Thanks you for the formula. By any chance do you remember the reason why you included belt load? Is a higher or lower belt load preferred. The more I think about it the less I understan lol

 

Belt load has to be entirely pertaining to slip only.

Keeping the same ratio will keep the same blower speed, so it will take the same amount of horsepower to turn the blower. This means that the strain on the belt between pulleys (pull or stretch) will be the same if the ratio remains the same.

Therefore the only difference can be that the larger the diameter pulley, the larger the circumference. Which translates to more of the belt touches more of the pulley, which reduces the amount of strain per square inch.

Sooo, more belt/pulley interface, less frictional stress on the belt.

 

Thank you for the explanation. If belt load is only related to belt slip and wear, assuming belt slip is completely mitigated via something like a griptec pulley, would you pick the smaller set?

The larger set would have a larger crank, and all the pulleys attached to the crank would spin faster leading to more passive loss right?

 

Yes. I have a added on crank pulley with a separate belt for my blower and I keep forgetting that most setups use a single belt. Yes your accessories would turn faster. Why don't you try the pulley that comes with your blower fiirst? Why are you assuming that it will slip? This is going to be a long project if you analyze every detail like you have the pulleys.

 

Nothing wrong with spinning the accessories 10% over. My truck stays super cool and never had any issues with AC or charging system. It is a DD with 10% over balancer and I've put 60k on it since that configuration was setup.

 

Belt load refers to tension on the belt itself. I would use this number to determine if you need to go to a higher rib setup since the load would be divded by the width (cross section) of the belt. I vaguely remember something like 25lb per rib being a rule of thumb, although that may be antiquated by now. Pretty sure I included that because it was mentioned in one of Hartman's books, probably this one:
I would go with the larger crank pulley since it will be more flexible. Overspinning the accessories is fine unless you are planning on 7200rpm+.

 

Atomic, what happens past 7200 rpm? Just curious?

 

Things spin faster. Not a hard rule but general guideline around that rpm. If you plan to spin high you need to make sure the accessories dont go beyond their limit, especially the alternator, by using larger pullies on there.

 

Ok, thank you. That explains why my water pump pulley kept coming off. Lol. I had to weld it onto the shaft to get it to stay put bc I was shifting at 7200.

 

Ive had that happen too, even with it tacked on. I believe the alternating stress basically rocks the pulley off the shaft since its pressed on. Putting more power through the belt system driving a supercharger and using higher stiffness tensioners will do it. I believe the PRW pump helps a lot if needed.