BHP measuring

Howard

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You are correct , torque is effort , the push down the road , but power which is torque x RPM is work done , is the factor that allows the bike to develop speed. There is another factor though , power band. Any engine can produce an impressive PEAK power at a given RPM but if that is only a spike a few hundred RPM wide the vehicle is unuseable unless it has a 20 speed gearbox ! Vincents have a wide power band , that is , if the torque and power graphs are examined you would see alot of area under the curve instead of a tall mountain as tends to be the case with modern multi's. This means there is a constant thrust at the drive wheel to develop and maintain velocity.

Yes I'll go along with that, I've never seen the need for more than 4 gears on the Vin, and the Fireblade has 6 - I think - as Mike Hailwood famously said about one of his Hondas - I just keep changing until there are no more.
One minor problem - the Fireblade pulls quite happily from 30 mph in top (2000 rpm), not stunning acceleration, but smooth and far from sluggish.

H
 

Robert Watson

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You are right about the Dyno
Heenan and Froude DXP3 I believe. I have one in my carport, and most of the gear to make it run. We had it mocked up at the 2003 Int Rally with a drive connected to the final drive of a Vin, however they were direct coupled to the crank in the test house. There are pictures floating around that show it. We have toyed with setting it up here and are only lacking the Lightning or Picador engine donation to make it a reality. We even have a 1000 gal water tank standing by. Anyone?

Robert
 

Tom Gaynor

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Power and speed

If 55 bhp gives 125 mph (personally I doubt that many Shadows ever did 125 mph, so I'll settle for 120 mph) then to get 165 mph, you need 165/120 squared, x 55 = 103 bhp. The Vin is naked, the modern bike isn't, so 95 bhp would seem more reasonable for a faired bike. However, from my own experience of publishing power figures on oilfield downhole motors, knowing that drilling "engineers" were uneducated nerds, more testosterone than brains, who were impressed by numbers they didn't understand, bhp became an abbreviation for "brochure horse power". We always looked to see what the opposition were claiming, then fiddled the numbers to get more. A flash reading of 125 on the brake, miraculously survived, became "delivers a reliable 125 bhp". Who would ever know? It's capitalism, baby. Caveat emptor. As many bankers - some, but not enough, busted - would tell you.
The doyen of UK Aermacchi tuners, Dick Linton, quotes an American tuner (sorry, forgotten his name) who said that horsepower sells bikes, but torque wins races, and this is true. When the torque falls off a cliff (on the Manx, about 7200) the speed is still increasing, but now more slowly. Knowing this, I shifted at about 7000, and only let it run (to about 8300) in top. This works. One of the highlights of my racing career was out-accelerating a 55 bhp Gilera four replica on a 50 bhp Norton at about 110 mph. He had the power, but I had the torque IN THE RIGHT PLACE. (Noisewise there's no comparison. I got the full Doppler as I eased past him. Orgasmic.)
I've never put the Vin on a brake, but it would be interesting. Meantime, it goes from 30 to 100 in top, at which point I need to deploy the Vulcan Death Grip to stay on board, and I'm too old for any undignified lying on tanks. Would it do 125 mph? Doubtful, but WTF cares? Not me.
However 103 bhp (and now you know what bhp means) is close enough to a claimed 125 bhp to bear out the rule. The horsepower to reach any speed has a square law relationship with the speed difference, starting from about 36 bhp to see 100 mph on a naked bike.
And if you want to check the veracity of brochure claims, try weighing your Fireblade or whatever. Most of the claimed weights are only true if the bike is without oil, petrol - and crankshaft. Would-be customers are known to look particularly at weight. So lie. Who'll ever know?
Thought for the day: a "cynic" is what an idealist calls a realist.


Tom
 

Howard

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And if you want to check the veracity of brochure claims, try weighing your Fireblade or whatever. Most of the claimed weights are only true if the bike is without oil, petrol - and crankshaft. Would-be customers are known to look particularly at weight. So lie. Who'll ever know?

Tom

You caught me out again. I was curious about the weight claims too, so, the other night, I thought I'd try weighing the two bikes. I put the front wheel of the Egli on the bathroom scales, lots of lcd flashing but no weight! My old analogue spring scales would have weighed it.

H

ps there was no ulterior motive to this thread, just the product of my mind wandering during the boring parts of a rebuild (painting).
 

Albervin

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Tom, you do have a way with words! The Japs are now slowly realising that their weight claims are being questioned. We now have "kerb weight" which is probably a ready to go bike with half a tank of petrol. Look at the weight of a Vincent 1000 & it won't be a million miles from 200Kg. I wonder (or is it wander) at the speeds set 60 years ago with less than 100bhp. There are bikes out there with (supposedly) more power than 1980s BMWs & they are not doing 200 mph?! My 1985 BMW 323i weighed 1200Kg, supposedly generated 125bhp & did a genuine 120 mph ( Officer plod gave me a ticket to prove it). So why won't a 200 kg/125bhp bike do more than 165 mph?:rolleyes: On the other hand my little Aprillia has clocked 110 mph with 50 Japanese horses & weighing 140Kg (plus me).
 

Tnecniv Edipar

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The 323i had considerably more torque & better aero.
I've noticed that contemporary Vincent road tests produced variable performance figures. The probability is , I suspect , that tolerances and quality control of the day were much inferior to today. This also applies to other British makes. Triumph in particular were known for 'exaggerated' performance claims ! Then again , so was Jaguar and many other automotive makers. Harley was a joke !
 

Howard

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The 323i had considerably more torque & better aero.
I've noticed that contemporary Vincent road tests produced variable performance figures. The probability is , I suspect , that tolerances and quality control of the day were much inferior to today. This also applies to other British makes. Triumph in particular were known for 'exaggerated' performance claims ! Then again , so was Jaguar and many other automotive makers. Harley was a joke !

Top Gear did an article not too long ago about 150 mph E Types and Aston Martins from the 60s, and said that only specially prepared cars ever got close to the claimed figures.

H
 

Tnecniv Edipar

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Yes , I saw that episode but I already knew about the 'massaged' press E Type ;) Some of the worst offenders for fantasy power numbers were the American car industry. Fortunately for them , at the time , their customers knew no different.
 

lindie

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you mean it's a real feasibility that the 19 DIN horses my MZ is claiming is a "massaged" figure? but with a combined rider and bike weight approaching 280 kg i've seen 120kph on the speedo with a correlating readout on the tacho.

should i fit a turbo or lose 40 kg?

power figures over here have been a wank for decades as well with companies strangling engines early through the seventies and still claiming the previous models output figures so as not to appear to be de evolving. and with the converse applicable in japan for a long while to adhere to an artificial limit of 280 hp from their cars. yet with newer models weight figures rising and yet acceleration figures getting sharper there had to be some wondrous H.O.G. (not the harley owners group, their passtime with the first two words "hands on") fiddling of figures or plainly detuning for dyno testing/imposed lower rev ceiling.

as long as my rapide is capable of a higher speed than my MZ(in the region of 10 kph higher is all i'll ever really require living over here anyway) and i need to ride 1600 odd miles to legally do that, then the final power output is academic and best left untested. as long as the rockers rock, the valves valve and the connecting rods decide to stay in connection, and i suspect this to be more likely for longer at moderate revs, then the big girls motor will live a fairly unstressed life in my stewardship. but i plan to sample the torque from down low with open taps on a frequent basis. revs kill engines, but it's generally torque that destroys drive components. hope i find a happy medium somewhere.
 
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