Belt up!

[bogstandard]

Bank on around 10 to 12 squid a metre. I've haven't bought any that large for a few years.

I would just like to add, that I think this belting is great, and I have used it for many years in many applications and never had a problem.

Unfortunately, I am having my first problem with it on my lathe, and have had to swap back to the old belting system for the time being, until I have time to investigate further.
Both belts are exactly the same length, but for some unknown reason, the one nearest to the head is either throwing the belt out of the groove, or breaking the welded joint. I have swapped the belts over after rejoining, and the same thing is happening again, same inner pulley groove.
I suspect it has something to do with the pulleys themselves. It only happens when starting the lathe in very high gear, so I suspect that coupled to something wrong with the pulleys, and the intial stretch of the hi torque start brings on this strange phenomenon.

I thought I would mention it, just in case you want to revert back to putting on the link system, which in your case is a tried and tested system (when the right size is used).
I wouldn't want to fall foul of recommending a system to you that has a problem that I have never come across before.

John

[John Hill]

John,  re the two belts on your lathe.


Now,  you have two belts, I suspect  the pair of sheaves of at least one pulley is not identical, well we know they are not identical dont we as one pair of sheaves breaks the belt and the other does not.  Because the pulleys are not identical one gets slowly ahead of the other and this is a situation that cannot continue so one belt breaks.   

It is not unlike the effect of you get driving an early model Land Rover on the road with 4WD engaged, one axle goes 'further' than the other and the difference is taken up by winding the suspension until eventually the stress gets too much and one wheel looses traction and you get that rather startling bang from under the vehicle.

[bogstandard]

John,

Thanks for the insight.

That is the same sort of conclusion I came to, mismatched groove sizes. Because these belts have so much grip over a standard type, they just don't slip like a normal belt would in that situation, and balance themselves out, so something has to give. Depending where the joint was, either tighten up on one side, overstretch the joint and break it, or go too slack on the other side so the belt is thrown off.

I still don't know why it only happens with just the one pair. Why isn't it alternating between the two? Why is one belt always being classed as the master set that the other has to try to follow?
Maybe it has something to do with the surface finish down the grooves. Unless of course, it is the machine doing the most logical thing, giving the belt which always has the least stress on it priority over the other, leaving the one with the imbalance to take care of itself. Who knows?

I can see a good debate coming out of this.

Unfortunately I can't do a take out and fix at this time because I need the lathe for other work, and when I do get them off, I think Stew will be having a visitor to his already crowded little shop.

But I thought I had better warn Darren just in case he would suffer the same fate if he was using twin pulleys. As I said, it isn't nice when you thoroughly recommend something, and it all goes pear shaped. You tend to gain a rather bad reputation, and a few new unrepeatable names.

John

[Darren]

No worries John,
Can only have a go eh?

Re your problem, I agree the two pulleys are not exactly the same and it proves just how much grip this Redthane has as the punished one is obviously not slipping...!!




My current problem is finding out what section size I need....

I thought it was B, but now I think it's A after doing a bit of research.

The confusion came about by looking at the markings on some newish belts on other machines. In this case Halfords branded. According to them A is bigger than B...this is clearly wrong.

After looking at some belting charts I came up with these figures for the top width of V belts

A=13mm
B=17mm

And the depth

A=8mm
B=11mm

Armed with this info it seems I need an A sized belt for the mill.

The equivalent diameter for Redthane seems to be

A=10.2mm
B=12.7mm

So I believe most of our type of machines would use 10.2mm diameter Redthane on our A section pulleys.



I'm still trying to work out what Z & M sections are, I have a little drill that uses a small section belt......



Please if any info above is wrong then give me a  . I wouldn't want to mislead anyone that may read it. 

[Darren]

John,

Does the difference in Rethane section size actually make that much difference?

10/12 mm don't sound like enough to worry about if you get it wrong?

[John Stevenson]

John,

Had this many times on large saws.

What you need to do is take all the belts off and choose one belt.
Put it on pulley track 1 and mark the motor pulley with a paint marker and the belt, then mark the belt on centre of the driven pulley but not the pulley. Measure that distance.

Now turn the motor pulley 10 times and measure from that mark on the motor pulley to the driven the distance you measured and mark the driven.

Do the same in all the grooves with the same belt and in theory you will get the driven marks all in line.
in practice they will be out, By how much is dependant and the groove width and depth.

The trick is then determining which one, or both are out.

I used to have a two brass blocks that were a section of a B series belt [ only worked on B series so didn't need any others ] these were popped into a groove and measured across the backs and the readings compared and the grooves machined so they all matched the lower reading.

John S.

EDIT for Darren,
To all intents and purposes Z and M are the same at 3/8"

[Darren]

John,



EDIT for Darren,
To all intents and purposes Z and M are the same at 3/8"

Ah....that explains why the conflicting info I have been finding......well not conflicting if you know what I mean......

Thanks for the clarification....John....

[bogstandard]

John S,

Many thanks for the checking info, I will use it when I get to doing the pulleys.

It might only be a couple of thou difference between the two, but it can cause major problems when things like this occur.


Darren,

When we used to use Redthane at work, we had it in stock most of the time. You can in fact get away with a smaller size if pushed, as long as it doesn't sit in the bottom of the groove, then it will drive OK, and can get you out of a situation if you run out of stock of the correct size, but it does overload the belt a little so is only a temporary measure until you get the right size.

This is all getting to a point of interest.

We wouldn't fit the belt by saying it is such and such a size for a given groove. We would measure the width at the top of the V groove and fit the next available sized Redthane down. So say it measured 14mm at the top we would fit your 12.7mm belting.
This is assuming you can have the belting sitting proud of the pulley. We did it that way because we knew that even though it isn't following the manufacturers guidelines, we were in fact fitting the strongest belt we could have on there. You did as much as you could to make the drive system more robust.
If you have very close fitting guards, then you have to go by the recommended sizes, which are to allow the belt to sit in the groove and not have the top edge protruding above the V groove. So the example of 14mm, you would most probably use the 10.2mm diameter.

John

[shred]

One other thought-- do you need both belts?  A number of the 12x36 crowd here just run one most all the time, and it sounds like the redthane can transmit more power than one ordinary belt.

[John Hill]

One other thought-- do you need both belts?  A number of the 12x36 crowd here just run one most all the time, and it sounds like the redthane can transmit more power than one ordinary belt.

I believe John needs all the power he can get when turning down old truck crankshafts making chew toys for Bandit.

[bogstandard]

Bernd,

As John has said, I need all the transmission power I can get.

Not because of the size of the jobs I do, but the speed I run the machine at. Because I make mainly very small brass and ali parts, I usually run at high speeds to assist in getting good finishes.

Even though I fitted a one sized larger belt, and had it sitting above the V groove top, I still wouldn't like to start up in a high gear with just one belt. It takes a lot of torque to run the machine up on initial start with a high gear selected.

For some reason, my machine is fitted with a 2HP motor than the one at 1.5HP as shown in the manual and all the literature, another reason not to have a weak transmission system on there.

I'm not unduly worried at the moment, the old belts are working OK, and when I get the time and inclination, I will get the pulleys matched up. The only problem I have is swapping between gear ranges, it is a real PITA with the old belts on.

Bogs

[John Hill]

John, I cant even get my started in the high speed ranges, not even after running for a while and warming the oil etc.  Mine is 2 HP two though I guess they are little under nourished Chinese horses.

Starting in a high speed range trips the circuit breaker which is only 10 amps.  Of course I could up the circuit to 20 amps but I fear for the longevity of the motor which has already failed once (though not from start up loads).  So I am seriously considering mounting the motor of a hinge (gate hinges look promising) so that with a lever I would have a slip clutch for starting in high speed ranges.  (So many things to do, including going to the office each day! )

[bogstandard]

John,

Mine goes into full bore straight away, even on the highest range.

I did blow the caps on the motor a while back, and Chester UK replaced the motor, but forgot to ask for me to send the old one back, so not to waste anything, it was sent to the local council recycling facility.

Very soon after, I picked one up from the council recycling area, F.O.C., an identical motor match for my machine, but the caps were blown. Wasn't I lucky?

So I think I will just replace the two caps and I will have one ready to go if the need arises.


John

[John Hill]

Hmmmmmm.....  maybe mine would start the high ranges if I took the chuck off,  I assume most high speed work would be done with the collet chuck anyway..

[bogstandard]

There is only one way to go John.

Try it.

It just might be the drain trying to spin up a heavy chuck that is causing your problems.


John

[Bernd]

Ah John, are you off your meds again. 

How did I get involved in this conversaion about how many belts you use. See reply #35. Some how I got mentioned. 

Bernd

[bogstandard]

Sorry about that Bernd, it is BECAUSE I am on meds that the problems occur.


Now what's that damned name I use?

Ah! got it.

Steve

[John Hill]

It just might be the drain trying to spin up a heavy chuck that is causing your problems.


John

Yep, if I take the heavy chuck off and it spins up ok in the top cog!

[JohnC]

Thanks to all for the info on this thread.  I had to renew the drive belt on my DW mill:



It was 1/4 in in old money:



So 6mm should do it.  A length of solid Redthayne belt arrived, 6mm:



I looped the belt over the pulleys and marked off, just like Bogs did above.  I subtracted 7% as
per instructions.  I tried Bogs' high tech welding device but couldn't keep the joint still enough between heating
and getting to the angle iron.  So, a low tech jig.  Apologies to those of a nervous disposition - the jig uses the fibrous brown stuff
normally used for making sheds:



I trapped the belt in each side so it could just be pushed together after heating.

I used an old hacksaw blade, heated up and cleaned with emery to remove any deposits,
then heated to cherry red and placed between the ends of the belting.  In the time between
removing the heat and getting to the jig the blade had cooled somewhat, but still easily melted the belt :



I then gently pushed the ends together and went off for a brew



I trimmed the joint with nail clippers (saw that on another post - due credit)



And - result!



The 7% shortening seemed a lot, but the belt stretched nicely over the pulleys and the joint
shows no sign of weakening.

(And Neebs - if you read this, yes, that is your old machine, doing sterling work!! )

Again, thanks and due credit to all on here who provided inspiration.

John

[andyf]

Thanks to all for the info on this thread.  I had to renew the drive belt on my DW mill:

It was 1/4 in in old money:

So 6mm should do it.  A length of solid Redthayne belt arrived, 6mm......

That's posh, John!
My Mk1 DW had a car fan belt on when I got it, so when I re-motored it for variable speed and ended up with the pulleys a bit further apart, I just got a new one from the local car accessory place.

I think your pulleys have narrower grooves, though.

Andy

[JohnC]

Hi Andy,
The pulley grooves are semi circular section - not sure where they came from. I have another mill with 'A' section belt. That said,as has been mentioned above, the 'thane belt runs well and doesn't 'balloon' from the pulleys.   
John

[Jonny]

Slightly off topic whats the stuff you can buy to spray on the belt or V pulley to reduce slipping?