Posted: 09/23/2009 6:35 AM Post subject: MMSIPH-10 MK 1 UPDATE: Nearly pierced 1/2" Steel!!
Major General
Joined: 29 May 2008 Posts: 1519 3981.54 Spud Bux
MMSIPH-10 MK 1(Manometrically Metered Pilot Isolated Piston Hybrid )
Chamber: 2" SCH 40 galvanized, 12" long, plus a lot of fittings.
Barrels: .5" copper 10' long, in 5' segments. 2" EMT conduit 10' long, also in 5' segments
Valve: .75", .5" porting, O-ringed piston. O-Rings allow pilot to be filled to a different pressure than the chamber, allowing opening pressure to be adjusted Independently from mix #.The dead space is filled with caulk, so the air spring has an acceptable compression ratio.
Piston: Machined aluminum, 2 O-Rings. Re-enforced rubber sealing face
Mix: 2x-10x (limited by compressor)
Ignition: Camera flash/ Iggy coil. The trigger electrodes can be hooked up to any extension cord, allowing me to be 250 feet away when I fire the cannon. The most I ever use is 50 feet.
Spark plug: Drilled out bushing/ filed down automotive spark plug JB-Welded together.
Meter: modular quick connect, manometric.
fuel meter:
air meter:
nozzle: homemade venturi designed to aid in fuel mixing, as I was having problems with this earlier. IIRC, the holes are .02" diameter
[img]http://i608.photobucket.com/albums/tt165/roflchopter11/potato%20g un/3026cropped.jpg
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nozzle before insertion into tee
Noise level: Surprisingly quiet when a paper towel wad is used with 10' barrel. Multiple echoes around my rural neighborhood when shooting blanks. Absolutely deafening in my basement at 2x with no barrel.
-2" piston valve, magnesium alloy for 40% less weight, if I can find some rod for less than $80 shipped. I may melt scrap, but melting several pounds of flammable metal that will evolve hydrogen and steam if it contacts water seems rather unsafe. I also lack a suitable inert gas cylinder.
-Barrel supports!!!
Innovative design:
Ignition system that uses extension cords to extend range, without buying extra wire. (currently too ghetto to include pictures of)
Pilot area sealed from chamber to allow opening pressure to be controlled separately from mix number
Nozzles to aid in fuel mixing (see above)
Other notes: flies seem to love the galvanized chamber
Last edited by ramses on 05/30/2010 19:29 PM; edited 1 time in total
Do you take requests? How fast can you launch a miniature marshmallow? If you can punch a hole in a major appliance with a marshmallow, I'll be very impressed. ( I'm already very impressed. ) That battery splat is much worse than mine.
Also, I think the marshmallow would simply catch fire. Would that qualify as an incendiary projectile for the rules. It would at the very least gum up the barrel (which already smells like some kind of plastic burning).
That said, I'll see what I can do. We may be getting rid of a 15 year old computer.
Edit: yes, rag. HGDT puts it at around 650fps, but I have to leak some air out or it won't ignite for some reason.
How exactly did this go 8 months without receiving a single comment? This is a very impressive launcher, and you even have high speed launch videos.
It amazes me how so many PVC sprinkler valve pneumatics can get 5+ pages of replies, yet a well built piston hybrid gets none. I'm kicking this up to the top of the forum in hopes that more people will see it.
I do have a question: Have you had any issues with the sealing face becoming damaged when the air spring expands and slams the piston into its seat? Before I changed my setup, I had this issue on my hybrid launcher, and ended up experiencing a complete structural failure of the rubber seal.
White goods, washing machine, refrigerator, etc. Pics below from the marshmallow cannon. (Not a Hybrid)
I used to know the mass. I took the weight of a bag of mini marshmallows and then counted them. Divided the weight by the quantity to find the weight if each. I don't remember the mass.
Golf ball dent.JPG
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Dent in the lid and the projectile
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Conduit hole.JPG
Description:
The edge of a piece of 1 inch electrical conduit makes a nice hole.
How exactly did this go 8 months without receiving a single comment? This is a very impressive launcher, and you even have high speed launch videos.
It amazes me how so many PVC sprinkler valve pneumatics can get 5+ pages of replies, yet a well built piston hybrid gets none. I'm kicking this up to the top of the forum in hopes that more people will see it.
I do have a question: Have you had any issues with the sealing face becoming damaged when the air spring expands and slams the piston into its seat? Before I changed my setup, I had this issue on my hybrid launcher, and ended up experiencing a complete structural failure of the rubber seal.
First of all: Thank you! Although I wouldn't consider this well-built. It has a number of issues I need to correct.
I have had no issues with the sealing face, but I am using a re-enforced rubber with some kind of fiber stuff inside. It's probably at least .2" thick, and is a PITA to cut.
@ Tech - Would a stainless steel toaster count? it's fairly well built (well excpt the switches, which is why I took it apart in the first place .)
I know it's probably a "minor appliance," but...
this was posted a good while ago, but I dont think the creator would mind a bump:
In a hybrid like your's (the pilot not exhausted) vs one like SB15's or McCrowley's (vented pilot at ignition), do you think you're losing a fair amount of power that vented designs get from a better valve?
Joined: 15 Mar 2007 Posts: 18061 32519.23 Spud Bux
Lockednloaded wrote:
In a hybrid like your's (the pilot not exhausted) vs one like SB15's or McCrowley's (vented pilot at ignition), do you think you're losing a fair amount of power that vented designs get from a better valve?
Because of the complete disparity between chamber and pilot pressures, I doubt this is really the case to a noticeable degree.
I don't think so, but I could test in a comparison with a burst disk screwed between the barrel and chamber.
The air is only exerting 2*pilot pressure*area force on the piston at half its travel. So if I fill both to 150 PSI, or roughly 11x, there's 300 PSI in the pilot, and 1100 (roughly) acting on the front.
But at something like 9/10 travel, there's a 3000 PSI acting on the piston, which would act in lieu of a (good) bumper. That was the main reason for the lack of an exhaust valve. I am considering a 1.5" porting valve upgrade, and at that point, I may exhaust the pilot. though this would reduce rate of fire.
It is worth noting that this was built when piston hybrids were less understood, so one of my main goals was to make sure the no fuel/air mix could enter the pilot. This could either ignite, and prevent the valve opening, or diesel and cause a bunch of other problems.
I don't think so, but I could test in a comparison with a burst disk screwed between the barrel and chamber.
The air is only exerting 2*pilot pressure*area force on the piston at half its travel. So if I fill both to 150 PSI, or roughly 11x, there's 300 PSI in the pilot, and 1100 (roughly) acting on the front.
But at something like 9/10 travel, there's a 3000 PSI acting on the piston, which would act in lieu of a (good) bumper. That was the main reason for the lack of an exhaust valve. I am considering a 1.5" porting valve upgrade, and at that point, I may exhaust the pilot. though this would reduce rate of fire.
It is worth noting that this was built when piston hybrids were less understood, so one of my main goals was to make sure the no fuel/air mix could enter the pilot. This could either ignite, and prevent the valve opening, or diesel and cause a bunch of other problems.
That's what I was thinking, if the pressure holding the valve shut is so substantially larger then the opening pressure, there shouldn't be problems. I just wish I had some numbers to back this assumption up
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) That battery splat is much worse than mine.
