Vroom. . .

[andys]

I have a little salt flat experience. If 200MPH was as easy as gears and a big powerful motor, the 200MPH club would be a very crowded place......but it isn't. There is a surprising amount of motor and aero tuning that must take place in order to achieve that result. You must aero balance the car and get traction, as spinning the tires with big HP at that speed is well.....you get the picture. It's not as easy as it might seem.

I think the impressive thing about the GT40's of the '60's era WAS their ability to achieve 200+ at a place like Le Mans with a roadrace setup and an endurance (read de-tuned for longevity) motor. I'll continue to remain very impressed.

Andy

 

Mike,

I believe drag goes up according to a square law. I heard it on a program recently and it sounds likely but then the actual shape/effect of the car at speed must be an issue so its probably more complicated. Anyway, you need about 4 times the power to get to 200mph as to get to 100mph.

100mph should be possible with 100 bhp (my old Ford Anglia would do 105mph on 100bhp before the valves started bouncing, so a low drag GT40 certainly should). I think 450 bhp would be marginal to see 200mph. Driveline losses are not linear but become a lower percentage at higher powers (I believe).

The gearing on my GTD gives nominally 192 at 6,000 rpm (rev limited) with only about 350bhp I would never get there myself!

 

[Brett James-McCall]

Dave,
Remember its got to be vehicle speed, not dial speed. There is an error factor built into most dials, if I remember correctly the Focus is about 6%.

Brett

 

[ QUOTE ]
I think the impressive thing about the GT40's of the '60's era WAS their ability to achieve 200+ at a place like Le Mans with a roadrace setup and an endurance (read de-tuned for longevity) motor. I'll continue to remain very impressed.

[/ QUOTE ]

Indeed impressive, though there really is no reason to go 200mph. Talking about downforce and lift and what not--this is all understood. How did these cars do it? Many replicas can probably do it, but I guess what I was wondering is if you just need a crazed fellow flooring the gas pedal? That is to say, back in the sixties, racing was much more dangerous. And 1075 could go 200+mph with Ickx, that car having just near 500hp, down the smoky, foggy, windy, hot, cold Mulsanne straight over and over again. Continue interesting comments.

 

[ QUOTE ]
I think the impressive thing about the GT40's of the '60's era WAS their ability to achieve 200+ at a place like Le Mans with a roadrace setup and an endurance (read de-tuned for longevity) motor. I'll continue to remain very impressed.

[/ QUOTE ]

Correct me if I'm wrong, but I think the GT40 was record at 203 or 206 mph at Le Mans.... Good radar....

I think I read this on historic book.....

EG

 

[Mike Dozier]

Again... I apologize for not recalling the source, however
my understanding is that the GT40 is NOT a low drag car.
In fact most cars on the road today are lower drag.
Of course most cars today are shapeless clones...

MikeD

 

[Paul Thompson 'Hooligan']

Hi Malc + all

I remember that day well at Upper Heyford Aerodrome - we had allowed approx 500 yds to slow down, which seemed a lot beforehand, however, at the 176Mph Roy reached, you are covering some 85 yards per second so you don't want to brake late!! but space was a problem, not power as the car was pulling like a train at 170+.

Roys car seemed very stable but was slightly affected by crosswinds where one runway crossed another. Speed was from the onboard datalogging, picking up from the front near side wheel and cross checked against a speed trap at Brighton speed trials.

We're still up for the 200MPH barrier (and the sub 12s qtr) so next year should be fun.

We have not been to Bruntingthorpe....anyone here have experience??

 

[Gary Gibbs]

Drag force is proportional to V^2. But power required is Force times velocity. Thus the power required to overcome drag is proportional to V^3. Thus to double the speed takes 8 times the power.

Also the GT40 has a average drag coefficient, Cd; however, the total drag force (and resultant HP) requires that you multiply the Cd times the frontal area which is small for a GT40.

Also many of the aero tricks of today can be applied to the GT40 just as Ford has done with the new GT. They added a front splitter and a rear diffuser to their flat bottom GT and have reported reasonable downforce (not lift). This can all be tried with the current GT40's without severly hurting the beauty of the GT40.

 

[Max Walter]

Paul,

Maybe you should speak to Dick Townsend about Bruntingthorpe.

Max

 

Hi all

Quote from Goodyear regarding their Blue streak tires and the 1966 LeMans MK11 cars

The 2900lb GT40 Mk11 fitted with 427cid, 500bhp big block cars were exclusively designed to handle Le Mans and the infamous Mulsanne straight, a flat five kilometre's of country road. Here the cars would get up into high gear, winding up to close to 225mph. At that speed, the space between hartbeats is 330 feet. The tires would grab the track, turning 2700 times a minute, from there the cars would slow to 36 mph to take the Mulsanne corner. The tires and brakes would work together to dissipate over 4,000,000 foot/pounds of kinetic energy. The vented discs would glow at a temperature of 1500 degrees. Brake fluid would begin to boil. and it happened every lap for 24 hours.

It makes you think
Regards
Chris

 

Chris almost hit the nail on the head. How did these awesome machines do it though?! They didn't have fancy computers and ground effects and all this other modern day crap, but they did go 200mph over and over again and then brake for the Mulsanne corner, which is basically a 30mph u-turn. It's insane! It is exciting to think what it was like to drive a GT40 MK II with its Kar Kraft 4-speed. It's like, "Oh S---, I am going 95mph. . .maybe I should shift to second!" HA HA! I read another post and seems there are several GT40 replicas that can hit 200mph. I won't be the one to do it/ubbthreads/images/graemlins/grin.gif Have a nice day all.

 

[andys]

The lack of computers and sensors simply meant that information was gathered through testing..... with some brave souls out there, and some that didn't live through it. I will remind you however, that they've been doing this sort of thing at the salt flats for many years and there was some knowlege in how to go fast with low areo drag winglets, and so on. I thought that the body for the GT40 was shaped by Ford and tested in a wind tunnel; am I wrong about that? Maybe one of the later models? Also, under car flow wasn't being managed as it is with today's cars. I have done a small bit of sports car testing using temporary aero devices during track test days. It was quite a learning experience, as some devices made for some pretty dramatic differences in behavior (some quite scarey, in fact).

This discussion brought to mind a 24 Hours of Le Mans race televised on ABC's Wide World of Sports back around '67 or '68. Please forgive me for not knowing better, but it was a race won by a GT40 in the rain as I recall (It's ok, please chime in and rake me, aged memory loss is an ugly thing!). Little did I know at the time (as a young college student), that I was watching history in the making!

Andy

 

Those pictures of a Mercedes doing back flips 30 feet in the air from Le Mans a couple years ago on the Mulsanne straight should serve as a warning to anyone about what happens when good aerodynamics suddenly go very very bad...

 

[Jim Glickenhaus]

It's interesting to note that the MK-IV's did use computers.
On LeMans test days they gathered data from several sensors and recorded it on a reel to reel tape recorder. They imputed it into a mainframe and used a map of LeMans broken down into very small segments to come up with rpms, gearing, and shift points. They ran the 24 of LeMans on a dyno and gave these specs and rev limits to the teams. The teams modified them slightly but the data worked. I have that Dyno/computer/map on my wall. It's a bit of history. At night when I look into my garage at J6 I can hear the whispers of converting 4 million ft/lbs of speed into heat...