<VV> Re: Belt Slippage

[Frank DuVal]

NicolCS at aol.com wrote:

> [Craig said:]Slippage  would be even worse at lower rpm.   I'm going 
> to try this
> again  someday with a brand-new belt to see if the results  change.
>
> [Fraink said:] In actual experience, a glazed belt will alow more 
> power throughput at lower RPM
>  
> [Craig replies:]
> I don't claim to be an ex-pert (or even a current one) but as I 
> understand things with certain loads "on" and a certain battery 
> charge, the car's electrical system will demand a given amount of 
> current.  Knowing system voltage is 14ish, that means so many watts 
> (aka horsepower) is needed.  At a given rpm, say 3000, that horsepower 
> requires a certain torque on the alternator.  At lower speeds, the 
> alternator field current is increased in order to maintain the output 
> current.  Thus, at 1500 rpm, the torque (belt load) will be doubled 
> compared to 3000 rpm.  I guess it's possible that a glazed belt might 
> save itself by slipping but I've never experienced that.
>  
> Craig (puzzled) Nicol


Your description is correct, just go a step further. At idle RPM, the 
alternator will not deliver full output, slip or no slip. Full field 
voltage or not.  Therefore the horsepower demand is less, therfore the 
slippage is less. Glazed belts slip most of the time. That is what 
caused the glazing. Belt dressing, sandpaper, soap are temporary 
measures at best, replacement is the only cure. Glazed belts sometimes 
squeal. Have you noticed that most squealing belts do not squeal at 
idle, just  starts to squeal when the accelerator is pressed to leave 
the traffic light.

Frank DuVal