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Author Topic: My ball shooting mechanism - Having doubts, need help  (Read 1418 times)

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Offline ThomasMTopic starter

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My ball shooting mechanism - Having doubts, need help
« on: March 24, 2012, 02:43:55 PM »
Hello,

This is the mechanism in question, explanation follows:

The circles are gears.
The black part is controlled by a DC motor.
The red gear has a couple of sequential (?) teeth missing.
The gold part tightens (?) a spring.

When the toothless part of the red gear is at the gold gear,  the mechanism fires.
My fear is that there is the possibility that the top lands of the red and gold gears will be pressed against eachother when the mechanism tries to fire again, and that this will break either the gears or the motor.

Let me know if you need more/better clarification.

My questions are:
Is this a good mechanism?
Is there a better (not too expensive) mechanism?
Is it possible to improve this mechanism?

I'm too scared to order the parts and try it out because the mechanism can break.

Thank you very much.

« Last Edit: March 25, 2012, 08:51:17 AM by ThomasM »

Offline Gertlex

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Re: My ball shooting mechanism - Having doubts, need help
« Reply #1 on: March 24, 2012, 03:38:18 PM »
It sounds like you're doing a geared down ratcheting mechanism, similar to what airsoft guns do.  More information on what you're doing would be useful (especially what the yellow gear/axle are attached to)

Quote
that the top lands of the red and gold gears will be pressed against eachother

I have no idea what you're referring to here, unfortunately.

I have no idea what size we're talking, but if you're after an example, gearboxes like this one do what you're trying to do.  They generally gear down a lot more than you are doing.
I

Offline ThomasMTopic starter

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Re: My ball shooting mechanism - Having doubts, need help
« Reply #2 on: March 25, 2012, 02:33:34 AM »
Thank you for your reply, I'm sorry for my rather unclear explanation.

Quote
that the top lands of the red and gold gears will be pressed against eachother

I have no idea what you're referring to here, unfortunately.

I meant the Top of the teeth

It's not going to be big, it's going to fire a tennis ball.

When the motor is on, the gold part will be pulling a cord that tightens the spring, then at a certain moment the red gear will no longer have contact with the golden gear, because it is missing some teeth. The spring will then fire the ball. My fear is, that when the red gear tries to make contact again with the gold gear, the teeth could be out of position and two tops could meet. (I'm using a sensor to detect wether the gold and red gear are connected which will make the motor stop temporarily to give the mechanism time to unwind (?).)

Another problem is a mechanism to tighten the spring but I'm still thinking about that.

Thanks for your time.

Offline Gertlex

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Re: My ball shooting mechanism - Having doubts, need help
« Reply #3 on: March 25, 2012, 08:49:15 AM »
It seems like you would want multiple revolutions of the yellow gear to wind up the cord/spring thing.  To do that, the red gear needs to be much larger than the yellow gear.

I think I see what you mean about gear teeth being at risk right before the two lose contact.  I'm not sure how this works out in general, but those teeth in an airsoft gearbox are much larger than those on the rest of the gears.
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Offline ThomasMTopic starter

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Re: My ball shooting mechanism - Having doubts, need help
« Reply #4 on: March 25, 2012, 08:51:00 AM »
Thank you Gertlex, I'll look into how airsoft gearboxes work

 


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