I don't have a whole lot of experience with these but I've never seen one anything like this. How is it possible it wore off every other tooth?
That is caused by the track chain stretching. When the individual links stretch, or the pins in between wear, they no longer match the distance between the sprocket teeth and will wear down every other one. By this same principal it is also common for dirt bikes to break every other tooth off of the sprocket. This is one of the more extreme examples I have seen on a piece of equipment though.
That makes perfect sense, thanks for the explanation. Could it also be caused by running the track extremely loose? I know this machine has had a problem with the track tensioner for some time. It's amazing how much more wear there is on this side of the undercarriage compared to the other.
What machine is this??
It is much more likely to be from the track being too tight. Too much tension on the track will cause accelerated pin wear and stretch the links.
I suspect the chain was shortened because of wear - if you get a situation wear the # of chain links is divisible by sprocket teeth , the bushings hit every other tooth so same teeth always wear
That looks like an old excavator sprocket. I suspect the chain has been worn out for a very long time. Probably has many broken bushings and I'll bet the front idler support blocks are out the end of the track frame. Really at this point it doesn't matter what caused it. It is so far past its useful life that who would even care?
sprocket Yep,they got the last dollar out of that one.Looks like a 200 series Cat sprocket.
It's an old 235c cat excavator. I was just curious what caused it because I would assume if the sprocket was replaced the new one would wear the same way in a short amount of time unless the problem was corrected.
Correct!
I'm sure this is the answer here. There is never supposed to be both sprocket and chain with both even or both odd numbers.
The number of links and the number of teeth will not make a difference in wear as long as the space between the pins is correct. I worked for a company that removed a link from one track of thier excavator to shorten it. Almost all of the operators swore up and down that having a shorter track on one side would make the machine turn when it walked. Afterwords the machine walked as straight as ever.
The chain will Lengthen because of wear, not shorten. Either way it will have the same effect and cause the pins to no longer line up with the teeth resulting in the wear you see in the photo.
I think he means somebody took out a link, thus changing the ratio of bushings to sprocket teeth. This causes the sprocket to pull with the same teeth every time and half the teeth to never touch a bushing.
I think he means it stretched to a point it could no longer be tightened, so it was shortened by taking out a link or two.
Ok I gotcha, either way the number of links will have no effect on sprocket wear, the only thing that matters is the distance between the pins.
Hey Jerry, don't you hate when somebody else is typing the same thing at the same time and makes you look like a copycat? Mitch
When you remove a link the same same sprocket tooth will hit the same bushing every time it comes around. I'm not saying you're going to see much of a wear difference if the pitch length is correct but eventually there will develop a wear pattern. If the pitch is incorrect with a lot of stretch, I think the pattern will be much worse. My 2 cents anyway.
apparently I was not clear enough - I assumed you all could see the sprocket had been " Worn to Destruction" and pins and bushings were probably in similar condition Try looking up hunting tooth sprockets, non hunting tooth sprockets A lot of old machines - a lot of them Cat and International models, used a design where bushing hit every other tooth . when you turned pins and bushings you moved contact to the unused part of of sprocket as far as wear goes it was found to be a lot better to use the whole sprocket
:Banghead Yea, I just seen that. I guess good minds think alike. My problem is i open several threads, then browse through them, so if there is a new post, I will miss it sometimes. Back to the U/C at hand though, and I bet the pins and bushings are in every bit as bad of shape. Certainly got their moneys worth out of them.
depends on if it is a even or uneven tooth sprocket or hunting or non hunting meaning if it hits or runs on every tooth or every seconde tooth. it does not matter how maney links you remove or add out of a chain it will not change the wear pattern on the sprocket
wear start from the bushing and pins (track link chains), worn bushing and pins cause to change the pitch of chain, if the pitch of chain and sprocket is not match, it cause to high impact between the pin and sprocket and sprocket start worn out
So 951 C which used a 30 tooth sprocket ( 4v5390 ) (7k3990), a d6 B 28 tooth sprocket (8m6041), A D7 & 977 H ( 3s7090 ) all these skip a tooth because they have a even number, by your explanation
Regarding the photo of that worn sprocket, has anyone considered the fact that chain and sprockets in that condition must place considerably more load and shock on the drivetrain. Looks pretty nasty.
To use a simple example a 20 tooth 60 link should work out the same as a 33 tooth 99 link
The way I am thinking is that since the sprocket only contacts the bush on every second half round, (the bit in between each tooth), the only way it can use every half round/tooth is to have an uneven number of teeth. There should be no relation to the number of links regarding the teeth use as every bush is used when driving the tracks, but only every second tooth. Hypothetically a 5 tooth sprocket would contact tooth 1-3-5-2-4-1 etc a 6 tooth sprocket would contact 1-3-5-1-3-5 etc Hope I got that right:beatsme Baz
No it is the # of teeth to # of links for example 10 teeth to 20 links ,30 links , 40 links 11 teeth to 22 links , 33 links 44 links 22 teeth to 44 links , 88 links 27 teeth 54 links Those are simple examples of what I am trying to explain I believe 235 came with either 47 or 54 links but I do not remember how many teeth came on the sprocket perhaps somebody will post this and we can figure what numbers would work If it had a 47 link chain with one linked removed and used a 23 tooth sprocket - this wear pattern could result as I said earlier i do not remember how many teeth a 235 has ,this is an example
The Cat 235 came with a 24 tooth sprocket and should have a 49 link chain. Which is a even # of teeth and an odd # of links. Keep this in mind. The JD 450H comes with a 25 tooth sprocket and has a 37 link chain but the 450H LGP comes with the same 25 tooth sprocket and has a 40 link chain.
After studying that sprocket for a while, I feel that the wear on it is consistent with my theory that an even toothed sprocket will not have bush contact on every second space on the sprocket although it will have contact with one side of every alternate tooth. On an even toothed sprocket it will wear one side of the tooth on every alternate tooth going forward and the other side of every other alternate tooth in reverse. Since reverse has a higher wear factor than forward, that would explain why every second tooth is still standing. Still, I could be wrong.:beatsme Baz
you really need to do a search on hunting and non hunting tooth sprockets as you appear not to understand it
Found this on a search. From Antique Caterpillar machinery owners group "Teeth Count the number of teeth,even number of teeth no hunting tooth,uneven number hunting tooth,with an even number of teeth the chain bushes run in the same teeth all the time and as the chain bushes runs in every second tooth it means that the teeth in between go unused,with an uneven number the bushes alternate from the even to the uneven each revolution and all the teeth gets used,look at the clock face and start off at 1 and miss 1,so it goes 1,3,5.7,9,11,1 but if you have an extra tooth it would go 1,3,5,7,9,11,13,2,4, etc,the 951s are few and far between now,I do remember the change in the pitch but the sprocket still had 30 teeth,I cannot recall any with a tooth more or less but dealing with all makes of machines it hard to remember what was on what. AJ " I do understand the principle of hunting and non hunting. It generally refers to gears where every tooth meshes, and whether or not the same teeth on both gears mesh together every time or more randomly. Track chains are a little different because due to the link having the bush two teeth apart only every second tooth drives. Sprockets are defined as hunting or non hunting as above depending on even or odd number of teeth. The amount of links in the track chain will also effect whether or not the bush always contacts the same tooth consistently or keep changing until it returns to the original tooth bush combination once every however many times the track needs to rotate to complete the pattern. There is as you point out a correlation between the number of teeth and the number of links, but only a sprocket with uneven teeth will use every tooth on both sides. Baz
so explain why these machines wear every tooth - they all have a even # of teeth 951 C which used a 30 tooth sprocket ( 4v5390 ) (7k3990), a d6 B 28 tooth sprocket (8m6041), A D7 & 977 H ( 3s7090 ) all these skip a tooth because they have a even number, by your explanation
That is correct, They do skip a tooth, but the thing is that they wear the front side of every second tooth going forward and the back side of every other tooth going in reverse, so in effect they still wear every tooth, but unlike a hunting sprocket that wears the front and the back of every tooth. Baz
The point is that having an even or odd number of sprocket teeth does not make it hunting or non-hunting. It is weather both the number of link bushings and the number of sprocket teeth are either even or odd numbers will make it non-hunting. If the number of bushings is even and the number of teeth is odd it will be a hunting system. Different brands and models could do it either way. I thought all machines that do a lot of traveling were hunting.
These machines ARE HUNTING TOOTH If you think bushing has to engage every tooth on every cycle you are wrong. Bushing would engage half of the teeth on one cycle then half on the next sprocket cycle (referring to bulldozer track systems
You seem to be doing a better job than I at explaining this I had thought the original question was a matter of experience requiring a simple quick answer - but I was very mistaken
Although I see where you are coming from here as to the relationship between the sprocket teeth and the number of links giving you a hunting ratio, what we are discussing here is that for a sprocket with an even number of teeth, it is a mathematical impossibility for it to use both sides of every tooth when only very second tooth contacts the bushing of the track chain. Test it out on a machine that has an even number of sprocket teeth. The space that sits in the middle of the link will never make contact with a bush on a sprocket with an even number of teeth. BTW, if you google "Hunting tooth sprockets" you will see that Berco describes a hunting tooth sprocket as one that has an uneven number of teeth. So the term "Hunting" can be used to describe the sprocket without any relationship to the chains being mentioned. Baz
You seem to want to ignore this as does not fit your theory
Also 955 F , 955 H used a thirty tooth sprocket , yet when sprockets are changed every tooth is worn. You mentioned a 951 as being old and uncommon - how does that change anything ? if its old and does not work for your theory do you just discount it? You say its impossible - but these machines are proof of what I am are saying So what is going on ? Do you consider this a debate that what is right or wrong does not matter , just what sounds better ? or if you post your theory enough times it will be be accepted as correct? In the beginning I had thought you just did not get it- know I think your just tweaking
Please re-read post 33
I now understand why lions eat there young
OK so here it goes: A even number of teath in the sprocket, means every second teath wears down all the time. A uneven number will make the sprocket last twice as long. A even number of links in the chain, means the chain is worn only on every second bushing. A uneven number of links in the chain, means the chain is worn on every bushing. Longest lasting system is a uneven sprocket, inside a uneven chain
The sprocket will wear one side every second tooth in one direction and the other side of every alternate tooth in the opposite direction due to the tooth on one side of the bush driving in forward and the one on the other side driving in reverse. Every bush (link)is used traveling forward or reverse even though one tooth is skipped on the sprocket per bush . Baz