Pulley

Hi again

One other job I have to do to get my mill going properly is sort out the pulley on the motor. The motor that came with the mill blew up (literally), but luckily an extremely kind chap on the Dore Westbury group gave me a spare motor he didn’t need any more.

Trouble is, it has a larger diameter spindle than the original motor I had, and so the original pulley doesn’t fit, which means I can only use one speed. So what to do….

1) bore out the original pulley to fit the motor spindle

2) Turn a new one on the lathe - which would be good lathe practice for me, but I’d be concerned about messing it up.

Thoughts?

Steve

The pulley on the right looks to me marginal if the hole is to be bored to the size of the left one. Measure the diameter of the bottom of the smallest pully wheel to see if it is bigger than the proposed bore. I would not be happy with less than 2mm, 0.080" wall thickness after boring.

What size is the original pulley bore? what size is the new motor shaft?

It’s an optical illusion! The top faces of the two pulleys are the same size. The hole on the right pulley is just under 1/2”. The hole on the left pulley is 3/4”. The motor shaft diameter is 3/4”.

Steve

Edited By Steve355 on 28/10/2021 23:22:39

You appear to have a chunk missing from the pulley you intend using. Might cause noise and accelerated belt wear, possibly affect the finish if it causes vibrations too.

Rob

If you're just expanding it 6mm, you might as well just bore it out, just make sure to set it up running true.

In the last photo I’m assuming the bottom pulley is your original with the 1/2” bore, it has a large piece missing from the rim. I would make a new one, not a difficult turning job.

However it would also be possible to effect a repair and bore out to suit the new motor shaft. If you want to go this way the repair can be done by turning down the large damaged pulley until you are say 0.200” smaller than the bottom of the V diameter then make a new V section from mild steel. Make the bore of this an interference fit, allow 0.001” per inch of dia. Heat the new pulley “ring” until it blue then fit over the pulley you turned down and allow to cool. Forgot to say I would make a step on the turned part of the original pulley and a matching recess in the new V to facilitate location when fitting.

I have used this method many times converting flat pulleys to V pulleys.

John

Nowt wrong, I would think, with filling the ‘space’ and machining to match the profile of the pulley. That might mean machining away and fitting a new piece (likely by brazing) or filling the gap with braze and machining.

The latter might slightly alter the balance, but I doubt it would be noticeable.

..whilst bearing in mind that one can buy a 3 step A section V pulley with 3/4" shaft for about £25..

This from a UK supplier RG Wylie & Co via their Ebay shop..

https://www.ebay.co.uk/itm/173869803951

..depends how you value your leisure time..

You could kill two birds with one stone perhaps?

Measure the overall length, and the groove spacing of the original pulley, and the OD of the shaft on the replacement motor..

For the moment, we will assume that the shaft is exactly 0.750" diameter

Bore out the original pulley to 1.000 or 0.875" (Whichever you choose ) ensuring that the bore is square to the faces of the pulley.

Measure the bore accurately

Turn away the damaged groove

Turn up a new pulley with just one groove, the same as the largest diameter groove with the piece missing, but with a "nose" to make it so that the O A length is the same as the original pulley, and that the groove spacing will be the same as the original..

Turn the OD of the "nose" to 1.001" or 0.876" (i e a thou bigger than the new bore in the original pulley, and bored to 0.752". )   This should give a close but sliding fit on the 0.750" shaft of the new motor.

It is easier to turn an OD to match a hole than to bore a hole to match an OD.

Put the new long nose single groove pulley into the freezer and leave for 24 hours..

After 24 hours, heat the oven to Gas Mark 6,. You are looking for 5 - 600 degrees

"Cook" the remains of the original pulley for at least an hour, to ensure that it is REALLY hot.

Place it in the oven, small groove down, preferably

Have a copper/hide mallet to hand, or a hammer (At least 2 lb ) and a piece of wood; in case you need it.

You will also need another piece of wood or ply on which to put the original when it is removed from the oven. , and placed on the floor.

Remove the new single groove from the freezer and wrap in a towel to keep it cold, while you remove the original from the oven.

Place the original on the ply, small diameter down and quickly unwrap the new long nose groove, and drop it into the remains of the original pulley.

Hopefully it will drop easily into place. It it does not, assist it with the copper/hide or the the 2 lb hammer with the piece of wood between the hammer and the pulley.

You need to be quick about this so that the original does not cool, or the new piece warm up too much.

When everything has cooled to the point where it can be safely handled, admire your modified pulley and fit it to the motor.

Hopefully, once the motor and pulley are installed and aligned., the D W will be ready to function with a long belt life and the full designed range of speeds.

(Straight edge across the face of the motor pulley and of the pulley that it is driving. )

The "Heat and Freeze" technique works, or did for me when fitting a 1" diameter bar into a reamed 1" hole in a cast iron base..The 0.001" interference has left the bar securely in the cast iron base.

HTH

Howard

Edited By Howard Lewis on 29/10/2021 06:34:39

That would be ideal, but not the right size unfortunately. ODs need to be 4, 2-3/4, 1-1/2

😢

Just thought of an alternative and maybe easier way!

Measure length and groove spacing of the damaged pulley

Bore / ream the damaged pulley to 3/4"

Turn a single groove pulley to replace the damaged area, and bore out to say 1.5" diameter.

Measure the bore accurately..

Reverse the damaged pulley, and machine away the broken groove to leave a central spigot, 0.001" larger say than the bore of the new single sheave.

Heat and freeze as before , and hopefully you will be back in business!

Howard.

Does the new motor have the same rpm as your original?

What HP is your newly acquired motor?

Fatter shafts normally mean higher HP or a much older motor.

Too much power can temp over stressing little mills that aren't light industrial built.

Both motors are 1hp, and 1450 rpm as far as I can tell - the plate is damaged on the original one. The “new” one donated to me came from an older Westbury mill. So I think I’m ok on that count.