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Belts - Maintainence & when to change?

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Beagle08/10/2010 13:10:39
21 forum posts
Hi all,
 
Lathe drive v-belts - how should they be maintained, when / how often, and how do you know when it's time to replace them?
 
The obvious answer is once they've snapped of course, but I beleive in a more preventative approach )
 
I ask as I've recently picked up a ~20 year old Speed 10. It's in excellent condition, and if anything is probably suffering from under-use. As a result the 2 belts seem a little stiff and make a few squeaky / creaky noises as they rotate on the pulleys (it's definitley the belts!). They don't appear to slip, nor are cracked - just a bit noisy - kinda like the squirmy noises sports shoes make on a squash court.
 
Is this typical of a v-belt, or do they sound past their best and hence time to replace? Also any advice on using belt dressing / conditioning sprays - or best avoided?
 
Cheers,
- Clive

Edited By Beagle on 08/10/2010 13:11:54

David Clark 108/10/2010 13:21:11
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3357 forum posts
112 photos
10 articles
Hi There
There will be an article about belts in MEW 170.
regards David
 

Edited By David Clark 1 on 08/10/2010 14:11:18

Jeff Dayman08/10/2010 14:38:52
2356 forum posts
47 photos
Dressings and conditioners in my opinion should never be used on V belts - always run them dry.
 
V belts should be replaced if the working surfaces are glazed / shiny or burnt / powdery, or if there are pronounced deep cracks more than a few mm from the inside out, or if outer layers are breaking away.
 
Old belts can work fine but if they start exhibiting any of the above mentioned flaws, they should be changed.
 
 
Gordon W08/10/2010 14:55:08
2011 forum posts
Don't spray anything onto a V belt, they drive off the sides, tighter belt more friction. I would replace the belts if they are that old, modern belts can be more flexible, waste less power. Keeep the old ones tho'.
Beagle08/10/2010 22:00:00
21 forum posts
Thanks guys. The belts show the slightest hint of glaze on the sides, but based on what you've said, they're other wise not too bad. For a few quid, I'll probably pick up a couple of new ones and aim to get them fitted in the next month or two; if it runs better great, if no different then I have spares.
 
David - cheers for the heads up. I'd not had time to digest all of issue 169 yet, however if I had, then I'd have spotted that 170 may answer my questions!  
NJH08/10/2010 22:32:31
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2314 forum posts
139 photos
Hi Clive
 
If you are going to change your V belts you might want to consider replacing them with a link belt.  I was amazed at the quiet, smooth running achieved when I changed mine. In addition there is no need to dismantle the headstock to fit them.
regards
 
Norman

Edited By NJH on 08/10/2010 22:32:59

Nicholas Farr09/10/2010 02:07:48
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3988 forum posts
1799 photos
Hi, a couple other things to look for are; see that the V shape hasn't gone a bit rounded at the bottom part of the belt and/or see that the flat bit on the inside of the belt isn't touching the bottom of the pulley's, both pulley's will be shiney in the bottom if this is the case. If however one pulley is shiney in the bottom, then it's more likely to be the pulley that is worn, especially if it's the smaller pulley. Belts and pulleys that are in good condition and properly adjusted should never need any dressing with sprays or the like. The belt should never be drum tight, general tightness is about 16mm deflection at mid position, per metre of of pulley centres, but should be a bit higher on short centered drives. If your pulley centres are say 300mm or less, then set them with about 25mm to 30mm deflection per metre, e.g. 25 x 0.3 = 7.5. The deflection pressure should be about (I'm genralising here) 0.6 kg on small size section belts to something like 2 to 2.5 kg on say an A section belt. Idealy the machine manufacturer will give the correct tension in the user manual.
Regards Nick.
Bill Dawes09/10/2010 13:00:25
605 forum posts
Try the ERIKS website, they are the people that bought out the famous Fenner brand, lots of useful info on all power transmission products although could not find a PDF specifically on belt maintenenance.
Bill D.
Bill Dawes09/10/2010 13:07:59
605 forum posts
PS.
Would reiterate advice on spraying, vee/wedge belts don't need it, I remember from my apprenticeship days this was common on the old flat belt days (a sticky tar like substance) we had 'Johnny the oiler' who came round squirting oil over everything and 'dressing' the belts. Drive ratios were changed with a deft flick of the hand to flip the belt up/down a pulley, taking care to avoid slashing your hand on the clip that joined the belt together. Ah the good old days, would be H&S nightmare now.
Bill D.
KWIL09/10/2010 13:58:17
3681 forum posts
70 photos
A more simple tension test is to grasp the belt between your fingers at the midpoint and if you can just  twist it through 90 degrees you are somewhere near correct.
 
Belt should not be driven at the time (e&s)

Edited By KWIL on 09/10/2010 14:16:13

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