SCTBDCv1.5 - 450psi 50mm steel cannon (updated with new vid)
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elitesniper
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DYI you do like burst disk alot dont you?
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SpudBlaster15
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Last edited by SpudBlaster15 on Wed Jul 14, 2021 6:11 pm, edited 1 time in total.
Well, the neighbours are either indifferent, or actually like it. Kind of strange, but it isn't that loud because of its high efficiency.
SB15, I'm assuming that this must either be using 10x+ mixes, or be impractically long, because that's almost half the muzzle energy of FEAR.
But I'm building a 20x, 2" bore hybrid in the summer, so that should be pretty impressive too.
But my next main project is the massive backstop I'm building for the SCTBDC so I can safely fire it in my backyard. Probably 1/2" plate steel of something, with 4x4s for supports. That, and the recoil absorbing stand for the launcher, to avoid another mishap like yesterday's.
SB15, I'm assuming that this must either be using 10x+ mixes, or be impractically long, because that's almost half the muzzle energy of FEAR.
But I'm building a 20x, 2" bore hybrid in the summer, so that should be pretty impressive too.
But my next main project is the massive backstop I'm building for the SCTBDC so I can safely fire it in my backyard. Probably 1/2" plate steel of something, with 4x4s for supports. That, and the recoil absorbing stand for the launcher, to avoid another mishap like yesterday's.
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SpudBlaster15
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Last edited by SpudBlaster15 on Wed Jul 14, 2021 6:11 pm, edited 1 time in total.
Where do you live Spudblaster?
My plan is a 3" x 24" steel chamber, and a 2" copper barrel, with 10x - 20x mixes. EVBEC forecasts a hell of a lot of muzzle energy, about half what FEAR generates.
My plan is a 3" x 24" steel chamber, and a 2" copper barrel, with 10x - 20x mixes. EVBEC forecasts a hell of a lot of muzzle energy, about half what FEAR generates.
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mark.f
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DYI, have you considered bungees and a sliding platform for a stand? I'm not talking just one or two cords, either. Depending on your max projectile weight, several bungee cords and a platform allowed to slide "freely", (minus the friction from wood on wood), backwards, but not side to side, should allow enough flex to avoid future failures of your stand due to "quick" loads. Your stand will still have to be pretty beefy, however, if you plan to fire heavy rounds. Perhaps you could try reinforcement with 1/2" or 3/4" threaded rod? Or maybe rebar if you've got the tools to work with it...
SpudBlaster, do you think a larger (3") chamber would survive many 8x mixes? I know you and others have lit off these kinds of mixes in smaller chambers, like 1-1/2" or 1-1/4" SCH-40 steel, but with the larger pipe, I think your "safe" pressure would be reduced. I definitely forsee some sort of remote ignition in your future.
Probably the RC servo again, no? I've just been using a pull-string tied off to the toggle switch on my new ignition box, playing around with my old hybrid.
SpudBlaster, do you think a larger (3") chamber would survive many 8x mixes? I know you and others have lit off these kinds of mixes in smaller chambers, like 1-1/2" or 1-1/4" SCH-40 steel, but with the larger pipe, I think your "safe" pressure would be reduced. I definitely forsee some sort of remote ignition in your future.
Probably the RC servo again, no? I've just been using a pull-string tied off to the toggle switch on my new ignition box, playing around with my old hybrid.I'd be using SCH 160 steel in my design. The purpose of wider chambers is to reduce the chance of DDT at higher mixes (or at least that's the purpose of the wider chamber on my design).
My plan was to make a stand out of 4x4s, and instead of a single support in the middle of the carriage, I would use one on either side. Then I would make a rectangular-prism shaped base, with 4 wheels, so that the whole thing would slide backwards, and use chains and various clamps to secure the cannon to the stand.
My plan was to make a stand out of 4x4s, and instead of a single support in the middle of the carriage, I would use one on either side. Then I would make a rectangular-prism shaped base, with 4 wheels, so that the whole thing would slide backwards, and use chains and various clamps to secure the cannon to the stand.
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SpudBlaster15
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Last edited by SpudBlaster15 on Wed Jul 14, 2021 6:11 pm, edited 2 times in total.
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mark.f
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You don't have the option to export GGDT files in a format convenient for this forum, but most people just take screen-shots. This is from the steel ice-slug shot...DYI wrote: If you can show me how to post GGDT files, I'll show you the GGDT output for it. I don't actually have any close up pictures of the valve area.
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For ammo you could take 2 1 1/4" end caps and make a little section of pipe with them at the ends and then fill it with concrete, Pykrete, or something to that extent and shoot that. Since the 1 1/4" end caps give a good seal in 2" pipe.
Mark, that GGDT is close, but not quite;
The pressure used was 470, not 450, the dead space is more like 10+ cubic inches, and the flow coefficient of a burst disk valve is at least 50, possibly 55.
The most significant problems however, are the bore and the valve:
I used a 3" barrel for this shot, and you entered a 2" barrel. The use of a 3" barrel significantly increased muzzle energy for this shot.
Also, you entered 2" porting, while the porting on my valve system is only 1.61". This slightly reduces performance. (the union is ~1.9" ID, but the rest of the valve is only 1.61, and the flow is determined by the place with the least flow)
The pressure used was 470, not 450, the dead space is more like 10+ cubic inches, and the flow coefficient of a burst disk valve is at least 50, possibly 55.
The most significant problems however, are the bore and the valve:
I used a 3" barrel for this shot, and you entered a 2" barrel. The use of a 3" barrel significantly increased muzzle energy for this shot.
Also, you entered 2" porting, while the porting on my valve system is only 1.61". This slightly reduces performance. (the union is ~1.9" ID, but the rest of the valve is only 1.61, and the flow is determined by the place with the least flow)
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