SidewaysFC

Not to interupt this great conversation ...but what is the conversion factor for the units regarding lb and kg when indentifing spring rates?

its66

iTrader: (2)

Sideways...
Try this, it is very useful.

http://www.convert-me.com/en/metric_conversions_en.html

SidewaysFC

ty ...still couldn't find the right conversitions though. i suppose i'll do it the systematic way with cancellations.

lbs/in to kg/mm i think.

Nihilanthic

Its kilogram/mm vs lbs/inch, right?

"In order to convert kg/mm to lb/in do the following. Multiply the kg/mm amount by 56. So if you kg/mm spring rate is 6 kg/mm Front and 5 kg/mm Rear your lbs/in would be 336 lb/in Front and 280 lb/in Rear. Pretty Simple."

That seems to be the basic conversion factor, and more convenient than "55.9974146". :P

I also found a nifty lil calc here.... http://www.proshocks.com/calcs/anglefirst.htm might be useful if youre ever calling up someone and spitting out your own spring rates you want wound and happen to know all the math.

Good thread!

DamonB

Just as ernestgj says, a splitter to me is always horizontal (parallel to the ground). Once you start putting an angle on it you now have a spoiler. Splitters and spoilers function quite differently.

Nihilanthic

So, whats the specifics on a front spoiler, then? And uh... what angle do you build it at so that on WOT it doesnt have the leading edge higher than the trailing edge to keep it just as a splitter? Or, do you just stiffen up the rear end of the car a lot?

SidewaysFC

When does the shape of the front bumper play a role in this issue? Like comparing some aftermarket bumper covers with stock. Those with big openings I assume would allow too much air to pass through and not enough air to remain in that pressurized area pushing down on the splitter.

Nihil - I think someone mentioned that earlier, by way of shock travel markers. It is at the point when the rear squats no more that the leading edge will not increase above the trailing edge and it will be horizontal at WOT. So it is more car specific to lift the lift of the front end generated by the engines power and stiffness of the springs. Am I understanding this correctly?

Nihilanthic

All cars lean back on acceleration, drag race cars pull the front wheels up off the ground actually. But yeah on a race car for circut racing you dont generally want that much, as that would mean it would understeer like hell on the throttle... heh. I guess you just gotta play with it and get it right.

A far as bumper shape, if it sticks out enough and its strong enough it will push down on the front of the car, but youre right.. most rice crap is just for looks. I guess for safetys sake you oculd just give it a little bit of a positive rake.

ernestgj

Front spoiler, ie Formula 1 or Indy car are inverted wings. Like an airplane they have an angle of attack. The negative lift (or downforce) is proportional (quadratic function, not linear) to the angle of attack. The drag is also, but that's another issue. Formula 1 produces the wings so that at WOT the angle of attack will be close to zero (you don't need front downforce when you are accelerating hard, do you). When the car is at constant velocity (nose not pitched either up or down) it has a different angle of attack. Finally, when braking it has the maximum angle of attack which means they get the most downforce on the front tires. So basically, you want to make sure that the angle of attack is greater than or equal to 0 degrees when you are at wide open throttle. Probably the easiest way to do this is to take a video of your car launching and running through 1st gear (you only need 1st gear because this produces the most squat). Pause the video on the screen and whip out a protractor to measure the angle between your car and the ground. Notice that the car will squat a lot on launch, this angle isn't important because there is no air flow over the car so a wing is useless at this speed.

Greg

ernestgj

Oh yeah, to clarify spoilers/wings: spoilers are continuously connected to the car while wings have an air gap between them and the car body.

Greg

Node

iTrader: (1)

anyone care to share why ITS cars use stiffer front sway bars and remove the rears?

-Ben Martin

Black91n/a

I've found an online source for some excellent aero articles. The site's down right now, but I'd think its only temporary.

http://www.advantage-cfd.co.uk/Newsl...-Articles.html

The articles about front airdams, splitters and diffusers are V14N10, V14N11, V14N12.

its66

iTrader: (2)

Not trying to be a smart a$$, but mainly because that seems to work. Starting with my ITA 240 sx, I tried several different spring/bar set ups. With a rear bar, I could get the car loose, but the loose was very "snappy" and not easily controlled. A long time RX7 (who we shall refer to only as Hollywood) racer suggested I try losing the rear bar and reset around that set up. It worked. It was also loose, but much easier to drive than with the rear bar.

I have a similar set up on my ITS RX7. It works. Big, speedway style adjustable front bar. No rear bar. Several different theories on spring rate, but most are similar.

If you want more, pm me or you might start a new thread. This post will get lot here.

C. Ludwig

iTrader: (27)

On the bar setup, the main difference is the field of use. There is a huge difference in balancing a car for average speeds over 85mph and balancing a car for autocross. You run the big front bar and no rear bar to do exactly what one would think that would do, tighten the car up. Like Jim said, that's what works.

ziig

iTrader: (1)

actually I did my final year thesis on CFD vs. Traditional testing and found that a splitter will not increase drag in any way noticiable. It will assist by creating suction and removing the large bubble of dead air in front of the car which in fact is a big wall of air that slows you down. as long as the body can withstand the DF produced without being rip out, and if you flatten your floor out it will assist even more. keep your splitter at zero as best as possible and keep it well withing yout existing bumper.
I used FLUENT and windtunnel testing as my test method and found that the more (faster) you can move the air over your car the less the drag will equate to.
try to avoid bubble seperation and heavy boundary layer.
But over all i think you will find a splitter with a wing and diffuser is all you need for any motorsport.

speedturn

iTrader: (1)

I would not mold the splitter out of fiberglas. Splitters take a lot of abuse, and fiberglas would break very fast. I studied the Audi prototypes up close, and they make their splitters out of what appears to be a dense grade of 3/8" plywood. I was told that they adjust ride height until the splitter grinds really bad on the pavement bumps, then they raise it up a little until it grinds just a little bit each lap.

5 weeks ago, I built a splitter just for one race. I usually race in a class where splitters are illegal, but for one SCCA regional road race I ran in the Super Production class which allows unlimited aerodynamics. I made a 15/32" thick plywood splitter and screwed it to my front undertray / air dam. The track, Nashville Superspeedway, had very rough pavement transistions, and the splitter took some hard abuse and still looked great at the end of the weekend. Next time, I would make one out of thinner 3/8" or 11/32" plywood.

On the GT Car forum, they recommend using an expensive polymer sheet called Garolite
http://www.gt-racecar.com/forums/top...?TOPIC_ID=1566

Node

iTrader: (1)

thats what i was originally planning, a thick *** plywood lip, and just shave the front to make it angled for airflow a little, but sounds like i can go skinnier and not even bother w/ the front anymore, i really liked the idea of a brushed or polished aluminum ankle chopper