Sprocket size for 1:1 gearing ratio

Suppose the gearing ratio must be 1:1, then is there an advantage in using two 30T sprockets compared to using two 6T sprockets? If there is, why?

Regarding power and speed, there’s no difference. However 6t sprockets are more compact and easier to manage. It just depends on what you need the sprockets for.


You have less torque with larger sprockets compared to smaller sprockets in a 1:1 ratio.

generally there is no difference, but from my experience the 30t sprockets have less slack on the chain and they have higher resolution since there are more teeth in use. but there aren’t many practical applications for high resolution in vex.

if your using sprockets to make a 1:1 chained drive, i’d personally use 30t sprockets because there are some techniques you can use to have a zero slack drive.

but if your making a drive with a ratio i’d something different

im not to sure about extra torque, but they would be more rigid


What do you mean “30t sprockets” and “larger 30T sprockets”
did you mean 6t sprockets on one of these?

whoops i wrote the 2nd part of sentence before the first

the 30t sprockets have less slack on the chain and they have a higher resolution

my grammar is so awful lmao

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How do I create a zero slack drive?

Proper tensioning using a free spinning spacer or 6 tooth sprocket idlers can alleviate slack without introducing too much friction. Geared drives are also an option.


Here is a paper with some general information about using chain and sprockets: Chain and sprocket systems.pdf (118.6 KB)


I would avoid the smallest 6T sprockets for anything that transfers full 1 or 2 motor’s worth of power.

For transferring the same torque, smaller sprockets need larger linear force (torque=radius * linear_force) and, therefore, you end up with larger force of axles pushing on the bearings and, as a result, larger friction losses on both sides.

For 1:1 power transfer, try to use at least 12T or 18T sprockets.

If you have to implement specific gear ratio, and there is absolutely no other choices but to use the smallest sprocket then you have to be aware of the potential friction losses and pay extra attention to the build quality, proper axle alignment, and lubrication of the bearings to minimize the power losses.


There are also teams that have used 24 tooth sprockets very successfully on their drivetrain. These don’t really have a huge advantage over the 18 tooth sprockets, but if you want to try it go for it. The difference between 18 tooth and 12 tooth sprockets, however, is more noticeable. 6 tooth sprockets, on the other hand, have a huge drop off from 12, and the discrepancy becomes even more apparent when compared with a 18 or 24 tooth sprocket. In short, use the largest sprocket possible until you get to the 24 tooth, where things like weight may become a more important factor than small efficiency gains.

Could you please point out the performance difference between them? I never notice anything (then again, I’m not very observant).

In industrial design, we never (or rarely) use a sprocket with less than 17 teeth as a drive sprocket, and usually not for the driven sprocket either. It has a little to do with lever-arm (reducing the load in the chain), but mostly, it has to do with the flow of the chain around the sprocket: as the tooth number drops below 17, the chain binds and hangs-up on the sprocket teeth. Sprockets with less than 17 teeth are intended for guide and idler use, mainly.


Printing this (and the pdf above) and handing it to my students building a cascade lift with 6 tooth sprockets. I cringe every time I look at it. TY