Author Topic: Douglas Aero 1937  (Read 3426 times)

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Offline Doug

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Re: Douglas Aero 1937
« Reply #50 on: 28 Feb 2017 at 19:15 »
Eric,

With the output sprocket off, there will be a small amount of axial (end) play in the output shaft. With the sprocket on, the spring washer against the seal should eliminate any axial play. There should be very little radial play, or wobble. However the roller bearings are not spaced very far apart and much of the alignment is provided by the fit of the input shaft through the sleeve gear busing. If that is worn, the sleeve gear can wobble on the shaft and the roller bearings do not have a wide enough 'stance' to prevent it. The input shaft should have a small amount of axial play at all times and no perceptible radial play. Again, if the sleeve in the output shaft is worn, you will be able to wiggle the shaft up and down. If you can perceive it (0.15mm) it is worn out.

Yes, there is a rod that passes through the footrests with nuts on the outside clamping everything together. It looks like the face of the footrest and the sleeve have been modified. These should have a face serration to allow angular adjustment. Pictures of mine attached. The serrations for the brake pedal side are almost entirely worn down. I made new ones. I re-cut the serrations on the foot peg arms.





-Doug

Offline Doug

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Re: Douglas Aero 1937
« Reply #51 on: 28 Feb 2017 at 19:18 »
Actually, you may want to ask around about the footrest serration. Perhaps Douglas changed that for the 1937-38 models, because the serrations getting worn and mashed was a chronic problem.   -Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #52 on: 28 Feb 2017 at 20:38 »
As for the foot rests, I can see remains of serrations but INSIDE of the right only foot rest. Like if the rod should have matching serrations.
Nothing can be seen on the left.

Any way I will mount it back the way it was. I have more than I can handle for now.

Offline Eric S

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Re: Douglas Aero 1937
« Reply #53 on: 28 Feb 2017 at 20:53 »
I do have a small amount of axial play on the output shaft. (Providing output shaft is where the Sprocket for Primary Drive mounts or larger shaft)
However I have no "spring washer against the seal". Do you have a picture of that?

Providing input shaft is where the Sprocket for Secondary drive  mounts, or small inside shaft, I have no perceptible play between it and the output shaft.
I am not sure to understand what is the "sleeve in the output shaft" though.

Offline Eric S

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Re: Douglas Aero 1937
« Reply #54 on: 28 Feb 2017 at 21:07 »
I am not able to identify the thread size of the screws holding the front brake.
I thought it would be 1/4 26 Tpi BSC but is seems to be just a little bit asmaller and 1/4-26 do not screw there.

The original screws on the bike were Allen socket head screws. Anyone has the information as to the correct head shape on those screws?

Also how can we remove this triangular shape plate. Seems to be locked on the square shaft. Do I have to remove the front wheel?
« Last Edit: 28 Feb 2017 at 21:20 by Eric S »

Offline Doug

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Re: Douglas Aero 1937
« Reply #55 on: 28 Feb 2017 at 22:08 »
Eric,

The original fasteners would be hex head, Whitworth wrench size across the flats. While Allen head socket cap screws were available for the 1920s onward, Douglas did not use them until postwar.

The triangular plate is some sort of modification. So no telling how it was put together. Attached is the very original (and rusty) front end of my 1936 Aero. Also a picture of just the brake backing plate (sorry about the low resolution). The brake arm passes through a bush in the girder fork blade and plugs into a spline inside the brake. A bolt through the center holds the brake arm and shaft from falling out.





Markup of the sleeve gear, labeling the parts. I do not happen to have a picture of the wave washer, but it is of the same design as waver washers still sold today.



-Doug


Offline Eric S

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Re: Douglas Aero 1937
« Reply #56 on: 01 Mar 2017 at 20:30 »
I just remind that the front brake has been changed by a previous owner. I guess they installed Triumph parts to make it more efficient.

As for the leather gland, is it something hidden inside?
I guess I still miss parts as I can't see how a wave washer stuck between the rotary sprocket and the fixed gear box would handle the friction. Don't I need a ball bearing or the like?
Also I have 3-4mm between the gear box wall and the sprocket. Isn't it too much for a wave washer?
« Last Edit: 02 Mar 2017 at 07:59 by Eric S »

Offline Eric S

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Re: Douglas Aero 1937
« Reply #57 on: 06 Mar 2017 at 12:43 »
Hello there
On the front brake, original screws seems to be 26 Tpi and about 1/4 but  I can not screw in a 1/4-26 screw. So what it might be?

Doug that is your "bolt through the center holds the brake arm and shaft from falling out".

Doug again, from what I understood on your previous drawing, I should have a leather gland, a backing washer and a spring or wave washer. If those are 3 loose parts that are taken between the gear box and the sprocket, I am lacking them.
Below is a picture of the shafts out of the gear box. I only have the Sprocket to install there.

I found a round gasket, that comes to be slightly compressed between the box and the sprocket. Is that a decent solution unless anyone can tell me where to get the right parts?

Current spark plugs are NGK BP7EVX. Those are completely worn out. Is this model OK? Bike Works well with it...

Offline cardan

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Re: Douglas Aero 1937
« Reply #58 on: 06 Mar 2017 at 21:06 »

Hi Eric,
It looks like someone has fitted a "modern" lipped seal to replace the original leather seal. Since it has been leaking, I guess you need to replace it. Try to find a replacement before you try to get this one out because the metal casing is often very thin and will probably be ruined if you take it out from the outside.
A gasket of any kind between the case and the sprocket will not work: it won't seal the shaft and it will probably spin with the sprocket and wear the aluminium case away.
Cheers
Leon

Offline Doug

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Re: Douglas Aero 1937
« Reply #59 on: 06 Mar 2017 at 21:23 »
Hello Eric,

Remember when I said "if they used the same design as the 3-speed". Well they did, and they did not. I pulled the sprocket off of my 1936 Aero gearbox and the seal is not the same as the 3-speed. The housing has no external access to the seal, as you can see in this picture. The aluminum comes right down to the journal diameter.



Which did not match you photo at all. So I looked at another gearbox, this for a 1932 Greyhound 4-speed. It has a design like the 3-speed and the section illustration that I previously posted.



Just to the rear of the keys you can see the spring washer. The spring washer and the backing washer behind it are shown below. The leather gland was missing.





With this style, the back of the sprocket has a more pronounced spigot that projects into the end recess of the gear case and bear against the spring.



The 1936 sprocket only has a slight hub. The 1936 gearbox for the Aero has a P prefix, the 1932 gearbox for the Greyhound has a GB prefix. It looks like you have this earlier style gearbox?

The spring has a cross-section of 0.062 thick by 0.093 radial, 1.531 outer diameter, and a free height of 0.200 (all dimensions in inches). The backing washer is formed by rolling a lip. The material is 0.036 thick with a inner flange rolled up to make a overall width of 0.088; the outer diameter is 1.739 and the inner diameter is 1.293 (inches). The lip faces outward, towards the spring.

-Doug

Offline Doug

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Re: Douglas Aero 1937
« Reply #60 on: 06 Mar 2017 at 21:27 »
Eric,

The bolt that secures the brake lever is 1/4-25, a Douglas proprietary thread. They also used 17/64-25 (like for the petrol tank mounting bolts), so you have to be careful.

Picture of the brake arm and bolt in this post:
http://www.douglasmotorcycles.net/index.php?topic=2440.msg8835#msg8835

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #61 on: 10 Mar 2017 at 20:45 »
Leon

thank you for your expertise.
The round gasket I'm talking about is a round rubber ring. Being compressed it should pressure the shaft out of the box and limit the leak. Being rubber it should be harmless and help for a while.
I'd prefer to have the box opened, the modified gasket inspected and replaced but can not find anybody locally that may do it. Though waiting replies.

Doug thanks one more time. Don't know what to do. Maybe as just said give this rubber ring a try.

As for the bolts, the "bolt through the center holds the brake arm and shaft from falling out" will be re-installed. I wanted to change as it is an Allen head but will leave it as it is a 1/4-25 and can't find a correct hex head bolt in that size.

I will helicoil the 3 screws on the triangular plate and makes them 1/4-26. The original bolts seems to be also 1/4-25.
Anyway since they were Allen and loctited over worn out threads, I had to discard them + I should be able to live with 1/4-26 there.

The drum being a Triumph, is it possible Triumph also used 1/4-25 there?

On the tank I had a missing bolt so got 4 new chromed 1/4-26 bolts and they screw in 4 turns before being hard to turn. Are they bottoming out or are they 17/64-25?

Offline Doug

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Re: Douglas Aero 1937
« Reply #62 on: 11 Mar 2017 at 03:42 »
Eric,

The petrol tank bolts are 17/64-25.

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #63 on: 11 Mar 2017 at 18:10 »
Doug

I measured the 1/4-25 bolts and they are .232"
Seems a bit small for 1/4"?

Offline cardan

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Re: Douglas Aero 1937
« Reply #64 on: 11 Mar 2017 at 21:08 »

Since they're Allen heads, they might be M6 (6mm x 1mm pitch - 0.236 - 25.4 tpi)!

Leon

Offline Eric S

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Re: Douglas Aero 1937
« Reply #65 on: 12 Mar 2017 at 20:26 »
Well done Leon, it's well a 6mm bolt.
This bike seems to be a sample of every thread size available in the world.

I re-installed the gear box, clutch flywheel, ...
With the knowledge I acquired through the forum and reading period manuals, I came up to the conclusion that my clutch problems might be linked to an overloaded clutch counter acting on the cam plate/cable action.
So I thought I would adjust the springs to a minimum.
But I think I have too strong springs in there.
Using 2 springs (instead of 6) and screwing in the adjustment nut just 1 turn, I have the plate out of its location but the clutch seems to function and I can turn the primary chain sprocket by hand without turning the engine (so Clutch is well off)
Screwing more prevent that and turning the sprocket turns the engine.
I did not started the engine yet and did not tried "live" but I am really wondering if the sprins are OK.

They are 40mm/1.57" and wire is 0.80"/2mm


Offline Eric S

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Re: Douglas Aero 1937
« Reply #66 on: 13 Mar 2017 at 22:54 »
Looks like the tank bolts has been helicoiled that would explain the 1/4-26 Tpi bolts fits.

I also noticed the engine bolts fits into inserts that I do not have on the gear box where bolt screw into aluminium. But the inserts are the correct thread size.

Offline Eric S

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Re: Douglas Aero 1937
« Reply #67 on: 15 Mar 2017 at 20:21 »
Does anybody have any idea regarding the clutch springs discussed just above?
Are they too strong?

Offline Doug

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Re: Douglas Aero 1937
« Reply #68 on: 15 Mar 2017 at 23:34 »
Eric,

I don't know that anyone bothers to measure them. New ones are available to LDMCC member via the spares department.

As for the engine and gearbox mount. The engine is supposed to have the steel inserts, the gearbox was tapped directly into the aluminum.

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #69 on: 16 Mar 2017 at 11:01 »
Thanks Doug
I will check with the club.

I noticed a play on the rear wheel sprocket. Do I have a torque converter here?

Offline Chris

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Re: Douglas Aero 1937
« Reply #70 on: 16 Mar 2017 at 11:03 »
HI Eric
   I have just measured six clutch springs purchased at different times over the years from LDMCC spares. No two are identical. These are a fairly fast moving item and have been purchased from different sources probably on the basis of samples supplied as patterns. The lengths vary between 35.68 and 37.35mm, appreciably shorter than your springs of 40mm. Diameter of coils vary between 12.64 and 13.19mm. The wire diameter also varies between 2.01 and 2.12mm. The subject of clutch springs has been discussed previously on the Forum as other members have experienced difficulty with clutch operation. From my experience with four different models with flywheel clutches none of them needed more than four springs to function well even including a 350cc CW with passenger sidecar.
Chris.

Offline Doug

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Re: Douglas Aero 1937
« Reply #71 on: 16 Mar 2017 at 15:10 »
Eric,

Quote
I noticed a play on the rear wheel sprocket. Do I have a torque converter here?

Do you mean a shock absorber or cush-drive? If so, no, the rear sprocket is supposed to be rigidly mounted to the rear brake drum/hub/wheel. Having said that, it is only pressed on to a knurled portion of the brake drum. There are several key/blocks that transmit the torque.

-Doug


Offline Eric S

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Re: Douglas Aero 1937
« Reply #72 on: 16 Mar 2017 at 17:08 »
I don't really know what I mean !
But shock absorber or cush-drive seems to be what I had in mind.

 A friend told me that if the large toothed wheel (with the chain on) moves on the drum where it is installed, then it might be a torque converter.

If it is supposed to be rigid, looks like a new field to play with...
« Last Edit: 16 Mar 2017 at 18:35 by Eric S »

 

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