eXcel expression for relating pulley size, distance between centres, v-belt length

Get yourself an HPC catalogue; it has all the necessary formulae for designing v-belt and toothed belt drives

find them at

cheers, David

Steve, You are going to need different spreadsheet for timing belts to V belts due to the pitch diameter being different on each of these. Vee belts usually use the OD of the pulleys and the outer length of the belt. Timing belt have a PCD that is outside the pulley.

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

Ordered one today. I hope the maths for V-belts is better than the flute music they have on the website for timing belts...

Thats why I hoped to cadge a proven excel equation! My typing is OK but never learned to play the flute.

Best Regards

Steve

Thanks John. I did some more working out and discovered that I can probably get to a decent 40rpm with V-belts on the C6B, so I can avoid using timing pulleys. (I'm using 10% of top speed as a usuable working minimum on the C6B eg 0- 2000rpm as shipped = 200rpm lowest useful speed which seems about right).

There is a bit of stuff here at the bottom under transmission.

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

I can't help with how or where to measure but maybe I can help with the maths. The notation is how excel expects it.

If the big pulley is radius R, the little pulley r and the distance between centres is L. Then, First work out the angle of the belt to the horizontal. Angle = ASIN((R-r)/L) in Radians (excel default)

Then work out the various bits and add them up.

The bit wrapped around the big pulley is =(PI()+Angle*2)*R The bit wrapped around the small pulley is =(PI()-Angle*2)*r The straight bits are =SQRT(L^2-(R-r)^2) (there's 2 of these)

With the following values, R=9 r=3 L=23 I got a belt length of 85.3

Mike.

P.S. anyone interested can find an XL sheet at

I built an excel sheet using the belt formula in the catalogue. I tested it using pulleys of equal size first and it produced the expected result. Used real data from my C6 and it came up with a 900mm belt instead of 800mm. Cannot spot the error. I'll have another go.