@jrp62, I really like your Vex IQ lift models. They look great and literally scream “Take me and learn how it works!”
Do you have a demo videos of them in action by any chance?
I am not sure if CAD models would work better, because you need a computer with CAD software to play with them. But you can touch the models or watch a video on almost any device and let your imagination fill the gaps.
Also, it is very easy to understand velocities through the animation, like in this example:
(another video here: Misc - jpearman)
But students keep missing that this planetary transmission design lacks torque balance, which is not obvious even from the best of animations. The output will always be weaker than if you had just connected both motors directly to the wheels, because of the backdriving issue with non-locking planetary transmissions.
Yes, I’ve seen that thread and read it a number of times before! Please, tell your son that it is very well written and was very useful when I was working on the Automatic Transmission topic.
There is a way to solve the motor under-utilization in EVT and get close to 100% efficiency in the high torque mode:
One of our teams tried to build an automatic transmission with the worm gear based (non-backdriveable) differential for ITZ Worlds, but run out of time. It would have been great to have all that extra torque. This is the final and the most compact version we’ve got:
In high torque mode, you could get 9 motors worth of pushing power from just 3 actual motors at 1/3 of the max speed. But it isn’t an easy build and takes a lot of time to tune it.
So, for the Turning Point season our goal was to build a transmission with the minimal friction losses and lesser complexity, which is shown in OP.
Right now most of our students are busy preparing for tests, but I will definitely talk to them later to make a good CAD. The best I could do now is to link a few more videos.
The first variant is what was frequently called MoGo differential transmission (DMD) or “anti transmission” (v4 video by @antichamber: https://youtu.be/x7r2REIz4U0?t=50). Additional explanations:
The second variant of differential transmission uses coaxial motor mounting (in respect to both of its functional outputs) and, in this example, secondary function is used to transform the chassis between the high torque and the high speed modes:
Another video with few more explanations (at 7:40) is here: https://youtu.be/WIVaZDXmQec?t=460