Double belts

[Trevethan]

Just replaced alternator and new one has twin pullies. Noticed that the water pump and drive also have twin pullies so thinking good idea to use double belts, but the old vee belt looks a little wide (on all the pulleys not just the new one) and worried doubled belts could interfere with each other.

So question is do I stick with slightly wide belts or scrap them and buy two a touch thinner?

All the best

Nick

 

[FlyingDutchman]

A vee belt should run on the pulleys with the outside of the belt level with the outside of the pulley. From what you describe, I would think that this is not the case here. This means, that the belt is too wide and should be replaced with the correct one. I would then also use two belts. Make sure you buy the two belts at the same time and from the same supplier in order to avoid differences.
Good luck!

 

[Avocet]

I used to have a car with double belts. They used to be sold in "matched pairs". If your alternator was happy with a single belt, does it really now need a double one? Its very difficult to get both of them doing exactly the same amount of work each. Depending on how old the alternator is, you might find that modern "V" belts (with the serrated insides) are just so much better than older ones that they can transmit as much power singly as the old ones used to in a pair. Of course, if you do fit 2, and they DON'T fit that well as a pair, you have the huge advantage of a backup one when the one doing most of the work fails.

 

[billcowan]

In industrial applications it is generally considered that all your belt problems just go away if you "overbelt"

I have a machine that used a single belt that needed renewing every 6 months, so last time I put on double pulleys and belts, that was ten years ago. Never even had to re-tension them.

nuf said

 

[[2068]]

Double belts are the work of Satan.
"By the power of my torque wrench I command thee..."

Volvo used to have double alternator/water pump belts, but changed to larger singles or the new "flat" belts.

Why ?

The problem is that if the double's aren't adjusted perfectly, or one is a bit more worn than the other, they can vibrate out of synch with each other, then they can touch, and if you're really unlucky (like me) there can be an 'orrendous bang as they cross over each other and self destruct.

dv.

 

[Its_Only_Money]

Sounds like an installation issue rather than something wrong with multiple belts per se - multiple bets are quite common in agricultural applications too - I once had a flail hedgetrimmer (tractor mounted) that used a set of 5 belts in one part of the drive. Expensive if you have one break as you have to change the whole set - but they never broke! (well not in the 10yrs we had it anyway).