Flat belt issue

[Sonic EscapeParticipant @sonicescape38234]

I just got a new belt for my lathe and I have some problems with it. I understand how to adjust the two pulleys in order to keep the belt from falling off. But I don’t understand why it is wobbling like this. Could it be a defect of the belt?

The old belt doesn’t wobble like that. So that means the new one is bad or I’m missing something?

I bought the belt here. I got the cheapest one, the one for 11.2 euros. Because I was stingy. But is it normal for it to be so bad?

 

[OldironParticipant @oldiron]

If you run a straight edge around it on the sides does it look to be V shaped ? If so it has been assembled incorrectly. If not I would tighten it and try to run it in. Maybe been sitting in packaging folded for some time.

[Oldiron]

On Oldiron Said:

If you run a straight edge around it on the sides does it look to be V shaped ? If so it has been assembled incorrectly. If not I would tighten it and try to run it in. Maybe been sitting in packaging folded for some time.

Yes it does. But the V shape moves to the other side if I put the belt in the other way. So I think this is not caused by assembling error. And the old belt doesn’t have this V shape.

One more thing. If I put the belt on a flat surface I can’t notice any irregularities. So maybe some of the internal glass fiber wires are broken and this is deforming it when tensioned?

 

[Graham MeekParticipant @grahammeek88282]

It looks to me like the new belt has not been manufactured correctly.

Regards

Gray,

[SillyOldDufferModerator @sillyoldduffer]

Also possible, because it’s that lathe again, is the tensioner problem fixed?  Low or over-tensioned belts can snake.

Bearing in mind the lathe has been completely dis- and reassembled (I believe), confirm the pulleys and tension roller are parallel and aligned fore/aft.  And that the bearings aren’t twisted in the motor or headstock. Apply a straight-edge to check alignment and a DTI to confirm there’s no run-out.

As the lathe seems to have some non-standard features, trust nothing until proven otherwise! Bent motor shaft?

Dave

 

[DiogenesParticipant @diogenes]

EDIT – no, agree it’s the belt – that is ‘wrong’ – if you used that on a machine with cheeks on the pulleys it’d fail in short order – decent toothed belts run remarkably true..

Will they take it back / credit you the amount if you buy a branded one? ..a good belt should last for years on a lathe, so costs over time are small..

[JasonBModerator @jasonb]

Wonky belt, I believe they are made as a long tube then cut to width. That one was cut crooked.

 

[Ian PParticipant @ianp]

Absolutely the belt!

Last week a belt I ordered on ebay (UK) arrived and I fitted to my X1 mill following a motor and pulley change (I had previously converted it to belt drive). The new belt looked fine outwardly but ran atrociously. I then ordered a new belt but this time chose a brand name belt, I fitted it yesterday and it runs sweet and smooth.

This was a multi vee type belt, only 4 ribs wide (about 12mm) and 70cm long. Both belts run perfectly where they are in contact with the pulley but between the pulleys the unbranded belt wobbled side to side to the extent that at the highest motor speed the belt displaced itself off an idler. TBH the idler was only the same width as the four ribs it that was in contact with, but that arrangement had worked fine until I decided to change the motor and pulley.

Next time I will not go for the cheapest, the price difference between branded and unbranded belts was not that great.

Ian P

[cedric 1Participant @cedric]

Buy cheap, buy twice.

[old martParticipant @oldmart]

Definitely the belt, the teeth are not all square to the belt. You should get a Gates or Conti belt or buy a belt from a supplier like Simply Bearings who deal with industry and only sell trusted makes.

[Dave HalfordParticipant @davehalford22513]

Being ‘that lathe’ again is it me or has the motor pulley got a bit of a wobble as well?

 

BTW reject belts can be sold off cheaply, the ones that aren’t uniform thickness ( as in lumpy) or cut badly.

If you can turn the belt inside out will it run true then?

[cedric 1]

On cedric 1 Said:

Buy cheap, buy twice.

Yes, I rediscover this gain and again!

 

The lathe is fine. At least this part. I made a modification to use the old Continental belt that was too long. Everything is fine now. I’ll try to return that silly belt.

 

[SillyOldDufferModerator @sillyoldduffer]

Have Cedric, Ian, Jason and Old Mart missed the point?  I’m here to help Sonic fix his problem, and, like it or not gentlemen, there are two potential causes: Faulty Belt and Tracking Problem.

Sonic and Gray both suggest faulty belt early in the thread, and they might well be right.  But this is not confirmed.  The main evidence in support is that the old belt doesn’t wobble, but that’s suspicious because of the earlier unsolved mystery:  why is the old belt too big?  And Sonic says “If I put the belt on a flat surface I can’t notice any irregularities. ” – if the new belt is faulty, it’s not obviously so. No-one has seen the belt or the machine apart from Sonic.  Therefore, confidence level low because we’re working from a video and a few stills.

Why are so many so keen to bang the drum for ‘faulty belt’? Anyone prepared to deny that tracking errors cause the same symptoms?

I’ve been professionally trained to problem solve. Necessary because jumping to conclusions wastes time and money. “Engineers do not start by solving the wrong problem.”  Instead, apply a disciplined approach that eliminates costly rash, impulsive, ill-informed, and premature decisions.  Gather evidence, form hypotheses, and find the best match.  Usually necessary to revisit the evidence.  In Sonic’s  case, we know his lathe is odd and that it’s been stripped down and rebuilt.   An assembly error is entirely possible.

I say we can better help Sonic by reducing guesswork.  Evidence trumps experience.  All that’s necessary for Sonic to eliminate tracking error is to check with a straight-edge and DTI. If he finds everything is correctly aligned, that’s clear evidence in support of ‘faulty belt’.  Otherwise, the evidence supports ‘tracking error’, and he has to follow that clue.

If the ‘faulty belt’ belt advice is wrong, replacing the belt is an expensive way of confirming ‘tracking error’.  A quick simple test saves that bother, by confirming or confuting tracking error.  I see no objection to testing for it!  Sonic is better off testing than following distant advice that might well assume too much.

I’ve never come across a faulty belt that wobbled, though old ones set in their ways can be a bother.  I’m sure it happens, but are they common?  Evidence please, not opinion!

Dave

 

 

 

 

 

 

[cedric 1Participant @cedric]

Misaligned pulleys don’t cause the type of belt wobbling from side to side seen in the video. Faulty belt will.

Proof in the pudding is the old belt tracks straight.

No need for pontification.

 

[blowlampParticipant @blowlamp]

That isn’t a tracking problem. If it were, the belt would just move to one side or the other and remain there.

As has been pointed out already, these belts are manufactured very wide and then sliced to whatever width is actually required. It’s a faulty belt for sure where something went wrong in the slicing operation.

 

Martin.

[cedric 1]

On cedric 1 Said:

Misaligned pulleys don’t cause the type of belt wobbling from side to side seen in the video. Faulty belt will.

Proof in the pudding is the old belt tracks straight.

No need for pontification.

 

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