GregC
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Boy, this thread took a left turn at Albuquerque [emoji851]
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Boy, this thread took a left turn at Albuquerque [emoji851]
Wy wife wants to ride on back and she is heavy.
Here's an article for you all to read. Probably written by an engineer as it explains some things:
Motorcycle Aerodynamics | Canada Moto Guide
And the article indicates speed (since we're not really addressing velocity) has a cubic relationship to air pressure. But then uses the words "multiple of 3". So not clear on that one.
Horsepower and speed have the squared relationship (twice the speed, 4 times the power). As a rule of thumb that is.
You greatly underestimate the effects of rolling resistance and aerodynamic drag. The motorcycle has a terminal top speed because at that point ALL of the engine's horsepower is used to overcome the mechanical losses (internal heat), rolling resistance and aerodynamic drag, and there is no excess power left to accelerate it. As you speed up between standstill and top speed, more and more power is lost to friction and drag. Air resistance is proportional to velocity squared, if I remember correctly. Twice the speed, four times the drag. Acceleration in top gear vs 1st gear is vastly different due to friction and drag losses.
With an example motorcycle, the engine at WOT and at 6000 RPM puts 50 horsepower to the rear wheel in 1st gear. At WOT and 6000 RPM in 6th gear, it also puts 50 hp to the rear wheel. The gearing change from 1st to 6th that allows the rear wheel to spin faster relative to the engine speed also reduces the rear wheel torque by the same factor, leaving the horsepower number the same. However, in 6th gear, the vehicle is moving faster through the air and over the ground. More power is used to overcome the rolling friction and aerodynamic drag, so the acceleration is less. It's that simple.
If we could find a way to levitate above the ground and ride in a vacuum, yet somehow still propel the vehicle, we wouldn't need to have this friendly, educational discussion.
Down side, you need to carry that air tank in order to keep the motor running...
Now you have me wondering if it would be possible to modify a traditional RICE (reciprocating internal combustion engine) to accept liquid fuel/liquid oxidizer to build a space-bike. I would expect at that point it would be way more efficient to use a traditional LF/LO rocket engine than to try transmitting the power to the wheels.
Or maybe a gas-turbine... I think I've found a new side-project...