Uses

Chains transmit power across a long distance. Movement is transferred between two parallel shafts which are any distance apart. Chain is flexible in one dimension, meaning that it cannot elongate or twist side to side.

Chain is typically run at relatively low speeds, up to about 800 ft/min (Chain Speed). At higher speeds, gears are preferred as chain becomes quite loud.

Advantages

• Simpler & Lighter than gears for longer distance runs.
• Require less precision than gears.
• Easy to change reduction ratios by changing sprocket sizes and re-running chain.

Chain Terms

One Chain Link is one individual unit of chain.  The chain contains alternating inner and outer links.

Rollers are the round pins which act as pivots between chain links.

Plates are the metal plates holding the rollers together.

Pitch is the distance between round rollers on a chain.

Sprockets are profiled wheels with teeth which chain wraps around.  The teeth allow engagement between the chain links, with the teeth pulling directly on the rollers. Sprockets can be on a live axle or can be bolted to a wheel in a dead-axle configuration

Designing for Chain

When designing for chain, it is usually important to design in some sort of chain tensioner.  Team 254 prefers using a cam which shifts a bearing block to tension the chain without adding any additional friction to the chain.  Other options, such as placing idler sprockets or low-friction plastic blocks in the chain run are other possibilities.

The calculator in the blue box below can be used to calculate the distance needed and the number of links needed for a certain chain run.  Simply fill in the boxes and the remaining boxes will be filled in automatically.

Chain Sizes

The two most commonly used chain sizes used in FIRST Robotics are ANSI #25 and #35.

ANSI #25 Chain

• Pitch: 0.250"
• Roller Diameter: 0.130"
• Tensile Strength: 781 lbs
• Working Load: 140 lbs

#25 chain is more than strong enough for most robot applications, and is used often by Team 254. However, due to its small size, #25 chain is very sensitive and must have proper sprocket alignment and tension to function properly.

ANSI #35 Chain

• Pitch: 0.375"
• Roller Diameter: 0.200"
• Tensile Strength: 1758 lbs
• Working Load: 480 lbs

#35 chain is often used by Team 254 for raising large arms and other high load bearing applications. Furthermore, #35 chain can handle much greater forces and much looser tolerances than its smaller counterparts. For teams who are not confident about achieving proper alignment and tension, #35 chain is often a better solution.