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Aluminum combustion plans

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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Aluminum combustion plans

Unread postAuthor: Zach1188 » Sat Aug 22, 2009 12:08 pm

I am starting plans on an aluminum coaxial combustion cannon. It is designed similar to Ultimate Spud Gun's BL series spud cannons.

Here's the plans first:
Image
If you can't tell in the pic, the part of the wire that fits into the igniter is epoxied into place. Also on the front end of the chamber, there will be a horizontal handle. The gun will be held underarm, similar to Moonbogg's combra venom.

Now my questions:
1. I know little about metal plumbing parts. This plan is what I would do if I was building this out of PVC. Are there similar parts in aluminum?
2. Drilling a hole into the chamber of a PVC cannon can be dangerous. Is that true with metal cannons? The hole for the igniter wire will be sealed with epoxy.
3. I'm guessing aluminum is way overkill for a MAPP combustion cannon. If that is so, what are the chances of being seriously harmed by using acetylene? Or perhaps acetylene with a steel cannon? I know acetylene is dangerous and unstable, but is there any safe way to use it? I figured I would ask here and do some research before touching the stuff.
4. How well will the chamber fans vent the chamber in a coaxial? I just don't see it working very well.

Future Improvements:
1. Laser sight.
2. Pistol-grip from http://ultimatespudgun.com/
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Unread postAuthor: King_TaTer » Sat Aug 22, 2009 1:50 pm

Just a few things to consider...

A coaxial setup is one of the least efficient configurations for a combustion. Factors such as heat loss, flow constriction, and slower flame fronts start to harm performance.

I'm pretty sure there aren't fittings offered in aluminum similar to those of PVC but I could be mistaken. You can expect to pay over a thousand dollars easily if you were to use aluminum, not including machine shop costs. I suggest asking Moonbogg how much the Cobra Venom cost him. :lol:

You would be better off buying the Bl-520 from USG, In terms of price and performance. However If you were to make it a hybrid, aluminum would definitely be up to the task.

Also acetylene is pretty dangerous. I don't even like thinking about it in a steel cannon.

As far as your plans go...

I also don't think venting will be very efficient either as you will need an opening near the reducer to actually expel the CO2.

A grill igniter jumping four gaps is pretty impressive and probably won't happen every time unless you have very small gaps. I would use stun gun ignition for better consistency and you would be able to use a more comfortable trigger. You will also want to place your spark gaps along the length of the chamber to allow for faster chamber burnout, which means faster velocities.

If I think of anything else I'll edit. I hope I've helped. Good luck.
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Materials links:
<a href="http://www.discounthydraulichose.com/">Discount Hydraulic Hose</a>
<a href="http://www.buyfittingswholesale.com/#">Buy fittings wholesale</a>
<a href="http://www.flexpvc.com/">Flex PVC</a>
<a href="http://www.murrayequipment.com">MEI
</a>
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Unread postAuthor: Zach1188 » Sat Aug 22, 2009 2:30 pm

I see. Perhaps coaxial a coaxial configuration is inefficient, but after seeing the BL-520 I'm still impressed. Coax seems very convenient to me, and it appears that an over-under design would require some welding (rather than fittings) for it to look decent (like the Cobra Venom).

I don't know my metals, are there any cheaper alternatives? I know some good pressure rated PVC would be more than enough, but something about a metal spud cannon is very attractive to me. I would buy the BL-520, except for me, firing the cannon is only 1/2 the hobby. The other 1/2 is developing plans, construction, endless hardware store trips, etc... And I don't have the know-how yet to build a hybrid.

Ok so acetylene is out of the question, and I'm fine with that.

The current cannon I have uses a grill igniter, and jumps three 3mm gaps. I'm pretty sure I could get 4-5 gaps to work if the gaps were small. A stun gun is something I have seriously considered, but I'm not sure if I could make it real trigger-like. And it seems a bit iffy to use a stun gun in a solid metal cannon :lol:

So in other metals, are any of those fittings available?
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Unread postAuthor: chenslee » Sat Aug 22, 2009 2:37 pm

Zach! Your day has come. There ARE aluminum pipe fittings!

I hope you are rich. A 4" pipe cap costs $70

http://www.mcmaster.com/#aluminum-pipe-fittings-and-pipe/=3aw5pc
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Unread postAuthor: Zach1188 » Sat Aug 22, 2009 3:04 pm

Haha well chenslee, I'm more than willing to pay the price of a BL-520, but ONLY if that means I get to build it.

Thank you :)

Are there any cheaper alternatives to aluminum? I know steel is, but that would make this one heavy motherfucker. I will spend $1000 if I have to, but having $500 to spare would be quite nice.
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Unread postAuthor: jagerbond » Sat Aug 22, 2009 4:04 pm

Zach1188 wrote:Haha well chenslee, I'm more than willing to pay the price of a BL-520, but ONLY if that means I get to build it.


520 DIY <a href="http://ultimatespudgun.com/product_info.php?cPath=38&products_id=156">kits</a> are available for $660. The rings fit any schedule 40 material including Aluminum.

Starman just put one together a 417 from a kit, you could PM him about the build.
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Unread postAuthor: Willdebeers » Sat Aug 22, 2009 4:36 pm

jagerbond wrote:
Zach1188 wrote: are available for $660.


May I ask what your profit margin is on this product?
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Unread postAuthor: jagerbond » Sat Aug 22, 2009 5:01 pm

Willdebeers wrote:
jagerbond wrote:
Zach1188 wrote: are available for $660.


May I ask what your profit margin is on this product?


You can ask, but I probably won't post publicly. If you were thinking about starting your own SG business I can tell you there are more profitable sectors.

The assembled BL-520 consists of 38 machined parts, 26 of which are unique. We use robotic automation to help keep the costs down and I often feed the machines myself. My accountants tell me I'm crazy. So do the lawyers for that matter :D
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Unread postAuthor: Hotwired » Sat Aug 22, 2009 5:28 pm

Willdebeers wrote:
jagerbond wrote:
Zach1188 wrote: are available for $660.


May I ask what your profit margin is on this product?


You can ask, but I probably won't post publicly. If you were thinking about starting your own SG business I can tell you there are more profitable sectors.


Starting a spudgun business in the UK and advertising it would be very tricky anyway. Something about the law round here.

Machining services based on a forum and private sales are about as close as you could bring it. Unless of course you get into the special effects cannon business for a legit side to it :)
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Unread postAuthor: theBOOM » Sat Aug 22, 2009 7:15 pm

Not to be a party pooper for anyone but Moonbogg is gonna be selling the cobra venom and the cobra viper (I think that is what the name is) kits for 400 or so dollars(THIS IS AN ESTIMATE), full aluminum construction :) with hybrid capabilities 8) :P
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Unread postAuthor: USGF » Sun Aug 23, 2009 12:18 am

theBOOM wrote:Not to be a party pooper for anyone but Moonbogg is gonna be selling the cobra venom and the cobra viper (I think that is what the name is) kits for 400 or so dollars(THIS IS AN ESTIMATE), full aluminum construction :) with hybrid capabilities 8) :P


Boom, True I am biased towards USG ... I am USGF after all. Thats Factory :)

Moonbogg's offering is a fabricated product mostly, not CNC machined. A great product but anytime apples and oranges are compared you gotta point it out.

I read with interest others comments on how Mike builds things or how much profit there is. It's a real hard thing to quantify. For instance, you will buy 500 lbs of aluminum billet to carve parts, a couple of thousand dollars worth of tooling, pins, screws, anodizing services etc. etc. You build and sell a bunch of stuff and yes there is little to no cash in the bank. BUT, you still have a small pile of parts, a couple boxes of screws and a few endmills that were not snapped off. How do you place a value on that?

The potential / possibility of increased sales is what keeps us going, not huge sales that keep the machines running 24/7. We have other products that keep the shop very busy. We love the USG product line and find many people do too. We are using machines to do things most spudders can only dream of. We don't apologize for the prices we post . This is what it will take to keep us building dreams for our customers.

As I have mentioned before, more cool stuff IS in the pipeline.

USGF
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Unread postAuthor: inonickname » Sun Aug 23, 2009 12:32 am

I wouldn't think so, it cost him a hell of a lot more to get close to completion than $400.

I won't bother talking about how bloody expensive aluminum would be for this, but about acetylene:
-Unstable, forming explosive compounds with materials like copper (yes, your wires, spark strips etc. ESPECIALLY ones that are coated in PVC insulation.
-Rapid burn rate etc, but not a huge problem in such a cannon.
-Liable to explode if stored under 20+ psi (must be dissolved in acetone), so no hybrid possibilities. (a low mix mapp hybrid will perform better)
-If obtained from calcium carbide extremely toxic impurities are common, such as phosphine and arsine.
-Mild asphyxiant (as a lot of things are)
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Unread postAuthor: starman » Sun Aug 23, 2009 12:38 am

jagerbond wrote:
Zach1188 wrote:Haha well chenslee, I'm more than willing to pay the price of a BL-520, but ONLY if that means I get to build it.


520 DIY <a href="http://ultimatespudgun.com/product_info.php?cPath=38&products_id=156">kits</a> are available for $660. The rings fit any schedule 40 material including Aluminum.

Starman just put one together a 417 from a kit, you could PM him about the build.


Building is very doable...basically your biggest challenge will be rounding up the pressure rated PVC parts and how ever much effort you care to put into your paint and finish job.
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Unread postAuthor: POLAND_SPUD » Sun Aug 23, 2009 9:05 am

who said you need to use one material ?? use aluminium pipes and standard malleable iron fittings... taht should cut costs and mass at the same time
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Unread postAuthor: Zach1188 » Sun Aug 23, 2009 3:53 pm

POLAND_SPUD wrote:who said you need to use one material ?? use aluminium pipes and standard malleable iron fittings... taht should cut costs and mass at the same time

Very, very good point. The fittings are where it gets real expensive.

Darker fittings and lighter pipe will also look better.
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