143MPH 850 MK1 Commando?

Land speed, not airspeed, on 2 wheels..

Apart from drag races & that hi-speed run, was the trick factory 850 circuit raced?

Was that sport spec 850 available ex-factory?

No.
If you've read through all the thread(s) here on the subject ( and there are getting to be many ), somewhere in there it mentions that Dennis Poore wanted to sell a Combat Model 850 - but it couldn't pass noise testing.

So Norton Villiers published Tuning Sheet 1 and Tuning Sheet 2 - to let owners build their own - and could supply as factory bits all the parts required. 4S cam for example, big sprockets, etc etc etc. This was based on the 850 Mk1 factory hotrod that John Baker and Dave Rawlins were sprinting in 1973.

Apart from standing start 1/4 mile and flying 1/4 mile, I've also never seen mention anywhere that any version of the 850 was road raced - maybe Norton Villiers and then NVT finally accepted that road engines do not racing engines make, and did not go down that path with the 850.

The John Player Special road bike with fairing and twin headlamps was described as a sheep in wolfs clothing - a stock standard engine exactly as other models had. Reliability roooles, OK ??

From '76 I ran a motor in my Rickman chassis that came from an ex-Norton employee, with parts from the experimental shop where he worked until made redundant, and parts from the Thruxton race shop. He was intending to use the motor in his own Rickman, which had in it the very motor that Baker and Rawlins had used on the UK strips to set 4 world records. He was expecting this new motor to be faster!

It was an 850, MkIII cases, 89mm MkIII crank, but 750 short stroke head, fully spherical and re-angled big valves from the blank, it was also machined for clearance in the monocoque and to allow a bolt fitting exhaust stub, ports were large at 34mm. Pistons were Omega short stroke domed, but with the piston pins as per standard rods. Compression was low at about 10.25:1, but it push started easily which was obligatory in those days. Cam was simply marked TX and would have been similar to 4S but with slightly wider power. 36mm Mk1 Amals, later MkIIs which started life at 34 but were quickly bored to 36, large bore exhaust to works dimensions. Estimated output, about 80 at the crank, but never tested. It came as a complete kit of parts I had to assemble myself, interesting for a 21 year old with little previous experience, but when we identified that the new coils supplied to me were useless out of teh box we got it flying, based on gearing calcs it pulled 150mph at 6,800 down towards 2nd gear Knickerbrook at Oulton Park!, which in '76 ran all the way from Island without the chicanes there are today, other rider comments supported the speed, nobody passed it in a straight line except on the brakes!

I was told at the time that the pistons were made because Thruxton built a couple of 850s like this to use in events that were not restricted to 750cc, UK Nationals rather than F750 races, and that on a dyno they were very similar at the top end, but had a huge mid range advantage, certainly I ran a 4 speed Manx ratio box with high ratio primary and Commando clutch with few issues, but I suspect they shortened the life of works 5 Speeds!

Interesting post Steve.
Got a pic of your Rickman, or in action ?

Excellent data, cheers guys.

Rohan said:

Interesting post Steve.
Got a pic of your Rickman, or in action ?

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http://www.facebook.com/photo.php?fbid= ... =3&theater

2 pictures here of original incarnation and 2 of the '79 version, all track pictures Cadwell Park, Lincolnshire.

Currently the original frame is back from repair and with the tank maker for a second new tank!, because after getting one made similar to the original I need a shorter and lower one to accomodate me today :roll:

SteveA said:

Estimated output, about 80 at the crank, but never tested.

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This translates to an estimated 65-70 rear wheel horsepower.

Don't know how we could determine the drive train lost but its a constant that don't increase as power on it increases, so I think Nortons only loses about 10 %.
So 80 crank more like 72 rwhp. That should nugde up close to 150 with fairing and no head wind I'd think.

Drive train losses CANNOT be a constant - lotsa older bikes came out over the years with less than 10 bhp engine, and if they lost as much as the bigger bangers then there would be nothing left !!

Commandos claimed 60 bhp, and allowing for marketing claims, put out 42-45 hp at the rear wheel. I have a little Villiers with a claimed 3 hp - if it lost 10 hp in the drivetrain, you'd be going backwards ??

P.S. Do belt drives get more to the back wheel than chain, or vice versa ?

Rohan said:

P.S. Do belt drives get more to the back wheel than chain, or vice versa ?

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In theory a belt primary should get more power to the rear wheel. As well as the saving in reciprocating weight, a belt should be a couple of pounds lighter, you also have no chain tensioner so less friction. As for the final drive, I guess it should be lighter so maybe a little more power.

In the real world I don't know if there is a noticeable difference, I've never ridden a bike with a belt primary or final drive.
Any Buell owners out there?

Webby

I started road riding with a Honda c200, 90cc, 6.5 bhp. It would comfortably do 60mph and managed to touch 70 mph with a tail wind. These were speedo readings, subject to the usual inaccuracies, however it would run down the 70 mph limited freeway and mostly keep up with traffic in the slow lane, so Im confident it was doing 60-65 mph. When I upgraded to the OHC 8 hp Honda Super 90, there were occasions where I would actually pull out into the fast lane and pass one or two slower moving cars!

Glen

Rohan, I goofed up in my lngo. Of course the *percentage* of drive train loss varies greatly with the input power, so what I meant was that a set hp loss is the constant to add to rwhp figures to get sense of crankshaft hp. Ie: say 4 hp to turn drive train to 3000 rpm, the 40 rwhp Cdo implies 44 hp shaft, 100 rwhp implies 104 shaft hp. Jump to smaller scale drive train and it will have a lower constant hp drag no matter what is turning it. Our chains are at least mid 90's efficient and belts upper 90's, though best chains match belts in upper 90's. So most drag is in AMC box till in one-one 4th, then mainly the oil drag/heat.

Alas no one seems to know the ballpark Norton drive train loss to plug into the rwhp, but then neither do the vast majority of motorsports dyno'd so rwhp is what all the bragging rights focuses on. if one hooked an electric motor in place of the crank shaft and measured its watts to turn up to various rpm we'd have our ballpark graphed answer to calibrate shaft to tire values.

hobot said:

Don't know how we could determine the drive train lost but its a constant that don't increase as power on it increases,

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Whether you realize it or not hobot, that is a trick statement. So technically you are correct, drive train losses do not necessarily increase with increased power, but the caveat is for any given rpm. So if a given Commando is making 45hp at the crank at 7,500rpm or increased power of 80hp at the crank at 7,500rpm the drive train loss at that rpm will be about the same.

I used 10hp loss as a general rule of thumb for a standard (primary and secondary chain drive, crunchy gear box and tire loss) Commando (maybe 8hp, maybe 12 hp) and it goes without saying that if someone is quoting 80hp at the crank, it ain't at tick over speed bub but somehwere between wringing the old girl out and frag time....

hobot said:

Rohan, I goofed up in my lngo. Of course the *percentage* of drive train loss varies greatly with the input power,

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You are now peeing down your leg hobot. It's rpm or speed, more than anything else. Power equates to greater loading but speed is the main factor.

I suppose in the days of pyramid building the load/power would have been more of a factor as there really was not much speed until they found that slave blood was a wonderfull lubricant to skid the dimension stones.

Dancer, I've looked it up. If same drive train is used , then same hp drag to turn it to some rpm, regardless of the power plant turning it to same speeds. Same thing as a tire, same drag to turn tire till breaks loose and smokes but tire don't drag any more energy out of a small engine vs a big engine. Drive train is higher percentage of small engine vs big engine out put is all. Big engine may turn the drive train or tire to scrap but that's not same thing as how much friction drive train consumes. So my message remains if we had the watts it takes to turn Norton drive train then same watts would apply to big or small engine.

What is up for discussion is what this 143 mph 850 would show rwhp on roller dyno as hardly anyone has a crank dyno for cycles. I may not get it but I seek good pull up over 150 and not feel anything but the thrust and wind rush.

hobot said:

Dancer, I've looked it up. If same drive train is used , then same hp drag to turn it to some rpm, regardless of the power plant turning it to same speeds.

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Quote your source.

Your understanding seems to be changing and as stated above is not quite accurate.

For a given rpm, higher power equates to greater loads. A factor in power loss for a given rpm is load but for our purposes for the discussion of the Norton Commando in all its forms, in my opinion, load/power (whether it is 45hp or 80hp) for a given rpm can be ignored.

Dances, make is simple on your self, picture just a single chain connecting crank to output, it will be same hp load weather 15 or 150 hp turning it to same rpm. Next picture a cog on crank and a cog on output axle, same drag heat etc if 15 hp or 150 hp turning it to same speed. Put load on chain or cogs to drag 15 hp down or 150 then more heat and wear on the chain or cog loading 150 down, but not significant difference in the loses of drive train itself. I did post my references a while ago and kind of hard to find as one of the deep mysteries and secret analysis of various dyno types and interpretation. If ya think i"m mis-sleading anyone good on you to warn everyone off, but I'm sticking to my story till shown otherwise, then freely adapt to new info and thank ya for it.

Could your Drouin match this subjects 850 performance?

hobot said:

If ya think i"m mis-sleading anyone good on you to warn everyone off,

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Not everyone, only for the sake of the newbys to the list. The rest know better.

hobot said:

but I'm sticking to my story till shown otherwise,

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Story it is and all over the road. :lol: So you quote something, when called out on it, you cannot find the reference.

You have changed your story like a chameleon changes color but it is entertaining.