Planetary gears

So my team is dealing with planetary gears as a part of the drive, but I had a question regarding its ability to switch between different gear ratios.

We’ve been having trouble setting the planetary gear so that it can be both geared for speed and torque (using changes in relative direction from its input) while maximizing efficiency for both of these settings (I.e. the motors don’t work against each other nor do they share different amounts of torque put into the drive). What is the best way to remedy this?

How is the planetary set up? Maybe some pictures could help us better see your set up so we could help you more.

Congrats on your first post.

we have made a detailed thread about this system in the past
cant find it for you now on my phone, but just use the search dig it up

This is the thread murdomeek is referencing:


Nice drive murdomeek

My planetary is set up like murdomeek’s first iteration of his planetary gear, with inputs at the planetary carrier and the ring gear and the output on the sun gear. The only part of the system that I can change relatively easily is the sprocket (24 tooth) connected to the chain that drives the ring sprockets. With this configuration, both the inputs contribute approximately equal amounts of torque when spinning in the same direction from each other, but produce virtually no rotation when spinning in the opposite direction.

The planetary gear is there primarily to serve other purposes (shh) but being able to switch between torque and speed with efficiency (in the current layout, the motors on the ring gear input will have to be programmed to run at half speeds in order to obtain a 50% increase in torque in exchange for a halved rotational speed) would be a huge bonus.

I won’t have access to pictures for a while, sorry. It is similar in principle to murdomeek’s system.

How did you add a “lock” to prevent back driving?

from my understanding, it was just a screw stopping the chain
there is no proper way of stopping the backdriving, which is the only reason I don’t use them

I haven’t had any backdriving problems yet- does it only happen when the gears are set to torque?

How do you find the gear ratio of the planatary? I’ve found formulas and calculators online, but none of them take in account for the fact that two of the inputs are put in at once. Do I just add the gear ratio of the two inputs together (if the gears are set for speed)?

The backdriving problems will occur when you try to drive up against something, (when you try to push something). I can’t help you out on the calculating part, I don’t know myself.