Stationary Engine

Belting Issues

| January/February 2004

Stationary Engine

Last month, I mentioned the last sale of the season. And guess what? My collection has increased by one! The new one's a vertical Crossley VOE, a hot-bulb, single-cylinder engine that looks to be about a 6 HP, but is in fact an 11 HP, achieved by a pleasingly complicated air-scavenging system. Originally someone else's restoration project, this Crossley came to me in do-it-yourself assembly form - one large chunk of cast iron and several large containers of assorted parts. Thanks to the Internet, we had no trouble finding a complete manual to download and print out, which proved invaluable in putting the jigsaw back together. I know I've covered the subject of flat belts before, but it's the thing I get more 'please help' e-mails about than any other topic. I looked up the last time I mentioned belts, and it was 32 articles back, so I don't think I've overdone the subject - yet.

And that brings up the one thing we don't seem to be able to find on the Internet: belt dressing. If anyone knows of a source for solid sticks of rosin-based dressing, contact GEM so the information can be passed on to the engine-collecting world.

And now, on to the the discussion that attracted my attention this month on the Stationary Engine List:

On more than one occasion I've been asked at a show, 'What keeps the belt from slipping off the side?' - or - 'What keeps the belt on?' Can anyone give a simple explanation?

The simple answer is that the pulley's crown (center) section is traveling at a higher surface speed than its outer edges. The belt gravitates to the portion of the pulley that runs fastest. That's what keeps a flat belt on the pulley. If you made a tapered pulley and tried to run a belt on it, the belt would walk right up the taper and off the high side of the pulley.

I agree with what you're saying, but I don't understand why it will gravitate toward the larger-diameter, higher surface speed part of the pulley. It seems logical that the smaller diameter would be the path of least resistance, and the belt would drift to that direction.