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| Thread ID: 33295 | 2003-05-13 02:19:00 | Completely O/T.. Car wheel frictional power loss | Terry Porritt (14) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 143584 | 2003-05-13 09:44:00 | By the way, in the C++ e-mail group I am in, someone asked, How do you calculate the equation of a straight line passing through the points (x1,y1) and (x2,y2) ? Without misleading anyone with any bull I went straight to google and put in "calculate the equation of a straight line passing through the points (x1,y1) and (x2,y2)" and got the answer in seconds, that brought back memories. |
E.ric (351) | ||
| 143585 | 2003-05-13 09:49:00 | Yes Eric, the reference to clockwise wasnt needed, sorry to mislead that way :) It wasnt deliberate, I hadnt thought properly. We used to have a physics graduate apprentice once who thought that a right handed screw would become a left handed one if looked at from the other end. He went into great explanations about parity, we went into great fits of laughter :) |
Terry Porritt (14) | ||
| 143586 | 2003-05-13 10:28:00 | Graham L > I know cycle racers use solid disks to avoid the drag of spokes. I notice that cycle racers are avoiding using the solid disks these days for a number of reasons, one that I remember is that the weight of the solid disk outweighs the benefits of the disk over the spokes... I believe they're now leaning toward using solid (rather than wire) spokes (about 5 or 7 or something). Mike. |
Mike (15) | ||
| 143587 | 2003-05-13 10:33:00 | It would depend on which face of the spoke was "sharper" - some forward facing spokes are more rounded than others - some are rounded towards the rear, some towards the front... and the same goes for rearward facing spokes. It also would depend on what kind of "lift" (would be outward or inward) is caused by the spokes - similar to the lift generated by the rounded forward edge of an airplane wing, or on a Formula One car... Unless this was done with exact matches of forward/rearward/radial spokes for the testing, it'd be near impossible to determine. That's my opinion anyway :) Mike. |
Mike (15) | ||
| 143588 | 2003-05-13 10:36:00 | Ok well since we're all being completely OT (and please note this is my ifrst posting in any OT T): You are travelling in your car at the speed of light (hypothetically of course). What happens when you turn the lights on? |
falvrez (390) | ||
| 143589 | 2003-05-13 10:47:00 | >and please note this is my first posting in any OT Zorro came to mind when I saw the above,what dareing do. >>You are travelling in your car at the speed of light (hypothetically of >>course). What happens when you turn the lights on? Surely this would depend on if your car had spoke wheels. |
Thomas (1820) | ||
| 143590 | 2003-05-13 10:56:00 | Oh dear, we're now going to get into paradoxes, and I havent really kept up with relativity for oh so long. :) Gee, what you have to always remember in relativity is that speeds can only be measured by using a ray of light or radio wave in vacuum that travels to and fro, ie an outward and inward journey together with a clock to time the there and back signal. With the speed of light constant by definition then all paradoxes are resolved in the Special Theory, and so you get the relativistic eqations for addition of velocities. What it boils down to is that the addition of any velocity positive or negative to the velocity of light leaves that velocity unchanged, even if that velocity is the velocity of light: u= (c+v)/(1+vc/c^2) , If v=c, ergo u=c where u=relative velocity, v=a velocity, c=velocity of light QED |
Terry Porritt (14) | ||
| 143591 | 2003-05-13 11:00:00 | Oh Ive forgotten, not only would your length contract to zero, and your mass increase to infinity, but you would also radiate electromagnetic wave etc rather excessively. I think Thomas has the right idea. |
Terry Porritt (14) | ||
| 143592 | 2003-05-13 11:03:00 | with most wheels it won't make any difference (unless your turning a corner or have a strong side wind) as the spokes on most wheels are sheltered from the airflow by the tire. besides most of the drag will be from the tire and wider tires have more drag. |
tweak'e (174) | ||
| 143593 | 2003-05-13 11:15:00 | Er well, that is yet another effect on top of just the wheels rotating, tweake. The wheels act like an inefficient radial fan or compressor. The air is centrifuged radially outwards, it is sucked in near the centre and it leaves at the outer edges of the trim/tires. Then there is also a viscous shear effect, imagine the layer of air next to the wheel rotating with the wheel, then as you get further away the air gets slower and slower until it is at the general surroundings condition The answer I suppose would be to rotate a wheel on a dynamometer and measure the power loss for different designs and shapes of spokes. This must have been done by vehicle designers. |
Terry Porritt (14) | ||
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