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
Sprocket replacement
Sprocket replacement
An optimist is usually wrong, and doomed to disappointment. he is unprepared. A pessimist is usually right, delighted to be wrong, and is well prepared.
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
Lavoy
Parts and restoration for antique and late model John Deere crawlers.
Owner and moderator www.jdcrawlers.com
Owner and moderator www.jdcrawlers.com
- Stan Disbrow
- 350 crawler
- Posts: 2898
- Joined: Fri Jul 15, 2005 3:13 pm
- Location: Raleigh, NC
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
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
There's No Such Thing As A Cheap Crawler!
Useta Have: '58 JD 420c 5-roller w/62 inside blade
Useta Have: '78 JD350C w/6310 outside blade
Useta Have: '68 JD350, '51 Terratrac GT-25
Have: 1950 M, 2005 x495, 2008 5103 (now known as 5045D)
Useta Have: '58 JD 420c 5-roller w/62 inside blade
Useta Have: '78 JD350C w/6310 outside blade
Useta Have: '68 JD350, '51 Terratrac GT-25
Have: 1950 M, 2005 x495, 2008 5103 (now known as 5045D)
- Stan Disbrow
- 350 crawler
- Posts: 2898
- Joined: Fri Jul 15, 2005 3:13 pm
- Location: Raleigh, NC
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
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
There's No Such Thing As A Cheap Crawler!
Useta Have: '58 JD 420c 5-roller w/62 inside blade
Useta Have: '78 JD350C w/6310 outside blade
Useta Have: '68 JD350, '51 Terratrac GT-25
Have: 1950 M, 2005 x495, 2008 5103 (now known as 5045D)
Useta Have: '58 JD 420c 5-roller w/62 inside blade
Useta Have: '78 JD350C w/6310 outside blade
Useta Have: '68 JD350, '51 Terratrac GT-25
Have: 1950 M, 2005 x495, 2008 5103 (now known as 5045D)
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
Willie
An optimist is usually wrong, and doomed to disappointment. he is unprepared. A pessimist is usually right, delighted to be wrong, and is well prepared.
Who is online
Users browsing this forum: No registered users and 116 guests