Indoor Kart'n.....

[dieselgeek]

Let's use drag racing to help understand the concept.... traction is created by the weigh shift to the rear wheels. Without the weight shift, you don't accelerate as quickly because you don't have as much grip. On a Kart track, the same principle applies in reverse, more weight on the front wheels (obviously to the limit of grip) means you turn harder, faster (thus also the need to turn sharp then do a progressively longer radius out of the turn). DG, you'd be right if it was a skateboard, but Karts flex and weight shift like indy carts.

I got my trophies between 10 years ago and 4 years ago (as an adult at 200+ lbs).... and I beat all sorts of people, including kids - and the Karts were all, basically the same.

I know in drag racing, additional weight that gives traction also costs ET because it's more weight that has to be accellerated. Drag racing cars *always* improve ET with weight reduction... so long as all else is equal... this is a great question, I'm not claiming I know the answer but it seems like a basic physics quandry. God knows I don't want to offend any readers!!! :-)

[JeffMcKC]

Objects at rest tend to stay at rest.

Indy cars are a poor example they have both down force and more power than they know what to do with.

A sit up Kart the center of Gravity is higher with the added weight which makes it want to turn over, the added traction is used up as the weight wants to go straight not turn and a skid pad will bear that out with understeer issues from the weight. Light weight and a balanced kart with drivers skill will win out every time. A driver that understands how a Kart works is work a lot and maybe how you won.

TC if the track that you go to has more of one turn than the other then you can if its a right hand dominate track pick the front tires up one at a time go from Kart to Kart find the one with the heavy right front tire. We used to tweek frames this way all the time till I built a Kart with bearings spacers and heims to adjust camber it it. I had because of my height/weight wheelbase % and I tried everything, a huge understeer problem. ( I use the Mark Donahue Method of driving)

I still have 2 Karts Mine is over 7 foot long and a Komet K-88 which runs 18,000 rpm and over 125 MPH we raced on 2 to 3 mile long tracks back then. The Open Karts ran on Alky, Nitro Benzine and Acetone to even the burn. The Stock appearing Karts ran on the lightest gas we could buy then added Nitro benzine to bring the weight up, it was fine till they caught on and started water checking us.........

[SuperBuickGuy]

you both are right, but you're not going far enough. Your traction is limited by two things 1) grip, and 2) weight transfer. you can increase grip by putting more weight over a wheel - a light person cannot put enough weight on the wheel to push it beyond its limit of grip (there is a limit to all this, but for these purposes a 75 lb kid vs. 200 lb adult is the comparison) thus - like your skid pad example - it is a steady-state test, but it's not the absolute limit of grip. Example - current Vettes can handle right at 1 g on a skid pad, however, they can do more than 2g if you load the front wheels and turn simultaneously.... the reason you can do that is because you're putting more weight on the wheels.... clear as mud?

and DG - I don't understand - are you trying to sound disingenuous with your constant apologies?

[JeffMcKC]

I am not going to keep going into it you forgetting to equate the center of gravity change in the Kart it does not have susp. either, but you can look at lap times, the Light class will always be faster than the Heavy classes, in most cases it will be the same drivers with a second Kart or in my case I was heavy in the Light Class and just right in the Heavy with the same Kart and engine packages just a fresh engine, those things cost more than a car to run.

[TC]

pretty sure that goes against racecar physics. The weight you use to gain traction is still additional weight that fights the change in direction. there are a number of roadrace guys here who shoudl be able to shed some light on that.

edit: if more weight was better, than why woudl there be a "minimum" weight rule in all the racing kart classes I know of? (which is remarkably few). Also, if that theory was true then it would seem the more weight the better, so why not carry around a few hundred extra pounds of weight? this is an honest question, not trying to get anyones feathers ruffled.

Go ask Keith how much the HotRod Special weighs in at.............

[dieselgeek]

Go ask Keith how much the HotRod Special weighs in at.............

I already know, it weighs about HALF the car we're bringing to Bonneville this year. And ask yourself, would the SoAl Special accellerate and turn quicker than the same car with half th weight? The clear answer is, that car won't turn for shit, ever. Take 80% of the weight out of it and it'll turn far faster.

What you guys are saying sounds good but it flies directly in the face of what guys like Carroll Smith show in his book. Think of it this way: what turns corners quicker, an open wheel Indy car? or a Cup Car (NASCAR)? by far, the Indycar out turns and out accelerates the Cup Car, and they both have almost the same amount of power. The cup car weighs more but has similar tire area.

[TC]

you both are right, but you're not going far enough. Your traction is limited by two things 1) grip, and 2) weight transfer. you can increase grip by putting more weight over a wheel - a light person cannot put enough weight on the wheel to push it beyond its limit of grip (there is a limit to all this, but for these purposes a 75 lb kid vs. 200 lb adult is the comparison) thus - like your skid pad example - it is a steady-state test, but it's not the absolute limit of grip. Example - current Vettes can handle right at 1 g on a skid pad, however, they can do more than 2g if you load the front wheels and turn simultaneously.... the reason you can do that is because you're putting more weight on the wheels.... clear as mud?

and DG - I don't understand - are you trying to sound disingenuous with your constant apologies?

I saw that with the kids, they would spin out 90 to a 180 degrees, where when I would spin out I'd spin out less than 90 degrees......

[dieselgeek]

and DG - I don't understand - are you trying to sound disingenuous with your constant apologies?

I had to look up that word. I'm apologizing because I don't want to offend YOU. But I'm pretty sure that you are not correct, that's all. I'm basing this on the Carroll Smith books I read, and the logic I learned while working alongside guys like Jeff at the drag strip, and finally the logic I pointed out above, that in cars with similar power and similar tire contact patch, the lighter car ALWAYS turns and accelerates faster.

[moparmaniac07]

I had to look up that word. I'm apologizing because I don't want to offend YOU. But I'm pretty sure that you are not correct, that's all. I'm basing this on the Carroll Smith books I read, and the logic I learned while working alongside guys like Jeff at the drag strip, and finally the logic I pointed out above, that in cars with similar power and similar tire contact patch, the lighter car ALWAYS turns and accelerates faster.

But wouldn't the indy car technically be heavier if you add downforce to it? More weight over the tire equals more traction. Granted, it's not mass that has to change direction, but the same principle, push the tire into the ground with as much force as possible. I don't know the science behind karts, but if I understand correctly, SBG is saying to use weight as downforce the carts don't have to give the front tires more traction. Whether the added traction makes up for extra mass is where Jeff's disagreeing I think.

[JeffMcKC]

DING DING because your down on power around the whole track........... The kids spun out more because they where going faster and dont know how to drive......

[pdub]

But but but...downforce aside, does not the Indy car corner quicker than the Cup car because of a drastically lower center of gravity? In my mind, if you put a heavy weight on a tall stick way overhead, the car is going to lean on the corners, taking the inside tires completely out of play in a corner, if the rig doesn't actually turn over.

Low CG. All four tires biting. At least the inside ones biting much more than on a taller car.

[SuperBuickGuy]

read the stuff around diagram 2 about late apex racing lines.

http://www.drivingfast.net/techniques/racing-line.htm#axzz1jkwdK3GF

and now ask yourself, why is that the fastest way through a corner.

I have more words, but maybe you'll believe them if written by someone else

[SSChevyManiac]

Doug, I didn't quote you but yeah it's in the Mack plant.

[TC]

read the stuff around diagram 2 about late apex racing lines.

http://www.drivingfast.net/techniques/racing-line.htm#axzz1jkwdK3GF

and now ask yourself, why is that the fastest way through a corner.

I have more words, but maybe you'll believe them if written by someone else

Thanks for that, I now know why I was spinning out/sliding on the hairpins.....I was taking the wrong line...........

[SuperBuickGuy]

Thanks for that, I now know why I was spinning out/sliding on the hairpins.....I was taking the wrong line...........

it truly is counter-intuitive....