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PostSubject: Variable pitch?   Sat Nov 14, 2009 3:04 pm

Are we doing a mechanical VP or servo based? The problem I have with a servo based variable pitch is how to get it to actuate inside the aircraft style shaft we have for the sub. What do u guys think? I'm really not sure what you all are considering at this time.
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Morford
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PostSubject: Re: Variable pitch?   Sun Nov 15, 2009 5:24 am

I'm considering your mom...




But seriously, variable pitch is on the table, but I'm not entirely sure how to implement it if we go with it. Servo actuated would be nice and such, but I think a mechanical one might be easier to implement.
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PostSubject: Re: Variable pitch?   Tue Jan 12, 2010 10:22 pm

Your welcome...

Variable Pitch Prototype
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PostSubject: Re: Variable pitch?   Wed Jan 13, 2010 12:28 am

already saw it
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PostSubject: Re: Variable pitch?   Wed Jan 13, 2010 12:39 am

so is this what u had in mind for the system? It would be easy to add 2 additional joints if you wanted a 4 prop system.
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PostSubject: Re: Variable pitch?   Wed Jan 13, 2010 12:52 am

I was thinking about it, since it's a fairly simple and looks reasonably reliable, although I think it would need some beefing up to make it work in the water correctly. Also that way wouldn't require a huge amount of machining, at least I don't think it would.

I saw a different way of doing the variable pitch that I kinda liked, but it would probably require more machining than we'd be able to do without Ron's shop open.
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PostSubject: Re: Variable pitch?   Wed Jan 13, 2010 12:57 am

yeah exactly what i was thinking... Brandon and I kinda have some issues with the servo shaft that will move the pitch. We feel that it just isn't powerful enough to move it in the water. We could try it and If it does work regardless I would like to see some kind of kill switch that would make the system numb upon a crash or something
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PostSubject: Re: Variable pitch?   Wed Jan 13, 2010 1:03 am

Also, if we can get a bunch of that carbon fibre from the company Turner was talking to, I think we could rapid prototype a a large portion of the parts and use the carbon fibre to make them, thus cutting down on a large portion of the machining while not sacrificing strength too much.
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PostSubject: Re: Variable pitch?   Wed Jan 13, 2010 1:07 am

As far as the servo not being powerful enough, I think that if it wasn't, we could either increase the length of the horn, or we could just double up on the servos, like have two or three servos actuating the shaft instead of just one.

We could also add springs to help it
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PostSubject: Re: Variable pitch?   Wed Jan 13, 2010 6:29 pm

Would putting multiple servos on the one shaft work? I honestly don't know. Some might move faster than others just by more/less resistance than the others.
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PostSubject: Re: Variable pitch?   Wed Jan 13, 2010 7:25 pm

holy crap, is Ron's shop permanently shut down? I walked by today and it was completely empty. Not like he was ever there when he was supposed to be anyway.
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PostSubject: Re: Variable pitch?   Wed Jan 13, 2010 7:42 pm

I doubt the difference in servo speed/strength would be that great to actually matter, but Subrat might know better than me, and if it could matter, he might be able to build something to counter it through the micro-controller.

Or we might just be able to buy a stronger servo.
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PostSubject: Re: Variable pitch?   Wed Jan 13, 2010 9:00 pm

but stronger servos are more expensive.
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PostSubject: Re: Variable pitch?   Wed Jan 13, 2010 10:15 pm

morford means to say to use the servos we have, but through them in series to increase the driving force. Or increase the ohms or something
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PostSubject: Re: Variable pitch?   Fri Apr 02, 2010 7:46 pm



Motor Type: Coreless
Bearing Type: Dual Ball Bearing
Speed (6.0V/7.4V): 0.17 / 0.14
Torque oz./in. (6.0V/7.4V): 333 / 417
Torque kg./cm. (6.0V/7.4V): 24.0 / 30.0
Size in Inches: 1.57 x 0.78 x 1.45
Size in Millimeters: 39.88 x 19.81 x 36.83
Weight oz.: 2.39
Weight g.: 67.76

333OZ/IN on a 6v supply. I have to see if we can run this. Apparently it is also "water tight". Im not sure what IP rating their "water tight" implies but this motor Triples our torque.
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PostSubject: Re: Variable pitch?   Fri Apr 02, 2010 9:13 pm

I've been wondering if maybe we could find a linear actuator that would do the job better.

I was looking about and apparently a company called Firgelli makes "waterproof" rubber boots for their linear actuators, although it doesn't say how deep they can go, and they probably mean "splash proof." But I think it's something to consider.

I just think a linear actuator would be stronger and less of a hassle than trying to use servo motor, but we can discuss this tomorrow.
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PostSubject: Re: Variable pitch?   Fri Apr 02, 2010 9:38 pm

Firgelli's are expensive. I looked into those when I was doing IPPD. There are companies out there that make waterproof linear actuators but im not sure if we could run it off battery. The battery drain might hurts us
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