Thanks, Dan!? I appreciate the comments. Very much!

You reminded me of a question I forgot to ask about belt tightening. Thank you!

My current plan is to mount a free spinning, 2" idler on one or both sides of the belt. I put two 1/2" slots to accept the bolt. Today, the 30mm wide, 8mm pitch belt slides on my prototype fairly tightly, then I can tighten with the idler.

However, you recommend using slotted holes for the motor mount. I considered that, and it would likely be ideal, since I wouldn't need an idler - saving me both space (I could bring the two gears closer together), and efficiency of having a bend in the timing belt (not to mention the additional wear).? What kept me from doing that is that the motor is 120 pounds and I was worried that the weight and vibration would eventually 'wiggle' the motor down, loosening the belt. This is especially true since I'm having to mount only a single face of the motor (at least that's the current plan).? (Plus, the bolts are only 3/8" holding in the motor.)

Am I being overly concerned about the bolts loosening and the motor slipping down?? I'd love to have slotted mounts, but I'm nervous!??

Thanks again, Dan!? I really appreciate your help. Especially the drawing of your solution!