Robert has belt drive kits now

curtisfox

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May 13, 2010
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609
Now you've got me drooling over a belt drive for my nexus hub... thanks a lot. Good thing they are very much out of my price range or it would be a splurge buy... It would hook right up to my shift kit without any fuss. Now i'm looking to see if there are belt options for all 3 of my chains (not v belt).
Maybe this will help, just about anything you want.............Curt http://www.sdp-si.com/products/Timing-Belt-Pulleys/index.php
 


CrazyDan

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Jul 9, 2016
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curtisfox

Active Member
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May 13, 2010
Messages
609
Unless you go with serpentine the V-belt drive pulley has to be about 3" other wise you get slippage. Like Whizzer they have around 2.5 to 6 then 2.5 or 3 to rim 15". 5 grove serpentine is 3/4" wide, and is the same as 5 V-belts, so almost impossible to slip. What is sad the only pulleys you can get are car size. I am doing a alternator pulley on jack shaft, with a 24" bike rim on rear wheel.
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used tapered strap hinges bent to attach pulley to rim............Curt
 

JerboaJohn

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Jul 29, 2018
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so with belts, pulley diameter to figure ratio but is it outer diam or at bottom of the groove?
 

zean

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Dec 5, 2010
Messages
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With V-belts to figure ratio I think you measure somewhere in between the outer diameter and the bottom of the groove because it's the sides of the belt that come into contact with the pulley. I believe if you have a 2 inch pulley driving a 5 inch pulley the reduction ratio will be about 2.6 or 2.7 to 1. Am I right about this?
 
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curtisfox

Active Member
Joined
May 13, 2010
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609
With V-belts to figure ratio I think you measure somewhere in between the outer diameter and the bottom of the groove because it's the sides of the belt that come into contact with the pulley. I believe if you have a 2 and a half inch pulley driving a 5 inch pulley the reduction ratio will be about 2.6 or 2.7 to 1. Am I right about this?
Depends on the pulleys new A pulley 1/2" and new A belt the belt will actually stick up above the pulley a tad. ..........Curt
 

zean

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Dec 5, 2010
Messages
45
Yes I think I'm going into too much detail. Not a big difference: If someone has a top speed of 30 mph with a 2 and a half to 1 reduction ratio then with a 2.6 or 2.7 to 1 ratio the top speed would be 29 or 28 mph respectively. If there was more difference between the size of the pulleys say a 10:1 reduction ratio then there would be a greater difference in figuring out the speed. Although I think you're right I might be splitting hairs.
 
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