Gearbox whine

[cbranni]

Hi All
I have have finally put some miles on my 1930 T6, I have got the engine starting very easily hot or cold and the brakes are working but still work in progress, it handles really well and performs perfectly .............except for the gearbox whine in first, second and third, it's awful and third is the worst almost like a police siren, don't laugh, it is such a relief when you change into fourth and the scream vanishes.

 I have read previous posts complaining of the same issue and Eddie's helpful answers.

At the moment I am avoiding third gear and going from second to top the engine has enough grunt and doesn't complain but over the coming winter I would like to sort it out.

When I bought the basket case there were two sets gearbox casings T/345 and 6Q/120 and one set of shafts and gears and I built up a decent box and to be honest it works well, gear changes are good up and down it is just the whine, I must admit I didn't check what pressure angle the gears were when I built the box.

Seems 14.5 was early 1900's and slowly changed to 20 mid century but not sure if Douglas followed suit

So the only option I have is to try and purchase a complete good gearbox or set of matching gears, if any members have any thoughts please reply, this whine is really spoiling a lovely rideable machine.

Thanks for reading, kind regards Colin

[Doug]

Colin,

I think the change from 14.5 to 20 degree pressure angle occurred earlier than mid-century. Regardless, Douglas did change from stub tooth form to involute for the 4-speed gearboxes in 1935. Some 1935 models had stub tooth and some involute according to the gearbox prefix code list. Even though the stub tooth is an involute curve, I presume it indicated a change in form. This all occurred a year or so before the Q/ and T/ prefix gearboxes, but it still is possible that you have a mix of early (1932-35) and late (1935-38) 4-speed gears of incomparable forms.

And yes, that will set up quite a whine. My brother had made a new engine pinion for a M120 Panther and had assumed one pressure angle but Panther had used the other. Even with a suitable amount of backlash, it whine something terrible until the pinion was remade with the correct pressure angle.

-Doug


[fix typo, 20Jan25, Doug]

[cbranni]

Thanks Doug for your prompt reply, my best course of action is to place a wanted advert on this forum and place an advert in the New Conrod probably for a complete gearbox or complete set of matching internals and go from there.

Once again thanks Doug, kind regards Colin

[cbranni]

Just an update on my noisy box issue, I failed to find another gearbox so I pulled the gearbox out stripped it and rebuilt  a few times and could find nothing wrong so I put it back in and today as the farm lane I live on was quite dry I took the bike out for a run around the village and the noise is far less of a screeching sound than before it is a whine yes and maybe a louder than other bikes I have but I can live with it and I also know there is nothing untoward going on in the box.

Next job before Spring is the very poor front brake, I understand that old bikes have poor brakes but this brake is dangerous and so far I have re lined the band that didn't work that well even after filing the high spots  I then replaced the band with a pair of shoes with same result, I could see the drum was flexing when applying the brake with both set ups so I welded a ring outside the drum, please see photo and it still flexed so it's back to the drawing board and hopefully come up with a solution in time for Spring.

Kind regards to all

Colin

[Alan]

Welcome to the strange world of Duggie brakes and as I think Doug said some years ago...they either work or no matter what you do they don't ! Use the search function as lots of chat re this...Every ride on my B29 aged me 10 yrs.
My solution was to use the shoes and parts etc from a Triumph sls drum..an amazing improvement...not original but so what !!! At least I could ride in modern traffic without certain parts of my anatomy going rigid every time a P plate SUV cut in front of me...

[cbranni]

Hello Alan

Thanks for the reply, I have tried a pair of Triumph shoes without a lot of improvement but I will revisit the setup again and persevere with it because it makes sense and I agree with you brakes are more important than originality, updates will follow

Regards Colin

[eddie]

About 18 years ago, I got persuaded to have a go at Vintage sprinting with a 600 DT based Douglas. Even though I had heard the stories of Douglas servo brakes not being very effective, I went ahead and used them. Bearing those stories in mind, I rebuilt the brakes using linings obtained from Friction Services at Keynsham, Bristol - the material they supplied was known as 'MZ Gold' - asbestos free and woven like the old Ferodo linings. I drilled and riveted the linings myself, but before doing the actual riveting, I roughened up the brake band and applied a liberal coating of Araldite (proper 24 hour Araldite, not the rapid rubbish!), and then did the riveting. The brake band was then fitted in the drum and the brake applied. The assembly was then left the requisite 24 hours for the Araldite to cure - the thinking being this would eliminate any sponginess in the brakes. The outcome was a success - after a couple of bedding in runs, the brakes worked well bringing the bike down from 100+mph without giving any cause for concern.

Regards,  
              Eddie.

[cbranni]

Thank you Eddie this does give me confidence to move forward.

Colin

[richard s1]

Regarding brakes
      About 40 years ago Frank Dolman sent me this letter (3 pages) on how to improve braking on the T6 that I had at the time.
    No doubt then, BSA brakes were easier to find than now.   

Richard Matthews 

[cbranni]

Hi Richard

Thanks for posting this I have printed them out so shall read and digest.

Kind regards Colin