Originally published at: https://boingboing.net/2020/11/20/gentleman-builds-very-large-nerf-launcher.html
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“This guy is not taking the bullshit at the cubical farm”
First, we assume a spherical bull.
Edited to add: This was much funnier before the spelling error in the summary was corrected. Now it’s only a little funny.
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Man, this guy is one joyful builder.
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There are elastic, or spring, driven nerf guns and air pump nerf guns; i’ll confess i was shocked (shocked) that his fine fellow (Ivan Miranda) wasn’t making an air pressure model. May we assume that the muzzle velocity, hence kinetic energy, of an air gun will in general (JoergSprave notwithstanding) outpace a spring/elastic model?
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I’m going to spoil it for everyone and tell you right now; no, no one gets nailed by this thing at any point in the video.
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Although I admit I definitely expected air pressure to be the mechanism, I also had some doubts as to how well it would work. It my mind you’d need:
- A fairly strong and large pressure vessel to hold the compressed air enough to fill the entire barrel with gas at (ideally) >1 atmosphere of pressure.
- Some way to transfer that pressure suddenly, which seems like it could be difficult with such a high volume gas transfer.
Not impossible, but I didn’t see any external vessel attached in the preview image, so I was curious how he managed it.
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I had an idea to make a spud gun with a rupture disc as the release mechanism. Just keep pumping until it reaches a suitably high pressure and watch it explode. My back of the envelope would suggest supersonic spuds, but I’m fairly sure a got something wrong in that calc. Still, might work and could be repurposed for firing nerf bazookas.
More cheaply, you could use 3l drinks bottles that fail at something like 12 bar. There’s a lot of energy in that! The hard part then is a containment vessel that is only just bigger than a failing drinks bottle so as not to remove too much energy. It would need some trial and error to get right i expect.
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You could borrow a few design ideas from this.
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Thanks for posting. I sent along to my dad, who’s an engineer and (like me) a rabid baseball fan.
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Finally, a way for the common foot soldier to fight back against Nerf tanks.
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Indeed.
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Sure, it might be over powered now, but it probably will get nerfed in the next patch.
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Thank you for posting the transonic baseball cannon, for me, the world has just become that bit more fun and happy a place to be. 
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The follow up video of them trying to catch the supersonic baseball is also worth your time.
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I did this with 2 liter bottles. IIRC the estimated energy was 300 kilojoules, enough to launch a pineapple vertically for 11 seconds. (Say “boom” and look up higher and higher as you count to 5 1/2 to imagine just how serious this is.) The pineapple experiment, before my time, was performed inside an athletic field’s metal fencepost that was conveniently just barely larger than 2 liter bottles. My personal experiments were mostly about launching large quantities of oranges, which would come down as mush.
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Wow! Someone actually did it! That was amazing!
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We’re they mush when they left the barrel?
If your question is, did the launch mush them or did the landing, then surely the launch. In a vacuum, they suffer the same impulse at launch and land, but in air, they’ll land slower than they launch, especially if they’re already mush and have lots of air resistance.
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Air has the advantage that with a longer barrel and enough pressure, the projectile will keep accelerating until it exits the barrel. With a spring acceleration will stop when the spring is back at it’s original length. Any spring can’t be compressed all that much before the coils touch. Though tensile elastic elements could be used with the right mechanism to avoid that limitation.
We built something like this (near identical dimensions to the video) at the local university using a big tube and a medium size pressure vessel (about the size of a bbq propane tank). Though we launch a 20 kg slug of aluminum at about 100 kph (44 lb at 60 mph).
We activate it with a manual valve - a ball valve with 90 degree lever rotation between on and off. So it’s pretty quick to let the air in the barrel. The pressure vessel is either a tire debeader or a larger industrial unit which both have about a 2 inch outlet diameter.
We had an earlier version where we sealed both ends with thin diaphragms. We didn’t pressurize the barrel but instead connected it to a vacuum pump. Then we punctured the end opposite the projectile exit and let atmospheric pressure accelerate the projectile. That was launching much lighter foam samples. I don’t recall how fast.
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Having seen a small compressed-air spud cannon launch potatoes with enough force to dent quarter-inch steel plate, I’d have to guess “yes” to that.
The spudlauncher I saw used wide copper tubing as the barrel (I’d guesstimate 2-1/2") with a lever-operated ball valve and a small compressed air tank, usually used for quick-inflating car and truck tires onto rims. It would be interesting to try that with a solenoid-operated valve. The trick would be getting one with sufficient capacity.
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