Back in the days of August 2022, when the deer and the antelope played and the skies were not cloudy all day (seems like a lifetime ago, doesn’t it!), David and I met at the Monterey Historic Races at Laguna Seca Raceway. As we were walking around the garages, we came across the Team Lotus tent where they had two very interesting Formula One cars: A Lotus 78 from 1977 and a Lotus 91 from 1982. Only five years apart, these cars couldn’t have been more different, with technology that worked so well it was eventually outright banned from the series.
If you’re so inclined, above is a video walk-around of each of the cars.
Lotus 78
After a series of unsuccessful attempts to replace the brilliant but aging Lotus 72 chassis, Colin Chapman and his team set out in 1976 to design and build what was to become a revolutionary new Formula 1 car, the Lotus 78. Chapman, having recently studied the de Havilland Mosquito fighter bomber, figured that an inverted airplane wing would be a perfect addition to a race car and would serve to better plant the car to the road. He asked his chief engineer Tony Rudd to look into it and Rudd, along with chief designer Ralph Bellamy, engineer Martin Ogilvie, and aerodynamicist Peter Wright, set about figuring out how to incorporate the concept of an upside-down airplane wing into the body of a race car. Rudd and Wright both previously worked at BRM and had considered the idea then but lack of funding at BRM meant the idea never got developed.
After several wind tunnel tests, and tweaks to the design, the team discovered what became known as “ground effects,” which uses the same basic principle as an airplane wing. Airplane wings work thanks to the groundbreaking discovery in 1738 by Swiss mathematician and physicist Daniel Bernoulli that as a fluid, like air, flows faster and faster, its pressure drops (our aerodynamicist has written all about that concept). This idea would later be used to develop the first airplane wing. The idea of an airplane wing is that as the wing moves through the air, it forces some of the air to flow over the top surface and some to flow over the bottom surface, but because the top surface is curved upward, the air flowing over the top surface has farther to travel and therefore must move faster. The faster flow reduces the pressure so that there is now a higher pressure in the air flowing over the bottom surface than there is in the air flowing over the top surface. This pressure difference pushes the wing upward and hence we have flight.
Rud, Wright, and Chapman realized that if you turned this idea upside-down, then instead of getting lift, you could get downforce which would help push the car into the road and increase traction. Increasing traction would mean harder braking and faster cornering, both good things when it comes to race cars.
In their wind tunnel tests, the team discovered that they were absolutely right in their thinking, but they also discovered something far more important. They found out that if you placed this upside down wing close to the ground, the effect was intensified. Here’s how it worked:
After more experimentation, they found that the impact of the air expansion space under the car was by far the dominant factor in creating downforce. As the air flowed under the body, it got trapped between the underside and the ground and as the air flowed towards the rear of the car, it had an ever-increasing space to fill — see the air expansion space in the image above. Since the same amount of air now had to fill a larger volume, its pressure dropped and sucked the car down. Note that the side pods didn’t have to look like upside down wings, they just had to have that shape on the underside. Like this:
What they had discovered was the effect of the ground, or “ground effect.”
The new car ran its first race at the beginning of 1977 and went on to dominate the field, winning five races that season. Of course, now that the cat was out of the bag, everyone jumped on the bandwagon and Lotus had to continue to develop the idea to stay competitive.
As the year went by, further development of ground effects led to the Lotus 91.
Lotus 91
The Lotus 91 was developed for the 1982 Formula 1 season and included some minor improvements a one major one. Colin Chapman spent a considerable time looking into composite materials and made the decision to build the new car from carbon fiber and Kevlar. Lotus needed the lighter weight materials to be competitive against the faster turbo powered cars and the 91 became only the second car, after the McLaren MP4/1, to use composites. The results speak for themselves with several podium finishes that season and a win at the Osterreichring.
Another feature was the now full-length ground effects extending all the way to the rear of the car:
Unfortunately, the full-length ground effects made the car very pitch sensitive, which led the team to develop the first active suspension system for the subsequent Lotus 92.
The idea worked a little too well though, so 1982 would be the last year for ground effects as they were banned for the 1983 season.
Sorry Huibert,this one is a bit clumsy.Obviously you were trying to make it brief and interesting but the historical errors bring it down
I’m surprised no one has mentioned one of the key advantages of utilizing ground effects to achieve downforce rather than wings/spoilers/lips/ect.
That being, ground effects is a way to add downforce without significantly adversely impacting the drag coefficient of a car. This advancement allows one to make a slippery streamliner that has net downforce, rather than net lift.
The modern Peugeot 9X8 was designed to use ground effects rather than a wing in order to allow reduced drag vs its competition, while still maintaining adequate downforce.
“…figured that an inverted airplane wing would be a perfect addition to a race car and would serve to better plant the car to the road.”
They had already done that, hence the wings mounted to the front and back in previous years. What was new was mounting them amidship, then taking it even further by turning much of the body into a wing.
when ground effect was re -introduced to f1 last year, it seems that adrian newey was the only designer who remembered the bouncing that ground effect can cause.
that’s why redbull is killing it imho.
when ground effect sucks car lower to ground, the airflow can stall, releasing the aero downforce, letting springs raise ride height, then ground effect sucks chassis lower and the cycle repeats.
the in car videos of first half of last season (especially the mercedes and ferrari) shows the violence of that ~5Hz (?) up/down banging.
dunno how the drivers could see.
Driver61′ YT channel had a good video about Newey a couple weeks ago. (https://www.youtube.com/watch?v=zUYprGdcTSg&t=2s)
It doesn’t seem very shocking that the team who’s designer had grond effect figured-out 40 years ago would be dominating now…
good video, thx.
ya AD is pretty clearly a genius. as evidence, consider that he doesn’t use CAD, just his trusty 2d drafting board to translate the vision in his head into a format his staff can convert into cad files for manufacture.
his autobiography “how to build a car” is good.
For ground effects to really work, the distance between the ground and the underside of the car needs to be maintained and strictly controlled. This means very stiff suspensions. Not ideal for all the other things a suspension has to do!
yes, Sensei.
the rb19 is reported to be able to run closer to the ground due to trick anti-dive/anti-squat pitch-control suspension and
strakes, etc. to control vortices to seal the edges of the floor without a skirt.
the inter-connected-ness of all these elements and systems to produce performance is fascinating to me.
thank you for your wrenchineering articles, i enjoy learning from you.
Yep, there’s a video on YouTube of Alan Jones testing a Williams with no suspension. Lotus did a lot of work developing active suspension, and Nigel Mansell did most of the test work, which is one of the reasons he was so good in the actively suspended Williams FW14, as he had a complete understanding of how to get the best from it.
Several years ago, I was watching an IndyCar race and noticed one of the cars in particular was bouncing/porpoising quite a bit. I have since read that the IndyCars, because they are essentially identical, are differentiated largely by shock absorber development. For example, Penske and Ganassi spend a bunch more time and $$ on shocks than smaller teams like Foyt..Just spitballing here because I’m not an engineer…Is it possible the RedBull advantage is as much a function of its shocks and suspension as its aerodynamics?
Throughout the six minute video:
David looks completely befuddled as he can’t figure out where the driveshaft is that goes to the front wheels and how come there’s no rust holes on these 40+ year old vehicles.
Hehe.
Why don’t F1 bring back active suspension? It would allow ground effect to go back to working properly again and get that close battling that the fans want, and I don’t see how it would lead to unfair advantage, it’s a pretty mastered technology in road cars.
I’d rather they bring back refueling instead tire longevity non racing.
iirc active suspension was banned because of safety (ref zannardi at spa) and concern that driver aids would shadow driver skill ( the same reason f1 does not permit abs or esc).
Active suspension would not necessarily mean ground effects could work again. For ground effects to work, the distance between the underside and the ground needs to be strictly maintained. This means the suspension just has to be very stiff which is not ideal for all the other things it has to do.
I’ve been curious about this and you might have some insight. Would some variant of the now-banned inerters do a great deal in solving the porpoising issue? It seems like they’d be able to be tuned to attenuate the frequency of the oscillations.
BTW, extremely poor wording on my part. I meant to say attenuate the amplitude of the oscillations at the porpoising frequency…
That’s the benefit of active suspension, it allows the ride height to be constant at all times.
This is why the underside of an F1 car is the most scrutinized part.
Ugh. “The idea of an airplane wing is that as the wing moves through the air, it forces some of the air to flow over the top surface and some to flow over the bottom surface, but because the top surface is curved upward, the air flowing over the top surface has farther to travel and therefore must move faster.”
It’s time for this explanation of lift to die. There is absolutely no reason that a divided air stream needs to cross a partition in the same amount of time on both sides, and pretty good evidence that it doesn’t.
http://amasci.com/wing/airfoil.html
Thank you! Hydrofoil wing sections are identical to airplane wing sections a lot of the time. So they work by putting a vacuum in the water? I don’t think so.
To be fair, this article doesn’t actually say that the two air streams must cross in the same amount of time – only that the upper air stream moves faster, a fact which William Beaty acknowledges in the piece you reference. Beaty also says that the Bernoulli explanation actually does explain 100% of lift. His major beef is that the Bernoulli explanation has some major issues which don’t get discussed and the Newtonian model (along with Coanda, circulation, flow-turning, and 3D vortex shedding) get marginalized. Beaty’s other point is that even the standard Bernoulli explanation is often misrepresented which, as far as I can tell, did not happen here.
My objection is to the, “the air flowing over the top surface has farther to travel and therefore must move faster,” line. Which is just another way of saying that the two air streams must travel in the same amount of time.
Perhaps, then, your real contention is with the word “therefore” – there is nothing misleading (or incompatible with Newton and the Attack Angle model) if you said “the air flowing over the top surface has farther to travel yet moves faster.” That is borne out by the mathematical equations based on an infinite wing and by empirical studies of real wings. If so, I would offer that aerodynamics is undeniably complex and even though he threw out the grade-school explanation everyone is most comfortable with, perhaps we could give Huibert a pass for not covering all of its intricacies in a 1,000 word post.
I’d be okay with, “The air over the top of the wing flows faster”–just not with the implication that this is *because* it has farther to travel.
Yeah that’s not the most accurate way to explain it. Even with a symetric profile (i.e. same distance to travel on both sides) you can get lift. Hell, even a flat plank can give you lift!
The easiest way to explain this to me is using the air stream momentum. A flat plank with a given angle of attack will deviate the air stream downward, creating a vertical component to it’s speed where there was none.
That momentum had been created by a force (the wing pushes on the air) and Newton’s third law (for every action there’s an opposite reaction) implies there’s an opposite force acting on the wing.
Therefore, if the air goes down, the wing goes up. That’s what you were doing as a kid when you put your hand out the window of the moving car.
PS: I’m glad to see Huibert didn’t do a 5000 words article on this car otherwise I don’t know what’s my added value here!
And it was sponsored by cigarettes and pornography. The golden years of racing.
I’m not sure Penthouse would even qualify as porn in today’s world. It was pretty tame and you could barely see through the Vaseline on the lens.
Yeah, but back then it was definitely naughtier than Playboy…or so I am told…
You were told correctly. The simple explanation was the women in Playboy represented “the girl next door” while Penthouse models were “the slutty girl next door.”
At least in my college days, a Playboy subscription was a rite of passage whereas picking up Penthouse was for perverts…
Also, the articles in Playboy were better…
There were no articles in Penthouse, unless Forum counts. At least that’s my memory.
Here’s a few from Playboy:
https://thehundreds.com/blogs/content/reading-playboy-for-the-articles-13-must-read-journalism-literature-pieces-from-playboy-magazine
Here’s the quick look up for the same search using Penthouse instead of Playboy:
https://www.rocksbackpages.com/Library/Publication/penthouse
I’m kind of interested to read some of those actually.
Yeah, “on the lens.”
one short of the vice-trifecta.
dunno if surtees or hesketh ever achieved the trifecta.
Imagine ANY magazine making enough money that they could sponsor an F1 team.
Or other mags sponsoring a team…
“And Andretti makes the pass in the Gigantic Asses Lotus! Splendid!”
Of course Mark Martin (IIRC) used to drive the Viagra-branded stock car.
“Martin’s making good progress through the field. Let’s see if he can keep it up after the caution.”
Dear Penthouse,
I never thought the stories were true, but here’s what happened to me…
so how do these two cars differ from the lotus 79 which is on iracing
The 1977 Lotus 78 came 1 year before the 1978 Lotus 79 (which won the championship with Mario Andretti)
The history of F1 technology is interesting in those early years. Some giant leaps moved things forward.