Replacement A belt sizing confusion

[julianf]

I have a smallish A belt.

Its still got the markings on it, but they dont make sense to me.

It says "A50"

but also "A450"

So what's all that about then? I have the belt, so i can (kind of) measure it. I would imagine its about 10" diameter ish, so about 30 odd inches in length - about. But neither of those really tie with the A450 marking?

 

[brightspark]

here https://www.vbelts4less.com/Measuring-Belts_ep_46.html

 

[julianf]

Thank you. Thats kind of what i thought. I must be making a mistake though - ill take a photo and post it up.

Of course, i could just measure it, but id like to understand what is going on!

 

[8ob]

Thank you. Thats kind of what i thought. I must be making a mistake though - ill take a photo and post it up.

Of course, i could just measure it, but id like to understand what is going on!

Just take it in and get another one matched up Ashley, there does not seem to be any correlation between whats printed on a belt vs what they actually measure, I have a belt gauge so measured a belt thats supposed to be 1270mm long. Turned the belt inside out as they recommend and it measures 1260mm, measured as is its 1220mm so take your pick.

 

[brightspark]

I just use the string method and take it in to get belt. it never fails

 

[julianf]

It says A540 A20 =50

 

[julianf]

...so I guess the A20 number might be correct? Certainly not 540 inches long!

 

[MCKDAVID]

A - section is 12.7mm wide, at the widest point of the Vee. Measure yours it will probably be around 12mm or so, allowing for wear if it's still an A - section. The numeric value indicates overall length, the 540 will be millimetres.

easiest way is to take it with you for a direct comparison, but if not, brightsparks string method will work fine, or at least close enough. You normally have some tolerance, but you need to look at the adjustment, how much there is.
One thing to look at is your alignment, it might be the angle of that photo, but the belt looks well off...

 

[julianf]

The motor isn't mounted in the photo.

I'm replacing the original motor with a larger one, but will keep the same belt length.

 

[julianf]

Hmm... 20 inches is not 540mm

I thought the A20 was 20 inches?

 

[MCKDAVID]

I did wonder when I saw the guards off etc..

 

[MCKDAVID]

it could be imperial, depending on the age of the machine if it's ancient, it could also have been a part number. Older systems / manufacturers were all a bit - each to there own. Modern belts (in Europe at least) generally are all standardised now, in section size and length and follow the metric base. Obviously there will still be exceptions, the oddballs, by far the easiest way is to measure it..

 

[merryman]

There are at least three different belt sizing systems. The one you have shows two of them. A20 is the UK Imperial size 20” inside length. A540 is the metric size, but this is measured externally, hence the discrepancy in 20” not equalling 540mm on a ruler. There is another system, seems to come from the US, where belt length is external circumference in inches. This is used on mower belts, particularly ones that act as a clutch, Kevlar and cloth covered. None of these sizes are all that exact, I have seen A1200 and A1215 belts both claiming to also be A46. Imperial sizing is not just for “old” stuff. As on car wheels, inch is still used as the standard for run of the mill belts. Metric sizing is used more on notched and raw edge belts.

 

[julianf]

There are at least three different belt sizing systems. The one you have shows two of them. A20 is the UK Imperial size 20” inside length. A540 is the metric size, but this is measured externally, hence the discrepancy in 20” not equalling 540mm on a ruler. There is another system, seems to come from the US, where belt length is external circumference in inches. This is used on mower belts, particularly ones that act as a clutch, Kevlar and cloth covered. None of these sizes are all that exact, I have seen A1200 and A1215 belts both claiming to also be A46. Imperial sizing is not just for “old” stuff. As on car wheels, inch is still used as the standard for run of the mill belts. Metric sizing is used more on notched and raw edge belts.

Thank you!

Thats exactly what i was after - i know i could have measured it, but now i have that knowledge (with luck) until i die!