Disregard that last paragraph.

1 1/2 inch hose cuffs have an ID of 1 1/2 inches.

Copper pipe has a nominal ID of 1 1/2 inches, but a larger OD.

About the only way you'd be able to slip those hose cuffs over 1 1/2 inch copper pipe is if you unscrew them from the hoses and dip them in boiling water for a minute. Then the vinyl would be soft enough to fit over the 1 1/2 inch copper pipe fairly easily.

If you have to do what you're doing every year, it would make sense to buy a vaccuum hose joiner (or coupling) so that you don't have to fight with this same problem every year.

Also, I've heard of janitors using silicone caulk as thread sealant on their hose cuffs to both ensure the cuffs don't loosen up and to ensure an airtight seal at the cuff/hose connection. If your cuffs are hard to unscrew, don't force them because they're probably siliconed on. You should be able to push both 1 1/2 inch cuffs onto a vaccuum hose joiner so there's really no need to remove the cuffs from the hoses.