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New Combustion Launcher

Built a combustion 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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New Combustion Launcher

Unread postAuthor: Deadeye » Fri Jul 18, 2008 12:23 pm

Gun Name: Hammer-time
Design: Basic Over/Under Advanced combustion with a few mods.
Chamber: 18” of 4” 280 PSI Sch. 40 (Double Sleeved) + 4” 90 & 4”-3” Street 90 = (5200 ML Interior)

Barrels: (1) 62” Long 2” Sch.40, (C:B 1.5:1) (2) 58” Long double sleeved 2” golf ball barrel 1.7” ID, (C:B 2.4:1)
(3) 96” 1.5” Sch. 40 (C:B 1.6:1)

Fuel: Off-Board Propane meter w/ regulator – On-Board portable pre-measured Fuel cells (7.5” of ¾” PVC) Custom triple diaphragm fuel cell loader with quick connects

Ignition: Piezo BBQ Igniter – Dual Stainless steel multi-point spark arresters wired in series and spaced evenly in chamber

Electrical: 24VDC Chamber Fan, Custom On-Board PVC Battery pack (3-9 VDC Batts.), Custom Off-Board Large Capacity Power Supply (4-6 VDC Batts.) Curly cord and plug for easy switching.

Accessories: 2” Adapted Threaded Barrels, 2” Ball Valve for Venting, Customized Safety trigger/handle, & Barrel support

Esthetics: Tri-Color Paint Job - Rust-Oleum Specialty Hammered Paint For Plastic - Paint Link (Black Combustion chamber, Silver Accessories, Dark Bronze Barrels)

Props: After much web research on ideas, innovations, and what-not’s (to do), Spudfiles had by far the most posts, pix, and relevant chat. Burnt Latke for C:B ratio & Fueling made easy. Can’t forget extra how to’s, technical data at Advancedspuds. Credit for my fuel system goes to homedepotpro. I knew I wanted propane but I didn’t want that clunky tank & meter on board, so I was going to have the metering device & tank as a kind of loader, until I saw HD Pro’s innovative setup.

C:B Ratio: I realize some of the barrel lengths are less than ideal as per the prevailing wisdom. I was trying to balance performance against portability, and also wanted to try and use what I had. I plan to pick up some 8 footers and do some experimentation. From what I can tell there is a big sweet spot between .5:1 – 1.5:1, but then the velocity and distance drops off drastically on either side of that range.

GB Barrel: My Golf Ball barrel has the biggest lack of volume problem, but sleeving those 2” Sch 40’s into one another was a bear, I won’t be doing that again, especially not a longer one. For those who haven’t done this – You have to cut a 7/8-1” slit out of the inside pipe then squeeze the gap shut and smash it into the outer pipe. Once you cut the inside pipe it loses its cylindrical integrity so becomes oval. This oval force along with the pipe trying to spread apart creates two different forces of friction which increases exponentially as more length of pipe is in contact with one another. If I do anything I will buck up for the SDR 21 (only available in 20’ lengths @ plumbing supply) and sleeve it into the sch 40 2”.

Mishap: In my anxious paranoia of getting a perfect seal on the combustion chamber I failed to leave myself a way back in, which was quickly remedied when the fan started making a weird noise and then ultimately quit working. The chamber is comprised of high pressure pipe with couplers over the top for a complete double wall structure. To replace the fan, I had to cut away the last coupler & glue without disturbing the last piece of pipe under it, so I could then glue the replacement coupler back over the pipe. Needless to say I added a threaded cleanout body at the end before the reducer & ball valve, which was much incentivized by the surgical precision required to re-enter the chamber. The fan it turns out was corrupted by my sloppy epoxy job (per the autopsy). The fan body was mostly cut away to allow it to fit perfectly in the round pipe, as a result, when I was gluing the fan in the chamber, I got some on one of the blades. This little bit of friction eventually took its toll on the motor.

History: This was technically my second gun, the first being nearly 15-years ago which was a standard in-line spray & pray, with a lantern lighter & a thirst for starting fluid. I believe it had an eating disorder as it would throw-up potatoes about 200 yards.
Haven’t really shot this one much yet, 10 or so shots in the shop with a ball of duct tape to tweak the fuel levels, one of the errant shots blew a hole through a piece of 1/4” plywood. I shot two golf balls; one of which went literally out of sight, the other much further than I can hit one.

Need to score a safe place to shoot and I’ll get some damage shots, and try and do some distance measurements. Also, as said, I want to check out barrel length performance next.
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Accessories: Fuel Cells, Loader, & 2nd Power Supply

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Unread postAuthor: brogdenlaxmiddie » Fri Jul 18, 2008 12:53 pm

Awsome cannon! Especially for your second. Keep up the good work and I look forward to more of your cannons!
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Unread postAuthor: psycix » Fri Jul 18, 2008 1:15 pm

Nicely done!

The way you mounted your igniter is very good! The button is protected against accidental presses.
Seems like this gun has almost everything a combustion gun needs.
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Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

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Unread postAuthor: starman » Sat Jul 19, 2008 10:04 am

Oh man, this slipped by too quickly yesterday. Really clean build here Deadeye. You utilized HomeDepotPro's syringe system as well I see... :wink: I like your multi propane syringe manifold...I may have to incorporate that myself.

I like your protected ignitor build-out there...and an external hoss 24v fan power mains...that baby will definitely be chopping up some fuel/air mixture and being lantern batteries, could just last forever... :) Also, the On-Board PVC Battery pack is a unique and clever design and it looks like those battery holders were built to fit in there...perfectly! Is there any way you can show us your spark gap setup?

Your barrel support is solid and you've got a very beefy air inlet ball valve. I think my only suggestion would be to turn the fuel injection quick coupler back to the 4 or 5 o'clock position for easier syringe access from the right side.

Great build, excellent write-up and solid cannon!

Oh and...if you want to sleeve an SDR 21 barrel, you'll want to do it with 2" sched 80. It will be a little too loose in sched 40. BTW, I highly recommend the whole SDR 21 sleeved in sched 80 GB barrel thing...big improvement over the slit 2" inside a 2" sleeve...been there, done it myself.
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Unread postAuthor: Deadeye » Sat Jul 19, 2008 1:57 pm

Thanks for the kind eval.

Spark: - I might have oversold this in the description, which I suspect peeked your interest. In reality it is actually the one that came with the igniter I bought. Most were junk this one was a little more expensive because it had side burner hardware too, which I didn't use, but it was the only one that had this nifty multi-gap operation, so I had to buy two.

At the bottom is a pic of one of the spark arresters installed - They are mounted at each end of a piece of 1/2" pipe sliced in 1/2 and epoxied to the chamber wall, and press-fit with those spreader thingy's- The cone of pipe also protects most of the wiring.
Also below is the ad photo which shows better angle. As you can see there are 6 stainless prongs which the spark jumps across - so in theory 6X more sparks before they start to degrade or carbon over.

I looked at several custom alternatives but kept coming back to this because of reliability and longevity, figuring the manufacturer's R&D people are way smarter than anything I could come up with.

Lastly on the spark topic, below is a pic/ad of one they call a "safety Igniter" which I was originally looking at, it would be a simple install for a single spark operation which I thought I would mention for those having trouble with spark gaps. I haven't seen this elsewhere on any of the spud sites, so this maybe worthy of it's own mention in an easier to find location within the site to help out those looking -
Just goggle the name - it's pretty reasonable at around 12 bucks

I originally had a 12vdc fan with 8-AA's sleeved into a piece of 1/2" and wired like a flash lite with a switch at one end and a female plug at the other. I wasn't thrilled with the fan power, so when I had to replace it I found a slightly smaller one @ 24VDC which pulled less amps and was 2-3 times more powerful. I wasn't wild about the new voltage and the battery pack redo but boy did it turn out to be worth it for this big chamber.

The single coolest thing about this gun is the fuel cells (sounds more army than syringe) ha! and the credit goes big time to Homedepotpro. I think you will be seeing way more of this setup.
The Tri-loader idea actually originated not for loading cells but for loading the gun (to have on-board standby fuel) at that point to make it work I had to move the connector per your suggestion. I moved it back more for symmetry than anything else. (It's threaded and taped - not epoxied so I can move it around if I want) so good catch - it actually loads a single "cell" pretty easy in it's current location - it's a two-hand operation either way.
You'll note that I had to go from 1/2" to 3/4" (shorter) pipe to facilitate this in-line location. I originally had it mounted on the threaded adapter just before the ball valve (thinking that if there is a weak point I wanted it to be further away beyond the chamber) - Also this was behind the fan so I reasoned that maybe this would help get a better mix - not sure if that really did anything - just a thought. Feel better with the current double wall install.

Thanks again for the suggestions, always welcomed
I get a little wordy & run on in the write up and this response because when I was doing my research for ideas, that is what I found most useful.
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Spark Arrester Installed
Arrester 1gif.jpg
My Spark Arrester Ad - (bottom right)
Arrester 1gif.jpg (10.56 KiB) Viewed 2333 times
BBQ Safety Igniter
bbqsafetyigniter.jpg (27.69 KiB) Viewed 2333 times

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