Author Topic: Douglas Aero 1937  (Read 23560 times)

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Offline Eric S

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Re: Douglas Aero 1937
« Reply #150 on: 07 Aug 2018 at 20:01 »
In any case the drawing comes from Douglas owner's manual.
Should you use a smaller diameter #5 bearing then you would push #13 but clutch plate #6 would not be pushed then and remain engaged.

Offline eddie

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Re: Douglas Aero 1937
« Reply #151 on: 07 Aug 2018 at 21:11 »
No, Eric, exactly the opposite. The drive is obtained by having the springs pushing against the flange of the carrier sleeve which, in turn, pushes via the set of balls and applies pressure to the clutch plate, forcing it against the pressure plate. If the release bearing pushes against the end of the carrier sleeve, the sleeve will be lifted, releasing the pressure and the clutch plate will drift free of the pressure plate.
   In your illustration, the release bearing bears against the face of the sprocket, so when the clutch is lifted, the full spring pressure is being taken by the thrust bearing between the clutch plate and carrier sleeve - this will provide enough drive to make gear engagement almost impossible. You can easily check this out by removing the flywheel and taking away the clutch release - lightly refit the flywheel and just 2 clutch springs. Use a pair of tyre levers to lift the carrier sleeve and see if the clutch plate/sprocket can be turned freely. (don't lift the carrier sleeve too much or you may dislodge some of the balls in the thrust race).

  Eddie.

Offline Doug

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Re: Douglas Aero 1937
« Reply #152 on: 07 Aug 2018 at 21:43 »
Eddie,

The sprocket and clutch disk are effectively 'pinched' between the release thrust bearing [5] and the other thrust bearing under the clutch disk [8]. The idea being they are enough of an anti-friction bearing that the clutch disk can rotate freely; even under the pressure of the clutch springs. In reality, there is probably enough bearing drag that the sprocket would never entirely become stationary of its own accord. However the friction of the primary chain and the gearbox ought to counteract that and be sufficient. In theory...

There is a problem with pushing directly on the end of the carrier sleeve [13]. While this will unload the pressure of the clutch springs against the clutch disk, it does not physically push the clutch disk away from the backing plate. You would have to wait for the clutch disk to shuffle away and cease contact, in its own good time. It might just continue to drag against the face of the backing plate. Also, you would be separating the ball races for the thrust bearing [8] - perhaps by as much as the clutch lift - until such time the liberated clutch disk wandered over and closed up the gap. If I remember correctly, the races are like the old bicycle bearing type, or like the 2-3/4hp wheel hubs. There is a bit of a taper leading into the curve of the ball track. So as it separated, it would develop radial clearance. That would allow the clutch disk to hop about off center, with only the bearing rollers biased over towards the sprocket to counteract it. So I think the intention was to keep the balls of the thrust bearing [8] at all time in contact with their race.

I have ridden an Aero and an S6 with these single sided cork clutches, and they are capable of working just fine. But it is like the Douglas internal band brake, it only takes a few non-obvious things to turn them into an infernal PITA.

-Doug

Offline eddie

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Re: Douglas Aero 1937
« Reply #153 on: 08 Aug 2018 at 06:23 »
Doug & Eric,
         As I said previously, "Now if the carrier sleeve was shortened to be just proud of the face of the sprocket" - I was thinking about 10 thou proud - that would mean the release bearing would lift the carrier sleeve just 10 thou, thus reducing the drag by unloading the bearing[8] before lifting the clutch plate away from the pressure plate. Set up that way, the bearing[8] would have a much easier life as it would only be performing under a lesser load when the clutch is half engaged - with the clutch disengaged, it would be running with the 10 thou clearance, and fully engaged it would be under load but effectively 'static'.

  Regards,
               Eddie.
« Last Edit: 08 Aug 2018 at 07:47 by eddie »

Offline Doug

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Re: Douglas Aero 1937
« Reply #154 on: 08 Aug 2018 at 14:33 »
Eric,

Ah, I forgot to factor in that ten thou clearance. That would stop the bearing from separating. The race of the thrust bearing would then have to handle the differential between the speed of the carrier sleeve and the clutch disk, but the clutch disk would be unloaded from end pressure by then and the parts would be greasy. The gap would close as the clutch wore and it would gradually return to the factory design.

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #155 on: 08 Aug 2018 at 16:01 »
Hi everybody
Stupid here

So, as 13 and 6 were moving together no matter what and the fact that the slightest pressure from the springs was locking the sprocket, I thought that a gremlin was hiding in the #8 balls or #7 rollers.
I took off the whole thing, removed the balls and saw nothing wrong.
Counted the rollers and I had 30 on the lower row and 32 on the upper (keep in mind they are larger 5mm rollers). I was positive that I counted them 3x when installing and had the same amount of rollers on both rows.
So checked in the greasy balls, not there. Mystery.
Put 2 more rollers on the lower raw, slide the 2 parts together.
Then had one more rapid look at the balls and then I saw guess what, 1 roller in the balls. And then another one. My 2 MIA rollers were back !
A 2 years old monkey knows that a square do not fit in a circle and square rollers are probably not doing any good in round rollers.

So now I just have to slide the balls in place; Only concern is that I have 32 ORIGINAL balls. There is enough place for one more ball that I don't have; Can I roll with 1 missing?


Doug your point is mechanicaly sound (I guess) but as  the parts I am using seems to be originals, I will rely upon Mr Douglas assumptions that it should work as it is.
I will keep that in mind however should I have to work on that later.
« Last Edit: 08 Aug 2018 at 16:57 by Eric S »

Offline eddie

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Re: Douglas Aero 1937
« Reply #156 on: 08 Aug 2018 at 17:14 »
Eric,
        Don't fit the extra ball - the general rule for crowded balls or rollers is to fit a full house minus one, so that adjacent balls/rollers are not pressed together.

Doug,
          Clutch wear will not affect the suggested 10 thou clearance as the carrier sleeve and clutch plate will move as a pair - only wear to thrust bearing [8] will affect that clearance.

  Regards,
               Eddie.

Offline Eric S

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Re: Douglas Aero 1937
« Reply #157 on: 08 Aug 2018 at 17:46 »
Thank you Eddie
In the meantime I reinstalled the whole set-up as anyway I don't had an extra ball.

It works much better.
Originally when on the stand at neutral the rear wheel was slightly turning.
Engaging a gear was cracking.

Now, rear wheel barely moves at neutral on the stand. However engaging gear still cracks. When clutch is released, the primary chain still turns as you expected. Will adjust  the clutch as Doug said and give her a few kilometers to see how it settles...
I don't know if the pressure on the spring is paramount here.
« Last Edit: 08 Aug 2018 at 17:54 by Eric S »

Offline Doug

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Re: Douglas Aero 1937
« Reply #158 on: 08 Aug 2018 at 19:20 »
Eddie,

Correct again. My brain seems to be firing only on one cylinder today!

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #159 on: 26 Sep 2018 at 12:05 »
Hello dear all

I had not a chance to ride the Douglas until today. Clutch still cracks a lot to engage first gear but then during riding it goes through smoothly. I will try again and maybe there is some break-in taking place.
I would like to check the head nuts.
What is the torque on these?
And what torque on gear box and engine on frame?

Also what pressure do you put in your tires. I am using 3.5x19s.

Edit :
Just noticed what may be a problem
When pressing the clutch lever I noticed that the flywheel moves.
I measured it at +.020" at 12o'clock and +0.00 at 6
Then I moved it by hand and I can definitively feel a play in the crankshaft. When moving by hand the flywheel, measured at 9 o'clock , I can get as much as .040" of play.
Is that normal or too much?
« Last Edit: 26 Sep 2018 at 18:25 by Eric S »

Offline Eric S

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Re: Douglas Aero 1937
« Reply #160 on: 27 Sep 2018 at 07:36 »
Hello

Sorry if I appear like impatient but I plan to attend the Distinguished Gentleman Ride next sunday with 100-150 kms to do but I would like to make sure I can make it so any comment or advice about my previous questions would be greatly appreciated.
« Last Edit: 27 Sep 2018 at 07:53 by Eric S »

Offline Doug

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Re: Douglas Aero 1937
« Reply #161 on: 27 Sep 2018 at 14:40 »
Eric,

Never seen any torque value published. Generally manufacturers didn't for stuff of the era. You were just expected to have a feel for the bigger the fastener the tighter you could wrench on it! Basically, what you can comfortably accomplish with open and box wrenches. No sockets with breaker bars; no one had them back then.

When you say flywheel movement or play in the crankshaft, do you mean the flywheel moves relative to the crankshaft or the crankshaft moves relative to the crankcase? Either way, the numbers you mention are grounds for 'do not operate until further investigation'. The flywheel has to be rigid on the taper or the taper will be destroyed. Either axial or radial clearance on the drive side bearing is a major problem. Axial is very serious (could be the incorrectly shimmed for end play) and radial is courting a catastrophic failure. End play should be a slight 0.005-0.010" or so; in other word you should not be able to perceive it. There should be no measurable radial play.

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #162 on: 27 Sep 2018 at 15:01 »
Thank you Doug

Re. Torque, I tend to over tighten the bolts and nuts usually so I was just asking...

I will take down the flywheel this evening to check the play on the crankshaft and make sure from where this play comes.
I did not checked but I did not felt any axial play, only radial (from side to side)

Will come about it later.

Offline Eric S

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Re: Douglas Aero 1937
« Reply #163 on: 27 Sep 2018 at 19:05 »
Well I have .030" of fore and art (axial) play
.020" side to side
Not very accurate measures taken on the crankshaft top, flywheel removed.
Noticed the shaft seems to be worst than what I remember. Should not induce play but would not help otherwise.
« Last Edit: 19 Oct 2018 at 06:24 by Eric S »

Offline eddie

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Re: Douglas Aero 1937
« Reply #164 on: 27 Sep 2018 at 21:36 »
Eric,
       To be brutally honest, with a crankshaft taper that bad, I wouldn't attempt to ride the bike anywhere! No matter how tight you get the crankshaft nut, the flywheel will work loose and do even more damage! As it is, the flywheel will not run true, so the clutch will not free properly. With the amount of play you have on the crankshaft, the whole engine needs stripping and rebuilding.
Sorry to be the bearer of bad news, but running the engine will only make matters worse.

    Eddie.

Offline Eric S

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Re: Douglas Aero 1937
« Reply #165 on: 28 Sep 2018 at 06:43 »
Eddie

I was ready to hear that.
I will take off the engine (and gear box as the quick tends to rattle, probably some teeths missing inside) so will hurry my winter project.
Any adress where I might go for the rebuild?
Or anybody can guide me in that?
I remember that the crankshaft has been worked on from the documents I had with the bike.

Offline Eric S

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Re: Douglas Aero 1937
« Reply #166 on: 04 Oct 2018 at 08:19 »
When we'll machine the cone on the crankshaft and in the flywheel, how do we make the parts fit together again.
Is it just a matter of taking the flywheel down the cone a bit more or do we need to sleeve the flywheel?

Offline eddie

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Re: Douglas Aero 1937
« Reply #167 on: 04 Oct 2018 at 09:57 »
Eric,
        From the photos you have posted and the figures you have quoted for crankshaft movement, your engine needs a complete strip down to check where the problems lie.
        From the basic questions you are asking, I get the impression that you don't have the necessary expertise to do the work yourself, so I would advise you to put the work out to someone who specialises in engine rebuilds.
       To bring the engine back to original spec, the flywheel taper and crankshaft taper (and possibly bearing journal) will need building up and re-machining - otherwise the flywheel will go on too far (maybe by 12mm!).
       From the photo of the crankshaft taper, I would guess that someone has already made a half-hearted attempt at a repair - and in actual fact, made the problem worse, because the poor fitting flywheel has broken loose and done considerable damage to the taper. Unless you are a skilled machinist and capable of carrying out precision engineering, do not attempt to repair it yourself!!

     Regards,
                   Eddie.

Offline Eric S

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Re: Douglas Aero 1937
« Reply #168 on: 04 Oct 2018 at 11:58 »
I feel pretty confident that I can do it myself. I bought a brand new file and I don't see too much trouble in doing that while watching TV.

No, seriously, of course I will not attend to make it myself and I think I can find a local company that will make the hard work.
I guess I can diassemble the engine and maybe put it back together should I do not find an expert that can do it.
I did not knew material can be built-up.
I just hope I won't find parts in need to replacement that need to be built from billet.

You are again right about the work previously done. I will check from home tonight but I remember having seen an Invoice in the file that was crankshaft related...

Offline Jonathan Hewitt

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Re: Douglas Aero 1937
« Reply #169 on: 04 Oct 2018 at 17:15 »
Best laugh I have had today ,nice one Eric even with that problem.
Jonathan

Offline Eric S

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Re: Douglas Aero 1937
« Reply #170 on: 04 Oct 2018 at 21:28 »
The engine is now ready to leave the frame.
Only concern is the magneto. Does it needs to be timed with the engine?
Do I have to make some marks to replace it correctly later?

I went through the documents I had with the bike and several pages concern researches the previous owner made (David, owned it from 2015 to 2016)
He was on this forum and printed messages Eddie and Doug sent him.
Apparently he had troubles already with it, had it modified and it has been modified already prior to his ownership.
The previous modification was made in UK for a french owner but no name on the letter, only 2 pages of drawings and this letter.

Will try to sort this out over the week-end.

Offline Eric S

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Re: Douglas Aero 1937
« Reply #171 on: 08 Oct 2018 at 16:07 »
Well I have sorted out all the documentations that came with the bike.
However some documents are not dated so I am not sure at what time the crankshaft has been worked on and if several modifications has been made or if it was just discussions.

Anyway I will have to remove and open the engine. So this takes me back to my previous question about Magneto. What is the trick to remove it without loosing the timing or if it is just a matter of re-timing (with professionnal help) upon re-assembling...
« Last Edit: 08 Oct 2018 at 18:38 by Eric S »

Offline Doug

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Re: Douglas Aero 1937
« Reply #172 on: 08 Oct 2018 at 16:35 »
Eric,

There is no way to practically preserve the timing unless you want to do paint dots on the gears or scratch marks. It is just simpler to re-time it when it gets put back together. Given the other issues that have arisen, I would assume the timing needs verifying anyway, so might as well go through the procedure yourself and know it is set correctly. There might well be marks by the teeth for the valve timing already, though unlikely for the mag. But it is not that complicated to time, so I wouldn't worry about making any special marks.

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #173 on: 12 Oct 2018 at 17:03 »
Engine is now on my bench.
Anybody can take me on a step by step process to reach the crankshaft please?
Is there and caution To have when disassembling like on the valves?

Offline Eric S

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Re: Douglas Aero 1937
« Reply #174 on: 13 Oct 2018 at 18:21 »
Thanks To the manual I managed to remove 1 cylinder. To get the second one I need an imperial Allen wrench which I did not have here.
I noticed some extra grease near 1 valve?
The brass part near the oil pump is not nice but seems to work.
Piston is scratched but cylinder is nice and rings has been replaced by previous owner.
Now the manuel do not enter further disassembling so I will need help from now.

Offline Doug

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Re: Douglas Aero 1937
« Reply #175 on: 14 Oct 2018 at 02:23 »
Eric,

Don't know what the grease is about. The tappet chest should be lubricated by oil mist.

Splitting the cases is pretty straight forward. The only thing that needs special mention is to remove the timing pinion before tapping the crankshaft through. It can be a tight fit on the crank and difficult to get behind it to extract. You might need a special gear puller. The crankcase wall is very thin behind it, so you don't want to be prying against it, or using it to strip the gear off the journal. I cannot remember if the key for the pinion will clear the hole through the crankcase wall, so you will need to check that and extract the key, if required. The ball bearings should be just a light tap (with a rawhide mallet) fit in the crankcases. If stuck, a little heat around the bearing bosses should free it up. If the crankshaft slips out of the ball bearings, leaving the bearings in the crankcase, then just leave them there. Unless the bearings need replacing. On the drive side, there should be a bearing slinger between the crankshaft and the bearing. Between the bearing and the crankcase there may be one or more thin shims that set the end float. Again, it depends if the crank slips out of the bearings, or the bearings slip out of the crankcase.

I seem to recall form older posts for this machine that the oil pump drive is slightly different for the 1937-38 machines, vs. my 1936 Aero. For 1936, the worm has a bronze bush and spins on a steel post that is pressed into the timing cover. For 1937-38, the arrangement was the worm was on an axle, and the bush was in the timing cover. Though I am not sure why the bore is offset so much from the original hole in the timing cover. maybe they needed to alter the location, and that was the easiest way to do it.

Cylinder wall oiling is basically the spray tree from the oil pump dribbling oil in the path of the conrods. This is supposed to line up with shallow grooves in the center web that lead the oil in at the sides of the conrods and so to the big end bearings. See arrow in following image:



What misses the grooves get splattered about by the crankshaft and thrown on the cylinder walls. So you will want to verify the spray tree is delivering oil, and that the holes are approximately lined up with the grooves in the center web. Because it looks like there is a problem with the pistons not getting enough oil.

-Doug
« Last Edit: 17 Oct 2018 at 22:33 by Doug »

Offline Eric S

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Re: Douglas Aero 1937
« Reply #176 on: 14 Oct 2018 at 12:26 »
Doug
since the picture I removed A Nut and B part. I guess the Timing Pinion is what I marked as C.

As for the Bearing Slinger and Shims. I don't saw any shim and I have only 1 washer marked E. No idea what is a slinger. SEE NEXT MESSAGE FOR MORE
As for the spray tree, it points above the conrods but I can not see for now where is the center web from your picture??
For now it looks like there is an anormal play at F. The nut might be not tight but I don't have the right wrench with me.
Bearing on Shaft exit seems OK.
Is it an original set up so far? (except oil pump arrangment)
Do you have any tip as how to test the spray tree?
« Last Edit: 14 Oct 2018 at 16:27 by Eric S »

Offline Eric S

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Re: Douglas Aero 1937
« Reply #177 on: 14 Oct 2018 at 16:40 »
OK I finally went the whole thing.
I did not find anything really wrong in the bearings, plays or whatever except the play on F described before.
Now I found a home made washer which I really do not like and the wall behind it is cracked and out of shape. (do not seems to be really flat)
I met a company in Birmingham last year that can repair this crack. At least I am going to ask him as the wall is only 3mm thick...
Unless it would be better to machine and put a steel insert?
The red arrow shows a slight mark that do not seem to be a crack.
Would you please confirm the valve cams are on the right position as I did not made marks on them and I need to make sure they do not rotated 180. I don't think so but want to make sure.

Any other comment is welcome.
« Last Edit: 14 Oct 2018 at 18:48 by Eric S »

Offline Doug

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Re: Douglas Aero 1937
« Reply #178 on: 14 Oct 2018 at 16:55 »
Eric,

Yes, "C" is the timing pinion. It will need to be withdrawn, and possibly its key, before removing the crankshaft from the crankcase/bearing. You will probably have to remove the cam spindle support plate "D" and the inlet and the cam wheels to get good access to the pinion. To get the cam wheels off, you will need to remove the tappets for the rear cylinder that are blocking the way.

There is a keeper plate bridging the two tappet guides, which is pretty obvious. The tappet guides are tapered on the outside and usually need a tap with an aluminum drift to pop them loose. The head of the tappet is too big to exit with the tappet guide, so the tappet guide is slid off the tappet. That means the valve adjusters have to be removed. Once the tappet guide is slid out, the tappet can be cocked at an angle and withdrawn to the inside. A bit of a nuisance, but it makes for a commendably compact arrangement.

"E: is the oil slinger i mentioned. It looks like it was in the correct position, between the crankshaft and the drive side ball bearing. The shims (if any) are behind the bearing; between it and the crankcase. They can stay there until you determine if the crankshaft end float needs adjustment.

"F". The connecting rods can have a little end play with out detriment. I don't know what the official amount would be, but in general 0.008 - 0.015 inch is often encountered for roller bearing connecting rods. I would err towards the loose side because the Douglas crankshaft does flex and you do not want the connecting rod getting pinched! This gap can be checked with a feeler gauge. The bolts that hold the whole the three parts of the crankshaft together should be very tight. You do not adjust the clearance by how much you tighten the bolt, the assembly had to be clamped up solidly and rigid. If not, the flex and motion across the connection will eventually work it loose and fracture the crankshaft.

You will want to check the connecting rod bearings while you are at this stage. They should rotate freely in either direction with no tight spots. Axial clearance as already noted. You should not be able to feel any perceptible radial play. This can be done by spanning you thumb across the connecting rod and crankshaft web and applying pressure and trying to feel any relative movement between the two. Don't take the crankshaft apart unless you have to, though it may be require to repair the crankshaft taper.

Spray tree/bar. It looks like the end of your pipe is open; it should not be. The end should be capped with weld and there will be two small holes pointing down at the crankshaft. It is a matter of checking to see if these holes line up with the grooves in the center web that led oil into the connecting rod bearing. A good time to check it is while the crankshaft is still in the crankcase and can be revolved while making observations. I don't think there is enough volume of oil that it jets out of the hole, so there is no point trying to test the system under pressure. It is more like a dribble in the path of the crankshaft. The spray bar is threaded into the pump body and locked by a jam nut. Axial adjustment is by threading it in or out of the pump body in increments of one revolution and locking it in place with the nut.



At some point, you will want to check that you oil pump is working. That can be done applying some oil to the inlet port and turning the pump over by hand. Oil should be transferred to the outlet. The oil circuit has been dealt with in other posts.




« Last Edit: 17 Oct 2018 at 22:33 by Doug »

Offline Eric S

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Re: Douglas Aero 1937
« Reply #179 on: 14 Oct 2018 at 18:47 »
Doug

I assume you replied "only" to the first part of my message.
The spray bar is well closed on the end.
The play at F is like if the large bolt is not tight enough.
I don't have any play at the conrods. Well not so much that I felt it but I have to remove the piston to feel it better.
The only "shim" I found is this homemade washer.

Offline Doug

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Re: Douglas Aero 1937
« Reply #180 on: 15 Oct 2018 at 04:04 »
Eric,

You posted another reply while I was typing the last message, so it did not address the latest developments.

If the bolt for the crankshaft were not done up very tight, or the joint not pulled up hard against the shoulder of the crank pin race, that would be extremely detrimental to the rigidity of the crankshaft.

Typically there should not be a washer behind the crankshaft pinion. Standard design practice would have this pull up directly against a shoulder on the main shaft. However... The spares list does state part number "18022, Washer behind pinion". So it looks like there is indeed supposed to be one there.

The inlet and exhaust cam are the same part number. So it does not matter which position you install it, or which side faces in; other than the generally good practice of returning everything to its original position because the parts have bedded in against each other.



The cracks at "A" are typically due to levering off the timing pinion by prying against the rear wall of the crankcase. Folk do not realize how thin it is. As long as there are no lose pieces, it is best left alone. Welding will likely make it much worse. Douglas aluminum (or alumininum) has a very poor reputation for welding and is to be avoided if at all possible. It is very porous, and well saturated in oil. This creates unending impurities when welding regardless of the skill of the welder or how modern their equipment. It is never pretty and often cracks alongside the weld. Plus, you have distortion issues caused by welding. All that is needed is enough of a lip to stop the ball bearing from pushing though into the timing chest. Indeed, part of the crankcase wall is already removed to allow oil to breath into the timing chest at the port "B". So these cracks are relatively harmless.

More worrisome is the crack at "C" as this ties the main bearing in to the rest of the crankcase. And I cannot see how it can be anything but a crack as it spans the machined and cast surfaces. It is peculiar, I have to admit, that it does not seem to penetrate through to the inside of the crankcase. The saving grace is that it is above the bearing and not directly in the load path between the bearing and the cylinders. Still, it is a damnable thing. Do you leave it and hope for the best, or gamble with welding and the problems associated with that?

You could bore it out and put in a steel sleeve. The following is just such a repair carried out on a 350cc crankcase.



In this case the entire wall was blown through because the timing pinion was not removed first before extracting the crankshaft. This repair does not really tie the bearing housing into the crankcase, but it does help distribute the load. The saving grace is it is only a 350cc, so the load is not as great. Mind you, the 600 Aero probably only makes 12-15hp.

-Doug


« Last Edit: 17 Oct 2018 at 22:34 by Doug »

Offline Eric S

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Re: Douglas Aero 1937
« Reply #181 on: 15 Oct 2018 at 10:29 »
Doug

I forgot a shim. I had well one bearing against the crankshaft larger diameter and the face of the bearing. Side opposite flywheel.

As for the inlet/exhasut cam. Depending how you rotate them, their face can be / or \ hence my question.

Re. the repair, Nicolas Hood makes repairs without welding. They have a special process with screwed in parts and remachining. www.castingrepairs.com
But as you said it does not need repair, I will leave it. I will wait Nicolas' reply though.

As for the crack on C, I checked it again and it is definitively not a crack. It is just a surface mark although I can't explain its origin.

I tried to tighten the large crankshaft nut. A socket won't fit so I have to use a flat wrench. However 28mm is too large (being 28,1mm) even if bolt is measured at 28mm and I don't want to force as it is likely to slip and damage the head which is already not nice.
What is the actual size of that bolt?
« Last Edit: 19 Oct 2018 at 06:49 by Eric S »

Offline Doug

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Re: Douglas Aero 1937
« Reply #182 on: 15 Oct 2018 at 13:25 »
Eric,

The following timing info is for the 600EW, but basically the same engine design as the 600 Aero.



I do not remember what the crank pin bolt size was. Most likely the hex is a Whitworth wrench size. The next size under 28mm is 9/16W, which has a maximum distance across the flats of 1.010 inch. 5/8W is 1.100 inch.

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #183 on: 15 Oct 2018 at 14:57 »
Doug

Can you educate me with 5/8W (it looks like it is not 5/8") that makes 1.100".
That is 27.94mm so it might well be the one.

Beside
I have hex nut bolts and Allen bolts on the cylinder heads. Which ones are correct, where to get them and what size are they?

Offline Doug

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Re: Douglas Aero 1937
« Reply #184 on: 15 Oct 2018 at 15:58 »
Eric,

Whitworth wrenches are a peculiar British institution. Not only did Whitworth pioneer a standard for thread sizes and pitch, but also a suitable size hex head for the bolt. I do not know how he came up with these 'optimum' sizes, as they are all odd sizes (not fractional or metric). This all back in the day of wrought iron and coarse threads. So a 5/8 Whitworth wrench would be suitable or a 5/8 bolt (or thread diameter), with the hex head of course being bigger than the bolt shank. Over time, bolts transitioned from iron to steel and material-wise were more homologous; also a fine thread series (BSF) was needed. So British Standards (BS) which took over for Whitworth (now relabeled BSW) reduced the hex height and increased the hex size. The modern, low profile hex head bolt. This lead to a disconnect between a Whitworth wrench, and the bolt head that it would fit. What was formerly a 5/8W wrench now became a 11/16BS wrench. You will find tables for the wrench sizes online.

I am not sure when internal hex head bolts (Allen cap screws) first came into use. Douglas did use them on the post war models, but you will not find any on the prewar bikes. The cylinder head bolts are 5/16-18 Whithworth thread. The dimension across the hex is 0.437 inch, or 7/16. Not a Whitworth wrench size. I don't know why they chose not to use a Whitworth size (0.445 inch).

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #185 on: 15 Oct 2018 at 19:01 »
When I started with the Douglas I had to learn the subtles of the British "Standards" and I even wrote a piece on a french forum on the subject but I never heard that Witworth also "standardised" Nuts dimensions !

Offline Eric S

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Re: Douglas Aero 1937
« Reply #186 on: 17 Oct 2018 at 19:15 »
I removed the pistons. Checked the play on the rods. Nothing wrong here.
I made my own 5/8W wrench and the flywheel side of the shaft can be tightened almost 1 full turn and I did not forced.
So I will have to find a way to make them tight and maybe Loctited?

On the center web, I have a small screw. What is it for?

Next step is to check for plays on the bearings and then go to a machine shop with flywheel and shaft for rebuilding of the cone connection.
I have 1 piston full of carbon on top and the other one only covered on a 1/3. Any meaning here?
I will re-do the paper gaskets. Previous mechanic that did them made a nice and tight fit around round parts (cylinder bases for instance). What is the trick to cut round holes in paper gasket, at the right place?

Pistons are scratched but the cylinders are nice. I guess they are ancient scratches but will check spray tree though.
« Last Edit: 19 Oct 2018 at 06:51 by Eric S »

Offline Eric S

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Re: Douglas Aero 1937
« Reply #187 on: 17 Oct 2018 at 19:26 »
While the engine is in parts I will make some paint.
Do I have the correct color scheme on the drive train?
Do I have correct gas and oil hoses?
What improvements would you recommend?
How would you "sand blast" the cylinders?
« Last Edit: 17 Oct 2018 at 22:49 by Eric S »

Offline Doug

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Re: Douglas Aero 1937
« Reply #188 on: 17 Oct 2018 at 22:58 »
Eric,

The slotted screw on the center web of the crankshaft is a plug for an oil gallery. The 1936 Aero engine was derived from the 1935 500cc "Blue Chief" 500cc Douglas. The Blue Chief had a drilled crankshaft and oil pressure feed to the end on the crankshaft on the timing side. I would appear you have a Blue Chief crankshaft in your Aero. If so, the crank does not have the shallow grooves leading to the connecting rod bearings and the spray bar oiling is not going to lubricate the big end bearings correctly.

The tappet chest covers, dynamo, and entire intake manifold were painted black. No bare aluminum. The copper hot air tube for the carburetor is a facsimile of the original, which was chrome plated steel. The end had a small flare. It extended to the top of the cylinder head, not past it.

The oil lines did have a short segment of flexible hose. The original furrels are a little more rounded on the ends than modern ones. The rubber was not black, but a blue-grey color.



This must have been something common at the time, because the handlebar grips exhibit the same blue-grey color. Note the ends where the grip was protected from the elements:



-Doug

Offline Doug

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Re: Douglas Aero 1937
« Reply #189 on: 17 Oct 2018 at 23:43 »
Eric,

Original 1936 Aero 600 oil lines.



Somewhere I should have the fuel line, but I cannot lay my hands on it at the moment.

While the following advert dates to 1937, it shows a 600 Aero in the 1936 petrol tank scheme so must be a left over model.





Pride & Clarke were advertising the Douglas line as early as April 30th 1936 issue of The Motor Cycle.

-Doug




Offline Eric S

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Re: Douglas Aero 1937
« Reply #190 on: 20 Oct 2018 at 15:28 »
I went and checked some details.
- The tree is well adjusted. 2 ports are facing right on each edge of the center web.
- Bearings are turning smooth with no play I can feel.
- Same for Conrods. Only a little barely feelable axial play.
- Tested the oil pump. Oil fed through the bottom port went down through the bottom plug. Then I put oil on the top port and turned pump the other way and oil dropped from the tree.
So I guess it's a pass.
- Checked play on the crankshaft :
   - No play on Flywheel bearing
   - LARGE play on the middle bearing like several millimeters
   - When crankshaft is sled through BOTH bearings, absolutley no play I can feel (see picture below)
   - When oil pump end is fitted, no play either of course.

Now some questions.
1. I made pictures of the marks that tappets are making on the valves. Is the pattern normal or does it tell anything?
2. What shall I do with this homemade washer. Should I make a plain washer of the same thickness?
3. How to lock the big nuts on the crankshaft? Loctite is required and is it enough?
4. I have more carbon on top of 1 cylinder than the other one. Any meaning?
5. Can I sand blast cylinders to paint them?
6. What was the finish on the aluminium parts? Polished, blasted, brushed?

« Last Edit: 20 Oct 2018 at 17:09 by Eric S »

Offline Doug

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Re: Douglas Aero 1937
« Reply #191 on: 20 Oct 2018 at 16:41 »
Eric,

Sounds like the oil pump and the spray tree/bar is o.k. However if the center web of the crank does not have the shallow grooves, the oil is not going to be able to get into the connecting rod bearings as it ought to.

You will need to be more specific about the clearance in the 'middle' bearing. Is the play in the bearing itself, that is between the inner and outer race? Or is the play in the fit between the bearing and the journal of the crankshaft? Either way, it needs more investigation as it sound like something is amiss.

The long timing side shaft, apparent lack of oil grooves on the center web, and mention of a 'middle bearing' (implying there are three) make me think you have a 1935 crankshaft in a 1936 engine. Have a look again at the photo I posted of my 1936 crankshaft. Note the timing side shaft is short. It ends at the nut for the timing pinon.

Also it contains the answer to your question about crank pin bolt retention. There are supposed to be a tab washer under the bolt head.




1. Marks of the heads of the tappet adjuster from the tip of the valve stem. Normal.
2. Make a new washer, but keep the outer diameter smaller than the root of the gear teeth. The spare list does not say how thick the washer should be. So copy what you have, or try to figure out what the optimal thickness would be to bring the face of the pinion flush with the rest of the gear train.
3. See above.
4. Simplest answer is that piston (and rings) were passing more oil than the other. Be it scoring in the cylinder, rings tired, excessive ring gap, ring flutter, or all the many things that lead to excessive amounts of oil getting past. De-coking engines was a fairly regular ritual back in the day. We are rather spoilt by modern engine in comparison with better air filtration, lack of dusty roads, and lower mileage on vintage machinery as to expect never to do need to scrape carbon. Having said that, both pistons should carbon up at about the same rate.
5. Yes.
6. The aluminum seems to have been 'smoothed-off' at the factory. Or at least in the areas where readily accessible; they did no go into every nook and cranny. Nor did they bother on areas not readily visible, such as underneath. I don't think it was polished to a mirror reflection, more of a satin finish. Most likely it was a job given to the apprentices, so the amount and diligence likely varied from motorcycle to motorcycle. As previously mentioned and shown in the adverts, much of the timing side face of the engine was painted black.

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #192 on: 20 Oct 2018 at 18:03 »
Doug

The center web has well the oil grooves machined.

As for the play in the middle bearing, It looks like the shaft bears on the aluminium frame, look at the marks on the shaft. So that's where it pivots around.
Bearings measured with a caliper at 24.9mm, shaft measured at 25mm. So considering mesuring internals with a caliper is not accurate it is a good fit.
So it should not pivot???

The pictures shows the shaft entering the bearing but not in place yet.
Shaft is much longer than on your picture. However how would the short 1936 shaft would fill the difference in length?

I have not removed the nuts yet but I don't think I have lock washers? Where can I get them?

What are those aluminium cages on your picture?
« Last Edit: 23 Oct 2018 at 08:55 by Eric S »

Offline Doug

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Re: Douglas Aero 1937
« Reply #193 on: 21 Oct 2018 at 02:33 »
Eric,

The grooves are deeper and narrower than what the factory used. Someone has modified the center web to work with the 1936-38 oiling system and the spray tree. At least the rod bearings will get oil.

Because the 1936-38 engine uses a spray tree, it does not need to introduce the oil via the end of the crankshaft. That is why the shaft does not need to extend all the way to the timing cover. Nor does the 1936-38 crankshaft require internal oil ways. This probably explains the strange, offset bush in the timing cover. It was part of the modification to install the 1935 crankshaft in a 1936 engine.

The crankshaft stops at the engine pinion nut. The nut has a pair of drive dogs for the oil pump worm. The oil pump worn spins freely on a dowel pin pressed into the timing cover, coaxial with the crankshaft, of course. A picture looking into the timing chest and a view of the inside face of the cover.





Now having said that, I do recall from a prior post that there was some differences noted between the 1936-37 and 1938 engines. Specifically, the 1938 engine the worn has a key. In my engine, no key is required. So perhaps they did extend the timing shaft back to the timing chest, though I am not sure why they would bother. They had a lot of other engines with the 'short' shaft and they never seem to have been a problem. I have a 1938 spares list, but while I have seen the 1936-37 spares list, I do not have a copy of it.

As I mentioned, typically there is no shims or bearing spacers on the timing side of the crankshaft, but again, perhaps this was a requirement of using a different crankshaft in the crankcases.

You probably will not find tab washers the right size. It is a small bolt diameter with a large hex head; an unusual combination. Most likely you will need to make them.

The aluminum cages in the photo I used are the roller bearing cages for the connecting rods.

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #194 on: 21 Oct 2018 at 19:58 »
My shaft being supposedly a 1935, it is however not hollow !?
The worm driving the oil pump is on the main crankshaft on top of the timing pinion and locked with a nut. Then the remaining of the shaft goes in this bronze bushing in the timing chest.

Offline Doug

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Re: Douglas Aero 1937
« Reply #195 on: 21 Oct 2018 at 23:41 »
Eric,

The crankshaft being 1935 was a possibility. However, as mentioned in the last email it is known from the 1938 parts list that there is something different about the oil pump worm compared to the 1936-37 models. Perhaps the crankshaft is different also, and that it is a 1938 crankshaft fitted. Unfortunately, I do not have an example of the 1935 crankshaft or the 1938 to compare to my 1936. Nor have I seen an example of these components so I have to go be indirect observations.

I do know the 1935 crank fed oil in via the end of the crankshaft. But I do not know if this was via a plain bearing in the timing chest or via an oil quill; they used a quill on several other models. It also used a duplex gear pump at the base of the timing chest. Since your crankshaft does not have a hole drilled in the shaft communicating to the throw (not hollow), it would suggest it is not 1935. I know from mine it is not 1936. Though I do not have a copy, I know the 1936-37 models are covered by a single spares list, suggesting the 1936-37 models were the same. I do not know that for 100% certain, since I do not know the contents. They did issue a new spares list for 1938, and I have a copy of that. But without the 1936-37 list, I cannot compare the part numbers to see if the crankshaft part number changed.

My best guess now is they decided to extend the shaft for 1938 to the timing chest for additional support via a bush, but not necessarily to provide a means of supplying oil via internal drilling. Why they did so when they managed without this additional support since the basic design was introduced with the 600EW in 1927 I have no idea. Nor do I know why it would then have a plug in the crankshaft web, suggesting a cross drilling for internal oiling. Until another similar example turns up it is a bit of a mystery as to what year it is or if it is a mixture of parts from different years.

-Doug

« Last Edit: 22 Oct 2018 at 19:13 by Doug »

Offline Doug

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Re: Douglas Aero 1937
« Reply #196 on: 22 Oct 2018 at 19:18 »
Addition pictures of the 1936 timing cover for comparison.



And a closer view. Note no provision in the casting for a bush (indicated by arrow), or gutter to collect oil the bearing.



-Doug
« Last Edit: 22 Oct 2018 at 19:24 by Doug »

Offline Doug

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Re: Douglas Aero 1937
« Reply #197 on: 22 Oct 2018 at 19:40 »
The 1937 Aero 600



Curiously, the cylinders appear not to be painted black.

The 1938 Aero 600



At some point in 1938 they apparently ran out of cast lugs for the saddle springs and substituted a bit of steel tube with the ends flattened! It did the job and was much simpler (and cheaper). I have seen it on a few late Aeros, so not just a one-off.

Back to your engine, Eric, I wonder what the serial number would indicate what year it is?

1935 Blue Chief (probably ruled out by now) would be 5/H***. A crankcase from the similar Endeavour would be 5/J***.
1936 would be 5/L***, 6/L***, or 6/M*** for the 500 and 600cc models. Not sure what the difference between the 6/L and 6/M is.
1937 would be 6/P*** or 6/PM***. Again, do not know the significance of "M".
1938 would be 6/Q***.

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #198 on: 22 Oct 2018 at 20:36 »
Doug
here are the serial numbers of the bike.

Eric

Offline Doug

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Re: Douglas Aero 1937
« Reply #199 on: 23 Oct 2018 at 01:16 »
1937 frame, 1936 crankcases, and crankshaft and timing cover??? The mystery continues!

-Doug