On that model TOS, the SN40 and 50 the drive from the motor is taken direct to the gearbox which is a big unit on the far left of the machine, the bit with the levers on it but iit extends down the full length behind the screwcutting box, weighs about 1/2 a tonnne
From there the drive is taken to the feed and lead screws and to the spindle by a hollow splined coupling.
In fact the main gear box shaft is hollow and sits on the end of the spindle so long parts go thru it.
The headstock on these is just a spindle supported in 4 bearings, nothing else. thats the plain looking bit that sits on the bed ways.
Most other lathes drive the spindle and everything is taken off that, on the TOS it's the spindle that is driven.
I used to have this same model lathe until I scrapped it last year, but I still have a smaller one but this isn't the same build up and like most lathes relies on the spindle running to drive the gear train.
Edited By John Stevenson on 10/08/2013 18:25:56