Convex pulleys

[Hitch]

Having an issue with a belt drive, both convex pulleys, motor about 40mmø, driving a 120ø. Machine back gauge.
Shredded the belt a few months ago, so replaced with the same. Run it for probably a few hundred turns in one direction, belt stays central, reverse, and runs the same. Nice.

So I gather motor alignment is good if its staying central in both directions...?

However, it's thrown the belt a couple of times in the last month, but can't work out why.
No play in pulleys or bearings.
Pulleys are pretty clean.

Maybe I should just work a bit of coarse emery round the pulleys to roughen them up and put a drop of belt spray on it...

Any tips for these convex pulley setup

 

[brightspark]

not worn in the center is it leaving hardly any crown

 

[Pete.]

Crowned pulleys throw the belt if the power transmitted exceeds the amount of grip. My hobber does it on coarse pitches sometimes

 

[brightspark]

Crowned pulleys throw the belt if the power transmitted exceeds the amount of grip. My hobber does it on coarse pitches sometimes

a bit of belt dressing may help then

 

[Pete.]

a bit of belt dressing may help then

I used to use ordinary spray glue on my Monarch flat belt. A good long spray of it whilst the belt was running did wonders for the grip. It did get the better of me in the end and I ended up fitting vee pulleys.

 

[Hitch]

Crowned pulleys throw the belt if the power transmitted exceeds the amount of grip. My hobber does it on coarse pitches sometimes

Hm, I wonder. So if something makes it harder to drive, it's likely to throw it. Makes sense.

not worn in the center is it leaving hardly any crown

Nah, plenty of shape still.

 

[gaz1]

could be bearings jamming when hot ive seen a few via alternative sources that have jamed and shreded the belts

 

[Agroshield]

Could it be a bad belt (even though it is new)? Buy another to eliminate that possiblity and keep as a spare.

What centres are the pulleys at? If you can increase the wrap on the smaller pulley (with a flanged idler), you can increase the grip if it is marginal and help guide the belt at the same time.