600EW

[Clive]

Hi All.
Can anyone tell me the difference in diameter of the flywheel between the 350cc EW and the 600EW, the shaft size appears the same but i would have thought the 600 would have a much larger flywheel .I have a spare 350 EW flywheel which is slightly bigger than the one on my 350EW, is this because every new owner machines the flywheel to get a nice finish before plating.
  This is a long term project that lives under the bench and only comes out as other important parts materialize. At the moment i only have crankcases ,crank ,cylinders and heads one camshaft and cam followers .still need a frame ,gearbox etc is the g/box bigger than the 350EW? perhaps a member can inform me please of all the differances between the two models.
Regards
Clive

[Doug]

Clive,

My '28 600EW has a 9-7/8" flywheel, verses the 8-9/16" you would see on a 350EW. It is not unusual to see this skimmed down a 1/16" or more to remove rust. Yes they both use the same taper. The main difference between the 600 and 350 is a substantially heavier rim and use of a keyway on the taper. And though I have not checked, most of the guts look like they would interchange, once the 350EW switched from the tang drive to the pin drive pressure plate. The one exception is I would think the sprockets would be different, as the 600 could pull a lower primary reduction. Some 350s, like the 1930 H3 for colonial markets, used a heavier, larger diameter flywheel which appears from photographs to be the one for the 600 (not validated.)

There are a lot of differences between 350 and the 600, too many to list in one reply.

The trans is basically the same housing, but the mounting is different. The 600 clamped to the duplex frame tubes right from the start, something the 350 did not adopt till 1927. And even then, the frame tube spacing on the 350 remained narrower, so the housing (and clamp) was never identical. Never checked the internal gear ratios, but pretty sure the 600 had a longer main shaft as the primary chain line would be offset more for the larger engine.

Forward of the seat post the 600 was a duplex frame and the 350 a single loop.

What year is your engine? The 600EW frames did change when they adopted saddle tanks.

-Doug

[Clive]

Hi Doug,
Thanks for all that, The eng No is EH483 so about 1927 . The crank is in poor condition , drive side taper and keyway badly worn ,has been run loose keyway chopped out. i have a spare flywheel 350EW which is a little oversize [no keyway]measures 8 3/4 ins od good taper would that run OK until the proper size turns up?
Regards the worn tapered main shaft a friend in the engineering business thinks he can build the shaft up and re machine the taper and run without the key .what do you think .Works well enough for the lower capacity engine the bigger engine doesn't develop that much extra power , so i am prepared to give it a try .
The G/Box sounds as if it is quite different , not to many came to NZ will have to look harder . I know where there is a duplex frame but the owner is playing hard to get!!!!!
Are the wheel hubs and brakes the same as the 350? As i have spares of those .
Regards
Clive

[Doug]

The tapers I have seen repaired by others with welding or electroplating had all failed in time, though they all were on the more powerful OHV machines. A fatigue crack starts at the top of the taper where the repair stops abruptly. The 600cc SV is not that powerful, but then it uses a smaller series taper that the OHV machines. Another problem with welding, while it held, was the surface was annealed and a little too soft. The plating method used was hard chrome, which unfortunately had a low coefficient of friction. In both cases there was trouble getting the taper to grip really tight, even when lapped in. It may be the flywheel shuffling on the taper added an additional shock load that hastened the crankshaft's demise.

The gearbox you are looking for is a WG prefix, and the frame a PH prefix.

The 600EW used the machined hubs with the taper spline for the brake drum. The brake drum was pressed steel. The 350EW used an all sheet metal hub and the brake drum formed one of the spoke flanges. Later 350s adopted the machined hub, as did nearly all Douglas models up to 1938. The 350s for the colonial market may have got the more robust hubs earlier. All use the 8" brake band and non-spigoted (water excluder) backing plate, though you do have to be mindful of rotation of operation for the band. 

-Doug

-Doug

[Clive]

Thanks Doug,
Much food for thought will keep you posted as we progress along the road to a completed rideable Douglas Motorcycle.
Regards
Clive