143MPH 850 MK1 Commando?

Modern 961 Norton Commando Motorcycles

Re: 143MPH 850 MK1 Commando?

Postby Rohan » Wed Aug 29, 2012 2:16 pm

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 ?

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Re: 143MPH 850 MK1 Commando?

Postby Webby03 » Wed Aug 29, 2012 3:39 pm

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


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.
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Re: 143MPH 850 MK1 Commando?

Postby worntorn » Wed Aug 29, 2012 4:14 pm

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!

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Re: 143MPH 850 MK1 Commando?

Postby hobot » Wed Aug 29, 2012 5:30 pm

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.
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Re: 143MPH 850 MK1 Commando?

Postby Dances with Shrapnel » Wed Aug 29, 2012 6:57 pm

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


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....
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Re: 143MPH 850 MK1 Commando?

Postby Dances with Shrapnel » Wed Aug 29, 2012 7:02 pm

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


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.
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Re: 143MPH 850 MK1 Commando?

Postby hobot » Wed Aug 29, 2012 7:51 pm

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.
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Re: 143MPH 850 MK1 Commando?

Postby Dances with Shrapnel » Thu Aug 30, 2012 8:04 am

hobot wrote: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.


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.
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Re: 143MPH 850 MK1 Commando?

Postby hobot » Thu Aug 30, 2012 11:19 am

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?
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Re: 143MPH 850 MK1 Commando?

Postby Dances with Shrapnel » Thu Aug 30, 2012 12:12 pm

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


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

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


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.
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Re: 143MPH 850 MK1 Commando?

Postby J.A.W. » Thu Aug 30, 2012 7:45 pm

Hobot is correct, both in his explanation of energy transfer loss factors, & his view re theory, -stick with it until proven otherwise, if any sound data emerges to dis-prove so be it...

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Re: 143MPH 850 MK1 Commando?

Postby Snorton74 » Thu Aug 30, 2012 7:53 pm

Ditto.
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Re: 143MPH 850 MK1 Commando?

Postby J.A.W. » Thu Aug 30, 2012 8:58 pm

From Classic Bike, Feb `06, P.28, Re `74 J.P.N. Racers;
"Sometimes raced with short-stroke & 850cc engines."

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Re: 143MPH 850 MK1 Commando?

Postby SteveA » Fri Aug 31, 2012 1:42 am

SteveA wrote:
Rohan wrote:Interesting post Steve.
Got a pic of your Rickman, or in action ?


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

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Re: 143MPH 850 MK1 Commando?

Postby Dances with Shrapnel » Fri Aug 31, 2012 8:48 am

J.A.W. wrote:Hobot is correct, both in his explanation of energy transfer loss factors, & his view re theory, -stick with it until proven otherwise, if any sound data emerges to dis-prove so be it...

hobot wrote:Of course the *percentage* of drive train loss varies greatly with the input power

yet
hobot wrote:Don't know how we could determine the drive train lost but its a constant that don't increase as power on it increasesso

and
hobot wrote: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.

so
hobot wrote:so I think Nortons only loses about 10 %

I think there are enough words quoted above that if you rearrange a few of them you get the facts. I see your point :roll:
And if someone represents something as accurate or as fact or tries to build credibility by stating:
hobot wrote: I've looked it up.

and someone calls them on it...........

My other point is that through all the diatribe I think hobot came around to an understanding; it just took several posts and iterations.
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