Figuring V-Belt Length ?

[CustomDoug]

Hi, I'm going to be picking up a v-belt for an industrial cylinder arm machine with a servo that has a small pulley (50mm) installed. I have the motor mounted and sitting in what looks to be the perfect angle (the relationship between the foot pedal and servo arm linkage). When I put a flexible measuring tape around both pulleys (not down in the grooves) I get 52"... when I fit a length of twine around and "into" both pulleys, I get 49". I know there is plenty of adjustment to the motor but since these belts are readily available in all sizes [48,49,50,51,52,etc], and I like where everything is sitting now, which length would you get? I'm thinking 50" would be the best - but I'm not sure if the stated belt sizes are measured around the outside or inside? They look to be about 1/4" thick. thanks.

Edited November 12, 2012 by CustomDoug

[The Major]

Pully 1 diameter x PI (3.14)/2

Pully 2 diameter x PI (3.14)/2

Plus length of pully 1 center to center of pully 2 multiply x 2.

Add it all together is your length.

[CustomDoug]

Pully 1 diameter x PI (3.14)/2

Pully 2 diameter x PI (3.14)/2

Plus length of pully 1 center to center of pully 2 multiply x 2.

Add it all together is your length.

Wow, the scientific method ! ; ) That's good info. Sounds like the 52" (flexible tape wrapped around the top of both pulley's) was the correct number... and that those belts are measured around the outside diameter. Thanks.

[trekster]

The cross-sectional thickness of the belt determines the flat layout dimension that will fit over a given configuration.

Here is a site that has a calculator on-line.