Rob North Framed Commando

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HOWEVER...I had overlooked the line “must be of a type built”. In previous times the rule was “must be built from parts available in the period” and I was working on that basis. Which would be fine. BUT if there was no Rob North Commando pre ‘73 (unless anyone knows otherwise) then a Rob North Commando is not “of a type built” so I just got this wrong.


I have a distinct memory of reading a report from Daytona some time in the 70's regarding the 750 triples with a pair of 750 Triumph twins with Rob North frames in the background ; admitidley not Nortons but at least twins if that helps.
Dick Mann won the 1971 Daytona 200 on a BSA triple. If I remember rightly it was a Robb North frame.
John Cooper famously beat G.Agositini on the MV at Mallory Park race of the year, also the Ontario race in Canada on the BSA3.
P.S. someone under race rules claimed the bike for $1500, much to the annoyance of the BSA factory personnel. Wonder what it's worth today?
 
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lcrken

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Plenty of Rob North frames with great results in the '70s, but they were Triumphs and BSAs, not Nortons, so don't count towards eligibility of Rob North Nortons for current vintage race classes with ealry '70s cutoff dates. Mick Hemmings commissioned the frames from Miles Engineering in 1984, based on the Rob North triple frame design, but with changes to the frame design (upper tubes spread, etc.) to accommodate the taller Norton engine. So they are not really reproductions of period frames, which the Triumph triple repro frames that Miles built are. You might argue that someone could have built a similar bike in the '70s by cutting and welding a Rob North triple frame, and adapting a Norton, but I don't think anyone ever built or raced such a bike back then, so it doesn't really qualify.

On the other hand, as others here have pointed out, the rules can sometimes be more flexibly interpreted if you happen to be rich and famous, or an insider or official of the group making the rules, or even if they are just trying to get more bikes racing in a particular class. So it's not impossible that someone with enough influence might be able to race a Rob North Norton as a period bike. I've had some experience with that sort of twisted rule interpretation to favor a club official twice in my own racing experience. That sort of thing does leave a pretty nasty taste in one's mouth. Hey, it's an imperfect world, but the only one we've got, so we just deal with it and carry on.

Ken
 
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'Some things are worth doing simply because they are good things to do'. When I built my Seeley 850, I did it because it was worth doing. I never worried about historic racing eligibility. It is what it is and it is pretty close to authentic. It gets accepted into Period 4 Historic, so I sometimes do that. But there are other places it can be raced, and If I only used it on track ride days, I would still love it. When I built it in about 1978, I never expected it to be so good - so it sat un-raced for 20 years. When I actually did race it, I was very pleasantly surprised. As-built it was almost right.
If you have got the frame - build the bike. What I really like is the effect that a near-genuine classic racer has on the young guys. When I take my bike to a race circuit, they are all over it.
 
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From the photos you have posted, I think a Rob North Commando would really be worth having - regardless of eligibility. You would always be able to use it somewhere.
 
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When John Cooper beat Agostini, wasn't that a 750 beating a 500 ? - Which circuit ? Anybody can be beaten if they are in the wrong place with a bike which does not suit.
 

Fast Eddie

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It was at Mallory Park.

The 500 was a purpose built GP bike. The 750 a road based bike.
 
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It was at Mallory Park.

The 500 was a purpose built GP bike. The 750 a road based bike.
A Rob North triple is also a purpose-built race bike. I watched Ken Blake beat Agostini at the 1976(?) Australian GP at Laverton Airstrip. The guys all thought that was marvellous. Ken was riding the first four cylinder Suzuki 500 two-stroke and Laverton Airstrip was long and straight. I'm much more impressed that Percy Tait ever got near Agostini with that 500cc Triumph shit-heap. I've often wondered what gearbox was in that.
 
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If you have got the frame, aRob North Commando would be an easy build, and you would have the advantage that you could fir a much better gearbox. When you build a race bike there are two things which are critical - the front brake and the gearbox.
 

holtcorseaux

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Just a heads up for anyone interested, I posted today on the Other Nortons forum with pictures and questions about the current status of bikes built with Mick Hemmings Rob North frame kit for Commandos. It's not a Commando, just uses that engine, so I wasn't sure where to post it.

https://www.accessnorton.com/NortonCommando/where-are-the-rob-north-northtons.30270/

Hi all, I found an article about another Rob North Commando. This one not from Hemmings but from Trident M/C. The anonymous builder/ owner is from Liechtenstein. Unfortunately only in German. Nice machine though.


Have a good day,

Martin.
 

Fast Eddie

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A Rob North triple is also a purpose-built race bike.
No it wasn’t Al. It had a purpose built racing frame, largely designed by trial and error by Percy Tate when he used Rob North fabrications to make him a one-off frame for racing as a privateer.

And, of course, it had a road bike engine.

The MV was a purpose built GP racer, designed from scratch by one of the greatest GP outfits of the day.
 

Dommie Nator

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T
No it wasn’t Al. It had a purpose built racing frame, largely designed by trial and error by Percy Tate when he used Rob North fabrications to make him a one-off frame for racing as a privateer.

And, of course, it had a road bike engine.

The MV was a purpose built GP racer, designed from scratch by one of the greatest GP outfits of the day.
That reminds me, I must post what Les Williams wrote on the subject of Percy's 500 that went to the Belgian GP. It wasn't in his book as it never went much beyond his Royal Signals Regiment White Helmet days.
 
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Dommie Nator

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That reminds me, I must post what Les Williams wrote on the subject of Percy's 500 that went to the Belgian GP. It wasn't in his book as it never went much beyond his Royal Signals Regiment White Helmet days.
Part 1 in the Pub.
 
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It was at Mallory Park.

The 500 was a purpose built GP bike. The 750 a road based bike.
All good handling frames are developed by trial and error. Whomever does the most racing usually has the best bike. Agostini's Evolutzione MV3 replicas have his special fork yokes. If you watch that video of him riding around the Nurburgring, you will notice that when he approaches a corner, he is either braking or accelerating. He does not roll for any distance in the middle of corners. There is no reason a Rob North frame cannot be developed to do that by simple adjustment. About the motor - if a 500cc pushrod engined Triumph can get near him, the MV3 is not that fast. A decent 750 should crap on it. A lot of guys believe that horsepower is the be-all and end-all of winning. With Agostini, it is more the handling of the MV. The RG500 Suzukis blew him to the weeds at Laverton. - very few corners and a straight blast. I watched him both at Calder Raceway and Oran Park. Calder is a power circuit - he still won, but at Oran Park he was much faster - more corners.
 
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The MV3 motor would probably only be faster on some circuits than the Percy Tait Triumph because it can rev higher to get more top end power. Horsepower sells motorcycles, but torque wins races. That Triumph must have had a 6 speed close box - hard to find back in those days. Gileras in the 1950s had 7 speed gearboxes.
 
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The Rob North triples apparently had a crank problem. The crank was a forging which was twisted during manufacture to get the offsets. That imposed a limitation when the motor was raced. Theoretically the 750 motor should be able to be revved to over 10,000 RPM. With 6 speeds close ratio, the motor does not need to spin that high. But Triumph boxes are 5 speed.
 

Fast Eddie

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Al, Trident cranks are as strong as they come! In fact, my layman’s understanding is that the forged and twisted method is stronger than billet as the grains of the metal remain in line as they would in a normal forging.

But it is a common mod to add more oil way drilling’s and to lighten them.

As to the rest of your comments Al, I’ll not even respond, other than to say that at the time, Ago on the MV was considered practically unbeatable on UK short circuits. Hence the effect it had when a relatively little known rider beat him.

Simple as that really.
 
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With 6 speeds close ratio, the motor does not need to spin that high. But Triumph boxes are 5 speed.
Hi Al, I don't understand your logic. A rider revs the engine to peak power revs (or a little beyond) in order til obtain maximum power, which equates to maximum speed. I would think the objective is the same, whether the transmission has 5 or 6 speeds? Overall gearing ratio in top gear should be approx. the same. The rev bands are shorter for a 6-speed than a 5-speed, so maybe the torque curve need to be modified somewhat for a 6-speed. Have I missed something?

-Knut
 
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Dick Mann won the 1971 Daytona 200 on a BSA triple. If I remember rightly it was a Robb North frame.
John Cooper famously beat G.Agositini on the MV at Mallory Park race of the year, also the Ontario race in Canada on the BSA3.
P.S. someone under race rules claimed the bike for $1500, much to the annoyance of the BSA factory personnel. Wonder what it's worth today?
The guy who claimed the bike didn't get it. He was fobbed of with another one of the North framed bikes, Steve Brown the mechanic told me .
 

Fullauto

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One brake horsepower in the midrange is worth three in the top end. As true now as then.
 

Roger Middlebrook

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My bike is Period 4 pre Dec 72 approved by Motorcycling Australia. The compliance took into consideration the bike from top to bottom albeit am sure behind closed doors there was two discussions on approving similar to the thread above, the only question they came back with was around a rear disc break. Once I commented that nearly every other Rob North racing in Australia P4 had a disc break, the questions stopped and approval was granted. appears there will always be two sides of an argument for a bike like the RNN for historic pre 72 eligibility, Fast Eddys cut paste from BHR is very closely aligned to MAU historic P4 pre 72 rules.
Rob North frames first recognized as raced in 1969 and available to general public in 1970, Norton engines, AMC gear boxes, triumph wheels,11" rotors, Marchozzi forks all available pre dec 72 so any combination of these could have been assembled and raced in the period. Fact that no one recalls seeing a Norton in a RN frame kit does not mean it was not done. If my bike was a chopper triple and not a hand crafted special would that make it any more eligible ?? I have to wonder.
Fact is I love my bike for what it is, it has been a part of my life for 20 years the dream or racing it in a high profile period 4 historic event in Australia will soon be a reality and one that I most excitedly am looking forward to. :) Apologizes in advance attachment two formats upside down no matter how it s saved outside of this forum.
 

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