Sprocket replacement

[Willie B]

As undercarriage wears, the gullets in the sprocket wear deeper, this reduces the diameter, and circumference of the sprocket. The sprocket distance between pins gets smaller.

Meanwhile, the chain wears, and the distance between pins grows. Moving forward, all the strain on the track is concentrating in the first pin. the rest of the way around the sprocket, the track is slack. New sprockets would reduce the discrepancy between sprocket pitch, and chain pitch.

Is it ever done to replace sprocket before the chain is spent to avoid some wear on the chain?

Willie

[Lavoy]

Not really, the sprocket and chain tend to wear together, so kind of a waste of money. Not saying it isn't done, but doesn't make a lot of sense to me.
Lavoy

[Stan Disbrow]

Hi,

This would address only half the wear. The OD of the bushings and the sprocket teeth. It would do nothing about the wear on the ID of the bushings and the OD of the pins.

A better approach would be to lessen the entire wear rate by limiting the amount of reverse used. Reverse being wear on all the points where the chain meets the sprocket as opposed to only the first couple of teeth when moving forward.

Stan

[Willie B]

I can't really wrap my brain around why reverse is worse than forward. Could you explain?

Willie

[B Town]

We try to maximize the use of the front and back of the bushing/sprocket . We push hard going forward and walk distances from job to job in reverse

[Stan Disbrow]

Hi,

In reverse, the force is on all the sprocket teeth engaged because you are pulling the track from the top. In forward, the force is on the first two teeth because you are pulling the track from the bottom.

The wear mostly occurs when the chain has to make the turn under load. So, there is a turn at the top and bottom in reverse and only on the bottom in forward (there is very little force at the top in F, so for practical purposes it doesn't add to the wear).

Now, on a dozer, it isn't so bad as they move forward loaded and reverse unloaded. So, the total force is less in R than in F. But, a loader is used loaded in both directions, and that load is heavier than a dozer even in transport.

For more on all of this see:

http://www.tpaktopc.net/files/undrcarguide.pdf

Stan

[Willie B]

The concept of there being a lot of tension on the chain in reverse having to pull it around the front idler certainly makes sense. As there is nothing to hold the bushing deep in the gullet I get the notion of it riding up to the tooth where it strains on the tip where it is weakest, and there is little surface contact. A convex surface, on a convex surface. The 30 degree rotation as the chain link begins the rotation around the sprocket happens at the bottom also, does it not?

Willie