10 replies to this topic

[P.Dron]

Does anyone know what the neutral-steer speed was at Montlhéry, before the installation of chicanes?

[BRG]

Oh, the relief....

 

I read this thread title as "Hands Off Montlhéry" and expected a sad tale of proposed housing developments

[P.Dron]

Oh, the relief....

 

I read this thread title as "Hands Off Montlhéry" and expected a sad tale of proposed housing developments

 

Alas, that is quite probable!

 

What interests me is that at MIRA, for example, neutral-steer speed round the three banked bends is 100mph and it is only above 120mph that it becomes challenging. At the Millbrook bowl, neutral speed is 120mph and it is usually only from 160mph that you have to work hard. Of course this varies, depending upon the car and the tyres. I am trying to put various Montlhéry records into perspective.

Edited by P.Dron, 16 April 2021 - 14:15.

[BRG]

Is there any correlation to the angle of the banking and the radius of the turn?  From memory, MIRA is pretty steep and tight  whereas Millbrook is a very gentle banking and a very large circle.  Montlhery is certainly quite steep.  

[P.Dron]

Is there any correlation to the angle of the banking and the radius of the turn?  From memory, MIRA is pretty steep and tight  whereas Millbrook is a very gentle banking and a very large circle.  Montlhery is certainly quite steep.  

 

Yes, quite. That is what I wonder about. The thing about Millbrook is that you can feel a progressive increase in lateral g, whereas at MIRA in a fast car you arrive at a bend at a higher speed than can be sustained. I think that the Montlhéry oval was a mixture of the two... Bring on the engineers!. 

Edited by P.Dron, 16 April 2021 - 21:01.

[Greg Locock]

MIRA's high speed circuit has killed quite a few people over the years - the transitions into the banked corners were poorly designed. Where I work the hands off speed is 180 kph, and you can drive around the entire loop using less than one finger's width of steering rim motion, on cruise control (ie no throttle steering). At Hethel the hairpin can be driven round without moving the steering wheel, just using the throttle, in an old Esprit, but I was never game to try that.

[mariner]

One sort of obvious  point is that most banked RACE tracks are tilted but flat  e.g NASCAR and Indy. That means only one speed will be hands off .

 

Most TEST tracks seem to be concave or parabolic so allow a wide variety of hands off speeds. I assume  that is for safety and to allow different vehicles  on test to overtake. Useful if you are MB and testing big trucks and SLR's I guess.

 

GM give an example of the weight transfer of a car running a 31 degree tilted flat  track at 190mph. I think this is representative of Daytona. The lateral weight transfer of NASCAR type car is about 1.25W which suggests quite a lot of steering input and tyre slip angle is required at 190 mph.

 

The full maths is in Milliken pages 685 to 690. Above crltical speed the car loads the outside wheels and requires positive steering angles to generate slip angles to counter the G load. Below critical speed the opposite is true.

 

In response to the Miilbrook problems designing the transitions is well established maths as it is critical for high speed rail lines where the track is "super elevated" as they call it - i.e banked. An article here  

 

https://web.engr.uky...y REES 2010.pdf

 

Incidentally although Brooklands was a curved or parabolic track it's designer Col. Holden aimed for  hands off speed of 120 mph. The big cars of the 1930's were up to 135 mph lap speeds so they ran very high and must have brutes to steer given the bumps. 

Edited by mariner, 17 April 2021 - 09:14.

[DogEarred]

Funnily enough, my last ever motor race was the Formula Ford 1600 event at Montlhery in 1984.

 

The chicanes were in use but such was the length of the banking that terminal velocity could be reached twice.

 

I remember testing lines during practice.

I tried keeping low initially, to make the 'shortest' route but it scrubbed off speed.

I tried going high initially, in order to have a 'swoop down' increase in speed at the end in order to make overtaking moves.

I tried letting the car take its natural line, which turned out to be about one third the way up the banking. I did try taking my hands off the wheel once, for a couple of seconds but it was not the speed that spooked me but the jumping about due to the bumpy old concrete!

 

We high geared the box, so I'd guess the top speed was touching 130 mph.

 

 

 

 

I came to the conclusion that the lines were a case of swings & roundabouts, so didn't make much difference to lap times.

[P.Dron]

Funnily enough, my last ever motor race was the Formula Ford 1600 event at Montlhery in 1984.

 

The chicanes were in use but such was the length of the banking that terminal velocity could be reached twice.

 

I remember testing lines during practice.

I tried keeping low initially, to make the 'shortest' route but it scrubbed off speed.

I tried going high initially, in order to have a 'swoop down' increase in speed at the end in order to make overtaking moves.

I tried letting the car take its natural line, which turned out to be about one third the way up the banking. I did try taking my hands off the wheel once, for a couple of seconds but it was not the speed that spooked me but the jumping about due to the bumpy old concrete!

 

We high geared the box, so I'd guess the top speed was touching 130 mph.

 

 

 

 

I came to the conclusion that the lines were a case of swings & roundabouts, so didn't make much difference to lap times.

 

Very interesting. Thank you.

[P.Dron]

MIRA's high speed circuit has killed quite a few people over the years - the transitions into the banked corners were poorly designed. Where I work the hands off speed is 180 kph, and you can drive around the entire loop using less than one finger's width of steering rim motion, on cruise control (ie no throttle steering). At Hethel the hairpin can be driven round without moving the steering wheel, just using the throttle, in an old Esprit, but I was never game to try that.

 

Have there been many fatalities on MIRA's triangular "high-speed" circuit? In  December 1980 I destroyed a Fuego there; I fell asleep at 80mph while doing steady-speed  fuel consumption tests. This was on a Monday, after a long drive from St Paul de Vence, initially over snowy/icy roads. I set a record by flattening 36 of the wooden posts. This was beaten shortly after when two Rolls-Royces were circulating in close formation. Part of the exhaust of the lead car fell off and got stuck in the front suspension of the following car, which crashed.

 

As far as I recall, no one had ever been killed at MIRA at that time, despite some dangerous objects, such as sand-filled oil barrels as corner markers on the aptly-named Number 2 circuit. I seem to remember a biker being killed at MIRA, but I do not think that there have been many deaths there..

Edited by P.Dron, 18 April 2021 - 13:23.

[Greg Locock]

A couple of vehicles shot off the top of the banked corners and rolled down the outside. Don't know much about it, but I was told, in the late 80s, it was loss of control on entry to the banked corner. Easy to do in the wet. We have Armco all around the tops of our banked corners, as we do a lot of high speed testing with max gvw trailers, which can be a bit of a handful, and also have to run 24 hour durabilities which leads to fatigue management problems.