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Commando Top Speed? (2010)

Discussion in 'Norton Commando Motorcycles (Classic)' started by highdesert, Dec 21, 2010.

  1. john robert bould

    john robert bould

    Joined:
    Sep 26, 2009
    Back in the late sixties my mates A10 Rocket would do 140 mph....speed inceasing with more ALE!, from experance with a early jota which would "out poke" a commando ..135 semi prone was my best speedo reading..but i was not the best stream-lined dude...I recon SPEED was real selling power back in the seventie's ..and manufracters played on that.. Frontal resistance /power equal speed...a little guy with tight leathers , and a tail wind..should do well :!: [, quote="pommie john"]

    I agree.
    My race 750 has 36mm Amals 10.5 compression and an Axtell 5S cam. It makes 60bhp at the rear wheel. With the highest gearing I have it's supposed to be 132 MPH at 7000 and I've seen pretty close to 7000 in top which adds up with the above.

    All this talk of 150MPH and even 170 I find very hard to believe. In an aerodynamics textbook I have it says that at 100 MPH if you want to go 5% faster, you need either 5% reduction in drag or 16% increase in power. Think about it, to get from 130MPH (which is a reasonable figure for 70bhp) to 170MPH would take a massive increase in horsepower which is simply not available from a Commando engine.[/quote]
     
  2. daveh

    daveh

    Joined:
    Jan 22, 2008
    Cash — thanks for posting that article — very interesting reading.

    More real world road bike figures — The best figure that Cycle magazine could achieve in 1973 with a well prepared stock 750 Commando was 104.77 mph quarter mile terminal speed and a measured 49.7 hp at the rear wheel. In comparison, a Trident 750 put out 53.4 hp and produced a quarter mile terminal speed of 106 mph. A Z900 Kawasaki churned out over 64 hp, 14 hp more than the Commando, and managed a terminal speed of just over 110 mph. All measured on the same dyno.

    Quarter mile figures are the most realistic for the road, all things considered, along with, for example, 50-70 mph top gear roll-ons.
     
  3. hobot

    hobot

    Joined:
    Oct 19, 2005
  4. hobot

    hobot

    Joined:
    Oct 19, 2005
    Dug up pre-Ms Peel factory Combat 7th day in my hands - at drag strip time trials after mufflers blew off and opened up the power band. My avatar was the 5th trial I never finished d/t tire fold up and wheelie into a throw down injury...

    1000 ft event May 1999, tach showed 25K miles so likely way more by then.
    Fastest that beat me a 1200 race only wheelie bar Sportster @ 127 mph.
    Best reaction time .632 sec, worse .883 sec.
    60 ft ET 1.667 to 2.044 sec
    330 ft ET 5.646 to 5.838 sec
    1/8 mile ET 8.743 to 9.080 sec
    1/8 mile mph 76.23 to 78.61
    1000 ft ET 11.298 to 11.743 sec
    1000 ft mph 80.58 to 87.59

    [​IMG]

    Combat in far lane
    [​IMG]
     
  5. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    I'll second that - Cash, thanks for posting that article.
    Thats a much later update to the circa 1974 article I've got somewhere.
    Which was more a look at what Nortons published as Stage 1 and 2 Tuning Sheets.

    68 hp and 145 mph on a naked Commando.
    Not bad.
    @ 6250 rpm too, that is interesting, they don't try and spin it any faster.

    Imagine what it would do with a full fairing.
    And more ponies like the JPN Racers had.
    160+ mph looks quite achievable....

    Big incease over the usual ~42 hp at the rear wheel.
    Which will do ~125 mph with a 22 tooth gearbox sprocket.
     
  6. john robert bould

    john robert bould

    Joined:
    Sep 26, 2009
    My Honda Blackbird with 165bhp and a state of the art fairing showed 168 mph ..thats 2 1/2 times the power of a Stock Commando! so 150 plus reports are slighty over the top.
     
  7. daveh

    daveh

    Joined:
    Jan 22, 2008
    But, as Seeley 920 posted:

    "In 1972 Peter Williams was speedtrapped at the Highlander in the IOM at 148.8mph....but that was with the "69bhp at crank" motor."
     
  8. pommie john

    pommie john

    Joined:
    Nov 18, 2005

    I'm pretty sure the Highlander is at the end of a very long downhill section where they have been on full throttle for a few miles. It's not indicative of the real top speed of a bike on the flat.
     
  9. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    If you've ever had anything to to do with Isle of Man bikes, you'll know how enormously high geared they are.
    I've seen a Suzi do a demo standing start with Isle of Man gearing, and it was slipping the clutch in first gear for about 150 yards. 1st was said to be equivalent to the usual 4/5th gear (in a 5 speed road box).

    Pommie John, I think your graph is way too pessimistic with speeds.
    An Isle of Man Manx Norton was good for 145 mph with about 50 hp - and full fairing.
    And look at the speeds they and the G50s can do these days.
    Never underestimate the usefullness of a full fairing on speeds ?

    I've been for a spin on a Rickman Honda with 3/4 fairing, and a single cam 750 engine mildly hot-rodded. It easily did 150 mph on the flat with probably 75 hp - and its quite a wide bike and none too aerodynamic ?

    I was part of the speedgun crew on Conrod Straight at Bathurst for the Easter Arai 500 race - the 750 race bikes back then had about 100 to 110 horsepower, and were monowheeling over the humps at ~175-180 mph (280-285 kph).

    Maybe we need to put all these bikes on the same dyno, and find out who is quoting horsepower and who is quoting ponypower ?? I know that a lot of quoted numbers are said to be "flash readings", the highest number they can briefly see, with all accessories stripped off, no alternators, no airboxes or silencing, etc....
     
  10. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    Something else to ponder is that its generally quoted that it takes
    ~10 hp to do 60 mph, and
    ~30 hp to do 100 mph.

    This for a reasonably slim bike and reasonably slim rider, no fairings.....
     
  11. hobot

    hobot

    Joined:
    Oct 19, 2005
    Ain't yet found Normal White's 170 mph article yet but creeping up on it.
    Not top speed but 1/4 mile factory fast speed here

    His site http://www.normanwhite.co.uk/profile.htm
    [​IMG]
     
  12. pommie john

    pommie john

    Joined:
    Nov 18, 2005

    My graph was made with figures from the real world. If you can find figures to refute it I'd be happy to see them. But all the figures I found fit into a trend on the graph and there are no anomalies that suggest it's possible to get to these very high speeds without major horsepower.

    As I said before the Highlander at the TT is at the end of a very long , constant downhill section and is not indicative of a realistic top speed, and Conrod straight is also downhill pretty steep downhill I believe.
     
  13. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    I'm not sure where the "realistic" top speed crept into the conversation - the question was did JPN Racers do 155 mph ?

    Race bikes have to gear for the fastest part of the track so they don't over-rev, so if flat out in top is down a mild hill like Con-rod Straight or off the banking at Daytona, then so be it.

    And if a tuned stock looking Commando with 68 bhp can do 145 mph naked at Elvington airstrip, then a faired JPN Racer with 76 bhp should be able to do a good bit better ?

    The speed recorded at Daytona in 1974 by the JPN Racer is listed as 165 mph, which (presumeably) was not just someones wild guess, so this seems creditable. They were being blown into the weeds by the more powerful opposition, it must be said.....

    What is almost scary is that the sidevalve HD KR Racers, fully faired at Daytona were also capable of +150, now that is some speed out of a sidevalve....
     
  14. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    Maybe we should look at some of the older bikes - that used real horsepower ?

    The Vincent Black Lightning is quoted as 70 bhp, and a top speed of 150 mph.
    Since its bettered that speed at Bonneville, thats a genuine top speed.

    And the Guzzi V8 Racer of the 1950s was quoted as 62 bhp, which fully faired was quoted as +160 mph on some circuits. It was only 500cc, after all...
     
  15. pommie john

    pommie john

    Joined:
    Nov 18, 2005

    Oh, OK. can we count my 49cc Honda moped that did 120 MPH ( off a cliff)
    :D
     
  16. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    Actually, reading further on the Guzzi 500cc V8, the final version (before Guzzi withdrew from racing) was giving 75 bhp at 12,000 rpm.
    And with a full dustbin fairing, was lapping MIRA at 187 mph.
    (A speedbowl, none of this stop/start GP race circuits stuff).

    500cc and 187 MPH....

    What was that about needing big horsepower for big speeds ??
    Or maybe it was stallion horsepower back then, not pony power....

    That was a full dustbin fairing though.
    JPN folks did say the fairing helped..
     
  17. john robert bould

    john robert bould

    Joined:
    Sep 26, 2009
     
  18. Carbonfibre

    Carbonfibre

    Joined:
    Nov 16, 2010
    Like it or not a Commando with a 150mph top speed is going to need around about 105BHP at the rear wheel, and for 170mph its going to need around 130bhp at the wheel. Realistic top speed of these bikes in road going form is about 105mph, with very well prepared fully faired race bikes getting to around 130mph.

    For an accurate idea of some real world figures relating to Commando performance there was a pretty accurate test feature in a recent edition of "Classicbike" magazine, which are not quite as impressive as the silly claims posted in this thread.
     
  19. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    Carbonfibre, you didn't read the scans of the FACTORY hot-rodded Commando 850.

    Dave Rawlins, with a stock looking roadster with 68 bhp, was clocked at Elvington airfield in 1973 and 1974 at 145 MPH. This on a naked Commando, tuned to Stage 2 as the factory called it.

    The JPN Racers are reported as having 76 hp, and with a full fairing were clocked at Daytona at 165 MPH.

    Obviously a Commando doesn't need huge horsepower to do a fair old speed ...

    If a Guzzi 500cc bike with full dustbin fairing and 75 bhp can lap at 187 mph at MIRA, then obviously the aerodynamics can make up for a significant horsepowerr difference.

    Makes you wonder what all these jappa bikes with their big horsepower do with it ??
     
  20. Rohan

    Rohan

    Joined:
    Aug 26, 2010

    105 mph out of a Commando ?
    That is utterly feeble.

    My old 850 Mk1 would cruise at 80 mph with a 21 tooth sprocket, and that was only 2/3 revs. It would do 100+ mph in 3rd gear at 7000 rpm. Didn't actually test it out in 4th, book says it should top out at 120 mph with that sprocket.

    As a racer, this would be laughable....

    Which is why the factory put out the Stage 1 and Stage 2 Tuning Sheets, which upps the horsepower by 50%. And gives you the choice of a 22, 23 or 24 tooth sprocket as well...
     

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