Yair . . . What would be the criteria used to determine the idler diameter on Hi-tracks? To my eyes they always look "out of scale" and on the small side . . .I have heard certain models "scallop" rails which is what would be expected if a chain was running at those acute angles around a tight radius. Just wondering, that's all. Cheers.
When I had my D6H , it was routine to have to change idlers ever so often. The rails seemed to scallop because it had 2 idlers to run around. I would use rebuilt CAT idlers with a 1500 hr warranty which they pro rated. Kind of a joke. I can't recall if the flat track units I been around scallop or not.
I'm sure the engineers make them as small as reasonably possible, probably so that at 100% or so worn they're the tightest diameter the track in good nick can bend around without the links binding? Smaller saves weight and space, maybe saves a link or two in track chain length? The oval track machines they just pretty well matched the sprockets eh?
I know nothing of it. I wonder if in oval track machines there is a constant discrepancy between track chain pitch, and sprocket pitch. These machines might have 9 teeth engaged at a time. A discrepancy of 1/8" pitch difference will multiply by 9. The high drive machines benefit from fewer teeth engaged, the difference is less severe.
As a rule you only have two or three teeth pulling anyway, the rest are along for the ride due to normal slack in the system. As you say though contact time is probably lessened reducing wear somewhat.