Sizing a fan belt

[tree monkey]

My small store of spare fan belts has come to an end, minor problem is from the numbers on the old belt how do I work out what size I need.

 

0100 675 0450 932.

 

Thanks in advance for any help given both relevant and not

[rusty69]

It may help to mention the engine make/model TM.

 

I tried to guess the right one for my old Yanmar the other day.Measured it with a bit of string.The one that turned up was still too big (well, you did say relevant or not).

 

I ended up cutting it in half to measure it, but figure it was probably stretched anyway.

Edited October 15, 2018 by rusty69

[matty40s]

Don't phone that. its a premium rate nuclear war advice line from North Korea.

[dmr]

Its not easy but there is quite a bit of info on the www from some belt suppliers, though some of it is just too much detail.

 

Measure width of belt, most common is 12.5/13 mm   This is an "A".  The little ones are 10mm, this is a "Z", bigguns, quite rare on boats, are "B".

 

The measure the depth....some are deeper than others, might or might not matter depending on your pulley. I think this would result in either an A or an AX for example but you need to check this.

 

Last get the length...lay belt on table and run a tape measure round the edge....a sewing type tape measure rather than a steel tape.

This gets a first shot at the length but most belt makers appear to specify a length at a sort of working distance which is somewhere between the inner and out lengths of your belt, so likely a cm or two shorter than what you measured.   

 

Either take a chance and buy the belt on eBay then measure it, or go to a shop where you can compare your old belt with the new one!

 

Your number is maybe just a part number, try typing it in to Google....there might be another number on the belt (if you are lucky) which relates to its size.

 

.............Dave

[rusty69]

https://www.beltingonline.com/vee-and-wedge-belts-213/help-identifying-v-belts-591/

[zenataomm]

I too used the string method once in Stone Staffs.

 

I went into a little back street shop next to the market.  The bloke in there wasn't overly enthusiastic about unpacking oodles of fan belts from their cardboard  wrap arounds in order to offer them up for comparison.  Until I said I was happy to give him two days while I enjoyed the pubs and Indian restaurants, and I'd buy three.

I got them in less than a day.

[MtB]

6 hours ago, dmr said:

 

Last get the length...lay belt on table and run a tape measure round the edge....a sewing type tape measure rather than a steel tape.

This gets a first shot at the length but most belt makers appear to specify a length at a sort of working distance which is somewhere between the inner and out lengths of your belt, so likely a cm or two shorter than what you measured.  

 

I find belt length shockingly critical. Your method works well as a ranging shot and the belt that comes in the post will be close, but rarely right. Either a bit too short or a bit too long. This allows one to place a second order that will probably be dead right, although in my experience sometimes it takes a third order to iron out the last residual error.

[BEngo]

There are three sorts of belt: V belts, wedge belts and poly V belts.

V belts and wedge belts are similar and both look like a traditional car fan belt with  a trapezoid section. They can be had as plain belts  or cogged belts.

 Poly V belts look like modern car drive belts with 4 or more raised ribs.

V belts are sized by the belt width, using the letter codes A, B or C and the length in millimeters or occasionally for American sourced belts the length in eigths of an inch. Look for a number like A 1033. There is a standard range of lengths, which google will find you, plus specials for big volume vehicle makers.  The length quoted is the pitch length of the belt not the outside length.  The pitch length is measured at about the centroid of the belt shape and is less than the outside length. Again google will turn up some correction factors  for the difference between outside length and pitch length.

Wedge belts are similar but deeper section and  the size is described by the letters X,Y or Z.  eg Z 775.  Marked Lengths are pitch length, not outside length.

dmr has given the sizes of common sections above.

Cogged belts have notches on the inside and are better for small pulleys.

Poly v belt sizes are described by the number of ribs,  a P(for poly V), the rib size by letters H,J K. and the length in mm. ( or eighth inches).  Eg 4 PJ 1133.  Cars usually use the K size.

N

 

[dmr]

11 hours ago, Mike the Boilerman said:

 

I find belt length shockingly critical. Your method works well as a ranging shot and the belt that comes in the post will be close, but rarely right. Either a bit too short or a bit too long. This allows one to place a second order that will probably be dead right, although in my experience sometimes it takes a third order to iron out the last residual error.

Well I did suggest either go to the shop and measure or buy one on eBay and hope its right first time.?

 

When I redid my domestic alternator installation there was no time to hang about so I purchased three belts in adjacent lengths and yes, length is critical. One was ok and the other two were at or beyond the extremes of the adjustment range.

 

............Dave