Re: Belt tension?

Posted by Bob M on March 24, 2005 at 12:48:35 from (151.190.254.107):

In Reply to: Re: Belt tension? posted by Allan in NE on March 24, 2005 at 11:29:17:

Hi Alan – Belt slippage has nothing whatsoever to do with which side of the engine an alternator is mounted. Rather it’s belt tension and pulley wrap that matter.

But.....you are indeed correct about in the “old days” belt slippage was less of a problem. The reason for this however is alternator output capacity, not which side of the motor the the alternator happened to be positioned.

Explanation: Back in the early 60’s when they first appeared on cars and tractors, most alternators had a maximum output of 25 - 30 amps or so. This required about 1/2 HP to drive at full load – well within the capacity of a single 1/2” V-belt.

Fast forward a few years and you’ll find alternator capacities have increased. The 80’s era, internally regulated Delco alternators (the preferred unit for 12 volt conversions) are rated usually 55 or 61 amps. This alternator needs 1-1/4 HP or more to drive at full output – about the limit of a single V-belt. Therefore if the belt is not tight, or it’s oily or wet, it’s gonna want to slip under heavy load - like immediately after starting the engine.

Today cars are now routinely supplied with 90 to 120 amp (and larger) alternators. And these are universally driven by multigroove serpentine belts to deliver the 2-1/2 HP+ it takes to spin ‘em at full load. Further, unlike V belts, serpentine belts are “threaded” around a series of accessory, tensioner and idler pulleys at the front of the engine to achieve a 180+ deg belt wrap around each pulley in order to enhance the belt’s grip. And there’s always a spring loaded tensioner to keep the belt tight as is stretches.

Bottom line is with regard to belt slippage it doesn’t matter where the alternator is positioned on the engine – it’s the layout of the belt drive that counts! ...Bob

Follow Ups:

• Re: Belt tension? Allan in NE 14:22:46 03/24/05 (3)
  • 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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