Bandsaw vibration - Advice?

[Dissolve]

Hello,

Picked up an Eelektra Beckum BAS 315 bandsaw recently, looks like a pretty good fit for my needs but the thing shakes the house down on the faster speed! It's incapable of making any decent cuts with it vibrating like this.

So far I have tested the following:

- Run the motor with no pulley, and it's nearly silent with a very very small amount of "wobble", but hardly any.

- Run the lower drive chain with the pulley and lower wheel on the slower setting, vibration improved massively and would be very workable.

Based on these tests I'm assuming it isn't the motor/pulley at fault, but when I tested the lower drive chain on the faster setting, the belt made a small squeeky sound when spinning by hand and when switched on the machine made MUCH more vibration. So the vibration comes into play when the lower drive chain is running on the higher speed setting.

Any ideas folks? I'm thinking of trying a new belt regardless but not sure where I might get one?

 

[CHJ]

1. Take off Blade.
2. Take off or slacken drive belt so that motor is not driving lower wheel.
3. Run motor, does it vibrate?
4. Is the motor mount stable and secure?
5. Lower wheel, are its bearings sound and free running without undue play or knocking noises?
6. Likewise upper wheel.
7. Spin Lower wheel and check for balance, it should not stop in the same position but at random locations.
8. Likewise the upper Wheel.
9. Are both upper and lower wheel tyres even and complete.

 

[Dissolve]

3. Run motor, does it vibrate?

No, with the motor mounted in the machine and with the belt slackened and pulled aside, it runs extremely smooth without vibration. Slight amount of wobble as it slows down but hardly anything.

4. Is the motor mount stable and secure?

From what I can see, yes. As the motor spins well on it's own, mounted, I would assume it's very secure!

5. Lower wheel, are its bearings sound and free running without undue play or knocking noises?

I have not been able to remove the lower wheel yet to spin it with no load on it, but as soon as I figure out how to remove it I will test this and report back.

6. Likewise upper wheel.
Upper wheel spins very well

7. Spin Lower wheel and check for balance, it should not stop in the same position but at random locations.
Will check the wheel balance(s) once I have worked out how to remove the lower wheel and report back!

9. Are both upper and lower wheel tyres even and complete
Both tyres are in great condition, nothing I can imagine causing any vibration.

 

[RogerP]

I fitted a Powertwist belt - made a difference.

http://www.fennerdrives.com/powertwist-plus/

 

[Dissolve]

The belt only squeeks on the higher speed setting but to be honest, the belt doesn't feel/look worn in the slightest.. I'll check the lower wheel better tomorrow before purchasing a new belt as it seems more likely to be the lower wheel.

What am I looking out for with the lower wheel? Aside from clicking noises from the bearings?

Thanks

 

[Aden30mm]

If you have a green 315 made in Germany, you got a good one all steel construction (except the table and wheels). I had one for over 15 years and it was a brilliant piece of kit. I would have kept it if I had the room, when I upgraded. However, the one problem I had was with the blade tensioning mechanism, and I changed the whole tensioning carriage and threaded bar under warranty.

I think Chas has nailed a systematic was of fault elimination. What I would say is it needs to be bolted down to a suitable stand with some weight. I made the stand myself which allowed for some weight to be paced in the lower portion of the stand, I always thought that the optional extra floor stand was rather flimsy (but I sure many would argue that it was fit for purpose). Also may be worth checking the blade guides (top and bottom), for wear and the ability for them to free run. If you take the table off you will also be able to check both wheels for true with a good straight edge (the table as I recall is held on my 4 both onto the tilt rack).

Regards

Aden

 

[Aden30mm]

Sorry I meant bolts.

 

[Dissolve]

Thanks! I like it so far, I'll be checking the wheel assignments, lower wheel bearings and take a closer look at the belt today.

Fingers crossed its something simple! Seems strange that it doesn't cause any problematic vibration on the slower setting yet it shakes so badly on the faster one.

 

[CHJ]

Seems strange that it doesn't cause any problematic vibration on the slower setting yet it shakes so badly on the faster one.

If the drive belt is a Polly Vee Belt check that one or other of the drive pulley wheels does not have saw dust packed in the grooves. Can often happen if cutting green wood when stringy wet wood threads end up being flung around the lower wheel.

 

[Dissolve]

Seems strange that it doesn't cause any problematic vibration on the slower setting yet it shakes so badly on the faster one.

If the drive belt is a Polly Vee Belt check that one or other of the drive pulley wheels does not have saw dust packed in the grooves. Can often happen if cutting green wood when stringy wet wood threads end up being flung around the lower wheel.

UPDATE:

Checked the wheel alignment
Wheel's are co-planar

Cleaned the vee belt and pulley grooves
No build up in either the belt or pulleys.

Checked the bearings by spinning the lower wheel
Bearings are making a bit of noise but I wouldn't have thought this could cause the machine vibration?

There is some play in the lower wheel, should the circlips grip the inner wheel of the bearing to be tight? Or should the inner wheel of the bearing spin as well? I ran the motor with the belt and lower wheel attached and the vibration remains. SO I have located the cause is the lower wheel in some way.. and the belt/pulleys look to be in very good condition.

Thanks

 

[Eric The Viking]

Is it a wobbly wheel, or does it just slide on the shaft? Sliding is OK, wobble isn't.

It's beginning to sound like a wheel bearing to be honest, which is a nuisance, but not expensive to fix, as they're usually a standard size (see several other threads on this). Basically, get a new pair, carefully drive out the old ones (change both at the same time, too), and drift the new ones in. Freezing the bearing and warming the wheel will improve the clearance for fitting (but it may be too small for that to make much difference). If you do freeze it, put it in a plastic bag in the freezer, with as little air as poss., so condensation is kept to a minimum when it comes out (unbag it at the last minute). It's worth getting sealed bearings for this job, if they weren't before.

It's not as hard as I make it sound, really. They're not all that high-tech.

 

[Dissolve]

There's slight side to side play with the wheel, but when the wheel sound there's only the slightest "wobble" so I'm not sure it is that. Should the circlips but up tight against the bearings?

I'll replace them regardless I think, but I'm wondering how slightly noisy bearings could result in the whole machine vibrating badly?

 

[CHJ]

Are the lower wheel bearings rotating freely? make sure they are not seized with dust and that the inner race is not running on the support shaft, if this has happened then the replacement bearing fit may need a loctite type assembly of the inner race to prevent it skidding on the shaft.

 

[Eric The Viking]

The other possibility is a motor bearing - there isn't much else to affect it as you've eliminated pretty much everything else.

I wasn' quite certain from your original post: if you take the blade off and run motor+ bottom wheel on their own, does it still vibrate, and does altering motor drivebelt tension make a difference in that circumstance?

If so it can only be either motor or bottom wheel bearings, or a missing balancing weight. Is it high frequency or low frequency vibration and does it change with the gearing? If high: bearing(s) If low, bottom wheel out of balance, possibly. If it changes with the gearing, it's probably the bottom wheel. If it stays a constant frequency, but the amplitude changes, it's the motor.

 

[Dissolve]

Are the lower wheel bearings rotating freely? make sure they are not seized with dust and that the inner race is not running on the support shaft, if this has happened then the replacement bearing fit may need a loctite type assembly of the inner race to prevent it skidding on the shaft.

With the wheel removed and turning the wheel with the fingers supporting the bearings they both run smoothly, with a slight ticking/clicking noise, but they appear to spin very well in all honesty!

When you say "Make sure the inner race is not running on the support shaft".. Do you mean the the inner race should stay tightly secured on the shaft? Because when spinning the wheel assembled with the circlips, the inner race does spin a bit with the rest of the bearing/wheel!? :?

The other possibility is a motor bearing - there isn't much else to affect it as you've eliminated pretty much everything else.

I wasn' quite certain from your original post: if you take the blade off and run motor+ bottom wheel on their own, does it still vibrate, and does altering motor drivebelt tension make a difference in that circumstance?

Yes, with the blade off, and the belt driving the lower wheel the vibration is apparent, it's bad enough to slightly shake the machine which is then magnified if the blade+upper wheel are put into the equation.

If so it can only be either motor or bottom wheel bearings, or a missing balancing weight. Is it high frequency or low frequency vibration and does it change with the gearing? If high: bearing(s) If low, bottom wheel out of balance, possibly. If it changes with the gearing, it's probably the bottom wheel. If it stays a constant frequency, but the amplitude changes, it's the motor.

The wheels don't seem to ahve any additional weights added to them but spinning them free-hand they seem to stop with a different point at the bottom each time, so they seem reasonably well balanced

I would describe the frequency of the vibration as low. Definitely not a high pitched/squealing.. The vibration almost completely disappears when changing the gearing to the slower speed.

Based on these things, Is it worth trying to remove any left-to-right play with the wheel? thus "locking" the inner race of the bearings? Or maybe try replacing the shaft? I have been tensioning the belt with a reasonably amount of tension, as per the Record power bandsaw setup DVD I purchased a while back.

 

[CHJ]

.....When you say "Make sure the inner race is not running on the support shaft".. Do you mean the the inner race should stay tightly secured on the shaft? Because when spinning the wheel assembled with the circlips, the inner race does spin a bit with the rest of the bearing/wheel!?

May not be the cause of your problems but this is not good, it means that the hard bearing is using the support shaft as a bearing which will in time only cause wear on the support shaft, the inner race of the bearing should be a good enough fit to prevent the inner race rotating on the shaft in normal use. You may not need a new shaft, knurling the shaft and/or using a locking fluid may be sufficient to get a usable fit.

 

[Dissolve]

.....When you say "Make sure the inner race is not running on the support shaft".. Do you mean the the inner race should stay tightly secured on the shaft? Because when spinning the wheel assembled with the circlips, the inner race does spin a bit with the rest of the bearing/wheel!?

May not be the cause of your problems but this is not good, it means that the hard bearing is using the support shaft as a bearing which will in time only cause wear on the support shaft, the inner race of the bearing should be a good enough fit to prevent the inner race rotating on the shaft in normal use. You may not need a new shaft, knurling the shaft and/or using a locking fluid may be sufficient to get a usable fit.

Okay great! Thanks for the advice, So is it worth me ordering a replacement set of bearings and trying them with some locking fluid?

If this doesn't cure the problems, anything else I can try?

Cheers

 

[Eric The Viking]

You've diagnosed it systematically. There may be other worn bits that add to the problem, but it seems that the bottom wheel bearings are not well.

I'd order sets for top AND bottom wheel bearings and do both, as it's highly likely the top ones aren't far off knackered too, as the force is pretty much the same on both of them.

Spare ones will be expensive, standard ones shouldn't be. There's a lot of postings on this previously - worth a search.

When you get it apart, do what Chas says, and have a close look at the fit/wear of the bottom shaft. If the bearing has damaged it significantly, you might have to replace it (he suggests other remedies too, above).

They're not complex machines - once you've done that (and set it up properly!) it should work as new, literally.

E.

 

[Dissolve]

Brilliant! Thanks for the tips!

This one has the alluminium table rather than cast iron which I would like to try and replace eventually.. But for the moment the "Spare" bearings are £5 a piece and a new shaft is around £10 so worst case scenario we're looking at £20/£30 to get a (hopefully) decent running machine!

Whilst I'm on the subject, when I switch the power on at the wall (before switching the motor on) I get a buzzing/hum sound from the motor which I assume to be the capacitor, it's not a huge deal as the motor fires up brilliantly well, but is it something I should try and remedy?

 

[Eric The Viking]

This is a wild guess: your bottom wheel bearing is knackered, so there's quite a bit of friction to overcome when starting-up. Try it with absolutely no load on the motor. In other words either completely slacken or (better) take the drive belt off altogether. I'd expect an audible hum for a moment or so, at worst, and apart from the fan it should be pretty quiet. Compare it to another induction motor of similar size, if you can. If it's quiet, you probably have your answer.

Incidentally, If it has starter contacts you should hear these drop out with an audible click after a second or two of running, and drop back in when you cut the power (they're centrifugal and they switch in the starter coil). If the motor is small enough it may not have them fitted. Otherwise apart from the fan, it ought to be pretty quiet.