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This is really my first attempt at a gearbox using actual numbers so please feel free to comment..any tips are appreciated
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A few comments on drive train / transmission design:
1. Design everything around maximizing power output. Essentially, this means that at the point where your wheels slip, your should be peaking current draw from your motors (40 amps each). You need to employ a factor of safety in there somewhere, perhaps 10%.
2. This implies that there will be different ratios for a design with the Fisher-Price or Drill motor. You need to pick one of these to design around.
3. People have mentioned having the shaft supported on both sides. This indeed generally a good rule of thumb. However, the real reason it's good to have a shaft supported on both sides is to reduce shaft deflection. The moment of inertia of a shaft, which is a factor in it's deflection is a function of diameter to the 4th power. Larger shafts mean you may not need to have it supported on both sides, especially early in the transmission where torques / forces are lower. Also, having a gear moving closer to the side of the transmission will reduce deflection.
4. A Karl Kreder-ism (college advisor on our team last year) is that the round posts like you have are difficult to work with, having ledges (ASCII sketch below showing top view) work better to encourage overall alignment and stiffness, which is critical for gears.
ASCII Sketch
Code:
* *
* *
* o o o o o o o o o o o o
* o o o o o o o o o o o o
*'s - walls with ledge notch cut in them.
o's - wall that fits on ledge.
Just some ideas. Ask for more details if you need 'em.
Matt