JPN Monocoque Specs

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SteveA said:
acotrel said:
From the little I have read about Peter Williams, I think one of his more notable wins was in the wet. Under those conditions a commando-based bike has a distinct advantage. When it rains, we are all back to square one and how the bike puts it's power down is very important. There appears to be two distinct types of bike in road racing - the Ducati on which Hailwood made his successful comeback on the IOM, seems to have been slow handling and it's advantage was probably in the way it handled the high speed bumpy stuff rather than in short high speed blasts.
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So why did Hailwood win on the same bike at Mallory Park?
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For reasons Acotrel has not discussed here.
 
Getting away from the subject, but about Hailwood. In the early 60s Hailwood used to get a lot of flak from the great unwashed, saying that he only won because his Dad bought him the best bikes. So in about 63 or 64 he got a fairly ordinary 350 Manx and entered a race at Silverstone. These were the days when a short, maybe 10 lap race, would involve the first ten finishers all being very close, as in "covered by a blanket". This would be happening pretty well at every meeting all over the country....very exciting and spectacular racing. In the race at Silverstone the first couple of laps Hailwood was in a bunch of maybe 20 riders, all going for it. Then one lap, all of a sudden Hailwood came round with a 100 metre (probably 100 yards, it was the 60s) lead. The next lap 200 metres. He won the race by a good margin, which was unheard of in those days, and most of the flak stopped.
A truly great rider and sadly missed.
cheers
wakeup
 
Re; “by wakeup » Tue Dec 23, 2014 3:28 pm
Somewhere I have a photograph of Croxfords JPN, in two (major) parts, upside down behind the fence at Woodcote, Silverstone/ This was the crash that inspired the lampstand. I will have a search for it..........
cheers
wakeup”

did you ever find those photos :?:
 
wakeup said:
Getting away from the subject, but about Hailwood. In the early 60s Hailwood used to get a lot of flak from the great unwashed, saying that he only won because his Dad bought him the best bikes. So in about 63 or 64 he got a fairly ordinary 350 Manx and entered a race at Silverstone. These were the days when a short, maybe 10 lap race, would involve the first ten finishers all being very close, as in "covered by a blanket". This would be happening pretty well at every meeting all over the country....very exciting and spectacular racing. In the race at Silverstone the first couple of laps Hailwood was in a bunch of maybe 20 riders, all going for it. Then one lap, all of a sudden Hailwood came round with a 100 metre (probably 100 yards, it was the 60s) lead. The next lap 200 metres. He won the race by a good margin, which was unheard of in those days, and most of the flak stopped.
A truly great rider and sadly missed.
cheers
wakeup
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I suggest you don't become a good racer by riding bad bikes. In my own case, all I probably know is how to avoid the crash. Racing is more than that. If I have learned anything about road racing, it is that nothing is cheap. If you are a beginner, buy yourself a bike which is potentially competitive in it's class. Don't do what I did and feed some kind of nostalgia kick. My short stroke Triton went very close to destroying me, it certainly turned me into an instant dud. The Seeley is a world apart but still not a bike for a beginner.
 
Triton Thrasher said:
SteveA said:
acotrel said:
From the little I have read about Peter Williams, I think one of his more notable wins was in the wet. Under those conditions a commando-based bike has a distinct advantage. When it rains, we are all back to square one and how the bike puts it's power down is very important. There appears to be two distinct types of bike in road racing - the Ducati on which Hailwood made his successful comeback on the IOM, seems to have been slow handling and it's advantage was probably in the way it handled the high speed bumpy stuff rather than in short high speed blasts.
Click to expand...

So why did Hailwood win on the same bike at Mallory Park?
Click to expand...

For reasons Acotrel has not discussed here.
Click to expand...

Most of his passing was done coming off the high speed sweeper at the other side of the circuit. It looks brave, however there is no way of knowing how that part of the circuit made the other guys feel on bikes that had different handling.
Last year the Brits and Yanks again came to Phillip Island. Turn one was a worry for them. I think a slow-handling Ducati might be the best bike on which to go around there at full noise. I won't be taking the Seeley there because to get around corners safely, I need to be accelerating. It would be really bad to get halfway around there and run out of steam.
 
Mike the Bike was a Savant on 2 wheels ..... will be a long time before another shows up
Craig
 
Bernhard said:
Re; “by wakeup » Tue Dec 23, 2014 3:28 pm
Somewhere I have a photograph of Croxfords JPN, in two (major) parts, upside down behind the fence at Woodcote, Silverstone/ This was the crash that inspired the lampstand. I will have a search for it..........
cheers
wakeup”

did you ever find those photos :?:
Click to expand...

Sorry I haven't looked. However I will right now!!
cheers
wakeup
 
If you call Mike Hailwood a savant, so are Ago, Redman and Surtees. They all make it look easy. Perhaps some riders get to stage where everything that can happen has happened, so they become supremely confident ? This might mean there is danger for anyone who tries to stay with them. Have a look at Surtees in this level playing field :

https://www.youtube.com/watch?v=GL3Yv_GXnrw
 
And 75 years old at the time...

I watched JS at Mallory Park as a kid. Must have been his last year at MV.
The old guy who was chief corner marhall told me to watch his exit line during practice. Between sessions Joe went out and put a chalk mark on the road (the exit at Gerards) on the line that Surtees had used. He continued to hit the same mark throughout the race too.
 
Well I've found two photos of the Croxford Lamp Stand in the making, apparently I have to jump through some more hoops to get them on here. Problem is I'm away for a few days and the boss is telling me I have to get packed. Sorry about that.
cheers
wakeup
 
acotrel said:
Most of his passing was done coming off the high speed sweeper at the other side of the circuit.
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You have been watching a different video....

https://www.youtube.com/watch?v=0LnNP7mw7XY

And when it comes to Seeleys, you seem to be the only owner in the world who declares his Seeley is dangerous!

I have only ridden one, and even with a known heavy stiction problem in the forks no way was it dangerous, and clearly it could have been better than it was.
 
If you have too much or too little offset on the fork yokes, the Seeley is certainly dangerous. I began racing the Seeley after it had sat around for years. The bike originally had an SFC 750 Laverda motor fitted to it which was quite heavy. It gave a friend of mine worries when he raced it at Sandown. When I got it, I couldn't get the motor, so I fitted the 850 Commando engine which was much lighter. I noticed the fork yokes had a fair bit of offset but didn't think much about it. Another of my friends was the first to race it and he warned me that it had mishandled and nearly crashed him. I thought he must have imagined it, but when I raced it myself , the same ting happened. It stood up under brakes and turned the wrong way, throwing me off-balance. I knew I was gone, so I decided to drop it onto the grass at the side of the circuit. When I turned it on again to get there, it came back under control - that was with TOO MUCH offset. It now has TOO LITTLE offset and it is possible to tie it into a knot when it self-steers. When you race it you have to learn where it is going to go, so you can use it to best advantage. It has not crashed me YET, but it is likely to happen, so I am always ready for it.
If you look at the JPN Monocoque specs, it has 27 deg. rake and 98mm trail. My bike has 27 deg.rake and about 92mm trail - there is almost nothing in it, but it is treacherous. The Monocoque is slightly longer.
 
acotrel said:
If you have too much or too little offset on the fork yokes, the Seeley is certainly dangerous. I began racing the Seeley after it had sat around for years. The bike originally had an SFC 750 Laverda motor fitted to it which was quite heavy. It gave a friend of mine worries when he raced it at Sandown. When I got it, I couldn't get the motor, so I fitted the 850 Commando engine which was much lighter. I noticed the fork yokes had a fair bit of offset but didn't think much about it. Another of my friends was the first to race it and he warned me that it had mishandled and nearly crashed him. I thought he must have imagined it, but when I raced it myself , the same ting happened. It stood up under brakes and turned the wrong way, throwing me off-balance. I knew I was gone, so I decided to drop it onto the grass at the side of the circuit. When I turned it on again to get there, it came back under control - that was with TOO MUCH offset. It now has TOO LITTLE offset and it is possible to tie it into a knot when it self-steers. When you race it you have to learn where it is going to go, so you can use it to best advantage. It has not crashed me YET, but it is likely to happen, so I am always ready for it.
If you look at the JPN Monocoque specs, it has 27 deg. rake and 98mm trail. My bike has 27 deg.rake and about 92mm trail - there is almost nothing in it, but it is treacherous. The Monocoque is slightly longer.
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Why don't you get some proper yokes ... ?
 
For anyone interested, this is a table of typical rake and trail values from vol. one of John Bradley's book on racing motorcycle design and construction. His two volume set is one of my favorite references because of its great detail on the mechanics of construction techniques, as well as an in-depth study of all the design criteria. It's interesting to see the wide variation in rake and trail between the common race bikes that all work quite well on the track. This is clearly not a case of one size fits all.

JPN Monocoque Specs


Wheelbase also has an effect on the stability vs. quick turn-in trade-off.

JPN Monocoque Specs


Ken
 
acotrel said:
If you have too much or too little offset on the fork yokes, the Seeley is certainly dangerous. I began racing the Seeley after it had sat around for years. The bike originally had an SFC 750 Laverda motor fitted to it which was quite heavy. It gave a friend of mine worries when he raced it at Sandown. When I got it, I couldn't get the motor, so I fitted the 850 Commando engine which was much lighter. I noticed the fork yokes had a fair bit of offset but didn't think much about it.......
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You know, whenever I see that avatar picture of yours I think they tyres are too wide, too tall and and too heavy and the rear shocks are too short.....there are a huge number of Seeley's out there with a huge range on engines fitted, but all basically the same geometry, including yoke offset....check for no fractures/weekness inn frame and plates, go for standard Seeley dimentioned yokes, make sure the forks are set up properly with full travel, jack up the back with up to 14" shocks, fit more suitable tyres on no more than WM3 front/WM4 rear, make sure the wacky Seeley swinging arm pivot/footrest mount is properly installed, the rear wheel alignment arrangement is sound and the wheels are in line and fix the real problem....

I was amazed to see Kenny C point out on the wheel weight thread he uses an 80/80 front, now I actually prefer a 90/90 to a 110/80 on most of the bikes I have raced, so I do go in his direction, a 110/80 won't make it dangerous, but it just wont turn the same. And though I do use a 130/70 rear on the Rickman, if I had an issue and a narrow enough rim, I would go 110/80 at least until it was sorted, because they work fine with way more horsepower than you have.

Following the JPN geometry today with very different forks, tyres and rate of turn expectations does not make too much sense, following the vast range of data out there for Seeley's does, there are more in Seeley copies in classic racing today than any other frame design.

(And very few of the riders on them can truly drift 2 wheels at will as Williams could, nor would want to with the tyres they have available. I always had a lot of respect for Croxford, but I also used to think he struggled a bit with a bike designed around Peter.)

On the evidence you provide, ploughing your own furrow seems to end up with you doing just that!
 
Ken,
The tables of rake and trail you have posted don't show any with 27 deg. rake. If you look at the fork yokes on a Featherbed Manx which has 24.5 deg. rake, they have very little offset, yet if you fit the large offset yokes from a garden gate model, the bike is likely to mishandle. I would expect larger fork offset with the steeper rake.
Every time we change the fork yokes, the cost is $500 or thereabouts. When I had the problem, I simply tried using what I already had in my possession and it worked.
Some of the bikes in that table are modern - the theory is different when you are using fat small diameter tyres and trying to prevent the hi-side.
I suggest that if your bike is neutral handling, it should become stable when you brake and tighten it's line as you accelerate. A Manx does that, however my Seeley tightens it's line a lot and that can be used to create an advantage. - Brake a third of the way into corners, then get straight back onto the gas and let the bike find it's own way.
 
acotrel said:
Ken,
The tables of rake and trail you have posted don't show any with 27 deg. rake.
Click to expand...

I suggest that if you look at that table you refer to and you will see a Triumph Trophy 1200 with 27 degrees and a BMW K1100LT with 27 degrees.

I have a fleet of Seeley Mk2's and none of them behave anywhere near what you describe. It sounds like you really need to sort your bike out. Reread SteveA's remarks on tire sizes as I believe he is on to something for you.

When I had my first Mk 2 made by Keith Stephenson in Yorkshire he cautioned me about wide tires on the Seeley as it "would spoil the handling". Sounds a lot like what you have been going on about for a long time now.

I can attest to the tire bit in a way when I first went onto the track with my Commando with 18" Avon Super Venoms. I was expecting a light flick-able bike like with the 19" K81's but no, it was a bit of a pig. But it never behaved anything badly as you describe.

We are here to help you.
 
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