the Douglas 'cross-over' 3 speed gearboxes fitted to the
OB, OC, RA, DT, SW, F/G, and like models has a 'crash'
second gear that shifted in and out of mesh with the gear
teeth rather than dog clutches. So the 'box had a pretty
hard time of it - except the DT, which you did not actually
shift during a race.
DT ultra close ratios were more for selecting between
1/8, 1/4, and 1/2 mile tracks I am told. Between that
and a selection of sprockets, all bases were covered.
Preference was to use top, or direct, to minimize power
losses. If you could afford a good selection of sprockets
to cover all your events, you could remove all the gears
and fit a solid countershaft and save a bit of weight.
have encountered two basic DT sets. Close, and the ultra-close
as fitted to mine. The ultra-close ratios are so close,
it makes the machine impractical to use on the road.
it is geared with the sprockets for a good turn of speed
in top. This makes first gear start at about 15mph with
perhaps the clutch fully home at 25mph, if the engine
does not stall.
the sprocket for a more get away in first would see
the engine screaming its lungs out by 45mph. Hence a
wider spread of gears is required. If you can find a
set of road ratios these days, more than likely they
are well used up. I am having a new set of gears made
and should have the new gear blanks machined and ready
to deliver to the gear hobbing firm next week. I look
forward to riding with the new ratios in one of the
events on our Spring calendar.