this idea have been on my mind for very long time. back on the time when I still use fixed motor screw holes mounts. the belts always will have little loose, or if too tight will kill the belt. So, I always wanted to use 2 fingers to press on the belt to make it fit well. that comes the idea of this idler. have been test it for a while, working good.
to put springs on the idler, the purpose is to put pressure on the belt. makes the belt not too loose, and not too tight. to achieve the function, absorb vibation, protecting belts and pulleys. making the system more effective.
Note: to keep proper pressure on the belt ! but I can not tell you what proper it is. what I can do is to collect datas. like for 15/36 pulley need 330 belt on my long mount. So, on this require buyer’s DIY ability.
this idler is not fixed, the whole idler set will move following the movement of the belt. https://www.ebay.com/itm/303086092686
advertise this product, by the way. https://www.ebay.com/itm/303229671320