Removing belt pulley from spindle properly

[RainbowsParticipant @rainbows]

So the page here says that to avoid belt pull issues the pulleys are put on ball bearings with a peg transferring the rotation to the spindle. Stops belt pull affecting accuracy/surface finish or something like that.

Am I copying the concept right? There is just a peg going through a hole in the pulley to screw into the spindle. I am sure that Smart & Brown had their reason but I am looking at it and it just looks like a reinvented version of the keyway.

[RainbowsParticipant @rainbows]

[David JuppParticipant @davidjupp51506]

No – more complex than that. I have a S&B plain lathe and have replaced the bearings for the pulley cluster. The pulley is supported by 2 ball races from a central hollow sleeve. The sleeve is bolted to the end of the headstock.

The spindle passes through the aforementioned hollow sleeve and runs in tapered bronze bush at nose end, and a matched pair of angular contact ball bearings at rear end to take thrust (at least on my own lathe). The 'peg' arrangement transfers drive from pulley to spindle.

On the S&B, you can remove the spindle, yet still run the motor/belt as the pulley remains in place.

[RainbowsParticipant @rainbows]

Oooh I had been misreading that sleeve as just floating on the spindle. Thanks a tonne.

[Michael GilliganParticipant @michaelgilligan61133]

That's a classy bit of engineering

… Good job I haven't got any room, or I might be looking for one.

MichaelG.

[Ian PParticipant @ianp]

Posted by Michael Gilligan on 01/12/2016 19:34:21:

That's a classy bit of engineering

… Good job I haven't got any room, or I might be looking for one.

MichaelG.

Classy yes, but not really required nowadays.

I think the construction overcomes some of the disadvantages of the legacy belt drive system. Heavy cast iron pulleys, flat belt with non uniform section and a joint, also the side load on the spindle from the belt tension.

Polyvee or even high quality single vee belts have much more constant section so would impart little disturbance to smooth rotation, direct spindle drive avoids the belt problem but probably introduces a whole lot of other effects.

Ian P

[HacksawParticipant @hacksaw]

I thought i recognized that drawing …I've got one too….and i like the gentle hummm…. & Tick..tick.. tick… tick.. tick…The growl from the worn back gears is annoying though

[RainbowsParticipant @rainbows]

Would heavy pulleys be a disadvantage? I would have guessed (though I am not an expert) that it would make the drive smoother cause of the flywheel effect or something. If they aren't machined or balanced at all though then maybe.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ian Phillips on 01/12/2016 20:15:13:

Posted by Michael Gilligan on 01/12/2016 19:34:21:

That's a classy bit of engineering

Classy yes, but not really required nowadays.

Polyvee … have much more constant section so would impart little disturbance to smooth rotation

.

Just imagine how Smooooth it would be with the pulleys converted to Polyvee.

< Sigh > … I think I need to lie down for a while.

MichaelG.

[Ian PParticipant @ianp]

Posted by Rainbows on 01/12/2016 22:05:47:

Would heavy pulleys be a disadvantage? I would have guessed (though I am not an expert) that it would make the drive smoother cause of the flywheel effect or something. If they aren't machined or balanced at all though then maybe.

You are right, I would have thought heavy pulleys (probably balanced in this, quality machine) would be a big benefit but they would need to be torsionally locked to the spindle rather than linked through a keyway, pin or spline.

Ian P

[HacksawParticipant @hacksaw]

Yes but when i lift the lid it's "Sigh … what lovely bit of solid engineering ..that's been working faultlessly for 65 years "

Not " Oh its like a cheap modern washing machine"

[RainbowsParticipant @rainbows]

Redo!

Spindle will be going 4000rpm so gonna double up with poly vee and bearings.

[HacksawParticipant @hacksaw]

The chuck will explode.. I've got a kopp variator you can have to get it up to the full 5k

 

My model M  shakes like a dog having a dump when its on the fast pulley

Edited By Hacksaw on 01/12/2016 23:16:33

[RainbowsParticipant @rainbows]

Integral collet, no exploding chucks.

Tho I checked and bison cast iron chucks at 80mm work to 5000rpm

[Ady1Participant @ady1]

I read somewhere that watchmakers prefer plain bearings because spindles in ball races leave marks on the work

[RainbowsParticipant @rainbows]

Posted by Ady1 on 02/12/2016 08:25:09:

I read somewhere that watchmakers prefer plain bearings because spindles in ball races leave marks on the work

I saw the same thing too from a few places. Would consider it myself but I am not sure how well I would pull off matching tapers with good finishes and all that other stuff.

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