Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

I would also note that round belts often slip when looked at cross eyed, even in nicely fitted grooves, for the above reason. A big part of that problem stems from packing oil fogged on newly manufactured items. The oil and water pump belts on the four cylinder inline I have are o rings, and folks complain they slip. Indeed mine slipped when new. I removed the belts, cleaned pulley grooves and the belts with windex, got them dry, end of problem once the o ring had some grip. Once dry, the reduced requirement for belt tension will make beatings and belts happier, and reduce parasitic losses. There is no longer a need to preload the belt much.