Harmonic Vibration At 1000rpm

S

Str8jacket

H-M Supporter - Gold Member
H-M Supporter Gold Member
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May 17, 2015
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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?
 
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.
 
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.
 
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.
 
It will be a twin belt one may have stretched a bit more than the other also check main bearings
 
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.
 
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.

20150911_073508-1.jpg 20150911_073352-1.jpg
 
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)?
 
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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