How to Choose the Right Roller Chain Sprocket?
Roller chain sprockets transmit power between the shaft and the roller chain, so these two components point you in the direction of the right one for you.. The shaft’s contribution to sprocket specs is the bore size: the diameter of the shaft determines the bore size of the sprocket. The chain pitches in with, well, the pitch diameter. The pitch diameter is the sprocket-level view of the pitch of the chain, which is the distance between consecutive pins. Together, these two specs ensure that the roller chain sprocket gets a good “bite” on the chain.
Everything in a mechanical drive chain is both a cause and an effect, is both upstream and downstream of other components. That perspective extends to component design and selection, and how specs are all interrelated.
The pitch diameter, the sprocket’s diameter and the number of teeth on the sprocket all play off of each other. Change one, and you’ll have to change the other two. When actually designing a system, then, one component needs to be held constant so you can determine the other two.
The sprocket’s diameter is usually the most important of that trio, as the location and role of the sprocket in the system will influence the others. At the most basic level, the amount of space available for the sprocket in the system will set the upper boundary for how much space the sprocket can take up.
The driven sprocket – the one on the downstream end of the transmission – is usually larger than the drive sprocket. Knowing at which end of the chain, so to speak, the sprocket is going to go will help determine at least the relative size of the sprocket you need.
The relationship between the characteristics of the driven and drive sprockets also comes through in the sprocket ratio, which is the number of teeth on the driven sprocket over the number of teeth on the drive. Like a reduction ratio in a geared system, the sprocket ratio can be manipulated to change the RPMs of the shaft running through either sprocket, which affects system speed, torque and efficiency.
Zooming out a bit, we can see a few other decision points as you select the right roller chain sprocket.
So far, we’ve assumed – or at least implied – that the sprocket has a single set of teeth, also known as a strand. But one sprocket can have multiple strands that act upon an equal number of single-strand roller chains, or a combination of single- and double-strand roller chains. Once again, the design characteristics of your chains will constrain or determine your choice of sprockets.
You may also have been thinking about the most familiar sprocket and chain tandem: a bicycle’s. If that’s case, you’d have been thinking about a Type A sprocket. Type A sprockets are just a disc with teeth. Type B sprockets have a hub on one side surrounding the bore; Type C have a hub of equal thickness on both sides; and Type D sprockets have a hub on both sides, but one hub is larger than the other.
The last “macro” factor we’ll bring your attention to is the material the sprocket is made of. Most sprockets are steel or plastic. A common variation is a plastic sprocket with a steel insert on the bore. That way you get the lightness of the plastic with the durability of steel surrounding the shaft.
With all this in mind, you’re most of the way there to finding the right roller chain sprocket. To ensure you finish the job of selecting the right equipment so you can get on with the job of mechanical power transmission, get in touch with us today and we can work through the last few criteria in sprocket shopping. Or, if you know exactly what you need, head over to our product pages where the right roller chain sprocket awaits.
