Breaking, Measuring, and Adjusting Chain ~The most used drive system on a FIRST robot uses chains and sprockets. Understanding the proper techniques to “breaking” chain, installing master links/half links, and measuring chain will speed up build process and ensure a durable drive train during competition.

Breaking Chain: Breaking chain simply refers to the process of separating links in order to achieve desired length. Chain links should NEVER be separated using anything but a proper chain breaker. An example of a chain breaker is shown below (↓). Insert the jaws of the chain breaker directly on the sides of the link pin with the piston of the chain breaker facing the top of the pin. Gently tighten the chain breaker by turning the handle clockwise. The piston will force the pin ¾ of the way out. Then place the chain breaker on the second pin of the same link. Force that pin out and the link will be loose enough to remove by pulling on the link, separating it from the rest of the chain.

Measuring Chain After installing all sprockets in the correct position, place a length of chain on the sprockets. Pull the chain tight and mark the link that the end of the chain reaches. This method is effective for most applications. Adding a chain tensioning device, such as an idler sprocket, will further guarantee a durable drive system. Be careful not to tighten the chain too much because the chain may break. Proper chain tension is usually determined by pressing down on the center of the chain ( furthest point between sprockets). The chain should flex down at least 1/8 of an inch when moderate pressure is applied. If the chain does not move at all, then either remove a link or adjust the tensioning device.

Installing Master Links Master Links are used to connect chain back together after separating it with a chain breaker.A master link is shown below (↓). -Insert the link (middle object in above picture) into both ends of the chain. After sliding the link through, place the spacer (right object in above picture) flush on the link, making sure both pins are inside the spacer holes. Then, place the wider end of the clip (left object in the above picture) on either pin with the tips of the thinner end resting against the other pin. Notice the small groove. Then, finally take a pair of pliers and force the sides of the thinner end around the pin, locking it into place. Move the chain around and pull on it a few times to ensure the master link has been placed correctly. If any part of the chain is bent or damaged, the master link will prove difficult to install. Simply discard any damaged parts and continue the process.

Installing Half Links - Half links are used when removing a whole link makes the tension too tight and adding a whole link makes the chain tension too loose. A half link is shown below (↓). -Slide the open end of the link (left object in the above picture) over the desired chain link, lining up the holes. Then, insert the pin ( middle object in the above picture) through the holes. Slide the supplied cotter pin ( right object in the above picture) through the hole in the half link pin and spread the “legs” of the cotter pin in opposite directions to secure the half link. Then, finally use a master link to attach the closed end of the link, completing the chain.