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 Motor/Wheel Questions [MELTY Ant]

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Jeff L
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PostSubject: Motor/Wheel Questions [MELTY Ant]   Sun May 09, 2010 7:36 pm

So I'm doing some more in-depth work on my antweight melty design, and I've come to the question of what wheel and motor I should use. For weight's sake, I'm aiming to use only one wheel [and therefore only one motor]. The catch is, I'd like to have weapon a tip speed around 8,000 RPM (which is a nice neighborhood for a 5"-6" diameter weapon speed), but that means the wheel needs to hit around 30,000 RPM. So, what does everyone think the best choice for a wheel [and motor] at those speeds is? Keep in mind this is an antweight bot, and I'd like to keep the wheel & motor around an ounce each if possible.

My current thoughts are to take the smallest colson available and maybe reduce its overall width on a mill, driven by a micro brushless outrunner (the kind used for miniature RC helicopters).

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PostSubject: Re: Motor/Wheel Questions [MELTY Ant]   Sun May 09, 2010 9:34 pm

Have you or anyone else figured out how to control a brushless in a melty?

Also, I don't know that anyone has really gotten much over 100o to 1500 rpm with much luck while translating.....

So, what do you know different?

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Cody
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PostSubject: Re: Motor/Wheel Questions [MELTY Ant]   Sun May 09, 2010 10:03 pm

From what i remember death by translation ate threw colsons on a thirty and MUCH lower rpms.
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Jeff L
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PostSubject: Re: Motor/Wheel Questions [MELTY Ant]   Sun May 09, 2010 10:16 pm

To my knowledge, there is no good reason why manipulating a brushless motor should be much more difficult than a brushed motor, except the need to take into account for hardware specifics. After all, you only need a few set pieces of input data (the robot's current rpm and three receiver signals) to produce the translational control output (throttle signal * [% angular modulation]). I'm 99% sure all this could be done by one arduino microcontroller accepting three inputs and producing one output for a standard brushless ESC to drive the robot.

However, now that I think about it, the problem concerning high-rpm translation is due to too little time to actually apply the modulation to the wheel, and should be even worse at higher speeds. That said, consider this project scrapped - there is no good way to improve translation at high speeds (in two dimensions) on MELTY bots, rendering them inferior in the lighter weight classes.

EDIT - Except maybe if it's a hovercraft. Then it might work.

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PostSubject: Re: Motor/Wheel Questions [MELTY Ant]   Sun May 09, 2010 11:03 pm

Quote :
rendering them inferior in the lighter weight classes

cant say i agree with it at all
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Jeff L
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PostSubject: Re: Motor/Wheel Questions [MELTY Ant]   Mon May 10, 2010 1:07 am

Cody Harris wrote:
Quote :
rendering them inferior in the lighter weight classes

cant say i agree with it at all

Sure, they may be durable, but they can't compete for energy against even a plain-old undercutter.

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PostSubject: Re: Motor/Wheel Questions [MELTY Ant]   Mon May 10, 2010 11:10 am

New tack I'm looking at: melty drive (at around 600 rpm), with a more standard friction-driven shell. It may end up requiring a larger battery, but could have some pluses in terms of durability.

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PostSubject: Re: Motor/Wheel Questions [MELTY Ant]   Mon May 10, 2010 12:12 pm

so 1lb at 1k rpm vs maybe a 3 ounce disk at probably 4k at the most isnt even close? i dont feel like doing the math but i have to think there more then just close

most undercutters dont spin to the moon
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Jeff L
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PostSubject: Re: Motor/Wheel Questions [MELTY Ant]   Mon May 10, 2010 12:16 pm

Cody Harris wrote:
so 1lb at 1k rpm vs maybe a 3 ounce disk at probably 4k at the most isnt even close? i dont feel like doing the math but i have to think there more then just close

most undercutters dont spin to the moon

6" OD, 5.75" ID, 1" H, steel mono-tooth = 2.66 kJ at 8594 RPM. At 3000 RPM, it's 0.325 kJ.

EDIT: And that's a ring. Bars are less efficient, but I've seen both discs and bars run pretty fast in more than a few ants.

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rjw
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PostSubject: Re: Motor/Wheel Questions [MELTY Ant]   Sun Sep 05, 2010 12:17 am

some melty logic in this thread, I think...

technology can change overnight

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