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Bolt-Action Aluminum Hybrid Piston Valve: Al-50

Built a hybrid cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Bolt-Action Aluminum Hybrid Piston Valve: Al-50

Unread postAuthor: frocksie » Thu Jun 24, 2010 3:16 pm

This project started in January with this design, but I improved upon it after realizing that welding the chamber would significantly weaken the chamber.

I then came up with the design below, which skirts the issue of welds by using bolted connections, as advised by Moonbogg. This design was made possible because I had access to a full machine shop (lathe, milling machine, etc.). To achieve a seal, o-ring grooves were machined in 6061 Aluminum plugs. I also machined a UHMW piston with an o-ring groove, as the design features a chamber-sealing piston.

I machined a bolt out of aluminum to allow for fast and easy reloading. The bolt has an o-ring to seal. On top of the launcher is a sch. 80 aluminum pipe which serves as a magazine. The balls are loaded into the magazine and then drop down into the barrel when the bolt is cycled. The magazine features a milled slot, allowing me to check the number of balls in the magazine.

To hold the chamber and barrel together, I made a frame out of square aluminum tubing and TIG welded it together. I then sandblasted the frame and the chamber and the barrel.

Ignition is achieved with a camera flash capacitor dumped through an ignition coil. I also made a remote-firing device with an RC car controller, an RC car receiver, and a relay.

For aesthetics, I added a flash suppressor machined out of sch. 80 aluminum pipe with slits cut with a milling machine. Its held in place with four set screws.

Specifications
Chamber: 14" of 2" I.D. 2.5" O.D. 6061 T-6 Aluminum Seamless Tubing
Barrel: 19" of Sch. 10, 1.5" Stainless Steel pipe
Valve: .75" porting chamber-sealing piston valve
Ignition: Camera flash circuit dumped through ignition coil with remote ignition system
Mixes: up to 8x, but mixes up to 15x should be possible.

I haven't fired it yet, but I will in the next week.
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Attachments
components full-2.jpg
Shot of chamber with machined parts laid out in their respective places.
barrel with bolt.jpg
flash supressor3.jpg
Mock flash supressor machined from sch. 80 aluminum tubing with a milling machine.
bolt.jpg
divider sealing face.jpg
Sealing face.
piston with face.jpg
Piston machined from UHMW
chamber plug with sparkplug.jpg
Chamber plug with sparkplug made from 1/8" NPT nipple filled with epoxy.
airspring plug4.jpg
Airspring plug with pressure gauge.
spacer transfer.jpg
Barrel spacer and gas transfer tube.
meter.jpg
Meter. Meter pipe is machined aluminum rod with 1/4" threads machined on both ends. The regulator is a Mead Fluid Dynamics Mini-Regulator.
full from behind.jpg
full from right.jpg
full from front left.jpg
full from left.jpg
Scan.jpg
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Unread postAuthor: CpTn_lAw » Thu Jun 24, 2010 3:23 pm

That is A-W-E-F-U-L-L-Y clean!!! Nice!! Can't wait for you to put a nice video of it in action!!! :D :D
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Unread postAuthor: SpudFarm » Thu Jun 24, 2010 3:23 pm

:D:D:D
This is what I like to see! There is activity in this section of the forum now.

This cannon is perfect! I would like to have something simmilar myself but I will have to stick with plumbingparts and elbow grease for now.

Good piston setup and inoative overall design. I am simply to stunned to say more.
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Unread postAuthor: jackssmirkingrevenge » Thu Jun 24, 2010 3:28 pm

Looking very good, though why not ditch the bolt action for a heavy spring and make it semi-auto...
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Unread postAuthor: frocksie » Thu Jun 24, 2010 3:34 pm

Semi-auto would be nice, but I couldn't vent the chamber and refill in time to make it work, unfortunately.

As it is, I estimate that I can fire three shots a minute, which for a hybrid of such power isn't too bad...
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Unread postAuthor: SpudBlaster15 » Thu Jun 24, 2010 3:36 pm

Absolutely beautiful work. Love the piston and bolt design, the machining, and the remote ignition system.

One question: Which radio system are you using to control the ignition setup? A build this nice surely deserves an interference free 2.4GHz spread spectrum system.
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Unread postAuthor: jackssmirkingrevenge » Thu Jun 24, 2010 3:39 pm

frocksie wrote:As it is, I estimate that I can fire three shots a minute, which for a hybrid of such power isn't too bad...


I'm guessing one shot would be enough for most targets :)
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Unread postAuthor: frocksie » Thu Jun 24, 2010 3:51 pm

The radio system is just a 49 Mhz Tyco Controller. It was just a quick little addition to allow for remote firing. I'm not sure about interference but there shouldn't be too much, because this cannon can only be shot in remote areas.

And jack, i agree and thank you. :D
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Unread postAuthor: Heimo » Thu Jun 24, 2010 4:07 pm

real impressive, nice job!

Would you please post damage pics....
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Unread postAuthor: Davidvaini » Thu Jun 24, 2010 10:00 pm

Why not use forced compressed air to vent the chamber? rather than a fan or something..

I agree this would be nice as a semi auto cannon...

But I hope this thread doesnt just turn into one of those...

"really nice looking cannon, but who knows if it works since there is no video"
threads.
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Unread postAuthor: Moonbogg » Fri Jun 25, 2010 12:48 am

This is a super unique design and I love it. Bombass job! May I bring something to your attention? I notice you have 4 bolts holding the end caps to the chamber in a shear configuration. Calculate the maximum force on those end caps, then divide it by four and make sure the shear strength of the bolts you use will be strong enough. Also, make sure the holes where the bolts go through the chamber don't see enough force to stretch, deform or crack the aluminum around the hole area. I considered holding end caps on this way, and I would suggest at least thinking about adding another 4 holes for a total of 8 per bolt pattern. This lessens the stress on each hole area. There is a lot of force on each of those small frontal hole regions, so dividing it up between more holes may be better. I will run a stress analysis for you if it would help.
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Unread postAuthor: jackssmirkingrevenge » Fri Jun 25, 2010 1:02 am

nipple filled with epoxy


FTW!

:D

Will you be making some sort of tripod mount for this? Poor thing looks a bit legless at the moment :roll:
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Unread postAuthor: frocksie » Fri Jun 25, 2010 1:17 am

Moonbogg, thanks for the concern, but before building it, I calculated the shear strengths needed and I can say that at normal operation I have a safety factor of 13. I didn't just go to the hardware store and pick out some $0.89 bolts. I did my research and ordered proper shoulder bolts. That being said, I will be sure to check the launcher periodically for any cracking or stretching of the aluminum tubing.

Jack, I considered it, but I didn't have enough time to finish one. I might make one out of wood just to get it up off the ground, but it wouldn't be anything too spectacular.

Why not use forced compressed air to vent the chamber?


I actually plan on doing this, although I may make a ducted fan to suck air through the chamber in order to vent.


But I hope this thread doesnt just turn into one of those...

"really nice looking cannon, but who knows if it works since there is no video"
threads.


I sure hope so too :D :D
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Unread postAuthor: SpudFarm » Fri Jun 25, 2010 10:26 am

When talking about a stand. It looks like you have quite a bit of mechanical knowlege. You should make a servo controlled stand for it!
That is something JSR would love :P
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Unread postAuthor: Ranger » Fri Jun 25, 2010 12:22 pm

I was thinking someting like this...
[youtube]http://www.youtube.com/watch?v=tzFnY1c1PQg[/youtube]

Horrible quality I know...
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