80 replies to this topic

[Dan333SP]

I know exact numbers are hard to come by because of insufficient data or team secrecy, so perhaps this thread will remain largely speculative, but what cars had the highest absolute downforce potential in F1, Indy, and Sportscars? I was reading an old issue of F1 racing where Patrick Head discusses the FW07 and mentioned that it generated 30% more downforce at speed than a 2006 F1 car, which seems somewhat insane but I guess the full ground effect cars with skirts had incredible downforce. Which car was the stickiest of that breed, and could it compare to the downforce of the best sportscars of the late 80s/ealy 90s? I've read that the Toyota Eagle MKIII produced 10,000 lbs of downforce at 200mph, which is absolutely incredible and many thousands of pounds more than the highest downforce configurations of cars built to current regulations, but maybe there was an even more impressive machine from the same era? How about Indycars, of which I know little? When did they peak? I'd guess in the late 90s/ealy 2000s, but that is completely uninformed... Thanks for any input!

[gruntguru]

May I suggest, if we are going to post DF from various racing categories, that the vehicle mass also be posted?

[DaveW]

I offer the Lotus 80:



I recall Peter Wright stating that it would "go round any corner at any speed". It didn't work, partly because suspension technology of the time was incapable of supporting the aero loads. It probably represented the ultimate F1 aero design, however. Skirts were banned shortly after, which suited Lotus' solution to the 80's suspension issues. That appeared in public as the Lotus 88, which was banned for political reasons. Not the best image of the 88, perhaps, but it does include ACBC & a rather pensive Peter Wright:



Technically, I think, increasingly restrictive regulations caused F1 to do down hill from that point.

The Chaparral 2J of Jim Hall was probably the most advanced aero race car in the USA.

[Ross Stonefeld]

Define 'downhill'. From an engineer's perspective or a practical ones? The cars of today are already boring enough as they go around the corners on rails, I can't see over-developed tunneled cars being any better.

[DaveW]

Define 'downhill'. From an engineer's perspective or a practical ones? The cars of today are already boring enough as they go around the corners on rails, I can't see over-developed tunneled cars being any better.

Couldn't agree more, but the thread is about down force.... Down hill -> lower L/D, for me.

[Tony Matthews]

I offer the Lotus 80:


It didn't work, partly because suspension technology of the time was incapable of supporting the aero loads.

Another problem was the skirts jamming, as they and the channel that they worked in was curved to go round the inside of the rear wheels, and used to stick. I hadn't heard about the suspension problems.

[DaveW]

Another problem was the skirts jamming, as they and the channel that they worked in was curved to go round the inside of the rear wheels, and used to stick. I hadn't heard about the suspension problems.

Details, Tony.... You are correct, of course, and it had other issues too. But the thing porpoised uncontrollably by the time it left the pit lane. That fact was the reason for developing the twin chassis 88 &, ultimately, the adoption of active suspension.

[mariner]

I remember when the Lotus 88 was banned Colin Chapman getting very angry and even hiring lawyers ( novel in those days). In one statement he argued that all he wanted was the right to experiment and fail rather than being stopped. Sounds kind of funny today!

Like dave W. I see the Lotus 88 as a pivotal design not because it worked ( it never actually turned any really quick practice laps) but because it marked the end of innovation in F1 and what we see today in car design can be traced back to the short period from the Lotus 78 through the Williams and the Lotus 80/88.

I see why because cornering speeds were rising so fast but it did change the whole regulatory approach.

[DaveW]

Apologies, Dan, I seem to have hijacked your thread, & I don't know the D/F figures for the 80....

However, it is interesting to note (for Tony) that some of the plan area of the 80 had been thrown away for the 88 (I guess because it was realised that the 80 was a step too far), which allowed the skirts to be straight.

In retrospect (hindsight is a wonderful thing), for it to have worked, the 80 would have required a quantum leap in chassis stiffness, a push-rod layout, active suspension (or, at least, a large step forward in damper & spring technology), better tyres (probably), & a few other knock-on stiffness & strength improvements, many of which were only available a few years later.

[Tony Matthews]

I remember when the Lotus 88 was banned Colin Chapman getting very angry and even hiring lawyers ( novel in those days).

I was called in to prepare a set of drawings to try to prove the point that the 88 was legal, as I personally believe it was.

[cheapracer]

Nice try with F1 but sports cars off a far greater area of diffusers and wing area that far exceeds F1.

As mentioned above the Toyota Eagle MKIII probably takes the cake but I wouldn't raise an eyebrow if someone told me a Supermodified or a Sprintcar was the winner ...







And then theres Top Fuel, what do they put down at 300mph adding a 1000lbs of down thrst from the exhaust ..



I have no reason at all for this shot of Manfred von Brauchitsch at Donny 1937...

[zac510]

What about one of those Pikes Peak unlimited-category machines?

[cheapracer]

What about one of those Pikes Peak unlimited-category machines?

You have a party on that splitter.

seriously some of you need to get out of the "F1 is the ultimate" mindset.

Edited by cheapracer, 11 August 2010 - 12:12.

[Dan333SP]

Well, I was asking what the highest downforce for each type of racing car was, so F1 was included in that... I'm sure things like Sprint Cars and the Pikes Peak unlimited cars have lots of downforce, but just having a giant wing or two can't possibly produce as much downward thrust as a car with a fully contoured underbody AND wings like the group C cars and GTPs? Apparently the Allard J2X from the last year of the GTP series matched the MKIII Eagle with around 10,000 lbs of df at 200 mph, though the car had so much drag and so little power that it would never be able to approach that speed even on the fastest track...

[Dan333SP]

Also, don't know how I didn't find this list of exactly what I'm looking for on Mulsanne Mike's website-
http://www.mulsannes...r.com/data.html
It has downforce figures at 200mph for many of the best sportscars of the last 40 years, plus assorted IndyCars and the Lotus 79. Some interesting things to note- The highest on that page is the Nissan P35 GTP car at just over 10,000 lbs. with a l/d of 6:1, incredible. It looks like the best of the IndyCars was the Panoz from '07 with 5700 lbs and a l/d of 3.26:1.
The Lotus 79 had a relatively puny 4,453 lbs at 200 mph, but I'd bet that the 88 was at least 1,000 or 2,000 lbs better than that.
Also, the Porsche 908 and Ford GT40 from Le Mans '69 had around 170 lbs, just enough to keep the nose from lifting and sending the car into the wall at 200mph I guess! Still curious about sprint cars and maybe even rally cars, anyone have figures for those?

[Tony Matthews]

The Lotus 79 had a relatively puny 4,453 lbs at 200 mph,

Relatively puny, but astonishing for only a second-generation GE car. However, did it ever reach 200mph in a race, or is this a projected figure? I suppose Monza might have seen it reach the magic figure.

[cheapracer]

Well, I was asking what the highest downforce for each type of racing car was, so F1 was included in that...

I missed that, my bad sorry, I went off the thread title.

Some of the Supermodifieds do have GE but surely the simply massive amount of wing area they have can't possible escape your senses? It wouldn't be that hard a task to compare corner speeds with F1 given that corner radius's are available.

Can't get to Mulsanne corner for some reason tonight but I imagine they don't have S'modifieds, Sprintcars or Top Fuelers on that list?

The Lotus 79 had a relatively puny 4,453 lbs at 200 mph, but I'd bet that the 88 was at least 1,000 or 2,000 lbs better than that.

Puny relative to what? Left everything for dead in it's day except for the Brabham fan car at Sweden.

Edited by cheapracer, 11 August 2010 - 16:59.

[Tony Matthews]

Puny relative to what? Left everything for dead in it's day except for the Brabham fan car at Sweden.

I think Dan meant relative to modern stuff, but for its day, as I said earlier, an astonishing figure. That period must have produced the steepest learning-curve for drivers of all time.

[Ross Stonefeld]

I'm not sure that's even puny compared to today. It's near equal to an Indycar at the start of the century when it was a free-for-fall series.

[Jones Foyer]

I recall reading something about aerodynamic downforce and something about one car that tested with so much downforce it blew out the tires.

I know Jim Hall was getting good downforce out of his sucker car too. Probably a lot of the experimental cars of this era never accurately tested the downforce numbers (the means, and equipment not being available), so it would be speculative to rate them.

Edited by Jones Foyer, 11 August 2010 - 18:01.

[ivanalesi]

I've always taken the old F1/GTP downforce figures with a pinch of salt, they are probably true in some laboratory conditions. Some 2 yrs ago Formula Master went to Anderstorp, the track record on this track was still held by Lauda and his Brabham fan car. I don't remember very well, but I think the FM car broke the record or at least came very close to beat it!
I guess the FM Yokohamas are much more advanced than the tyres on this Brabham, but still the power difference is huge advantage.
It's 250 bhp vs. 520 bhp, FM also had something like 700 kg downforce.

Edited by ivanalesi, 11 August 2010 - 18:38.

[cheapracer]

Probably a lot of the experimental cars of this era never accurately tested the downforce numbers (the means, and equipment not being available), so it would be speculative to rate them.

They are called springs and they go on all 4 corners, know the spring rates know the downforce.

[MatsNorway]

In the pikes peak category i think this is the one is the hotshot.

http://lh3.ggpht.com.../Toyota Celica


"Millen captured the record for the fastest ascent of the 156 turn, 12.42 mile (19.99 kilometer) Pikes Peak International Hill Climb. He broke the old record time by 40 seconds when he ascended the hill in 10:04:06 in 1994 in his all wheel drive Toyota Celica.[8] His record was broken on July 21, 2007 by Nobuhiro Tajima driving the Suzuki XL7 Hill Climb Special to a time of 10:01.408.[9][10] However, Tajima's record was set after the Pikes Peak surface was partially paved whereas Millen's record was on dirt."


Video of it from the festival of speed

http://www.youtube.c...eos=Ju5VJ1taiUc

[OfficeLinebacker]

May I suggest, if we are going to post DF from various racing categories, that the vehicle mass also be posted?

I see where you're going here. What if we were to put it like this: what is the speed at which (theoretically) the highest DF cars of each category would stick to the ceiling if driven upside down?
j

[mariner]

from Tony Matthews

"I was called in to prepare a set of drawings to try to prove the point that the 88 was legal, as I personally believe it was."

Tony are these drawings the ones you are referring to?

http://www.grandprix...ft/ftpw021.html

If so I think you have earned your place in F1 history as well as your cutaways skills.

One point on max. downforce , you really have to define the performance envelope because the higher the upper end of the cars speed range the more likely it is to "win" the prize. For example the Turbo cosworth CART cars of the 1980's may not have had all that much inherent downforce but the fact that they were the only cars to consistently corner at 220+ mph probably means they had very high total downforce just because of the extreme speed but almost any other car would beat them at say 100 mph

[Dan333SP]

One point on max. downforce , you really have to define the performance envelope because the higher the upper end of the cars speed range the more likely it is to "win" the prize. For example the Turbo cosworth CART cars of the 1980's may not have had all that much inherent downforce but the fact that they were the only cars to consistently corner at 220+ mph probably means they had very high total downforce just because of the extreme speed but almost any other car would beat them at say 100 mph

Well, I was trying to set a baseline of a theoretical 200mph, even if the car can't achieve that or if it can achieve more than that. As for the CART cars on superspeedways, they weren't really that high, they just needed enough to get the tires to grip the banking and they wanted to minimize drag at all costs. In fact, according to that page I linked to, a 2001 Reynard in super speedway trim (Fontana, Michigan) produces only 1,000 lbs of df at 230 mph, with 930 lbs of drag, compared to the Eagle MKIII I mentioned ealier with 10,000 lbs of df at 200 mph and just over 2,000 lbs of drag.

[munks]

They are called springs and they go on all 4 corners, know the spring rates know the downforce.

Uh, you still need the deflection to calculate it. And sensors and telemetry weren't quite as prevalent 40 years ago.

[cheapracer]

Uh, you still need the deflection to calculate it. And sensors and telemetry weren't quite as prevalent 40 years ago.

These things make life faster and were designed/invented using the same math/physics as engineers have always used.

The car's bottoming in turn 3 - ok we will put harder springs in < This answer hasn't changed in 100 years, only the speed the solution is arrived at.

Have some respect for engineers of old who managed to make planes fly, meet 2 ends of a tunnel in the middle of a mountain and make race cars go very fast all with the aid of a slide rule and not an electronic device in sight, they knew exactly how much downforce they were achieving.

[Marc Sproule]

What I would like to know is what were the numbers for positive downforce, produced by the exposed wings and bodywork, versus the negative lift generated by the underbody?

Not gonna hold my breath on that one of course.

Drag was mentioned previously and it's always been my understanding that negative lift didn't add to the drag. So,when tunnels were der rigeur, the quest was to gain as much from the underside because it didn't bring the drag penalty that positive downforce did.

Attached are links to some snaps from Indy '85. The Marches had the field pretty much covered that year because they had the best underbodies....read Alan Henry's book on the March F1 and Indy cars for a good explanation. Note how little wing some of the Marches were running compared to the Lolas.

I've also attached a couple of links to the Mc Larens at Long Beach in '82 where Watson and Lauda ran without front wings because of the negative lift from the underbody.


Marches:

Pancho
http://www.flickr.co...57623324227456/

Sullivan
http://www.flickr.co...57623324227456/

Johncock
http://www.flickr.co...57623324227456/

Al Sr.
http://www.flickr.co...57623324227456/

Mears
http://www.flickr.co...57623324227456/

Rahal
http://www.flickr.co...57623324227456/

Lolas

Mario
http://www.flickr.co...57623324227456/

Al Jr.
http://www.flickr.co...57623324227456/

Howdy
http://www.flickr.co...57623324227456/

Long Beach '82

Watson
http://www.flickr.co...57623186790747/

Lauda
http://www.flickr.co...57623186790747/

Some personal notes....

At the Michigan 500 in '00 Chuck Matthews, Montoya's engineer that year, told me that due to high speeds there, 240+, if you missed the static ride height by as little as 2mm, yes, 2mm, you were toast. That's how important what was left of the ground effects at that point were.

Chuck also told me at Sebring, in pre-season testing, his first with Montoya, that the previous year in the Michigan 500 the computer tracings for steering input, showed that Montoya was driving the car sideways. Yes, sideways, something you're not supposed to be able to do for very long on an oval. Montoya had done it for 500 miles. That's how fine a line they were running on total downforce.

In Dec. of '81 I had to good fortune of going for a ride in the first March 82G GTP car at Laguna Seca. I was supposed to go with Teo Fabi but ended up with Paul Newman as my chauffeur. This was before the additions to the track that did away with it's being a high speed track.

It was March's first foray into IMSA's GTP wars and had some serious tunnels in the underbody. There were no sliding skirts and the static ride height was supposed to be 2" if memory serves. We ended up about 2 seconds under the lap record for GTP cars.

The sensations of being in a ground effects car at speed were almost overwhelming. We went through the high speed stuff at speeds I figured were impossible. And proceeded to go faster each lap.

It definitely gave me a great appreciation for what it would have been like to have been a driver during the seriously high ground effect era. They have my utmost respect.

A few years later I found out...one of the mechanics told me...that I had been, unbeknownst to Newman, the recipient of a "sponsor lap". I was writing a story about the car for "On Track" magazine.

Robin Herd was there that day and had had the mechanics set up the car a bit lower than the 2" minimum static ride height the rules called for.



This is the only pic of the 82G that I currently have in my flickr stuff. I may have some more detailed shots of the body work and if so, they'll eventually end up being posted here.

http://www.flickr.co...57623186793517/

[Tony Matthews]

Tony are these drawings the ones you are referring to?

They are, mariner, but some cheeky person decided to add colour - and how they have suddenly become someone else's copyright, I do not know. The odd angle was used because Colin Chapman did a little sketch on some lined paper - I still have it somewhere - and being a bit in awe of him I thought there was more chance of him accepting the finished illustrations if they bore some relationship to his sketch. As it is, although it looks slightly odd, it shows the principle quite well. Doug Nye used some of the individual drawings in 'The History of the Grand Prix Car', but not all, then commented that they didn't tell the whole story! Well Doug, you only had to ask!

Many years later I did a composite version, which I posted before, it might warrant another posting... By the way, there were other drawings too, showing how a conventional F1 car rolled in a corner, and how the 88 chassis rolled inside its separate outer body. I exagerated the roll considerably to better show what was going on, and when a Lotus drawing-office person saw it, he pointed to the conventional car and said "Obviously being driven by Jarier!"

In later years I kept either good copies, or the originals, of everything, as otherwise, as in this case, things disappear...



Edited for spellin.

Edited by Tony Matthews, 12 August 2010 - 09:48.

[murpia]

They are called springs and they go on all 4 corners, know the spring rates know the downforce.

Uh, you still need the deflection to calculate it. And sensors and telemetry weren't quite as prevalent 40 years ago.

Don't forget about the bump rubbers!

Regards, Ian

[Dan333SP]

VERY cool information, can't believe you got to go for a hotlap around Laguna in a GTP driven by PLN! Amazing... Just imagine, as quick as that March felt, the Eagle MKIII probably had double the total downforce of that car thanks to a decade of GTP aero development, not to mention better tires. Must have been gut wrenching to go through the old turn 2 at Laguna in the Eagle if they'd run that config. Some of the Eagle's lap records on North American tracks have just fallen in the last few years to the very quick Porsches, Acuras, and Audis in the ALMS, which is probably a sign of how bad the tires were in '92 more than the cars of today being that much better...

Edited by Dan333SP, 12 August 2010 - 12:20.

[Charles E Taylor]

[b]Highest Downforce Figures[/b


In absolute terms of loading the highest figures achieved may well be with Sports Cars competing at Le Mans.

While at the time there may have been no really accurate way of estimating the total figures (Many ware extrapolations of the wind tunnel estimates at circa 200mph) some feeling may be demonstrated as to the lack of real understanding of the total loads generated. Of course today everything is strain gauged so the loads can be more accurately assessed.

In 1988 the entire Sauber Mercedes team was withdrawn from the Le Mans 24hr event. The cause of this was gross overload of the Michelin tyres at the end of the Mulsanne straight. The tyres failing at high speed due to too much down-force pressure.

Some mention can be found here,
Here

These were 900kg cars, with speeds approaching 400kph at the time before the chicanes.


I hope this give some feeling for the nature of “Downforce”.






Charlie

[munks]

These things make life faster and were designed/invented using the same math/physics as engineers have always used.

The car's bottoming in turn 3 - ok we will put harder springs in < This answer hasn't changed in 100 years, only the speed the solution is arrived at.

Have some respect for engineers of old who managed to make planes fly, meet 2 ends of a tunnel in the middle of a mountain and make race cars go very fast all with the aid of a slide rule and not an electronic device in sight, they knew exactly how much downforce they were achieving.

Whether I have respect for engineers of the past is irrelevant (for the record, I do have an immense amount). But I think we'd both agree that the use of the word 'exactly' above is hyperbolic. I doubt they even knew the downforce within 10% with any confidence. Even in your example, is the car bottoming due to the downforce, or due to a bump in the road? Still, you're only getting a binary answer with a finite set of springs you have on hand. Throw in non-linear geometry (and bumpstops, as somebody mentioned), tire growth and spring rates at the given speed and camber, etc. and it simply takes more time to calculate than is worth it.

They'd be far more interested in what the stopwatch said than anything else. And it's not much different now, considering how little we really understand about tires.

[cheapracer]

I doubt they even knew the downforce within 10% with any confidence.

I think you may be wrong and right at the same time - these designers were leaning heavily and employing the sort of people who put 747 Jumbo's thru to airforce fighters into the air, they knew exactly on paper what downforce they should be acheiving but having that actually happen on a racetrack probably brings your 10% into play as a variation on track.

[McGuire]

Of course, downforce figures aren't terribly comparable unless they are quoted at a common speed. Many historical downforce figures are quoted at 200 mph... which are extrapolated/extended values as there were no tunnels that could blow at that speed. Meanwhile, there were a number of cars capable of big DF numbers @200 mph in their max aero configuration. However, many of them couldn't do 200 mph hauling that package -- too much drag/not enough power. So these are more theoretical or hypothetical numbers. For whatever it's worth, the grand champion for max hypothetical downforce might be Millen's Toyota Pikes Peak car. Whatever it was capable of developing in gross downforce, it likely never achieved it in practice, as it ran on dirt at high/variable ride height and at relatively low speeds up much of the mountain. But in the wind tunnel I bet it could make a hell of a number. A couple of large boys or small men could nap comfortably in there.


6200+ lbs DF at ~0 mph:

Edited by McGuire, 12 August 2010 - 16:00.

[Catalina Park]

6200+ lbs DF at ~0 mph:

[gruntguru]

For whatever it's worth, the grand champion for max hypothetical downforce might be Millen's Toyota Pikes Peak car. Whatever it was capable of developing in gross downforce, it likely never achieved it in practice, as it ran on dirt at high/variable ride height and at relatively low speeds up much of the mountain. But in the wind tunnel I bet it could make a hell of a number.

I wonder what range of yaw angles were tested in the wind tunnel. I'm sure a lot of the extreme DF cars discussed here would suffer large DF reductions in a 45 degree power slide on dirt. (sprintcars a possible exception but only in LH turns )

[Marc Sproule]

VERY cool information, can't believe you got to go for a hotlap around Laguna in a GTP driven by PLN! Amazing... Just imagine, as quick as that March felt, the Eagle MKIII probably had double the total downforce of that car thanks to a decade of GTP aero development, not to mention better tires. Must have been gut wrenching to go through the old turn 2 at Laguna in the Eagle if they'd run that config. Some of the Eagle's lap records on North American tracks have just fallen in the last few years to the very quick Porsches, Acuras, and Audis in the ALMS, which is probably a sign of how bad the tires were in '92 more than the cars of today being that much better...

Actually it was about half a dozen laps and turn 2 was not as amazing as T4. Turn 2 was just scary because I figured there was no way in hell we were gonna get through there going as fast as we were. And, of course, we proceeded to go faster with each lap.

Four was a different story though. From old 9 to there we were flat out, but at the approach to the uphill left-hander he had to get on the brakes a little, drop down one gear and then hammer the throttle.

This was right after lunch, I was sitting on the left side, hanging on to my shoulder harness with one hand and the front rollover hoop with the other. With the g-loads pulling on my head and helmet, my head fell over and lunch nearly got recycled into his lap. Fortunately it didn't and I was able to better prepare myself for the next laps.

It was truly amazing.

After my ride the studio pilot that had flown Paul up from LA got his turn in the car. We had had a moment with a sticking throttle in the corkscrew on the last lap so Paul was going considerably slower this time.

When his ride was done the pilot got out of the car, got down on his hands and knees and kissed the ground. When he got up he said, "I've felt some serious Gs in my life, but I've NEVER felt anything like that!! The lateral loads were amazing"

He had been an F4 jockey in 'Nam so I reckon he knew what he was talking about.

[munks]

I think you may be wrong and right at the same time - these designers were leaning heavily and employing the sort of people who put 747 Jumbo's thru to airforce fighters into the air, they knew exactly on paper what downforce they should be acheiving but having that actually happen on a racetrack probably brings your 10% into play as a variation on track.

A good point - I realize now that I had totally dismissed the possibility that they might actually calculate the downforce based on shape (CFD on slide rules ... well not quite, I suppose). I actually have no idea how advanced these equations and lookups were at the time - especially concerning those dang spinning wheels!

[pugfan]

A good point - I realize now that I had totally dismissed the possibility that they might actually calculate the downforce based on shape (CFD on slide rules ... well not quite, I suppose). I actually have no idea how advanced these equations and lookups were at the time - especially concerning those dang spinning wheels!

Lanchester came up with his circulation theory of lift before the turn of last century just by having a look at birds so there are some smart cookies around.

[Palmero]

Thanks for some of the stories shared in this thread, great stuff.

[mariner]

Reynard have just launched an entry to this list and it is a ROAD car

http://www.autocar.c...AllCars/251862/


Downforce three times its weight at 1200kg or over 2,500 lbs and all with a 180 bhp engine.

As the engine would probably limit the car to around 140 mph or so the downforce at the standardised 200 mph here should be well over 5,000lb apparently

Edited by mariner, 13 August 2010 - 07:59.

[Charles E Taylor]

Downforce? Negative Lift?




Consider the negative lift required to keep 10700kg on the ground at 1223kph.




Look Here





Charlie

[Tony Matthews]

Consider the negative lift required to keep 10700kg on the ground at 1223kph.

Surely the 'negative lift' only has to be slightly more than any lift - otherwise it's going to dig a trough in the salt. After that you only need super-downforce as a cornering aid.

[dosco]

Downforce? Negative Lift?

Consider the negative lift required to keep 10700kg on the ground at 1223kph.

Look Here

Charlie

I think I may have discussed this a couple of times on this forum.

I was stationed at Travis AFB in the mid 1990s and one day received a call (out of the blue) from Craig Breedlove's shop. They wanted to hire a life-support technician to install a breathing system for Craig in his contender "Spirit of America." I was invited to come to the shop in Suisun to talk with a couple of guys on the program and tour the vehicle. When I asked the crew chief about downforce control, he tells me the vehicle has fixed "tabs." I was appalled, and unfortunately not surprised when Craig rolled the vehicle during his trial runs.

I was informed the Thrust SSC, OTOH, has an active downforce control system ... there are load cells on the wheels and the t-tail is controlled by a computer to maintain a certaing amount of downforce on the wheels. No surprise that this was a deciding factor in successfully setting a new record.

Edited by dosco, 13 August 2010 - 15:11.

[Fat Boy]

I think I may have discussed this a couple of times on this forum.

I was stationed at Travis AFB in the mid 1990s and one day received a call (out of the blue) from Craig Breedlove's shop.

I saw the data from Craig's run (I think it came off an old Pi2 dash). It was amazing. When I first put it on my screen I didn't even see it. With the scaling that I was using it was just a vertical line. It only made sense after setting Max speed to, like, 800 mph. That guy was actually driving that thing. You could see throttle input (controlled fuel pressure) and everything. The 'pilot' of the Thrust was basically a monkey in the rocket. Breedlove was doing _everything_ to keep his car going. He lifted at around 600 mph. When asked why, he said it was to keep from going supersonic before the measured area. I don't know if that's just him being optimistic or reality, but I can tell you that the acceleration curve when he got back on it the gas (prior to the sudden right hand turn) was very steep. It was showing no sign of the acceleration slowing even at about 675mph when everything went oblong.

I've had drivers 'suck it up' to get in the car sometimes, say, after a bad crash on an oval. I've never had a driver get in a car that would take the balls that it took to get into that thing. Breedlove will forever have my respect.

[DaveW]

I was informed the Thrust SSC, OTOH, has an active downforce control system ... there are load cells on the wheels and the t-tail is controlled by a computer to maintain a certaing amount of downforce on the wheels. No surprise that this was a deciding factor in successfully setting a new record.

Apologies, but I don't think so. The original plan was to control rear ride height actively to maintain a fixed average contact patch load distribution. I modelled the vehicle & a trial control system & decided that, with (I recall) 5/8 inch front suspension travel & no wheel/tyre deflection to speak of, there was not much chance of reacting in time to a sudden change in aero before the front wheels were off the ground & the only way of keeping the thing under control was by inertia forces. I suggested, strongly, that they should fit controlled foreplanes, & demonstrated (by modelling) that the vehicle could be controlled in pitch & roll using those as emergency "motivators".

RN decided to plough on regardless &, as a result, I decided not to be involved. In the event, the initial active rear ride height control system proved to be inadequate (despite a 1 millisec response time). Andy Green was instrumental in finding the boundaries incrementally & recovering before the vehicle departed, & rear ride height was eventually "scheduled" open loop as a function of airspeed (or so I was told). No aerodynamic surfaces were controlled at any time.

There were other problems too. I was moved to describe it at one point as a supersonic dumper truck, courtesy of rear steered wheels. It was also flat bottomed. I have the utmost respect for Andy Green, because I think the vehicle would probably have killed almost any other driver (pilot).

[Fat Boy]

I have the utmost respect for Andy Green, because I think the vehicle would probably have killed almost any other driver (pilot).

Interesting. I guessed it to be a more sophisticated operation. It seems Mr. Green deserves the same respect as Mr. Breedlove.

Honestly, I think all of those guys are a little out of their gourd.

[dosco]

Apologies, but I don't think so. The original plan was to control rear ride height actively to maintain a fixed average contact patch load distribution. I modelled the vehicle & a trial control system & decided that, with (I recall) 5/8 inch front suspension travel & no wheel/tyre deflection to speak of, there was not much chance of reacting in time to a sudden change in aero before the front wheels were off the ground & the only way of keeping the thing under control was by inertia forces. I suggested, strongly, that they should fit controlled foreplanes, & demonstrated (by modelling) that the vehicle could be controlled in pitch & roll using those as emergency "motivators".

RN decided to plough on regardless &, as a result, I decided not to be involved. In the event, the initial active rear ride height control system proved to be inadequate (despite a 1 millisec response time). Andy Green was instrumental in finding the boundaries incrementally & recovering before the vehicle departed, & rear ride height was eventually "scheduled" open loop as a function of airspeed (or so I was told). No aerodynamic surfaces were controlled at any time.

There were other problems too. I was moved to describe it at one point as a supersonic dumper truck, courtesy of rear steered wheels. It was also flat bottomed. I have the utmost respect for Andy Green, because I think the vehicle would probably have killed almost any other driver (pilot).

Thanks much for the info, I am glad to learn more about the realities of the RN program. I too thought that RN's operation was more sophisticated than that ... too bad.

The Breedlove operation's program manager was a young guy that was rather ... ahem ... eccentric. During my short visit to the office/workshop he proceeded to explain to me that it was impossible to break the sound barrier on the ground because of a variety of technical issues. When I asked him why it was possible for rocket sleds used in military tests to routinely exceed M=1 he decided it was time for his afternoon bicycle ride to "maintain his energy levels." Breedlove's crew chief (a different guy) went on later to explain that a number of engineers brought on from CalTech, MIT, and a plethora of aerospace companies had clashed with this young guy and left.

The personalities involved are interesting, to say the least.

Edited by dosco, 13 August 2010 - 20:17.