Lake Gairdner Salt is underwater?

[Freud]

Did you ever notice that nobody from here goes faster down there than they do here? Maybe the length of the course doesn't really add any advantage.

Not even Al Teague.

I wonder why?

FREUD

[Rocky R]

We went to Lake Gairdner in 2000. We also waited till the last day for our best attempt. Had to wait for a Kangaroo to be chased off the course before we could run! Our best pass was 289mph which was the top time of the meet. During that run the rod broke off and went out through the bottom end. Coasted through the lights.

Had a lot of fun and tasted the best beer in the world-Coopers, which I think is brewed in Adelaide. That town also had about 3 girls to every guy. Interesting. On the salt the flies were so bad during the day we all had nets hanging from our hats. Great experience.

RR

[Glen]

Thats why they sent Keith Turk down there......to draw the flies away from the racers and to troll for the roos on the course.
Glen

[Sumner]

Did you ever notice that nobody from here goes faster down there than they do here? Maybe the length of the course doesn't really add any advantage.

Not even Al Teague.

I wonder why?

I always assumed if you had the hp that a longer course would mean bigger speeds.  Tom Burkland has finally turned the light on in my head about how that doesn't always work.  What I know now, and Tom or anybody jump in here if I don't have this quite right, is that every car has an aero drag that relates to that cars Cd, frontal area and speed.  The drag increase dramatically as the speed goes up resulting in the often stated formula that it takes 8 times the hp to go twice as fast.  

The solution seems easy, more HP.  The problem is you need to get that HP to the ground through the tires.  Now you are dealing with the traction available to you, which is dependent on the surface (salt or dirt in our case), the tire patch and the weight on the tire.  Tom says "0.6 is the upper end of salt surface friction coefficients, which range all the way down to about 0.22 in wet years".

So you have the aero drag holding the car back and the HP trying to move it forward through the available traction conditions.  Overcome the available traction and you are going to spin the tires and not go any faster no matter how long the course is.  The only way to go faster is to put the power to the ground through more tires, like in Tom's 4 wheel drive streamliner; have better (less wet) salt conditions (and these can vary through the course of the day); cut down on the aero drag of the car; or as most people do, add weight to increase traction.  

Over in Australia at the lower altitude the aero drag is going to go up, but I don't know what amount.  If their salt offers more traction than ours that is a plus.  Sounds like Ack Attack was having problems hooking up the tire to the salt, probably due to the fact it was under water a few days before.

On Tom's streamliner they are up against the available traction using only 52% throttle on their 450 mph run.  Of course all I'm talking about here only deals when you are running a certain speed and can't go faster due to tire spin.  It is really amazing to me now the speeds Al turned in only powering the rear tires in his streamliner!!

Above I just touched the surface of what Tom has related to me and if anyone is interested in more PM or EM me.  I might also try and get it down on one of my web pages once I get it really straight in my head, if that is possible.

Had a lot of fun and tasted the best beer in the world-Coopers, which I think is brewed in Adelaide. That town also had about 3 girls to every guy. Interesting. RR

I'm married and an old man now, but my wife doesn't seem to mind me looking   .

On the salt the flies were so bad during the day we all had nets hanging from our hats. Great experience. RR

I was wondering about the flies this year after all the talk.  I don't remember seeing anyone wearing nets in Jon's pictures.  If the wind is up does it blow them away like it does the gnats here?

c ya, Sum

[John Burk]

How fast could you go on 100 miles of salt ? The Speedweek results from a past year when they showed the speeds in all timed sections showed these differences between 5th mile average and exit : 200 mph - 2 to 3 mph , 300 mph - 6 to 12 mph and 400 mph - 14 to 17 mph . That would say the faster you go the more distance you'd need .

[1212FBGS]

the distance you need is governed by.... the terminal velocity of your aero drag, available hp, available traction. those 400 mph cars will eventually hit the proverbial brick wall.

[ack]

Just got back to Port Augusta.  We could only get about 8 miles of usable salt and about 1/3 of it was sloppy wet. The Aussies were great hosts. Charlie Hennekam from FIM and Ron and Max from Motorcycle Australia all were a great help but the conditions just were not good there.  Sam got one run in at 247 average with 3 Mile run up and was almost blown off the course at the timed mile entry speed into the timed mile was 234 exit 260.  We tried to run Friday but the wind was blowing at 7:00 AM and never stopped. Who gets the poster?

[generatorshovel]

I was wondering about the flies this year after all the talk.  I don't remember seeing anyone wearing nets in Jon's pictures.  If the wind is up does it blow them away like it does the gnats here?

c ya, Sum[/quote]
Having returned from a week on Lake Gairdner I noticed as the week went by , the flies got worse, maybe they hitched a ride out on the 1st vehicles to set up on the salt ? and thought it a great idea, and talked their freinds into doing the same ?
I also wonder if hitching a ride in the akattack streamliner qualifies a fly as "the fastest fly in Australia?"
    Cheers    Tiny (484 M/F 175 fastest Postie bike in Australia    )

[Sumner]

How fast could you go on 100 miles of salt ? The Speedweek results from a past year when they showed the speeds in all timed sections showed these differences between 5th mile average and exit : 200 mph - 2 to 3 mph , 300 mph - 6 to 12 mph and 400 mph - 14 to 17 mph . That would say the faster you go the more distance you'd need .

That is true John as long as you don't get to the point where traction limits the speed, Kent's "proverbial brick wall".

Take Rick's 330 mph motorcycle motor powered streamliner.  He is still exiting the last mile at a higher speed than his average in the last mile.  He told me he looks at it as a long acceleration run like a long drag strip.  He tries to accelerate as fast as he can once he leaves the starting line as the course is not long enough for him.  In his case if he could loose weight then he might accelerate faster and go faster.  But in the process of shedding weight he then might loose traction and hit the "brick wall" where he can't go faster because of wheel spin.

I worry about this with my lakester as it is not going to be a fly weight.  I don't think I'll be too heavy once I have a blown 'busa motor in it, but to start with the car might not accelerate fast enough to do 175 in the first quarter of the 3rd mile on the short course to move over to the long course.  I won't have this problem with the unblown 750, because it probably won't have enough power to run the 175 no matter which course it is on.  But after I put a turbo on it I'm hoping it can run over the 175.

Here are a couple more comments from Tom to me about my car (750 cc powered lakester).  Note these comments are in response to me wanting to run 200 with the motor putting out between 250-300 hp with the turbo.

At 200 mph you will only be capable of producing 563 pounds of thrust with 300 HP (see more about thrust below). This requires 938 pounds of weight on the drive tires at 0.6 friction coefficient to prevent tire slippage. If you could produce this much thrust the car would still be accelerating at 0.35 G if the 1600pound weight is close (what I'm guessing my car might weigh). This is a fairly high acceleration figure for typical LSR cars. At zero speed it is very common to see 0.6 G, but as the speed goes up the power gets consumed by air drag and the acceleration numbers will drop off. For a low powered car like this I would always attempt to reduce the weight as much as possible without sacrificing structural integrity. You can always add ballast later if the power increases enough to warrant it. Removing weight from an already completed car can be very difficult.

The equation for the thrust figure I mentioned is HP = [ F(or thrust in pounds) X V (speed in mph) ] / 375. This is just the standard force times distance over time to get power relationship. I was only using it as an example of the upper limit of how much thrust you needed to account for in your traction assessment. This power uses rear wheel power also, not the engine power, so you would need to figure in the efficiency of the transmission and any power losses between the engine and tires.

Once you have the upper limit of thrust you can produce for the assumed power available you can convert that to required weight on the drive tires to produce enough traction to use that amount of power. The 0.6 is the upper end of salt surface friction coefficients, which range all the way down to about 0.22 in wet years. What you have already noticed, and Rick Yacoucci told you about also, is that lower powered cars are much better off running at light weight for acceleration purposes. The additional weight is not required for traction purposes and only succeeds in lowering the acceleration rates. With better aerodynamic approximations you can predict the drag of the car and match it to the available power to get the terminal velocity. If you attempt to exceed this traction limit the tires will spin and the car will not speed up as desired.

This last sentence is what the really high speed cars come up against, like Al's streamliner along with Tom's and maybe you also John when you get your car there.  The speeds you mentioned were with cars that still have not meet the traction wall. What I like about your car is all the weight over the drive wheels (front wheel drive) and the fact you have all that weight forward of the center of pressure.  A lot of cars that are running with rear-wheel drive only have the problem as they add weight at the rear to help with traction move the center of gravity towards or past the center of pressure and then have handling problems.

Still a lot of the really fast cars would like more distance to give them a chance at finding that fine traction line that would allow them to increase their speed.

Now here is some really good stuff that helps understand this and I hope Tom doesn't mind me sharing it with you guys.

The speed limit based on track conditions relates to length and surface conditions which create the friction coefficient to generate the upper limit on traction. I had looked at the three mile parachute test run maximum acceleration number from our data recorder, which I knew from the cockpit was using lots of wheel spin, and projected the last mile speeds using this friction coefficient to tell the crew that we might not even be able to qualify against the existing Nolan White record of 413.156. My theoretical best case prediction was a last mile of 420.5 mph with optimum power application for the entire distance. This usually means the actual runs will be 8 to 10 mph slower from the alternating combination of wheel spin slowing the acceleration when the driver overpowers the traction and under powered operation when the driver pedals the throttle to get hooked up and looses some acceleration. The lower the surface friction is the harder it becomes to manage this wheel spin condition all the way to the exit trap. You know from the time slip that our morning run resulted in a 418.425 last mile average, which was very close to the traction limited best possible speed at 0.42 friction coefficient. The afternoon run had about 0.015 lower friction coefficient for a best possible of 417 and the actual run was 415.616. The runs in the heat of the day with solar gain on the track draw more moisture to the surface through evaporation and capillary action causing the reduced friction numbers. Our best run with this car was a fuel calibration pass at the 2000 WoS with a 0.48 friction coefficient that resulted in the 438.815 mile average you have posted on the web site. This run was farther from the best possible speed because the throttle was too far open and wheel spin was excessive. The friction coefficient is easily obtained from the data recorder as we leave the push vehicle at low speed. You can watch the wheel speeds on both ends of the car as they quickly pass the rate of speed gain on the ground to verify tire slippage and read the accelerometer at this point. As the speed increases the air drag produced by the body shape and rolling friction of the drive train are subtracted from this maximum available thrust to maintain the current speed. Any remaining thrust is available to accelerate the car if you have enough power to produce that much thrust at the higher speed. Our streamliner has the luxury of more power than it has traction all the way up to the high 490 mph range on tracks with friction coefficients of 0.60. For the slippery surfaces at 0.42 this speed is over 820 mph which is not even realistic. We reach the terminal velocity on the slippery tracks in about the same distance and then have to hold throttle at the tire slip point through the timed sections since the track will not take any more power application. We have measured friction coefficients up in the 0.6-0.62 range with our other cars in the past but have yet to get the streamliner through the timers in these conditions. Some of the high speed predictions you may have heard from me are based on the 0.6 friction and thirteen miles of hard smooth surface to run six miles of acceleration into the middle mile for a two way return average. These were the design conditions for the car. On shorter tracks and slicker surfaces we obviously run slower trap speeds within the car and driver?s capabilities. To this point the track has always been the limiting factor in how fast the car has run. Hopefully we will someday get the opportunity to run full power at the higher speeds on these better tracks.

I'm still trying to put all of this together to the point of better being able to predict the potential speed of a car, say Hooley's Stude or my lakester, if I knew the frontal area, approximate Cd, HP, weight on the rear tires, and track friction coefficient.  Tom and some others obvisiouly have it all figured out.  There is some really good information there, thanks Tom, and it gives you a much better idea of what the really fast bikes, cars, lakesters and streamliners are up against.  John I think you will be in that list also with your streamliner.

c ya, Sum

[JackD]

Campos, Teague, White and others did it with the seat of their pants.

[Baatfam]

Wow....for a someone new to all this, this thread has been a fascinating read

Bob T.

[Malcolm UK]

Why can the fastest not achieve the same speed on a 'new' track?

In addition to the relevant mathematics on getting speed out of a particular track, there are operational matters that have to be considered.

No two locations are the same for speed attempts even if they are both salt flats, so what you take from one to another is only part of the story.

Whilst 20 years behind the wheel of a car means that the driver knows his equipment you cannot take those years of driving at Bonneville and expect to achieve somewhere else (say Lake Gairdner), the same or better in five (5) days.

I learnt this lesson when racing on the salt in 1999 with the Gillette Mach3 Challenger bike.  Even allowing for previous visits to the salt and a UK record, the British team had planned to be on Bonneville for 16 days of the total 21 that the attempt, with travel, would take.  Even then we lost complete days to 'engineering' and to weather conditions.  

In Britain (where all attempts are on private time) I am hiring facilities for four days at a time to give teams the chance to break their target records and that is with tarmac airfield surfaces.

Achieveing a record - especially at the 400 + level - takes well designed and assembled equipment but you will need the patience and ability to work on the chosen track in the prevailing weather conditions - your operation as a whole has to be correct.  You may require that element of good fortune (some may say good luck) that comes from being ready to set speed when the weather conditions open for the hour or two that you need.  

I organised an outright British LSR attempt that achieved the teams records after two and a half days, because they were ready for the 90 minutes that the weather abated.  The window closed after the bike entered the measured timing trap on its return pass.  

(My two pence worth on a complex subject)

[k.h.]

The world needs more fast cars for proof of concept @ 400 mph.  Here is one for sale in Oklahoma:

http://www.race-cars.com/carsales/other/1130993135/1130993135ss.htm

[John Burk]

Rather than a wall I'd think it more as a diminishing return curve . On graph paper I put the 3rd 4th and 5th mile and exit speeds for runs Vesco (420 mph in the last mile) Teague (355 mph) and Danny Boy (303 mph) made at Speedweek in 1999  . A drafting curve that followed all the dots says Vesco would have peaked out at 487 in 9 miles , Teague 398 in 8 miles and Dally Boy 335 in 7 miles . All these cars went faster at other times , these were just random runs I picked .

[JackD]

Simply put "when push forward equals shove back you find the wall."