Author Topic: Dismantling 1936 Aero 3-speed gearbox - advice appreciated  (Read 514 times)

0 Members and 1 Guest are viewing this topic.

Offline Tazmantic

  • Full Member
  • **
  • Join Date: Mar 2020
  • Posts: 46
  • Location: Oxford, UK
Hi I want to split the 3 speed box on my aero is that basically the same as this?





I've got the cover plate off and removed the kickstart, do I just need to remove the input sprocket from the other side and then pull it all out from the kickstart side? what about the change lever?

Thanks Neil

[Split topic and add images. 05Mar20, Doug, Site Moderator]
« Last Edit: 05 Mar 2020 at 17:17 by Doug »

Offline Doug

  • Administrator
  • ****
  • Join Date: Mar 2004
  • Posts: 3695
  • Location: Glen Mills, PA, USA
Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #1 on: 05 Mar 2020 at 17:16 »
Neil,

Yes and no! Not quite the same, but you can pull the entire cluster out the cover side once the sprockets are removed. Be prepared for the rollers on the sleeve gear to become dislodged. Hopefully the grease will keep them in their place. Yours should look like this:



The change lever remains in the gearbox. No need to remove it unless the bushings are worn. This is a 1928 gearbox, but almost identical to what you are dismantling. You do have to watch when sourcing spare gearboxes as there were different main shaft lengths for the lightweights and the big twins. Otherwise they shared a lot of parts in common.

-Doug
« Last Edit: 06 Mar 2020 at 20:51 by Doug »

Offline Tazmantic

  • Full Member
  • **
  • Join Date: Mar 2020
  • Posts: 46
  • Location: Oxford, UK
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #2 on: 05 Mar 2020 at 18:50 »
Can I remove the side without removing the sprockets? as I don't really want to remove the whole cluster just want to look inside as Im sure its empty and just want to asses the gears.

Thanks

Offline Doug

  • Administrator
  • ****
  • Join Date: Mar 2004
  • Posts: 3695
  • Location: Glen Mills, PA, USA
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #3 on: 05 Mar 2020 at 18:54 »
Neil,

Yes, the cover can pull off the ball bearing races. If I remember correctly you will need to remove the kick start ratchet nut. However the fit at the other end where the journals enter the bearings tends to be a bit looser so the whole cluster tends to pull out first. You can try warming the cover up to loosen the grip on the bearings. Don't misplace any shims that might be between the bearings and the cover.

-Doug

Offline Tazmantic

  • Full Member
  • **
  • Join Date: Mar 2020
  • Posts: 46
  • Location: Oxford, UK
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #4 on: 05 Mar 2020 at 18:59 »
Kick start removed, side plate removed and bolt with spring removed just looked like the gear left wouldn't fit through the plate? or is that just the bearing I can see...

Thanks

Offline Tazmantic

  • Full Member
  • **
  • Join Date: Mar 2020
  • Posts: 46
  • Location: Oxford, UK
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #5 on: 06 Mar 2020 at 19:06 »
Got it all out today and all gears look ok, did find the gear select arm was loose on the square shaft so will tighten that up in reassembly (presume it should be tight?) did leave output gear in place to start with but then noticed a tight spot so stripped that out too and ended up with lots of rollers  :o grease in box was very thick so all washed out ready to rebuild.

I've read the post saying about the oil/grease mix to put in the box so bought some general purpose bearing etc grease and I have some 80w90 gear oil that doesn't say its EP should these be ok.

Thanks

Offline Doug

  • Administrator
  • ****
  • Join Date: Mar 2004
  • Posts: 3695
  • Location: Glen Mills, PA, USA
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #6 on: 06 Mar 2020 at 20:57 »
Neil,

Also check the four standing keys (short spline) in the center of the layshaft. These act as the dog clutch for 2nd gear. When heavily worn (along with the spline through the gear) the gear can be prone to jumping out of engagement under load.

You can buy self-leveling grease, also labeled as thixotropic, but since you have the grease and heavy oil, you might as well mix your own. You want it to level out after one to two minutes at room temperature.

-Doug
« Last Edit: 08 Mar 2020 at 03:53 by Doug »

Offline Tazmantic

  • Full Member
  • **
  • Join Date: Mar 2020
  • Posts: 46
  • Location: Oxford, UK
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #7 on: 07 Mar 2020 at 19:01 »
Checked the dogs and they look ok, Started to rebuild and when I nipped up the nut on the output shaft sprocket  :roll:it all locked up...

Behind the gear am I right in thinking there should be a felt seal? as mine has an oil seal and its too thick and stopping the gear going on the taper properly gripping the seal and its spinning in the gearbox. :roll:

Offline Tazmantic

  • Full Member
  • **
  • Join Date: Mar 2020
  • Posts: 46
  • Location: Oxford, UK
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #8 on: 08 Mar 2020 at 10:52 »


You can buy self-leveling grease, also labeled as thixotropic, but since you have the grease and heavy oil, you might as well mix your own. You want it to level out after one to two minutes at room temperature.

-Doug

So don't know if Im just being silly but Im struggling with this easy task... I have no experience as what the grease/oil shoud be like as the box was filled with just grease it looked like,

so I've made a mix up but I'm struggling with the test. The mix I have is pourable so is that too thin? if I drag my finger through the surface while its in an old plastic tub (about 1.5" deep) finger drag levels almost instantly, but if I tip the pot then level it out the grease takes ages to level out, If I pour it into a coffee jar lid so its about 1/4 thick it starts to level almost instantly but never looses the finger mark completely.

Confused dot com  :shock:

Offline Doug

  • Administrator
  • ****
  • Join Date: Mar 2004
  • Posts: 3695
  • Location: Glen Mills, PA, USA
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #9 on: 09 Mar 2020 at 15:06 »
Neil,

Sorry, I should have clarified but the topic of transmission lube has been covered before and I forget that not everyone has seen the old posts. The method is to drag you finger through it to make a groove and see how long it take to fill in. Don't worry about it filling in perfectly without a trace.

The danger of getting it wrong is thus: Too thick, the gears cut slots through the grease and push it all aside and it never flows back in to lubricate the gears (or not fast enough). Worse, it never gets in to lubricate the main shaft where it runs through the sleeve gear. Too thin, it leaks through the sleeve gear where the main shaft passes through. However it is a British motorcycle and it is expected to leak oil...

-Doug

Offline Tazmantic

  • Full Member
  • **
  • Join Date: Mar 2020
  • Posts: 46
  • Location: Oxford, UK
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #10 on: 09 Mar 2020 at 20:38 »
Cheers Doug,

Sorry I did search it and found some info on the 1937 areo but that was all, Does it matter how deep the mix is in the pot when you test it? because that's where I get my discrepancy from if its shallow it takes a while to level out but if its deep it levels out almost instantly.

Also referring to the 1937 aero topic I presume the seal on the output shaft should be leather with a cupped washer and a spring washer NOT an oil seal.

Thanks Neil


Offline Doug

  • Administrator
  • ****
  • Join Date: Mar 2004
  • Posts: 3695
  • Location: Glen Mills, PA, USA
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #11 on: 09 Mar 2020 at 21:50 »
Neil,

It is a leather conical washer. Against that presses a flanged steel washer, note in the illustration the flange faces out. Between that and the sprocket is a wave washer, that provides modest pressure. In this regard it is the same as the later Aero gearboxes. Douglas did not use proper oil seals until after WW2.





I never experimented as to the depth and I don't see why it would matter unless the goo was not thoroughly mixed and homogeneous.  That is, lower viscosity layer in a large area container would make for a thinner strata that would not fill in the 'groove' fully. I have always used a throw-away plastic drinking cup to make up my mix.

-Doug




Offline Tazmantic

  • Full Member
  • **
  • Join Date: Mar 2020
  • Posts: 46
  • Location: Oxford, UK
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #12 on: 09 Mar 2020 at 22:08 »
Doug,

Thanks so much for the diagram do you know if these parts are available? and thanks again for the info on the lube I'm thinking I really need to see some and experience the correct viscosity for myself  :?

Neil

Offline Tazmantic

  • Full Member
  • **
  • Join Date: Mar 2020
  • Posts: 46
  • Location: Oxford, UK
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #13 on: 10 Mar 2020 at 20:36 »
Neil,

It is a leather conical washer. Against that presses a flanged steel washer, note in the illustration the flange faces out. Between that and the sprocket is a wave washer, that provides modest pressure. In this regard it is the same as the later Aero gearboxes. Douglas did not use proper oil seals until after WW2.







-Doug

Does anyone know if these parts are available? were they fitted to other gearboxes as I've contacted LDMCC spares and they don't keep them..

Cheers

Offline Tazmantic

  • Full Member
  • **
  • Join Date: Mar 2020
  • Posts: 46
  • Location: Oxford, UK
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #14 on: 16 Mar 2020 at 20:13 »
So now ive had it out on the road a few times Im finding its crunching when going into 1st, the clutch is disengaging ok because with the engine stopped I can spin the primary gear really easily so just presume when the engine is running its the tiny bit of friction in the clutch that's spinning the primary chain, so this makes me think could my oil/grease mix be too thin thus not putting enough friction on the gears in the gearbox to stop the primary...

Any help  :?

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 263
  • Location: France
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #15 on: 16 Mar 2020 at 22:33 »
I had something similar. Ended that the crankshaft's cone's surface where the flywheel slides on was quite poor and I had the bolt holding together the various parts of the crankshaft un-locked. I noticed it when I grabed the protruding shaft of the crankshaft (the cone) and felt side play.

Offline Doug

  • Administrator
  • ****
  • Join Date: Mar 2004
  • Posts: 3695
  • Location: Glen Mills, PA, USA
Re: Dismantling 1936 Aero 3-speed gearbox - advice appreciated
« Reply #16 on: 17 Mar 2020 at 04:27 »
The Douglas flywheel clutch is prone to drag. Play in the clutch disk carrier bearing and where the pressure plate sleeve rides on the flywheel hub allows both to tip their separate ways under the chain load and uneven clutch spring pressures. And there is not a lot of room inside to spare. There are ways to recondition the fit between the pressure plate and the flywheel hub, by making the hub bigger. And that is often where the majority of the slop is, as I don't think Douglas made the fit very tight at the time. The roller bearings are a different matter, unless you have some over sizes rollers.

What is often do is to replace the clutch thrust ball bearing with an oil impregnated bronze washer. This side-steps condition issues of worn or pitted bearing races and provides a little extra friction that acts as a clutch brake, acting against the clutch drag.

-Doug

 

motorcycle