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Pulleys/sheaves?


EXFFPM's Avatar
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05-21-03, 01:20 AM   #1  
Pulleys/sheaves?

I swapped a 3 h.p. B&S with a 3.5 h.p. B&S between my lawn edger and a reel type mower and need to replace the pulleys/sheaves (the round part that mounts on the drive shaft with a keyway and allen screw) that the belt runs on, since they are different O.D. and the shaft sizes are 5/8" vs 3/4".

Are they called pulleys or sheaves, and if I increase the diameter on the edger, is there a formula for identifying the drive belt size I need? Thank you in advance!

 
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cheese's Avatar
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05-21-03, 01:26 AM   #2  
Hello EXFFPM!

No formula that I'm aware of. I would stay with the proper diameter pulley, because a smmall change in pulley diameter can make a large difference in the drive ratio of the equipment the pulley drives. New pulleys are inexpensive, so I reccomend getting the correct OD pulley for the machine with the corresponding ID diameter for the engine to be used.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
EXFFPM's Avatar
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05-21-03, 02:19 AM   #3  
Pulley replacement/swap

Cheese,

Thanks for the prompt reply! So they are called "pulleys"? Any suggestions where to purchase them at a decent price? Thanks again!


Last edited by EXFFPM; 05-21-03 at 02:35 AM.
 
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05-21-03, 04:27 AM   #4  
Just a little fyi I figured might come in handy one day. It has been a while since I did the math so bear with me. To get the proper size for a v-belt (flat belts use a different formula), here is the formula:

L=2xC+1.57x(D+d)+(D-d)/4xC

L=Length of belt
C=Distance between center of sheaves
D=outside diameter of large sheave
d=outside diameter of small sheave

So if one sheave(pulley) is 2" in diameter and the other sheave is 3" in diameter and the center of both sheaves were ten inches apart, then:

2x10=20
3+2=5
1.57x5=7.85
3-2=1
4x10=40
1/40=.025
20+7.85+.025=27.875"

So the length of the belt needed should be about 27 7/8" I think.
If some can double check my math for me, I would appreciate it. I know the formula is correct, I just don't know if I worked it out correctly. Or you could just forget everything you've just read and wrap a string around the pulleys to get the length. I know that either using the string method or the formula above can be incorrect a little due to the fact that the v-belts sit in the groove, so the string method's accuracy would totally depend on where the string would be placed during the measurement. I hope I typed it neat enough so everyone understands it.

 
EXFFPM's Avatar
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05-21-03, 08:04 AM   #5  
Mower17

Thanks for the info....that's exactly what I was looking for. I had taken all those measurements, but had no idea what to do with them. Had hoped the place where I was going to buys the parts could do the calculations? Really appreciate that! Thanks again!

 
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05-21-03, 09:34 PM   #6  
One other thing to keep in mind. A properly tentioned belt will have 1/64th" of give for every inch that the two shafts are aparated by.

 
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05-21-03, 10:30 PM   #7  
Good info Mower!

EXFFPM...you can call them pulleys or sheaves... Sheave would be the more appropriate word, but most people just call them all pulleys, which is fine.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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