"06" Lake Gairdner traction

[JackD]

It is kinda like girl friends, you can study them all you want and spend more money
 and time than you have and still not understand them.
 Marry one and only then will you begin to understand.
I suggest you find the people that are going fast and make yours look the same.
 That is how I learned to sail and it worked on more than a few speed records also.
When the Highboy and the wife have been perfected, I will fly a pig overhead with a tow banner to
 announce it.

[edweldon]

I think classic coeficient of friction effects occur to the greatest degree under near ideal conditions (dry, flat salt, no wind, minimal wheel slippage from too much power and a few others).  Under these conditions tire width is less important as tests indicate.  Here you see minimal roostertails.

 But note that most of the really fast cars throw roostertails.  That means they are breaking the surface a lot. So the traction problem gets more like on a dirt track car. Tire width becomes important up to the point where it creates too much air drag.   We're pushing on small walls of salt while we're digging through it.  In this regime a classic coefficient of friction test would likely only be an indicator of other factors which directly effect traction (like soft salt)...
Wanna read more of my rambling?  See the attachment.....better than a sleeping pill
Ed Weldon

[stayt`ie]

So does this mean a wider tire with more footprint won't increase traction since the weight will decrease per square inch of footprint?

i have seen this mistake made many times at the dragstrip , put a wider tyre on, and then scratch your head because the thing went slower ,,,, go get yourself a simple engineering mechanics book and have a read up on friction, the first thing you will learn is that "friction is almost , independant of the area in contact", the second thing is that "friction is proportional to the force that press the surfaces together"... when i first learnt this back in the eighties i decided to put it to the test. was running a turboed bike with an eight inch slick, ran consistant 9.30`s, put a skinny 4" on and hung 50lbs of steel bar either side of the rear wheel, first run 9 flat, say no more ....

[Sumner]

So does this mean a wider tire with more footprint won't increase traction since the weight will decrease per square inch of footprint?

i have seen this mistake made many times at the dragstrip , put a wider tyre on, and then scratch your head because the thing went slower ,,,, go get yourself a simple engineering mechanics book and have a read up on friction, the first thing you will learn is that "friction is almost , independant of the area in contact", the second thing is that "friction is proportional to the force that press the surfaces together"... when i first learnt this back in the eighties i decided to put it to the test. was running a turboed bike with an eight inch slick, ran consistant 9.30`s, put a skinny 4" on and hung 50lbs of steel bar either side of the rear wheel, first run 9 flat, say no more ....

I guess there is a point where too "skinny" won't work even with more weight, like say you went with a tire that was 1" wide.

There are a lot of high hp cars running fast speeds on the 4 1/2 inch wide Goodyear tires, so I'm wondering if someone (an engineer or by trial an error) determined that this was a good overall width for us?

I guess it won't matter much to me as that is what I have and like the salt is what I'll have to use.  The only variables you have much say about is the weight you decide to run and hopefully the HP you make.

Interesting stuff and some of it goes against what you would assume to be logical.  Kind of like a teardrop shape.  Looks at first that it would go faster turned around the other way with the small end in front.  Also a lot of body shapes I use to look at and think probably provided good down-force are actually "lifting" bodies.  Some times it is scary to start thinking if I was wrong on all of this what else am I wrong on that I'm sure I'm right about.  That almost sound like something JackD might of said .

I'd better quit ,

Sum

[edweldon]

LSR and the engineer

The engineer comes out of school thinking he is ready to solve any problem with his formulas.  Then some wag asks him how far that tree will bend in a 40 knot wind.   He looks at all the leaves and twigs and sees the real world of engineering.  If at that point he says "Lets have a beer"  he's off to a good start.

When a mechanical engineer shows up at the Salt (me, 20 years ago) he quickly realizes some things.
1.  Landspeed racing is highly complex and poorly understood at the engineering level.  The idea of push the pedal down and drive in a straight line for 3,4,5 miles is a deceptively simple one.  Especially at over 200.
2.  There is a reason why engineers are attracted to sports car racing.  The design problems are actually simpler to analyze and build on.  There are fewer variables in the environment and track conditions.  It is much easier to test out your theories on any appropriate stretch of pavement.
3.  There is a lot of "been there, done that, here's how to do it" in landspeed racing that commands high respect.
4.  And, to my liking (I'm an engineer both in reality and at heart) there is virgin technological "country" to be explored.
5.  There's a big gap between the engineer and his preoccupation with numbers and the average land speed racer with his preoccupation with just one number.   I'd like to try and bridge some of that gap.  Perhaps I should learn to be more humble.

So I'll try to put some numbers on this coefficient of friction thing and see if it takes us anywhere worthwhile.
To that end does anyone have the remains of a smooth tread landspeed tire kicking around the shop?  Or maybe first I should ask if anyone has ever tried to dismember a tire with a chop saw?  The idea would be to cut out a piece about a foot long and attach it to a steel test plate of approximately that size.

Ed Weldon

If you want to join the leaders in any human venture the best way is to adopt the best of their wisdom and then try to go them one better??.but for some of us winning is less important than understanding how to win.

[JackD]

If you want to start to learn about AERO shapes on the cheap use water.
Find a HI Speed picture of a single drop of water doing the falling thing in the air we have to share with it.
 It's shape is entirely dictated by the easiest path through whatever it is going through,

[Sumner]

If you want to join the leaders in any human venture the best way is to adopt the best of their wisdom and then try to go them one better??.but for some of us winning is less important than understanding how to win.

I like that quote and the tree example a lot .  I probably quit my attempt at a degree in engineering early as I saw the trees blowing on the U. of Wyo campus a lot.  Now just off campus there were no trees.  They either didn't grow there or had been blown to Nebraska and points east .

Me, I like lots of info available.  I might not use it, believe it or want to hear it, but it is nice to have it there if I decide to look.  I hope you pursue this some and get back to us.

My tires are still good and virgin at this point , so I can't help there,

Sum

[JackD]

A segment of a tire on a test plate of any shape will not simulate the charactoritics of a tire under way.
The best way to begin to figure what they do is to get a photograph of a TF rear at speed
and understand that all tires do it to different degrees.

[maj]

And then factor in the variability of the surface from one point to the next.
Friday at Gairdiner ranged from snow like slush to hard & grippy ,
Wind conditions can vary from mile to mile, its the nature of our sport

[JackD]

"Winds don't blow, they suck. Unless of course if it is a tailwind, that is horsepower.
For example a tail wag often means a cross wind and that sucks.
 Most often the lack of speed is attributed to a head wind that might not even exist.
It also sucks that so many don't understand the effect of the wind and rely so much on Hot Air.
That is not meant to be nasty but the result often is."

[edweldon]

"Winds don't blow, they suck....... so many don't understand the effect of the wind and rely so much on Hot Air.

Interesting you mentioned experience with sailing a couple of posts back.  There's a lot to be learned in that venue about the effects of wind on body moving on a fixed course. When I read on that subject, pretty much all I do with sailing--my "sailboat" is almost laughable, I find lots of surprises.
Ed Weldon

[JackD]

Surprises are best if they are then used as speed secrets.

[Rex Schimmer]

Like Edweldon I am also an engineer both by interest and profession and after 40 years of dicking around in this business and 50 years screwing with cars there is still nothing like experience. I think that the advantage that I may have is that maybe with my background I may have a little better understanding of the thing I learn by experience. I am really looking forwared to the "experience" of building a car for Bonneville and running there and hopefully be able to use some of my technical knowledge to be fast. I agree with Sum (guys that went to the U of Wyo seem to agree on alot!) that you cannot have to much data and information, the trick is to figure out what it all means and how it relates to what you are doing.

Remember when you learn by experience the test comes first and the lesson come afterward!

Rex

[stayt`ie]

i was of the mistaken belief that this coeff. of friction thing would have evolved long ago, given the amount of race  time bonneville has seen since its inception.
i recon that trying to account for all the variables will only muddie the waters (and brain), keep in mind that the figure is going to be a generalization, so lets try and simplify it a little for now,,,, it seems to be accepted that .6 is good salt :  comment anyone,,,     so how would you rate the differance between .2 and .4 :  comment anyone....
(a long time racers concise run  diary sure would help right now)

[JackD]

Unlike most forms of motor sports, the fastest LSR racers keep very little in the way of documentation or a journal.
 It is for the most part a "seat of the pants" type of deal.
 The recent addition of the log book with each entry has mostly to do with streamlining tech.
Many of them have people along that analyze everything to reach a conclusion the successful driver already has.
 They were among the last to use data recording and use it to convince others of the information the driver already has in is head.
"Fraction Control" is really easy to do in many ways but is very distasteful to many to the extent the have severe penalties against it.
 Cheating on that would be so easy but you will find they really don't do it.
In relation to other motor sports , much of LSR is just now being dragged and kicked into the 70s.
Their is great satisfaction for many in beating the highest technology with the lowest.
 Contract projects don't do as well as their PR would have you believe.
 Some top out short of their objective and the more successful are often sand bagging so theY can sell another one later.
Just in the last year their have been some well documented efforts that went home with their tail between their legs and choking on a foot.
 That made them walk a little funny.
It was particularly hard on the engineers.