A long time ago at a factory I worked at, we had a bearing and power transmission salesman who came by on a regular basis. We were talking about something one day, and he mentioned that regular v-belts like you get at the car parts store are not rated for a pulley to run on the backside. He said that is why lawnmower belts are more expensive, they have more plys and are thicker on the backside of the belt, they are made for a pulley to run on the backside of the belt.
I don't know if you can do some web research and confirm this, but if it's true I would only run green lawnmower belts if I were you. Or why not tension the belt on the underside on the v side of the belt?
I will tell you also(you may already know this) but it's better to tension the belt on the return to the engine. In other words, if the engine turns clockwise looking at it from the front, and one of the belts runs over to the power steering pump, the idler would work best on the bottom part that is going down to the crank pulley, not the top part going to the pump. I hope you get what I mean.
Franklin,
I would believe that. As most on here know, I am into IH Cub Cadet Garden Tractors, and I and others have found, if you just goto the Auto Parts store and get the proper length and width "fan belt" they will fail in short order, like might not get the yard done, short. Now on some of these belts, they do not use a back of the belt idler, but on some it's they way the belt is routed and the way it moves while it travels. On a older IH Cub, the engine is a horizontal shaft engine and the crank is parallel with the frame of the tractor (the crank ends point toward the fron and rear of the tractor, not across like the older John Deere or Wheel Horse tractors). So the PTO is mounted at the front of the engine, and the pulley is perpendicular to the frame, so the belt in this case, is running over the top of the PTO Pulley with the V facing the ground, directly below this pulley, is the mule drive, with 2 pulleys that one has a spring, and one a bolt which tensions the belt, but they are parallel with the frame. This turns the belt 90 degrees to head toward the rear of the machine. On the mower deck and rear belt driven tiller drive, is another pulley, that hangs down, and the belt goes around the pulley which is parallel with the ground, and the shaft it mounts on points straight down at the ground. A single point on the belt has to twist 4 times, with the v going from point down on the PTO, twist 90 degrees with the v facing the rear before getting to the idler pulley, rotates back the 90 degrees, to face the inside of the belt, runs the length to the implement where it goes around the pulley, and then rotates 90 degrees again so the v is facing up to enter the other idler pulley, then twists 90 again, to go from facing the rear, to facing down to go over the PTO..... The v belt drive on the deck itself has a rear idler, which will chew up a "fan belt" also.
What I have started using is the Blue Kevlar belts from TSC (Tractor Supply) and they have lasted for years of heavy use. Plus the come in 2 or 3 different widths from something like 15 inches long to over 100 inches long. These may work out for what he is trying to do.
