Startrite 352 Problem...

[cowfoot]

Hoping a fellow 352 owner (or someone with more mechanical sense than myself!) can help...
The motor pulley keeps working its way off the drive shaft. It's secured by a strip of metal that's tightened up to fit a corresponding channel in the shaft with a grub screw -

Doesn't strike me as a particularly secure fix, anyone got any better ideas?

Thanks in advance!

 

[kevinlightfoot]

Check that the grub screw is not a locking screw for another screw underneath it,this is common practise in well engineered machines, tighten both screws and you should have no problems,if it's any reassurance for you I have had my 352 for 35years without any problems other than a coil which packed in and that was easily repaired by an electrician and a replacement drive belt

 

[Fitzroy]

I'm no expert but key-ways, and keyed pulleys are pretty standard fair for machinery. On my machines the keys are a pretty tight fit to the key-way and pulley, I doubt I could remove the pulley with the belt correctly tightened, and the belt alignment pulls the whole arrangement back to the correct position. The grub screw in the pulley seems secondary to holding the whole lot secure.

 

[Lons]

That design of keyway is well proven. As said, check the grubscrew. Try turning in in with the pulley off and look inside the bore, check also that the grubscrew or pulley thread isn't stripped.
Check also that the key itself isn't worn, easy to make one if it is. If all ok you can add some security by adding threadlock to the grubscrew.

I have the same machine with no problems and it's probably 35 years old.
Bob

 

[Jacob]

Check that the grub screw is not a locking screw for another screw underneath it,this is common practise in well engineered machines, tighten both screws and you should have no problems,if it's any reassurance for you I have had my 352 for 35years without any problems other than a coil which packed in and that was easily repaired by an electrician and a replacement drive belt

Ditto no probs for 40 years (at least I think it's about 40!) except one bearing replaced. So it's not a design fault!

 

[dickm]

If the pulley is coming off the shaft when the machine is running, something is seriously out of line. Just a guess, but is the motor securely tightened down to the mounting plate? If it's loose, the belt tension coul just pull the pulleys out of line. The 352 is pretty much bomb proof!

 

[Hot stuff]

Just beat me to it there ****, I'd be looking at the same area for a problem. It's not a 3 phase converted to single or had a replacement motor by any chance?

 

[woodpig]

As said a Woodruft key has been a standard way of attaching a drive pulley to a motor for many years and will no doubt continue to be so. The key is normally a tight fit in the shaft but can be held in place with loctite if it's a bit loose. The pulley is often held on with a single socket set screw but there may be two in some cases, one above the other.

 

[kevinlightfoot]

I don't think mine is fitted with a Woodruff key it is a normal type key which fits into a flat bottomed key way in the motor shaft.A woodruff key is semicircular in shape and the curved edge fits in the shaft.I think it interesting that a couple of chaps have suggested that It may not be the original motor and this may well be the root cause of your problem let us know how you go on I'm very interested.

 

[cowfoot]

Thanks for all the helpful advice.
The key was a bit loose in the channels, so I made a new one. Drilled a shallow indent to fit the end of the grub screw too, it's nice and tight now. If it works loose again I might try some Loctite but I guess that's a last resort.
I've also made sure all the bolts are snug on the mounting and the belt is tensioned. It's a very well designed machine, simple but solid.
The motor's a noisy old b*gger (especially when slowing down) but all this tinkering about has reassured me that it wouldn't be too much bother to swap it out when it finally pops its clogs.

 

[kevinlightfoot]

Great,sounds like you've done a proper job,by the way mine is devilishly noisy also.All the best Kev.

 

[Lons]

Great,sounds like you've done a proper job,by the way mine is devilishly noisy also.All the best Kev.

+1
Mine is a noisy old beast as well but wouldn't swap it. \/ ( that applies to the missus as well :lol: )