CPP machined sheave

[grantspec]

Bought a brand new machined sheave from CPP. Was a little surprised when I opened it and it looked less like it was machined and more like they took 60 grit sandpaper to it including the face where the belt rides.

I guess the messy surface really doesn’t matter but I was a bit surprised at the “machining” quality. Thoughts? Will delete if you guys think it’s no big deal.




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[TheNewGuy]

Looks good!! Where the belt rides did not get machined, the face at the seal is what was cut. They may have sanded the entire face. The belt will grip well.

[Field6565]

Originally Posted by TheNewGuy

Looks good!! Where the belt rides did not get machined, the face at the seal is what was cut. They may have sanded the entire face. The belt will grip well.

So all they do is cut the bottom of the sheaves to ride closer together?

[TheNewGuy]

Originally Posted by Field6565

So all they do is cut the bottom of the sheaves to ride closer together?

That is the only way it's going to happen. Machining the sheave angle would do the opposite and more over, weaken the sheave. Bringing them closer together increases the diameter and will make the belt ride higher. You gain a bit more low end, noticeable on takeoff. I have machined several over the years, every little bit helps.

[Field6565]

Originally Posted by TheNewGuy

That is the only way it's going to happen. Machining the sheave angle would do the opposite and more over, weaken the sheave. Bringing them closer together increases the diameter and will make the belt ride higher. You gain a bit more low end, noticeable on takeoff. I have machined several over the years, every little bit helps.

I'm going to have my secondary apart in the morning. Maybe I should do some work on my sheaves. I'm gonna have to be careful though, if I take off too much the belt will act like it's short. I suppose if that happens then I can shim it back.
Yeah I was always under the impression that the sheave faces were machined at different angles. I see now what's done to them. Thanks for the help Ron.

[TheNewGuy]

Only the aluminum sheave is machined.

[slonomo]

Sanding the face of the clutch takes of the glazing from the old belt rubbing on it for years. Think brake rotor/disc. You don't want a smooth shiny surface. You don't want deep grooves. You don't want wavy surface.

On a new clutch, using a rough sandpaper takes all the factory shiny off and allows the rubber belt to have some bite. Sometimes new clutches have a directional machining surface. Most brake rotor/drum machines have an attachment that "burnishes" the surface after machining and gives it a non directional finish. That's what you're seeing there, a "non directional finish". Every new clutch I've ever installed I do the same thing with some 100 grit paper. I sand in all directions, just enough to take the machining marks off. You also don't want a polished surface for clutches, this will allow the belt to slip. Over time the belt will polish the surface of the clutches. When I change belts, I scuff the surfaces of the clutches lightly.

Some may disagree with this. Most don't do it and it usually works out fine. Might even be overkill. But I do it this way.

[slonomo]

Ron, doesn't that also allow the belt to ride lower in the clutch for more top end?

[TheNewGuy]

It may help a bit but I believe there is more to gain on the low end. The belt should bottom out if the clutch is opening all the way.

[slonomo]

Originally Posted by TheNewGuy

It may help a bit but I believe there is more to gain on the low end. The belt should bottom out if the clutch is opening all the way.

Thank you sir