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semi-hybrid

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: metallover » Thu Apr 24, 2008 6:22 pm

I am looking of ways to improve my propane advanced combustion cannon. Instead of adding a chamber fan, which is the only other thing I could think of, could I put a small amount of compressed air (5-10psi) into the chamber after the propane? It would kinda be a hybrid...
I would of course add more propane

Tell me if you think this will work or if you know any other ways to increase performance. This is only my second gun, so bear with me.

Here is my gun. It is made of sch40 pvc and was double glued with pvc cement. It shoots about 200 yards into the air on a good shot. I fill it with a air chuck and schrader valve. It has a 16" 3"dia. chamber after the fittings and a 38" 1.5"dia. barrel for close to an .8:1 ratio. [Edit: 1.5:1 ratio - not so good] I could extend the chamber/barrel in the future if you think it would be worth doing.
Image
I got a lucky picture and caught a spark. It has a bbq ignitor with two sparks on opposite ends of the chamber.
Image
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Last edited by metallover on Thu Apr 24, 2008 11:00 pm, edited 1 time in total.
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Unread postAuthor: bigbob12345 » Thu Apr 24, 2008 6:28 pm

Looks like a great gun but DO NOT USE IT AS A HYBRID
sch80 hybrids are bad but that is just plain suicide
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Unread postAuthor: Sticky_Tape » Thu Apr 24, 2008 6:38 pm

Boom. (Message too simple)
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You can tell how awesome a cannon is by the pressure used.
http://www.spudfiles.com/forums/high-pr ... 12803.html
xnt rnm ne z ahtbg
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Unread postAuthor: Blitz » Thu Apr 24, 2008 6:40 pm

Your C:B is not even remotely close to 8:1 -- it's more like 1.68:1. Which is good, cause 8:1 would be so overkill you'd probably be wasting energy.

I'd say stick with the chamber fan. With the injection of a small amount of air, you have to compensate by adding more fuel, and you'd need to calculate how much to add, etc. Not to mention, I wouldn't recommend running beyond a 1x mix in a sch40 PVC cannon.
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Unread postAuthor: metallover » Thu Apr 24, 2008 10:56 pm

O MAN! whoops. thanks for telling me... I used the default 9" for chamber length and didnt change it to 16". Would my performance increase much if I lengthened my chamber to 72" to get a real .8:1 ratio? I really want the most performance out of this thing as I can get without spending too much.

Blitz - by overkill, do you mean a lot more performance or so much energy that some would be wasted?
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Unread postAuthor: Blitz » Thu Apr 24, 2008 11:00 pm

metallover wrote:O MAN! whoops. thanks for telling me... I used the default 9" for chamber length and didnt change it to 16". Would my performance increase much if I lengthened my chamber to 72" to get a real .8:1 ratio? I really want the most performance out of this thing as I can get without spending too much.

Blitz - by overkill, do you mean a lot more performance or so much energy that some would be wasted?


Sure, you'd get a performance increase by increasing your barrel length, because gases will have a chance to accelerate the projectile even more.

And a chamber fan would assist in mixing your fuel when you add it. It's a recipe for a great performer. :)
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Unread postAuthor: metallover » Thu Apr 24, 2008 11:08 pm

Awesome

I was hoping for a little more out of this thing...

Thanks for the help. I have one question - Where is the best place to get a 2.5" barrel and reducer? (I'll get the C:B right this time)
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Unread postAuthor: Blitz » Thu Apr 24, 2008 11:11 pm

metallover wrote:Awesome

I was hoping for a little more out of this thing...

Thanks for the help. I have one question - Where is the best place to get a 2.5" barrel and reducer? (I'll get the C:B right this time)


Upper left corner -- picture that says "BCARMS". You can get whatcha need there.
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Unread postAuthor: starman » Thu Apr 24, 2008 11:17 pm

I'm with Blitz, a fan makes a big difference...add it. Also, additional spark gaps incrementally add performance although the increments are less each time. Add a 3rd gap in the middle.

Lastly, consider using a basic 30-40 psi burst disk. This one feature alone can vastly make up for many other performance shortcomings. This is my chosen implementation, there are many other ways to do it.

Image

Don't fool with hybridizing this model. While I don't agree with BigBob that it will be suicide, especially if you keep it 2x or under, you should beef things up some before heading down that road. Try the basic burst disk... :)...you may find that's all the performance you really need. I'm already finding I can barely see the projectiles exit, much less where they end up.
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Unread postAuthor: metallover » Fri Apr 25, 2008 10:11 am

Is the 2.5"-2" the only reducer they have? That makes no sense to me. Why not have a 3" or 4" -2.5" reducer? plus I think the price is pretty high - its about 20 bucks total + the cost of the fittings you need to attach it to your chamber.

I'll so some searching on burst discs. I have a few questions that I will probably answer by searching a little, but here they are:

1. do they make it louder?
2. how much do they increase performance?
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Unread postAuthor: starman » Fri Apr 25, 2008 10:29 am

metallover wrote:Is the 2.5"-2" the only reducer they have? That makes no sense to me. Why not have a 3" or 4" -2.5" reducer? plus I think the price is pretty high - its about 20 bucks total + the cost of the fittings you need to attach it to your chamber.

I'll so some searching on burst discs. I have a few questions that I will probably answer by searching a little, but here they are:

1. do they make it louder?
2. how much do they increase performance?


1. YESSSS!!!
2. Depending on you overall configuration and ammo, up to 3X projectile velocity!!

Go to www.mcmaster.com and search for 4880K613, a 3" to 2.5" reducer bushing. They have anything you might want there.
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Unread postAuthor: metallover » Fri Apr 25, 2008 10:48 am

Well, the sound isnt exactly a positive thing :? - my town is crawling with cops and I usually shoot in my backyard into the state park or around campgrounds - :P
What I found so far is that a burst disc is a piece of material such as aluminum foil used to seal off the chamber from the barrel to increase preassure. the only thing I need to know is if it will work with threaded barrel removal system that I have, and what to make it out of. I thought a certain number of layers of aluminum foil. What do I need?
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Unread postAuthor: starman » Fri Apr 25, 2008 10:55 am

metallover wrote:Well, the sound isnt exactly a positive thing :? - my town is crawling with cops and I usually shoot in my backyard into the state park or around campgrounds - :P
What I found so far is that a burst disc is a piece of material such as aluminum foil used to seal off the chamber from the barrel to increase preassure. the only thing I need to know is if it will work with threaded barrel removal system that I have, and what to make it out of. I thought a certain number of layers of aluminum foil. What do I need?


My burst disk you see there is 2 layers of 2" masking tape on a male camlock...about 40 psi...assumes you've got a camlock breech system on your gun and barrels. Others do it with steel or PVC unions. Here's another method:

http://www.advancedspuds.com/burstdiskinst.htm

Other hybrid guys around here swear by multiple layers of aluminum foil for their hybrids. Be creative and careful.

Anything you do to improve performance will increase the associated noise. If you can't deal with that, maybe you should just stay with low powered guns.
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Unread postAuthor: metallover » Fri Apr 25, 2008 11:20 am

I think what i'll do is get my new barrel to get the C:B right, then if I want a more powerful shot every now and then, I'll add a burst disc. I dont want to get a bad relation with the cops :roll:

Thanks for all the help, are these the only things that will increase performance?

1. Chamber fan
2. Correct C:B
3. More sparks
4. Burst Disc
5. Fuel..... :idea:

What is the most powerful fuel I can use in my spud gun? I know mapp gas is another step up.
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Unread postAuthor: starman » Fri Apr 25, 2008 11:32 am

metallover wrote:What is the most powerful fuel I can use in my spud gun? I know mapp gas is another step up.


Stick with propane, MAPP is only marginally more powerful and 3X more expensive.
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