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Well, here it is (finally).
Fnord's piston hybrid, version 2.0 - aka. "Thunderstruck"
(sorry dialup users)
Prepare for reading.
Here are the basic stats. This stuff is described in detail farther down.
Chamber volume: 36 cubic inches (around 600 ml)
overall length: 28" sawed-off style
1" x 18" sawed-off
1" x 36" long-gun
.5 x 52" marble barrel
weight: 19 lbs (8.6 kg) with sawed-off barrel (!)
mix: up to 4.5x, though as long as ddt doesn't kick in, it could probably do 7x
ignition: flash capacitor+ignition coil setup.(single gap)
universal propane meter
Pimpin' purple propane tank
320 fps with 4oz lead balls, 700-800 ft-lbs
400-500 fps with vaporized potatoes, 700 ft-lbs
900+ fps with marbles. 330 ft-lbs (may have broken mach 1)
*velocity numbers calc'd with evbec.
This upgrade of my original piston-valved hybrid uses a more efficient, all-steel(ok, so the piston itself is aluminum) barrel sealing piston valve. I've also added an extra port on the end cap for attaching a pop-off valve for easier piston opening, or a high-flow blowgun for pneumatic use. The current pictures show a pressure gauge on this port.
I've reduced the somewhat bulky rectangular look of the last version to a more thin, riotgun-like look.
The entire gun (minus the barrel) can be broken down reasonably quickly to fit in a shoe box.
The propane meter has also been compacted considerably from before.
Finally, a propane meter that doesn't leak. Leaking propane has been sort of a curse for me, as there is no way I'm going to give anyone $20 for a $1 tank adaptor fitting. I eventually found an antique(literally) propane/oxy torch and salvaged the usable parts from it.
New, sturdy grip salvaged from a mig welder. After fighting the spaghetti monster for a while, I got the wiring reloaded into something actually designed for hv. The old hand grip was a spray can gun with a psu power switch hot glued into it. The bad thing about the old version was if you got your hand too close to the charging switch wires when firing, it would arc out of the trigger and into your hand.
Other stuff that hasn't changed:
For Ignition I used a camera flashboard and capacitor dumped into a (motorcycle?) ignition coil. The wiring and circuitry is contained within the handle, and the coil and battery are packed neatly above. All the external wiring is inside uber SciFi-looking wire jackets from and old car.
The output voltage is around 35KV (estimated from jump distance).
The chamber is black iron, and the fittings are all steel(one is brass though). The barrel is also galvanized steel and can be changed in seconds. I'm planning on a breech loading system soon.
For some reason, this gun has a very unique smell when fired. Something between burning wax/hydraulic oil/black iron enamel. The first time I shot it gave off a puff of smoke like a musket.
Even from the beginning, I never expected this gun to work, as I have never trusted my engineering skills with any task more complex than a ball-valve gun. It was constructed for around $40 usd, with most of that being for the large pipe fittings. The first parts were purchased around January (07) and the first real testing was only days ago (6-29-07).
This gun is more powerful than my 7-foot combustion. At 4x the muzzle energy is the same as a .44 magnum (firing a 240 gr SP).
The sound makes my ears ring, and the recoil is, to say the least, very noticeable. Being that it's a hip-shooter and not shoulder fired, it isn't so bad though.
Marbles give a loud rifle-like crack when fired, so I may be getting past the sound barrier. It's hard to say.
The damage shots I've done are fairly impressive. Bricks get shattered. Plywood gets pwned. Sheet metal is roughly equivalent to tissue paper.
After punching some numbers, I found that this gun is produces about 1/2-2/3 the energy of the mauler at a given mix.
It also seems very convenient not having to change burst disks after every shot. I would recommend anyone with access to a welder/drill press try making a piston valved hybrid over a traditional one. It's so much cooler.
Future upgrades/repairs: needs a more solid propane meter, needs a new rear pressure gauge (the current one couldn't handle the extreme working pressure).
I may also add a small bike pump underneath the chamber.
Last edited by Fnord on Sun Aug 14, 2011 5:14 pm, edited 2 times in total.
holy shat, that thing is awesome. How many Hybrids are portable or even close to handheld?
fnord..you were my hero when u built the first version..but now..(along with no name) you are my jesus!!
but seriously this looks totally better and more compact u do some good work!
4" piston valved cannon-half done..( i spilt my cement...)
Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
NICE!! That seems like a big improvement over the original design, not quite as rusty and ghetto looking, and the performance is quite impressive. It must be great not having to change and make burst disks, probably cuts down quite a bit on the reloading time.
Questions: How exactly does this new valve work? The old one used the pressure increase from the combustion to push up a spring loaded piston, but this one seems closer to a conventional barrel sealer.
Is the interior of the galvanised barrel rough enough to lose performance? I've heard that galvanised isn't the best barrel material.
Do you know what kind of ROF you can get from this design?
Overall, great job.
EDIT: I just found the thread explaining how your valve works.
Last edited by DYI on Thu Jul 19, 2007 7:49 pm, edited 1 time in total.
It is just DELICIOUS! Seriously, I love it! What's the deal with the x-ray of your foot? When I click the "delayed" link that's what comes up.
CO2 tank hybrid: Gotta fix the meter
Cane gun: Needs a pilot/fill setup
1.5" piston valve gun: Almost done
Beastly. How's that pop-off working for you? Does it actually open when the air behind the piston compresses?
Wow. looks like I'm going to have to answer a lot of questions tomorrow.
There is more stuff to come; I'm working on a diagram and 3d model, so the inner workings should be explained pretty well then.
I broke my foot(If you look closely you can see the bone sticking up on top), and the monster combustion is to big and heavy for me to work on, so it's delayed for a week or two.
wow, possibly my favorite hybrid cannon ever! has the pop-off valve behind the piston increased performance noticably?
searching for a modern day savior from another place,inclined toward charity,everyone's begging for an answer,without regard to validity,the searching never ends,it goes on and on for eternity
Sure people have built hybrids. They have built piston valved guns as well. Portable spudguns have been made as well.
...but for one person to combine them all in a compact package? Wow. Great work.
Well mine is.....
Fnord this is a very well constucted design NICE
Impressive. i can find an adjective to describe this so i made some up this gun is super ubertilary and jaffgeious
BTW you said it gives off 1/2 or 2/3 energy of the mauler. what makes the mauler so powerful?
"Those who are different change the world. Those who are the same keep it that way"
Nice man. When I saw your first I was amazed. But This is just crazy. I was wondering if it is completely portable or do you still use air compressor?
Very nice design, it kinda looks like a real grenade launcher. Even though it is not the first piston valved hybrid (GalFisk beat you to it), the valve is very well integrated into the design. Great job. A few questions:
1) Would it be possible to clean up the (somewhat cluttered) wiring at the rear of the launcher? This would drastically increase the aesthetic appeal.
2) Why did you epoxy the pressure gauge into the center of the meter pipe? A T fitting would be much more solid and look better.
3) When you disconnect the propane meter hose from the schrader valve and connect your air source, or when you disconnect your air source, because you do not have a ball valve between the schrader and the chamber, do you experience any fueling issues at higher mixes due to the lost propane/air pressure?
As a side note, I don't think you should take it past a 4x mix without using remote ignition.
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