let's talk about flat (not leather) drive belts

That is right. Oil is not what they want (or need). They want precise alignment and a slightly (0.1mm or so) belly-shaped wheel to run on.

Nick

The most likely cause is that the pulleys are slightly mis-aligned. You can try adjusting the motor position (that's why the slots) or possibly adding a couple shims.

Also, flat belt pulleys should have a bit of a crown to them (the greater the crown, the more tolerant they are of mis-alignment).

However, one of the nice things about a flat belt is that it will come off if it is over-stressed, hopefully before something breaks. So, is it possible that the machine is turning way too hard?

Another possibility (rare) is that the belt has stretched unevenly so that one side is a tad looser than the other. Try reversing the belt and see if it tends to come off the other side of the pulleys.

Cleaning the oil, etc., off the belt is a good thing. Did you try putting some belt dressing on it?

Just a few random thoughts...

Jerry

Don't do it. It works by softening the rubber. I have worked on cars where instead of getting a belt adjusted the owner has used cans of dressing, making a nasty mess under the hood and ruining every bit of rubber under the hood. Clean it and align it. Soaps like Castrol Superclean and Simple Green will do well, but they are bad for Aluminum if not flushed out of the cracks.

Agreed! Been there done that.

In the limited space the only way to make the belt really tight is to adjust the motor with the belt off and then roll the belt on.

I'm sure.

I agree there. The manuals have a rather peculiar mix of either nothing you need to know, slight hints at other things, and completely skipping important stuff. It took me several hours to figure out how to change mine from 440 to 220 (had trouble finding the change over leads for the main motor).

You have that belt on TOO tight. Tighten just enough to prevent slip.

I don't think the belt is on too tight - what happens ( watched) is that the traverse encounters a stiffer than normal place (for example, raising the table at all), so the belt stops - this is because the motor pulley is smaller than the pulley entering the gearbox that drives the traverse, so there is less surface for friction on the motor pulley - anyway, the belt stops, the motor keeps running, and the belt just slides off the pulley.

the pulleys are properly cronwned - as nick said "belly shaped" - I think the problem is the oil, and maybe the age of the belt - I have no particular reason to believe that the belt has been replaced since the mill was new in

Wayne C - have you changed seals in the traverse gearbox? -- if yes, worth doing???

others - generically - glazed belt? versus new?

I put some water-based valve lapping compound on sepentine automotive belts occasionally to break the glaze on the pulleys. Sand on the roads here in winter turns to dust and embeds in belts.

We used a poly V belt (serpentine engine belt) flipped to run on the back side to replace the belt on mine.

I've not had the gear box out of mine yet. I need to since the rapid traverse clutch is iffy as to whether it will engage or not.

Gunner making notes as he schemes on getting his Abene home.

"[L]iberals are afraid to state what they truly believe in, for to do so would result in even less votes than they currently receive. Their methodology is to lie about their real agenda in the hopes of regaining power, at which point they will do whatever they damn well please. The problem is they have concealed and obfuscated for so long that, as a group, they themselves are no longer sure of their goals. They are a collection of wild-eyed splinter groups, all holding a grab-bag of dreams and wishes. Some want a Socialist, secular-humanist state, others the repeal of the Second Amendment. Some want same sex/different species marriage, others want voting rights for trees, fish, coal and bugs. Some want cradle to grave care and complete subservience to the government nanny state, others want a culture that walks in lockstep and speaks only with intonations of political correctness. I view the American liberals in much the same way I view the competing factions of Islamic fundamentalists. The latter hate each other to the core, and only join forces to attack the US or Israel. The former hate themselves to the core, and only join forces to attack George Bush and conservatives." --Ron Marr

I used to service equipment with a similar flat belt. They would go "bad" I didn't beleive it... At first. Get a new belt, and problem solved. No amount of tighter, looser, flipping of belts, or aligning would fix it, once the belt got out of whack. New belt, solved. YMMV. Good luck.