# How to measure V belt size?

• posted

I need a V belt (Z range) for a machine I'm building.

How do I work out the size I need from the pulley sizes and spacing? I want to avoid a trial and error approach, which from past experience will involve buying several.

TIA

Mike

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There are some web pages that will calculate it for you : e.g.

There's another one that explains how it's calculated, but I can't find it right now ..

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Thanks Adrian. The only difficulty I have with the calculator is knowing which pulley diameter to use. Is it the top of the v groove, or the bottom, or some intermediate diameter?

Mike

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Don't know, I'm afraid. But unless someone else knows better, I'd use the same measurement as the belt : i.e. if you measure the belt's outside length, then use the top of the groove.

For what it's worth, I have a Picador pulley marked by the manufacturer as 12" which is 12" across the _outer_ diameter. And I don't think the bottom of the groove should be important, as the belt isn't supposed to touch there.

• posted

In message , snipped-for-privacy@virgin.net writes

Mike, The pulley should be measured at its pitch diameter not the OD. Most quality pulleys will measure slightly "oversize" if you measure the OD.

As a general guide pitch diameter is worked out as follows.

Z section belts - OD (mm) minus 5.5 mm A section belts - OD (mm) minus 7.5 mm B section belts - OD (mm) minus 9 mm

This information is taken from a handbook I have that originally came from Fenners belt manufacturers in Hull.

Using these figures it should be possible to work out the total length of belt you need using one of the numerous calculators available on the net providing you know the centre distance of the pulleys.

Regards,

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Thanks Pat.

I've just discovered this afternoon that some (all?) belt manufacturers appear to use the length on the pitch diameter when specifying their products, so your information now ties everything nicely together.

Mike

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Would this help?

Lionel

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Mike,

I've been working through this for some months (as a novice) and the best site I've found is

You have to keep drilling down but they have loads of PDF's that cover everything to do with belt and pulley specs. A great supplier of belts I've used for phone orders is AC Belting. email is snipped-for-privacy@acbelting.co.uk No connection just placed a couple of orders.

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Lionel/Steve

Many thanks for the info. Really useful.

Mike

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replying to mike.crossfield, velmurugan wrote: Budgetary quotation for V belt grade testing unit for testing C 122 V belt grade from 48 to 52 using load cell (for tension), Linear trasducer ( for length measurement), LED display, pulley wheel 2 Nos duly following the railway RDSO guidelines.

Velmurugan v P southern railway trichy

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