Rob North Framed Commando

storm42

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Yes, very much so....

I am interested in the following statement from the article:

....The isolastic mountings were dispensed with, only a damping rubber was retained for the cylinder head steady......

Any idea what was used? Where are the pictures referenced
This is the Minnovation solution Steve, Norvil type head steady with the iso plates removed, the rubbers are in place.

MinnHeadSteady2.jpg
 

SteveA

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This is the Minnovation solution Steve, Norvil type head steady with the iso plates removed, the rubbers are in place.

View attachment 16209
Can probably be traced back to Steve Maney then.... Thanks.

Concept very much like the effort on Chris's Rickman. That motor is mounted like a Commando so a bit more room over the head to frame tubes than I have in my Rickman, which as you know has the motor vertical like an Atlas. and the frame had a for/aft tube and only a very short cross tube.

In the amount of room I have I think I have about done what I could without welding on frame tags. The rubber content on mine is exactly the same as a standard Commando, twp Commando cotton reel rubbers from AN.
 
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I'm not really surprised that your bike was approved, Roger. It's a gorgeous bike, and as long as the standard is "could have been built at the time", it should certainly qualify. That seems to be the standard with some organizations, while others insist someone actually had to have raced a similar bike back in the day. I tend to favor the more relaxed criteria, because it results in a more interesting field of competitors.

One of the more interesting eligibility questions I was involved in was whether the short stroke 750 Commando engine was legal in AHRMA's 750 Sportsman class. The issue centered on whether the engine was a "production street engine". In the end, AHRMA decided that Norton had not sold the Commando with the short stroke engine as a "production" bike, even if it was listed as such in the factory brochures. Even though I was arguing for it's eligibility, and provided the factory documentation to support that view, I think the officials were probably right in disallowing it. We're now pretty sure that Norton never produced more that a handful, if any at all, of such bikes for sale to the public.

Ken
As the Norton shortstroke was available at the time, IMO the system is flawed.
I wonder where they stand on someone entering a 500 MV Agusta?
 
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In Australia, there has been a move towards bringing more modern bikes into historic racing. But anything pre-1982 is probably easier to develop and race. I am probably more technology-minded than most people, but computers on motorcycles don't thrill me much. I still believe there is a long way left to go with development of two-valve four-stroke twins, without going silly. When you race an old bike, your mindset is different. When I was working, I was brought-up with computers and a lot of what I did was cutting-edge. I am quite capable of developing a modern motorcycle to go faster, but how fast do you need to go ? I already race fast enough in corners to scare most people. The most dangerous part of road racing is when you brake from very high speed into a corner after a long straight
Am I missing something? I thought the most dangerous part of motorcycling is when you lean it over to take a corner going right onto the shoulder of the tyres or is it just me?
 
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Sounds good. In Australia, if the rules have two syllables we have a major problem.
I have always thought the vertical twin four-stroke motor is a long way from fully developed. I'd even bet the Kenny Dreer motor did not have it's ultimate race cam and exhaust system. It takes a lot of racing to get the best out of any motor. I think the 961 would safely rev higher than the early Commando. More revs = more BHP.
Re; " More revs = more BHP."
Maybe, or not quite, more revs from a motor that only produces the same BHP on the same gearing, an extra 1000 revs will if top gear ratio is 10 mph to 1000 revs make the bike 10 mph faster, or thereabouts.
 
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storm42

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Can probably be traced back to Steve Maney then.... Thanks.

Concept very much like the effort on Chris's Rickman. That motor is mounted like a Commando so a bit more room over the head to frame tubes than I have in my Rickman, which as you know has the motor vertical like an Atlas. and the frame had a for/aft tube and only a very short cross tube.

In the amount of room I have I think I have about done what I could without welding on frame tags. The rubber content on mine is exactly the same as a standard Commando, twp Commando cotton reel rubbers from AN.
I have considered not having a top mount, are they actually necessary? would it be correct to say all the vibration of any consequence is happening around the crank cases?

I could see a solid brace adding to the frame stiffness but, once the top is rubber mounted that extra stiffness is gone, maybe.
 

Fast Eddie

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I have considered not having a top mount, are they actually necessary? would it be correct to say all the vibration of any consequence is happening around the crank cases?

I could see a solid brace adding to the frame stiffness but, once the top is rubber mounted that extra stiffness is gone, maybe.
My thoughts also...
 

MichaelB

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Kenny Dreer installed an Iso on the bottom of the cradle as a fourth Iso on his VR880's.
Dubbed it Quadralastic.
He was so pleased with the results he eventually removed the top Iso. Wasn't necessary anymore
The head is now stress free.
That's how most VR880's went out.
 
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Why add weight and complications when you can just reduce the vibration at the source?
BTW - Kenny Dreer got in touch with me a few years ago about the lightweight pistons and bushless rods - but it was too late.
 
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Am I missing something? I thought the most dangerous part of motorcycling is when you lean it over to take a corner going right onto the shoulder of the tyres or is it just me?
That is a simple-minded approach to the process. It assumes that all motorcycles are the same. If they are, then you simply join the procession in corners,. But if your bike is set up to oversteer when you gas it, it stays more vertical and can power through the corners taking a tighter line. It is not easy to get a bike to do this and most road bikes are set up to handle neutrally. So tend to run wide in corners as you gas them. That is when you become totally tyre dependent. Coming down from high speed into a corner using a drum brake can b a nightmare. It is far more dangerous that losing the rear in a corner when you are at full lean. Dropping a bike in a corner is not the end of the world , because the speeds are relatively low. I've had about three get-offs at around 100 MPH when braking - I don't like that.
 
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When you see a top rider blitzing everybody else, you might believe they have superior skill. But you usually haven't ridden their motorcycle. I once asked Ken Blake how he could go so fast on the Dean Jesser Triton. He said 'it is just the bike, you can do anything with it'. If my Seeley 850 had 20 more horsepower, it would probably kill me very quickly. When I ride it, my head needs to be around the next corner before I get there. You can't have that with a bike which is super-quick.
John Kocinsky had it with the Honda RC45 Superbike and won a lot of races by powering through the corners. It would not happen these days., the modern bikes are too fast. - However Commandos are nice and slow.
 
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The other day I was watching a video about Marc Marquez improving his riding techniques. You have to wonder.

 

Chris

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Hi Storm
Not sure about vibration being around the crankcase area. Ran the Mk4 without the head steady & it did for my exhaust pipes in pretty much one weekend.
 

storm42

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Thanks Chris, I suppose there must be vibration at the top as it wouldn't break frames and brackets if there wasn't, but I couldn't see a reason for trying to control it, now I can.
 

storm42

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Just a thought though, didn't the Mk4 hang the motor from the top with no front engine support?
 

SteveA

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Kenny Dreer installed an Iso on the bottom of the cradle as a fourth Iso on his VR880's.
Dubbed it Quadralastic.
He was so pleased with the results he eventually removed the top Iso. Wasn't necessary anymore
The head is now stress free.
That's how most VR880's went out.
That's interesting, but not relevant to a rigid mounted motor! On a Commando as we know, the head steady dynamics affects handling characteristics where the head steady is the only point that mounts the motor to the frame as the other points mount it too the engine/plates/swinging arm assembley. Not so I believe on rigid mounts. Sound like the '4th Iso' mounted the assembly to the frame below the engine rather than above.

So as I understand it what Kenny Dreer did when he removed the head steady was in effect to move the 3rd iso mount!
 
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SteveA

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Just a thought though, didn't the Mk4 hang the motor from the top with no front engine support?

028.JPG


Chris' John Caffrey MkIV Seeley framed bike had a head steady!

But on the 'no head steady topic'. Of course that is an option to be considered. I did, but emotionally felt better with my rubber bobbins....

However, a number of Norton powered sidecar outfits don't have a head steady, mainly because their chassis designs don't have anything within close enough clamping distance to make it worthwhile!
 
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storm42

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Hi Storm
Not sure about vibration being around the crankcase area. Ran the Mk4 without the head steady & it did for my exhaust pipes in pretty much one weekend.
I see from Steves pic that there is a support, but something else has just occurred to me, removing the head steady may introduce more vibes that killed your exhaust but how does the standard Commando make its exhaust last?

I guess that your exhaust was rubber mounted at the rear like mine.
 
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