It has seemed to me that most every car i have worked on went slower in the
morning return run than they qualified and to go with that most went faster in
the late afternoon return runs when they had them. The cars all seemed to not
hook up as well as they did during the day. Possibly the salt is slightly wetter
or drier, or maybe softer or harder. All I have noted is the traction seems
worse in the morning than afternoon. Seems like it is worth a further look
though. The one thing i have also noted in the last 10 years all or most of the
larger streamliners run in the mid to late afternoon. They are the most traction
limited cars out there in my mind. Ok Mayf how do we easily measure the
available traction and hardness. I have 2 ideas. For traction a small weighted
sled with rubber on the bottom and a pull scale. measure the breakaway and
sustaining force to move it along the salt. Then a round metal ball may a few
pounds in weight dropped from a certain height and measure the diameter of the
imprint to measure hardness.. Could also measure the temperature and I am sure
someone would have a way to measure the moisture content at the surface. With
all the traction issues at Bonneville it really has to come down to where the
rubber meets the road for a lot of people. It has always made me a big fan of
slippery light cars that do not have traction issues in the first place.
Dave Dahlgren
Marge and/or Dave Thomssen wrote:
>
> The Hayseed's two-bits worth:
>
> Aero drag and horsepower produced by a gas aspirated engine vary exactly the
> same with change of air density. At zero density aero drag is zero and HP
> is zero. rolling resistance is not affected by air density, so the cars
> (such as streamliners) that have the greater part of their resistance
> brought on by rolling resistance will suffer the worst when air density is
> lowest. If aero drag is lower and HP is lower, rolling resistance is still
> high, so a streamliner benefits from high barometer and low temperature.
> Obviously the engines with oxygen-bearing fuels will not be affected as
> much.
>
> Dave D is quite right when he said that high speeds produce lots of
> rolling resistance. The SAE paper describing the goldenrod calculated
> higher rolling resistance than aero resistance at 400 MPH. All this stuff
> depends on what kind of car you run. When I run a fendered street roadster
> the aero drag is so monstous that rolling resistance is comparatively small,
> so in goes the ballast.
>
> As to dry vs. wet salt: do we know for sure that speeds are slower in the
> morning? If they are, could it be because the running gear (rear end, wheel
> bearings, trans, etc.) are not yet warmed up as much as when you run in the
> afternoon heat? It does seem to be a fact that the salt is wetter in the
> heat of the day and capillary moisture comes to the surface and brings some
> salt with it. Sit still some day and watch the ground and you can see it.
> When you get as old as I am you sit a lot.
>
> Dave the hayseed
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