James Bailey

Interesting read....liked this "And it was a time when Losee spun the Enzo at about 195 mph—and realized he and his team had a lot to learn about the salt, including scrub radius, alignment, correct tires and Salt Flat-specific driving skills. “The great thing was the advice and coaching that came from some of the other competitors and the SCTA officials—people who had been dealing with the Salt Flats for many years. And one veteran driver in particular gave me the best advice after the spin—‘Don’t try to correct the wandering the car does on the salt, just think it back into the groove.’”

The Enzo runs in the Modified Sports class 360 cu inch class on fuel at about 850 HP and they bumped the redline up over the stock 8,000 RPM. Same basic class as Carl except smaller motor and better fuel.......

Carl Fausett

The ballast performs a few functions:

1) downforce without drag - most of the downforce devices that I am used to like wings and canards, etc, are removed because of the penalty in increased drag they provide. As a builder, you search for ways to get downforce with little or no drag penalty. Ballast is one of those.

2) safety - the ballast helps keep the nose down and helps the driver maintain steerage. If you loose steerage (like in the video that follows) then you may end up going backwards or sideways at speed, and all your aerodynamic streamlining is now backwards.

3) tractive force - the top speed of the car will be a result of being 1) HP limited, 2) aero limited, 3) gear limited, or 4) traction limited. Traction limited means the rear tires are actually spinning at speed as you have the HP to go faster, but not the traction to push it.

We scaled the car last night with all the panels on it and came in at 3383 lbs with driver, no fuel.

The tires are rated to 1700 lbs per tire, or 6800 lbs for the car (if perfectly distributed).

This gives us 3417 lbs to work with. I am expecting up to 300 pounds of downforce at the nose produced by the chin splitter and air dam, so the working remainder is 3117 lbs of ballast that we could use.

I'm not going to do that - we plan on installing 1200 lbs of lead ballast this Saturday, and in such a way that it weight balances L to R equally.

Here is the video that I spoke of - note what happens when he looses steerage and the air is allowed to get under his car...

F451

The salt is nothing like driving on a paved surface, its more akin to a dirt road, or snow, than pavement.

Just driving around on the salt in the parking/pits area is gnarly. At first glance it looks smooth, but pot holes form, little ridges, dips, bumps, etc.

I can't imagine getting out there at speed.

Anyone that does, has *****.

You really have to see it first hand to understand. I had no idea.

mark kibort

I think i posted that video first a long time ago.

anywyay i wouldnt count on downforce by just a splitter or air dam. pressure under the car stays at near ambient but can rise very quickly if you have any lift on the nose at all, which can happen because of the huge low pressure zone on the hood of our cars. hood vents allow you to get downforce without much drag. otherwise the air that was going under the car, will go over , or to the sides of the car.

obviosly, there was some stability issues with the RX7 . was it driver, set up, balance, who knows. But , my question was where did the amount of weight come into play. your ability to correct small changes in attitude might be endangered with too much weight. there is a balance , and thats why the question of where that weight value came from. another record holder did this successfully? also, as much as the weight is not a huge factor for acceleration initially, you dont have an endless run up. you have to do the calculation of how an additional 3000lbs of mass would effect acceleration with your given HP avaliable. (x .75 because of altitude) if you think about it, when you are at 220mph, the last 10mph will talke some time and power/torque. that extra 3000lbs might not give you the time you need to get it ramped up to 230mph.

just curious if you have done that calculation as well.

bcdavis

Yeah, when I was watching the cars run at El Mirage, I didn't see them using a ton of ballast. And the amount of time it took them to get up to speed and get shut down was not as long as you might think. I know El Mirage is a shorter course than Bonneville, but I still think acceleration is a factor.

Carl Fausett

Mark,

I have built a 1 degree rake into the belly pan, so we are nose-down at 35mm above the salt at the front and 65mm at the entry to the rear diffuser. Bernulli's principal will apply, and the pressure beneath the car will go lower from front-to-back. As the pressure under the car lowers, the relative pressure (relative to above the car) is a net of negative lift (downforce).

The car will be fully skirted to prevent air from the sides from being drawn under the car. As I posted, I do not have the skirts on the car just yet.

Please rest assured I have not posted everything nor told everything. No, we are not just relying on the chin splitter to keep us down! :-)

As to acceleration distances, I have 3 miles to the first trap, 4 miles to the second, and the last timing beam is at 5 miles. I think I'll be long past maxed out before 6-mile.

Carl Fausett

El Mirage is not only shorter, but I think it is dirt. Not salt. Jim Bailey would know this one...

BReyes

Carl, I love that movie about Bonneville , I think it is called something like, Worlds fastest Indian, where the one man on the motorcycle runs the flats. I want to see your videos! Best of luck.

Regards,

Carl Fausett

I love that movie too. When I was trying to recruit my reluuctant crew into this project, watching that movie was required. ;-)

Something to consider - there is no where we can go to test this iteration. Does it rattle at speed? Will the air stream lift my hood up, or push it down? Is it stable? I can't test it.

I know what this car feels like at 160 MPH as I have been there many times. But that's with grippy wide tires, wings and spoilers, etc.

I have no where to go that I can run this to find out wheather we "got it right". I have a friend who lives on a .7 mile dead end road - not long enough. Cant use airports. Even the main straight at Road America is not long enough and would tell us nothing.

I imagine this is what happened to Mr Mazda in that video. That was his first year and one of his early runs. I bet he couldn't run it anywhere and test or tweak his settings either. Thats why I'm not too quick to criticize his effort. He learned from it, came back, and set the record 2 years after that event. Thats the best possible outcome.

Z

"He turns up the oxygen mix" isn't exactly the best description of what happened with the RX7. The car experienced wheel spin and lost traction when the driver activated the nitrous system.

Good luck Carl!

LEADASS

You got big brass ones Carl! Godspeed.

bcdavis

It's the same organization running at El Mirage.
(SCTA)

When you talk about not having a place to test your car,
that's essentially what they are doing. A lot of people who
run at Bonneville are from So Cal, so El Mirage is only
2 hours away from LA. So they go out there 4 times
per year to test their vehicles prior to Bonneville.
The surface is dirt, but very similar. It's essentially
dry clay. So it's hard, but with a surface of dust on top.
They run the same tires, etc. But it is a shorter course.

James Bailey

Correct El Mirage is dirt. And much much smaller. Still interesting to see some of the stuff people fabricate...
The Mazda video lacks contrast because the salt looks all the same no reference markers to how fast it was going. Perhaps the best comparison is NASCAR where you see them crash @ 200 or so and see how high and far they fly because there are walls fences and other cars in the frame. Plus they have "airbrakes" and fins on the roof to break up the lift when flying sideways or backwards.

So yes this is very seriously dangerous stuff. It takes a brave man or a very foolish one to attempt this.

IcemanG17

I didn't realize the straights were so long....damm 6 miles wide open....that makes the traps in ORR seem like nothing

jorj7

Gee Brian, have you been on any of the ORR courses? The timing straights
at The Pony Express are 6 and 7 miles long. The timing straight for the
Bonneville 100 is 9 miles and the Silver State is 11 miles. The actual measured
time trap is shorter, but the straights have plenty of time/distance to get the car
up to speed and stay there, plus we're going 145-165 mph before we hit the
straights