I have the dual drum rotary tumbler from Harbor Freight and it had been working well until a few weeks ago when it started rotating the drums really slowly. I did some researching and found that the belt tension could be adjusted. So I added more tension to the belt and it did great, until that belt snapped. I figured maybe it was time, that belt got used enough, so I replaced it on Friday and now today during more tumbling the second belt snapped. Am I putting too much tension on these belts? I need good tension on the belt when I fill both drums otherwise it doesn't spin them fast enough to get good results. If anyone here has any experience with the HF tumblers, please I need your input. The belts are cheap enough to replace, but I don't want them breaking every time I try to use the machine.