Author Topic: Douglas Aero 1937  (Read 79421 times)

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Offline cardan

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Re: Douglas Aero 1937
« Reply #350 on: 06 Apr 2020 at 05:34 »
1. Are the ring grooves clean enough?
2. piston condition remain still usable? I hope so as I don't plan to change them and in any case the engine was running fine with them in.
3. Any order/matching in ring gap dimension or we just don't care?
4. I cleaned and removed any gasket compound (used on top of paper) surplus and removed everything I can see. Is it quite critical given the oiling system to have a real clean engine interior or is it tolerant. I mean do I need to make 200% sure nothing is left behind that may plug the oiling system. Not sure of the pression and size of ports in this system.
5. any comment?

Hi Eric,

1. Probably
2. They look OK, but the critical issue is the fit of each piston to its cylinder. Check there is more than 6 and less than 10 thou between the skirt of the piston and the cylinder wall at the bottom of the stroke. I assume the bores are ok - not too badly worn at the top. If there are any scuff marks on the pistons, smooth them off with a "flat" file - preferably a brand new one that has never been used on steel.
3. Personally, I think 4 rings per piston is way too many in a bike like this. I'd use plain rings in the top two grooves and leave the others empty. Not everyone will agree, so if you want to fit more use the order proposed above. Use the smaller gaps on the top rings, and the shockers on the skirt. The ring gaps should be set by filing, rather than cutting. Make sure - with a file - the ends of the rings are square and free from burrs.
4. Clean is good. If you have sand/glass/abrasive blasted anything internal you will need to clean, clean and clean again. A few tiny floaties of gasket material won't hurt, but if you wash thoroughly most should be gone.
5. Comment: If you don't have a copy of Radco's "Vintage Motorcyclist's Workshop" get one. It has most of the answers to our questions, and contains almost nothing that is "wrong". I like the way Radco recognises that we're not trying to build MotoGP racers, and cuts some slack to the home mechanic!

Cheers

Leon

Offline Red

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Re: Douglas Aero 1937
« Reply #351 on: 16 Apr 2020 at 08:04 »
I didn’t want to start a new topic as the subject is briefly mentioned within the pages of this exchange. I have an Aero 6oo and my son has an Aero 500 but on both engines the ball and spring in the oil sight drip feed on the timing cover is missing. Doesn’t affect the running of the engines but as soon as we switch off, we have to remember to turn off the oil supply as the window will quickly fill up with oil. Both engines have a tap in the oil supply line. I believe the ball bearing is a ¼ inch, but can anyone give any dimensions for the spring – length, number of coils and wire diameter. I assume it is a very light spring, possibly something like a magneto brush pick up spring. Any help/guidance will be very much appreciated. Thanks.
Roy

Offline Eric S

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Re: Douglas Aero 1937
« Reply #352 on: 16 Apr 2020 at 08:25 »
Interesting, I never notice any spring and ball and did not know it was supposed to be there !

Offline eddie

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Re: Douglas Aero 1937
« Reply #353 on: 16 Apr 2020 at 08:35 »
Roy,
        It could possibly be the same spring and ball as used for the engine breather in the timing end of the crankshaft on the 2¾ models - Douglas were good at making use of existing parts from earlier models!

  Regards,
                 Eddie.

Offline Red

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Re: Douglas Aero 1937
« Reply #354 on: 16 Apr 2020 at 08:49 »
Hi Eddie
Thanks for that. In which case I suppose there is a possibility that pre war spares may have some parts, but I will have to wait until the current crisis is over and the spares service is up and running again. As I say it doesn’t affect the running of the engine, we just have to remember to turn off the oil supply when we park up.

Roy

Offline eddie

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Re: Douglas Aero 1937
« Reply #355 on: 16 Apr 2020 at 09:13 »
More important - turn it back on when you resume your run!!!

  Eddie.

Offline Aero

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Re: Douglas Aero 1937
« Reply #356 on: 16 Apr 2020 at 10:26 »
Hi Roy,
my 600 luckily had the spring fitted.
It was broken in two but at least it meant I had something to measure up, and it turned out to be the same gauge as a B string on an old electric guitar that was knocking around.
Just checked the workshop & I still have my first attempt at winding one. As luck would have it my later attempts were no better!
Its yours if you can make use of it.
Mark

Offline Red

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Re: Douglas Aero 1937
« Reply #357 on: 16 Apr 2020 at 16:07 »
Hi Mark

That's very kind of you. If you could post it to me I will be happy to refund the postage. I assume you are a club member and my address is on the inside cover of the Conrod under  Secretary. Many thanks.
Roy (Staunton)

and yes Eddie - that is my biggest worry. I am parnoid about checking that the oil supply is turned back on before I ride off. A club member well known to both you and I (DR) did exactly that and he tells me he covered 20 miles before the engine seized!

All the best .


Offline Eric S

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Re: Douglas Aero 1937
« Reply #358 on: 16 Apr 2020 at 17:21 »
I would be interested to see where this spring fits and how it works. My bike do not have it and I get used to open and close the oil tap since I had it as I was told to do so.

Offline Red

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Re: Douglas Aero 1937
« Reply #359 on: 17 Apr 2020 at 08:38 »
Hi Eric

Perhaps Aero (Mark) can give us his advice as to how this is actually fitted as like you I don't have these parts fitted to my bike. My understanding is that with the engine running the ball is lifted of it's seat and allows oil to be pumped to the drip feed tube. When the engine is stopped the spring pushes the ball valve back on to its seat and stops the oil flowing otherwise the oil sight window quickly fills up with oil and eventually drains down in to the sump. Even with these parts fitted I am told by those far more expert than me that it is recommended that you still have a tap fitted in the oil feed line from the oil tank otherwise if left overnight some oil will still seep through.

Roy

Offline Aero

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Re: Douglas Aero 1937
« Reply #360 on: 17 Apr 2020 at 12:44 »
Thats a good description of how it works. However I have not found the need to turn the oil tap off. Even if not using the bike for a few weeks the most I have seen the sight glass is half full.
To save me stripping it down to show the gubbins I've marked the spring position in red & the ball bearing sits underneath marked in black.

Offline Red

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Re: Douglas Aero 1937
« Reply #361 on: 17 Apr 2020 at 13:25 »
Thanks Mark

It was interesting to hear you say that even when left for a few weeks the oil sight glass was only half full. As I mentioned to Eddie I am paranoid about making sure I've turned the oil tap on before moving off. The last thing I need is a seized engine. Once I get these parts fitted I will experiment with the need for the tap in the oil feed line. If I can leave it on all the time I think I will be alot happier.

Roy

Offline Eric S

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Re: Douglas Aero 1937
« Reply #362 on: 17 Apr 2020 at 20:26 »
My memory is really bad. A few months back I removed the assembly and I remember this spring and ball. As for the tap, I am using the wheel on top. I close it and open about 1/2 turn I guess.

Offline Aero

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Re: Douglas Aero 1937
« Reply #363 on: 18 Apr 2020 at 09:57 »
Roy, the spring is on its way.
If you tap the ball bearing into its seat sharply using a brass or alloy drift it should seal nicely.
This is how much oil is in my sight glass after the bike standing for the last 2 weeks.

Offline Red

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Re: Douglas Aero 1937
« Reply #364 on: 18 Apr 2020 at 14:02 »
Hi Mark

Thanks once again. If I can achieve the same result I will be happy to leave the in line tap on all the time. Without the ball and spring the sight window fills up very quickly - matter of minutes so I need to shut off the tap even if I'm just stopping for petrol. My son has the same problem with the 500 version he has just finished restoring - see photo attached. He was hoping to take it to this years Annual Rally but sadly as you know this has been cancelled. Never mind there is aways next year so I will keep working on my Aero 600 so I don't show him up! Mind you I've got the bigger engine although frankly there doesn't seem to be any difference in performance.

Best wishes

Roy 

Offline Eric S

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Re: Douglas Aero 1937
« Reply #365 on: 01 May 2020 at 13:32 »
I am now ready to re-install the cylinders.
What is the best, slide the piston and top rings in the cylinder, then drive the piston's axis on the conrod and then drive the bottom ring in the cylinder
Or
Install the piston on the conrod and then drive the piston in the cylinder?

I got a tool to compress the rings but it can't be used as it does not fully open and is too wide.

Also am I happy with a 2.5 grams difference in piston weight?
Any tip welcome one more time.
« Last Edit: 01 May 2020 at 17:59 by Eric S »

Offline Eric S

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Re: Douglas Aero 1937
« Reply #366 on: 10 May 2020 at 11:11 »
Making slow progress on engine assembly.
Still have to adjust for timing where a friend should be able to help me.
As for the tappet adjustment, the book of jhe Douglas ask for .006". Is that still correct although I don't see ay reason to have it changed over the years?

Offline Red

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Re: Douglas Aero 1937
« Reply #367 on: 10 May 2020 at 12:43 »
Hi Eric

I was told .006" exhaust and .004" inlet

Roy

Offline Eric S

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Re: Douglas Aero 1937
« Reply #368 on: 10 May 2020 at 13:26 »
Anybody knows the wrench size normally required to adjust the tappets? I did not unlocked them while the cylinders were out. Too bad and the nuts are damaged so wrenches fits oddly. Seems to be 3/8 and 7/16...
Adjustments are all over the place.

Edit : it's well 3/8 and 7/16.
« Last Edit: 10 May 2020 at 16:28 by Eric S »

Offline Doug

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Re: Douglas Aero 1937
« Reply #369 on: 11 May 2020 at 17:01 »
I have a factory supplied service sheet for the Aero models and it mentions 0.006" for the tappets. No distinction for either inlet or exhaust. Nor if the setting was done hot or cold.

By the mid-thirties Douglas were using a lot of Whitworth wrench sizes. So 0.340, 0.4245, 0.520", etc. Earlier you do find imperial fraction sizes. The tappet jam nut us part number 8376, so predates the Aero era quite a bit. That number dates back to the time of the 350EW.

-Doug

Offline Red

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Re: Douglas Aero 1937
« Reply #370 on: 11 May 2020 at 17:12 »
Hi Doug

Is it possoble to post a PDF copy of the service sheet you have for the Aero. The only information I have when servicing my Aero is what other people tell me. Hope you can help. Thanks

Roy

Offline Doug

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Re: Douglas Aero 1937
« Reply #371 on: 11 May 2020 at 18:09 »
Roy,

Much of it is the usual palaver about running in and adjustments. Only a little really useful info. I have uploaded it here in the Technical Articles board:

https://www.douglasmotorcycles.net/index.php?topic=8098.msg31144#msg31144

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #372 on: 11 May 2020 at 19:06 »
Tappet adjustments made a .006".
Cams measured and all are equals.
When I check or valves opening (I am not sure of english term for that, balance maybe?) the valves on 1 cylinder are closing and opening when piston is up for less than 1mm
On second cylinder in same conditions, valVes open for 3mm+
I can't understand why with same cams and same tappet adjustments I come with different valve openings?

PS Doug I sent you an E mail
Eddie I sent you a PM
« Last Edit: 12 May 2020 at 08:10 by Eric S »

Offline Red

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Re: Douglas Aero 1937
« Reply #373 on: 12 May 2020 at 08:41 »
Thanks Doug - much appreciated

Roy

Offline Eric S

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Re: Douglas Aero 1937
« Reply #374 on: 01 Jun 2020 at 11:36 »
Still working painfully and as time allows on this engine and still finding some weirds arrangements.
I just realised (thanks to Doug) that the tappets were the wrong ones.  So I have to replace the rear cylinder exhaust tappet with the front cylinder inlet tappet.
But the latter being close to the engine block, it does not slide off the guide.
Cylinders and pistons are in place but how can I get off the tappet, I assume I have to remove thje guide but how? Is it screwed or pressed in? What would be the simplest to slide off this tappet?

Offline Aero

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Re: Douglas Aero 1937
« Reply #375 on: 01 Jun 2020 at 11:46 »
Hi Eric,
unfortunately i think you will have to remove the front cylinder to allow you to tap the inlet valve guide out.
Its best to use a brass drift to avoid damage to the indentation slot provided for removal.
The guides are a taper press-fit, and contain an "O" ring to seal them.

Offline Eric S

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Re: Douglas Aero 1937
« Reply #376 on: 01 Jun 2020 at 17:11 »
Thank you my friend. I was so sorry I had to take off the cylinder ...
but you can't always loose !
I had a look and saw that the guide was not blocked under the cylinder. So I removed the nut holding the tab that hold in place both guides and with a mild blow on the slot, the guide popped out. I exchanged the tappets and now the valves are opening and closing on .020-.025 gages @TDC on boh cylinders.
I am happy and hope nobody will explain there is something else wrong.
I will push back the guide, do I need to heat the block to secure it or just the clamp holding it is fine?

I did not removed the tappets so it's a previous owner/restorer business. I guess the bike will work much better if I ever can make it work.
But I still move forward, slowly but forward.

Offline Doug

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Re: Douglas Aero 1937
« Reply #377 on: 01 Jun 2020 at 18:24 »
Eric,

Just seat the tappet guide in the taper with a light blow from a soft drift to make sure it is firmly seated. Then apply the bridge clamp. No need to heat the casting. Make sure you install the tappet guides so that you have access to the notches for the next time they are removed. Three have the notch facing the timing cover, but the rear exhaust needs the notch pointing downward so that you can access it via the opening in the casting.

-Doug

Offline Aero

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Re: Douglas Aero 1937
« Reply #378 on: 01 Jun 2020 at 18:39 »
Eric,
I'm glad you had some luck at last.
I had the same problem of incorrect tappet orientation by some previous owner, but on my bike the guides were obscured by the cylinders casting.
I also found that casting completely obscured the breather hole, so the breather system was totally blocked! Maybe it was that way from new or perhaps it had a cylinder change in the past & they never checked.

Offline Eric S

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Re: Douglas Aero 1937
« Reply #379 on: 05 Jun 2020 at 20:57 »
Some questions here.
On A, I don't have a washer or anything between the nut and the gear below. Is that OK? And how can I tighten the nut, the engine rotates when tightening.
How tight does it need to be, loctite? Do I have to lock the engine to tighten the nut?

On B, there is a lock washer. How tight and loctite?

On C, I have flat washers, same questions, how tight and loctite?

Offline Eric S

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Re: Douglas Aero 1937
« Reply #380 on: 10 Jun 2020 at 08:33 »
Hi folks

I found my way on B and C above but what about the main A nut?
I thought about holding the crankshaft via the flywheel nut but this may disturb the crankshaft.
I am thinking using a cloth in the gear teeths to lock the engine while I tighten it.
But the questions remain how tight does it need to be?, no washer is OK? and do I have to Loctite it?

Offline Aero

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Re: Douglas Aero 1937
« Reply #381 on: 10 Jun 2020 at 09:47 »
Hi Eric,
when I first reassembled my engine I had no washer behind nut "A" but I later found that without a washer there was no preload on the gears, and they could move slightly, so I fitted one.
I would use Loctite on the threads & stop the crank rotating using the flywheel nut as you don't need to apply a huge amount of torque.

Offline Eric S

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Re: Douglas Aero 1937
« Reply #382 on: 11 Jun 2020 at 20:21 »
Thank you for this information. I will get a washer even though I can't see how a washer might pre-load the gears?

Offline Aero

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Re: Douglas Aero 1937
« Reply #383 on: 11 Jun 2020 at 20:44 »
Axial pre-load (clamping force)

Offline Eric S

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Re: Douglas Aero 1937
« Reply #384 on: 21 Jun 2020 at 16:59 »
Hi all
On my engine, the timing side of the crankshaft seats in a bronze/brass bushing. Shaft has an helicoidal groove.
I am wondering if it would be wise to use mecanical grease rather than oil in the brass bushing (plugged on one side)? Is grease or oil the best? I thought grease may end up making a solid piece of old grease and prevent subsequent oiling from the engine's oiling system...

Offline Aero

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Re: Douglas Aero 1937
« Reply #385 on: 21 Jun 2020 at 20:37 »
I seem to recall there is an oil feed straight from the pump to that bushing in the timing cover, so best only use oil to pre-lube it.
Might be a good time to clean the multiple oil passageways out in that cover too if you haven't already?

Offline Eric S

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Re: Douglas Aero 1937
« Reply #386 on: 21 Jun 2020 at 21:18 »
Good point.
I am having a Ford V8 being rebuilt and I made sure the rebuilder clean and check the oil circuit. Good to remind me to do it there too !!

Offline Eric S

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Re: Douglas Aero 1937
« Reply #387 on: 22 Jun 2020 at 10:02 »
Checked the oil system, I blew in the oil arm that brings oil over the conrods and it goes not through. Is it normal as it is kind of backwards against the normal oil flow?
How can we test the pump to make sure it works without taking everything apart?
I tried to turn the pump by hand but it's probably going too slow.
« Last Edit: 23 Jun 2020 at 18:19 by Eric S »

Offline Doug

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Re: Douglas Aero 1937
« Reply #388 on: 24 Jun 2020 at 17:11 »
Eric,

The following post, though for an A31 model, shows an identical oil pump circuit. By applying some oil to the appropriate hole(s) you should see oil pump through. It is a positive displacement pump, so while it may pump slow when turned by hand, it will pump.

https://www.douglasmotorcycles.net/index.php?topic=4288.msg15399#msg15399

This post shows oil transfer from the crankcase to the timing chest, whence it is scavenged.

https://www.douglasmotorcycles.net/index.php?topic=5936.msg21795#msg21795

In this earlier post of your engine one can see the bush supporting the outboard end of the crankshaft. There is a gutter in the timing chest to collect oil and lead it via a drilling to the bush. One hopes it got pressed back in the precise orientation to maintain alignment of the crankshaft axis! And there has to be a hole from the gutter to the bore.

https://www.douglasmotorcycles.net/index.php?topic=5829.msg21297#msg21297

It looks like the bushing interrupts the drilling from the bottom of the timing chest that scavenges oil and returns it to the oil tank. The corresponding part of the bush likely should be relived so that it does not form an obstruction. It should not break through into the bush. It does not provide oil to the bushing and any connection will likely cause the scavenge circuit to suck air in rather than lift the oil.

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #389 on: 24 Jun 2020 at 18:25 »
Thank you Doug
Looking at the 2nd link, I recognise my engine (and then I realised it was Polly's so that's well it) and it already had the reversed front admission/rear exhaust tappets !

As for the bushing you are right, I have well this small port and it's well aligned. I checked for it (as I can't remember such things) after Aero told about it.
In the post you talk about a sheared pin.

I tried the pump, it takes quite a few drops of oils but the oil drips well from the spraybar, turning by hand.
I will test late rthe scavenging portion and try to find out the bypass in&outs.


Offline Aero

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Re: Douglas Aero 1937
« Reply #390 on: 25 Jun 2020 at 09:39 »
Its worth removing the pump & checking the previous owner wasn't having a bad day gasket making

Offline Eric S

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Re: Douglas Aero 1937
« Reply #391 on: 05 Jul 2020 at 19:11 »
Checked the oil pump, gasket was nice and neat. Stayed well in place.
I am in the final stages of closing the engine, waiting for light Loctite to "glue" the nuts holding the plate over the distribution gears.
I used a good amount of new motor oil on the parts. Is there anything special to do when closing the engine to help in pre lube before starting the engine?

Offline Aero

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Re: Douglas Aero 1937
« Reply #392 on: 05 Jul 2020 at 20:59 »
These engines are basically a wet sump with pumped recirculation, so its a good idea to start off with a quantity of oil for the crank to sit in & splash around the bores. I haven't measured exactly how much sits in mine but I'd estimate 200ml

Offline Doug

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Re: Douglas Aero 1937
« Reply #393 on: 06 Jul 2020 at 04:06 »
You will also want to pour some oil in the timing chest. It is meant to pool up to the depth of the weir before spilling over and being scavenged by the pump. The depth ensures the teeth of the lower cam gear dip into the oil. Oil vapor passing through from the crankcase chamber normally maintains the oil level. But with a newly rebuilt engine it would take time for the oil level to build up and the gears might run dry in the meantime. 

-Doug

Offline Red

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Re: Douglas Aero 1937
« Reply #394 on: 06 Jul 2020 at 09:13 »
I was advised that even when doing an oil change to remove the dynamo and pour in about 1/4 pint of oil into the timing chest before restarting the engine for the same reason.

Roy

Offline Eric S

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Re: Douglas Aero 1937
« Reply #395 on: 12 Jul 2020 at 17:07 »
What kind of gaskets do we want here?

Offline Doug

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Re: Douglas Aero 1937
« Reply #396 on: 12 Jul 2020 at 17:11 »
Eric,

Hard fiber washers, just as shown. Red is the traditional color.

-Doug

Offline Eric S

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Re: Douglas Aero 1937
« Reply #397 on: 30 Jul 2020 at 18:49 »
When I had the cone rebuilt on the crankshaft, the guy that made it also made 2 new washers to place under the bolt that hold the crankshaft pieces together.
Those washers has tabs that you fold up against the bolt head.
I recently saw a picture of one of those washers on a crankshaft except it had 2 tabs, one that goes up against the head, like he did for mine and one (or maybe even 2) that bends down against a flat on the crankshaft.
I would like to show him this picture of a 2 tabs washer but I can not find it on the forum. If anyone could point it out for me I would appreciate.
Then I will open a discussion with forum members and the guy that made mine and see if a single tab washer will work...