Would love to hear more about this project Graham,
By all means. It would probably go down better if I continued to put pictures and description into a final PDF, and in the end, that must happen. There is no better place to leave such an "extended manual" than on this site. What we have is the best we could do with the information we had, so there is bound to be stuff which others here could add to, or correct, or just show us a better way to do things. The "diary" PDF has some pictures and descriptions covering perforated rocker cover welding magic, cylinder work, magneto reconstruction and various stuff up to about halfway through the work.
Keeping to the original point for mark1010
, this was about how much of the Douglas T35 stationary engine information was also directly applicable to the T35 bike
. Perhaps some T35 bike owners, seeing this post, can confirm what seems good for the bike also, and maybe point out differences. Everything to do with the gearbox, frame, and all parts of the bike beyond the crankcase are not really things we can help on, and there are probably places elsewhere in the forum where T35 info has been posted in the past.
This engine rebuild has taken me into many deep and dark Douglas places. Douglas had an order for more than 25,000 T35 engines, not including motorcycles. I think the wartime dispatch riders were given BSA, Triumph, and their favourite was Norton, but there were some Douglas also. The cylinders and heads were of a high grade nickel iron, though still prone to rust. The quality of the castings could have been better, but it was wartime, and they were in a hurry. Post war build quality had a problem, a curious mix of near military spec. and excellence, and stuff that should not have been allowed. The bike did look really good, but was under powered. The Dragonfly, (also under powered) was a sensation when shown off, by Douglas did not have the resources to make a good go of it.
We discover that the valves are made of the same special valve steel used for the Rolls-Royce Merlin. KE965 special Austenitic nickel-chrome steel developed by Kayser, Ellison & Co. Ltd. in Carlisle does not air harden under any conditions!
KE965's maximum tensile stress is 17.2 tons per sq.in while it is glowing hot at 900C. That would be bright orange-yellow, and it rings if you whack it. 5 hours glowing somewhat brighter than that at 1000C in exhaust gases still shows no loss of weight. It just does not distort. It is also not made any more. I guess technology moves on, and valve steels are even better now.
Interesting then how one finds the heat, and the constant smacking turns some of the austenite to martinsite in the poppets of the exhaust valves, with only the top of the stems also showing some slight magnetising properties. This does not happen to the inlet valves. This property is not to be confused with valves that have magnetic stems made of different material friction-welded onto stainless poppets.
The KLG spark plugs also, are shared with the RR Merlin. The ignition leads and plugs are fully shielded, to stop interference to radio kit that the machine was undoubtedly powering at times. The Magneto is BTH MD2 from British Thomson-Houston of Birmingham. The questions are.. are the valves in the T35 bike the very same? Is the bike magneto still the the same? I mention this because lots that I found in the magneto is military build to AEI Aviation specification. (I found the overhaul manual)!
I had an abortive adventure trying to re-use an annealed copper head gasket with my 0.006" tiny copper wire O-ring stuck on it until it became clear the sealing trick uses the machined fillet on the cylinder casting spigot to distort the crisp 90 degree edge of a new copper gasket into a perfect seal. It only happens if the hole in the gasket has exactly the right clearance. The trials of trying to home-brew re-manufacture decent gaskets are a separate story!
Perhaps unwisely, I put the part diary PDF on the site here in this post. it is on the understanding that it is a draft, and is going to change! It was a sort of quick review snapshot of progress at the time. A better pdf would include disassembly and reassembly help, reflecting our experiences, and a load of good engine data. Very likely, content may have to change because of new input from the folk here. I include the a few pictures of gasket making, diamond lapping valve followers without going through the hardening layer, and some other novel bits. Forgive that I am hung up on gaskets. Those exhaust ones are some kind of black high temperature stuff between layers of tough stainless steel. They are darn difficult to cut accurately, (and they cut you back)! In the end, the holes were made to fit the ports exactly by using a Dremmel grinder.
Do not be confused by the color codings on some nuts. Everything is BSF, and some are high tensile. The red lines are marked across the ends of any bolt or fixing that has been properly completed with thread-lock in. There are, of course, lots more pictures and info, but for now, you see a bit of where we are.