Author Topic: SW5 gear sets  (Read 455 times)

0 Members and 1 Guest are viewing this topic.

Offline roger h

  • Full Member
  • **
  • Join Date: May 2012
  • Posts: 92
  • Location: ulverston, cumbria, uk
SW5 gear sets
« on: 28 Apr 2020 at 20:47 »
A couple of us in the UK are producing some new SW5/DT/TT type gear sets. See the attachment for details.

Quote from: Attached document

The vintage period TT model and later DT and SW model Douglases are fabulous machines, and have a long history of successful use in sprinting and racing. Most of the successful sprinters have used Norton (Sturmey Archer) gearboxes, as suitable internal ratios are available. The Douglas factory fitted gearbox (SG, TG, YG, UG etc) have not been much used, as the TT ratios which would have been suitable are unknown, and the standard DT ratios are not suitable, these providing a choice between :-

a)   an acceptable first gear to get off the line, but “flat out” in top gear at 40-50 mph
b)   a high top speed, but an impossibly high first gear, making starting very difficult.

I do not have details of the TT gearbox ratios (this has been the subject of much recent discussion on the Australian -  led Douglas discussion page, however we are all still in the dark as to what Douglas fitted to their TT gearboxes).

There must be many  SW5/6 or TT type Douglases around, brilliant machines with searing acceleration, good brakes and handling (see the Titch Allen and Alan Cathcart road tests for example), which are not used on the road, or in competition, with the DT gearbox ratios as the main culprit.

Some twenty years ago, Doug Kephart in the USA produced three sets of new gearbox gears, with suitable ratios, which allowed an acceptable first gear start combined with a high top speed. These sold out immediately, and there have not been any others available since.

Chris Fisher and myself (Roger Harrison) have now commissioned a further  ten sets of gears, to be made in the UK under our supervision. We are very grateful to Doug Kephart, who has very kindly allowed us to use his original drawings and specifications, and we plan to have these gear sets available this year.

Each gear set will consist of a solid layshaft with 21, 18 and 14 tooth gears, and mainshaft gears of 16 tooth sleeve gear, 19 tooth slider gear and 23 tooth free gear.

Several factors have resulted in the finished price for a set of gears being less than in previous years, and we expect this to be £600. Four sets are already reserved, so the remaining six sets will be available.
We would be pleased to hear of expressions of interest at this stage.

Please reply to:-  r.harrison135(at)

Attached text added to post - Dave, 29 Apr 2020
« Last Edit: 28 Apr 2020 at 21:46 by Dave »