Gearbox numbering

[saluki42]

Hi there I have at last got to the bottom of the boxes which comprise my 34 Model Z, with some worrying finds, but there is one puzzle I could do with some help with. The engine and frame number match what I would expect however the gearbox is the problem as the only numbers I can find comprise of a letter 'K' in a Letter 'D' followed directly by 'V2' then slightly further to the right and upside down are 'D1' followed at a short distance by a capital 'P'.
Could anybody enlighten me, is this possibly the correct gearbox for my Model Z?

[eddie]

According to Jeff Clew's book of the Douglas, a 4 speed handchange gearbox with an E/ was listed for the Z & Z/1 models. A later 4 speed handchange gearbox prefix P/ was listed for the 1935 600sv & 750sv models. Around this time, some gearboxes had stub teeth and others had involute form teeth, so individual gears may not be interchangeable between boxes.

  Regards,
                Eddie.

[Doug]

Full rundown on the applicable gearbox prefixes are this:

D/  1934 Z (Wessex), Z1 (Powerflow) foot-change
E/  1934 Z (Wessex), Z1 (Powerflow) hand-change

J/  1935 Z (Wessex), Z1 (Powerflow) hand-change
L/  1935 Z (Wessex), Z1 (Powerflow) foot-change

P/  1935 600 & 750cc , 4-speed, hand-change, involute
Q/  1935 600 & 750cc , 4-speed, foot-change, involute

The superimposed DK is the Douglas of Kingswood trademark. The V2 is some sort of inspection mark; you find them on engine cases too. The trans number is stamped on the top face of the inner end cover and not on the transmission case. The format should be the prefix, slash, and a three digit serial number. While this is not a Z/Z1, it shows the location and format:




-Doug

[saluki42]

Thanks Eddie and Doug, I'll have to look in the boxes for the other gear boxes to see what other parts are there to try to find a number

Chris

[saluki42]

Hi Doug a quick follow up to your reply.
I've had a look at the inner gearbox cover and the number is "6Q/220" which seems to indicate a 1935 600cc with foot change however, the gear selection is operated by rack and pinion through the top of the gearbox. Did they use the same system for both hand and lever change models?

Chris

[Doug]

Chris,

They just altered the end covers which contained the gear change mechanism. Both hand and foot shift ended up operating a rack in the inner cover that turned the gear selection drum inside the gear case proper. [Correction, only the hand shift worked the pinion via a rack.] I had a look to see if they used the same inner cover for both and perhaps someone has just swapped the outer cover. I have a 1935 foot shift gearbox on a ohv model, and while essentially the same gearbox turned ninety degrees and mounted up under the saddle, sharing many the same parts, am not certain the end covers are exactly the same as the side valve models. Pictures of the foot shift on the Z and Z1 are rare, so I could only find the 1935 catalog image. But it does look like the foot shift cover was much larger and a different outline than the corresponding foot shift version (like the ohv hand- vs. foot-change), so it does not appear you can mix inner and outer covers. Which leaves me a bit baffled! I did check the gearbox code list in the appendices of Jeff Clew's book "The Best Twin" to see if I accidentally got the codes reversed. I did not, but I have noted a few other errors in the list before. Anyone else want to chime in? 

1935 model Z (Wessex) with foot-shift:



1935 model Z1 (Powerflow) with hand-shift:




-Doug

[Correction. 16Jan21 Doug]

[Ian Hand]

Hello again, I am working on the gearbox of my Z1 and it has an L prefix.  Reading the thread it seems that it's the right gearbox for the bike. Foot change.
It looks to me like the kick start return spring has been removed. I would appreciate it if someone could have a look at the pictures and confirm that the coil spring is missing on the inside of the outer casing.  Some internet research tells  me it might look like the spring in a Burman Hurth. I have attached a screenshot of what I think it might be.  Help would be appreciated
I am also having trouble timing the gear change.  It was not working properly before I stripped it down, I suspect whoever needed the kick start spring just threw it back together without regard to correct timing.  Any help would be appreciated.









[Attachments converted to linked images. 04Jan22 -Doug, Admin]

[Doug]

See this post here:

https://www.douglasmotorcycles.net/index.php?topic=7349.msg28049#msg28049

Note that there are 3- and 4- speed versions of this spring which are very similar in appearance. Both are usually stocked by the London Douglas Motor Cycle Club prewar spares department.

Also note that there is supposed to be a floating collar on the kick start quadrant shaft to prevent the inner end of the spring from wrapping too tightly around the pivot axle. It is the omission of this that typically leads to spring breakages at the inner end of the spring.

-Doug



[fix typo.  04Jan22, Doug]

[Ian Hand]

Thanks Doug,
Yes I have the floating collar, thanks for the information, I will contact the LDMCC and order the  part.
cheers

[Dads bike]

Morning
A little late in following up on this thread, but hay ho
A couple of pics of a Z1 four speed foot change gearbox. The bike was Sold by the Birmingham national motorcycle museum a little while back.
Steve

[Dads bike]

Morning Ian
Ref the kickstart return spring, see attached pic of a four speed hand change end cover with the correct spring.
When reassembling don’t forget part nos 7763 rubber buffer large and 7764 rubber buffer small. Also in the pic.
The small buffer is used on the stud where the return spring outer coil mounts.
Obviously these are unobtainable parts but 1/4” rubber petrol pipe cut to length works well enough

Steve

[Ian Hand]

Thanks Steve,
That is the bike I bought from HandH Auctions 12 months ago.  It's now in my workshop in Australia in a lot of pieces.  There are a lot of parts missing from the gear box and rubber buffers are just 2 of the missing parts. All the springs are missing too. I suppose someone needed them, The gearbox has been apart some time ago and not re assembled correctly.  Not to hard to work out the assembly. 

[Dads bike]

Morning Ian
Ref missing four speed gearbox parts, there is someone in Australia selling clutch and gearbox parts on ebay at the moment his sellers I.d is chenard1913
His post cost to the UK make them unviable but within AU maybe cheaper you could be lucky?

Steve

[Ian Hand]

Thanks Steve, Yes I have been following that stuff. Mostly earlier parts than my 1934. So far nothing of use to me.  If you need anything posted to the UK let me know. We have an Auspost contract and may be able to get a much better shipping price than you would get from an ebay seller. One of the strings to  my bow is I run the 3PL contract for Hobbyking.com in Australia and New Zealand.