Effect of Weight on Lap Times
Discussion
Using your numbers, thats the equivalent to 3.84bhp drop. but I'm pretty sure that there is a load more involved than that. Where abouts the extra weight is placed will effect(to a small degree) the cornering etc. The wieght placement might benefit the cornering if its placed in the right place. 
but I'm not an expert.
That didnt answer your question though did it? Ok, I'd do like this; I'd work out the extra weight as a percentage of the original. thats how I figured out the equivalent power drop,by using the power to weight ratio. I guess it could work on lap times as a rough estimate. 10kg is 1/65 of 650kg. If it effects your power to weight ratio by that amount it equals 1/65 of your power, which is 3.84bhp. Take a lap time with 650bhp then the extra wieght should effect the lap time by 1/65. So a 60 seconds lap timewould be effected by 0.01538 of a minute or 0.923 seconds. But thats just the maths. In the real world it wouldnt be that simple!
but I'm not an expert.
Edited by Galileo on Friday 20th October 17:56
That didnt answer your question though did it? Ok, I'd do like this; I'd work out the extra weight as a percentage of the original. thats how I figured out the equivalent power drop,by using the power to weight ratio. I guess it could work on lap times as a rough estimate. 10kg is 1/65 of 650kg. If it effects your power to weight ratio by that amount it equals 1/65 of your power, which is 3.84bhp. Take a lap time with 650bhp then the extra wieght should effect the lap time by 1/65. So a 60 seconds lap timewould be effected by 0.01538 of a minute or 0.923 seconds. But thats just the maths. In the real world it wouldnt be that simple!
Edited by Galileo on Friday 20th October 18:56
Galileo said:
But thats just the maths. In the real world it wouldnt be that simple!
I couldn't tell you what the answer is, but the relationship certainly is not linear. It is quite common in race series for winning cars to be given a weight penalty in order to tighten the competition.
In some series in which the cars weigh in the area of 1100-1300 kg, the weight penalty can be 50 kg or more.
On 1200 kg, 50 would be >4.1%, which for a reference lap time of 2:00 is equivalent to more than 6 seconds a lap.
We can also look at F1 in which the car with driver weighs 600 kg (and for relative purposes effectively weighs less insofar as the car will typically have >80 kg of that 600 in optimised ballast). Last year the cars had >900 bhp.
Relate that to, say, a 996 Cup car. The Cup car will weigh twice as much, have half the horsepower, and on the same circuit the Cup car's lap time will be maybe 50% longer than the F1 car's.
Just within F1, a full tank on a typical circuit seems to add something like 1.5 sec/lap, or 1.5%, to one's time (I'm ignoring the benefit of fresh tyres v used ones, if I may).
If the typical re-fueled load is maybe 75 litres, that's about 56 kg, or 9% weight gain over 600.
9% weight gain is obviously a lot more than the 1.5% increase in lap time.
Edited by flemke on Friday 20th October 23:28
Rob Croydon said:
Has anyone got any rough formula for the effect of weight on a racing lap time.
In particular the effect of 10kg on a CN class Juno which is 650kg car with 250bhp at say a circuit like Sneterton?
In particular the effect of 10kg on a CN class Juno which is 650kg car with 250bhp at say a circuit like Sneterton?
We have a handicap system in the TVRCC Speed Championship which is based on power-to-weight ratio. Our results show that for the particular circuits, cars and drivers in our championship there is a strong logarithmic relationship between power-to-weight and performance, and I have worked out the parameters for this relationship over about eight years worth of results.
Putting your power/weight figures into our handicap system gives you a handicap factor of 0.978 before the weight change, and 0.980 afterwards. In other words, the handicap suggests that the change would reduce the lap time by roughly 0.2%. Given that Snetterton is a fast circuit where drag may be more important, the gains may be rather less than that.
Edited by GreenV8S on Saturday 21st October 01:06
GreenV8S said:
We have a handicap system in the TVRCC Speed Championship ...
Given that the effect of weight on acceleration, braking, cornering, etc is so complicated, a successful handicap system (based on practical experience) is going to give you the best result, at least for rough & ready, "is it worth it" guesstimates.
GreenV8s figures would be of the order of 0.25 secs, on a 100sec lap of Snett. I would suggest that's probably a little bit optimistic for your Juno, but for an argument you could probably work from:
- Removing 10kg would save you an easy, and free, 0.1secs every lap, perhaps more - that's 1.5s in a typical 15-lapper
- Or, adding 10kg could be costing you up to 0.25sec
In other words, it's worth keeping the weight down if you can. Saving 10kg even on a 650kg car (N.B. do you mean 750kg with driver?) will make an identifiable difference.
Many, many years ago I read an article somewhere about Derek Gardner (the original Tyrrell F1 designer - cars 001 to P34)and I am sure that he had done some calculations about the impact that the weight added to a car by painting had on lap times (think how heavy a tin of paint is). The upshot was that Gardner insisted that the paint coating on the car was a thin as possible and that it was not overpainted and overpainted when repairs were done - instead the cars had to be stripped back to bare metal and the painting started over again. Gardner wouldf have had the cars race in the aluminium I think, but the sponsors wouldn't!! Sorry I can't remember the details but Gardner is still around somewhere.
[quote=andy97]Gardner wouldf have had the cars race in the aluminium I think, but the sponsors wouldn't!! quote]
Sounds like he took a leaf out of Mercedes' book. AFAIK, the reason they were called the 'Silver Arrows' is because Alfred Neubauer (sp?) insisted that the cars were not painted, to save weight. If you can imaging the size of those old Merc racers in comparison to a modern single seater they would probably take twice as much paint on the bodywork!
Sounds like he took a leaf out of Mercedes' book. AFAIK, the reason they were called the 'Silver Arrows' is because Alfred Neubauer (sp?) insisted that the cars were not painted, to save weight. If you can imaging the size of those old Merc racers in comparison to a modern single seater they would probably take twice as much paint on the bodywork!
GarrettMacD said:
andy97 said:
Gardner wouldf have had the cars race in the aluminium I think, but the sponsors wouldn't!!
Sounds like he took a leaf out of Mercedes' book. AFAIK, the reason they were called the 'Silver Arrows' is because Alfred Neubauer (sp?) insisted that the cars were not painted, to save weight.
And I think that was to get under the weight regulations set out in 1932 for the new international racing formula. The regulations stated that the weight of the racing car may not exceed 750 kg excluding fuel, water, grease, oil and tyres but not the wheels.
Edited by FourWheelDrift on Sunday 22 October 10:44
jacobyte said:
I seem to recall that Colin Chapman's general rule of thumb was that 10lb equates to 0.1 seconds a lap.
I'm trying to Google for a source to verify that. Anyone?
I'm trying to Google for a source to verify that. Anyone?
Thanks for providing me with an excellent excuse - my FVL is 80-90lb over the weight limit. Pity that I am usually several seconds away from the front of the grid...must be me then!
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