D.O.H.C. ? I want one of these

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Fullauto said:
A complex and costly exercise only needed because that particular manufacturer couldn't design a decent cam chain tensioner for, say, about three decades.
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I had a Honda V45 for a few years and overlapping with my first Commando. With relatively few miles I had to have the tensioners replaced. It was not cheap. My mk3 was much more fun.
 
gortnipper said:
Fullauto said:
A complex and costly exercise only needed because that particular manufacturer couldn't design a decent cam chain tensioner for, say, about three decades.
Click to expand...

I had a Honda V45 for a few years and overlapping with my first Commando. With relatively few miles I had to have the tensioners replaced. It was not cheap. My mk3 was much more fun.
Click to expand...


I wasn't going to name names.........
 
frankdamp said:
You really don't want one of those. While I was at N-V there was a program to develop a DOHC version of the 750 engine. The diagrams in the articles posted look a lot like the one we were trying to develop. A couple of development engines were built and dyno-tested.

The big problem was the camshaft chain length. Because the design tried to use the existing push-rod tubes to route the chain to the head, the chain was close to 36" long. There wasn't enough room to put tensioners in to keep the gradually wearing chain in tension and within a few hours of dynamometer running, chain wear reulted in the valve timing going to hell.

If someone wants to do a DOHC versiion of the engine, they need to get the camshaft chain a lot shorter.
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Frank, if you look at the article again, you'll notice that Merlin didn't use a chain for the cams. They used a toothed timing belt, external to the main engine castings, like some of the modern OHC bikes use (Ducati, Rotax, etc.), They didn't seem to have any problems with that arrangement.

Ken
 
Rohan said:
acotrel said:
There has never been a better single cylinder 500cc bike than a manx
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Are we completely ignoring or discarding the Matchy G50 then ??
For about 10 or 15 years (from the 90s ?) it was the bike to beat - finally got some breathing development late in its life.
All the replicas were faster than the manx, by a good deal, for quite a while there.
Recall how Barry Sheene RIP switched from a manx to a G50 in classic racing,
figuring that if you couldn't beat em then join em....
(Yes, we all know the G50 was sohc, goes to prove dohc is not entirely superior at lower revs...)

If we go back a few decades, into the late 40s early1950s, then the Velo KTT and the AJS 7R joined the fray.
Prewar, the Excelsior Manxman and the Rudge 4 valve Ulsters could all whup a manx predecessor on a good day.
And there were OK Supreme lighthouses, Dunelts, Hudsons, AJS cammies, some french oddities etc etc etc.

The manx came out on top only because of an accident of history - Nortons survived, and the rest succumbed... ?
How soon we forget, eh ?
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The only way a G50 is better is that it is cheaper. The other bikes you've mentioned were all inferior to the 1962 manx. A 4 valve Rudge was a convincing argument however the rest did not quite get there. It's a pity that in 1962 the two stroke competition arrived. If the bikes had been in segregated races from then, the development history would have continued for both technologies, and we would probably have seen 4 valve manxes, with all the electronic trickery. Even today the greatest killer of race classes lies in the mixed grid of radically different technologies - it is almost impossible to get good racing that way.
That rotary Norton was a good example of that - good that it was banned.
 
acotrel said:
The only way a G50 is better is that it is cheaper. .
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So if all those superfast G50's could beat a manx every time, the manx was better ??
Cheaper ?? Have you priced one ?

acotrel said:
The other bikes you've mentioned were all inferior to the 1962 manx. .
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So its become a 62 manx now, has it ??

If all those other bikes had continued to become 1962 models,
we can't help wondering where the manx would be in the pecking order.
All those other bikes could often beat a manx ancestor on a good day.
Some of em, even back then, had all their valves contained and lubed internally, which is already a fair step forward...

A Moto3 bike could already give a manx a run for its money - and they are only a 250cc - and technologically restricted to boot...
 
http://www.nationalmotorcyclemuseum.co. ... pe-P10/51/

D.O.H.C. ? I want one of these
 
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