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I’m Bill Sawicki, National Account manager for Kaman industrial Technologies, with over 25 years of experience in the power transmission industry.
One of the issues I hear a lot from our customers is slippage of their chain drives. This causes premature wear, failure, and unplanned downtime.
Today, I will show you how to properly install roller chain sprockets, and the proper tensioning of roller chain. By following these steps, you can vastly extend the life of assembled drives, and ensure better performance of your power transmission system.
Installing and Tensioning a Chain Drive
For sprocket installation and tensioning, we’re going to use:
- two Martin roller chain sprockets, with set screws
- steel key stock
- roller chain
- a hex wrench
- a straight edge
- and a tensioning scale
First, we’re going to install the sprocket on the drive shaft. Then we’ll take our key stock, and insert it to lock the sprocket on the shaft. We’ll want to slightly tighten the set screws for now, then come back and tighten it more after we check the tension.
Next, we’ll install the second sprocket and insert the key stock to lock the sprocket on the shaft. We’ll slightly tighten the set screws, and then install our roller chain of the appropriate length.
Make sure the ends of the chain are lined up with the sprocket, and we take the pins and plate from our master link and slide them in the chain ends. Next, slide the plate over the pins and attach the clip to secure the master link.
Now we’re ready to check the chain tension. Excessive chain sag can cause vibration or excessive noise and prevent the chain from properly engaging the sprocket. This can prevent the chain from operating smoothly. On the other hand, an over-tightened chain can cause premature wear, or elongation of the chain and lead to increased replacement costs.
On the slack side of the chain drive, we’ll place our straight edge, from sprocket to sprocket. From the straight edge, we can use our tensioning scale to measure the amount of sag from the straight edge to the chain. For most applications, chain should be installed with sag from two to four percent of the sprocket center distance.
Once we’ve ensured proper tension, we’ll fully tighten the set screws on the sprockets and apply lubrication to the chain in accordance with the chain manufacturer’s recommendations.
A critical step in maintaining equipment with roller chain and sprockets is to routinely inspect drives for correct chain tension. You can also routinely inspect roller chain for elongation using a gauge which compares the true chain pitch to the original pitch.
Most chain manufacturers recommend replacing the chain after three percent elongation. After this amount of elongation, the chain rides up on the tooth sprocket, altering the pitch of the tooth. To ensure optimal part life and avoid unexpected down time, be sure to replace the sprockets each time the roller chain is replaced.
You can also consider options such as hardened sprocket teeth, which provides additional wear-life. This is especially helpful for driver sprockets, and when ratios exceed 3:1.
If you need any more information about roller chain sprockets, or alignment techniques, please contact your local Kaman representative. We have the product, and expertise, to help you avoid costly unplanned downtime.
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