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A place to ask general spud cannon related questions.
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 18, 2007 10:17 pm

jon_89 wrote:Has anyone here used electric motors to shoot projectiles? would it have a decent amount of power?


you mean a linear motor like a railgun, or a rotating electric motor like in this cd thrower?
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Unread postAuthor: Fnord » Tue Dec 18, 2007 10:19 pm

If you're talking about a centrifuge type gun, I don't think anyone has made one yet.

If you have a handheld gun with a 1' diameter "chamber", you'll need to get it spinning pretty fast to get a decent velocity. You're looking at 15000 rpm for 785 fps, so it might be possible with a good circular saw motor.

diameter * 3.14 * rpm / 60 = velocity

If you're talking about a baseball pitching machine, yeah, people have built those, but I don't have a link right now.

Jack?

(edit: of course, jack posts a reply even before I ask him to)
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Last edited by Fnord on Tue Dec 18, 2007 10:21 pm, edited 1 time in total.
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Unread postAuthor: ShowNoMercy » Tue Dec 18, 2007 10:19 pm

How do you manage to always find something related to the topic but at the same time ......not?
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 18, 2007 10:30 pm

_Fnord wrote:If you're talking about a centrifuge type gun, I don't think anyone has made one yet.


yes they have, and quite powerful too ;)

How do you manage to always find something related to the topic but at the same time ......not?


Mental archive, don't ask me how.

baseball pitching machine (works on the same principle as the cd thrower linked to above):

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edit: btw _Fnord, absolutely LOVE the icon :D
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Last edited by jackssmirkingrevenge on Tue Dec 18, 2007 11:00 pm, edited 1 time in total.
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Unread postAuthor: jon_89 » Tue Dec 18, 2007 10:52 pm

Yeah i have seen the pest before but is there a more simple way to build it? would two motors and wheels work better then an arm?
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 18, 2007 11:03 pm

jon_89 wrote:Yeah i have seen the pest before but is there a more simple way to build it? would two motors and wheels work better then an arm?


They're both turning rotational velocity into linear velocity, but I imagine with wheels the setup would be heavier, therefore for a given motor you'd get less RPM and consequently less velocity, so for decent power you'd have to up the calibre. Btw as far as I know only one of the wheels has to be powered.
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Unread postAuthor: jon_89 » Tue Dec 18, 2007 11:07 pm

I think the arm setup is a little to out there for right now. If i went with the wheel setup what size of motor and wheels do you think i should have?
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 18, 2007 11:10 pm

Well, a motor as big as you can obtain and the most reasonable size of wheel it can handle turning at high revs - it depends on what sort of balance and portability you're after. For example if you use a 1.5 volt motor from a cheap toy car, you'll get a pocket sized design, but shite power.
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Unread postAuthor: jon_89 » Tue Dec 18, 2007 11:12 pm

Well with the right setup do you think it is possible to go through a can at lets say 25 feet?
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 18, 2007 11:15 pm

jon_89 wrote:Well with the right setup do you think it is possible to go through a can at lets say 25 feet?
<--- on that condition, yes.
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Unread postAuthor: jon_89 » Tue Dec 18, 2007 11:19 pm

so how fast would the motor have to spin to reach high velocities? I dont need an exact number but just an estimate. what would be the best material for the wheels?
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 18, 2007 11:32 pm

RPM depends on the size of wheel, because the larger the diameter, the faster it's spinning. For example, let's assume a 2" wheel at 5000 rpm, theoretically at the circumference it's doing 43 feet per second. A 4" wheel at the same speed will give double the velociy if spinning at the same rpm.

If you can get an 8" wheel spinning at about 7500rpm, I'd say it would be enough to but a steel BB through a pop can at 25 feet.

As to the material for the wheels, the lightest strongest stuff you ca nfind that will spin at that speed without flying apart, also the rim needs to have enough friction to transfer maximum energy to the projectile.
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Unread postAuthor: jon_89 » Tue Dec 18, 2007 11:37 pm

i just thought of something not to go off topic but is there anyway to make an electric airsoft pistol stronger? so the bigger the wheel the faster the projectile will go? if a put the wheels at a slight angle will the put a spin on the bb?
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 18, 2007 11:47 pm

jon_89 wrote:i just thought of something not to go off topic but is there anyway to make an electric airsoft pistol stronger?


Upgrading an EBB to death

so the bigger the wheel the faster the projectile will go?


For a given rpm, yes - but if you put a bigger wheel on the same motor, it will be heavier so the motor will spin slower as it's under a greater load.

if a put the wheels at a slight angle will the put a spin on the bb?


if both wheels aren't at precisely the same speed and friction levels, you're going to get spin on the BB anyway.
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Unread postAuthor: jon_89 » Thu Dec 20, 2007 1:54 am

what would be a good motor to use running off a 9 volt? i am thinking a rc plane motor.
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