Myford lathe – speed change lever design

[Steve WanParticipant @stevewan33894]

Hi folks,

Greetings! Back again for more help! I'm building a cutting machine with a variable speed change. I saw a Myford lathe video, the turner simply lift a lever, pulled the belt to another pulley, released the lever and went on turning with another speed at ease…wonder owners of Myford lathes could share some light over the working principle of it?! I like to make one to suit the cutting speed of a 5 steps pulley system at the driver motor end.

Appreciates inadvance, any drawing is most welcome either here or email me in private. Guys have a jolly workshop weekends

Steve Wan

[Steve WanParticipant @stevewan33894]

[Gray62Participant @gray62]

Hi Steve, I'm guessing you are looking at clutch designs, there are many ways of achieving this, in my albums, you will see some of the images of my Studer OB cylindrical grinder, one of the images shows the clutch arrangement,

here

hopefully the link works, if not just browse to my albums and look at the Studer OB Cyl Grinder albm.

This is quite a heavy duty taper clutch arrangement and maybe a bit overkill for your application however, this type of clutch is very effective and can be adapted in smaller scales to many applications.

I have a similar arrangement pklanned for my asian built GH1330 lathe, just need to work out how to integrate it into the drive train

regards

CB

[Cornish JackParticipant @cornishjack]

Hi Steve

What you describe sounds like the Myford Tri-Leva attachment. An excellent piece of kit which not only gives you instant speed change'on the run' (3 speeds) but also acts as a mandrel brake for chuck changing etc. The basis is three loose fitting belts from the counter-shaft to the headstock spindle and three levers which have pulleys at their extremities which press onto the outside of the selected belt (and tighten it ) to provide the drive. Selection of any lever de-selects any other instantly. With no lever selected, the headstock is free to rotate and if all three are selected it locks it up. Would be an interesting (and complex) exercise to reproduce and FIVE speeds would be something else again!!!

Rgds

Bill

[NJHParticipant @njh]

Steve

The Myford lathe drive has two levers. One is a clutch and the other is a belt tensioning lever. For my part, if I am going to change speed, I operate the clutch lever to disengage the drive, stop the motor, open the belt guard, release the belt tension, move the belt to the appropriate position on the 4 step pulley, operate the tensioning lever , restart motor and re-engage clutch. (NOTE: There are two speed ranges which are selected by changing the belt between one of two positions on the motor – countershaft drive.) This reads as a rather drawn out process but is, in reality, very quick.

I ALWAYS stop the motor – it only takes a second and I want to be quite sure that there is absolutley no chance of my fingers getting in amongst those belts with the motor.

Regards

Norman

AH!!  OF COURSE THE TRI-LEVER ATTACHMENT!!

Oh well  I'll go and have a lie down I think!

Edited By NJH on 22/06/2012 19:16:30

[NJHParticipant @njh]

Steve

In an attempt to redeem myself the details are HERE

Note to self: Engage brain before posting!

Norman

Edited By NJH on 22/06/2012 19:45:11

[Cornish JackParticipant @cornishjack]

Steve

Just looking at Norman's link, the point about the 2 speed motor is well made, but, coming up to date, the modern improvement is an inverter/3phase motor with speed control … absolutely fantastic!!! I've just fitted same and can hardly believe the improvement. Silky smooth, instant speed change through 3 ranges and belt slip if I get a bit over-enthusiastic!!

Rgds

Bill

[Steve WanParticipant @stevewan33894]

Hi all, CB and Norman

Thanks so much! I got a better picture thumbs up for Bill into making one with 3 phase motor.

I saw those links and downloaded the drawing.

It's a wonderful project if one could understand the basic design principle and apply to Asian lathes.

I think I need to digest a little here for Myford design, I may select a more simplified version like the one I saw in Record Drill press, not the new Record but 15yrs back where those were made in England. It had a lever to loosen and tension the belt. The motor rested on a pivot, able to swing free and engage any selected steps of the pulley but Myford is far better of course.

It's a wonderful experience to mingle with you guys with so much knowledge!

Steve Wan

[Author]

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