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 Ring and Pinion Gear

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Matt Jacobs
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PostSubject: Ring and Pinion Gear   Sat Nov 13, 2010 1:56 am

I think we might be able to replace a chain driven drive train with a ring and pinion gear. This would eliminate the need for a chain, tensioner and bevel gear. I would like to make the gear box watertight to reduce drag. Dana mentioned that a 5:1 gear ratio could produce a significant amount of friction, making it more difficult to pedal. If anyone has an idea to calculate the resistance of the gears, please let me know. I'm gonna try to get my hands on a ring and pinion gear to make a full scale prototype.

The pedal arms would attach directly to the main shaft and spin the large ring gear. This rotates the pinion gear, which is mounted on the end of the drive shaft, and rotates the propeller.

We would also need to devise a way to incorporate the variable pitch controls (linear actuator and servo).
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Matt Jacobs
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PostSubject: Re: Ring and Pinion Gear   Sat Nov 13, 2010 2:04 am

Please post some pics of a variable pitch propeller/hub assembly similar to what we are planning on using. We need to know the mechanics of the hub to design the drive train. The pic Dana showed me at the last meeting would require a hollow drive shaft and complicates servo mounting/power source.
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Dana
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PostSubject: Re: Ring and Pinion Gear   Mon Nov 15, 2010 3:17 am

Matt, did someone already show you pics of the variable pitch that you mentioned? Or does that still have to be designed?
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PostSubject: Re: Ring and Pinion Gear   Wed Nov 17, 2010 7:41 pm

I like the idea -- simplicity generally means less things that can go wrong. I have concerns about the dimensions, but we can talk about that tonight
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Matt Jacobs
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PostSubject: Re: Ring and Pinion Gear   Mon Nov 22, 2010 11:17 am

Dana wrote:
Matt, did someone already show you pics of the variable pitch that you mentioned? Or does that still have to be designed?

I saw a picture of another teams variable pitch propeller and hub that was being passed around. Are we going to use the exact same design?
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Dana
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PostSubject: Re: Ring and Pinion Gear   Mon Nov 22, 2010 1:34 pm

That was our human powered submarine propeller and hub. It did NOT have variable pitch. Sorry for the confusion.

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Matt Jacobs
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PostSubject: Re: Ring and Pinion Gear   Tue Nov 23, 2010 7:54 pm

I'm not talking about the hub from last year. I'm talking about photo on your computer. Could you post it? It has variable pitch and a linear actuator that appears like it would run through a hollow drive shaft.
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Dana
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PostSubject: Re: Ring and Pinion Gear   Tue Nov 23, 2010 8:02 pm

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Dana
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PostSubject: Re: Ring and Pinion Gear   Wed Nov 24, 2010 8:07 pm

here is a good 2D drawing of how that variable pitch is implemented. One problem that was discussed was that this design requires a hollow driveshaft. I remember someone mentioned problems with having a hollow driveshaft. Anyone remember what they are?

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PostSubject: Re: Ring and Pinion Gear   Wed Nov 24, 2010 8:18 pm

here's another one but you can't really tell how it works from looking at it. But it gave me an idea....



so say we have the carbon fiber blades, and we put a shaft through the end of it to secure it inside the hub. I think this will work for two blades. it might work for three blades, but not sure how.
Well we can put a pin at the end of the shaft, radially (either weld or use set screws). Then connect the pins for each blade together with a rod. Then attach the linear actuator to the rod.

If nobody is following this, that's perfectly fine, as long as I can follow it later when I can draw it in CAD or something.
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Dana
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PostSubject: Re: Ring and Pinion Gear   Wed Nov 24, 2010 8:42 pm

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Dana
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PostSubject: Re: Ring and Pinion Gear   Wed Nov 24, 2010 9:40 pm

just realized this also requires a hollow driveshaft.
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Matt Jacobs
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PostSubject: Re: Ring and Pinion Gear   Thu Nov 25, 2010 11:31 am

I like your idea for the variable pitch control, but I'm not sure how we will attach the linear actuator. The actuator would have to be off-center to work. That would present a problem when the propeller is rotating.

I don't know why a hollow drive shaft would cause issues. I don't think the amount of torque the driver can produce would be able to bend/twist it. We are planning on using a 3 section drive shaft with 2 universal joints. The short lengths should resist the torque better.
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Dana
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PostSubject: Re: Ring and Pinion Gear   Thu Nov 25, 2010 10:38 pm

You're right, it wouldn't work if it was spinning. It could be mounted in such a way to make it work, but it would be difficult to maintain.

oh, you already have a plan? can you CAD it up and bring it to the next meeting?

Another idea that Tim had was to have a completely electrical variable pitch system. ie, hook up motors (real motors with motor drivers, not servos) and program them with a microcontroller. Which we need to figure out soon, because I am building our microcontroller during final exams week.

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