Landracing Forum
Tech Information => Technical Discussion => Topic started by: stayt`ie on May 05, 2006, 06:12:23 PM
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this is a question to the u.s. racers and visitors that were at our 06speedweek event,,, " at what surface friction coefficient would you rate our salt this year :?: "
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about the same as wet salt here.... Slippery....
Jon
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yep......similar to Bonneville when wet..........
similar to many entities..........."slippery when wet"........
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yes it was slippery :) , but how slippery? i noted that your bikes didnt run near the speeds that you do on "wet" salt at bonneville, this may have been due to other factors?,, what i am trying to establish here ( what was asked in my initial post) that is, salt friction coefficient #. ok, .6 is the accepted number for good salt, then it can varie all the way down to .2, you fellas have had many years running on various "wet" salt conditions, soooo,,,, "what would you rate our 06 salt at" :?:
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Hi ronnie
there must be a pretty simple way of standardizing the traction coeficient .....a strain guage , a standard weight and a standard surface area of a known compound ( say smooth rubber) would be a reasonably simple way for to get a "feel" for the actual figure....anyone?
or to put it another way , dad how does this work?......does someone out there have a simple explanation of how the C of traction is calculated and how a basic device could be built to give relative readings.
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yes it was slippery :) , but how slippery? i noted that your bikes didnt run near the speeds that you do on "wet" salt at bonneville, this may have been due to other factors?,, what i am trying to establish here ( what was asked in my initial post) that is, salt friction coefficient #. ok, .6 is the accepted number for good salt, then it can varie all the way down to .2, you fellas have had many years running on various "wet" salt conditions, soooo,,,, "what would you rate our 06 salt at" :?:
The friction coeffiecient will even change during the day. What appears to be the same salt at 8 in the morning and 2 in the afternoon is not. I guess you just have to work with what you got when you get to the front of the line :wink: .
c ya, Sum
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that you do sum :) , it can also varie from start to finish at any time of the day.. but this is all part of the generaliziation of the conditions at the time, thus we have a coefficient number that gives us a level/figure of grip/slipperyness ie. traction to work with ...
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Okay, okay, so somebody come up with a repeatable set of test conditions, do your coefficient testing and determine some number, and report both the result of the test and the conditions.
For instance: Test 1: Bonneville Salt Flats, 9 AM, 78 F/12% humidity, sunny all day yesterday, no rain for XX days (months), salt generally described as "good", test made at the four mile: Result was Coeff/ Traction = .63
Test 2: Lake Gairdner, 3 PM, 34 C/8% humidity, partly cloudy today, rain squalls last Monday, salt generally described as "okay but not great", test made at the start line: Result was C/T = .38
All tests performed by dragging a "standard" (brick, old tire, case of diet coke, whatever) weighing "so many pounds/kg" and measuring the resistance in pounds/kg/slugs/whatever and converting by a set factor.
Or whatever -- the idea is to define the conditions enough that the results are at least somewhat repeatable, by defining as many of the variables as possible no matter what they might be at that moment. If we all know what those basic conditions are -- we could all interpret the results.
Yes, of course the conditions vary all over the Salt, and yes, anecdotal reports are very subjective -- so a set of conditions for a test help resolve those conditions into something from which all could benefit.
Okay, let the arrows fly!
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Okay, okay, so somebody come up with a repeatable set of test conditions, do your coefficient testing and determine some number, and report both the result of the test and the conditions.
I nominate that "Seldom Seen Slim" guy 8) , do I hear a second :? ,
Sum
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Why don't you just get in/on it, push or twist the throttle, keep the tire/tires under it and read the time slip?
DW
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I like that Warner
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Why don't you just get in/on it, push or twist the throttle, keep the tire/tires under it and read the time slip?
DW
When you get to the head of the line that is about your only choice, isn't it :) ,
Sum
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I do it Dan's way -- I was just trying to offer a way of quantifying the situation for anyone that does't choose to so do.
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This is a real interesting subject. Engineers like me like to put numbers on things. It might be interesting to run some simple friction coefficient tests and see if there's any correlation with the way the cars run. I think I'll bring my 2000# sherline scale (see attachment) and some smaller ones with me this year and in the meantime think about how to set up some simple tests. Any ideas anyone?
Ed Weldon
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I do it Dan's way -- I was just trying to offer a way of quantifying the situation for anyone that does't choose to so do.
I thought you said we could shoot arrows at you :shock: . Guess we didn't give you enough time to get your vest on :wink: .
(http://www.philohome.com/traction/traction1.jpg)
Well looks like you are out of the woods. This guy already developed the device to measure traction. Only problem is he used 5 different surfaces, but none were salt :cry: . I learned some from his site ( HERE (http://www.philohome.com/traction/traction.htm) ), but some of this still confuses me :? .
One interesting thing was ....increasing wheel number decrease weight per wheel, keeping vehicle traction constant....
. He noted the exception to this is Of course this applies only on a solid, reasonably even ground. More wheels may be needed to spread load on a larger surface (mud, sand...), but to maintain pulling capability as many of them as possible should be driven.
. So does this mean a wider tire with more footprint won't increase traction since the weight will decrease per square inch of footprint?
So when it is all over if you are spinning your tires you need weight and if not you need HP and you are still stuck with the current conditions when it is time to go, so just follow Dan's instructions :P .
c ya, Sum
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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.
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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
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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 :roll: , 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 8) ....
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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 :roll: , 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 8) ....
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 :wink: .
I'd better quit :roll: ,
Sum
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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.
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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,
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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 :D . 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 :lol: .
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 :wink: , so I can't help there,
Sum
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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.
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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
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"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."
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"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
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Surprises are best if they are then used as speed secrets.
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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
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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)
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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.
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.....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.
Usually is humbling for the engineers. But I think at least some of them are learning. I had a nice chat in impound with the young GM engineer supporting the Socal lakester (attachment)at SW last year. Nice guy, had his head on pretty straight. Wish now I'd gotten his pic and made a better note of his name. I think they applied a conservative approach to this particular project. Take a new strong engine technology; pick a class with a soft record (read "little serious competition"); wrap a proven not too radical car design around it; and then ratchet the record up just fast enough to keep the crew and supporters happy. Looks like there's some good management at work here. I wonder if it will continue given the rocky road facing our auto manufacturers.
Ed Weldon
The test floor tests the engineers as well as the machinery........
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One thing they are learning is it take 2 ways for a record over 200. They qualify way over it but seem to have a problem coming back fast....this year will probably do it.
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Denis Manning made a device to try
to quantify corfficient of friction and
tested it on El Mirage....Bonneville.....asphalt
.......Black Rock........AND GAIRDNER..........
he has the numbers for you and told me them............
I did not write them down because......it is what it
is when you get there.....and you deal with it the
best you can.......
it didnt help him go faster there...........
Gairdner was bette than all the venues he tested............
Joe :)
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.....it is what it
is when you get there.....and you deal with it the
best you can......
The best I could hope for is a little help in making adjustments before the run. (see my recently posted speed-gear ratio Excel spreadsheet.)
I know there are a lot of you old hands out there who have enough experience to make good "seat of the pants" calls. I'm a late starter...I hope I live that long.
Til then all I've got to go by is the wisdom of my friends and a little bit of engineering.
Ed Weldon
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There is a very simple strain gage you can make yourself with housebound stuff.
A digital bathroom scale with the appropriate linkage can be used to determine a lot of things without going 200mph, once a year to find out.
Start out with a L shaped fixture that will load the scale when you pull on the 90 deg arm with a ski rope for example. That will teach you how it works and now you have to adapt the concept for whatever you want to measure. More important than absolutes is improvements.
If you are 25% slow , your going to need more work.
Data accusation (spelled the way I want it) is important and can be really easy, using it is usually the hard part.
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Jack D wrote?."A digital bathroom scale with the appropriate linkage?..Start out with a L shaped fixture that will load the scale when you pull on the 90 deg arm with a ski rope "
Good idea, Jack. And a stretchy rope. I see a simple flat 3/4" plywood box with the scale inside, the linkage and cable attachment on one end and a window on top so a volunteer (who provides both the weight and data acquisition device) can stand or sit on top and read the scale.
A trailer winch or even a lever working around a stake in the salt would give an steady pull. I'm not sure pulling with a car is a good plan. Best a 2 person job.
I'd prefer an old fashioned analog scale. The digital scale may not catch the lower moving reading which is the one you want rather than the higher breakaway static number.
Ed Weldon
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Wow, you are getting fancy.
What's an analog ?
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JackD asks---What's an analog ?
Silicon Valley word meaning "alligator".......or....
The picture that the tanker truck paints on the Salt on Speed Week Saturday morning .........or.......
The special log books used by electric streamliners......or......
The part of an old engineer that he loses before his memory...... or.....
My wife's old bathroom scale (that doesn't eat batteries) I use for weighing parts in the shop.......or.......
That chain of JackD's that I'm having fun pulling.........
Ed Weldon
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I thought an ALLIGATOR was the thing that lived in the ditch around Moroso's track in Florida.
On a press day before an event we had there, somebody fed him a whole case of frozen hot dogs from the snack bar and the next week at the car races he wouldn't go away.
A week later his GF called me to ask if I knew anything about it. Hell, that was more than a week. What was I going to remember ?
Moral to the story "It is easier to catch an ALLIGATOR with hot dogs than chains but don't run out. Fly out on a Sunday night and you can deny the whole thing. I know I did. "
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Edweldon, I was never to impressed with the So Cal tank, push rod suspension, ground effects tunnels, etc, looked more like it should have been at Laguna Seca than Bonneville, but of course they hit the real "hi tech" addition when they stabilized the tail fin with twisted safety wire. I probably talked to the same guy that you talked to last year and he was telling me that he was the "aero" engineer for the car and how low the Cd was and how there was no drag from the ground effects etc, but when I asked him why the new "tank" with all of its hi tech stuff, turboed motor, wind tunnel testing still has not gone as fast as the original, his answer, and I'm not BS-ing, was "well they had a V8 and we just have a four cylinder." Honest to God that's what he said! He quit talking to me and I needed to go some where for a big laugh.
Rex
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I think I would have been inclined to leave my lunch on his shoe. :wink:
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....."well they had a V8 and we just have a four cylinder." Honest to God that's what he said! He quit talking to me and I needed to go some where for a big laugh.... Rex
I think what you got was a canned answer crafted by some GM spinmiester. I'll bet that kid had a whole briefing book of that stuff to memorize.
I think the twisted safety wire says it all about the GM management attitude toward engineering.
But they're our GM. Why the H did they let themselves get into the mess they're in?
Ed
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OK, I'm going to need some ed-cation(my spelling, Jack).
You've got your trick, plywood friction gauge all set and quantified. You are going up and down the return road, can't get closer to the track than a couple hundred or so feet, taking readings and putting them in your laptop spreadsheet. The actual track surface has had dozens of runs on it over the last few days so it has no relationship to the return road. In the meantime your buddy is advancing your roadster thru the lines to the starting area.
In a couple of hours you have the info you need and hustle back to your car which is now three back and needs a driver suited up and ready to go.
Scott has been dumping some of his low power bikes out of the trailer and quailfying for a couple of dozen records. Now, here is the trick part. We know Scott has his finger on the cof of the surface today so while pulling on our firesuit we sneek a glance to see what he has in mind. There sits a 4 turbo, multi cylinder, many streamlined, fuel bike ready to go.
Oh my God!!! my data is wrong!!! You jump out of the car, wave a couple of people around while making whatever adjustments you think will be to your advantage. In the mean time the temp has fallen, the clouds and wind have come up and what data you have in your spreadsheet is junk.
Please tell how the cof reading from several miles away and hours ago will help during your 2.5 to 3 min of run time.
As always, in wonderment of overthinking this thing,
DW
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Read it again.
I never said I used plywood a laptop or applied it to the track. The only constant about the surface will be change. All the testing and evaluation I do is in my time at my location. You can listen to the CB and find out the tack conditions with the speeds and counting the spins. Scott is pulling your leg because the speed secret he is hiding is the watching of others. "Never make the same mistake the first time." The successful bikers are very selective where they drive for good reason. At El Mirage for example, you just kinda drive in the shiny spots. At Bonneville it is not much different. In any case, you don't want to run in the fluff or one of Al's tire ruts.
If you can't figure any of that out, more rules may be your only outlet from what I have seen. :wink:
*****FANFY DANCY: A DANCE FOR THE ADMIRING FANS, ONLY TAUGHT AT THE HIGHEST PR AND ENGINEERING LEVELS IN LIEU OF ACHIEVEMENT.
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This is fun.
Dan, I can see your chain hanging out??..
Jack?..I've never met you..I don't think?Why am I trying so hard to insult you?
Engineers are a strange breed. Detail oriented. Always wanting to know how this or why that. Constantly frustrated by their inability to control the world around them. Fascinated by new discoveries. Too often more interested in the process than the end result. A certain immunity to them is necessary for the survival of our species.
I've had a fling with data recorders. Not fun. Can be more damn trouble than they are worth.
Last minute gear change??Salt, sticky oil and perspiration. Not fun.
The 2 mile marker goes by at somewhere on the north side of 150. Fun
You see one of your best friends get handed a red hat. Fun
The best computer we have is still the one between our ears. That?s the one to focus on.
Ed
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Standing firm with your feet firmly planted on the
ground is no good if your head is also in the sand.
It leaves you vulnerable to attack.
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Dan flatters me. I had assumed all these years that nobody was paying the slightest attention to whatever it was that I was doing!
Sucess bears watching.
DW
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Knowing three of your opponent's cards is better than knowing none.
You just need to know if the cards you see are the one he intends to play.....
I think JackD is posting using Scott's name 8) ,
Sum
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Jack and Scott are actually a bunch of old Rosetta members that sit around the home and make this stuff up just to upset the SCTA kids. :wink:
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The previous response is why I want 12 guys like Scott on my jury. 12 engineers or Land Speed Racers can't agree on anything......J.D.
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I know you think it takes 19 Commandments to keep a biker like Scott in line.
Actually the list is still open with new stuff all the time.
Sometimes you even have to think about what is on anothers list.
"When you close the list, you have only fenced and leveled your own playing field.
That would be one of your big mistakes."
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Scott and I agree on this.....and other things. Even when there are bright eyed teenagers around. (Scott--don't you dare explain this to anyone or I'll come back from the grave as an itch in the middle of your back)
Ed Weldon
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Hey, Scott.....there is money at Bonneville....the BUB Meet....and the Hot Chicks come with the money
....the Fame you already have....at
least with me!!!!!!!!!
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Hey, Scott.....there is money at Bonneville....the BUB Meet....and the Hot Chicks come with the money
....the Fame you already have....at
least with me!!!!!!!!!
"Money at Bonneville can buy you Flame and cost a Fortune.
Just look around."