SR3 Drag coefficient
Discussion
LCM said:
splitpin said:
Do you think Radical might know ?????????? 
Don't be silly! Well L, are you joining ROC & attending the Inaugural Trackday?; afterall, your fame precedes you and several people you know already have and are, so howzabout it? Please see the thread Radical Owners Club thread for the Founders contact details and I do know he has been trying to pin you down.
splitpin said:
LCM said:
splitpin said:
Do you think Radical might know ??????????
Don't be silly! Well L, are you joining ROC & attending the Inaugural Trackday?; afterall, your fame precedes you and several people you know already have and are, so howzabout it? Please see the thread Radical Owners Club thread for the Founders contact details and I do know he has been trying to pin you down.
Trackdays are a bit of a problem for me. Firstly, as Angus will tell you, I'm a BIG feardie; secondly, I haven't got any mirrors; thirdly, I can only carry 8 litres max of jungle juice which is enough for about 5 miles; fourthly with all my aero dangles I don't go fast in a straight line (130 at MIRA is the fastest I've ever gone) so would get in everybody'e way (see 2 qv); fifthly, I've only got A15 (or even worse A91) rubber which is totally sh*gged after 2 miles; sixthly, the sun might get in my eyes; seventhly, there's a hole in my mit and I might drop the catch; eighthly, I heard that the Rock was a bit of a Demolition Derby; ninethly, b*gger it I'm out of excuses.......................
OK then, I'll pop along to the ROC thread
Count Johnny said:
Guys
I hate to pop in, like this - and to do so seems pretty pointless given the flip responses - but I think what Simon's actually after is CdA (ie the coefficient of drag as a factor of frontal area).
As Antoine Xavier de St Exupery said "do not disregard the flippant for it often conceals a serious purpose". Except, of course, he said it in FrenchI hate to pop in, like this - and to do so seems pretty pointless given the flip responses - but I think what Simon's actually after is CdA (ie the coefficient of drag as a factor of frontal area).
To be serious for a moment and to indulge in a little arch-pedantry, CdA is the product of the coefficient of drag and frontal area (of which by definition they are factors rather than Cd being a factor of A as you suggest). Frontal area is relatively easy (even if somewhat tedious) to derive if you have the vehicle, whereas the Cd is somewhat more difficult.
Assuming that Radical cannot produce a figure and that Simon has neither ready access to a full size wind tunnel nor full 3-D Navier-Stokes CFD and really, really wants to know the Cd, then a series of coast-down experiments would be the way to go.
If you want to know how to do this, you can either pay an aerodynamic consultant a small ransom or read things like "Test Procedures for the Evaluation of Aerodynamic Drag......" Watson, Buckley and Marks SAE 76-0106 and "Contribution to Accurate Measuremet of Aerodynamic Drag on a Moving Vehicle from Coast-Down Tests" Roussillon G in Journal of Wind Engineering and Industrial Aerodynamics Vol 9, 1981.
Hope this is serious enough....................
LCM said:
Count Johnny said:
Guys
I hate to pop in, like this - and to do so seems pretty pointless given the flip responses - but I think what Simon's actually after is CdA (ie the coefficient of drag as a factor of frontal area).
As Antoine Xavier de St Exupery said "do not disregard the flippant for it often conceals a serious purpose". Except, of course, he said it in FrenchI hate to pop in, like this - and to do so seems pretty pointless given the flip responses - but I think what Simon's actually after is CdA (ie the coefficient of drag as a factor of frontal area).
To be serious for a moment and to indulge in a little arch-pedantry, CdA is the product of the coefficient of drag and frontal area (of which by definition they are factors rather than Cd being a factor of A as you suggest). Frontal area is relatively easy (even if somewhat tedious) to derive if you have the vehicle, whereas the Cd is somewhat more difficult.
Assuming that Radical cannot produce a figure and that Simon has neither ready access to a full size wind tunnel nor full 3-D Navier-Stokes CFD and really, really wants to know the Cd, then a series of coast-down experiments would be the way to go.
If you want to know how to do this, you can either pay an aerodynamic consultant a small ransom or read things like "Test Procedures for the Evaluation of Aerodynamic Drag......" Watson, Buckley and Marks SAE 76-0106 and "Contribution to Accurate Measuremet of Aerodynamic Drag on a Moving Vehicle from Coast-Down Tests" Roussillon G in Journal of Wind Engineering and Industrial Aerodynamics Vol 9, 1981.
Hope this is serious enough....................
Simon, are you trying to plug numbers into your test data to see what your power outputs like?
LCM said:
Count Johnny said:
Guys
I hate to pop in, like this - and to do so seems pretty pointless given the flip responses - but I think what Simon's actually after is CdA (ie the coefficient of drag as a factor of frontal area).
As Antoine Xavier de St Exupery said "do not disregard the flippant for it often conceals a serious purpose". Except, of course, he said it in FrenchI hate to pop in, like this - and to do so seems pretty pointless given the flip responses - but I think what Simon's actually after is CdA (ie the coefficient of drag as a factor of frontal area).
To be serious for a moment and to indulge in a little arch-pedantry, CdA is the product of the coefficient of drag and frontal area (of which by definition they are factors rather than Cd being a factor of A as you suggest). Frontal area is relatively easy (even if somewhat tedious) to derive if you have the vehicle, whereas the Cd is somewhat more difficult.
Assuming that Radical cannot produce a figure and that Simon has neither ready access to a full size wind tunnel nor full 3-D Navier-Stokes CFD and really, really wants to know the Cd, then a series of coast-down experiments would be the way to go.
If you want to know how to do this, you can either pay an aerodynamic consultant a small ransom or read things like "Test Procedures for the Evaluation of Aerodynamic Drag......" Watson, Buckley and Marks SAE 76-0106 and "Contribution to Accurate Measuremet of Aerodynamic Drag on a Moving Vehicle from Coast-Down Tests" Roussillon G in Journal of Wind Engineering and Industrial Aerodynamics Vol 9, 1981.
Hope this is serious enough....................
Ferkin Liberty, some non Radical Bloke rollicking a proper Radical Bloke on the Radical Forum.
You may be able to count, but sure you can spell?
They say what goes around comes around, so as we are accused of flip responses into a very serious question, Err anything you want to tell us chaps?
Luckily, Lindsay you avoided all of this with your Pearls of Technical Wisdom.
Count Johnny said:
LCM said:
As Antoine Xavier de St Exupery said "do not disregard the flippant for it often conceals a serious purpose".
Not in this case, I believe.Blimey!
PS:
For clarity, CdA=CD/Frontal Area
Edited by Count Johnny on Monday 30th March 05:18
which is why it is written that way. Were it, in some perverse alternative universe (with an alternative physics), to be the coefficient divided by the area then it would be written Cd/A.Oh hold on! (and forgive me for being a touch metaphysical here) Were the alternative universe to be that perverse, then we could not rely on Aristotelian logic applying and it could in fact be written anyway you like eg Norman
Anyway, I think that our (hidden) serious purpose (with the possible exception of Angus' hilarious contribution - but perhaps I do him a disservice) was to indicate that Our Friends in the East probably designed the cars without regard to such matters. Indeed, I seem to remember Peter Elleray indicating that he designed the SR9 without the benefit of CFD or wind tunnel, relying instead on first principles, rule of thumb and many years experience of what works and what doesn't
To give you an idea of what Simon might expect and without giving too many secrets away, the lowest drag sports protypes have a Cd around 0.5 and the draggier more like 0.8, some achieve a remarkable L/D ratio of around -6 although most are closer to -3.
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