Hydraulic Gearing for a Lathe?

[Peter Cook 6Participant @petercook6]

There is an Ebay listing for a used Taig lathe (#276300583143). It has a “variable speed hydraulic unit” to provide variable speed drive to the lathe.

I was just interested in what it was capable of, and wondered if anyone on here can recognise the unit from the two (very limited) images on the listing?

[DC31kParticipant @dc31k]

It is a Kopp variator, a larger model of which was used in the Chipmaster. Goes from 1/3 input speed to 3x input speed, so 9:1 speed range (which, inter alia, is not achievable on a VFD). Plenty of info. online on the model range and their operation principles if you are interested.

[Peter Cook 6Participant @petercook6]

Thanks.

[Ian PParticipant @ianp]

I have never heard a lathe running with a Kopp but I vaguely recall being told they were noisy, perhaps an odd choice for a very small lathe.

I have a VFD on my drilling machine which is set up to give a 30:1 speed range

Ian P

[Ian P]

On Ian P Said:

I have a VFD on my drilling machine which is set up to give a 30:1 speed range

Could you expand on that please. Standard UK mains frequency is 50 Hz. A 30:1 range would mean the VFD worked over a range from 3.3Hz to 750Hz.

[Ian PParticipant @ianp]

I use 4Hz to 120Hz  which by my calculation is 30:1

Motor is an ancient 1/3HP ‘square’ Hoover and the VFD an obsolete Siemens. 4Hz give very little torque (but then not much is needed when tapping M1.5).

Ian P

 

[DC31k]

On DC31k Said:

It is a Kopp variator,  […]  Plenty of info. online on the model range and their operation principles if you are interested.

Fussy little devils, it would appear !

https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/03_Machine_Tools/KOPP_Variator/KOPP_B_Series_Variator_Op_Serv.pdf

…although I do fondly remember using one on a round-head Chipmaster

MichaelG.

.

Edit: __ Must confess I’m a bit bewildered by the use of the word ‘hydraulic’ … I thought the Kopp was essentially a mechanical device.

[NealebParticipant @nealeb]

I suspect that someone who doesn’t know how it works has looked at the outside and assumed that it has a car-style torque convertor inside.

[Nigel Graham 2Participant @nigelgraham2]

Hmmm. I noticed in the manual that it is designed to use one and only one type of oil, and any other could ruin it!

I have thought the smaller hydraulic torque-converter, such as the ‘Eaton’ units that have found homes in various Diesel-outline miniature locomotives, idea for driving some machine-tools. Very expensive though!

[DC31kParticipant @dc31k]

I think the inventor is one Jean Kopp. UK Patent GB618774A. It looks like some of his previous work was on variable pitch propellers.

In passing, This document popped up, which is interesting:

https://ntrs.nasa.gov/api/citations/19830011852/downloads/19830011852.pdf

[mgnbukParticipant @mgnbuk]

I can only recall one project that used Kopp Variators when I worked for a machine tool rebuild company (on a Spanish built Tadu manual facing lathe ). This had two variators, one for spindle speed, the other for feeds & both were stripped and re-bearinged during a rebuild. I have a recollection that they were difficult to set up again afterwards, but don’t recall having any issues once the machine went back to it’s owner.

British lathe maker Binns & Berry used hydraulic spindle drives on their range of “Trident” lathes. These used a variable delivery pump to drive a hydraulic motor on the headstock, with the pump output controlled by a modified windscreen wiper motor. The wiper motor had a potentiometer added to the output arm for basic position feedback & a simple electronic control unit that had another pot on the operator panel to set the speed. The headstocks had 3 manually selected gears to give a wider speed range. The ones I worked on were leaky & the hydraulics ran hot. I guess it must have made some kind of sense economically when the machines were designed, as early DC motor / thyristor drives in the 30hp range were very expensive in the ’70s (and not that reliable).

Nigel B.

[DiogenesParticipant @diogenes]

I see the auction ended early.. ..anyone here get it..?

[Diogenes]

On Diogenes Said:

I see the auction ended early.. ..anyone here get it..?

I do hope so … it looked rather intriguing !

MichaelG.

[DiogenesParticipant @diogenes]

I thought so too – and it wasn’t that far away if bidding didn’t go well..🤔

[andywinParticipant @andywin]

The owners bringing it over tomorrow. I was looking for a micro lathe for making watch parts and some delrin tooling so would seem to be ideal.

[Michael GilliganParticipant @michaelgilligan61133]

Do share the joy please,  andywin

Details of the drive system would be particularly interesting

MichaelG.

[bernard towersParticipant @bernardtowers37738]

When I machine Delrin I use pcd inserts they leave a good finish with good dimensional accuracy.

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