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First hybrid build

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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Re: First hybrid build

Unread postAuthor: Scrambles622467 » Thu Mar 06, 2014 10:08 pm

So I am considering my pitons design, and I'm thinking1 what parts do you guys use to put your pitons together? My other question is about the the piston exhaust I've been looking into that part of it and I just can't figure it out. I was considering buying a piece of 2 inch solid steel that's 4 maybe 5 inches long and having my work machine it for me but I'm not sure I wanna go that route. Any ideas?
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Re: First hybrid build

Unread postAuthor: MrCrowley » Fri Mar 14, 2014 5:16 pm

I would recommend streamlining everything. I'm not sure if the right reducers are hard to come by or you just didn't have any on hand but it would be worthwhile to get the correct ones to minimise the length of the fuel meter and such.

Also, is that a pressure gauge directly connected to the chamber? That's not going to work, it will be destroyed. I'm not sure how safe the cannon would be at 15x-20x, you probably don't have much to worry about as the ball valve seals could possible fail first but I still wouldn't want to be standing next to the thing. Have a look at some of the remote ignition designs on the forum:
materials-ammo/topic24761.html

The reason I suggest you streamline the chamber is because mixing the fuel may be problematic. Manometric metering over volumetric could work better here. The best places I can see for ignition would be the back-end of each chamber, that's sort of in the middle and I imagine would work best unless you change your design.

What's with the piston housing by the way? From what I can tell, there is the piston-housing tee with a port for the barrel but end-capped on the other port and then another tee fitting behind that one with the two ball valves and such. Unless the picture is distorting my interpretation of the design, I can't really see where you will put the piston with the fill and pilot valves.

Scrambles622467 wrote:So I am considering my pitons design, and I'm thinking1 what parts do you guys use to put your pitons together? My other question is about the the piston exhaust I've been looking into that part of it and I just can't figure it out. I was considering buying a piece of 2 inch solid steel that's 4 maybe 5 inches long and having my work machine it for me but I'm not sure I wanna go that route. Any ideas?

There are only a handful of piston valved hybrids on the forum, I'm sure most of them show you what our pistons are made of :wink:
There might be a few discussion topics about pistons too, I'd suggest searching for those as well.

My other question is about the the piston exhaust I've been looking into that part of it and I just can't figure it out
You probably should have figured that out before starting construction :D
Being serious though, what made you want to build a piston hybrid if you didn't know how they work? I can understand members having difficult in designing or implementing a good exhaust system, but not knowing how some of the common designs work is problematic if you want to try and build one. Basically, break down how a piston hybrid works due to the forces. It's very similar to a pneumatic piston valve cannon, so start with those. What's similar and what's dissimilar between a pneumatic and hybrid piston cannon? Why does the hybrid cannon need a unique exhaust valve? You should start to realise that the hybrid piston needs to open when peak combustion pressure is reached, how can you make a valve do that? If the chamber pressure pushes a piston back, but the air behind the piston is still trapped there, how can you release that air? By adding a spool attached to the back of the piston, which unseats a valve port when the piston is moved back, air behind the piston can escape out this port and allow the piston to move back without compressing the air behind it.

I was considering buying a piece of 2 inch solid steel that's 4 maybe 5 inches long and having my work machine it for me but I'm not sure I wanna go that route. Any ideas?
Are you talking about the piston again? Solid steel would be pretty heavy (even for me, JSR!) and overkill, aluminium would be a better alternative. I had a home-made piston for sometime but it was annoying to fix and maintain every now and then so I got a solid piston machined from aluminium by a kind member on the forum. They're much easier to work with so I would definitely recommend it even if it sets you back <$100.
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