Quote:
Originally Posted by M. Krass
Is it possible to mount the servo plate (Drawing No. 5) onto the opposite side of the transmission housing than what is shown? I like symmetry and using as little space as possible for anything and everything.
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Yeah, it's definitely doable. We've always put them on the same side because we would have a default setting on the servos which we used to calibrate them. If you have the servos on opposite sides. If you have the plates on opposite sides then one transmission might have a bias toward 1st gear, and the other might have a bias toward 3rd gear.
Quote:
Originally Posted by M. Krass
Is mounting the assembly by a shaft collar genuinely sufficient? It seems like these assemblies can put out quite a bit of torque in first gear at stall and holding it place only by friction seems daring. Might it be better to adapt the Chiaphua Plate (Drawing No. 1) to mount directly to the robot in addition to the collar? I want to mount a gear to the output rather than a sprocket and am concerned that a collar will allow too much play in the center-center distance between the gears and create problems there.
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We had a debate about this on our team a couple years back, and trust me, those collars are more than sufficient. After 3 years of relying on the DeWalts for our drive train and arms, we've never has a single problem with the collars not being able to take the stress of competition.
Quote:
Originally Posted by M. Krass
We can laser cut .125" and .0625" delrin pieces and chemically bond them together to create a plastic top hat as shown in much less time than it'll take to set up and mill them. Will undersizing the .125" piece by as much as .003" be a disaster? The drawing calls for .128". I'd love to laser cut them, since I can then add a keyway in addition to the pressfit.
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Quote:
Originally Posted by Joe Johnson
The sole purpose of the tophat is to keep the shifting ring from the second gear stage of the Dewalt transmisssion (which, just for clarity sake, becomes the first stage of the gearbox on the Chiaphua design because the normal first stage is eliminated) from tilting out of alignment.
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Since they don't do anything else, I don't see why .003" would make any noticeable difference.
Quote:
Originally Posted by M. Krass
Is there a particular reason the modifications to the top hat carrier call for a counterbored hole rather than a countersink? Again, it seems to be it might be easier to countersink the hole than to counterbore it given our tools and desire to get it done quickly.
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I think it just has to do with the type of screws they recommend in the whitepaper, but I'm not sure.
Quote:
Originally Posted by M. Krass
Is first gear really all that useful, or should I be treating this as a two-speed transmission? It seems like with gearing designed to make the two higher gears useful -- 1:2.5 at the output, resulting in about 1:7.5 and 1:10 -- the first stage reduction then becomes 1:30 and produces way more torque than even the stickiest of FIRST tires can be bothered with. Perhaps it'd be wiser to ignore that first gear all together, since I'm going to be spinning tires there in any case, and gear the second and third speeds down a bit more. 1:10 is awfully fast and 1:7.5 might be illegal on the Autobahn, even.
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First gear is very useful. If anything, you might have more of a problem with the lack of difference between 2nd and 3rd. We designed our drive train to slip the wheels in 1st gear (using rough top on a 6wd). This maximized our speed while allowing us to still use the wheels' coefficient of friction as the limiting factor. In 2nd gear the robot would zip across the field, so we found that 3rd gear wasn't that useful, since 2nd gear was sufficiently fast for all practical purposes.