In Australia 0-100 has been the new o-60 since we went metric !

BTW spoolers,all this bollocks about dancing on the pedals is irrelevant in the case in question as there is no hesitation moment in the race to 100mph,there is no opportunity to use the brake pedal or the Lotus just gets further ahead !

Actually we started talking about a rolling start (ie steady 60 mph then floor it) after somebody posted the following which seems to suggest precisely that - but maybe he didn't mean that at all. What do you think he mean't Johnny?

Where did that Lotus come from? F**k those things can go! One moment we have a Porsche racing a McLaren then suddenly a Lotus appears then walks away from them.

And thus is the car traction limited, hence the necessity for launch control. As I said. The launch control would serve little purpose otherwise.



I wouldn't. 60 mph is the bottom of second gear where the vehicle is still traction-limited. The strategy would be more useful in, say, a top-gear roll-on test.

You are absolutely correct for the purposes of normal discussion. Loaded tire radius does not vary enough with speed to affect, say, speedometer accuracy, or acceleration tests as proposed at the top of the thread.

But drilling down a bit deeper for the purposes of this discussion... tire mfg'er specification table vs. actual loaded tire radius are not necessarily the same due to variations in sidewall compression. Can be back-checked by inflating the tires to desired pressure, drawing a chalk line on the sidewall, rolling the vehicle ten tire revolutions and dividing by ten. Forget aero loading in road cars <120 mph. Insignificant. However, tire circumference does grow a tiny bit, both with speed and over the life of the tire. Again, not enough to affect speedo accuracy or accel times, but possibly enough to affect low-tire warning systems based on ABS wheel speed inputs, so a little algorithm is written into the software to compensate for it.

I beg to differ. While I do not know if the launch control in the new 911 has some form of traction control in it (I guess it does), on my car launch control's only purpose is to build up boost before "launching" the car... no traction control or ESP is present.. You just floor it, it stops at 5000 and 0.9 bar boost... then you just drop the clutch and hang on..




again, depending on the vehicle, tyres and surface.. I would not say all of them are traction limited.. Otherwise I agree, turbo cars are laggy, especially at low RPM, even around max torque point (which is usually set so low you do not experience it without unnecessarily loading up the car in too high a gear..), but this is most evidend if you drive at constant speed and then floor it.. On a normal B road scenario, where you are on and off the throttle all the time, various anti lag systems can be in effect and the turbo lag is not evident all that much.. (be it full bang bang race antilag or mild street ones..)

Yeah magoo. I always ask someone who denies the existence of centrifugal force, what the feeling is in their arm as they throw the hammer/ bowl a ball. Centripetal my ass.

Actually i had a very funny argument once with some clueless noob, who refused to understand that tension is not really a force vector (as it points both ways), the 5 bob term is tensor.

I'll throw this one out one more time then I'm a spectattor again...

I undestand tire growth...the rear tires of a dragster being an extreme example. But why can't we have both tire growth and defelction at the contact patch? If centrifugal force can expand a tire why can't aero at some point - 150mph? - push a tire down so far as to cause it to flatten and reduce gearing? I also think I understand this may be particular to very specific tire construction.

I don't have a religious belief about it either way but on the other hand, neither do I have any problem with "imaginary" i.e. conceptual forces. So what. Aren't they all, really? Once they have the Large Hadron Collider up and running they are going to disappear the universe anyway, so BFD.

This just in. Latest conjectural depiction of the Higgs Bosun:

I knew as I was typing 'centripetal acceleration' there was going to be a balls up about it. I almost put "(centrifugal force)" after it, but figured that'd start just as many problems. I chose my words carefully, and they are accurate.

So, Nerds, How about this. The tire stretches out 'cause it's spinnin' really bloody fast.

Which ship was he on?

Strange, but the Higgs Boson that I keep in a jar has only got six nodules, not eight. Have I been the victim of fraud?

Yep, you can't win. If you wrote "centrifugal" someone would correct you for that. It's all in fun. This thread jumped its rails a while back.

It's decaying, throw it out.

Thanks. I know you realize that I didn't mean that tyres don't move at all, but meb was making them sound like spong-rubber bagels. Dragster tyres are very different in aspect ratio and probably construction, for the very purpose of not only gripping but changing in diameter.

When Peter Wright was researching for 'Formula One Technology' he said the tyre companies were the most reticent, more on compounds than construction, but loath to give anything away.

I think the modern tyre is a masterpeice of development in every aspect - and as a consequence, ignored by the average motorist.

PS. I don't know what the half-life of a Higgs Boson is, but I think I'll hang on to it for a while and see what happens.

boom! boom! both barrels i'm one dead clay pigeon. I want a lawyer now please.

Er - no reason at all. You are correct.

You can calculate the half-life of your particular Higgs Boson. How long has it taken to decay from 8 nodules to 6? Multiply your answer by 2.40942084. Bingo - you have the half-life.

(Now I must go and try to get a whole-one.)

Yea! I want my cookie now...

How about a Higgs Boson, 75% complete, a half life, thanks to gg, of 1214.34873034 hours - assuming eight nodules is 'complete' and keeping it under the stairs in a jar doesn't affect this figure - but I suppose you'd rather have a cookie...

(Life that is)

Under the stairs is occupied by a small wine collection...will half life exposure affect the wine?

It will double the alcohol content of the wine every 4.5 billion years - worth waiting for!

...but if I sit with the wine will it double my life every 4.5 billion years?

The Higgs Boson has a reverse effect on 'umans, it is unlikely you will see out a seco...

Having started this thread may I now expalin that I had an ulterior motive in asking the original question as it relates to my "toy" project car. this has a kerb weight of 1030kg and runs a 7.8 litre chevy which has 620 bhp at 6,000 rpm on dyno pipes. At the same set up there is 580 to 599 f/lbs of torque from 4,000 rpm to 5,000 rpm falling to 544 at 6,000 rpm.. In practice I have to use Supertrapp mufflers on the road which costs about 80 bhp. So if I just pro rate the torque it has 507 ft/lbs at 4,000, 522 at 5,100 and 474 ft/lbs at 6,000.

It runs a Muncie M -22 which has a 1.64 second gear with 1.28 for 3rd, the diff is 3.09. It so happens that the circumference of the rear wheels is 24.7 ins which with deflection is a radius of about one foot. So calculating the available thrust at the rear wheels in kg gives between 1,100 kg and 1,200 kg in the speed range of 58mph to 85 mph ( i.e from 4,000 to 6,000 rpm in second). I am ignoring trans. losses for simplicity.

Now the static laden rear weight is 624kg and and if you assume the Kumho track tires can get 1.2g longtitudinial grip and allowing for dynamic weight transfer the dynamic
vertical load on the rear wheels is about 874kg. With 1,100 kg of available thrust the predicted result is wheelspin.

The observed real world result - - wheelspin!

In third gear from 58 to 85 mph the calculation is about 900kg available thrust versus 874kg vertical rear wheel looad so - no wheelspin!

So I have three choices

1) use third gear from 60 mph upwards - simple but frustrating
2) fit traction control to limit wheelspin - some help but costly if only a small gain ( I will be "wasting" all the available torque fom 900 to 1,200 kg).
3) add rear weight until the wheelspin stops but then lose out a lot in acceleration above 90 mph or so.

Big problem, now maybe my obsession with why a Porsche 911 turbo with more weight can get so close to the McLaren F1 60 to 100 mph times is more clear. My car is in NO WAY meant to be in the McLaren F1 league but its basic power to weight ratio on open pipes is similar so I have studied the F1 data very carefully.

Any votes on wnich of 1) to 3) I should use , or any better ideas, the car is front engined which hurts traction but I can't change that, most everything that can be done to get the weight rearward has, I think, been done already.

Add diffusers? 200kg at 60mph might be a bit lofty though.

More traction is the ultimate (not by adding mass though). Move some weight back. Move some wheels forward. If you are drag racing, raise the ride height for extra weight transfer. Traction control is great! You are not wasting torque. Having more torque than the tyres can use is ideal because you can then operate them at their optimum slip ratio. Can't do any of the above? Put it in third.

Why not use manual traction control? A lot of the fun of being traction limited is throttle control.
Can you use slicks or some other tyres with better mu?

Not that you haven't already... You may not be able to move more weight back, but if you could remove any weight from the front all together, you'd still increase rear weight bias.

Land speed record cars where top speed is more important than acceleration, use ballast to increase traction. Top speed is not really affected by weight as long as you have a long enough run up.
Wings reduce top speed , but being light , they help traction and hence acceleration.

Better tyres are probably your answer though

Consider the late 1930s 750kg class Mercedes race cars.Front engine,rear drive,750kg weight,horsepower ranging up to the 700bhp region.How did they do it ?

Good post johnny, I think mariner your second gear ratio, although high at 1.64, is too low.The Mercedes has 1.37 second gear and 1.18 third, then .94 top through a 3.52 diff but 19 inch rear wheels on probably high profile tyres compared to todays,so although your diff is 3.09 you are multiplying your huge torque too much with that low second gear ratio and rear tyre diameter a lot smaller than the Mercedes. As well the Mercedes will have a big footprint off that big diameter,although you probably have a wider tyre patch.

No silly aero rules for a car like this- fit a PTO and make it a fan car. Full traction in 1st gear!

Plenty of travel on those skirts! (note cut-outs on rear skirt for fan ducts)

How much of that travel was to compensate for wear over the duration of the race?

Good point. Just noticed two big exhausts plus one little one at the top - dedicated Hoover motor ah la Chaparral.

Part of the apparent skirt height is due to the car standing without the fan engine running. Once that was started the whole car sank down as the vacuum was pulled inside the skirts.

They never got to run it enough to measure race skirt wear as the fan motor , whch was a snowmoble engine, proved unreliable at first , then the car was banned.

I would ban it on aesthetics alone.

Here's one made a bit later....

http://www.pasoporcurva.com/wp-content/upl...46b_fan_car.jpg

This one does drive the fan off the PTO. Unlike the Chaparral above, which had a separate motor for the fan - may have been tough getting a second engine on board passed in F1.

The skirts on the Chaparral are set up on a clever linkage so that they do not normally touch the road. See the gap under the skirt? It remains almost constant even when the little motor is running and the car lowers itself, though the gap would change a little due to tire squat.

Not only clever - alright, Jim Hall got there first - but a stunning-looking car, I think. So many of Gordon Myrray's cars looked great.