DOHC Commando (2016)

The engine I was talking about looked absolutely stock Atlas except for the cylinder head. I did the tests in about July 1967 at Wolverhampton. I emigrated to the US in July 1968.

Totally agree. As someone that is involved with engine parts manufacture and tooling to make said parts, a mass produced DOHC or 8 Valve head would cost a fortune to enable enough volume to be made to cost out the tooling. Tooling costs of £15k for a mechanical operated gravity fed casting die are the going rate - that is just one part. As for old style floor standing dies, many companies turn these away as they need 3 or 4 operatives for the casting run. To manufacture a whole engine from fresh, you would need to have or be confident in selling thousands of them.

Two or three times a week I get calls from those who need a part as they know I could get them made, when I mention the cost and the minimum quantity it is a non starter, I'm not talking large numbers 20 or so units would be possible to get machined, but these twenty would still not sold in 20 years time.

Many baulk at the cost of a fullauto head, considering the number of chambers, cores etc involved and then the subsequent machining the price is pretty good.
Each day I talk to many aspiring engineers who would love to make new items, but the risk / cost balance is not worth it. With CAD packages the design is easy, getting from software to finished part is the hard part, then you have to ensure it will out perform what it replaces or achieves or exceeds the expected benefits calculated at the design stage.

acotrel said:

What I was on about has more to do with the way our creativity is being stifled these days by the rules we impose on ourselves. To my mind, it would be possible to build a very good DOHC Commando, however what would we use it for ? It could be the 750cc equivalent of the 500cc Paton. Perhaps if we changed away from historic racing and more towards retro and improved historics, there would be more opportunity for creativity ?

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Triumph has tried that for quite a few years now and recently they threw in the towel on mid-displacement air-cooled twins and came out with a liquid-cooled 1200cc ohc twin. There's no replacement for displacement.

Alan, if you are thinking Nortons and DOHC and creativity, you should be looking at Manx Nortons. !

DESIGNED as a pukka racing iron from the ground up, they have come out as 250 and 600cc, 4 valve and desmo versions,
and 90 bore and larger, and ultra short strokes, and lowboy frames, and even fool injection.
Although not all thse variants are acceptable to some racing classes....

??

I could see 8 valves being an upgrade, but DOHC cannot be fully exploited without a lot more RPM than a Norton engine can tolerate. So without going to a very short stroke to reduce piston speed and some major strengthening of the crankcase, a DOHC Norton is fantasy.

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RIGHT . :wink:

http://www.odd-bike.com/2013/02/norton- ... -last.html

"Two cylinders of a Cosworth dohc shouldn't be hard to do, should it".
"Naaaa, have it running in a couple of weeks...."

8)

So, what did the Cosworth represent, apart from a motorcycle engine designed by car people in a far too big package?

Matt Spencer said:

I could see 8 valves being an upgrade, but DOHC cannot be fully exploited without a lot more RPM than a Norton engine can tolerate. So without going to a very short stroke to reduce piston speed and some major strengthening of the crankcase, a DOHC Norton is fantasy.

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RIGHT . :wink:

http://www.odd-bike.com/2013/02/norton- ... -last.html

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And so was this, at the time. Had it not had nearly insurmountable reliability issues, (and been a 4-cylinder) and gone into actual serial production, the company might have survived and not had to have been resurrected multiple times.

And much like the Cosworth Vega; crap at the time and coveted now.

"Crap at the time and coveted now".

Excellent! How many bikes does this describe? Quite a few I would suggest.

Yes, that might cover 95% of past motorcycle production.
Good job the scrapyard takes some of them out of circulation...

Fullauto said:

So, what did the Cosworth represent, apart from a motorcycle engine designed by car people in a far too big package?

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An up-to-date British Twin, with watercooling, modern combustion chamber design, dohc,
a crankshaft with many bearings and a gearbox that wasn't based on a prewar design.

And if the car design folks hadn't introduced a few quirky bits,
as the Quantel Racer it was (eventually) quite reliable,
and even enjoyed some race successes....

BUT, part of the weight penalty it had was due to being designed with half an eye on it being a road bike.

I always wanted one, IF it had gone to market....
Alas, one of the IF ONLY stories of Brit motoring.

Does anyone know if Norton p10 or p800 survived the NMM disastrous fire in 2003? If not was it ever restored?