Q- For those in the know........ With Gilmer belts..... I've seen a ton of cars/hot rods/fast *** race cars,past and present, that have the belt riding over the idler, then a bunch with the idler on the backside of the belt...... Is there a reason for such either way? I have my own thoughts, but, I digress. What was /is the reasoning behind the one way, or another? Trying to learn why things were done the way they were, and what was the advantage/disadvantage from either side......... Chime time......
might find that there's more belt wrap with the belt inside. But you might also find that the belt might hit the water pump pulley that way, if there's a water pump, and the belt is not perfectly sized.
Six of one,,,half a dozen of the other,,,,,,whatever works . Like Jim said,,,,you might find an interference somewhere,,,or need a little different position to make it all work . You do whatever it takes,,,,,,just imagine back when they were chain drives,,,,,chains flopping around ! Tommy
Just interested in as why one as opposed to another...... On another note- my belt is riding outside the idler...... Plenty of room there with no interference. I do have a water pump. Just looking at it, I don't think I could swing things with the belt inside. Also- just by mock up, I can see there's a greater contact patch of the belt, as opposed to running the idler on the backside. I'de have to measure both scenarios to calculate the percentage of contact. Thanks!
The Surfers,,,,,,man,,,,they were really at the top of the game at one time ! Low buck guys that were really compe***ive,,,,,,,it’s sad what has happened to fuel racing . I remember reading at one time where there would be over a hundred fuel cars at the races . Can you imagine watching that from the stands,,,or sidelines ? And I know they weren’t all top quality cars,,,,,but a lot of regular guys out there trying to have fun and be involved with racing . Southern California was the hub of fuel at one time,,,,,,,but,,,with 350 days of sunshine a year,,,,how could it not be ? Tommy
I’m running an Isky slide idler... Belt is on the inside... Saw an article in a 60s CarCraft that states running inside promotes longer belt life and nothing else.
Ide like to have a "fuel roadster", but my blue collar wont allow it! I'll keep pluggin along with the hemi'fied,lung fed ,A bone roadster that sits in the garage...... To be continued..........
With the belt inside the idler, it's going to have more than 180 degrees contact between the belt and the upper and lower pulleys...it has to. With the belt outside, it has to have less than 180 degrees contact. But....is that an issue? It might be if you're using a 1/2" pitch sq tooth belt, and cranking out some boost. I know I have to get the tension just right on a 2" wide 1/2" belt on my 427, to keep it from skipping when it's cold.
Idler location can be used to increase belt wrap. Belt wrap is the amount (or angle) that the belt is in contact with the supercharger pulleys, measured through the pulley centerline. The higher the belt wrap, the more contact area and better grip. Often we have little choice about where the crankshaft and supercharger pulleys are relative to each other – manifolding becomes the constraint. This means there is not much room to move the supercharger around to increase belt wrap. However, we can sometimes use an idler or tensioner pulley to increase belt wrap. As the supercharger drive belt is loaded, there is a strong tendency for the belt to move into a more circular shape. This phenomena is called orbiting. Orbiting reduces belt wrap, which in turn reduces the grip that the belt has on the pulley, leading to slippage. To reduce orbiting we can put the belt under tension in a number of ways, though having the idler “outside” the belt works more directly on orbiting than when the idler is inside. In terms of location, supercharger drive belts have a slack side and a drive side. Like a piece of rope, the crank can pull on a belt but cannot push on it. Where a choice is available, the idler should be installed on the slack side of the belt. This reduces loading on both the belt and the idler. The idler pulley should be located at least twice the idler pulley diameter away from the nearest other pulley. This gives the belt a chance to relax after it’s last bending, get aligned if the pulleys are not dead-true and also to p*** through some air and cool down, each of which will extend belt life. Cheers, Harv
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