I am Extatic!

[Moonbogg]

So I designed a cannon and its going to being fabricated!! One of my clients is letting me pay for it with CAD drawings!! I am so stoked. This thing is going to cost more than just a few bucks to make, and all I have to do at the moment is buy the material and give them the drawings.
I'll take as many pictures of its development as I can, problably starting with a pile of aluminum tubing all the way to a shiny, polished and anodized beast of a hybrid.
Heres a couple screenshots of the model. Still some minor changes to make, but this is it for the most part anyway.
I was worried about the welding weakening the material. But the trick is to use a heat treatable filler rod, weld it all up, send it out to be annealed and THEN heat treated last, with the annealing being a key step. Otherwise the aluminum will have strength issues near the welds.
If anyone has any design input, feel free to tell me because as soon as I order the material i'm going to have it made.
Wish me luck!

[MrCrowley]

Very cool, but why not make it a hybrid?

[dudeman508]

He is

beast of a hybrid.

[Moonbogg]

Very cool, but why not make it a hybrid?

I suspect my biggest problem will be recoil. Oh yeah, forgot to say i'm adding a recoil pad of some sort....and a laser sight of course.

[MrCrowley]

He is

beast of a hybrid.

I see three things wrong with this:

1: He has a ball valve to vent, in a hybrid you don't need to vent like that.
2: He has a fan, I don't think anyone has put a fan in a hybrid before.
3: He has a pressure gauge for the chamber.

I take it that Quick Connect is for a portable fuel meter then?

[rp181]

If there is a pressure gauge for either pre ignition pressure or fueling, add a ball valve to close off during ignition. A fan is not necessary, it was discussed before and was said that thee input turbulence is enough to mix it.

[Cosmic Muffin]

i dont think the pressure gauge is gonna like being subjected to the full force of the combustion

[rp181]

why not? it could hurt the accuracy of its readings alot.

[D_Hall]

i dont think the pressure gauge is gonna like being subjected to the full force of the combustion

Two words: Needle valve.

[D_Hall]

1: He has a ball valve to vent, in a hybrid you don't need to vent like that.

Depends on what you desire for shot to shot consistency. You may not NEED to, but that doesn't mean it isn't a good idea.

2: He has a fan, I don't think anyone has put a fan in a hybrid before.

So? 20 years ago nobody put fans in simple combustion guns either. He may be on to something.

(Besides, I'm putting fans in mine so I've gotta stand by him.)

3: He has a pressure gauge for the chamber.

Trivial to isolate either passively (needle valve) or actively (small ball valve).

[Cosmic Muffin]

why not?

maybe because it will blow the gauge?
i didn't see your post there, sorry, closing off the gauge before firing is a good idea.

Two words: Needle valve.

why would you use a needle valve...

[MrCrowley]

1: He has a ball valve to vent, in a hybrid you don't need to vent like that.

Depends on what you desire for shot to shot consistency. You may not NEED to, but that doesn't mean it isn't a good idea.

2: He has a fan, I don't think anyone has put a fan in a hybrid before.

So? 20 years ago nobody put fans in simple combustion guns either. He may be on to something.

(Besides, I'm putting fans in mine so I've gotta stand by him.)

3: He has a pressure gauge for the chamber.

Trivial to isolate either passively (needle valve) or actively (small ball valve).

I was stating those observations for why I didn't believe he was building a hybrid, not why he shouldn't.

If he has a portable meter, a chamber gauge isn't needed unless he's recording the max pressure, which will cost him a lot in gauge money.

The fan, well no one has tempted it before and people seem to agree it makes little difference.

Ball valve, just seems like a good way to make the cannon a little bit weaker.

Like I said above, those are reasons why I thought he was building a normal combustion, not why he shouldn't be building a hybrid.

[D_Hall]

If he has a portable meter, a chamber gauge isn't needed unless he's recording the max pressure, which will cost him a lot in gauge money.

I suppose I'm a bit biased by my own design, but mine will actually include several "built in" pressure gages and require no pressure measurement from the fill system (I'll be plugging directly into air compressors).

The fan, well no one has tempted it before and people seem to agree it makes little difference.

If no one has attempted it, where is the consensus that it makes little difference coming from? I'm not necessarily rolling my eyes, it's an honest question.

Ball valve, just seems like a good way to make the cannon a little bit weaker.

Shouldn't make one bit o' difference if the design is at all rational.

Like I said above, those are reasons why I thought he was building a normal combustion, not why he shouldn't be building a hybrid.

Fair 'nuff. I missed that part.

[MrCrowley]

If no one has attempted it, where is the consensus that it makes little difference coming from?

Not really a hybrid type-o-guy myself so I haven't looked into it, I guess it's just 'word on the street', is that right? That's what people these days say, eh?


Anyway...Looking forward to seeing this cannon completed. Sorry if i've missed other discussion, but what mixes will this thing be running at?

[D_Hall]

why would you use a needle valve...

It's a common trick in the hydraulics world to protect gages from pressure spikes. Granted, I've never seen a pressure spike of more than 1000 psi on a system that hydraulic system that operates at 3000 psi (yes, I'm thinking of a specific system from the office... 4000 psi peak with the spike), but the concept could work in this world as well.

Chamber -> needle valve -> gage.

The needle valve restricts flow to the gage. If mass can't flow quickly, then pressure can't change quickly (either up or down!) either. In this case, you'd want to put the gage inline with your fill mechanism (so there IS a problem with the design as implimented) so that the gas trapped between the needle valve and the gage is air and not fuel/air mixture. Thus, you prevent rapid expansion of the gases in that region and need only concern yourself with incoming gases from the chamber (which the needle valve will be expected to deal with).