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Portass Dreadnought Lathe
Drive System
Dreadnought Headstock & Carriage Photographs
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Good "wrap-around" is essential for successful flat-belt operation and when I first saw the remarkably well-preserved lathe pictured below the owner had arranged the flywheel-drive belt so that, instead of passing under the jockey pulley and increasing the belt contact, he had passed it over the top - and so reduced it. It says much for the machine's capabilities that he had, nevertheless, managed to make two model locomotives before the error was pointed out to him.
Originally, the lathe was supplied with heavy cast-iron covers over the changewheels and front section of the large drive pulley but, unfortunately, these have been lost. The headstock-bearing drip-feed oilers were not originally fitted, but every small lathe benefits from their installation - they are completely reliable (if rather fragile) and you can see exactly how the oil supply is functioning.
A version of the much lighter "Model S" was also available fitted to a stand of this configuration - but, usually being on a tight budget, the typical "S" buyer can seldom have been tempted by such luxury and consequently  these versions are particularly rare.

Above: handwheel adjustment of the belt tension was provided by arranging for a jockey pulley to wrap the belt more tightly around the large drive pulley.

In its original form the flat belt drive from motor to countershaft would almost certainly have been a cause of trouble. The motor pulley was too small for effective grip and a change to a V belt set-up would have been a great improvement - as the first owner soon discovered.
As a point of interest, on many of the smaller American South Bend lathes the electric-motor shaft carried a V pulley, with a V belt driving onto large-diameter, narrow, flat pulley. This rather unusual arrangement (of a V belt on a flat pulley)  worked very well even if, to modern eyes at least, it appears illogical. 

Home     Machine Tool Archive      Machine Tools for Sale and Wanted
E-MAIL   Tony@lathes.co.uk

Portass Dreadnought Lathe
Drive System
Dreadnought Headstock & Carriage Photographs
Portass Home   Model Range Advert   Portass Model S   Dreadnought Photographs
Mk.5 Portass   Portass PD5   First Portass Lathe   Portass Model C    Shaper