Author Topic: Douglas Aero 1937  (Read 47690 times)

0 Members and 1 Guest are viewing this topic.

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #250 on: 09 Sep 2019 at 18:32 »
I finally went ahead and prepared the parts to put them together.
I am anxious as I never went so far in disassembling an engine and would like to avoid making mistakes in re-assembling.
Plan is
1- install the bearings
2- Close the 2 Halves on the crankshaft.
3- Install the pistons and cylinders
4- Install the timing side
5- install the oil pump cover and generator.

And what do you think of my pistons? I have 2 scratches on the side.

Sorry pictures are a bit large :roll:
« Last Edit: 06 Dec 2019 at 07:38 by Eric S »

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #251 on: 09 Sep 2019 at 19:59 »
Hi Eric,
the marking on the pistons would suggest to me that there is insufficient piston to bore clearance.
I have had similar issues with my engine & had to hone the bores twice.
It seems these engine need a lot more clearance than most machine shops realise.
At the top of the piston just below where the rings sit you need around 6 to 7 thou clearance, and at the bottom of the skirt you need around 5 thou clearance, piston to cylinder, measured at right angles to the piston pin.

It would also be a good idea to have a trial assembly of the crankshaft, bearings & crankcases, to see if you need to shim between the crank & the bearings to get the crankshaft axial clearance down to a reasonable level.
Mine needed around a millimetre each side, although I have also installed a thin 0.15mm paper gasket between the crankcase halves.
Originally there would have been a 1mm thick oil thrower washer installed on each side of the crankshaft, which would account for the need for shims around the same thickness.

Offline Doug

  • Global Moderator
  • ****
  • Join Date: Mar 2004
  • Posts: 3559
  • Location: Pennsylvania, USA
Re: Douglas Aero 1937
« Reply #252 on: 10 Sep 2019 at 00:34 »
Eric,

I am personally not a fan of plastic cages for bearings used in engines. Particularly ones where you often have to heat the case up to drop the bearing in and out. Also, the one on the timing side looks to be very light duty, given the few number of bearing balls.

As mentioned already, you will need to assemble the crankshaft in the cases at least once to test the end float. There are ways to pre-measure this, but most folk do not have the measuring equipment and fixturing to do it. I forget now if the Aero 600 was still this way, but earlier engines were designed for a 21mm wide bearing that even then was becoming obsolete so they incorporated a 1mm shim with a 20mm wide bearing. Even if that was addressed, they still typically bored the flywheel side deep so as to allow for a few shims to get the end-float just right. The shims go between the flywheel side crankcase and the ball bearing.

The pistons look like they have been clawed by a bear! That is more than what would be described as a few scratches... Ease down the high spots and reuse with new rings. It is not ideal, but probably you do not have much choice as pistons are getting hard to come by. Is that recent or old history? If recent, then there is still a problem that will need to be addressed as to why the pistons seized.

-Doug

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #253 on: 10 Sep 2019 at 08:04 »
Thank you Doug and Aero
You point out the weak design of the bearing. Maybe I shall use the old one that was not really bad.

As for the pistons, they have no history. I just removed them to work on the crankshaft and have the flywheel cone rebuilt. I just took them off and put them aside.
I didn't had any trouble with the engine as far as I can tell. Only problem was the clutch.
There is no matching seizing marks in the cylinders as far as I can see. Even though the cylinders are not nice. I will send pictures of them later.

Do you have links to get rings?

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #254 on: 10 Sep 2019 at 17:59 »
Here are the pictures of the cylinders. 2 of the same cylinder as it came off the engine. One slightly honed.

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #255 on: 10 Sep 2019 at 21:06 »
They look like they need a bit more honing. As mentioned previously check the piston clearances to see how little or much you can hone. For the last 10 seconds of honing, with the drill on slow speed, move the hone rapidly up & down the length of the bore, this will give you a nice "cross-hatch" finish that will help the rings bed in quickly. There is a place near me (Shropshire) called FW Thornton who will supply piston rings worldwide.

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #256 on: 11 Sep 2019 at 08:46 »
Thank you for your help.
I called the mechanic that made the cone and I will visit him on Monday so he can have a professional look and measures of cylinders and pistons. He will check for roundness or lack of the cylinders.
I will have him check this tiny bearing too and the rest of the engine.

In the meantime I would appreciate to get the factory dimensions of the pistons so I can check if I have originals or replacements as well as the bore dimensions.

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #257 on: 16 Sep 2019 at 10:54 »
Anybody could tell me if those pistons are originals?
Anydimesions available?

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #258 on: 16 Sep 2019 at 19:31 »
They look like Hepolite replacements, the same as mine.
Standard bore is 74mm, with oversizes at 20, 40, & 60 thousandths of an inch, so roughly 74.5mm, 75mm, & 75.5mm.
If you clean the piston tops the oversize should be marked "20 thou" etc on the crowns, together with Hepolite or Heplex. They are unavailable new these days.
« Last Edit: 16 Sep 2019 at 19:40 by Aero »

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #259 on: 19 Sep 2019 at 08:12 »
Do we know if Hepolite replacements are the same dimensions everywhere as the originals. We may have to chase for replacements so need to know what we are looking after. If we found replacements that are different than the Hepolite but same as originals it would be too bad to miss them.

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #260 on: 19 Sep 2019 at 12:40 »
Original (I assume) on the left, Hepolite on the right

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #261 on: 19 Sep 2019 at 12:43 »
Underside

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #262 on: 30 Sep 2019 at 10:14 »
I talked to the engine builder this morning.
Cylinders are measured at 74,75mm. Pistons 74,60mm
Cylinders' walls are porous and he's advising re-boring.
However how can I get new pistons? What are the options? He advised against custom made pistons as quality is not really good on his experience...

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1439
  • Location: Hampshire, UK
Re: Douglas Aero 1937
« Reply #263 on: 01 Oct 2019 at 08:29 »
Eric,
        If the bores are not marked, don't get them rebored - rebuild the engine with the old pistons, but fit new rings. With .15mm clearance, they should be fine! Ignore the comment about reboring because the bores are 'porous' - taking another .25mm cut wont make them any better - in fact, 'porous' bores will retain more oil and prevent further 'nipping up'. Also, don't get too paranoid about the quality of repro pistons - the originals wouldn't have been any better.
    When you rebuild your engine, build it on any cheap motor oil until it is 'run in' - then go over to a better quality oil. Modern oils are so effective that the running in process doesn't get completed before any high spots become glazed. ( I used to work on marine diesels, and one of our craft had to have all the liners and pistons replaced under guarantee because too good an oil had been used during the running in period, and the bores had become glazed!)

  Regards,
                  Eddie.

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #264 on: 01 Oct 2019 at 14:59 »
Great thank you Eddie for bringing some good news.
I assume it still have to be honed though??
Just in case so I/we know, what would be the options should one need pistons?

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #265 on: 02 Oct 2019 at 11:51 »
As Eddie has already said, 0.15mm is a good clearance so best to just lightly hone any marks out of your cylinders & re-use the old pistons.
I have a couple of good used pistons measuring 74.7mm if ever you get stuck in the future, but I'm holding on to them for the moment in case I find any spare barrels.

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #266 on: 21 Oct 2019 at 19:04 »
I got the engine parts back.
They surfaced the heads, the top of the cylinders and honed the cylinders somewhat.
As said earlier, he was concerned about the surface quality of the cylinders being porous but I asked him just to hone the cylinders without re-boring them so he did the best he could.
They supplied new rings but did not cut them. He told me to adjust with a 0,4mm/.016" gap. Is that OK?

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #267 on: 22 Oct 2019 at 18:27 »
It looks like your engine builder has used long honing stones.
In this instance I think a flex (ball) hone would do a better job.
Somewhere between 12 & 16 thou is ok for the ring gap.
If you gap them now at 12 thou by the time they've bedded in they will probably be more like 16.

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #268 on: 04 Nov 2019 at 10:04 »
Looking at reassembling the engine now and here is a first question.
The bearing on the crankshaft, clutch side is a tight fit and slides in tightly. Surface on the shaft is rough. Removing the burrs may make the bearing loose on the shaft.
How would you do it. Install it with some kind of compound, dry, file off the burrs?

Also I have an oil sling on the same side on top of the bearing. How can I measure and determine if I need any more spacers/washers. How close does it need to be?

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #269 on: 11 Nov 2019 at 22:07 »
No Idea?

Offline Doug

  • Global Moderator
  • ****
  • Join Date: Mar 2004
  • Posts: 3559
  • Location: Pennsylvania, USA
Re: Douglas Aero 1937
« Reply #270 on: 13 Nov 2019 at 02:20 »
Eric,

The state of this engine continues to dismay!

I would stone off the burrs. It is a similar situation to the practice of center punch marking shafts. Besides being a deplorable practice, over time the high spots get compressed, resuming the original slack fit. Better to know now if the fit is slack and not providing the proper support and remediate it.

I do not know if this is worth the trouble for a single engine, but I made a simple gauge to measure the end float of the crankshaft for the DT engine since I have done a several and have a few more to do. This is a cylinder of aluminum turned to just a little under the ball bearing outer diameter so that it is a slack fit . Both ends are faced square with a chamfer equal to the bearing radius. The length is not critical other than it needs to be a little less than the distance between the bearing bores. To use, the measuring cylinder is inserted into where the bearings would go and the crankcase bolted up tight with any gaskets that you will be using. The measuring cylinder is push all the way to one side until it bottoms and a dial indicator is arranged to contact the end face and the indicator zeroed. The measuring cylinder is then pushed to the other side until it abuts and the indicator reading of the distance traveled observed. The distance inside the crankcase is the indicator reading plus the length of the cylinder. Then I assemble the bearings and slingers onto the crankshaft and take a measurement across the outside. I then can figure out how much shim is required to achieve the desired end float. That enables me to set the end float in one try. It requires several things not everyone may have available; a bar of metal, an lathe, and measuring equipment.

The traditional way is to assemble the crankshaft into the crankcase and using a mallet, thump the crankshaft to one side and measure the distance from some reference point on the crankshaft relative to a reference point on the crankcase. Then using the mallet to shift the crankshaft to the opposite side the measurement is repeated. That tells you the end float of the crankshaft. You then add or remove shims from behind the bearing races (usually on the flywheel side if both mains are ball bearings) to correct end float. The nuisance is the bearings are a shrink fit in the cases, so you have to go through several sessions of heating the crankcase to pop the bearing in and out as to experiment with shims.

-Doug

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #271 on: 14 Nov 2019 at 16:22 »
Doug

thank you for this information
The thing is the shaft has no really burrs or high spots. It's just not smooth. Bearing slides in and out without feeling any rough surface. It just pops in and out. It's a bit tight and I have to play it around so it can slide in. Making the shaft smooth would have some play...

Not sure to understand though. The bearings are inserted in the case and then shims are between the bearings and the crankshaft. It was this way when I took it apart. But why do you say "you have to go through several sessions of heating the crankcase to pop the bearing in and out as to experiment with shims".
Seems to be the opposite than "behind the bearing races (usually on the flywheel side if both mains are ball bearings)"

Then wouldn't it be easier to fit the bearings first and using the aluminum rod sliding bar method measure the required length of crankshaft+shims?
Those are going to be tiny shims but do we want one on each side to center the crankshaft or is it not important?
« Last Edit: 14 Nov 2019 at 16:27 by Eric S »

Offline Doug

  • Global Moderator
  • ****
  • Join Date: Mar 2004
  • Posts: 3559
  • Location: Pennsylvania, USA
Re: Douglas Aero 1937
« Reply #272 on: 14 Nov 2019 at 17:15 »
Eric,

The factory installed the shims between the crankcase and the bearing. There are slingers (in some designs) between the bearing and the crankshaft, but these are not intended to be shims. Presumably Kingswood (and other factories) did this to protect the thin and delicate shims. If they were installed on the crankshaft they would be more prone to damage during assembly. The crankshaft journal has a fillet between it and the throw to avoid a stress riser. If the shim registered on the crankshaft, the hole through would have to be bigger than the journal so that it would clear that fillet. During assembly you would have to be careful the shim rode up that fillet and registered on the flat face, else it might get pinched and not allow the bearing to seat fully. Also they might have figure the crankshaft shuffling back and forth the amount of the running clearance would unduly hammer or at minimum compress pinch the thin shims as the crankshaft flexes, so behind the bearing they are static as well as better protected. It seems to be normal practice, not just with Douglas.

I actually do not remember a slinger(s) on my 1936 Aero, but it has been a while since the engine was assembled and I did not take a photo of the assembled crankshaft that I can refer to. Most designs have a shallow spigot for the slinger to register on, just for the purpose to keep it off the journal radius. I do have a picture of the disassembled crank, and I do not see a spigiot for the rabbet so the must have done without.

Anyway, since the shim is behind the bearing, it has to be installed before the bearing is shrunk into the case. And since the traditional method involves some trial and error, the shim (and bearing) needs to be removed/installed several times until one gets the shim amount correct. I think that also answers why you cannot us the aluminum bar to just gauge the distance between the bearing races once in the crankcases.

One could divide the shims between the timing and flywheel side, but to be honest I cannot recall ever finding shims anywhere but on the flywheel side. The amount is so small, that it is neither enough to throw the rods significantly off center, or enough to correct any misalignment of the conrods. The rods rarely are exactly centered nor is it critical (allowing for the usual no rubbing, turns over freely, etc.) The flywheel side crankcase is easier to heat up to fix the bearing; easy access inside and out for the application of heat. I suppose that is why the shims are installed on that side.

-Doug 

[fix typo. 14Nov19. Doug]
« Last Edit: 15 Nov 2019 at 02:38 by Doug »

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #273 on: 14 Nov 2019 at 21:57 »
I used 2 x 0.3mm shims to get my endfloat correct, in conjunction with 0.25mm thick paper gaskets between the crankcase halves.
Might be a good starting point?
PS that is in conjunction with the 2 oil slingers, which are each 1mm thick

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #274 on: 16 Nov 2019 at 13:09 »
I got a bar of aluminum and will turn a tool next week.
so if I got it well we should have :
Shim - Bearing - oil slinger - crankshaft - oil slinger - bearing - shim (if needed)
I had something "different"

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #275 on: 19 Nov 2019 at 17:45 »
Well the bar I got was too small in diameter so I had to use regular washers lathed down.
I screwed one on one side (not proud of the job there), drilled and thread the other end so I can use an adjusting screw.
Then another washer and a plate of aluminum (I might as well use on this plate) with a small hole to slide a scredriver and I have an adjustable gage that can be measured out of the engine.
Thank you Doug for the idea to use this kind of tool.
When I will have measured this length and that of the crankshaft, I will come back and see what I need in term of shims and oil slingers.
« Last Edit: 19 Nov 2019 at 17:51 by Eric S »

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #276 on: 22 Nov 2019 at 07:53 »
Well the design of my tool may work with somebody with better lathe skills than me. But the play in the screw, the staking of washers makes it 0,3mm "bent" from one side to the other.
Now the question is how accurate do we need to be there? I assume we still need to have a bit of play between the crank and the engine?

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #277 on: 27 Nov 2019 at 08:48 »
Sorry, anybody can help me on my question?

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #278 on: 27 Nov 2019 at 09:13 »
I couldn't find any mention of crankshaft end float tolerances anywhere so set mine to 4 thou & the engine is running well.
I also fitted a modern nitrile oil seal to the flywheel side crankcase whilst the engine was apart, as there is enough lube for the primary chain & clutch  from the breather alone on these engines

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #279 on: 27 Nov 2019 at 13:21 »
Heres a pic of the seal mod

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #280 on: 27 Nov 2019 at 16:56 »
The engine has the same modification...

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #281 on: 29 Nov 2019 at 11:25 »
So nobody have any advice except Aero on crankshaft end float tolerances? .004" seems tight for me.

Then where will I found the shims? Can we buy them off the shelves?

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #282 on: 29 Nov 2019 at 14:07 »
Don't forget you are in effect levering against the end of the crankshaft every time you pull your clutch in.
Too much end float & you will actually see the flywheel move out when the clutch is applied.
Trust me, it is not the first time I have done this ;)
Shims are easily available on ebay.

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #283 on: 04 Dec 2019 at 13:09 »
I managed to make some measures as best as I could. Some parts are not easy to measure s I did my best.
Adding the bearings and the crankshaft, I come to 121.94mm - 122.34mm
The engine blocks as from face to face 124.14-124.44mm

That leaves 1.80 to 1.2mm for the oil slings and shims. I have oil sling (OK did not measured it and it is not smooth, so may replace it?) (That's .071" to .098")
Do I need oil slings on each side? I had one only on the flywheel side.
If I can get oil slings of such a thickness that I don't need shims, am I OK?

Sorry but I have not been able to find shims on Ebay (not familiar at all with this site) and our local machinists have nothing.
Saw a laser cutting company but they have only 1mm 1.2mm and 1.5mm steel. Maybe 2x1mm would fit.
do I need stainless steel or regular steel for shims and oil slings?

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #284 on: 04 Dec 2019 at 20:37 »
Are you going to use thin gaskets between the crankcases, as you will need to allow for those too? I used 0.25mm paper.
Heres a link for shims, but there are plenty of others if you search when you know the exact size
https://www.ebay.co.uk/itm/0-5mm-THICK-SHIM-WASHERS-HIGH-QUALITY-STEEL-DIN-988-ALL-SIZES/253287469547?hash=item3af91c11eb:m:mL7tYo9RonYTvbphx9unn2w

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #285 on: 05 Dec 2019 at 13:39 »
Yes paper was installed when I measured.
Thank for the link. When they say M42x52mm, does it means 42mm ID and 52mm OD?
I just need to hear from Doug or Eddie for the play I need to leave. Or I'll go with .004" like you did. However based on the lack of accuracy of m measures, I need to know how tight I need to be. I would have then to have it measured accurately somewhere should I need to be "close" or tight.

Is it better to have 1 shim behind each bearing or is it just not important? I mean better to use 2x0,2mm or 1x0,4mm?
« Last Edit: 05 Dec 2019 at 13:44 by Eric S »

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #286 on: 05 Dec 2019 at 14:52 »
Thats correct, M42 would be the ID in mm, and 52mm the OD
Personally I fitted the shims between the crank & the oil slingers. This meant I didn't have to remove the bearings to alter clearances.
Maybe not perfect engineering but it works.
Using this method its easy to assemble with no shims, check the end float & then add/subtract shims.
I did have to profile the inside of the shims to clear the radius on the crank however & I would suggest using a single shim and not "stacking" them if using this method.

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #287 on: 05 Dec 2019 at 15:11 »
Then did the oil slinger act as a shim?
Do you use oil slingers on both sides?

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #288 on: 05 Dec 2019 at 15:30 »
The oil slingers were 1mm thick & the diameter was just big enough to obscure the ball bearings.
I used one 1mm slinger & one 0.3mm shim on each side of the crank.
This gave me 4 thou clearance. I was aiming for between 4 thou & 8 thou.



Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #289 on: 05 Dec 2019 at 18:13 »
Right now I have 2x1mm 30x52mm oil slingers on the flywheel side.
Bearing "opening" is 52mm so the slinger barely covers the opening. Picture 1

On the link you gave earlier they offer 30x42. So OD is a bit small. Will it work?
The ones from the engine have a rough surface and there is 2. Picture 2
Can I still use them as they are larger or is it better to use a single piece, smooth although smaller?

On the timing side, the bearing is thicker than the shaft it rides so adding an oil slinger would take it off the shaft even more. Picture 3
Is it acceptable?
I can get a 25x35 slinger, with a bearing opening of 47mm !? Is it better than none?

Now inside the timing case, I had a real bad shaped shim/Washer/piece of garbage bent(!) to be roughly 3mm thick. Picture 4
Do I need it? Shaft here is 19mm and I could get a 20x28
How large and how thick I want it??

Now If we can use oil slinger of different thickness, why would one bother with inserting shims behind the bearing(s)? Isn't it more simple to ajust via the slingers?
Which brings me back to the same question, what are the required tolerances as thick shims/washers comes in 0,5mm increments?
Or shoudl I source other more size suited shims and slingers?

Offline Doug

  • Global Moderator
  • ****
  • Join Date: Mar 2004
  • Posts: 3559
  • Location: Pennsylvania, USA
Re: Douglas Aero 1937
« Reply #290 on: 05 Dec 2019 at 18:33 »
Eric,

The oil slingers are factored into the design so an not included as part of the shims per se; same as factoring for the width of the bearings. If manufacturing and tolerance were precise enough there would be no need for shims. The factory would just machine to the required dimensions and on assembly it would have the requisite end float. But Kingswood's overall machining accuracy plus the variables of all the individual tolerances on the components of the crankshaft add up to quite a stack of tolerances which result in too much variation. So they make the bearing pocket too deep, and bring the end  float back to the desired limit with shims.

They did not offer various width slingers to serve as a means to adjust end float. Presumably the traditional method of using standard, commercially available shims and popping the bearing in and out posed no difficulty for them. They were use to doing it every workday. They might even had some sort of fixturing or tooling that allowed them to pre-measure and set the shimming so they only had to install the bearing once.

But it is a thought. You might find it easier to make a custom slinger of the desired thickness rather than dealing with the aggravation of removing and installing the ball bearing from the case. I think this would be preferred to using shims between the slinger and the bearing. As already stated, one thick shim is better than multiples of thinner shims. Also, it can be arranged more reliably with the slinger not to get pinched on the radius of the main journal. (While I was typing this, I see you replied with much the same idea.) You could put the shim between the slinger and the bearing (inner race), but this is bad practice from two points. One, the inner race can rotate or creep on the journal, and you want the shim between two static members. Second, it increases the gap between the slinger and the bearing and one of the purposes of the slinger is to keep any larger, stray metal crumbs from getting into the bearing and causing catastrophic failure. Of course the smaller metal particles have probably already trashed the balls and races, but I believe that was the theory!

I have never seen a published figure for the end float on Douglas engines. You were expected to return to the factory or at least the local Douglas Dealer for that sort of repair. So you have to rely on general values from other engines or publications. That timeless source of information "Tuning for Speed" suggests 0.005" for speed work where the crankshaft does not require positive location (such as for the mesh of bevel gears to drive an ohc.) A maximum given as 0.010". Personally I would aim for about 0.004" as already suggested, just to make sure there is some clearance. While the crankshaft does run hotter, the aluminum crankcase will expand more so the clearance will only increase when the engine warm up. In theory you could aim for zero, as the clearance will increase with temperature, but I would not do so. I suspect the crankshafts whip a bit and that might just side load the bearings even more than usual if there was not some clearance to begin with. It also heats up first before the crankcase. I think 0.010" is just a little too much for a road going engine of the period (unless it is a Scott) so would not settle for anything over 0.008". With reliable measuring, I can usually get it within two thou of what I was aiming for (0.004-0.006") without going bonkers over it.

-Doug



Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #291 on: 06 Dec 2019 at 08:26 »
Thank you Doug,
Aero I don't want you to think I don't believe what you said, you've been quite helpfull so far. I just need to get as much information as I can and understand what I am doing which is quite challenging.

Aero what is the process to "profile the inside of the shims to clear the radius on the crank". Is it a larger ID or a radius on the edge? Do I need a tight fit of slingers/shims on the shaft and then a radius on the edge?

Doug don't we have the slinger rotate and creep on the journal too?

I asked for a quote on laser cut slingers, hopefully it is affordable...
If I input 2 - 1mm slingers in my figures, I come to -0.008"/+0.008" clearance so I definitively have to have the parts measured more accurately.

That leaves the question of this washer on the timing side. Do I need it, how large, how thick?
Aero do you have one on your engine?

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #292 on: 06 Dec 2019 at 13:40 »
Received the quote @ 15 piece without taxes !! I was hoping a bit less.
Anybody might be interested as I think that a multiple order may decrease the price?
Any other option??

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #293 on: 06 Dec 2019 at 14:50 »
Hi Eric, I am by no means an expert on these engines but I've built plenty of others over the years. I too need to ask for advice when its a Douglas peculiarity and as no factory assembly info is available for our engines we really need to share as much knowledge as possible between us.

I had to take a Dremel fitted with a grinding wheel to my shims, and chamfer the inner diameter so it would sit flat against the crank. The oil slingers were already chamfered.

My engine is slightly different to yours on the timing side but there is no washer/slinger fitted to mine in the place you mentioned. There is however a spring retaining washer on the other (outer) side of the timing gear.
« Last Edit: 06 Dec 2019 at 17:38 by Aero »

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #294 on: 06 Dec 2019 at 14:51 »
pic

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #295 on: 06 Dec 2019 at 14:55 »
pic

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #296 on: 07 Dec 2019 at 16:50 »
Thank you Aero
I will check the timing side when I will be reassembling it.
As for the shims, I think I will use a 1mm oil slinger and a 1,5mm on the other side. I will slide in the bearings with no shims and then I can determine easily how much I need and have the 2nd oil slinger surface grind
I will go to a machine shop to have my parts measured (and my calipers checked as one (Chinese) is consistently "less generous" than the other one (Mitutoyo)
I will ask them the cost to have the slinger machine grind so I can see if its reachable.

« Last Edit: 09 Dec 2019 at 13:35 by Eric S »

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #297 on: 09 Dec 2019 at 13:54 »
I will have the oil slingers cut in chrome steel rather than stainless. Seems mor eappropriate and I save 5 per piece.
I finally made some good and consistent measurements. Or at least better than previously.
Will have the slingers cut in 1.2 and 1.5mm which should be fine as it will bring me to -0.001"-+.009". I may be able to adjust a bit by sanding one of the slingers.

As for the slingers, I will have them cut right to the journal diameters for ID and adjust for a smooth fit.
As for OD, I will have them covering half of the external race unless somebody advise otherwise...
Will wait for a couple of days before I order the laser cut just in case somebody want to add something.

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 58
  • Location: Shropshire
Re: Douglas Aero 1937
« Reply #298 on: 09 Dec 2019 at 19:13 »
Eric, it is also possible to alter the crank end play a little by using different thickness of gasket paper between the crankcases.
When I first assembled my engine I had no oil slingers, so just used shims on their own, however when I had to strip my engine down again some months ago due to a crankcase stud pulling out I managed to get hold of some original oil slingers & used them in conjunction with shims. Unfortunately I only measured the thickness, and not the outer diameter. All I can say is from memory they just covered the external race enough to obscure the ball race. Sorry I can't be of more help but I didn't take many pics last time.
I'm sure chrome steel is quite adequate for their purpose.

Offline Eric S

  • Senior Member
  • ***
  • Join Date: Dec 2016
  • Posts: 220
  • Location: France
Re: Douglas Aero 1937
« Reply #299 on: 09 Dec 2019 at 19:24 »
I feel that as long as the oil slingers cover most of the balls and do not extend beyond the bearing OD I think it would be large enough...