Why not put dog gear on second stage?

Most shifting gearboxes have two initial reduction stages, then the shifting stage. In all the gearboxes I’ve seen, the shifting is done on the final output shaft. Is there a major reason why the shifting is never done on the output of the second reduction? I realize that in many gearboxes, it would be impossible to do the shifting on the second stage shaft because it is usually blocked by the gear from the first stage and therefore nothing can be connected to the shaft that moves the dog gear. The first image is an example of what I mean. The second image is another example of what is typically done. The third image is what it would look like to do the shifing on the second stage output. I also realize you would need to use large gears in that case.

That’s the main reason, since you’re optimizing the mechanical design for weight.

That’s kind of what the standard Vex Ballshifter layout already does. The ballshifter mechanism allows for ball gears that are smaller than most dog gear

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I’ll pose the opposite question: what advantages would there be to putting the shifter on the cluster shaft instead of the output shaft?

More possible points at which you can shift, and less issues with shifting at speed causing “shimmies” due to one side shifting slightly after the other. Our programmers had fun with that this year when we swapped from the standard ballshifter layout to a custom design that puts the ballshifter on the output shaft. In 2018, we shifted something like 10 times in auto.

The reason I was asking is actually because I am trying to use only one stage of reduction before the shifter. In this case, it is pretty much impossible to put the shifter on the output shaft, so I was going to put it through the shaft with the initial reduction. I don’t have a picture I can show yet because I haven’t figured out the gearing ratios yet.

Wow, that seems like a lot

I completely forgot about those and I’ve never looked at the inside of them. Thanks for reminding me.