Douglas 2 3/4 3 speed Gearbox

[Ivan]

Hello Douglas people,

I was wondering if anybody could give me some advice about a Douglas 2¾ 3 speed gearbox?
I have a 1921 Douglas 2¾ with a 3 speed gearbox, clutch (multi dry plate on gearbox) and kick start.
It's a great machine and transports me to the pub on a Wednesday evening without fail! The only issue is it will not stay in second gear no matter how the gear rod is adjusted. I managed to source another already reconditioned 3 speed gearbox to fit while I rebuild my original and source/machine new parts.
When I came to fit I noticed that the casings are different. The shaft that the kickstart goes on does not fit my replacement gearbox.
Please see photo's for the difference.
My assumptions are:
1. That the replacement gearbox on the right is from an earlier model.
2. My gearbox on the left had the attachment points for the kick starter and clutch release/engage mechanism beefed up to prevent failures to the casing on later models caused by over enthusiastic kick starting!
3. If I machine a new shaft for the kickstart / clutch cable mechanism with a smaller diameter for the gearbox then all will be good if I'm gentle with the kickstart or just paddle start that I do anyway.

Any comments and advice will be gladly received.

Thank you.
Ivan.

[Hutch]

...
My assumptions are:
1. That the replacement gearbox on the right is from an earlier model.
2. My gearbox on the left had the attachment points for the kick starter and clutch release/engage mechanism beefed up to prevent failures to the casing on later models caused by over enthusiastic kick starting!
3. If I machine a new shaft for the kickstart / clutch cable mechanism with a smaller diameter for the gearbox then all will be good if I'm gentle with the kickstart or just paddle start that I do anyway.

Any comments and advice will be gladly received.

Thank you.
Ivan.

Hi Ivan and welcome to the forum!. My apologies for missing your post - I was looking through old entries and came across it. I hope I can help you out.

1. Yes the gearbox "1333" is from 1915 to 1919. From the 1916 Handbook it is part number 818D. It is shown upside down so I have rotated the picture to make it easier to compare.

2. Yes I would guess that is what Douglas did. Note that the earlier clutch bridge for the cork inset clutch (1915-1919) is different to the later dry plate version.

3. I think you would be ok to machine up a new shaft to make it all fit together and it would be strong enough.


I am not sure "1333" is the original serial number for this gearbox. It does appear to have been restamped (?) I have a 3 speed gearbox with serial number in the 700's which is the same as your G3/1828 gearbox, so would have guessed that "1333" would have been too high a number?

Not staying in 2nd gear is quite often caused by worn selector dogs, this topic has been discussed a few times on this forum along with possible solutions.

Another thing to check is that by default these 3 speed gearboxes are held in second gear by two springs inside the tube that the selector arms (that move the dogs) slide on. There is a long thin screw through the meddle of the springs which tensions them - if something is amiss with this, or it is out of adjustment - then the gearbox will not be held in 2nd as well as it should be. One thing to note is that the early gearboxes have "4 dog"  selectors, rather than the "3 dog" selectors of the later gearbox's, so the gears and dogs are not interchangeable - (assuming that the internals of "1333" are original). I'm not 100% sure when they changed but guess that it was some time in 1920.

(I did some research into 2 3/4H.P. gearbox serial numbers some time ago and information on these very early 3 speeds is limited so thanks for posting your pictures here to help a little bit more information to the puzzle;
https://www.douglasmotorcycles.net/index.php?topic=9253.0)

Hope this helps,

Regards,

Hutch

[Ivan]

Thank you so much for the reply, some really interesting information. I'm going to rebuild my G3/1828 gearbox over the winter. Looking forward to looking inside or not as the case maybe!
With regard to your comment about re-stamping I'm not sure. It doesn't look like it has been re-stamped to me. The metal is of even thickness everywhere, so doesn't look like it's been ground down and re-stamped or over stamped. The only other marking is a S on the underside. I've included some closeup pictures and a picture of the bike.

So I did machine up a new shaft to fit the earlier gearbox and everything fits correctly and operates correctly now. So the clutch I'm running is the multi dry plate and not the cork, so I wouldn't think that Douglas ever did this combination with an early 3 speed gearbox and a multi dry plate clutch? I'm guessing that when the clutch went from the cork to the dry plate the gearboxes being used where like my G3 box with stronger castings.
I'm being gentle, but all seems good and the bike is so much more ridable with 3 gears! Hills are a lot easier!
I did find a problem with the clutch when it was apart which was a real shame. The inner race has a chunk out of it (looks like it's been there a long time). This allows the ball bearings to sometimes "escape". Not sure how to repair it, I've 3d printed a plastic bush that sits in place of the ball bearings and it's working great at the moment as it is only loaded when the clutch is operated, but not sure it's a long term fix! (I need to check the wear on the bush after 50-100 miles of riding.) I'll do another post with my clutch pictures and see if anyone has any suggestions.
Thanks again for your input about the gearboxes.
Kind Regards Ivan.

[Hutch]

Hi Ivan,

Thanks for the pictures of you 2 3/4 H.P. and the additional information on your gearboxes. I have done some delving into the "1333" serial number and my assumption that it has been restamped is possibly incorrect. I based my assumption on the l920 style gearbox I have with G6/741 serial number and patent information stamping - just like your G3 'box and the number "1333" being a lot higher than I would have thought, given the low production numbers of 2 3/4 H.P.'s with 1915-19 style 3 speed gearboxes in this period.

As there was no patent number on your gearbox, I assumed that it must have been removed. Then I remembered that I had some pictures of some 3 speed gearboxes for 4 H.P. Douglii. This is a very similar, but larger gearbox. I had never looked at them closely but was surprised to note they are stamped similarly to your "1333" box ! and have the word "Patent" stamped on them as well. Your 'box may have originally had the word patent in a similar place as well? I also noticed that they have a letter stamp on them, in a different location , but similar to your "S". I wonder if this is a QA stamp by an inspector, but I am not 100% sure. (The patent was by Walter Moore before he worked for Douglas)

I have started looking at the 3 1/2 and 4 H.P. information from the LDMCC 2014 Machine register in a similar manner to the work I did with the 2 3/4 H.P. machines and have noticed  a few things that may help solve part of the mystery. It occurred to me that although Douglas used the same part number for the 3 speed gearbox for the earlier and beefed up later gearboxes (818D) they possibly used a different sequence of serial numbers - i.e. one for 1915 to 1919 and another one, starting at 101 for the 1920 and later gearboxes. I am currently putting together a new spreadsheet and fingers crossed it will show up something.

Anyway, thanks to your question I have learnt something new and it may solve one of the questions I had on the early 3 speed gearbox serial numbers. I will report back if I can somehow prove or dis-prove my theory!.


Cheers

Hutch