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61
Douglas Motorcycles - General Discussion / Re: Four speed Aero gearbox
« Last post by FN on 23 Jan 2021 at 17:17  »
Inspection is not over now. What I found is, that the low gear pinion had a little bit more play than I would do it. The condition was not serious. The forks showed fresh surfaces especially in the regions, where the teeth could rub. All teeth showed rough surfaces. Sharp edges were present. I looked at the pinions.One had the DK mark on it in combination with D5. The other pinions got stamped with D5 also but not DK visible to me. The astonishing thing is, that bike got low milage after replacing many nuts and bolts. During that restoration the box was opened and sealed afterwars with plastic seal known from other components. If the flash was received over long time, it would have rubbed the forks completely down. I will continue my inspection. Below is the 4 speed spare parts list and I was checking for missing parts.
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Douglas Motorcycles - General Discussion / Re: Four speed Aero gearbox
« Last post by FN on 23 Jan 2021 at 16:53  »
Direct gear is reached by shifting the third gear pinions upwards and removing it from the dog clutch on the layshaft. A dogclutch between third gear pinion and sleeve gear is formed. In my chase the plunger was shifted totally into the gearbox cover, gap zero.
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Douglas Motorcycles - General Discussion / Re: Four speed Aero gearbox
« Last post by FN on 23 Jan 2021 at 16:46  »
Third gear: The lower pinion pair becomes unlocked and the upper ones receive connection.
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Douglas Motorcycles - General Discussion / Re: Four speed Aero gearbox
« Last post by FN on 23 Jan 2021 at 16:43  »
Now second gear: Here the layshaft gives the dog clutch.
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Douglas Motorcycles - General Discussion / Re: Four speed Aero gearbox
« Last post by FN on 23 Jan 2021 at 16:41  »
I did not know the action of the different pinions. The picture below shows the low gear position, the moment flow and length of the actuation plunger. The low gear pinion runs on the mainshaft on a bronce bearing, like in the three speed gearbox. In low gear position it becomes coupled to the mainshaft by a dog clutch from the second gear pinion.
66
Douglas Motorcycles - General Discussion / Four speed Aero gearbox
« Last post by FN on 23 Jan 2021 at 16:32  »
Dear Douglas friends,
I got so much information from this site, that I want to put something by myself into it. I am Gerd from Hamburg and Corona gives me time to work on a Douglas Aero 500 (1936), gearbox 6Q202. Here I want to show the results on an inspection of a four speed gearbox with constant mesh kickstarter. The gearbox worked without mistake. But I found lots of oil inside of the rear mudguard. The outside was clean. I thought, may be the gearbox has lost its oil and became dry now. I checked the oil level by unscrewing the screw to the rear cylinder head (not easy). Lots of oil (grease) was present. Therefore the oil level was ok but the oil showed yellowish flitter in it. I wanted to find the reason for the particels. I had no knowledge on the functions of this four speed gearbox. But I remember my mistake on the bearing bush for the low speed pinion on a three speed gearbox. It gave a full stop during riding (unfortunately to my daughter). This mistake don't want to do again. Removing from the frame and opening was quite straight forward. The picture shows the pinions and the gearbox cover.
67
Douglas Motorcycles - General Discussion / Re: Douglas Aero 1937
« Last post by FN on 23 Jan 2021 at 16:00  »
Doug,
thanks for the information. One night I thought the heavy load from kicking should not be put on a thread. I will redo the tool and do a next try. The holes in the ratchet are so demaged, that I believe my preowners did not succeed.
Gerd
68
Douglas Motorcycles - General Discussion / Re: Douglas Aero 1937
« Last post by Doug on 22 Jan 2021 at 19:23  »
Gerd,

Yes, it is threaded on. The three holes are factory, and the means for installation and removal. It helps a lot to have the face of the pin driver cut back to match the face of the ratchet closely. This reduces the cantilever of the pins. It is surprising that the small amount of deflection bridging the gap significantly diminishes the effectiveness of the impact driver in jarring it loose.

Remember it has had years of heavy boots stomping on it to tighten the thread!

-Doug
69
Douglas Motorcycles - General Discussion / Re: Douglas Aero 1937
« Last post by FN on 22 Jan 2021 at 18:54  »
I have a simple question on the four speed gearbox. This one has a constant mesh kickstarter. The ratchet is fixed to the main shaft and receives the full torque from the kickstart lever. Is the ratchet screwed to the mainshaft?
It looks like for me.  But I was not able to unlock it for getting the main shaft out of the box. There were three holes in the ratchet, which I used (are those original?). The small tool  (picture) was put on an impact driver. The ratchet was heated until oil was flowing out of the crevice and then the impact driver put on. It did not work. Has somebody a better method?
Regards
Gerd
70
Douglas Motorcycles - General Discussion / Re: Douglas Aero 1937
« Last post by Doug on 22 Jan 2021 at 18:49  »
Gerd,

There was a 4-1/4 page write-up in the Jan/Feb 2021 issue of the New ConRod magazine on the evolutionary changes of the 1936-38 Aero Douglas heavyweight models. I will be re-printing that here once I gather some additional supporting photos.

-Doug
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