Quote:
Originally Posted by bschloop
I think somewhere between .30, and .35 is a pretty good approximation for craig's bike. this is basically a blunt somewhat smooth body with good profile. the open sides act like open windows or wheel wells on a car. only creating a deceptively small amount of turbulence. Allert's would probably fall between .25, and .30, and looks to be quite a bit lighter. Also rolling resistance would be just over half the average for a car. this accounts for higher resistance tires, but half the number of tires. you must also figure that we are not using 100% of our rated output at 70mph. why? we could ride 70 all day without killing our bikes. 100% output will damage an engine after a relatively short period. The most efficient design would use about 60-70% load with the lowest drag possible. also, my bike is rated at 12-14hp new and is 30 years old. I was probably using closer to 10hp on the 70-80mph section, and making it up on the slower parts using closer to 5-6 hp. Craig's bike is rated at 16hp, and could go 70-80mph. this means that either the calculator is wrong, or that Craig's design is better than you give him credit for.
For the record, my frontal area was quite a bit less, but I think my cd is slightly higher.
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OK, this is good. It's always been hard to get any even faintly definitive figures for bikes and of course the problem isn't the bike fairing but the big pimple of a rider sticking out the top of a good looking fairing like the 'Busa. Craig's design solves that although it is possible I'll have to have the rear sections on 2 heavy duty drawer slides to let me get on easily... unless I can get the seat low enough.
Craig, I'll copy very closely but it will be going onto a Royal Enfield fitted with a diesel engine. Diesel will let me burn biodiesel too, the ultimate efficiency. It has to be an Enfield because unless the bike is pre 1970 our local rego boys won't let me modify it.
Calculators ? I'm an engineering kind of bloke and being able to see where the power goes is interesting, it lets me see where the effort is needed.