If you join the Yahoo Sheldon Lathe group they have a pdf. parts manual for the M series machines. Page 12 of the parts manual gives the details on how to change the Worthington variable speed drive belts.
You might want to suggest to the owner of the main Sheldon Group that whomever cares for FILES move everything from the subsidiary group over to the main group and lock down the subsidiary. The main Atlas Group on Yahoo used to have two other groups for file storage space. But when Yohoo foisted NEO off on us, about the only improvement was that they boosted the available space for files from 100 MB to 2 GB for most active Groups. After the NEO dust sorta settled, I moved all of the files and some of the photos over to the main group and locked down the subsidiary (but kept it for testing).
Old John Knox, the owner of both Sheldon groups is up in his 70's and probably has not thought of it combining the two groups or just don't want to. There is a sub monitor, but I don't recall his name or if he has control of doing anything either. It's a good group for getting information on the smaller lathes, but not much help from John on the R series lathes.
OK. That appears to be a future problem with several (if not all) of the Yahoo groups that I'm a member of. There is for the most part only one person with "the keys to the castle". That, coupled with the fact that it apparently isn't possible to get any response out of Yahoo, doesn't bode well for long term survival of any of the Groups.