# Harmonic Vibration At 1000rpm



## Str8jacket (Aug 5, 2015)

Hi I am getting a vibration/ unbalance through my machine when i change to 1000rpm. I have removed the chuck and tried a small face plate with no change. I am getting a bit of belt shake (1-2cm) but the elec motor stays same speed anyway and doesnt seem to effect it at 700 rpm?

Cut at 700rpm is nice. Higher and it wobbles the lathe that much i end up with something that would look ok as a dining table leg. 

Sounds ok. Smooth. No rumbles or growly noises???

Any ideas?


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## Str8jacket (Aug 5, 2015)

Sorry forgot to mention it is a 1967. Colchester triumph 7.5in mk 1.5 according to the lathes .uk site. It is the last of the round head style i think.


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## Kernbigo (Aug 5, 2015)

play with the belt tension


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## T Bredehoft (Aug 5, 2015)

I had a similar problem on a jointer. Running at recommended speed, it seemed to bounce. I put a turn buckle on the motor and tightened the heck out of the belt, now runs smooth as silk. I don't know about belt life, but I can replace a belt, don't have to sand my arms away to get out chatter.


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## Str8jacket (Aug 6, 2015)

Thanks guys. I am away for work now for a week or 2 so I'll tighten it a bit more and see. Dont like going to tight as it loads the bearings up on the motor shaft but obviously it must need a bit more.


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## Kiwi (Aug 25, 2015)

It will be a twin belt  one may have stretched a bit more than the other also check main bearings


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## Str8jacket (Sep 6, 2015)

Well it has been a saga. I have gone through 2 sets of belts. Cheap rubbish that I bought locally as it was all I could find. No good. Ordered in some gates ones. Bit better but not great. Fitted a  spring loaded belt tensioner to the unloaded side. Better again. Not great. Bit the bullet and stripped the elec motor as it sounded noisy under load.

Bearings felt perfect? Replaced them anyway. Refit the motor and it is 90% fixed..... realigned the belts tensioned and ran for 10 minutes to recheck tension. There was still a slight vibration. Feeling around to see if there was any hot spots and the main input shaft was hot and getting hotter. Put temp gun on it and it was 70*C and climbing. Shut it off.

So wtf? It felt like the heat was coming from onside the pulley not from belts. Checked the brake, all ok. Looked at it for a bit. Drank 2 beers and pulled the main input shaft out. Both input bushes on the way out. Looking in the manual it says it should have needle rollers?

So im up for a shaft repair and the housing too. I'll put some photos up soon. Fairly peeved to say the least.


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## Str8jacket (Sep 11, 2015)

I am at a bit of a loss on the best way to proceed with this repair job. I have measured up the shaft and the housing and gave the measurements to a bearing supply company who had their engineer look into it. the dimensions of the shaft is 34mm and the housing is 41mm. the engineer cant find needle rollers that will fit in this size and is recommending sinter bronze bushes again.

The parts book specs needle rollers, but no dimensions on these parts like the rest of the bearings in the parts book?

I have had look at SKF bearing catalogue and they have needle rollers with an inner sleeve and the standard outer shell and the closest that I could fit is 30mm ID and 45mm OD. The ID I think will be OK as the shaft is 34mm but steps down to 28mm where the pulley mounts so I doubt there will be an issue there.

The bore in the housing though I am unsure on, the outer diameter is 62mm which will leave 8.5mm of wall thickness which I think would be OK except on one end there is a machined flat which will reduce the wall thickness on that one area to 3mm....

Is this going to be to weak? the thin area is on the opposite end to the pulley and is 90* to the load path as far as I can tell, will this be OK. Any opinions would be  appreciated.


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## wa5cab (Sep 12, 2015)

Can you upload the manual?  We don't have a manual on the Colchester triumph 7.5in mk 1.5.  Also is that 7.5" the swing (American standard) or the distance from the spindle to the top of the bed (British standard)?


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## Str8jacket (Sep 12, 2015)

I dont think it is any different to the one in the thread just below this one? 
The manual is the clausing colchester one 15in swing 30in 48in. On ebay.


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## wa5cab (Sep 12, 2015)

Str8jacket (please sign posts, or set up you signature by hovering your mouse pointer over your User ID at top right of screen, sliding pointer down to and clicking on Signature, and adding at least your name),

Every time you or anyone replies to a thread, that thread moves up the screen to top of list.  So there is no way to know what thread was just before this one the instant before you pressed POST REPLY.
If you'll say the thread name, I'll go and look  at it.  The thread below yours when I opened it to read was about the Clausing 5418.


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## sgisler (Sep 12, 2015)

Ummm, and your signature is.......? 


Stan,
Sent from my iPhone using Tapatalk


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## wa5cab (Sep 12, 2015)

Robert D., of course.


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## sgisler (Sep 12, 2015)

I was actually just being a smart a$$, but maybe sig's just aren't showing up on my phone/tapatalk??


Stan,
Sent from my iPhone using Tapatalk


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## sgisler (Sep 12, 2015)

Hmm, my sig, which I set up in Tapatalk, shows up in Tapatalk and on the web view in the 'body' of the post. Your (and others) sig's don't show up in Tapatalk and on the web view show up in a separate area below the 'body' of the post.  
Sorry for the derail....


Stan,
Sent from my iPhone using Tapatalk


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## wa5cab (Sep 12, 2015)

Ah, OK.  That's possible.  Do you see the status and command bar below any post?  The background color of the bar varies depending upon which display style you are using.  At the left end, just to the right of your avatar, there should be a check box.  To the right of that the poster's User ID, minutes since post or date of post, and two to five command buttons.  At the right end is the post number and two command buttons (Quote and Reply).  You might try a different style.  Except in the Classifieds Forum, right at the bottom left of screen you should see the name of your current Style.  Click on that and a two-column list should appear.


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## wa5cab (Sep 12, 2015)

OK.  That must be where the "Sent from my iPhone using Tapatalk" comes from.


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## sgisler (Sep 12, 2015)

Yep, that's interesting; added a dig on the web and it shows up below the body of the post on the web but doesn't show in Tapatalk. 
Going to try changing the style and see what happens. In default style on web. 


Stan,
Sent from my iPhone using Tapatalk


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## Str8jacket (Sep 13, 2015)

Put my name in sig as requested. Still wont show up on my phone? I have never seen anyones signiture when using my phone?

Anyway my lathe looks basically the same as Krolls 1965 roundhead that he is stripping down and cleaning up.


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## wa5cab (Sep 13, 2015)

Ben,

OK.  Thanks.  If you have occasion to look at the site with a regular browser, you'll see it.  I have no idea why Tapatalk doesn't show it but apparently it isn't just your phone..

Your machine is a 15" (in US practice).  Am I correct in assuming that it's a (Clausing assigned, I think) 6570 Series (single-speed motor) or 6530 Series (2-speed motor)?  We have a rather confusing manual on the 13" variants but nothing I can find on the 15" ones.  And we have a catalog that shows the 13", 15" and 17" versions along with the Model Numbers of all.  Which is where I got the 6530/6570 from.  What I was interested in finding was a picture of the bearings.  Straight Roller (and needle) bearings come in three types.  The first is what I think your guy quoted, where the bearing consists of an inner race, the rollers (with or without a cage) and an outer race.  The second has just the rollers and the outer race.  The third has only the rollers (with cage).  Perhaps the originals in your machine were of the second or third type?  Have you called Clausing about them?


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## Str8jacket (Sep 18, 2015)

Quick update, I have ordered a set of needle rollers these have an inner and outer race, will need to machine both the shaft and the housing for them to fit.

Hopefully a cheaper option to repairing the shaft and housing to still being only able to fit a bronze bush back in. Still not sure if it was built with brass bushes or this is a previous repair.

What are peoples thoughts on cleaning out the headstock ? I was going to drain and flush with shellite and refill, just worried about contamination in those Gamet bearings. I could see a small amount of brass material in the little feed cup arrangement that feeds the front spindle bearing, Not enough to cause damage Id think, but still don't want to go through this and then have those fail.


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## Kiwi (Sep 19, 2015)

I hope you haven't made chips yet Nobilla Machine tools Ltd   Colchester lathe specialists Tel-01 438 812 409 or www.nobilla.co.uk


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## Str8jacket (Sep 20, 2015)

Hi Kiwi,

No i haven't done anything yet, not sure what you are suggesting? Buy a new input shaft assembly from them, sell my lathe to them, send mine to them to repair?


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## Kiwi (Sep 20, 2015)

Sorry had to dash away.  I was suggesting  that perhaps they may  have the right bearings that you are after sometimes it's better to spend a bit more and get the proper parts than to re machine for an alternative Colchester parts are expensive and hard to find Nobilla's has probably the largest range of the older round head colchester parts that I have found and I would put it to you they won't be around much longer and also freight costs will be the killer as there nothing light in colchester


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## Str8jacket (Sep 29, 2015)

Well an update, I emailed Nobilla and they were very helpful. at the time they had one shaft but it turned out to have different number of teeth on it to mine, also with the Aussie dollar some where far below the toilet region it was also extremely expensive.

So I bit the bullet and machined the shaft and housing to accept larger needle roller bearings. It turns out the shaft wasn't even hardened? it turned down very easily, in light of this I'm glad I went the way I did, I had to speedy sleeve it for the seal too as I think it would wear in short order. I have got the lathe up and going again and it runs smooth as silk, very happy.

I am still not impressed with the belts, I have got three "matchless" Gates power II belts. A84 but they are just inconsistent, one even causes a light thump as it travels over the pulleys!

So I am looking for options, I have found a 3 ribbed Gates belt powerband back, so its three joined together but I cant get them over here and cant find a seller in the States that ships over here, so what other belt options do people use?

Ideally a single belt with 3 ribs would be the best I think, anyone on here sell belts?

Cheers


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## Kiwi (Oct 7, 2015)

What about a cam timing belt means changing the pulleys


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## Str8jacket (Oct 7, 2015)

If i hadnt just bought 3 more belts i would seriously consider it, the new gates ones i bought are no good. I ran it for half a day and it was fine at 700rpm. The motor got hotter it would vibrate at 1000rpm. It shakes the machine slightly and it has a slight knocking noise in the motor. Im over it. I bought a new motor and am going to put it in. The irony is it will probably have a different shaft size so i will need a new pulley!  Did i mention im over it.


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## Kiwi (Oct 8, 2015)

Time for a cold one


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## Str8jacket (Oct 10, 2015)

If only! Im on nightshift so I was playing before work, although a few stubbies before would make the night go easy!  
I fitted the 3 new carlisle belts I ordered and they are much better, I also scored a belt pulley laser aligning tool off ebay so I will double check everything is good when I finish work this week. 
A new teco monarch 5hp motor is on its way, thanks ebay again, also decided to fit a vfd next week off too, after I make sure the vibration gone, one lot of problems at a time!


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## Str8jacket (Oct 24, 2015)

Well I skipped ahead and put the VFD on to the lathe before changing the motor..... and it works awesome!

 I have tested it and with the lathe in top gear I can start off at about 40hz no vibration, as I creep up to 50hz the vibration starts to develop getting worse until the hz gets to roughly 55hz then it comes good? at 60hz even to 70 it runs smooth as a dream!

After some reading up apparently there is a thing called 1 X rpm vibration where when the motor is running at a very close speed to the driven load it can cause a harmonic vibration, solution is to change the gearing or the motor as often the motor has unbalance or something at its rated load speed. Weird anyway.

So once I machine a bracket to suit the flange face on the new motor I will put it on and hopefully all issues will disappear. Very impressed with how smooth it can run with vfd, need to make a bracket for a speed pick up on spindle and then I will be able to pick rpm with the dial and gear changes! Flasher than a rat with a gold tooth!

Cheers


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## wa5cab (Oct 24, 2015)

Once you get the other motor installed and running, you can quickly determine whether the vibration was from the motor or something else on the machine.  If the Round-head is like most of the era, with a countershaft of some sort and with back gears, you can probably disconnect just the direct drive without engaging back gear and run the countershaft alone.


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## Str8jacket (Oct 24, 2015)

wa5cab said:


> Once you get the other motor installed and running, you can quickly determine whether the vibration was from the motor or something else on the machine.  If the Round-head is like most of the era, with a countershaft of some sort and with back gears, you can probably disconnect just the direct drive without engaging back gear and run the countershaft alone.



I have been testing the old motor in this way, no vibration? It is strange because without the vfd the speed of the motor never changed, and the vibration only ever reared its head when the gear box was in high gear, (spindle at 1000) chuch, no chuck, faceplate you name it I have tested it!

I should clarify the vibration was more of a unbalance / wobble rather than a rumble or grinding. it always sounded and felt smooth, just the whole machine would develop a wobble. I suppose that is what has sent me round in circles. Under any load there is a slight knocking noise from the motor when listened to with a screw driver up to my ear, disconnect the belts and it is quiet.

In retrospect I have had engines at work 45litre cummins that have had a build up of dirt in the harmonic balancer and a vibration will occur at different rpms, change the throttle 100rpms and it will disappear. Doesn't take much either.


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## wa5cab (Oct 24, 2015)

Could be one of the bearings.


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## Str8jacket (Oct 24, 2015)

In the motor? Or the head stock gear train?


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## wa5cab (Oct 25, 2015)

In the motor.  You said that you could hear something in it using a screwdriver as a stethoscope.  That's just a guess, of course.


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## Str8jacket (Oct 25, 2015)

Yep was using it as stethoscope. Noise was there before and after i replaced the motor bearings. Only under load. Belts off it's perfect. Old and new bearings the same


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## Str8jacket (Nov 13, 2015)

Well new motor fitted and done. The unbalance is still there at around 950rpm, 50 rpm either side ot is gone? Must be something in the gear box that gets into sync at that rpm and creates the harmonics. It happens when using the high speed selector and it will happen if i put the range at 700rpm and over speed the motor to get to 950. Or if i have it at 1000 range and slow the motor a little. It just so happens that it was at 50hz when i noticed it. Which is what my mains supply is. 

I finished the Vfd install and made a frame for the box. Used all the machine start forward reverse levers to control still so its easy to use. Picked up a tacho that seems to work well. Overall happy with it and can easily work around the wobble.


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