Sprockets+Roller chain+Rotation >Linear oscillation; how?

Hello there!

I am a high school student, and I am really interested in Physics, esp. electronics and mechanics; I am not an expert or something, so please don't take it hard on me.

Yesterday, I was bored and I messed around and successfully made a catapult (http://www.algodoo.com/algobox/details.php?id=100119). Of course, not IRL, but on my PC.

I am not advertising or something, but I am just saying, you should check the free software named "Algodoo"; it is a 2D physics sim, worth a shot, and totally free. If you can get it, it is easier for you guys to help me because I am using that program.

Anyways, to the point, I am very keen on replicating Mythbusters' "Arrow Machinegun"(), which is a very simple mechanism, basically containing two sprockets, one roll chain, some handles, a slider, bow, string, release mechanism and other miscs.

The problem is, how in the bloody universe, do you have two sprockets and a chain to reciprocate? I heard Jamie saying "the sprocket engaging the slider", but how?

I would really like it if you guys can draw me a model of how I can do it. It'd be even more awesome if you can use Algodoo and draw it for me!

Thanks a lot! :D
 
Hello? Anyone?

Guess not. :/
 

jack action

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I'm not sure how the presented mechanism work, but you can convert rotational motion into a reciprocating motion with many mechanisms:

The crank and slider:

p.gif

The Hoeckens linkage:

Hoeckens_linkage_Animated.gif

Any 4-bar linkage of the crank-rocker type:

650px-Linkage_four_bar.svg.png
 
Last edited by a moderator:
@jack action

First off, thanks a lot for the reply!

The linkage systems, cranks and basic rotary/linear converters won't work for me, because the mechanism I am using is attached to the roll chain, which consists of both rotary and linear motions, so it won't cut it for me.

HOWEVER, I worked it out with a very simple solution this morning; I fused it with a scotch yoke! I attached it with a red pin on the roll chain, and it works just fine; eureka!

Check out the pictures I attached.

Red: Slotted link mechanism
White: Frictionless sliders
Green: Body
Gray: Roll chain
Yellow: Sprockets (gears, wutevz)

Anyways, thanks a lot for your help! :D

https://flic.kr/p/sm8Sb5
https://flic.kr/p/sogoSW
https://flic.kr/p/sogp2U
 

jack action

Science Advisor
Insights Author
Gold Member
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I forgot about that one. Good catch, as I couldn't wrap my head around why they use a chain with 2 sprockets of the same size. It makes perfect sense now.
 

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