pic: High Reduction 2-Stage Gearbox

[Andrew_L]

This is fantastic for your first DOG shifter - be proud of yourself for what you're accomplishing.

To touch on your points:

-"5.5 ft/s low, 16 ft/s high" - this is a good spread to work with. I've personally found that you'll rarely need to go lower than 6 ft/s (or 5.5, 0.5 ft/s doesn't make much of a difference), and you rarely need to go higher than 16 ft/s. For future games, sometimes you'll need your high gear to be a little lower, and sometimes you can have your low gear a little higher. Either way, that's a good design decision you've made.

- 2.0 lbs - compared to 3.1 lbs for comparable COTS gearbox - Good target weight, though I think the reason your transmission is a pound lighter than the COTS alternative is more due to some cut corners than it is to a more weight-friendly design. Make sure your plates cover the circumference of your CIMs almost completely, otherwise there's room for bending and awkward loading. Also, make sure all of your material and mass properties are assigned correctly. It's easy to realize later that some non-custom parts, like the motors, shifting shaft, and shifting cylinder, were vastly underweighted in CAD. The spacing also looks a bit off on your shifting shaft, so unless that's custom, I'd double check with the WCP DS CAD model to see if you're using it right.

- Will the 32dp gears hold up? (They should according to the Lewis Formula) - We have done 32dp gears for our initial stage on a gearbox before on 1323, though I wasn't on the team at the time (maybe RC can comment on it). I do know that we don't actively do it anymore, so I'm guessing we stopped for a reason. Where most of the problem is going to arise is when you're in high gear, and the 32dp gears are the weak link in the chain of power transmission. Those pinions look pretty thin as they are, and I'm not sure how well they'd hold up, even if they were steel. You can achieve a lightweight 2 stage gearbox for an 8" wheel using 20dp gears, you just need to get creative.

- Am I doing dog shifting correctly? (This is my first dog shifter) - Like I said earlier, double check with the WCP DS model. Your shifter shaft looks a bit off to me, and it looks like you have an extra shifting cylinder mounting plate attached to your gearbox plate (you only need one, and none on the plate itself). Also you shouldn't need a shaft collar to hold your bearings in. Look into either geometrically retaining them (aka the model's geometry physically prevents the bearings from coming out), or by using the head of a #10 button head cap screw to retain the bearing flange (as seen on the WCP DS).


Overall, this is a fantastic first shifter. Keep up the great work and continue iterating and you'll only get better and better. As my boy Macklemore once said, "The greats weren't great because at birth they could paint, the greats were great because they paint a lot".