FTC Tutorial
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Power Transfer

How to transfer rotational power from shaft to shaft


On this page we will go over the pros and cons of a few types of transfer,
Look at Idlers,
and talk about Gear Ratios.

A Warning for handlers

It goes without saying. Don't put your fingers in when these things move.
Failure to follow may result in loss of body parts, blood, and pain.

Types of transfer


Note that gears change the direction of motion
Precise transfer
Can be easily self designed for 3d printing (Fusion 360 tutorial)
Need to be meshed with precision


Long distances
Chain length can be adjusted
Imprecise transfer; A sprocket can rotate a bit without its counterpart
Will skip under heavy loads; Frequent cause of shudder

Timing Belts

Long distances
Precise transfer
Come only in specific sizes

Round Belts

Long distances
Distance does not need to be precise
Pulley angle does not need to be the same
Imprecise transfer; Will slip easily


Idlers are used to shift chains and belts.They are often used to tension the system (take up slack) or guide it (get around obstacles).
They can be used both inside or outside the chain/belt.
Best when freely rotating (has a bearing) and using the appropriate sprocket/pulley.

Gear Ratios

Also applies to gears, sprockets, and pulleys.
Driver gear rotations : Driven gear rotations
As a rule of thumb, less speed equals more torque (power)
The opposite is also true; more speed equals less torque, which means it gets easier to jam/skip/slip.
Here are a few examples
15-tooth driver gear and 45-tooth driven gear.
It will take 3 rotations of the driver gear to equal 1 rotation of the driven gear, therefore, the gear ratio is 3:1
40-tooth driver gear and 40-tooth driven gear
It will take 1 rotation of the driver gear to equal 1 rotation of the driven gear, therefore, the gear ratio is 1:1
25-tooth driver gear and 10-tooth driven gear
It will take 2 rotations of the driver gear to equal 5 rotations of the driven gear, therefore, the gear ratio is 2:5