Shredding Fan Belts Alternator conversion

[Harpkatt]

My Friend did a 12V Negative ground kit conversion in his 31' RPU(not sure of the make)he is now shredding belts. I know this is a common issue, can anyone point me in the direction of a thread that might have addressed this problem? It looks well aligned. I do have concern this belt is being overtightened, So I will start there.

[Jim Brierley]

This is not a common issue, so I don't know what to tell you. Over-tightening should not cause this, too loose might but you would hear belt-squeal. Perhaps the pulleys are not smooth? Maybe they are too small, not giving enough contact area?

[CarlG]

Pulleys not aligned.

[Brentwood Bob]

Alignment. The bracket maybe the main problem in my experience.

[DBrer]

I have not had a belt problem with many miles driven, and mine is 12v.

[Kurt in NJ]

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Look at pulleys for rust scales
How fully charged is the battery--- perhaps the alternator has to work too hard
Most cars with alternator the belt slips easy on the alternator pulley--- light finger pressure on the alternator fan usually cause slip -----

My belt is starting to look past it's prime---it's 45 years old, but the larger pulley the generator uses means the belt doesn't work hard

[DHZIEMAN]

Based on what is being described with the fact you have proper alignment and the alternator is the new item (and is one with the proper pulley diameter for Model A's) and is shredding the belts, the problem appears to be the alternator. When it is charging is there any belt squealing? Does the Alternator pulley turn freely with belt off and engine off? I run a 6 volt alternator, which should make no difference and it worked fine the first time I started my A, and all the mounting hardware I built up myself. Other than what I am suggesting you look at as possiblities, I have nothing else to offer.

[1931 flamingo]

How could the alt be the problem?? The wrong pulley (depth and width) yes. JMO
Paul in CT

[rocket1]

I would run a straight edge to the pulleys to check for alignment,I never heard of this happening,try a alternator pulley from Brattons and a new belt,make sure the tensioner bracket is holding it's adjustment and not loosening causing the belt to slip.

[CarlG]

A cogged belt helps.

[Mulletwagon]

Originally Posted by CarlG

A cogged belt helps.

Model As use a BX40, 41, or 42 cogged belt (which ever one fits).

[Bill G]

Alignment can be a tricky thing to sight exactly. I have a Nu-Rex 6v + ground and the bracket that came with it must be accurate because I have had no belt issues. If you don't know the source of the alternator or the bracket that holds it to the engine, I would suspect that as the cause.

[rotorwrench]

The alternators are generally connected to the buss though a diode bridge and a voltage control unit. If the system has any high resistance due to wiring or terminals in bad condition, any shorts to ground, or a bad battery then it can work the alternator pretty hard. If the alternator diode bridge or voltage controller are malfunctioning then that can lock the alternator up pretty easy. If it locks up, you will usually hear the belts shredding.

[eagle]

Make sure the alternator pulley is the right width. Too narrow of a pulley will be tough on a belt.