I haven't designed or built a custom gearbox myself, but a few comments based on basic physics:
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Originally Posted by Chak
This can be a separate gearbox, or it could be the drivetrain rail itself. |
I like the simplicity, though I'm a bit leery about a gear ratio of less than 6:1, especially if your robots tend to barely make weight. I see this as much more likely built in to the chassis rail, especially as I try to figure out how to mount this segment of tubing to a separate chassis.
Quote:
Originally Posted by Cothron Theiss
I assume that the gear is exposed more on the bottom of the rail than the top because of the center-dropped axle, so would it be worth making this gearbox direct drive the back wheel instead of the center? That way you can flip the gear cut-outs and have the top side be more exposed.
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Quote:
Originally Posted by KohKohPuffs
Might be my tendency to have reasonable doubt when it comes to structural integrity, but my concern is if 1/16" thick boxtubing will be strong enough, especially to support the CIMs.
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I agree with KohKohPuffs (and others) that 1/16" seems rather light for most FRC purposes, but not because of CIM support. A CIM weighs under three pounds, and it's only cantilevered out a few inches. If you were worried about it, you could move the CIM back a bit farther with some spacers and put a bearing in the far wall to provide more support than you should ever need for the CIM, unless you were expecting someone to stand on the motor. The drive shaft, on the other hand, can easily support half the weight of the robot as it rocks from the front to rear wheels (or vice versa). For this reason, I endorse keeping the bearing mount low, putting more of the tubing structure above the bearing hole. (Rule 1 that we figured out about drive chassis design is to first consider the stress of keeping the robot off the ground; supporting motors and wheels is minor next to that.)
The lower pocket is clearly larger than the top based on the number of teeth exposed. As others have noted, It must be large enough to allow the gear to be inserted, unless you're planning to machine the tubing and gear from a solid block of aluminum
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