[TubaMorg]

I assume you mean for a chain? A swivel motor mount is also an acceptable way for tensioning. Two things to keep in mind:

1. Whatever tensioning method you use should be robust enough to not spontaneously loosen. For example, simply having a pivoting motor mount would not be enough because it would just pivot back under tension. You would have to figure out a way to lock it in place.

2. Your chains WILL LOOSEN with use. They stretch and will fall off if you do not check them periodically. For that very reason, even if you mount things so that the chain is tight initially, the chain will stretch. Without a tensioning system you may have a lot of heartache.