What is it?

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Fast Eddie said:
I agree. I know PW was not a fan of the engine for race use, but it would have been easy to punch it out to 900cc ish.

A modern 900cc, 8 valve, isolastic mounted twin, in the 1970s… that wudda been awesome !
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180 crank, Slipper clutch......revving to 15000..... Oh! What we could do with modern materials technology!

I think a lot of 1970s Commando purchasers would have hated it!
 
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Danno said:
........ The Challenge was later shown to be a viable racer, but it never made it to production.
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No it wasn't, really it wasn't.

It was a viable Battle of the Twins racer, where the competition was also limited to 2 cylinders. It would not have competed with 4 cylinder 750 2 strokes, ever, even as a 1000cc motor.

Consider how much extra capacity Ducati had to have to compete with 4 cylinder, 4 stroke 750s!
 
SteveA said:
180 crank, Slipper clutch......revving to 15000..... Oh! What we could do with modern materials technology!

I think a lot of 1970s Commando purchasers would have hated it!
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Errr… like I said… road bike… so basically none of the above !

More like, 900cc, 270 crank, normal clutch, sensible revs, isolastic mounted, etc.

I definitely think something like that would have sold.
 
ANIL's ex-MD Nick Hopkins has done some digging with Mick Duckworth who contacted Mick Ofield and Bob Rowley.
Bob Rowley actually remembers riding this lash-up at MIRA with disappointing results.So a prototype it wasn't, just a cut-off section of a Cosworth engine thrown into an existing chassis. I think I shall do a summary in the November "Source".

As for the Cosworth being viable, the unrideability proven by all racers contradicts it. According to Basil Knight, then the JPN race team's draughtsman, he suggested a slipper clutch but Frank Perris didn't want (understand?) the idea. Problem was when the rider shut the throttle the rear wheel stood still. And the rider fell off.

Having ridden nearly all variants of the rotaries I still support the idea of that era to develop the concept. It was brilliant to ride if it lacked the felt "oooomph", and the sound, of the typical Norton twin. Unlike the rotary racers. They most certainly had both in abundance!
Joe S.
 
SteveA said:
No it wasn't, really it wasn't.

It was a viable Battle of the Twins racer, where the competition was also limited to 2 cylinders. It would not have competed with 4 cylinder 750 2 strokes, ever, even as a 1000cc motor.

Consider how much extra capacity Ducati had to have to compete with 4 cylinder, 4 stroke 750s!
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And none of those thousands could compete with a current 600, either, so apples and oranges. The issues were addressed, but by that time, speed and technology had moved on. Honda's V5 GP bike was an overdog and it was banished. But it was the fastest.
 
Danno said:
And none of those thousands could compete with a current 600, either, so apples and oranges. The issues were addressed, but by that time, speed and technology had moved on. Honda's V5 GP bike was an overdog and it was banished. But it was the fastest.
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The Yamaha 700cc TZ750A was raced in 1974, and went to full 750cc in 1975, still delivering apparently 90hp, by '77 the factory were quoting 120hp. The Cosworth, first fielded in 1975 was not going to compete with that, even as a 1000cc motor! It was struggling to remotely deliver on the promise of 90hp, let alone another 30% in 2 years of development. And at the same time the handling deficit was being reduced so the corner speed advantage was being lost too.

It may be worth me pointing out that I raced an 850 Commando engine in a Rickman chassis against 750TZs in 1976 to '79. These were bikes flowed down to club racers like myself, so always a couple or more years behind the factory bikes. My motor was built from parts that escaped Thruxton in '75. And my experience against these bikes was similar to that of Williams and Croxford, I rode around them on the corners, and they flew past on the straights, the best leveller was rain, and even snow....but it was a lottery based on how far the finish line was from the last corner!

2 strokes and 4 strokes will always be an apples and oranges comparison, racers will choose whatever wins within the rules. Many rule changes to inhibit them have proven foolhardy in the face of racer innovation....the 4 cylinder 800cc MotoGP class was one of those foolhardy knee jerks, and failed on pretty much every measure!
 
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For the sake of history etc. I believe the Wankel project actually pre-dates the P86 Cosworth by a few years. I think BSA had a running prototype in the late 60's (albeit with a bought in engine).
 
SteveA said:
The Yamaha 700cc TZ750A was raced in 1974, and went to full 750cc in 1975, still delivering apparently 90hp, by '77 the factory were quoting 120hp. The Cosworth, first fielded in 1975 was not going to compete with that, even as a 1000cc motor! It was struggling to remotely deliver on the promise of 90hp, let alone another 30% in 2 years of development. And at the same time the handling deficit was being reduced so the corner speed advantage was being lost too.

It may be worth me pointing out that I raced an 850 Commando engine in a Rickman chassis against 750TZs in 1976 to '79. These were bikes flowed down to club racers like myself, so always a couple or more years behind the factory bikes. My motor was built from parts that escaped Thruxton in '75. And my experience against these bikes was similar to that of Williams and Croxford, I rode around them on the corners, and they flew past on the straights, the best leveller was rain, and even snow....but it was a lottery based on how far the finish line was from the last corner!

2 strokes and 4 strokes will always be an apples and oranges comparison, racers will choose whatever wins within the rules. Many rule changes to inhibit them have proven foolhardy in the face of racer innovation....the 4 cylinder 800cc MotoGP class was one of those foolhardy knee jerks, and failed on pretty much every measure!
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Again, apples to oranges, 2-stroke to 4, 4 cylinders to 2. I was at Daytona and watched Agostini beat Roberts in 1974. When I said viable racer, I was referring to fair class rules racing, 750cc 4-stroke twin cylinder, non-supercharged motors. Equalization rules, like 50% displacement limits for 2-strokes, 1000cc for twins and 750cc for 4's, weight breaks for pushrods over ohc, whatever, are a bandaid at best to keep current machines and interest, but they never exactly level the playing field, as racing rulebooks are supposed to do. By the time the Challenge was sorted, twins classes were on the way out.

Norton's modern history, like that of the whole Britbike industry, is a series of unfufilled "what-ifs".
 
Danno said:
Again, apples to oranges, 2-stroke to 4, 4 cylinders to 2. I was at Daytona and watched Agostini beat Roberts in 1974. When I said viable racer, I was referring to fair class rules racing, 750cc 4-stroke twin cylinder, non-supercharged motors. Equalization rules, like 50% displacement limits for 2-strokes, 1000cc for twins and 750cc for 4's, weight breaks for pushrods over ohc, whatever, are a bandaid at best to keep current machines and interest, but they never exactly level the playing field, as racing rulebooks are supposed to do. By the time the Challenge was sorted, twins classes were on the way out.

Norton's modern history, like that of the whole Britbike industry, is a series of unfufilled "what-ifs".
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Nothing is fair in love and racing! ;)
 
grandpaul said:
This is one of those bikes that makes me want to see all the relevant people from "back in the day" gather around the bike, and nobody leaves until the facts are determined. Then put the bloody thing to bed with rampant speculation EVERY TIME it's re-posted several thousand times...
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I did, I spoke to Bob Rowley about it, it was a development hack. I took bob round the NMM and it was interesting him telling me about the prototypes and back story.
 
I’ll bet that was interesting. Do you know who bought the hack ?
 
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