Need suggestions for top shelf combustion

Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
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spudmatic
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Fri Jun 13, 2008 1:54 am

I'm planning on making an ultimate combustion and I want you guys to help me plan everything out. Due to the fact that I'm fairly new at spudding I'm not sure about all the aspects of certain products.

This will be a propane(metered and injected) and chamber fan the whole nine yards... The first step that has been jumping around in my mind is normal basic setup or overunder? I want this thing to be as powerful as a combustion counld possibly get.

Now for materials I'm thinking all pvc construction with an abs cleanout as I have heard its much safer.

Ok guys, tell what you think and I'll take your ideas and draw out a concept model.

Also I found a plumbing business near my house that has a yard full of pvc, it looks like a spudgun heaven. There are pipes ranging from 2in to what I estimate to be about 18 INCHES in diameter but I dont want to go too overboard. So if anyone has experience with large bore over under chambers I wouldnt mind hearing of a good size too use again without going too big.

And for barrel size I'm thinking just a 2in so I can have the weighty spud rounds. Willing to go bigger if anyone can put up a good argument.
The definition of spudcannon should include combustion, if I wanted to shoot a pneumatic I'd go get my paintball gun.
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starman
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Fri Jun 13, 2008 2:09 am

Personally, I would rather you plan on generally designing your ultimate spudgun yourself and asking for help when you run into trouble. It sounds like you have a good idea about how you want to proceed on most issues.

Everyone has their own opinions regarding design, inline vs over/under, etc. Why don't you scan through the cannon showcase and decide what you want.

It's cool you have access to the big plumbing supply. That will be handy when you need pressure rated parts and odd sizes like 2.5" PVC pipe and fittings.
Last edited by starman on Fri Jun 13, 2008 8:48 am, edited 1 time in total.
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spudmatic
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Fri Jun 13, 2008 2:16 am

Yes, your probably right I should have thought this post out more thuroughly(not spelled right) then I did, as now I realized how many crucial details I left out. I'll make a design and post it tomorrow then you guys can yell at everything I did wrong :wink: .
The definition of spudcannon should include combustion, if I wanted to shoot a pneumatic I'd go get my paintball gun.
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spudmatic
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Fri Jun 13, 2008 4:22 am

Ok, I've come up with a solution. It will be an inline cannon so that I can get a much more powerful shot all the bends in an overunder take away from what I am trying to achieve.

Just one question, does anyone see a problem with a 5in-4in bell reducer?
I would think that as long as I use primer and keep my sparks away from it that I should be fine.

Here is another reducer I found not sure what type it is though:
The definition of spudcannon should include combustion, if I wanted to shoot a pneumatic I'd go get my paintball gun.
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Fri Jun 13, 2008 6:04 am

Bell reducers aren't pressure rated, if you're willing to live on the edge, then go ahead.
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Fri Jun 13, 2008 8:58 am

spudmatic wrote:Ok, I've come up with a solution. It will be an inline cannon so that I can get a much more powerful shot all the bends in an overunder take away from what I am trying to achieve.

Just one question, does anyone see a problem with a 5in-4in bell reducer?
I would think that as long as I use primer and keep my sparks away from it that I should be fine.

Here is another reducer I found not sure what type it is though:
OK I personally agree with your inline decision, only because I prefer them as well, no other reason. Others will recommend an over and under...

Second, don't even think about using that reducer you linked to. It's part of a shop sawdust collection system and it isn't pressure rated.

Don't use a bell reducer. Use a reducer bushing instead to do your reducing.
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Fri Jun 13, 2008 9:27 am

spudmatic wrote:Willing to go bigger if anyone can put up a good argument.
In terms of performance, bigger is *always* better. The bigger your launcher of course, there are downsides - higher material and running costs, harder to move around and to store etc. - so in general, I would advise that you make it as big as you feel comfortable handling. Of course you also have to consider your shooting area, there is such a thing as a cannon that is too powerful, especially if you reside in an urban area.
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spudmatic
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Fri Jun 13, 2008 11:25 am

jackssmirkingrevenge wrote:
spudmatic wrote:Willing to go bigger if anyone can put up a good argument.
In terms of performance, bigger is *always* better. The bigger your launcher of course, there are downsides - higher material and running costs, harder to move around and to store etc. - so in general, I would advise that you make it as big as you feel comfortable handling. Of course you also have to consider your shooting area, there is such a thing as a cannon that is too powerful, especially if you reside in an urban area.
I'm not sure if you quite caught what I was trying to say there about the willing to go bigger thing I was actually reffering to barrel size.

And starman I realize that the bell reducer is a bad idea but it is very hard to find fitting for bigger pipes especially pressure rated. I looked into 6in and found the stuff I would need but, the 90 degree elbows would cost me about $30 a piece :cry: .
The definition of spudcannon should include combustion, if I wanted to shoot a pneumatic I'd go get my paintball gun.
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Fri Jun 13, 2008 11:29 am

Not to be rude or anything, but safety does come at a price, and its always more than we want it to be.
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Fri Jun 13, 2008 3:10 pm

Hopefully I didn't miss the point of these posts, flexpvc.com has pressure rated "bell" reducers. 4" to 2" schedule 40 and 6"to 4" schedule 80. Last shipment had a problem and within a week I had the correct part with a prepaid envelope for the return. Good place.
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STHORNE
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Fri Jun 13, 2008 3:15 pm

OVER UNDER!!!

They are a lot more space efficient and the performance decrease to that of a "straight" design is unnoticeable without actually measuring out the performance/ fps.
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Fri Jun 13, 2008 3:23 pm

Just make sure you have interchangeable barrels that makes every cannon a load more fun.
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Fri Jun 13, 2008 3:26 pm

lol, yeah.

breech loading and a burst disk fastening area wouldn't hurt either :wink:
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Fri Jun 13, 2008 4:07 pm

Maniac wrote:Just make sure you have interchangeable barrels that makes every cannon a load more fun.
Amen!

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Fri Jun 13, 2008 4:23 pm

I would go with an over-under if it were me, you can make the cannon a lot larger yet more compact, plus you can make a barrel support, which is awesome. If you go with interchangable barrels, I would really recomend a golfball barrel (1.5 inch sdr 21). that has been my favorite so far.

I hear what you are saying about the prices of larger fittings, 3 inch and up gets pretty ridiculous fast as far as prices. Go as big as you can afford.
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