I was out today with my wife Ann in her BMW Z3 sports car driving through the peak district in Staffordshire - Derbyshire This is a very hilly area When we were overtaken by a learner on his whatever 125 motorcycle ! Well bugger me these can really go up hill he was doing 50 plus and down hill 60 plus What are these new bikes doing my 250 ,s and 350 can only keep up at these speeds Come on guys what am i missing out on Trev
Not sure what bikes you have. An old Honda cbr250rr or any of the 250 4 cylinder sports bikes of that period are quite spritely and enjoyable to ride. If you are just interested in outright performance from a 250 then the 2 stroke pocket rockets are the thing, but they require a bit more maintenance.
My bikes are listed as I can see so are yours This little thing was nothing more than a 125 single but by gum he was giving it some stick ! I really enjoyed watching him go I could tell he was a learner though as he seemed to be ballet dancing on the brake pedal That is according to his brake light I really admire any one who gives it his all possibly getting a 100 miles to the gallon as well Trev
I have always loved the concept of getting a lot out of a little I have even fantasised of getting 100 mph out of a 50 cc machine Fuel injection turbo and a slippy shape I cannot say how much I enjoyed watching the guy getting the max out of the minimum Trev
The 150cc that I owned a while ago was similar fun to run hard. Often tempted to buy another one just for the fun factor. https://2fiftycc.com/index.php?threads/my-latest-new-toy.3625/
Yes. There is real satisfaction out of getting the most out of little bikes. Anyone can go hard on a 1000.
Just buy an NSR 150 if you want to play dragonslayer. In fact, this would be the perfect track day bike, 40hp. Everyone passes you on the straight and you pass them all again before you finish the lap.
there must be some kind of formula for the speed of yer bike against ist horsepower rating taking things like drag etc into account any one have any tables Trev
Only thing which comes close to a formula I can think of is when Barry Sheene was commentating the 500 GP races. He'd always be lauding the speed and power of the Hondas and say that at those speeds each extra horsepower was one extra kilometre per hour by the end of the main straight
Err nope. Wind resistance is the killer. As with everything it will square with the speed so it only takes 40 or a little less to do 100mph and about 200 to do 200mph. After that it gets really crazy. The Ducatis have gobs more power than the Yamahas even though they might only be 12kph faster. You would think a simple comparison would be easily found on the internet of things but not so. Here are some links if you want to mess about https://www.omnicalculator.com/phys.../www.omnicalculator.com/physics/drag-equation http://elmoto.net/showthread.php?t=3400
While wind-resistance (aero-drag) goes up to square of speed, power-required to overcome that resistance goes up by cube-function of speed. So it requires eight times power to just double speed. For example, it requires about 9bhp go push bike through air at 100kph. To make it go 200kph, requires about 70-75bhp.
He's not necessarily disagreeing with Barry, who's not talking about ultimate top-speed given unlimited runway, but acceleration to end of straight. So effects of extra power given extra speed at end of straight isn't as great as would be realised with more road.
Hey, thanks!!! That list of bike cross-sections are very handy! Can plug into this equation to determine how much power is needed to reach any particular speed on any particular bike: TotalPower = aWS + (rho/2)CdCaS^3 where a = coefficient of rolling-resistance of tyres, and drivetrain (bearings & gears) W = weight of bike+rider in Newtons S = speed in meters/second rho = air-density (temperature and elevation dependent, so you'll have to expand on this) Cd = coefficient of drag, depends upon smoothness of body-shapes Ca = frontal-area of bike+rider in square meters, mirrors add surprising amount of area Notice that the 1st term (rolling-resistance) goes up linearly with speed while the 2nd term, power required to overcome wind-drag goes up to the cube-power of speed. When you go from 100 to 300kph, rolling resistance goes up 3x while power-required to overcome wind-resistance goes up by 3*3*3=27x !!! This is why you want to focus on aero-mods to improve top-speed. Easier than increasing gobs of power!
On a push bike you provide all the power. Recumbents are faster because they have less frontal area. Around my local area I can pedal my recumbent trike up to 60kph. Once I fitted a small nose cone that increased to 80kph. I took a Trisled racing trike for a ride around the bike race track. It is fully enclosed with only a few cm of the bottom of the tyres exposed. The track has quite an uphill slope around the back of the circuit. When I got into it my heart sank when I saw that the only front sprocket had 80 teeth. I thought there was no way I would be able to get it up the hill. But when I tried it we just sailed up it really fast. The hill was nothing compared to wind resistance.
I can think of one way to get more power on a bike, but I am uncertain as to the conversion between horsepower and sheeppower or if it's going to go any faster with that wind resistance
I think that has likely never happened, ever! They are worse than trying to play a game of Jenga whilst juggling three pins whilst balancing a plate on a stick on your nose with a hula hoop going on one leg whilst hopping over a skipping rope