General => Douglas Motorcycles - General Discussion => Topic started by: oily bloke on 22 Dec 2012 at 17:54

Title: EW Crankshaft oilways
Post by: oily bloke on 22 Dec 2012 at 17:54
Hi all,
Having rebuilt my EW over the last 2 years came to run it up for the first time and found the crankshaft was having problems!! I thought at first it was a tight piston but on stripdown both big ends were tight. Peed off or what!!!
The chap who rebuilt the crank has it back and is in the process of re-re furbishing it and hopefully whatever the problem is will be sorted, however, I have a spare Fairly knackered crank and rods and decided to strip it to see what where and how. I have removed the pressed on crankpin races which exposes the oil feeds (thanks to Doug for your earlier post which proved invaluable) which run through the drilling's within. Looking at the outer periphery of the centre web I can see what looks like three screw plugs to blank off the drillways. Two of which are diagonally opposed which provides a route from big end to big end and one which is central and goes to meet the diagonal drilling roughly in the middle of the Webb. This appears to be the feed in via the drilling in the timing side Webb and I assume that the oil is flung internally by centrifugal force to the big ends.
The question is, are these screws or are they plugs hammered in and cross peined. Either way does anyone have any suggestions as to the best/safest way to remove them? Does anyone know how long they are if I have to resort to spark erosion.
I am trying to assist the guy who is rebuilding my crank and to give me a better understanding as to why it failed so soon.
It has been suggested that the oilways on the re-furbed crank are blocked and/or full of carbon preventing adequate oiling of the big ends. Having said that, when I assembled the engine the crankshaft was flooded with oil under light pressure and oil appeared at both ends. The oil pump apears fine and pumps well.
Many thanks.
Title: Re: EW Crankshaft oilways
Post by: eddie on 22 Dec 2012 at 19:27
         Where were your big ends tight? Was it on diameter, or on the end float, or both? I have found with postwar big ends that it is possible to have the rollers fitting too tightly, which then results in the rods screwing themselves up against one of the webs as they rotate. I resort to lapping down the crankpins until the rods will just slide onto them under their own weight. Some of the purists will insist this is too slack - this may be the case under ideal conditions, but our old engines may not be perfectly aligned - and in any case, will flex under load, so some clearance may be required to cater for this. On the postwar engines, 6-8 thou endfloat on the rods seems to be the ideal - the roller bearing big ends can survive with minimal oiling but the sliding surfaces (and the pistons) rely on the big ends passing a greater quantity of oil for proper lubrication.
    From your comments, the oilways in the crank seem to be clear, so the problem is probably that the clearances in the big ends are too tight.
Title: Re: EW Crankshaft oilways
Post by: oily bloke on 22 Dec 2012 at 21:08
Hi Eddie,
The rods were very notchy when turned and appeared slack radialy then went tight. I returned the complete assembly to the crank guy and am awaiting his post mortem. My belief is the rollers acted like a starter clutch and have grabbed and spun the outer race in the rod eye but I am not sure why. The end float was, to my belief, a few thou but I did not measure this before returning it to the builder.
Thanks for your prompt reply Eddie. I wil post any news as it appears as It may help others restoring these great little bikes.
Title: Re: EW Crankshaft oilways
Post by: Doug on 23 Dec 2012 at 03:54

A notch feel is indicative of rollers that have developed flats. Usually from overheating due to lack of oil or insufficient radial clearance. It is not uncommon for the outer race to spin in the connecting rod. Alls sorts of bodges have been seen to try and secure them - punch marks, Loctite, tack welds - but the main problem is insufficient meat to back up the race and the eye stretches and the press fit becomes slack.

I have not had the oil gallery plugs out of an EW crank, but if they are designed like the OHV cranks the the plugs are threaded in until tight and filed flush. I remove them by taking a small steel machine screw nut, centering it over the plug, and welding it through the center hole. Then you have something to get a purchase on to wind them out. They are usually not very tight, especially after the weld cools and contracts.

This will be the opposite impression you will get if you try to drill the center of the plug and tap in an 'easy-out' device. You will wonder how they could ever possibly got the plugs in so tight, but it is the 'easy-out' expanding the plug and making grip the tapped hole incredibly tight. I know, I tried it.

Before thinking of welding on the nut I first tried building up a column of weld on the center of the plug. With patience and a steady hand this will work but it can be a bit of a bother getting a grip on the blog of weld with the pliers. Also if you stray off the center and weld the plug to the surrounding crankshaft you will have even more trouble getting the plug out! Using the hole in the center of the nut as a fence helps prevent that and keeps the weld in the middle of the head of the plug where it belongs, and it is about a hundred times faster. Countersinking the nut a little so you can get the welding electrode closer to the plug is an advantage. It does not take much of a tack weld, but if it does break off you can always get another nut and try again. I used a TIG torch to weld the nut to the plug, and I think it offers the best control to avoid going too far. But I suppose a MIG weld might work also. I would not attempt it with traditional 'stick' electric welding.

You will need to make new plugs, of course. For comparison the plugs on the DT crankshafts are threaded 3/16-27.

Title: Re: EW Crankshaft oilways
Post by: oily bloke on 23 Dec 2012 at 07:30
Thanks to both Doug & Eddie for your comprehensive replies. Without the knowledge base on this forum I doubt I would have got this far.

A bit more info on the crank. When I fitted the complete engine to the bike I flooded the crank with oil, filled the timing case so it came out of the overflow quill. With the plugs out I turned the engine over on starter rollers until oil was returned through the sight glass (I know that the sight glass does not indicate oil to the crank) & started the engine on the kick start. It ran at about 800 revs for ten minutes and promptly stopped. It sounded 'iffey' so I turned the flywheel by hand and it felt tight so stripped it thinking the rebore had been done tight and a piston had nipped but the pistons and bore were fine. Both rods felt notchy so the crank went straight back to the builder. The engine was warm to the touch but not hot and the crank showed no signs of overheating.

I will let you all know what the end result is. Hopefully it will be reclaimable.


Title: Re: EW Crankshaft oilways
Post by: Doug on 03 Feb 2013 at 15:55

I found where I had placed the plugs that I had removed from my DT crankshaft, and took a picture to illustrate my previous post.


In the foreground you can see two where I simply built up on top of the flush plug with a column of weld material. Well not so simple; a bit tricky actually. Remember the threads are only 3/16 of an inch in diameter. One point I forgot to mention previously, it helps to find and center punch the center of the plug. This helps you spot the center of the screw when the welding mask is on and helps the arc from the TIG torch initiate from the center of the plug (from the sharp, raised edge of the prick mark) and not off to one side where it may fuse the plug to the crankshaft.

Behind are some small machine screw nuts that have been fused to the top of the threaded plugs. This is the way to go. The hole in the nut helps confine the weld, though you will need to countersink it to get access down close to the plug. And it gives you something to grab onto to back out the plug.

I do not know if it was the weld contracting the plug, or just the heat loosening the thread, but the threaded plugs removed easily.


[fix typo, 26Jan16, Doug]