hey got a tech question about AM Trannys

[Andy Baker]

Originally Posted by jax1488

does anyone know the final output RPM of an andymark tranny? of high and low gear?
i cant find any information online

Originally Posted by jax1488

servo shifter (gen 2), with 2 small cims a piece.. i dont understand how to do the math

All... looking through this thread, I really don't think that the original question was answered.

On the AM Servo Shifter page, these gear reductions are listed:

Gear Reduction
Low: 10.67:1
High: 4.17:1
Difference between Low and High: 2.56:1

Here is my description on how to "do the math", in a nutshell:

A CIM motor has a free speed of about 5200. If two CIM motors are installed on an AndyMark gearbox, then the top speed (motor rpm) that you will be able to get is about 4300 or 4400. Let's call this the "top working speed". (The difference between the free speed and this working speed is because of efficiency losses, inertia, and friction in the mechanical system)

Using 4400 rpm as this top working speed, here are the resulting low and high speeds for an AM Shifter (servo or pneumatic):

Low: 412 rpm (4400 / 10.67)
High: 1055 rpm (4400 / 4.17)

This is the output rpm at the sprockets on the AM Shifter. Further reduction can be made, of course, with the sprockets on the wheels and the size of the wheel. Keep in mind that the smaller your wheel is, the less reduction you need to go an optimal speed.

Now... regarding the roll pins shearing and other stuff, I will make another post. Tyler's post is right on the money. However, the Super Shifter did see more vibration this year than the AM Shifters experience. The AM Shifters all use chain drive. The Super Shifters can be used in direct drive situations. Because of this, the Super Shifters experience more vibrational loading.

Like previously noted by Tyler and Travis, you must use stops on the cylinder so that the dog is positioned into place and held there, as opposed to continually pushing the dog into the gear. For servo shifting, this burns up the servo. For pneumatic shifting, this wears down roll pins.

Also, shifting at 40 psi seems to work the same as 60 psi. I do not suggest using 25 psi unless you are only shifting when not pushing against anyone. Also, servo shifting does not work when pushing against anyone. Servo shifting pushes with about 5 pounds of force. Pneumatic shifting at 60 psi puts out 33 lbs of force. Regulating the pressure down to 40 psi still gives 22 pounds of shifting force. This is still much stronger and more responsive than servo shifting.

Once again, I will say that I DO NOT RECOMMEND servo shifting, unless a team has absolutely no need for pneumatics on their robot.

We have some improvements listed for these gearboxes:

gearing options - other ratios (Toughbox, Stackerbox, maybe Shifters)
adding an encoder to the Toughbox and AM Shifter
higher strength roll pins
Longer output shaft for Toughbox
A better way to servo shift
Optional aluminum side plates for AM Shifters

These are in order of importance and priority. There may be more. We have a "to do" list on our main whiteboard at AndyMark central that is about 50 items long.

I hope this helps.

Sincerely,
Andy