Whats the difference between first 970 and 9070s with 1200-1250 rotor speed compared to newer ones which have 1300-1350 if i recall right. Did they just remove shims from the hydraulic piston on the sheave or is there different parts?
As of yesterday afternoon I can answer this.
A change in shaft speeds for other reasons lowered max rotor speed.
The drive did not change.
The new 90/70/80 max at approx 1500.
Not sure on the 9090, it has a different drive.
The drive is different. The 07 (and 970s) will have a 4 rib separator belt, while the newer ones have a 5 rib. I assume this is where they got the higher speed on the newer ones, but have not measured it. We do have trouble with the 4 rib belts. They seem to be a yearly fuse.
Would not spacing the separator main shaft (comes from the ribbed belt on the right side to the rotor drive pulley) further toward the front of the machine do the same thing as a shorter belt? One could build shims from 3/8 or 1/2 inch flat metal to move the bearing mounts forward, doing the same thing as shortening the belt. It would allow the belt to run in the same position on the drive pulley, but further down in the driven pulley (faster speeds). One would have to watch belt wear and slippage with used belts since they might be too thin for max speeds.
Anyone think it would work? Ideas on how many RPM it might net?
There are 4 or 5 plastic washers or shims on the rotor drive. You find these when you take the hydraulic part off the drive. For every shim or washer (whatever you call them) that you take out you get more rotor speed. However you don't get a lot. It is something that you might want to do if you plug but make sure to keep one in, they have a purpose.
I looked at those shims you can see, but i think the book said those are for adjusting the low speed or how far that piston can come back. Is there also shims in the insided by that cylinder? I didn't see them in the breakdown.
Yes, I believe your correct, the shims only set minimum rotor speed, maximum is still determined by by the sheaves closing together.
Even if you add shims the cylinder still has plenty of stroke to bottom the sheaves.
The stroke length of cylinder is not adjustable.
Your best hope is if you can track down one of those shorter belts referred to earlier.
The thing is, all the drives are attached with belts that have spring tensioners. At most, the lower bolt holes on the bearing holder would have to be slotted, and beyond that it should all work out. Maybe...