ThankyouReading around a bit, it looks like they made them in two 8 speed options and a 16 speed with a two-speed motor, with the lower speed, basic model aimed at schools and training establishments and the higher speed aimed at industry. That might be in your favour as a school one should have had an easier life.
From what I have read, it was just a different motor, different drive pulleys and a different data plate. The headstock bearings in particular were the same.
There's a manual at vintagemachinery.org but it is a bit jumbled up as there was never really a 140-specific one. If you look at the picture of the data plate for the 16-speed one below, it is the just a 750 with two speed motor. If you have native, full fat 415v three phase, it could be as simple as just buying a new motor. No new wiring or control circuitry needed. If you are running from a VFD, just buy a 2800rpm motor and have infinitely variable speed from less than 34 up to more than 1500.
There is a Harrison group at groups.io so you could read their back catalogue of messages to see if the issue has come up before.
A previous discussion here:
Harrison 140 Motor Frame Type
Does anyone know what sort of motor I need to buy? There seems to be a number of frame options. Do new motors come with different spindle sizes? Any motor brands to look for? I’ll be running it on three phase mains supply.www.mig-welding.co.ukSpeed Chart for Harrison 140 Lathe, 45 -1000RPM. 80203421 - G&M Tools
Speed Chart for Harrison 140 Lathe, 45 -1000RPMgandmtools.co.ukSpeed Chart for Harrison 140 Lathe, 34 - 750 RPM. 80210542 - G&M Tools
Speed Chart for Harrison 140 Lathe, 34 - 750 RPM.gandmtools.co.ukView attachment 367105Harrison 140 3 phase motor information wanted.
Harrison 140 3 phase motor information wanted.www.madmodder.net