4 ms·

I also loved the video. But I'd think if one wanted to deploy "simple" mechanical projectile weapons at scale, pneumatic launchers would be easier, more compact

by gattr 2mo ago

I also loved the video. But I'd think if one wanted to deploy "simple" mechanical projectile weapons at scale, pneumatic launchers would be easier, more compact and more reliable (way less cool-looking and operating, though!).

genewitch 2mo ago
like a potato cannon? I helped design the "reloadable" part of a golf-ball shooter that used acetylene as the accelerant. I don't think it went supersonic, though. There's videos (embarassing ones) on youtube. He eventually designed one that can shoot full cans of monster energy hundreds of yards. the reason i bring it up is we used to design and build pneumatic ones, that could send C and D batteries thousands of feet if you arced it right. that was with ~125psi, we always wanted to build out to 200+ psi, but instead went into accelerant-based cannons and he got a job doing machine drawing with autocad. the rest is history. edit: https://nextcloud.projectftm.com/index.php/s/cobra5x https://nextcloud.projectftm.com/index.php/s/cobra5x we show off the part i designed, toward the end on the "reload" - he designed and built the entire thing.
- qwery 2mo ago
  Sorry to be a bore [that's a firearms joke], but -- while I encourage everyone and their family to experiment with building such devices, with safety in mind of course, it is a lot of fun -- please don't dispose of your old batteries in the natural environment! Really not trying to call you out here, as a teenager I once had the idea to load up my marble cannon with dead AAs (they're free!) and got a "do you really think that's a good idea?" from an environmentally conscious adult when I went asking for dead batteries.
  - genewitch 2mo ago
    We moved on to oranges really fast after realizing that batteries coming out of the sky randomly was probably a bad idea, even if there were no apparent people around. Don't get me wrong, oranges are dangerous too, coming out of the sky at terminal velocity, but at least when they hit the ground they disappeared into a fine, 3 meter wide mist.
  - jpfromlondon 2mo ago
    oh my god, were it not for your redundant comment I might've gone to the forest to discard my collection of depleted batteries, thank goodness.
MomsAVoxell 2mo ago
I dunno, takes a lot of energy to get a pneumatic system up to the same speeds that this trebuchet can accomplish. I see it really as a super-efficient machine requiring very little effort to load .. But yeah, the fact that it's super cool looking - and sounding - is a key factor in my willingness to play with one too, one day. ;)
monster_truck 2mo ago
Basically anyone can go buy a pellet rifle that will easily and consistently clear 1500fps. They're still pretty cool, and will go through both doors of a car
gcanyon 2mo ago
I think the cycle time on this would be far superior to a pneumatic system: cycling this system effectively means lifting ~100 pounds ~8 feet, which a reasonably fit person (who could reach that high) could do several times a minute for extended periods. He got an efficiency over 40% (if memory serves, I watched this video yesterday) -- I wonder between pumping and discharge how efficient a pneumatic system would be, but I can't imagine that it's higher.
- fc417fc802 2mo ago
  If the pump were operated by a bicyclist and the projectile feed automated I imagine the pneumatic system would win out by a very wide margin regardless of any reduction in overall efficiency.
  - MomsAVoxell 2mo ago
    Once this thing is dialed in, a wind- or stream- rechargeable version is the obvious next step.
  - gcanyon 2mo ago
    I've seen potato guns (obviously much larger bore than this) and inflated bicycle tires to 100psi+ How do you imagine making the cycle time better "by a very wide margin" compared to lifting 100 pounds less than 10 feet?
    - fc417fc802 2mo ago
      Isn't it a simple matter of sustained energy output scaled by the overall efficiency? I'm saying that a human cycling can sustain much much higher energy output for much longer than most other forms of exercise. Running probably comes close and swimming likely exceeds both of those but in the latter two cases I'm not clear how you could productively harness energy from the activity with any sort of efficiency so it doesn't apply here.

by gattr 2mo ago

genewitch 2mo ago

like a potato cannon? I helped design the "reloadable" part of a golf-ball shooter that used acetylene as the accelerant. I don't think it went supersonic, though. There's videos (embarassing ones) on youtube. He eventually designed one that can shoot full cans of monster energy hundreds of yards. the reason i bring it up is we used to design and build pneumatic ones, that could send C and D batteries thousands of feet if you arced it right. that was with ~125psi, we always wanted to build out to 200+ psi, but instead went into accelerant-based cannons and he got a job doing machine drawing with autocad. the rest is history. edit: https://nextcloud.projectftm.com/index.php/s/cobra5x https://nextcloud.projectftm.com/index.php/s/cobra5x we show off the part i designed, toward the end on the "reload" - he designed and built the entire thing.

qwery 2mo ago
Sorry to be a bore [that's a firearms joke], but -- while I encourage everyone and their family to experiment with building such devices, with safety in mind of course, it is a lot of fun -- please don't dispose of your old batteries in the natural environment! Really not trying to call you out here, as a teenager I once had the idea to load up my marble cannon with dead AAs (they're free!) and got a "do you really think that's a good idea?" from an environmentally conscious adult when I went asking for dead batteries.
- genewitch 2mo ago
  We moved on to oranges really fast after realizing that batteries coming out of the sky randomly was probably a bad idea, even if there were no apparent people around. Don't get me wrong, oranges are dangerous too, coming out of the sky at terminal velocity, but at least when they hit the ground they disappeared into a fine, 3 meter wide mist.
- jpfromlondon 2mo ago
  oh my god, were it not for your redundant comment I might've gone to the forest to discard my collection of depleted batteries, thank goodness.

MomsAVoxell 2mo ago

I dunno, takes a lot of energy to get a pneumatic system up to the same speeds that this trebuchet can accomplish. I see it really as a super-efficient machine requiring very little effort to load .. But yeah, the fact that it's super cool looking - and sounding - is a key factor in my willingness to play with one too, one day. ;)

monster_truck 2mo ago

Basically anyone can go buy a pellet rifle that will easily and consistently clear 1500fps. They're still pretty cool, and will go through both doors of a car

gcanyon 2mo ago

I think the cycle time on this would be far superior to a pneumatic system: cycling this system effectively means lifting ~100 pounds ~8 feet, which a reasonably fit person (who could reach that high) could do several times a minute for extended periods. He got an efficiency over 40% (if memory serves, I watched this video yesterday) -- I wonder between pumping and discharge how efficient a pneumatic system would be, but I can't imagine that it's higher.

fc417fc802 2mo ago
If the pump were operated by a bicyclist and the projectile feed automated I imagine the pneumatic system would win out by a very wide margin regardless of any reduction in overall efficiency.
- MomsAVoxell 2mo ago
  Once this thing is dialed in, a wind- or stream- rechargeable version is the obvious next step.
- gcanyon 2mo ago
  I've seen potato guns (obviously much larger bore than this) and inflated bicycle tires to 100psi+ How do you imagine making the cycle time better "by a very wide margin" compared to lifting 100 pounds less than 10 feet?
  - fc417fc802 2mo ago
    Isn't it a simple matter of sustained energy output scaled by the overall efficiency? I'm saying that a human cycling can sustain much much higher energy output for much longer than most other forms of exercise. Running probably comes close and swimming likely exceeds both of those but in the latter two cases I'm not clear how you could productively harness energy from the activity with any sort of efficiency so it doesn't apply here.