Sprockets & Chain
Sprocket & Chain Basics
Common Terms
Pitch is the measurement from one roller chain pin to another. Popular chain sizes used throughout FRC are the #25 and #35, which have their respective pitches of 0.25" and 0.375"
Pitch Diameter also known as PD is the circle that is formed while the chain and sprocket are meshed together and which the chain rotates around. If you wish to find the PD, reference the formula below.
Pitch ÷ sin(180°/Tooth Count)
The Chain Clearance Diameter is the outer diameter of the sprocket while it is meshed with the chain. Knowing this is crucial when placing sprockets in tight places to ensure that no interference is being created. If you wish to find the Clearance Diameter, reference the formula below, along with an example equation for the sprocket shown above.
Pitch Diameter + Pitch
24T - #25 Sprocket
1.915 + 0.250 = 2.165
The Outside Diameter also known as OD refers to the size of the actual sprocket.
Calculating Center to Center
When deciding the placement and spacing of your sprocket and chain it is important to keep in mind that the Center to Center distance can be a fully custom measurement to ensure compatibility in your system, or can be decided through a pre-determined chain length.
The basic rule of thumb when deciding on a custom Center to Center distance is that it should be anywhere from 30-50 times the pitch of the desired chain for optimal usage and should not exceed 80 times the pitch.
Proper Tension
The examples below highlight different levels of chain tension, including chains that are too loose, too tight, and the recommended amount of slack for reliable performance in any subsystem.
An under tensioned chain can lead to inconsistent power transmission, causing the chain to skip teeth or derail from the sprocket entirely. This results in unreliable performance, excessive wear on both the chain and sprockets, and potential damage to surrounding components. Loose chains can also introduce backlash, reducing precision and control in your mechanism.
An over tensioned chain puts unnecessary stress on the chain, sprockets, bearings, and shafts. This added tension increases friction and wear, leading to premature failure of components. It can also reduce system efficiency by making it harder for motors to spin freely, ultimately impacting overall robot performance and reducing the lifespan of key parts.
A properly tensioned chain maintains just enough slack to allow smooth rotation while staying firmly engaged with the sprockets. This reduces wear on bearings and shafts, minimizes friction, and ensures reliable power transmission. With the right tension, the system runs efficiently, components last longer, and the risk of skipping or binding is greatly reduced. Resulting in consistent, high-performance operation.
Adding Chain Tensioner
Ensuring that proper tension is present in a sprocket and chain system is crucial for the sake of system integrity and performance. Achieving proper tension is a fairly simple task to do when using a chain breaker tool and tensioner offered through WCP. Such as the Spartan Chain Tensioner or the Chain TurnBuckle.
Implementing our chain tensioners into your system is a an easy task due to them having the necessary clearance holes for the roller pins. Use the chain breaker tool to partially remove the pin from the chain and lay your selected chain tensioner in place, then simply reset the pin back into place.
Idlers
Idlers are yet another way to ensure proper tension is present in a chain and sprocket system as they can be placed either on inside or outside of the chain loop to provide more contact with the sprocket and decrease slack. Adding an idler to the chain loop does not affect the ratio and can actually benefit performance if placed near the driving sprocket as it allows for more meshing.
Recommended Applications
#25 Chain
Intakes
Conveyors
Turrets
#25H Chain
Drivetrains (wheels under 6")
Intakes
Conveyors
Turrets
Elevators
#35 Chain
Drivetrains (wheels 6" and up)
Wrists/arms
Load Rating
#25
154 lbs
1058 lbs
#25H
209 lbs
1146 lbs
#35
419 lbs
2601 lbs
#25 Sprockets and Chain
Using this popular combination to transfer power or torque is a great alternative from other solutions due to the light footprint it has on your robot.
Plate sprockets are 6061-T6 aluminum
Hub sprockets are 7075-T6 aluminum
#25 and #25H Chain
Roller Chain in 10 foot lengths for use with any #25 sprocket
Available in #25 Standard and #25H
ANSI standard
Master Link included with 10 ft purchase
Chain Break Tools available to easily separate chain
Additional Master and Half Links sold in packs of 5
Motor Pinions
8mm Spline XS
10, 12
8mm Key/Falcon
10
Double Hub Sprockets
1/2" Hex
12*, 14*, 16*, 17, 18, 20, 22, 24
*12T and 14T sprockets are only available in steel. The 16T is available in steel and aluminum.
Chain in Tube Sprockets
1/2" Hex
16, 17, 18
Single Hub Sprockets
3/8" Hex
16, 18, 22
1/2" Hex
18
Plate Sprockets
Depending on the size, the Plate Sprockets will now have the MotionX Pattern and as many additional holes as possible following the 1" pitch.
SplineXL
24, 30, 36, 42, 48, 54, 60, 66, 72, 84
#35 Sprockets and Chain
Using this combination to transfer power or torque is a great alternative from the #25 solutions as it can sustain double the working load and tensile strength.
Plate sprockets are 6061-T6 aluminum
Hub sprockets are 7075-T6 aluminum
#35 Chain
Roller Chain in 10 foot lengths for use with any #35 sprocket
ANSI standard
Master Link included with 10 ft purchase
Chain Break Tools available to easily separate chain
Additional Master and Half Links sold in packs of 5
Double Hub Sprockets
Aluminum
1/2" Hex
12, 15, 18
Steel
1/2" Hex
9, 12, 15, 18
Plate Sprockets
Depending on the size, the Plate Sprockets will now have the MotionX Pattern and as many additional holes as possible following the 1" pitch.
SplineXL
18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 84
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