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TBMA-230 V2.0

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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Unread postAuthor: jackssmirkingrevenge » Tue Feb 14, 2012 5:35 am

Image

:D :D :D
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Unread postAuthor: POLAND_SPUD » Wed Feb 15, 2012 7:50 pm

SB we DEMAND moar vids!! plz plz plz
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Unread postAuthor: mark.f » Wed Feb 15, 2012 7:58 pm

Damn, I was going to post the same copypasta Zoos did until I went back a page to see who jack was talking to. :roll:
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Unread postAuthor: POLAND_SPUD » Wed Feb 15, 2012 8:01 pm

can we please stay on topic ?? This gun is great and it deserves moar attention.. not your offtopic comments



:lol:
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Unread postAuthor: SpudBlaster15 » Sun Feb 19, 2012 2:01 pm

POLAND_SPUD wrote:SB we DEMAND moar vids!! plz plz plz


Don't worry, you'll see plenty of videos in the spring.
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Unread postAuthor: mobile chernobyl » Sun Mar 11, 2012 8:05 pm

Just a little test run using some CFD software. Wanted to see just how bad of a performance hit you take with a conventional piston valved hybrid... video's speak louder than words sometimes! :D (Video is in 720p if you want to watch it in higher resolution you can full screen it!)

[youtube]http://www.youtube.com/watch?v=27Sdd0VOoE8[/youtube]
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Unread postAuthor: MrCrowley » Sun Mar 11, 2012 8:30 pm

Would help if you had a comparative analysis of a conventional, boring, burst disk valve for us non-engineering types :D

Though I would assume the fluid velocity would be up near mach 2 for an inline design?
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Unread postAuthor: mobile chernobyl » Sun Mar 11, 2012 8:39 pm

Its not the most accurate analysis in that sense - there is no "projectile" analogue. nor is there a valve transition from closed to open. It's more of a dry fire scenario. That is also why there is a generic number for fluid velocity right now. It's in between the combustion products SOS (based on GasEQ results) and what the projectile would actually be moving - a "ball park" figure if you will.

I'll work on learning how to add non-static objects to simulations after this semester. I'm doing static analysis right now for our schools Formula SAE team car... so that's about the extent of my knowledge so far!
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Unread postAuthor: Lockednloaded » Fri Jul 06, 2012 1:50 pm

Found this little gem looking at some old hybrid threads....

SpudBlaster15 wrote:I feel it is unsafe to use a hand held hybrid at anything more than a 4x mix.


You'd better get rid of this gun immediately :lol:
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Unread postAuthor: Spud Destruction » Fri Jul 06, 2012 5:28 pm

That thing is amazing. Makes me want to make one for the show. Maybe season 3 or 4. How reliable are they though? thats one of the reasons i went with the air cannon. Reliability, adjustability. when filming a show based on cannons we need it to work on command so i'm not wasting other peoples time.
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Unread postAuthor: MrCrowley » Fri Jul 06, 2012 6:16 pm

The only potential problem really is the piston valve. If you can make a decent piston, the cannon will work reliably. It generally takes some time for one to get the hang of a hybrid piston valve but once all the problems are sorted out they work every time. My valve probably went through 4 or 5 modifications (not including the 5+ modifications made to the bumper material and spool pilot valve) before I finally settled on the custom machined one you've seen in my recent videos.

If you start with a machined aluminium piston, you'll sort out the issues fairly quickly. The main problems that could arise are: barrel port sealing issues (inadequate/leaking sealing face), o-ring sealing issues (pilot not isolated from chamber due to wrong sized/damaged o-rings/grooves), piston bounce (not enough flow out the pilot valve), and an inadequate bumper (potentially destroying the piston).

You will probably have less problems going with a burst disk hybrid but they can be equally frustrating. It can be difficult finding burst disk material for large unions (>1.5") that are suitable for up to 10x mixes, can be cut to size easily and seal 100% at 'low' pre-ignition pressures (<150PSI). It takes several tests to find a suitable material that helps seal the disks in the union (o-rings or gaskets are usually used) and aren't damaged or shot out the barrel when the disks burst. You may also have to modify the union to stop the disks from slipping out of the union rather than bursting. An advantage with burst disk hybrids is the simplicity; less things to go wrong. If the union isn't sealing the disks, you can unscrew it and try something else immediately. If there's a leak in your piston, you have to find out where it is and then open the valve up to get the piston (which is a fair amount of effort/hassle for a large cannon like this) to try and diagnose the problem. Once it's fixed you have to put it back in, close the valve back up and test it out. This can take anywhere from 20 minutes to 24 hours (waiting for epoxy to cure).

tl;dr—if you want a cannon of impressive performance like a large-bore hybrid, you will have to make some sacrifices in reliability, cost and loading time. There's a great deal of ingenuity and improvisation required to keep the cost down in hybrids but you may pay for it with reduced reliability. Usually, as the cost of the project rises, so does the reliability.
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Unread postAuthor: SpudBlaster15 » Sun Jul 08, 2012 9:33 pm

Lockednloaded wrote:Found this little gem looking at some old hybrid threads....


Yeah, we had a few misconceptions about DDT back in 2007. :lol:
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Unread postAuthor: Buntyspudbaby » Sat Mar 30, 2013 4:43 am

Top notch design SB its pure excitement to watch the TBMA-230.
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Unread postAuthor: sudpuzzer » Thu Apr 11, 2013 2:47 pm

So, I am thinking about building a hybrid type cannon similar to this style. What kind of galvanized fittings are suitable? It seems like the most common I can find are Schedule 40, 150 psi rated. I'm guessing this is not enough. I have found a few rated at 300 psi, and the 3000 psi forged iron fittings run around $100 apiece. Does any one have any suggestions where to find suitable fittings and pipe in Canada?
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Unread postAuthor: MrCrowley » Thu Apr 11, 2013 2:52 pm

As far as I'm aware, both SpudBlaster15 and myself used the 150PSI rated galvanised iron fittings found in most hardware stores. They say the working pressure is 150PSI but they can take a lot more than that. They probably wouldn't actually fail until you reached 2,000-3,000PSI, if not more.
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