Peter Williams 2015 ?

acotrel said:

I notice the video was uploaded in March 2015 and I wondered if you guys had seen it. I found it interesting, especially when PW mentioned the way the Monocoque Commando steered. I wonder how many guys have tried different offset fork yokes with the standard commando frame ?

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Umm, yes. But, first, which standard Commando frame? My bike has a 750 frame, built (originally) in June/July 1972. When we were rebuilding it in January, 1973, the designers had changed to the 850 frame with more rake angle and more trail had been established and the first prototype parts were available. The thought among the design staff that an 850 frame with the 750 yokes would be not be a good idea but no one had much of an idea of how a 750 frame with 850 yokes would work. So, John Nelson and Alan Sargent (NV Service Dept., and Exp. shop, respectively) suggested that we put a set of 850 yokes on my Commando. So, as soon as it was road-ready, many of the experimental tester came back reporting "it seems to gain a little stability, but I can't find any drawbacks". At this time, it had the production racer tank and seat, so that may be a factor.

As I put some miles on it, I got to like it. It did appear to be more stable in a straight line and over bumps in a turn at road speeds. Then I went from Wolverhampton to the Norton distributorship in California and took my Commando with me and began racing in some "club" events there. I was aware that under racing conditions, I had to adapt a slightly different style, turning in a little earlier, maybe using a bit more force on the clipons; but, overall, it seemed to perform very well. As other people have discussed, it probably fell into the category "great rider wants the responsiveness, ordinary rider wants the stability" -- having worked hard to get up to the level of 'nearly ordinary', it suited me fine.

Then I had the opportunity to ride at Ontario Motor Speedway (California, east of Los Angeles, nothing to do with Canada). It was a track something like Daytona, but with four turns, like Indy, instead of Dayton's Tri-Oval - a BIG Nascar bowl track but motorcycles using a part of the bowl and then an infield twisty-turny section. There was a fairly slow but opening sweeper leading from the end of the infield section onto the apron at the bottom of "Turn 4" of the bowl -- you could get a good drive onto that straightaway; the big banked Turn 4 was just behind you so you had almost all of the length of that start-finish straight. At the end of that straightaway, you had to make the banked turn to the right (like a Nascar car would) but the entry to the infield came quick. In fact, at speed and lots confidence, you could take the whole as almost one corner in top gear; I never heard anyone say they didn't let off a little, but it was a FAST combination turn. Oh, and just as you entered the infield you wanted to be a little over to the right for a little left-hander next on the infield course so that made it a little tighter a turn that it first needed to be.

The first couple of practice laps, I figured how to do this and realized that it was going to take some big boy pants and a strong will to keep the speed up. So, made the decision to try it as fast as seemed possible. So I got the run onto the straight, past the start-finish and on to big banked turn - looked at the tach and I'm pulling 6700 with a 24-tooth sprocket especially fitted for that race (Brian Slark just nodded his head and said "yeah, you're going to need a *big* one for that track"). Everything looked - right speed, right place, all well. So as the banking began to turn, I gave it a weight shift and a bit of handlebar, and it turned in smoothly just as I wanted, breaking down the banking to make that turn into the infield, cutting a tighter arc than the Nascar cars would.

All going well until I got to the final correction to set up that entry to the infield, gave it a slight right turn -- and it wouldn't turn! Or at least it felt as if it wasn't going to. I'm sitting there with a growing lump in my throat, weight to the right, turning right, and it wouldn't go. And suddenly, it felt right to pull backwards on the left handlebar -- "turning left" to go right. And with no hesitation, it bent to the right and an opposite pull (right bar) turned it to the left for the proper entry.

It all came out OK, but it was an attention grabber! So, yes, some people have tried alternative yokes on "stock" Commandos. The decision was made to tell people to not mis-match 750/850 frames and yokes but that was a decision made maybe two years before my Ontario ride.

You should be very careful if you change the fork yokes. It is not so much about stability as it is about self steering as you brake or accelerate. With my bike, I never reverse steer to get it to turn into corners because it is extremely direct. Once I have braked into the corner, I get straight back onto the gas even when I am less than half-way around - the bike does the rest. It is very confidence inspiring. But here is the rub - if your steering geometry is wrong a problem can come from nowhere and bite you. Sometimes it only takes a ripple in the road. So if you are wise, you don't play with fork yokes unless you are confident you can recover if the bike suddenly mishandles.
The 1961 Manx I rode came back on line when I gassed it as it started to run wide. It is the only bike other than my own which I have ridden, which oversteered when I gassed it while cranked over. If your bike does that when you race, you are very much quicker in corners and at the ends of the straights, because you are powering from a much earlier position..

With the Peter Williams Monocoque - the fork yokes for the offset front wheel would have been made to give the same trail as normal yokes. However in anything I have ever read by Peter Williams, he never specifies the rake and trail he used. It is probably the same as was used on 'Wagon-wheels'. It might be worth someone getting access to one of his new bikes and measuring the rake and trail.