willem
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posted on 13-8-2007 at 09:47
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Weight calculator explained!
L & G's
In juli in Alsdorf we've used the weightcalculator as some of you may have noticed. I can imaging that lots of people don't understand how this
exactly works and what the meaning of it all is.
In general it comes down to the following:
Differences in car specific dimensions (ie: spur, height and guidebase) will be translated (calculated) in a weight-handicap.
How does the formula work?
The dimensions of the car will be measured on 6 different locations. (Check the image on the weightcalculator page).
These measurements will be put into the following formulas: (All values in mm)
Average spur (aspur) = (Frontspur + Rearspur) / 2
Average height (aheight) = (Frontheight + Middleheight + Rearheight) / 3 (see image for exact locations)
Guidebase = Value measured from the rearaxle (Including the axle itself) onto the front of the guide in straight position.
Then the formula which calculates the weight handicap
Weight handicap = (aspur - refspur)/2 + (refheight - aheight) + (guidebase - refguidebase)/2
Obviously the first question would be. What is refspur, refheight and refguidebase?
Answer: Well........these are the reference values determined per event and are used in the formula as a base reference. They depend on the circuit,
car types and type of event we're racing.
For Alsdorf these values are:
Reference spur: 82 mm
Reference height: 45 mm
Reference guidebase: 130
Reference bodyweight: 50
Reference totalweight: 190
You can treat these values as a given fact so you don't need to worry about them!
Now back to the formula using an example:
Front spur = 83
Rear spur = 84
Front height = 31
Middle height = 46
Rear height = 38
Guidebase = 125
(Front spur + Rear spur) / 2 = 83,5
(Front height + Middle height + Rear height) / 3 = 38,333
Putting all the values into the main weight handicap formula will result in the following for the wieght handicap:
(83,5 - 82) / 2 + (45 - 38,333) + (125 - 130) / 2 = 4,91
So your handicap weight becomes 4,91 gramms.
This handicap weight wiil be added to the reference total weight which is: 190 gramms
Rounded off your total weight must be 195 gramms
Your body weight is calculated only on the spur and height measurements. The guidebase does NOT play a role in there. So your total body weight
becomes:
(83,5 - 82) / 2 + (45 - 38,333) = 7,4 gramms + reference body weight (50 gramms) = 57 gramms
Feel free to ask any question about it if it's not clear to you. Goal is to make the cars more equal in performance on the track.
Cheers
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willem
LMSadmin
Posts: 356
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Location: Netherlands
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posted on 13-8-2007 at 11:41
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Weight calculator in excel
For those who want to use the weight calculator offline, I've just created a simple excel sheet which does exactly the same thing. Bare in mind that
the reference values (in the top left of the sheet) may differ per event. for the Alsdorf short endurance I've filled them out with the correct
values.
Attachment: Weight-calculator.xls (27kb)
This file has been downloaded 1129 times
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Francesc
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Registered: 28-5-2002
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posted on 13-8-2007 at 18:29
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Hello Friends
The formula is ok in the concept, but i think that may be better in 3 points
1- The rear spur and the front spur is measured from the with of the body in these points, but i think it's better measured in the with of the axle.
If not, the wheel arches are also an important point to measure and to put in the formula.
2- The guidebase it's measured from the center of the rear axle to the front of the guide, but may be better to measure until the turn axle of the
guide, beacause this turn axle is who rules in the behavior of the car.
3-And to make it more acurate, another important size is the lenght from the center of the rear axle to the rear end of the car.
I hope this can help to make this formula better.
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willem
LMSadmin
Posts: 356
Registered: 5-11-1985
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posted on 14-8-2007 at 11:20
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In releation to your 3 points:
1) We use the bodywidth instead of the actual spur to prevent driving a narrow spur under a wide body
2) Techincally you're right and we already had much internal discussion about this. Fact is that it doesn't matter what you measure because it's
all relative and not absolute. From a measurement point of view it's much easier to measure from the read-axle onto the front of the guide.
3) The length of size from the rear-axle to the rear-end is in my opinion aloose thing. In other words we could measure lots and lots of more things
which does NOT make any difference in the overall picture. Again in other words: We could measure the curve of the body and put this into a fucntion
whcih translates this to coeeficient and then to gramms.
Cheers
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