“Pin-Up” for the day

[Michael GilliganParticipant @michaelgilligan61133]

From

https://ia800705.us.archive.org/4/items/wolfjahnkatalog1903/Wolf%20Jahn%20Katalog%201903.pdf

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MichaelG.

[peak4Participant @peak4]

Interesting concept, so long as the phasing and drive angles are correct.
It looks as though the lathe designer considered that, since the top slide  equivalent doesn’t swivel to allow for tapered threads.

Bill

[PeteParticipant @pete41194]

An interesting lathe Michael. The exact same universal and telescoping drive was used on ornamental turning lathes and would be much older than that Wolf Jahn lathe. In fact the same type of drive was still used for the power table feed on my little Atlas horizontal mill built in the early 1950’s. I believe most horizontal mills used it unless they had an expensive built in secondary power feed design.

[Nigel Graham 2Participant @nigelgraham2]

Interesting… I wonder why the power feed was on the top-slide rather than saddle.

I take it the light dots round the pulley are holes, allowing for dividing, though there’s no obvious detent for that; nor mounting-pad for such. Perhaps it was an optional extra. The top-slide’s generous upper area suggests plenty of room for mounting the milling-spindle, vertical-slide, etc; shown in the book.

One extra caught my eye: a proper boring- and facing- table attachment with vertical feed, the screw for this operated by a handwheel between and below the shears. I don’t recollect seeing any such mentioned for any other make of lathe. I like the 6-jaw independent chucks also available.

 

Looking at the headings, I guessed Albert Jahn, the company’s founder in 1887,  had invented some particular aspect used on this machine. The catalogue suggests it was the collet system; well described by a labelled, sectional drawing of the headstock. I could be wrong though as I don’t know German.

 

No, it won’t turn tapers unless it is provided for a follower attachment. Another Optional Extra – but I didn’t see one in the book.

A few years ago a You-Tube link someone posted on here, led us to a large lathe being used in Russia to make a screw-type log-splitter. This uses a big, tapered, auger-thread the lathe could cut by the long and cross-feeds being geared together, thereby generating the taper. I thought then, a very good system but potentially a recipe for disaster unless used with great care. (You’d need the cross-feed withdraw, not deepen, as the long feed continues.)

 

Rather elegant little machine, isn’t it? The bigger W-J lathes had distinctly blockier beds; but all no doubt high-grade machine-tools. I wonder if there are any ‘C’ types still about and even better, in use.

 

Isn’t that general form of telescoping drive called a “Cardan Shaft”, or is that a particular type? I have seen the term used only for things like locomotives. My small Denbigh H4 horizontal mill is supposed to have similar although it came to me with only the worm-wheel in place on the table-screw; the rest either lost or was never fitted from new.

[renardiere7Participant @renardiere7]

Nigel,

The reason the power feed connects to the topslide rather than the saddle is because there is no saddle. The topside is mounted to the cross slide the whole unit is generally termed a carriage and it is locked to the bed with the hand screw that can be seen beneath.

The holes on the pulley are for indexing and generally there is a pin at the base of the outboard end of the headstock, probably obscured in this case by the banjo mount.

The cardan joint was attributed to Gerolamo Cardano in the 16th century so I suppose the original name for the universal joint and probably more correct.

[Nigel Graham 2Participant @nigelgraham2]

Thank you for that!

I see what you mean, but am a bit surprised it has a fixed carriage rather than the driven saddle already common practice by the 1900s era of this lathe.

I examined the engraving again and it’s not at all clear where it could hide a dividing-detent, which suggests either it was round the back of the headstock or simply not on the Model ‘C’ anyway. If so the pulley was drilled simply as a part common to other Jahn lathes of similar capacity.

 

My copy of Newne’s Practical Engineering Data Sheets credits the universal joint to Robert Hooke, but a little more digging courtesy of Wikipedia gives, basically:

Gerolamo Cardano – 16th century mathematician, describing gimbals not shaft drives.

Schott – 1664, mistakenly described the mechanism as a “constant-velocity joint“.

Hooke a few years later, analysed it and found the single set of gimbals is not a constant-velocity transmitter, but is linked to the geometry of the sun-dial hence that of the Earth!

Hooke – 1676 – coined the term “universal joint“; proposed that a pair at 90º to each other on the ends of shaft form a constant-velocity joint.

The familiar arrangement of two Hookes’ Joints on a telescoping shaft, as on that lathe and horizontal mills, is thus a form of constant-velocity joint.

18 – 19 C: The term “universal joint” became common in English language use; adopted from translations of French engineers’ and mathematicians’ studies.

Early 19C, French followed by English translators began to be credit Cardano for the Universal-Joint.

All the others such as spherical couplings, the Spicer (as in Hardy-Spicer) Joint based on that, and a weird and wonderful array of long-vanished alternatives, are all generally based on Cardano’s original gimbal principle and Hooke’s later developments of that, to form the Constant-Velocity Joint.

Which the universal joint alone, is not.

 

Some, such as the Hardy-Spicer coupling in 4WD cars, and its simpler pot-joint equivalent, simplify the 2-UJ method to one mechanism.

So Cardano discovered the geometry of the gimbal.

Hooke took that further to the geometry of the sundial and to the machine-drive mechanism; hence the name Hooke’s Joint. Via a 17C terminology mistake by Gaspar Schott!

 

So really, Cardano deserves the accolades for the gimbal joint, Hooke for the universal joint and its use in the constant-velocity drive; the latter being called that and used on machine-tools, the Shay locomotive and other machines well before Halfords had a market for car spares.

[Michael GilliganParticipant @michaelgilligan61133]

I think this deserves another “Wow” for Wolf Jahn

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MichaelG.

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