Posted: 06/23/2010 3:17 AM Post subject: WIP: 1.5" Porting Handheld Piston Hybrid (DAMAGE VIDS)
Hybridian
Joined: 18 Oct 2006 Posts: 2372 295.89 Spud Bux
This cannon went from an idea to design to construction in about a week. The goal was to build a hybrid launcher that is powerful, requires no cumbersome loading process (Burst disks etc.), and capable of being shoulder fired. While it's still somewhat of a work in progress, this launcher hits on that formula.
EDIT 7/2/2010: The launcher has gone through several revisions since the original post. I'll detail each one in descending order.
Updated design as of 7/2/2010
Specifications
Launcher Configuration: Over/Under
Chamber: Galvanized steel/malleable iron construction, 2.067" inside diameter, ~25" length, 85in3 volume
Barrel: Solid core ABS construction, 1.6" inside diameter, 72" length, 145in3 volume
Valve: 1.6" porting high flow barrel sealing piston valve w/lightweight ABS piston and spool valve pilot venting
Loading: 2" Aluminum cam-lock fittings
Fueling Setup: Volumetric meter w/integrated air fill port (Air through meter design)
Fuel: Bernzomatic 16.9oz Propylene cylinder
Ignition: Electronic BBQ igniter, homemade 1/8" NPT spark plug
Venting: Pressurized air exhausting system w/1.25" chamber ball valve
Mixes attempted: 4x, 5x; plan to use 6x in the future
Estimated muzzle energy: At 5x: 2800ft/lbs for a 50 gram frozen potato slug, 2950ft/lbs for a 75 gram marble shotgun round, 3050ft/lbs for a 100 gram APFSDS round, 3200ft/lbs for a 160 gram D cell slug.
Estimated muzzle velocity: 1280fps (supersonic) for a 50 gram frozen potato slug, 1080fps for a 75 gram marble shotgun round, 950fps for a 100 gram APFSDS round, 760fps for a 160 gram D cell slug.
Pictures
Launcher overview:
Chamber:
Inside the valve:
Crappy valve diagram:
Piston and spool valve:
Updated piston sealing face (5/16" thick rubber):
Videos
Firing a ~75g (Includes wadding) marble buckshot shell at a watermellon:
6' barrel was added, as well as a barrel support and larger chamber fan. The ignition trigger was also repositioned, but the valve design remains the same as the original.
Original design as of 6/23/2010
The original design used a pop-off valve on the pilot chamber, and a thin, soft butyl rubber piston sealing face. This setup proved to be problematic, as faster valve opening, longer valve dwell time, and a more durable sealing face were required.
Additionally, a fan was used in an attempt to vent the chamber more rapidly. It proved to be less effective than my original pressurized vent system.
Thanks for looking.
Last edited by SpudBlaster15 on 07/04/2010 1:48 AM; edited 5 times in total
Amazing build, one of the best made piston hybrids I've seen for a while, you included alot of unique things into this cannon.
The only thing that I see uncomfortable are all the fittings in the back resembling a stock of some sort, I'm sure you could cut down on all the fittings and make a better, custome, stock for the launcher.
Very nice build again, good job, and I'll be awaiting damage pics from this monster
great work there SpudBlaster, should be a nice hole puncher.
i like that way you mounted the fan.
only thing i can think if is a barrel support and BRING ON THE DAMAGE
The only thing that I see uncomfortable are all the fittings in the back resembling a stock of some sort, I'm sure you could cut down on all the fittings and make a better, custome, stock for the launcher.
I use this stock design on all my hybrid cannons, and with decent padding on the rear, it works great. By integrating the meter into the stock, you kill two birds with one stone.
theBOOM wrote:
PS - where did you get the small MAPP tank?
It's a standard 480g Bernzomatic Propylene tank.
-_- wrote:
only thing i can think if is a barrel support
I might build a barrel support when I add a longer barrel, but for now, this one simply isn't heavy enough to necessitate support.
ramses wrote:
What's your barrel made of? Do you have a diagram of your valve?
The barrel is ABS, and I'll post a diagram of the valve later.
I finally took some pictures of the valve and its components.
The piston is an assortment of 1.25" ABS fittings and pipe, with double o-rings to form the seal between the pilot chamber and the main chamber. Butyl rubber sealing face is bolted on.
The piston slides inside a 2" seamless galvanized steel pipe, and seals against a 1.5" pipe. The length of the 1.5" pipe and the travel of the piston have been optimized to allow for maximum flow into the barrel port.
A little silicone grease on the o-rings, and it all slides together and seals nicely.
I forgot to take a picture of the bumper when I had the valve open, but it's basically a large rubber doughnut that sits inside the endcap and extends slightly into the pipe.
It may seem surprising, but that really is all there is to it; the elusive hybrid piston valve is not much more complex than a standard pneumatic barrel sealer. Makes a person wonder why there are only a handful in existence.
God! This is a great gun. It's clean, acceptable ROF and power all in one small compact package! It does make me wonder why everyone with "small" hybrids is using burst disk's..
A union is a bigger pain in the arse then building a piston valve I can imagine..
looks great! is the piston sealing on the full od of the 1.5inch pipe or was that reduced slightly? if it wasnt reduced you will get some nice opening pressures without having a increased pilot area pressure!
Excellent piston. Please keep us posted on the durability of that one. I know the ABS is tough since I tested it in one of my cannons, but your test is much more extreme. The forces to crush it, stretch it, slam it, etc must be intense for use in a hybrid.
I wonder if the rear pipe can be extend somehow into the T so a shorter lighter piston can be used. It's performance may approach that of a burst disk.
The overall build is excellent. I was wondering about the amount of exposed threads and a total lack of marks from a pipe wrench. Is this simply hand tightened?
If I can find 1.25 ABS fittings, I may look into replacing the PVC piston in my ABS cannon so it is all ABS. It may be an easy way to get floating o rings on it.
God! This is a great gun. It's clean, acceptable ROF and power all in one small compact package! It does make me wonder why everyone with "small" hybrids is using burst disk's..
Thanks SpudFarm. I think most people use burst disks because they are simpler, easier to setup, and the "tried and true" method. Hybrid piston valves are still somewhat of an experimental concept, and with only 3 or 4 in existence, there's no standard set of design parameters which people can base their valves on. I'm hoping that by showing the internals of my valve, I'll bring understanding to a wider audience of spudders. Hopefully we'll see more piston hybrids in the future.
c11man wrote:
looks great! is the piston sealing on the full od of the 1.5inch pipe or was that reduced slightly? if it wasnt reduced you will get some nice opening pressures without having a increased pilot area pressure!
Yes, it seals on the full OD, which gives me a surface area ratio of approximately 10:1. This is convenient. 50PSIG pilot pressure = 500PSIG opening pressure.
Technician1002 wrote:
Excellent piston. Please keep us posted on the durability of that one. I know the ABS is tough since I tested it in one of my cannons, but your test is much more extreme. The forces to crush it, stretch it, slam it, etc must be intense for use in a hybrid.
I'll be sure to keep you posted. ABS is indeed a very tough material, but other than my hybrid barrel (Which is holding up well), this may be the highest stress application I've used it in. My largest concern is the impact with the rear of the pilot chamber during opening. The energy absorption and force reduction created by the rubber bumper should prevent damage.
Technician1002 wrote:
I wonder if the rear pipe can be extend somehow into the T so a shorter lighter piston can be used. It's performance may approach that of a burst disk.
I thought about that a lot, but with these fittings it simply isn't practical. The piston is hollow, so a reduction in length wouldn't save much mass anyway. It's pretty lightweight as it is.
Technician1002 wrote:
The overall build is excellent. I was wondering about the amount of exposed threads and a total lack of marks from a pipe wrench. Is this simply hand tightened?
I three-point the wrenches and/or use leverage from existing assemblies to tighten the components, so there are few visible pipe wrench marks. They are about as tight as you can get with a pair of 18" pipe wrenches. The exposed threads are a result of the manufacturer cutting a large excess into the male components.
God! This is a great gun. It's clean, acceptable ROF and power all in one small compact package! It does make me wonder why everyone with "small" hybrids is using burst disk's..
Thanks SpudFarm. I think most people use burst disks because they are simpler, easier to setup, and the "tried and true" method. Hybrid piston valves are still somewhat of an experimental concept, and with only 3 or 4 in existence, there's no standard set of design parameters which people can base their valves on. I'm hoping that by showing the internals of my valve, I'll bring understanding to a wider audience of spudders. Hopefully we'll see more piston hybrids in the future.
I am simply hoping to see more hybrids on this page. They are a bigger challenge then the simpler pneumatics and combustions.
Atleast I would like to build a piston hybrid now, I know "Galfisk" is working on his after abour three years of down time. His valve and metering system is something different!
A propane tank premixed with fuel/air and a marble hybrid would be so much fun! To bad I am to scared to use premixed chambers for fueling.
i like those opening pressures! the next thing i would worry about is sealing face being blown out during firing
Hopefully that won't be an issue with the large washer and bolt/nut assembly. If the sealing face does somehow manage to fail, it's back to the drawing board on that one.
Quote:
and if i may ask what is your fueling procces going to be?
Load ammo
Pressurize the pilot to seat the piston
Meter and inject fuel
Connect the air pump and pressurize the chamber
Fire
Open the chamber ball valve and turn on the fan (With the pop off valve in place the piston should stay open, allowing the exhaust gases to flow out the barrel)
Turn off the fan and close the ball valve
Repeat
SpudFarm wrote:
I am simply hoping to see more hybrids on this page. They are a bigger challenge then the simpler pneumatics and combustions.
Therein lies the problem. If we want to see more hybrids posted, we need a way to make them appear less intimidating and more within the capabilities of the average spudder. I suppose this complicated looking mass of pipes doesn't really help, but I hope the valve pictures do.
Quote:
Atleast I would like to build a piston hybrid now
Go for it. The more we research and develop it, the more the concept will grow.
Quote:
I know "Galfisk" is working on his after abour three years of down time. His valve and metering system is something different!
Can't wait to see it. Galfisk is a creative guy and I'm sure he's come up with something extraordinary.
Quote:
A propane tank premixed with fuel/air and a marble hybrid would be so much fun! To bad I am to scared to use premixed chambers for fueling.
I think premixed air/fuel is too dangerous to use, especially if you plan to store it at higher pressures. One electrostatic discharge during fueling, and you have a rather energetic pipe bomb on your hands.
Quote:
Good job once again!
Thanks, and keep up your high speed launch videos.
Last edited by SpudBlaster15 on 06/24/2010 14:07 PM; edited 1 time in total
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It may be an easy way to get floating o rings on it.