Cobra Striker

[Moonbogg]

Lets start with the video!



CANNON NAME: THE COBRA STRIKER

SPECS:

VALVE TYPE: BURST PISTON-VENTILATED (1" ID)
FUELING: 5x OXY/MAPP THRU 500PSI CHECK VALVES
C:B RATIO: 1.23:1
CHAMBER: 3 1/2" SCH40 X 10" (98.9cu in)
BARREL: 1 1/2" SCH10 X 36"
IGNITION: MULTI-GAP STUN GUN (150K VOLT)
HGDT ESTIMATED VELOCITY W/ GOLF BALL: 900FPS @3FT BARREL. 1030FPS @4FT BARREL. 1100FPS @5FT BARREL & 1160FPS@ 6FT BARREL.

MATERIALS:

6061-T6 ALUMINUM
B7 STUDS (5/16-24 FULL LENGTH)
GRADE 8 NUTS
POLYPROPYLENE
UHMW
STAINLESS PISTON GUIDE RODS

COST: TIME,SWEAT

MISC INFO: Cannon is in prototype form. Gaskets will be Copper (current PTFE gaskets stretch). Breech will not leak (solved). O2 will not be purged, but pressurized with gage. Cannon will utilize more robust sparking system, likely spark plugs due to extreme heat/pressure. Striker disagrees with chamber fans. Velocity to be verified and documented with existing 3ft barrel.


DESIGN EVOLUTION TO COMPLETION:

[GalFisk]

Aha, so that's how the valve works. I couldn't figure it out exactly from the description in the contest post. Nifty!

[jrrdw]

You should do chrony testing with the leak and then after the leak repair just to see how much power you were losing.

Really nice work!

[qwerty]

Man... thats a really nice piece of work and it got my vote but i still dont understand the difference between piston hybrids and normal hybrids because i know how normal hybrids work but not piston ones.
Is it a piston piloted by a burst disk when you fire the cannon?

[psycix]

It is... shiny.


Good job on the breakbarrel, quite a challenge to make it seal and safe on those pressures.

[chenslee]

Oh, Moonbog. Beautiful work. I shat a brick when I saw it was you that made this!!

If you didn't use a mill or lathe on this (IIRC) how did you cut the chamfer on the breech sleeve?

What cad program are you using?

HAHAH. It looks like you did the same thing I did on a project awhile back. I was SURE I could find extra long socket head cap screws. Looks like you had to go with studs. I figured it was nuts and studs that were under the pretty black caps.

[jackssmirkingrevenge]

Extremely well made, it certainly was a tough contender against chenslee's launcher.

[Moonbogg]

Thanks everyone! I am thrilled to have been able to place in this competition. It was great fun.
@Chenslee, the huge chamfer was made by using a bench top sander and holding the tube steady and rotating it to get the chamfer cut. After going through about 2 new sanding discs, I got it shaped and then used progressively finer sand paper by hand to smooth it out, then finally a rag and some compound. I tried a drill press with a buffing attachment, but I couldn't get the force needed to polish well, so I loaded a rag with compound, and started scrubbing.
The piston was the real PITA. I started with 1 1/4" round stock and drilled the thing out using progressively larger drill bits, all the way up to 1".

[Brian the brain]

Freaking awsome.
Now why didn't I see that breakbarrel picture in the contest?


Oh well...

I guess one vote wouldn't have made a huge difference..

I said his thing lacked creativity...I was dead wrong..
Unbelievable how you pulled this off without a machineshop...
Truely amazing!

[chenslee]

Wow. You have mad fab skills! I love the threadless pipe fittings. I'm still blown away by your internals.

I have tons of questions like:
What brand of clamp collars did you use? Where did you get them?
Where did you get your aluminum tubes?
Did you buff all this on your drill press or do you have a polishing wheel?
How did you cut the tank holes in what I assume is UHMW plastic?
Where did you get the black nut caps?

[Hotwired]

That breech loading system scares me

Seriously, I can see chamber flash coming out from there, how are you sealing it.


Aside from that, shine on 8)

[Moonbogg]

Wow. You have mad fab skills! I love the threadless pipe fittings. I'm still blown away by your internals.

I have tons of questions like:
What brand of clamp collars did you use? Where did you get them?
Where did you get your aluminum tubes?
Did you buff all this on your drill press or do you have a polishing wheel?
How did you cut the tank holes in what I assume is UHMW plastic?
Where did you get the black nut caps?

Thank you.

Clamp collars are from McMaster. They are classified as structural tube/pipe fittings.

I ordered all aluminum parts in the diameters and thicknesses needed from an online small quantities metals store. This eliminates the need for mills and lathes. http://www.onlinemetals.com has all of it besides the 1 1/2"sch10 barrel. That came from mcmaster.

I started out buffing with a polishing wheel attached to a drill press. It didn't cut it because i couldn't press hard enough, so I QUICKLY discovered the best way by far is to do it ALL by hand. I used a rag and a buffing compound. Lots of pressure can be applied by laying the rag flat and rubbing the aluminum on it. Prepare to sweat.

Tank holes were cut by using a single drill press hole cutter from mc master. It has an adjustable blade that allows you to cut any size hole in sheet metal and plastic ranging from like 1 1/2 up to 7" or so. The tank holder material is polypropylene as it is super tough, rigid and very economical.

Black nut caps are from Mcmaster as well.

[jaythedogg]

WOW!~ That is PURE SEX dude! Nice!

[chenslee]

McMaster FTW.

I ordered 8mm and 1/2" collars and got a mix of Ruland and Climax. Some spacers, o-rings, pressure gauge, and the constant force springs on my cannon were all from McMaster too.

I can't believe you HAND polished all of that. It makes me want to strip the paint off my plates and polish them like that.

[Moonbogg]

McMaster FTW.

I ordered 8mm and 1/2" collars and got a mix of Ruland and Climax. Some spacers, o-rings, pressure gauge, and the constant force springs on my cannon were all from McMaster too.

I can't believe you HAND polished all of that. It makes me want to strip the paint off my plates and polish them like that.

I swear dude, you could polish that entire thing and it will look hella pimp. Take a fine grit sand paper to everything, removing any scratches. A good way to do it is to make sure the sanding is done in a uniform direction, this will make it look cleaner and shinier. Then buff away! After buffing with a medium grit paste, go for the polish! Do the tubes also! It will look amazing.

EDIT: to get into the grooves of those tubes you have, you could use a stick and wrap a cloth around it and put the paste on the cloth, then run it along inside the grooves with a nice, firm pressure. Then polish the same way.