Quote:
Originally Posted by ccracin
Rodger,
I would use a bit of caution in relating weight placement and distribution on a dirt circle track car and anything else. It has been my experience that they are unique animals and most concepts that work there don't transfer well to even asphalt circle track cars let alone cars that turn right and left. You will never deal with a hard surface race track changing like a dirt track will with in a given race let alone day. (I'm sure you have that well figured out by now  ) That is typically why weight placement and transfer change so much in a dirt car and will not in others.
Around here the only guys using that size cell or larger are guys that run alcohol simply because you burn so much more of it during a race. Most try to run as small a cell as they can get away with so that you minimize fuel movement even with foam in the cell. We ran a 12 gallon cell with 6 gallons in it for a 25 lap feature on a .5 mile track as an example. That was the smallest cell we could get off the shelf at the time. Any weight additions are usually done with lead as it easier to know exactly how much you have and it can be more precisely placed. Any weight we added was first placed to optimize our front to rear and left to right bias. Then if we were still under weight for the class we added it as low as we could in the car as close to the CG in the horizontal plane as we could. The car would then be setup slightly tight to start so that it would move to neutral or free as the fuel burned off.
I can't see the benefit (Other than in a dirt car) of adding weight above the rear end line. In most hard surface situations you try to minimize the body roll while creating side bite. (managing weight transfer) This is done by shortening the moment arm length from the CG to roll axis of the car. By adding weight higher than the roll axis, you are effectively creating more roll moment you then have to counter act with stiffer springs or sway bars. (lengthening this arm on Dirt is good but that's another book)
My main point here is that be careful trying to apply what works on a dirt circle track to what most folk ere are trying to accomplish as the 2 in my humble opinion are VERY different. I really wish I could have spent some more time on dirt it was a blast. I only got to play a bit. I really ad a tough time racing my asphalt cars and helping friends with dirt cars because they were so different.  |
I agree Chad, I'm just saying in a car your going to drive on the street you might want more then a 5 gallon tank. And you can add weight or drive range with a bigger tank. granted a 22 gallon tank with 15 gallons of fuel might not be the best idea for a big sweeper autocross, but it might be for a tight track if your set up is tight and your driving style is with the gas pedal, not the steering wheel. Plus if you had 2 11 gallon tanks with proper baffling designed for your applications you would not have much slosh. Plus a full tank of fuel wont slosh.
I also agree traction is not as much a concern in asphalt as dirt, where forward bite is hard to come by. But in high horse power cars that might have say leaf springs you might need to add weight since you cannot control the instant center like a 4 bar that will help with traction and forward bite. But the things a drift car does to set up their car is similar to a dirt car, so if you want the car to be tighter and not super loose your going to do the opposite of what a drift car would. Drift guys want the swing weight and they are also going to use the biggest rear sway bar possible to be able to do that. The main difference is the fact that on dirt your driving off the right rear tire when track conditions are tacky and off the left rear when the conditions are going slick. No where have I ever seen a car set up to turn left with the softer spring on the right then the left but in dirt racing.
As much as the racing on dirt is like a women's emotions, you have no idea what your going to get from one day to the next, vehicle dynamics are going to be similar, you just have to use those dynamics for your driving condition and driving style.