Hi
From playing about with Cowey speedos in the past I can offer the following advice. Firstly, the nut at the bottom of the drive cable to screw onto the special Douglas front hub gearbox (Illustrated above) were made at one time and were available from the LDMCC Spares scheme as were the gearboxes themselves. On Cowey models I have used, the thread on the back of the speedo head is the same or near enough the same to that used on domestic shower hoses and the shower hose itself makes an ideal "outer" for the drive cable. So a length of inner can be adapted to make the drive. It is probably quite a rare item nowadays but there was a small tool available to create a square on the end of the inner using a vice to crush it. To finish the drive cable to look authentic, the chrome plated spiral of the hose shower outer can be covered with thin leather carefully stitched up the side.
The Speedo head itself, again in the examples I have seen, is actually a very simple mechanism. I remember when I came into contact with my first one I spent a while consulting with all the speedo experts and could find no one willing to even look at it. When I took it apart I found that unlike Smiths chronometric and some of the other expensive and sophisticated speedos the Cowey was a simple centrifugal device which with care I was able to clean and repair.
Chris.
