Author Topic: Barr and Stroud mystery bike  (Read 612 times)

Offline R

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Re: Barr and Stroud mystery bike
« Reply #15 on: April 13, 2018, 03:54:36 AM »
Not much B&S content here, but we've followed along behind a little Daimler Knight on a veterans rally, and it ran along very nicely and smokelessly. Chatting about it afterwards, he said he'd modified it, I think with something somehow related to a Suzuki (port timings ?) and used (smokeless) modern 2 stroke oil. We waz imprezzed !

No need to remind folks that there was some very big and powerful sleeve valve aero engines to come out of WW2. Its amazing how little mechanical noise there is with no valve gear thrashing about - which operationally gave some of them a considerable advantage.

Offline JFerg

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Re: Barr and Stroud mystery bike
« Reply #16 on: April 13, 2018, 08:21:34 AM »
There are sleeve valves and sleeve valves.

Knight and Minerva used two sleeves reciprocating with the piston in the middle.  The ports are small, like letterbox slots, and the wear is concentrated. 

B&S, Bristol, Napier and RR used single sleeves where the action is an elliptical path, with large ports, rapid openings, and good spread of lubricant which also spread the wear over a very large area.   The single sleeve aero engines were the most powerful spark ignition engines ever built, rendered obsolete by jet turbines.  Where poppet vale aero engines generally had a 500 hour service life, the single sleeve valve engines had a 1500 hour interval.  If single sleeve valves had anywhere near the gazillions of engineer-hours applied to them that poppet valves have had, there's be a lot more about.

I owe you an apology, Leon.  I've been severely tangled in life and other issues of late, and not had the chance to properly study the extracts you sent me.  I will get there, come May I will have shed a major workload.

Thank you for your Herald research.  As 33d6 suspects, I can postulate the engine number of this machine.  Norm Maplestone bought two B&S V twins.  He also reputedly had a shop in Kew, next to Mont Albert.  Tantalising.

That Czech bike is probably a "Kopra", too.

JFerg

Offline 33d6

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Re: Barr and Stroud mystery bike
« Reply #17 on: April 13, 2018, 08:35:03 AM »
Having explored the innards of one of JFergs B&S engines in company with him I can't really see how one could say they were difficult to get the port timing right but I'd certainly agree that just because you know how a cam operates to push open an inlet or exhaust valve doesn't mean you totally and fully understand the sleeve valve at first glance. It does require some degree of thought and some people find thinking very tricky.
I also think you can't really compare a double sleeve valve engine like the Knight to a single sleeve valve engine like the B&S. In one move the single sleeve valve reduces engine complexity by half thus markedly reducing any tendency for the famed sleeve valve smoking and excessive oil use. You have to remember the great majority if not all smoking sleeve valve stories all relate to double sleeve valve engines.  B&S motorcycle engines have exactly the same total loss oiling system as every other motorcycle engine of their day and use no more nor no less oil than any other and smoke no more nor no less than any other.

And yes, R, two stroke oil is very good in sleeve valves as JFerg will confirm. His is well pleased with it.

It's a pity the sleeve valve engine didn't receive a fraction of the effort and development as the 'umble poppet valve but it didn't and we now have a fascinating side story of what could have happened but didn't. It keeps us entertained doesn't it.

Offline JFerg

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Re: Barr and Stroud mystery bike
« Reply #18 on: April 14, 2018, 12:08:43 AM »
You're obviously in Melbourne, John, as are 33d6 and myself.
I have a couple of 500cc B&S engines, one of which is going.  If you're interested, drop me a line johnferguson@iinet.net.au

JFerg