planetary gear questions

The Andymark site mentions that “theoretically, an infinite amount of stages could be stacked on this gearbox” (GEM500 Gearbox, 3 stage, 49.4:1 ratio am-0401). What is the practical limitation for the number of stages that can be used with a CIM motor?

Our tube lifting mechanism uses a screw that has 12 revolutions for full travel.

Any suggestions welcome.


The practical limitation would be torque output capacity of the gear-set (efficiency also goes down with each stage added). They don’t list what the max output torque is, but the shaft is 1/2" diameter 4140, and the carrier is made of 4140. I am not familiar with the carrier design, but I would think the carrier would fail before the shaft. Send Andy a question and ask if there is a rating on max output torque.

Practical? that depends entirely one how much torque and how many rpm’s you want to get out of it.

Theoretically, one could stack 10 stages up if they wanted a very slow rpm or a very large amount of torque. However this would make the total reduction 3.673.673.67*…*3.67 or 3.67^10 which come out to a total reduction of 443262:1, which at no efficiency loss with a CIM would result in about 1 rotation every 1.5 hours… Something tells me this is a little bit more than your looking for.

As for your tube lifting mechanism, I can’t help much since I don’t know the load on the motor, the efficiency of your mechanism or what motor your looking to use. If you can tell us more about your design, I’m sure that there are plenty of people here who would be happy to go over the math with you (myself included).

Be careful - as you add layers planetaries lose efficiency very very quickly. Make sure you’re not defeating the point of the planetary by adding so many gearsets that your efficiency drops ridiculously…

My team is using the 2 stage planetary gearboxes for our mecanum drive system this year. I can tell you that on the basis of speed alone your probably going to want to go with 3 or 4 stages. the CIMs run at around 5000 rpm free speed.

So 5000/(3.673.673.67)= 101 rpm
Or 5000/(3.673.673.67*3.67)=27 rpm

Note: Your actual speed may be significantly lower depending on the efficiency of the gearboxes and whether they are “broken in” or not. See this thread for more info on breaking in gearboxes.

I hope that helped a little. But, as others as stated, in the future You need to be more specific when asking these types of questions.