Looking for source for 1/2 inch wide MXL timing belts

Breco can supply urethane/steel XL pitch belts up to at least 1" wide, but I've never seen one as short as 4.8", if that's what the 48 in your number specifies. $50 minimum, IIRC, though you may be able to get around that by going thru Motion Industries, etc.

You're correct that 2 narrow belts will not be as good as a single belt.

Ned Simmons

Why? Load sharing? Multiple belt drive setups seem to be common with aircraft homebuilders. Claim is, of course, redundency.

Ted

I'm not sure I've ever actually seen it spelled out, but for the urethane/steel belts at least, I've always assumed it's due the fact that the reinforcing cable is spiral wound, so that there is a loose end on each side of the belt. This has the effect of lowering the capacity of the belt's tensile capacity per unit width near the edges. For the belt cited (in urethane/steel), a 1/4" belt is rated

This probably wouldn't be of concern on an aircraft, where presumably the drive is being designed with other factors in mind that limit the tension in the belt to more conservative levels.

Redundancy sounds good on an aircraft--whether it's actually desirable would depend on what happens when one belt lets go. Multiple belts means a higher probability of a belt failure in a given period of time. If a separating belt causes other serious damage or problems, then the redundancy is probably not a good thing.

I wouldn't expect load sharing to be an issue as long as the belts were from the same lot and checked for equal pitch length at installation. I have seen significant differences among different timing belt lots when installed on pulleys with fixed centers, and no idler or other provision for tensioning.

Please don't design a propellor drive based solely on my advice.

Ned Simmons