Re: Belt tension?

Posted by Allan in NE on March 24, 2005 at 14:22:46 from (148.78.243.24):

In Reply to: Re: Belt tension? posted by Bob M on March 24, 2005 at 12:48:35:

Hi Bob,

Naw, ain't goin' there. I've lived thru this one.

But, maybe I shouldn’t have used the terms "left side" and "right side" of the engine. I should have said 'taunt' side and 'slack' side of the belt.

All things being equal, what you say is true "if" and only “if” you have but one drive pulley and one driven pulley.

Add another pulley to the mix and all bets are off, 'cause it indeed does make a difference where that alternator (or any other load for that matter) is located in it's relationship to the drive pulley.

Any time a belt is used to transfer power, and during rotation, there is a "taunt" side of rotation and there is a "slack" side of rotation. One side is working and the other side isn’t; it is just “returning” to the task.

Picture two driven pulleys and one drive pulley; a triangle if you will.

Then, drive the alternator from the pull side of rotation and it will take less "tension" on that belt, for any given load, than it would if it were being driven from the slack side of rotation, because the "pull", the “rotation” or the "tension" of that belt is always trying to "tighten" on the pull side against it’s load.

Consequently, and because of the load on the taunt or primary side, it is also at the very same time, trying to "loosen" across the 'slack' or secondary pulley. The secondary load indeed will suffer from a "traction defect". See what I mean?

The only reason I even bring this up is because I was working on the line when GM changed their alternator mounting in the 1969 model year and this is when we began noticing this phenomenon.

Same belts, same pulleys, same alternators and same outputs. Everything identical except the darned location of the alternator in relationship to that crank pulley. Belts started to slip.

If an alternator is driven secondary to another load, the belt simply has to be tighter than it would have to be if that alternator were the primary load.

Allan

Follow Ups:

• Re: Belt tension? Bob M 16:42:26 03/24/05 (2)
  • Re: Belt tension? Allan in NE 17:04:43 03/24/05 (1)
    • Re: Belt tension? Bob M 14:23:45 03/25/05 (0)

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