Cross Bow mech.

[Agent Blak]

I am interested in how the manufactoring of this would be carried out. I am interested in on that would be for a 400-500lbs pull so it will have to be able to with stand some force. Will "Cold Rolled Mild" work? any help would be greatly appreciated. Also can a low power scope be mounted on to a cross bow? or is it just aimed by line of sight?


------------------
A wise man once said:
"...There Will Be No
Stand Off At High Noon
... Shoot'em In The Back
And, Shoot'em In The Dark"

Agent Blak-------OUT!!

Go <a href="http://briefcase.yahoo.com/bc/agent_blak">here</a> to download my files.

[SawedOff8gaugeman]

A scope can be attached IF there is a rail for it. It's up to the xbows manufacturer. I really suggest making some kind of sights, even simple iron sights. Maybe installing some adjustable surplus sights would do... Of course a multi-reticule scope is the best...

400-500 lbs? http://theforum.virtualave.net/ubb/smilies/tongue.gif Definitely not a toy.

[EventHorizon]

400-500#'s ?!?!

You would need some kind of good spring steel or spring system, steel cable and solid steel shaftd bolts. Then there is the factor of how you cock it, you would need some type of arming system for a 500# crossbow, unless you are one bad dude.

IIRC, most of the top end cross bows only top out at around 200-250#, I've shot a 125# one and they are wicked, 10" groups at 100yds!!!

------------------
"Chance favors a prepared mind" - Louis Pasteur
"Happiness is a large pile of links." - Me
PGP ID 0x147CEF54

[nbk2000]

Car leaf spring for the bow, and a winch to draw it back. Steel wire rope for the string, and small rebar for arrows. OUCH!

Rent the movie "The Good Son" with Macaulay Culkin (the "Home Alone" punk). He has a crossbow built like this that he uses to skewer dogs with.

BTW, they got the design from a 30's popular science article. Read some of them at a library if you can, all kinds of neat shit in those old magazines.

As an aside, if I was the burglars from Home Alone, I'd either leave the fucking place alone, or surround it with 20 gallons of napalm and burn the fucking place to the ground with the screaming brat in it. http://theforum.virtualave.net/ubb/smilies/smile.gif

------------------
"I have begun evil, I shall end evil. That is the end that awaits me."

Go here (http://briefcase.yahoo.com/nbk2ooo) to download the NBK2000 files and videos.

[Agent Blak]

The bow is made from the leaf spring off on an old truck I belive about 30" long x 1 1/2" wide x 7/16 thick. I am using a cocking mech. aswell so don't worry about that. I got the idea from PMJB vol 3, P.62. I am thinking about using the mech design from shown there.

------------------
A wise man once said:
"...There Will Be No
Stand Off At High Noon
... Shoot'em In The Back
And, Shoot'em In The Dark"

Agent Blak-------OUT!!

Go <a href="http://briefcase.yahoo.com/bc/agent_blak">here</a> to download my files.

[PYRO500]

what about one of those mini winch things they use for strapping things down, they can pull alot. and a 500 pound crossbow! if the bowstring ever broke you'd lose probably more than a digit. that would make a good sniper weapon, assuming you have a good projectile. I think I'd have trouble with a 250 pound crossbow and I consider myself a large guy, past a certain point it will cut into your hands no matter your strength, you'd have to wear thick welding gloves to not hurt your hands

------------------
visit my web page at:
[URL=http://www.geocities.com/pyro2000us/]

[Agent Blak]

I would assume that Aircraft cable or laminated steel cable would be most appropiate. I levered/ratched system seemed to be most practical.


------------------
A wise man once said:
"...Never, never--We don't exist,
We don't collect, We don't know,
No body knows anything and
If there is a bullet coming at
The head of the United States
Then we can tell you precisely what
time it is going to Arrive"
--Nicholas Rostow

Agent Blak-------OUT!!

[Mick]

did it occour to anyone that letting off a 500lb crossbow would rip your shoulder right off?

and, if you did have a 500lb crossbow, how do you plan on aiming it? it would wiegh a ton.

i made a crossbow with a leaf spring from a 2tonne truck, and mounted it on a piece of 50x40x4mm section steel, and used a low geared boat whinch to cock it and used a piece of 20mm re-bar for a test bolt

the first test, the boat whinch stripped it gears even before i could cock it

so i got a better an stronger whinch, and managed to wind it back an cock it.
as i was preparing to release the whinch clip(and i'll point out at this time, i wasn't holding onto the bow, i had it mounted on the ground) the 200kg steel cable which i used for the bow string snapped, and the bow flipped up in the air and came crashing to the ground.

after finding some 400kg cable, i tried again, and this time i managed to fire it
only it snapped the makeshift stock in half, and launched the half that whinch was attatched to into a wall, distroying the whinch on impact.
the bolt was found in 2 trees, it hit the first tree, and snapped in half, launching the other half into a tree next to it.
(and i assume there was a 3rd pice that broke off because the 2 halves in the trees never fitted together)

so yes, a 500lb would be cool, but as for sniper type applications, it would be pointless because you could not fire it accuratly, or without snapping your body in half.


[This message has been edited by Mick (edited October 19, 2001).]

[Predator]

On a 500lb bow you'd better be using some very sturdy bolts/projectiles unless you want the bolt/projectile to snap upon launching and take your arm with it

[SawedOff8gaugeman]

BTW, do normal, for instance 150lb xbows have a strong recoil? I'm interested because have never fired one http://theforum.virtualave.net/ubb/smilies/smile.gif Compare to rifle calibers?

[Agent Blak]

I am not stupid enough to fire an untested weapon from my sholder. To me is it common sense tomount it to test fire it. But the warnings are much appriciate.

------------------
A wise man once said: "...Never, never--We don't exist, We don't collect, We don't know,
No body knows anything and If there is a bullet coming at the head of the United States then we can tell you precisely what
time it is going to Arrive" --Nicholas Rostow

Agent Blak-------OUT!!

(Blak, you're signature is seriously getting out of hand, verging on kewl. Trim it down to 3 lines or less. NBK2000)

[This message has been edited by nbk2000 (edited October 19, 2001).]

[EventHorizon]

Crossbows don't have "recoil" in the sense of firearms. The energy is away from you, hence the crossbows would pull it self out of your hands rather then kick you down.

------------------
"Chance favors a prepared mind" - Louis Pasteur
"Happiness is a large pile of links." - Me
PGP ID 0x147CEF54

[BoB-]

Leafsprings come apart, I can bend the longest section on this leafspring I have using all my bodyweight, but when it was all together It felt like my spine was going to snap trying to get that thing to bend.

Imagine how far lightweight arrows would go in such a bow.

[Zach]

BoB-

F=M*A
Force = Mass x Acceleration.
So, you may be able to get that light weight "arrow" (actually a bolt) to go a long distance, but the force would be like getting shot with a cottonball from a slingshot. There is also the possibility of "overpowering" a light weight bolt, where the force applied causes the bolt to bend
when launched/in flight, throwing off the accuracy.

z

[twinkle]

I think it is interesting that you want to build such a heavy bow but I think that for normal use it will be to heavy , 250 lb is already a very high powered crossbow .Also you can do two things ,one is making to xbow like a medieval xbow with a very strong short
draw like your car leaf spring or with fibreglass/resin bow (prod ) which has a longer draw with less force but the result is the same .It is just as with a normal gun you have a bullet and the charge and with a xbow you have the bolt and the draw force /draw length , at a certain draw and draw length belongs a certain bolt length /weight .So you have a lot to experiments to do
I think that when you would like to built something so heavy you better could built a roman "catapult" like the Ballista or so although that is not something you take with you so easy. If you like I do have some
information on trigger systems of xbows which I could sent .Also be carefull with these experiments the forces you use are easely underestimate

[Mick]

i wasn't trying to call you stupid or anything agent black,
i merely suggesting to everyone, that if they were to try something along the lines of this it would be an idea to benchtest it first (its just that some people get 1+1=3...if you get what i mean)


crossbows don't have a lot of recoil, more so *snap* then anything.
When you fire them they make your arms fly forward, which you then counter by pulling back. there a good way to pull a few muscles.
i used to have a 300lb bow, and i found even after firing it god knows how many times i still sometimes pulled my neck/shoulder out from the snap when it fires

[BoB-]

I am aware of Newtons' laws, which is why I mentioned how far they would go. You dont have to use physics to build a crossbow bolt, pointy stick going fast = ouch!

[twinkle]

I don't agree that with you Bob a pointy stick as a bolt Iam busy now for about 8 month trying all kind of things with bolts and a self-made xbow and getting the right bolt for it is not so easy as you say okay all "sticks" fly but to get the best result is another story .

[Agent Blak]

I would greatly appreciate it if you coulfd send me those triger mechs. I didn't think that you were callin' me stupid... and I know what you mean. for instance some will try to make a Slam-bang Shot gunusing 3/4" and an end cap. Than they wonder why it destroyeditself on the first firing. after they anwser a few questions it comes about that they used CPVC or Cu pipe instead of Galvized.
Can you send the info on those mechs to:
agent_blak@yahoo.com


------------------
"I Always Have A Spade Or Two Handy"

Agent Blak-------OUT!!

[BoB-]

Twinkle,

If you bang a razor knife into the end of a peice of wooden dowel, forming an x shaped split, then you can fit quivers in and secure them by wrapping the dowel in sinew (for looks), or duct tape.

I'll upload pics to the ForumFTP if you dont understand.

These bolts fall apart (literally) after a few shots, a more sturdy one could be formed from aluminum rod.



------------------
Teamwork is essential.
It lets you blame someone else.

[EventHorizon]

Bob-

Are you refering to "feathers" or "fletches"?

Quiver is a term I associate with the device that holds the arrows.

Most any sporting good store sells fletches and fletching glue. Fletchtite comes to mind. They are essential to getting the bolt or arrow to fly straight. Some simple math and a peice of paper wrapped around the bolt should be sufficient to align them at 120°.

To give you an idea of what type bolt material you'll be looking at, a 60# pull compound bow can't use the cheap wooden arrows. You just might be looking at solid aluminum shafts if you have a beefy crossbow.

------------------
"Chance favors a prepared mind" - Louis Pasteur
"Happiness is a large pile of links." - Me
PGP ID 0x147CEF54

[bangandow]

a while back at a gun show, there was a blowgun booth. the guy had a kit that you just hooked on and you powered your blowgun with co2 powerlets(from the cheap walmart paintball guns). the bolts used were solid aluminum and (according to the vendor) could take enough oomph from the co2 to go straight through a deer without any adverse effects to the bolt itself. id say using wooden dowels is a definite no-no with a bow this powerful. solid metal bolts is the only thing i can see working...

[This message has been edited by bangandow (edited October 23, 2001).]

[twinkle]

It was not meant as an insult Bob and i know how to make bolts you even can make a bolt more simple using wide tape to make vanes (instead of fletching the bolt it is not as good as fletching but it can do the job ) ,
however if you make the bolt to light it will flutter and when the bolt is to heavy it will drop to fast when the fletches or vanes are to big they will result in a brake when they are to small they don't work properly.
It makes great difference what type of point (arrowhead) you put on a bolt the flight pattern of a bolt with a broadhead is different from a "bullet point " you can make a bolt of wood , aluminium or glassfibre and I think for such a heavy xbow as 500 lb even steel tubing could be used .I see that they are saying to use solid rod instead of tube but for the strength it does not make much difference if you use tube or solid the bending strength is the same only it could help if you want more weight for a bolt .
this was for the bolt but the same applies for the xbow itself what type of trigger mechanism you are going to use and how long the draw is . There are a lot of variables you can "play" with .

[BoB-]

Quiver is used in the south as a synonym for feathers, bad habit of mine.

[Mick]

agent black: i never got as far as designing a trigger mech for it, all i used in the test phase to fire it was a piece of string tied to the release on the whinch
and i never finished the bow due to lack of time

the trigger mech was something i could never figure out - one of the ideas i had was the trigger mech off a spear fishing gun(obviously modded so it could take the extra strain)

[twinkle]

agent black maybe this can help somewhat to , if you want drawings of trigger mechanism I can email them to you I did not have the url addresses anymore .
http://crossbow.hunter.ru/making/bowstring.html
http://www.atarn.org/chinese/cn_arc_indx.htm
http://jim-diana-hart.home.att.net/cbsite.html
http://www.geocities.com/colosseum/1486/string/
http://www.en.com/alchem/crossbow.html
http://crossbow.hunter.ru/making/lock.html
http://www.geocities.com/TheTropics/3433/crsindex.htm
http://198.144.2.125/Crossbows/crossbows.htm
http://www.atarn.org/chinese/yn_xbow/yn_xbow.htm
http://www.atarn.org/chinese/rept_xbow.htm

[twinkle]

this is the address of the National Crossbow men of America they have a nice gallery with a lot of pictures of target crossbows they also sell plans of the Bailey's crossbow
(which is nice , scale 1:1 )
http://www.usarchery.org/naapub/crossbow/xbow.htm

[Boob Raider]

15 days short of a year. Anyways I was working on a kind of a bow that can be carried like a handgun so it doesn't have the cross leaf spring. Instead I am using 2 posts, one on either side to which 2 sling shot "power bands" have been attached. Rest of the design is same as a conventional crossbow. For the arrows/bolts I am using chop sticks (the bamboo ones). The chopsticks can carry impact sensitive 10-15 g AP or HMTD heads or the good old pointy end.

[Fukineh]

A friend of mine made a ballista with a truck leaf spring, and yes, It destroyed itself as we all anticipated. If your going to make something that powerful that is hand held It will have to be extremely strong yet light enough to carry. Now, the question is can anyway afford to make a crossbow out of magnesium :D ? My main point is that making something handheld and that powerful is impracticable, but I would love to see it successfully done.

About the pistol "crossbow" that is relatively flat shaped, you should try making a magazine for it. Preferably one that is spring loaded instead of gravity loaded so that you can still aim accurately.

<small>[ December 08, 2002, 08:38 PM: Message edited by: Fukineh ]</small>

[Harry]

Check the USPTO database. I remember seeing such a device, with short quarrels.

Search keyword archery.

Harry

[McGuyver]

I love the idea of having a small crank mounted beneath the bow to aide in pulling it back. It's noisy and might take longer but it seems really handy.
It would also have to release quickly.
I think the leaf spring thing was tried on junkyard wars but they were trying to lauch a football and it sucked. The other guys were using a huge air cannon. :D

<small>[ December 12, 2002, 09:19 PM: Message edited by: McGuyver ]</small>

[Fukineh]

Ya I've seen that episode. Pneumatic cannons kick ass and are quite reliable, but If you could get a giant ballista to work consistently right that would be a shit load of fun also.

[Anthony]

You should have seen this serie's grand final - they had to build a device to throw a car. One team made a trebuchet from telegraph poles with a skip full of 4 tons of lead as a counter weight.

Oh man, you should have seen when they pulled the release pin :D

[nbk2000]

Does that mean it worked and the car went flying?

Or did it fly apart, impaling silly wankers with shards of wood and metal scrap?

[zaibatsu]

Wankers, do they actually say that in the US? Anyway, while looking through my local library I found a very interesting book pertaining to this topic. It's called "The Crossbow - medieval and modern military and sporting, its construction, history & management". Problem is it's HUGE (~400 pages) and is a reprint of a 1903 book. I can't obviously scan it all in, as I have neither the patience or time to do so, but I can scan some sections in if you'd like. Here's a brief contents:

Part 1 - The history of the crossbow, with notes comparative on the longbow shortbow and handgun
I - The military crossbow
II - The Sporting crossbow
III - The General dimensions of crossbows
IV - The bolts used with crossbows
V - The range of the medieval crossbow and how it compared to the longbow
VI - The shortbow and longbow in relation to the crossbow
VII - The Handgun in relation to the crossbow
VIII - Summary of the development of the mediaeval handgun
IX - A summary of the history of the crossbow

Part 2 - The construction and management of crossbows: Mediaeval
X - The primitive crossbow
XI - The 13th and 14th century crossbow
XII - How the bow of the primitive crossbow was attatched to the stock
XIII - How the crossbowman placed the bolt of his crossbow on the stock of his weapon
XIV - The various contrivances employed in the 13th and 14th century for bending the bows of crossbows
XV - Continued
XVI - Continued
XVII - Continued
XVIII - The 15th century military and sporting crossbow with a thick steel bow
XIX - The construction of a powerful crossbow such as those used for killing deer in the 15th century
XX - Construction continuted
XXI - Construction continued
XXII - Construction continued
XXIII - Construction continued
XXIV - Construction continued
XXV - Construction continued
XXVI - Construction continued
XXVII - Construction continued
XXVIII - Construction continued
XXIX - The Slurbow
XXX - The 16th century sporting crossbow
XXXI - The cranequin and how it was applied to bend the steel bow of a crossbow
XXXII - The 16th and early 17th century Spanish sporting crossbow
XXXIII - The 16th century stonebow
XXXIV - The 16th century stonebow with a thicker steel bow
XXXV - The 17th and 18th century sporting and target crossbow
XXXVI - The 16th century improved locks which were fitted to porting and target crossbows

Part 3 - The construction and management of crossbows
XXXVII - The bullet-shooting crossbow
XXXVIII - The bullet-shooting crossbow continued
XXXIX - The bullet-shooting crossbow continued
XL - The bullet-shooting crossbow continued
XLI - The large bolt-shooting continental target crossbow
XLII - The small bolt-shooting target crossbow as used currently in Belgium
XLIII - Belgian target crossbow continued
XLIV - Belgian target crossbow continued
XLV - Belgian target crossbow continued
XLVI - The bullet-shooting target crossbow with a barrel
XLVII - The popinjay
XLVIII - The crossbowmen of Dresden-Privilegirte Bogenschutzen Gesellschaft
XLIX - The chinese repeating crossbow
L - Arrow throwing

Part IV - A treatise on the siege engines used in ancient and mediaeval times for discharging great stones and arrows
LI - Introductory notes on the siege engines used in ancient and mediaeval times for discharging great stones and arrows
LII - The antiquity of ballistas and catapults
LIII - The effects of ancient siege engines in warfare
LIV - The distances to which ancient siege engines cast their projectiles
LV - The catapult, its construction and management
LVI - The catapult continued
LVII - The Ballista, its construction and management
LVIII - The trebuchet
LIX - The spring engine
As you can see, there's a lot of stuff! Bear in mind this was written around 100 years ago.

[Anthony]

No, I think NBK is the first :)

Well, the car flew a bit, just in the wrong direction, and as an indirect result of a "fault". The problem was that the RSJ they had used for the main arm, although it looked pretty substantial, wasn't strong enough. When the counter weight fell, the arm bent and thus didn't raise the car, which meant that the energy from the weight wasn't transfered to the load. So the counter weight just accumulated kinetic energy until it reached the end of it's travel, whereapon it dumped it all into the frame (think 4T falling from 30+ feet), which promptly disassembled itself - in a most spectacular fashion :) I ain't never seen telegraph poles snap like that before :D

Oh, I loved those Devonshire farmers :) "Propah Jawb!"

[nbk2000]

Hey, I'm trying to expand my vocabulary to be international . :D

That hundred year old book is guaranteed to be much more detailed than any modern book on the subject of construction of these ancient weapons.

"bullet throwing" crossbows? Hmmm...previously fired rifle bullet projected at high speed via crossbow...cops looking for silenced rifle.... :)

I'd say scan anything that gives DETAILS on the construction of these weapons. All the history and background is obtainable elsewhere.

If you do scan it, do a good job of it and don't bollock it up. <img border="0" title="" alt="[Wink]" src="wink.gif" />

<small>[ December 14, 2002, 10:26 AM: Message edited by: nbk2000 ]</small>

[Anthony]

"Bollock(s) it up" NBK :)

[smokey]

ok guys ive got to say that imho i think that a 500lb cross bow would be a bitch to both use and maintain i think you would end up with a ballista style weapon( good for seiges) build yourself a 175 lb weapon and use it to nail dogs to trees and telegraph poles .ive got a 60lb pistol crosbow and its great for nailing rats to the rafters of my mates shed! hahaha
i woul have to agree with twinkle in tha the use of tube for bolts is the way to go in fact im gonna try it out with my gear and i love the co2 powered blow gun thing would you classify it as a mini portair cannon?

<small>[ December 19, 2002, 03:41 AM: Message edited by: smokey ]</small>

[SmallR2002]

tip: dont brace it only for back-recoil, brace for frount as well - crossbows dont fly straight! And hurt alot

[dinkydexy]

IMHO any talk about 500lb draw crossbows is just silly. The impracticalities of building and handling such a weapon have been well covered and are all well-grounded observations. What would someone hope to gain by more than doubling the drawing power of a readily available crossbow...extra range perhaps? Well, what use is that without accuracy, which it would be virtually impossible to gain? Or maybe extra penetrating power or clout at normal ranges? If so, what's your intended target for goodness sake?

I'm a reasonably experienced crossbowman. Take it from me, the weapon you're thinking of building is a loser's weapon. I'll back myself with a humble 150lb crossbow and a handful of homemade wooden 14" quarrels against it any time...and curiously enough the advantages I'd have would be the same as those enjoyed by the English Longbowmen who readily proved their superiority over their Continental European crossbow handling opponents way back when; superior rate of fire and increased mobility.

You fancy handling a crossbow? Cool. If you have half the pleasure that I have with mine then you'll be delighted...but just go buy one!!

[mr. wiggles]

I have never used large scale crossbows, but I would assume that with 500lbs, you will be dealing with less of a crossbow and more of a "javelin launcher"*. I would recommend looking for books on medieval siege weapons a and they should have a fair amount of info on javlin throwing machines.

The picture I have seen in some midieval weapons book had the the launcher mounted on a large quad-pod. Many things may be differint from the midieval design, as you will be using metal and they made thiers largly out of wood.

*that isn't the historic name, I tryed to search for it but came up with nothing

[Arbalest]

There is nothing silly or inherently difficult about building a 500# crossbow. Such a weapon doesn't have to weigh a ton or be a "javelin launcher", it will not rip off anybody's arm and it will not need metal arrow shafting. The pull of a bow tells little more than the amount of force needed to pull the string back. Two men can both weigh 200# yet the strength or speed difference between them can be huge. The same fact applies to crossbows.

Medieval crossbows typically had a draw weight ranging from 300 to 1200 pounds, and they were made mostly from wood, horn and sinew, materials much weaker than modern spring steel / fiberglass etc. Some of the 500+ pound 'bows don't have any metal in them apart from the trigger, and they are compact weapons weighing under 10 lbs. The reason they hold up is that they have very short draw lengths, often only 6 - 8". Consequently they don't store any more energy than a modern, high-end, long-draw crossbow. Which means the strain on the parts isn't particularly huge.

Why would anyone want to make a 500# crossbow if you can have a 200# crossbow that's just as powerful? Well, it's a hell of a lot easier to make a simple, straight, spring steel bow with a short, really heavy pull than to build an equally effective crossbow of half or third that weight. It would take well-designed, laminated reflex /recurve limbs or a compound system. Not something that can be done from scrap metal with a grinder. Commercial, good quality crossbows cost from 400 to 800 dollars, a worthy motive in itself for building a home-made version.

With a 500# crossbow it might be wise to follow the example of medieval bowsmiths and use a simple, rolling nut trigger mechanism, where the trigger is a long lever that's pulled with the whole hand instead of only an index finger. It takes some oomph to release a sear holding back hundreds of pounds. Most of the heavier, modern crossbows are compound bows. A 200# compound puts only 100# or less onto the trigger mechanism thanks to the let-down. A 500# home-made 'bow puts five times more.

By far the best string for a home-made crossbow can be made from the modern bowstring fibers that are sold in rolls in archery shops. A single strand of FastFlight has a breaking strength of 55#, so a thirty-strand string will hold up for 1650 pounds! And FF is very light for it's strength, a prerequisite for an efficient bowstring. Ordinary Dacron is a cheaper, weaker option.

Wood is still a very functional arrow material, and when used properly, will endure the forces generated by the heaviest crossbows. Crossbow bolts are short, so their stiffness is very high compared to conventional arrows. A wooden shaft doesn't have to thicken much to strengthen manyfold. The wood for serious heavy-crossbow ammo must be strong, not the weak cedar and pine that commercial wood arrows are made of. Hickory is the best in this regard, ash, maple or oak are good, readily available alternatives. The grain of the shafts must be absolutely straight; a shaft with stepped or wavy grain will crack dangerously when shot from any bow. The heaviest crossbow I've built - 180# - shoots 3/8" X 18" hickory bolts beautifully. A half-inch + diameter shaft might be a better choice for a 500-pounder.

[Dave the Rave]

Yes, Arbalest is rigth. I am an archer too, and have an xbow with 500 lbs, but it´s comercialy made, and it is not huge or heavy. It´s design can be duplicate by anyone with some skils on wood, and an smal workshop at hand, I think, in about 10 hours on nice work.

It isn´t made of strange materials, only of wood and fiberglass. It´s cordage is made of dacrom, (40 strings) and it´s bolts are made of AL tubing and epoxi with exactly half inch diameter.

When it shoots, there is no higher recoill than an convensional 200 lbs crossbow, and it´s bolts are driven easily throug an 3 inch plywood.

About those triggers:

Trigger one (http://photos.groups.yahoo.com/group/crossbow/vwp?.dir=/crossbow-stonebows&.src=gr&.dnm=Image2.gif&.view=t&.done=http%3a//photos.groups.yahoo.com/group/crossbow/lst%3f%26.dir=/crossbow-stonebows%26.src=gr%26.view=t)

Trigger two (http://photos.groups.yahoo.com/group/crossbow/vwp?.dir=/crossbow-stonebows&.src=gr&.dnm=Image1.gif&.view=t&.done=http%3a//photos.groups.yahoo.com/group/crossbow/lst%3f%26.dir=/crossbow-stonebows%26.src=gr%26.view=t)

Simple trigger (http://photos.groups.yahoo.com/group/crossbow/vwp?.dir=/crossbow-stonebows&.src=gr&.dnm=trigger.jpg&.view=t&.done=http%3a//photos.groups.yahoo.com/group/crossbow/lst%3f%26.dir=/crossbow-stonebows%26.src=gr%26.view=t)

Those 3 images are from an crosbow forum on Yahoo, nice images and files to anyone who wishes to browse the entire archive.

- Later I´ve realised that those links are useless to anyone who does not have an yahoo account. Sorry guys I´ll keep the llinks to those who wishes browse through the forum, but I will post only the pics ( as soon as I get it working ) -

[lamar pye]

I've seen a crossbow made from a leaf spring that used bolts made from farm haying rake teeth. It was very powerful and the accuracy was not bad but it seemed like a giant leap backwards in my opinion. A sound suppressed bolt action in .45 would be much more fun and you wouldn't have to hunt for the bolts after they dissapear.

[Dave the Rave]

Ok, Surely shoot some rounds on an nice (and supressed) .45 is one of mine ideas of fun, and most sure that we don´t have to search the grass to find lost bolts after that, but on the other hand, an trustfull crossbow have some advantages:

1- Less recoill - A .45 haves an kick that is an annoing thing
2- No signature - Crosbows don´t ligth in the dark
3- Better range - A supressed .45 haves a low range of "kill"
4- More penetration, even on bulletprof vests - A bolt with hunting tip or even with plain steel tip can penetrate easily on most BP vests

Plus it is a weapon to snipe the prey, it´s shorter than an rifle, ligther, simplier and much more terrorizing. Imagine the fear of the enemy when they see one body with a bolt protuting of a bloodly wound. It´s like found someone killed with a knife, we can manage the fear of being shoot with a bullet, but the pain of the tissue cut or pierced by an serrated hunting tip, made of cold steel and almost impossible to remove by "normal" ways, and which cuts and tears the tissues, nerves and tendons at every little attempt to movement, it´s beyond human tolerance.

Anyway, here are the triggers that I mencioned before.

- Dear Mods, why my pics don´t appears ? Is the add attachment option working ? -

[Rhadon]

Attachments have to get approved before they show up. This can take between minutes and one day (or even a few days on exceptional cases), depending on how often we come to have a look at the submitted attached files.

[McCarthyite]

I think Dover reprints that book under the title - "The Book of the Crossbow" by Ralph Payne-Gallwey.

[Jacks Complete]

You can see bits of "The Crossbow" <a href="http://www.rubbertreeplant.co.uk/catapult/crossbow.php">here</a>.

A "Javlin thrower" is called a ballista, by the way.

The Chinese repeating crossbow is quite interesting!

[zaibatsu]

I am now in possession of that book, it's very good, but also very large. Problem is, no scanner. Anyone (respected UK member) that wants to have a huge task on their hands can have it mailed to them, but only serious people - it's a serious task.

[Jacks Complete]

I would and could do it, but like you say, it is a huge job.

Do you have an older version or a newer version? OCR software tends to get stuck on a lot of the olde english and the odd turns of phrase.

I borrowed a copy printed in the 1950's, but couldn't scan it as the owner wouldn't let me break the spine, let alone cut it up! I tried the trick of taking and scanning photos, but it just didn't work.

[zaibatsu]

I'm not sure what you mean by old/new version, it's a straight reprint, so the language/phrases are the same as the original. It's significantly newer that the 1950s, like mid 1990s. If I sent it out, I really would prefer it not be damaged.

[dinkydexy]

"The pull of a bow tells little more than the amount of force needed to pull the string back. "

lol.

I think you'll find that there's a direct corellation between this force and the amount of force stored as potential energy when the the string is cocked, and then subsequently released and imparted to the bolt...which is to say they are all exactly the same. Bigger draw weights mean more energy stored and transferred to the bolt, usually exhibited as a faster initail velocity and thus greater range and/or clout.

[Jacks Complete]

dinkydex,

There are limits to how fast that energy gets fired out though. Hence the need for changing the material the arms are made of, and the mass of the arrow. A light arrow will not get as much energy from the bow as one that is just right, and one that is too heavy will have a limited range.

Research by the Royal Armouries in Leeds shows that, over the course of centuries, the range of crossbows only increased slightly, despite massive advances in the materials and techniques used to make them. The power went up, and bolts got heavier and heavier, and the total energy increased, but the "muzzle velocity" of the crossbows stayed the same! The energy went up a long way, but there was a limit to how fast the bow would throw the bolt. Even the big seige crossbows, which fired inch-thick bolts and cut through armour, still only threw the bolt at the same kind of speed. This is why armour persisted.

The big advance on the speed was actually down to gunpowder. Suddenly, there was a weapon that, whilst not very accurate (yet loud and good at intimidation), could throw a ball at ten times the speed of a bow. This meant that armour had to adapt.

Modern crossbows with glassfibre prongs are still beset by the same issues, hence the "Velocipeed" types bows that use leverage and pulleys to make them easier to cock and pull the bowstring faster.

Another issue is that the power stored in the bow has to go somewhere, and if it cannot, the bow, made well or not, may break. I have been close to a top-of-the-range new crossbow which some pillock fired without a bolt (in the fucking shop!) which snapped the string and destroyed itself. That energy has to go into the bolt, and too light a bolt means much energy is wasted.

So, no, the energy in the bow has little to do with the speed of the bolt.

Edit: Ziabatzu, I suspect I wouldn't have the time then. I think that scanning a 400 page book without being able to use a sheetfeeder would takes weeks! Heck, even *with* a sheet feeder... To do it without cutting out the pages would take forever!

[Arbalest]

[i]
I think you'll find that there's a direct corellation between this force and the amount of force stored as potential energy when the the string is cocked, and then subsequently released and imparted to the bolt...which is to say they are all exactly the same. Bigger draw weights mean more energy stored and transferred to the bolt, usually exhibited as a faster initail velocity and thus greater range and/or clout. [/B]

lol.

The pull of a bow is only a small part of the equation determining the energy stored in a bow. Draw length (the distance the string travels), has a huge effect, as well as the shape and length of the limbs, the initial tension in the bow before the draw, the mass of the limbs, mass placement etc. etc. Simply changing the string of a bow can increase or decrease the speed of an arrow dozens of FPS.

I suggest you check the basic literature ( "Archery - the technical side" by Hickman, Klopsteg and Nagler, or the more easily accessible "Bow design and performance" by Tim Baker in "the Traditional Bowyer's Bible vol. I").

Or better yet, make some practical experiments. Take an inch thick, three foot long oak board, attach a string to it and start hanging progressively heavier weights from the string. You'll need hundreds of pounds' pull to bend the "bow" two inches. Next, shave the board down to 3 / 8" thickness. The "bow" will now have a measly pull of maybe 100 pounds at twelve inches or so. It will, however, shoot a 500 grain bolt many times farther, with much more velocity and KE than it's awesome multi-hundred pound predecessor.

Modern crossbows with a 150 - 200 lbs. pull shoot no faster than compound bows with a 70 - 80 lbs. pull ( the world's fastest commercial compound shoots 350 FPS at 70 lbs. The world's most powerful commercial crossbows manage about 330 FPS with two- three times the weight and only slightly heavier bolts). If you compare bows with different limb configurations, the difference is even greater. Medieval crossbows, with their short draw lengths, heavy limbs and strings, and the friction between the bolt and the stock and the string and the stock, need 1200 lbs. to equal the cast of a 50 lbs. flight bow.

There is no direct correlation between the pull and the energy storage, let alone bolt velocity. The correlation only exists between bows that are excactly identical apart form the pull.

[dinkydexy]

"A light arrow will not get as much energy from the bow as one that is just right"

Hello? I'm sorry, but this is just plain wrong. Perhaps what you are trying to say is that a light arrow will not be able to overcome air resistance as well as a heavier arrow would, in exactly the same way as a ping pong ball will not cut through the air as well as a golf ball. Both receive the same amount of energy, but the lighter object has less inertia and is thus more readily slowed down.

"So, no, the energy in the bow has little to do with the speed of the bolt."

Sorry again, but if all other factors remain constant then greater energy will result in greater speed.

"The pull of a bow is only a small part of the equation determining the energy stored in a bow. Draw length (the distance the string travels), has a huge effect, as well as the shape and length of the limbs, the initial tension in the bow before the draw, the mass of the limbs, mass placement etc. etc. "

Sorry for the third time, but the enegy stored in a bow, when it is cocked, is determined by its draw weight. All the other factors you list, amongst others, affect the rate at which that energy is transferred to the arrow when the weapon is fired. Two totally separate issues.

"There is no direct correlation between the pull and the energy storage, let alone bolt velocity. The correlation only exists between bows that are excactly identical apart form the pull.

Well this is just nonsensical. Whether you can get your head around the concept or not, the energy stored in a cocked bow is determined by its draw weight and vice versa, whereas bolt velocity is determined by a number of other factors. As for your acknowledgment that there is a correlation only in bows '...that are exactly identical', well excuse me but it should go without saying that if you start altering other things then OBVIOUSLY you will alter the whole equation!! How much sense would it make for respond to the statement 'a dog is a 4 legged animal' with words to the effect of 'actually it has 5 if you include the tail'???

If what you're saying is correct, then kindly explain why it is that every bow available for purchase anywhere in the world has its draw weight listed as its primary specification...indeed, as often as not, its ONLY specification.


ps.I think my point is proved; any talk about building a 500lb+ bow is silly...just go out and buy one.

[Arbalest]

Dinky Dexy: I am lousy at expressing my thoughts about physics here, since A) English is a foreign language to me, and B) I have no physics education of any kind. I have, however, built, shot and tested appr. 50 bows of various types, including longbows, sinew-backed bows, recurves and crossbows, in the past 12 years. Additionally, I have owned and tested with a chronograph and a tape measure two commercial compound bows and three commercial crossbows.

I am the reigning flight shooting champion at our local Bowyer's Guild. I have changed ideas about how bows and arrows work with the most highly acclaimed modern bow experts, including men like Tim Baker and Dan Perry. I honestly think I know what I'm talking about when it comes to bows.

Do you know what a force-draw curve is? It is a line drawn on a graph, with draw length indicated on the horizontal plane and draw weight on the vertical, based on the pull of a bow at various draw lengths. Simply put, the area under the line is the energy stored by the bow. Not only draw weight and length, but also many other factors I mentioned affect the size of this area. This is thoroughly tested and proved common knowledge you can read from any serious book on bows and arrows. I hope some Forum member with a physics background expresses this idea to you using the correct scientific jargon.

The force-draw curve is the single most important indicator of arrow V and E. Why does a 50 lbs. compound bow shoot a 500 grain arrow about 30 FPS faster than a 50 lbs. longbow? Why does crossbows have to be two or three times heavier than hand held bows to achieve the same V and E? The FD curve is the answer to these questions. At identical draw weight and length, a compound stores much more energy than a straight limbed bow, as shown by it's highly curved FD curve compared to the longbow's almost straight FD curve. A crossbow, with it's short draw, puts much less area under it's FD curve than long - draw hand held bows at similar poundage.

The energy stored in a bow is only partly the result of draw weight. Since there are many, many factors affecting how much of the bow's potential energy is transferred to the arrow, in the end draw weight often really tells nothing about a bow's performance.

None of the hundreds of bow ads I've seen over the years have the draw weight listed as the primary specification. Yeah sure, some of those really sketchy SE Asian Barnett copy ads...
Every quality bow model is produced in various draw weights, which are typically shown in small print at the bottom of an ad. "Bow speed" is very often used as a primary attraction. Maybe the fact that you use advertisements as your source for dependable proof tells something of your depth of knowledge in this field?

Flight shooting is an excellent way to test various theories about bow and arrow design. I could bore you with dozens of instances where a light bow has out shot a very similar heavy bow. With different types of bows, even similar weight bows have strikingly different cast. Long-draw bows typically shoot arrows much farther than same-weight short-draw bows (to a point). The amount of evidence contradicting your claims is so massive it's hard to know where to begin.

Tests have shown (see the literature in my earlier post) that a heavy arrow is more efficient, ie. uses a larger percentage of a bow's potential energy, than a light arrow, but the effect is only slight. The heavy arrow's better KE and ballistic coefficient is the main reason why appropriately heavy arrows fly farther than lighter arrows. Medieval crossbows, with all the energy-transfer problems I posted earlier, don't shoot light arrows faster than any simple hand held bow, but can spit out incredibly heavy bolts with just as much speed.

[kEFIR]

I have recently been given the book "the croosbow" by R. Payne-Galloway and are planning to scan the part about the construction of a typical crossbow. Will be done sometime during the weekend.

[dinkydexy]

"I am lousy at expressing my thoughts about physics here, since A) English is a foreign language to me, and B) I have no physics education of any kind."

You're either out of your depth or you're both misunderstanding other people's posts and not expressing yourself properly.; in either case it's ridiculous for you to continue repeating the same point again and again, when it is simply WRONG. You can try to impress the world with boasts about your knowledge, achievements, etc till the cows come home...you can make silly patronising remarks to others who you've taken a dislike to till you're blue in the face...you can point to as much pseudo-scientific and technical data as you wish...but the fact remains that what you are saying about the storage of energy is just plain incorrect.

Get your head around this, if you can; energy storage and energy release are two completely seperate matters. A sack of coal contains a certain amount of energy which can be released in countless different ways, such as simply burning it or grinding it to a powder to create a flash...but it is folly to think that once it has been ground it suddenly has acquired more energy because it will burn much more rapidly!! A set of springs of different lengths, thicknesses and made from different materials but all possessing the same elastic limit will all store the same amount of potential energy when stretched...but, again, it would be folly to think that the springs with a fast contraction property had somehow acquired more energy than the others when expanded!! A tank of water posseses potential energy which could be released by making a hole in it...and the rate of release of this energy could be increased by enlarging the hole...but this would not mean that enlarging the hole had given the tank of water more energy!! You could fill two cars with an equal amount of fuel, thus giving them both the same amount of energy...but different models of car will release that energy differently; if you seriously believe that when you put 10 litres of petrol in a Ferrari Testarossa you are giving it more enegy than if you were to put it in a Ford Fiesta then quite frankly I despair!!!

And the amount of energy stored in a cocked bow, which is merely a spring, is not affected one iota by such factors as the material from which the bow is made, the size, shape, drag coefficeient or mass of the arrow, whether the bow be compound, long, recurve or whatever!! All of these are factors that affect the rate of release of the stored energy and subsequent flight of the arrow...NOT the amount of energy actually stored.

ps. The area under the curve on a force-draw graph does NOT display the amount of energy stored in a bow.

[Narkar]

Dinkydexy, go buy a "Traditional Bowyer's Bible" vol.1 , read it through 3 times and then come back. Because at the moment you know very little about general physics, and about nothing about designing bows.

Your comment about the ping-pong ball and the golf ball is ridicilous. They both have about the same air resistance (golf ball a bit less because of the dips on its surface though). What is different is energy in them when you throw them from the same crossbow. Fact is that crossbow limbs dont return home fast enough to give ping-pong ball even a small amount of the energy they have. But since golf ball is much heavyer, at the same speed or even smaller velocity (because of its weight) it gets much more energy out of the crossbow. The limbs come home a bit slower but the golf ball can take much more energy in it at the same velocity as ping-pong ball.

Air resistance has almost nothing to do with it because it is connected to the surface area, which is almost identical.

Now try to get this into your head: Draw lenght makes a huge difference in how much energy can be stored in a bow. This is just basic school physics. How to calculate how much energy you give to a rubber band when you strech it? It's only about the lenght and the weight of the pull. NOT ONLY WEIGHT. What you are basically saying is that in a 500# at 2" bow is the same amount of energy as in a 500# bow at 20" THIS IS NOT TRUE, come on think about it a bit.
The reason why in the catalogs the bow's pull is the most important factor is that bows are mostly custom built. Every person has his own drawlenght. This varies usually from 24" to 32" You tell them the pull at what drawlenght and they build the bow for you. IF it isnt custom built then its usually the kind of bow that can tolerate being drawn into lenghts of 32", but the draw-weight is taken from the drawlenght of 28" (default)

Area under the force-draw graph curve directly displays the energy put into the bow. In case of a pulled rubber band the formulae is F(power of deformation) = -k(stiffness) * delta l(change of lenght). With the bow the energy storage basics is similar. Power of deformation there translates into the energy put into the bow. k(as stiffness) directly translates into the stiffness of the bow and delta l(change of lenght) directly translates into the change of distance from bow to the string (draw lenght minus bracing height)

[dinkydexy]

I can't believe this...I really, really can't believe this. Am I the victim of some kind of wind-up here?

1. You say that the point I made about the ping pong ball/golf ball is ridiculous, then you state that they both have about the same air resistance; SAME AIR RESISTANCE-THAT'S THE POINT!!!! But the reason a golf ball will overcome that air resistance...which you have acknowledged will be the same on both balls...more much easily, and thus travel further through the air is because it has more mass and therefore more inertia...and therefore will not be affected so much by external forces. Such as air resistance!!! Not because it has received more energy!!!!!!! And the stuff you've said about crossbow limbs being too slow to impart all their energy to a ping pong ball etc etc can only be described as gobbledegook.

2. You have completely, totally failed to understand what I have said, and am saying, about draw length. I have never, ever, said that drawing a string back just 2" will provide it with the same amount of potential energy as if it were drawn back further...and of course I would never, ever say that because it is just wrong!!!! You tell me to 'come on, think about it a bit'...well I challenge you to point to a single thing I've said in any of my posts that would support your silly claim that I believe that draw length does not affect energy storage. Go ahead.

3. You're partly right when you say that the reason manufacturers provide draw weight as the primary (and as often as not ONLY) specification so that a prospective purchaser will know if he's capable of handling the weapon; but the main reason is because draw weight is the most important factor regarding the amount of energy a bow can STORE. By the way, i note that you disagree with Arbalast who reckons "...None of the hundreds of bow ads I've seen over the years have the draw weight listed as the primary specification. " Hmmm!

4. "...at the moment you know very little about general physics, and about nothing about designing bows."

Like I told the other guy, making silly patronising remarks to others will not put you in the right here.

[Narkar]

But the reason a golf ball will overcome that air resistance...which you have acknowledged will be the same on both balls...more much easily, and thus travel further through the air is because it has more mass and therefore more inertia...and therefore will not be affected so much by external forces. Such as air resistance!!! Not because it has received more energy!!!!!!!

And what exaclty do you think interia is other than the kinetic energy pushing it forward? Same thing! If you shoot the golf ball out of the same bow lets say 50 m/s it will get more energy out of the bow than a ping-pong ball shot out of the same bow which moves much faster because of its lighter mass. That because the air resistance doesn't grow in linear shape but sq. That is why there is certain limit to how fast can the limbs return home on a bow, because of that the golf ball can take more energy out of the bow(thus its more energy efficent when shot out) even when it moves 50 m/s. SO IT DOES RECEIVE MORE ENERGY FROM THE BOW THAN A PING-PONG BALL!!!

And the stuff you've said about crossbow limbs being too slow to impart all their energy to a ping pong ball etc etc can only be described as gobbledegook.

what the...???


2. You have completely, totally failed to understand what I have said, and am saying, about draw length. I have never, ever, said that drawing a string back just 2" will provide it with the same amount of potential energy as if it were drawn back further...and of course I would never, ever say that because it is just wrong!!!! You tell me to 'come on, think about it a bit'...well I challenge you to point to a single thing I've said in any of my posts that would support your silly claim that I believe that draw length does not affect energy storage. Go ahead

Dont try to tell me it wasn't you who claimed that the area under the force-draw curve doesn't show how much energy is stored in the bow
Force-draw curve is the drawweight/drawlenght graph that shows how does the drawweight change in relation to the drawlenght.
Or maybe are you trying to imply that there is a third variable too beside weight and lenght of the pull that determines the energy stored in the bow?

3. You're partly right when you say that the reason manufacturers provide draw weight as the primary (and as often as not ONLY) specification so that a prospective purchaser will know if he's capable of handling the weapon; but the main reason is because draw weight is the most important factor regarding the amount of energy a bow can STORE. By the way, i note that you disagree with Arbalast who reckons "...None of the hundreds of bow ads I've seen over the years have the draw weight listed as the primary specification. " Hmmm!

No i dont disagree with him. Traditional and primitive bows are mostly custom made (primitive almost always custom made). I believe he knows much about designing bows, even you could learn it if you had read the bowyers bible vol 1

And ofcourse the draw-weight is the most important thing to look when you are buying the bow but you cant buy it based on ONLY the draw-weight. Besides i thought this discussion was about design of the bow and the energy it stores, not how to buy one.


4. "...at the moment you know very little about general physics, and about nothing about designing bows."

Like I told the other guy, making silly patronising remarks to others will not put you in the right here.

No that's not patronising remark, we are all here to learn and you should learn too, im just stating what i think about your current level on bow design.
I thought about it that if you currently think that force-draw graph doesn't display the energy stored in the bow and you think that a ping-pong ball would recieve the same amount of energy from the bow as a golf ball then you obviously don't know as much about bow design and it's energy storage. This is the place to learn :p

[Dave the Rave]

Narkar,

The point isn´t the air resistance, it´s the bolt´s capacity of store energy. If you shoot an .22 pellet with a 12ga cartridge it will go less far as an solid 12ga slug shot from the same cartridge. It happens because of the size and density of the ammo which stores more energy. The ammount of this energy is the same, the velocity of acceleration is the same, but the way of this energy is stored and discharged is that counts.

About the bows, the velocity of return of the limbs only afects the acceleration ratio of the bolt, not the energy stored in it, again, when you give an ammount of energy to an object like an rocket or to an cannon, the inicial velocity of it isn´t the same, but the energy is.

The draw / weigth show ecxactly the ammount of energy used to stretch the limbs at one given weigth throug one given distance, so, it shows the energy stored on the bow. When you have a bow with 200lbs, it needs the wegth of 200lbs to be cocked and gives the bolt teh energy of 200lbs. At composite or recurved bows, the draw/weigth remains the same, what changes is the way the energy is distributed to cock the limbs.

When it´s said that at identical draw weight and length, a compound stores much more energy than a straight limbed bow, as shown by it's highly curved FD curve compared to the longbow's almost straight FD curve it´s because the energy is distributed throug the several parts of the bow, and if you make one single and straight bow, down to the pieces of one compound bow, you will get one longbow bigger and heavier to achieve teh same draw/weigth

So, Arbalest and JC are completely rigth at all theirs statements, and you may learn something from them.

By the way, the fact that some of you read a book several times or make several bows don´t give the rigth to flame the others. Please, when quoting a book, write the formulae and equations to give us some solid points.

We don´t need someone who shows us how ignorants we are, but rather than that, we need someone to show us how much we can learn.

[dinkydexy]

This thread has degenerated into a pointless quarrel...there's a pun in there if you look for it...and I, for one intend to take no further part in it. I don't doubt for a second that some people will take that as some kind of surrender or backtracking or admission that I've been proved wrong etc etc etc, and that's fine by me- the facts will remain as I've stated them regardless of what any amount of ignorant people say or think.

Here's my final remark.

1. "...what exaclty do you think interia is other than the kinetic energy pushing it forward? Same thing!

This is incorrect. The inertia that a body possesses is affected hugely by its mass; it is not determined solely by its kinetic energy. Go study.

2. " If you shoot the golf ball out of the same bow lets say 50 m/s it will get more energy out of the bow than a ping-pong ball shot out of the same bow which moves much faster because of its lighter mass. "

"SO IT DOES RECEIVE MORE ENERGY FROM THE BOW THAN A PING-PONG BALL!!!"

This is incorrect. According to you, if you were to take a golf ball and a ping pong ball, place them in a vacuum, and then project them forward from an identical device the golf ball would travel either faster or further (or both) than the ping pong ball....because it was capable of receiving more energy. If you seriously believe this, then you seriously need to study. The fact is that they would travel in an identical manner. The only reason this does not happen in air is because of the resistance of that air; and in this instance the golf ball, being much more massive and therefore having much more inertia, will not be affected to the same degree and will thus travel further.

3. "Dont try to tell me it wasn't you who claimed that the area under the force-draw curve doesn't show how much energy is stored in the bow."

The statement that I made is correct, and for you to cite it as an example of something that I've said which would support your silly assertion that I think that draw length does not affect stored energy is just totally bizarre.

PS. This is not the first time in history that an Englishman has been mocked for his 'ignorance' on the subject of archery. But as the history books show only too well, he who laughs last laughs loudest!

[Narkar]

If you shoot an .22 pellet with a 12ga cartridge it will go less far as an solid 12ga slug shot from the same cartridge. It happens because of the size and density of the ammo which stores more energy. The ammount of this energy is the same, the velocity of acceleration is the same, but the way of this energy is stored and discharged is that counts.
Hmm, weird, i always thought that an object's kinetic energy is only about the weight and the speed of the object. Please explain me how the .22 pellet and a 12ga slug, moving at the same speed can have the same energy? :confused:

About the bows, the velocity of return of the limbs only afects the acceleration ratio of the bolt, not the energy stored in it, again, when you give an ammount of energy to an object like an rocket or to an cannon, the inicial velocity of it isn´t the same, but the energy is.

From your talk i get the impression that the kinetic energy isnt the velocity times the weight, please explain.

The draw / weigth show ecxactly the ammount of energy used to stretch the limbs at one given weigth throug one given distance, so, it shows the energy stored on the bow. When you have a bow with 200lbs, it needs the wegth of 200lbs to be cocked and gives the bolt teh energy of 200lbs. At composite or recurved bows, the draw/weigth remains the same, what changes is the way the energy is distributed to cock the limbs.

When it´s said that at identical draw weight and length, a compound stores much more energy than a straight limbed bow, as shown by it's highly curved FD curve compared to the longbow's almost straight FD curve it´s because the energy is distributed throug the several parts of the bow, and if you make one single and straight bow, down to the pieces of one compound bow, you will get one longbow bigger and heavier to achieve teh same draw/weigth

I know that, it wasn't me who said that FD curve doesn't show the energy!

So, Arbalest and JC are completely rigth at all theirs statements, and you may learn something from them.

Read again who said what because i have never disagreed with Arbalest or JC :mad:

By the way, the fact that some of you read a book several times or make several bows don´t give the rigth to flame the others. Please, when quoting a book, write the formulae and equations to give us some solid points.

We don´t need someone who shows us how ignorants we are, but rather than that, we need someone to show us how much we can learn.

I was just explaining to dinkydexy that i wasn't making patronising remarks! What do you want me to repeat that again? I WASN'T MAKING PATRONISING REMARKS, to you too then, happy now? :mad:

Also i wasn't quoting the book, i was reffering to it, because it is a good book, person can learn much more from bow design and performance from there

EDIT:


1. "...what exaclty do you think interia is other than the kinetic energy pushing it forward? Same thing!

This is incorrect. The inertia that a body possesses is affected hugely by its mass; it is not determined solely by its kinetic energy. Go study.
and you're saying that the interia is affected by the mass, but kinetic energy isn't?


"SO IT DOES RECEIVE MORE ENERGY FROM THE BOW THAN A PING-PONG BALL!!!"

This is incorrect. According to you, if you were to take a golf ball and a ping pong ball, place them in a vacuum, and then project them forward from an identical device the golf ball would travel either faster or further (or both) than the ping pong ball....because it was capable of receiving more energy. If you seriously believe this, then you seriously need to study. The fact is that they would travel in an identical manner. The only reason this does not happen in air is because of the resistance of that air; and in this instance the golf ball, being much more massive and therefore having much more inertia, will not be affected to the same degree and will thus travel further.
I never mentioned the vaccuum, ofcourse the two balls behave the same in vaccuum when shot out of the bow. That because the limbs dont have any air-resistance in vaccuum, that would slow them down (air resistance isn't linear, its in sq, so it slows the limbs considerably when approaching higher speeds)

Fact is that in the air the bow can't impart the same energy to the ping-pong ball as it can to the golf ball. That's because there is a certain limit on how fast the limbs move home. No bow can move fast enought to give all the energy to the lighter arrow that it would give to heavyer arrow. That energy stays in the bow, it is felt as the recoil and vibration.

Ok, lets try a different approach to the same thing:
If a lighter arrow is shot with more recoil and vibration (which indicates that there was still energy remaining in the bow after the arrow flew, right?) than with the heavyer arrow(and if you ever shot a bow you would know that) , then where else does that energy of recoil come from than the energy of the bow that wasn't given to the light arrow as completely as it is given to the heavy arrow. (this might not make much sense if you just read it but think about it)

In a conclusion: The vibration and recoil is that same energy that you stored in the bow, but because lighter arrows cant absorb it as well from a bow as heavyer arrows can, it is left in the bow, and you feel it as the recoil. Thus the heavyer arrows are more energy-efficent.
Prove that thought wrong, i challenge you.


3. "Dont try to tell me it wasn't you who claimed that the area under the force-draw curve doesn't show how much energy is stored in the bow."

The statement that I made is correct, and for you to cite it as an example of something that I've said which would support your silly assertion that I think that draw length does not affect stored energy is just totally bizarre.
Don't try to evade my question or change the subject. Force-draw curve is determined by drawweight and -lenght, which you say doesn't represent the energy stored, BUT, now you say that drawweight and -lenght does affect the energy stored. So why do you think that drawweight and -lenght put in a graph doesnt show the energy stored anymore?

PS. This is not the first time in history that an Englishman has been mocked for his 'ignorance' on the subject of archery. But as the history books show only too well, he who laughs last laughs loudest!
Just because you are from England doesn't mean you know more about bows than others.

[Dave the Rave]

Narkar, I must apologize myself to you, my topic wasn´t only to you, but I´ve write your name on it because the 1st reply are to your last post.

lets go, when I said that the acceleration was the same I was telling that the inertial energy imparted to those two shots was the same, not that the velocity was the same. My point was exactly that those two shots can´t have the same energy stored, although the initial energy was the same, just because : object's kinetic energy is only about the weight and the speed of the object.

The initial velocity of a rocket isn´t the same as the initial velocity of an cannon round, even if the propelent charge was the same. So, the initial velocity of an arrow insn´t the same as the initial velocity of an bolt, even if the bow or crossbow have the same draw/weigth.

From now on, The post was not about yours assertives, so, again I hope you apologize myself... I know and understand that you agreed about the FD, and that you know that JC´s and Arbalest´s points are rigth and I find rigth that you wasn´t making patronising remarks to anyone.

By the way, I may be too rude when ask you to quote the book, but I feel the urge to know, at writers words, how he find those informations. sorry again.

From now on, white flag to all of you and let get our focus back to the purpose of the topic, an trigger capable to handling an draw of 500lbs or bigger.

[Narkar]

By the way, I may be too rude when ask you to quote the book, but I feel the urge to know, at writers words, how he find those informations. sorry again.

Dont worry about it:
Bow's design and performance, by Tim Baker
"Left: To measure a bow's stored energy draw the bow using a spring scale, noting its draw weight at various lengths of draw. A typical 50 lb. longbow will weigh: 10" = 8 lb; 15" = 20 lb; 20" = 30 lb; 25" = 41 lb; 28" = 50 lb. Label the bottom and side of the graph as shown. Make a dot where
the 8 lb line and the 10" line cross. Make a dot where the 20 lb line and the 15" line cross, and so on. When finished, connect the dots. The resulting line is called the force-draw curve. Area under the line represents energy stored.
f. Right: F-d curves for a 30 pound and a 60 pound bow. Squares under a curve represent energy stored.

Draw Weight
Everything else being equal, higher draw weight stores more energy.
These force-draw curves show the energy stored in typical bows made from straight staves. One having a draw weight of 30 lb at 28", the other 60 lb at 28".
The number of squares below a curve represents total energy stored.
This stored energy is the ONLY means available for propelling the arrow."

"Draw Length
Everything else being equal, longer draw lengths store more energy.
A 59" maple bow, made from a straight, unaltered stave, shooting a 500 grain arrow, was tillered to draw 45 pounds at 22", shooting 128 fps. This bow pulled 14 pounds at 10" of draw, and after being unstrung had taken a 1/2" set.
It was retillered to draw 45 pounds at 24", shooting 133 fps. Weight at 10" dropped to 11.5 pounds and set rose to 3/4".
Retillering continued to 45 pounds at 26", shooting 137 fps. Ten-inch draw weight fell to 10 pounds, with 1" set.
Each re-tillered version was equally hard to draw to length, but stored increasing amounts of energy. Note how early draw weight fell as set increased. As will be seen in this chapter, set would have remained even lower if limbs had been wider, longer, or made of a more elastic material. Early-draw weight would then remain high, storing more energy, raising arrow speed even more."

Then he talks about various other stuff like limb-cross view, brace height, reflex and recurves, et cetera
After that it continues like this:

"All of the factors outlined so far affecting arrow speed- draw weight, draw length, string height, and bow profile -determine the amount of energy stored in a bow's limbs. But at release, as this energy begins to flow to the arrow, the following obstructions come into play.
Limb Mass
Medium length, straight-stave, 50 lb bows weigh about 23 oz. For bows of this length, weight, and mass, a difference of one ounce in limb mass, on average, affects arrow speed by about one foot per second. For mid-weight bows a difference in one pound of draw weight also equals about one ips of arrow speed. Lowering limb mass allows a lighter draw-weight bow to equal the cast of a heavier draw-weight bow.
Heavier woods are generally stronger and more elastic, therefore, less wood is needed to do the same amount of work. Lighter woods are generally weaker and less elastic, requiring more wood to do equal work. But, mass ends up about equal for same-weight bows made of light or heavy woods..."

et cetera,
one part is about the energy efficency of heavy arrows:

"Much of the energy stored in long and heavy limbs remains in the limbs after ,release, becoming hand shock, string twang, and limb vibration. This is why slower moving, very heavy arrows leave the bow quietly. Heavy arrows make bows more energy efficient because more of the bow's energy has time to leave with them.
This is why flight bows are golf club-like: short, low mass, fast-reacting limbs. Flight arrows, arrows light enough not to impede these fast limbs, can be shot much faster than normal weight arrows. The same flight arrow shot from an English war bow of equal weight would be considerably slower."

Tell me if you want me to scan more text from the book

[Narkar]

cant edit,

http://www.hot.ee/marti184/sear.jpg

It is a bit like gun trigger mechanism and is also used in some commercial crossbows, but the disk (black in the drawing) is oval and off-centre to lesssen the pressure on the trigger(red part).
The mechanism will cock itself when you draw the string back. I think you would need some short lenght of rails over the system to prevent the string from jumping above the bolt,

EDIT: I made a pretty big mistake, that design on my drawing wouldn't be able to withstand 500#

You would need to make trigger more like on medieval crossbows, the lenght above the spring would need to be shorter from the pivot point, and the trigger part should be very long and designed to be released by the whole hand, not just the trigger finger (just like medieval ones).

[Dave the Rave]

Narkar,

Now we´re talking ! With your copy of the book´s terms, I can understand some of your assertives, and also clarify some dark spots at my knowledge.

About your trigger, I think that it can hold 500lbs, as it will rely on the release system to held the pressure. One wholehand lever trigger can be more reliable and comfortable choice, but I think that it can be turned on an "single finger" to compact the size of the weapon and to make the action of discharge more smooth.

Maybe an lever to hold the circle and another lever to sear the 1st one...

What do you think ?

[Jacks Complete]

Glad to see the arguement has subsided!

The scanned text from the book was very useful, thank you to Narkar.

The wasted energy that makes the string go "twang" is what you use a heavier bolt for.

Ok, so, on with the design. What was the obvious mistake in the picture? I didn't see one. However, you would be well advised to use a better angle on the face of your release, as a vertical face needs very little force in order to tilt past vertical, and if that lets the bowstring ride over the cam, you might lose our arm with a bow as powerful as we are discussing here.

I would tilt it back at least 5 degrees. Also, I would cut further into your pivot/axle, as this will reduce the force felt by your trigger sear. Obviously, you want to be using high yield steel for this part, but even so, don't go too far. Also, if you have a long lever like that, it might upset your shot as it turns, making the bow jump further than otherwise.

I would go for a more circular one, and a two-stage sear and hammer system. That spindly sear/trigger you drew looks like it would bend long before it overcame the friction on the end of it, and the trigger would be very heavy, as the leverage goes the wrong way.

[Dave the Rave]

Yes, that´s my point. The roller block is one of the best designs to the xbow, and with one sear and one trigger the counterforce will rest against the pin, till the sear is moved by the trigger.

I think that the sear/trigger of the bolt action rifles is whats bether explains what I´m talking about.

Anyway, I´ll draw an skech to post here.

[MMIV]

why would you bother with such large pull weight? it would be useless in a defense situation such as you need winch to cock it and the size of it would make it less concealable, also dangerous to the user. it would better to stick with minimum 150LB- 200LB. :)

[tinkerman]

i made a rather rough version of a cross bow that would have a very high pull, the only problem is that i cannot make a efficient cylinder (like hydraulics but i was planing on pnuematics). use the leaf springs but design some type of lever system to be pulled back in the middle and it will tighten. pull the cable back and then pressure up cylinder. more pressuer means more power. need sturdy bolts or they will snap and go haywire.

i made another using fiberglass rods*4 loads of power and i encased the rods to prevent "an accident"
when testing make several versions auntill ur sure it is good enough for what u want.
for a string i used a medium aircraft cable. i only went to close to 200 lbs. crossbows are not supposed to be long range. 500 lbs would be more like a ballista