Forum woes and impending doom.

[Cyclo_Knight]

Im in quite a rut...NBK is threatining me with death unless I can post some pictures of my railgun. Problem is I dont own a digital camera...and im poor as fuck. :( Since I dont have a dig. camera my only other option is scanning in a regular photo...but I still have to get it developed...

Since I dont feel like getting reported by the photo boot guy (my railgun is very clearly a weapon) I dont know how to get a pic. Even if i got a developed pic, I would still have to scan in the pic at Kinko's...and I dont know if thats safe either.

If anyone else has ever had a problem like this please help me out...I will be ever in your debt. :D

EDIT: Wow...i just looked at the link to Powerlabs provided by nous 2 posts before mine. I had no idea that THAT is what a railgun is. I just called MINE that beacuse it fired a steel rail spike!
I wondered why NBK called me on the "Mr. Wizard" clause...now I know!
I sure hope he doesn't ban me because of that misunderstanding

[nbk2000]

If there was a misunderstanding, it was on your part, because you didn't adequately describe what you were talking about.

Please detail what it is that you ARE talking about, here and now, and I'll decide your fate.

PS: Lack of funds is an inadequate excuse, as digital cameras are available for $20 at Wal-Mart, Office Depot, and other Mega-Retailers. Buy one, use it, return the next day saying "My computer wouldn't recognize it", and get your $20 back.

[Cyclo_Knight]

My "Railgun" is basically a .75" BP Cannon which fires a 4"sharpened steel spike instead of a ball.

The Barrel is simply a 2" solid steel pipe 2.5' long with a .75" bore. I obtained the pipe on a visit to a waste water treatment plant which I am designing the bacterial growth grids for in ACAD 2000. The plant is currently under construction, and they had several spare feet of this pipe(which is used to support the giant stacks of grids) awaiting pickup. I saw it's potential and asked to foreman if I could have a section, and he sawed me off a piece.

In my girlfriends college art room, I melted a crucible of lead in a gas kiln, dipped one end of the rod in and let it cool to form an endplug. I then broke the crucible away and sawed off some of the excess lead.

The frame is constructed of 2 pieces of 1/2" solid steel piping welded parallel to the barrel on each side, bent down around the endplug, and down at a 45 degree angle. There are branch offs on the main pipe 1 foot from the end which runs parallel to the barrel for 3 feet. These are 2'9" apart and are weighted down with 2x45 lb barbell weights on the ends. There is another segment running 9" from the end of the horizontal ground-bars back up to the barrel and welded parallel to it for structural support.

The overall look is of a quadrilateral with some sides extended beyond the intersection. The last foot of the 45 degree downwards pipe is welded to a 2x3x0.12" steel plate and is inserted firmly into the ground. This as well as the weighted front end help to control recoil and prevent it from moving backwards when shot.

All of the pipe-bending and welding was done wih a 20 ton hydraulic hand-press and an arc-welder at the garage I used to work at.
All materials were obtained from Home Depot(except the barrel).

On a side note...The lead endplug is begining to seperate from the barrel. I noticed it on my inspection after the 12th shot. It just barely wobbles and I dont think it could take another shot :( Im going to remelt the lead, but this time ill heat up the barrel red-hot with a propane torch to increase merging of the lead and steel. I just hope the torch is powerful enough to heat the barrel hot enough.

Thankyou for the second chance NBK. :D I assure you I wont screw up again !

[MightyQuinn®]

Just a thought, but you could put that welding rig to a better use by welding in an endplug instead of using lead for a plug. I figure a welded steel plug will far outlast anything as soft as lead.

Lead would have been my LAST choice as I have no desire to be subjected to large amounts of it while engaging in any hobby and lead is simply too soft to be useful in this application.

**Edit: If you insist on (or have no choice but to) use lead, consider cleaning the parts of the pipe that you intend the lead to stick to with an angle grinder or sandpaper et al. Then use a liberal application of an acid-based flux to help improve your chances of lead bonding to steel. You may also consider some alloyed type of lead....think plumbers solder.
**End of edit.

[Cyclo_Knight]

If would take about 40 bucks worth of coil to have enough metal for an entire plug...Plus thats impossible. The melting coil would just destroy the inside of the barrel, and send spatters of metal deep into the tube thus ruining my cannon. The only thing like that I could do would be to pound a .75 inch steel rod into the end and weld it into place. However, the weld would shatter on the first shot and send the endplug flying out. Not to mention that the end is still fouled up with excess lead making the insertion of the rod nearly impossible without reboring it...which i do not have tools for.

No, I think i'll keep this design, and hopefully the plug will stay in place after this new method.

EDIT: I think ill go down to ACE and see if they have any of that flux you mentioned. Thans for the tip!

[MightyQuinn®]

Here’s another idea; I am full of them. I picked this up from one of those damned mechanical, blah, blah, blah shows on the brain (drain) channel.

You could find a plug that is a couple of thousandths LARGER than the inside diameter of the pipe (.76-.78.)

With a torch, heat the end of the pipe up RED HOT. This will do 2 things, melt out all the residual lead and more importantly EXPAND the pipe to around the same size as the plug you hopefully were able to obtain. When the pipe is at it’s hottest, pound the plug in to the pipe as far as it will go while continuing to apply heat. When the plug is flush or will travel no more, remove the heat. The pipe will contract around the plug giving a very effective friction fit, which can then be bolstered with a good, solid weld around it.

[Bert]

welding was done wih a 20 ton hydraulic hand-press and an arc-welder at the garage I used to work at.

If you have access to their tools, look for a 3/4" or larger tap, and a bolt that
will make a better breech plug.

A cast lead plug- "You gonna die, boy!" Your cannon will turn recoilless rifle on you and fire TWO projectiles. One towards you, and one towards the target.

[Cyclo_Knight]

Indeed bert...however I make it a point to NEVER stand directly behind my cannon due to several unfortunate accidents I have read about. Im always well off to the side, out of the way incase it does suddenly go recoilless.

I may just use the 20 ton press to force a 4" rod machined to several thousanths larger than 3/4 in. into the end. I'll reinforce it with a heavy weld and a threaded cap to hide the unsightly mess my poor welding skills are sure to leave! :p

The tiny amount of lead left in the barrel may also act as a sort of "glue" to increase the strength of the friction joint...hopefully. I just hope it wont act like a lube...They added lead to old gasolines for that very property. If it does i'll just have to rebore to clear out any traces of lead. I dont have the specific tools made for that, so i'll have to use a 3/4 in. bit on the drill press. I hope it doesnt destroy the bit though, those bitches are expensive!

[Sparky]

This idea is very easy and simple, and I think it would work well. I'm only suprised it hasn't been mentioned yet.

The expanding the barrel then putting a rod up in there sounds like pretty good but I wouldn't want to trust a friction fit alone. Instead, a good mechanical lock would be better. Just put a tight fitting rod into the end of the pipe and then drill a hole through the entire thing and put a big pin in sideways. If you could get some solder to flow in and fill any gaps all the better. Here, I even made a diagram:
http://www.pigscanfly.ca/pyropage/GunPlug.gif

You could even put the pin in, fill the end with lead, and let the lead flow around the pin.

The only problem I can see is if the barrel is difficult to drill through because it is especially hard or something. File a flat spot to start the drilling of course, so the bit doesn't slip all over (assuming you're using a hand drill).

[Bert]

I just hope it wont act like a lube...They added lead to old gasolines for that very property.

Lead is added to brass that is to be machined because it DOES act as a lube. I've seen old fashioned pillow bearings made out of lead blocks too. The old gas had tetraethyl lead added as an anti-knock (prevented diesel type pre-ignition in high compresion engines) not as a lube.

A 3/4" pipe thread tap shouldn't be too tough to find. Try just going to a hardware store that cuts and threads pipe, ask them to do it for you on their machine. Hell, they'll even have threaded Iron plugs you can use "as is" in the plumbing section, you'll only need to get the tube tapped...

[Cyclo_Knight]

OK...Heres what im gonna do: Taking the best from all suggestions.

I'll go down to the local HW store and get the inside 4" tapped with a nice deep thread. I'll then get a 3/4" rod threaded the same. After that, liberally apply some heat-resistant epoxy to the barrel threads and screw in my plug. Ill drill 2x1/4 inch holes, 1 inch from the bottom and 2 inches apart, insert some steel dowels, and weld them into place. I'll then put a heavy weld on the end of the barrel, thread the outside, and put on a steel pipe cap. A light weld on the endcap and i'm all set...whew!

Thanks for the help all!

[Bert]

Um, do you wear more than one set of suspenders along with your belt?

I've worked on a number of muzzle loaders up to .75 cal. rifled and 10 bore shotgun. A threaded breech (intended to be removable!) is pretty standard...
What you're talking about is a bit overkill, perhaps!

[Cyclo_Knight]

Overkill? Most Definitely!

Still...Better safe then sorry. I probably wont weld the endcap, as that would not do much anyways. I do not intend to remove the breech plug, so the fact that it's completely solid wont affect me.

Dont know what the heck you're talkin' about with the suspenders comment, but whatever.

[simply RED]

Railgun and BP cannon are extremely different "weapons".
Railgun fires with electric impulse while the cannon - with black powder.

[Bigfoot]

Cyclo,
About that threading...

Is your pipe cast iron or steel? Pipe threads are meant for cast iron pipe, they're fairly coarse because cast iron's shear strength is lower--fine threads would break off. For steel, fine threads actually produce a stronger joint. Coarse pipe threads will work, though, you just won't get maximum strength.

Also, having 4 inches tapped is gonna be hard at the HW store. Unless they have a special threader or a lathe, the only way they'll be able to thread pipe is outside threads, and tapered. I found out myself after I read "Homemade Guns and Homemade Ammo", which will probably be on the FTP when it goes live.

Be safe!

[Cyclo_Knight]

I might only need 2 inches, and thankyou for your info on the threads. You may have just saved my vital organs from premature ejection! :p

I talked to the guy at the Home depot, and he gave me the name of a place that could do it. I was planning on going down there next week, but now I can avoid the hour drive out there. This steel is very hard and quite high-grade.

With the dowels included I doubt there is any danger of my plug blasting off, as it would be stronger than the rest of the pipe!

[Harpoon]

How is your cannon ignited and how is the ignition system fixed to the cannon?

I'm very tempted to build a similar cannon, only scaled down, but am wondering what type of material I should build it out of. IMO cast iron has more of a tendency to shatter than steel, due to it being more brittle. Shattering is a bad idea, should I wish to stand anywhere near to the weapon.

EDIT - Thanks Anthony, several hundred thousand PSI sounds excessive, but will give me a better error margin if I cock up with the propellent :p
I'll do some reading about the pressures developed in firearms before I embark on this project.

[Anthony]

Steel, drawn (seamless) hydaulic tubing should cope. Rated pressure is often around 50 000 psi for small sizes, tested burst pressures often reach several hundred thousand psi.

Small sizes (inch or smaller) are pretty cheap too. If you're in the UK, RS Components sell it.