203 replies to this topic

[Lee200]

I've often wondered too how accurate are the reported top speeds for various cars from years ago.  How was it measured?

Obviously, race cars did not have a calibrated speedometer so how did the designer/driver know how fast the car was going unless it was timed over a fixed distance.  An estimate could be made from the engine rpm as displayed on the tachometer and drivetrain ratios, but you'd still have to estimate the rolling radius of the tire.  Finally, there is always a certain amount of slip...the tire has to rotate faster than its ground speed in order to generate a force.  So even if all the other factors were precisely known, an estimate for tire slippage would be needed.

In GPL, the rear tire slip is about 10% at max speed...the tire is spinning about 10% faster than its speed across the ground.  So the car's speed is always lower than what the calculation from engine rpm, drivetrain ratio, and rolling radius would suggest.  I don't know what real world tire slippage is though.

[Border Reiver]

Presumably racing drivers also tended to exaggerate a bit too?

After all, there always was a lot of psychology, gamesmanship and bravado e.g. "but you are taking Fordwater flat aren't you?" or looking at an opponent's car on the grid then making a surprised face while looking at a tyre or suspension arm and then smiling, giving a little nod and then walking off!

I agree with Lee, unless these figures were independently measured then I'd only ever assume they are in the ball park, but most likely are an upper limit or bound on the true value and certainly not the average. Why would any team publicise true data so that the other teams knew what they had to beat? They'd obviously hype it up a bit to make the other teams try harder and perhaps over stretch themselves.

Rob

Edited by Border Reiver, Oct 15 2017 - 11:58 AM.

[StirlingMouse]

Your point is a good one, about teams exaggerating to mislead the opposition. When in the 1950s the Coventry Climax people decided not to make their eagerly awaited V8 Godiva engine available, this was mainly because they naively believed the exaggerated power outputs that were being - falsely - claimed by other manufacturers; sadly this decision was a major blow for Connaught and others who had to make do with inferior engines as a result. As regards top speeds, I notice that even in 1958 the very aerodynamic Vanwalls were reported as reaching 180mph on the very long (and, I believe, slightly downhill) straight at the back of Pescara, so maybe it's questionable whether even the best 1955 cars would have seen much more than 165, possibly 170mph on most tracks; however gearing will of course play a part, and that's an area where I still get very confused!

[Pete Gaimari]

A measured distance and the time it takes to do that distance will give you MPH.

[Michkov]

Pete Gaimari, on Oct 16 2017 - 09:01 AM, said:

A measured distance and the time it takes to do that distance will give you MPH.

That's average speed though. I'd stick with time, preferably sector times but that may be wishful thinking for the era in question

[MECH]

Maybe you can find someone who's willing to sit by with a stopwatch.
Just for historical correctness

[gliebzeit]

... or find someone like this.

 colin.jpg   84.38K   18 downloads

I learned about stopwatches here:

 slot-car-tracks-slot-car-racing.jpg   55.85K   23 downloads    watch.jpg   25.31K   19 downloads

Edited by gliebzeit, Oct 17 2017 - 08:16 AM.

[hagapito40]

So, we have a game that is based on lot of supositions, (like the 10% slip  that Lee points out) and the fact of course, that the game is a reduction...some times hilarious of the reality...and the first thing you argue when the numbers are not correct is..."those guy...Moss and Fangio overexagerate the top speed...only to get some chics..."

...ok

[Lee200]

I didn't know we were having an argument.  

[gliebzeit]

"those guy...Moss and Fangio over-exaggerate the top speed...only to get some chicks."

Well ...Moss, most definitely!

Attached Files

•  stirling.jpg   99.04K   37 downloads

[Lee200]

gliebzeit, on Oct 17 2017 - 12:14 PM, said:

"those guy...Moss and Fangio over-exaggerate the top speed...only to get some chicks."

Well ...Moss, most definitely!

Gotta love the cheeky old bastard.  

[Lord]

Lee200, on Oct 17 2017 - 02:02 PM, said:

gliebzeit, on Oct 17 2017 - 12:14 PM, said:

"those guy...Moss and Fangio over-exaggerate the top speed...only to get some chicks."

Well ...Moss, most definitely!

Gotta love the cheeky old bastard.  

"You can say I was certainly... heterosexual."
https://youtu.be/prv8t5hq9SQ?t=9m19s

Well, about the topic at hand, I don't mean to sound like the know-it-all here, but my engineering studies taught (and still teach) to me a thing or two about the correct way to make mods (at least physics wise):

1. Take all the data you can, even if it's from the year before: you can always derive the correct parameters from reading the source material accurately;
2. Focus on the cars first: since the main focus of simracing is, well, drive the cars, it's best to focus on the cars themselves first for the physics.
3. The continental european data for classic cars (pre-'70) is WRONG: this is a sad truth. When you encounter European cars, take it this way: if it's continental, chip away 7% to the power. This is because of the test beds we used to use in the continent, very prone to overextimating due to chafing in the power axis;
4. The top speed depends on context: always check, for any given season, where those top speeds have been achieved.
5. The track (and its AI) aren't 100% correct: They might be really close to be perfect, but there are some details someone can't take without exploring the site in person, giving a difference in both laptimes and racing line.

I hope I made some sense: if you wnat to add/correct, feel free

[Lee200]

Makes a lot of sense Lord and is exactly what the mod teams have done for years.  There's a lot of stuff floating around on the internet...some good and some not which should come as no surprise to anyone here.  So every source is scrutinized, compared to others, and tested to see if it passes the common sense test.  Unfortunately in a lot of cases, there just isn't any data available, but the mod teams are pretty good now at filling in the blanks.

It's never going be perfect as GPL itself isn't perfect either, but we've always done the best we can with the available data.

[gliebzeit]

Right on.

[Lord]

Lee200, on Oct 17 2017 - 06:10 PM, said:

Makes a lot of sense Lord and is exactly what the mod teams have done for years.  There's a lot of stuff floating around on the internet...some good and some not which should come as no surprise to anyone here.  So every source is scrutinized, compared to others, and tested to see if it passes the common sense test.  Unfortunately in a lot of cases, there just isn't any data available, but the mod teams are pretty good now at filling in the blanks.

It's never going be perfect as GPL itself isn't perfect either, but we've always done the best we can with the available data.

That's great to hear, at least now I know that I'm not off the mark
About the data, I've had my fair share of... "fecal matter" when checking it from the 'Net: some of it is wildly off the marks that it's downright unbelievable. Personally I consider this a reason enough to trust (and cross-check) the old-fashioned books written by reputable sources and "History of Grand Prix Engines" website. It's fairly easy to check them with one another, too bad that the best books are (most of the times) or have been long out of print, so it can happen that you have to pay a pretty penny on Ebay/Abebooks to check that info.