Question for math boffs - serp belt size
Question for math boffs - serp belt size
My basic 'year one' maths tells me that the pulley is 0.30" smaller in diameter, but as the belt only makes contact with half of the pulley, I only need to account for 0.15" difference which is 3.8mm.
Now, the question is if I deduct 3.8mm from the 2151mm belt will that be correct, or do i really need to deduct 7.6mm from the belt length to account for the fact that I need to reduce the circumference by 3.8mm?
Or am I speaking utter twoddle. Someone help!!
So I'm going from a 2.55" pulley on my supercharger to a 2.25" pulley. The serpentine belt that currently fits great is a 6PK2515 (2515mm) belt.
My basic 'year one' maths tells me that the pulley is 0.30" smaller in diameter, but as the belt only makes contact with half of the pulley, I only need to account for 0.15" difference which is 3.8mm.
Now, the question is if I deduct 3.8mm from the 2151mm belt will that be correct, or do i really need to deduct 7.6mm from the belt length to account for the fact that I need to reduce the circumference by 3.8mm?
Or am I speaking utter twoddle. Someone help!!
Dark Samurai
15-07-2018, 05:53 AM #2You'll have to keep the 7.6mm belt I think, but what do I know, I only got a B in maths yesterday
Back to school for you.Dark Samurai
15-07-2018, 06:08 AM #4The one that's the 7.6mm you're talking about, not 3.8!!!!!!!!!!!!!!!!!!!!!!!!
You need to work out the circumference of the part of the pulley that the belt will sit on for the old and new pulleys...
Old Pulley Circumference = a
New Pulley Circumference = b
Then half them both, so now you have a/2 and b/2
Then do (a/2)-(b/2) which will tell you how much shorter the belt needs to be :thumbup:
sprinter2012
15-07-2018, 06:08 AM #5Don't take this as gospel, but it makes sense in my head...
You need to work out the circumference of the part of the pulley that the belt will sit on for the old and new pulleys...
Old Pulley Circumference = a
New Pulley Circumference = b
Then half them both, so now you have a/2 and b/2
Then do (a/2)-(b/2) which will tell you how much shorter the belt needs to be :thumbup:
EDIT: And as you rightly said that's assuming the belt is in contact with exactly half the pulley
sprinter2012
15-07-2018, 07:34 AM #7Looks right to me, specially as the figure you had before was 3.8 so it's all in the right area :biggrin:
EDIT: And as you rightly said that's assuming the belt is in contact with exactly half the pulley
if it were me, i'd cut the old belt, fit it and measure the gap to get a rough idea, (maybe with a strange assortment of clamps to keep it taught), And then compare that to the Math!
:confused1: didn't/couldn't the suppliers provide you with the necessary length?
if it were me, i'd cut the old belt, fit it and measure the gap to get a rough idea, (maybe with a strange assortment of clamps to keep it taught), And then compare that to the Math!
I may just have to buy a few belts _around_ the size I think I'll need and see if I can get the shop I buy them from to agree to me returning the ones that I don't use.
I think the problem with using string/cutting belt is that its going to be quite hard to get the size right when you're going to be fighting with the belt tensioner.
I may just have to buy a few belts _around_ the size I think I'll need and see if I can get the shop I buy them from to agree to me returning the ones that I don't use.
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