Racing car without swaybars?
Racing car without swaybars?
(OP)
Hello,
is a good idea?
with low center of gravity 4WD racing car without swaybars? (maybe only small rear bar for balance)
some other reason swaybar for use in racing?(than corner balancing)
thanks for your opinion!
Radek
is a good idea?
with low center of gravity 4WD racing car without swaybars? (maybe only small rear bar for balance)
some other reason swaybar for use in racing?(than corner balancing)
thanks for your opinion!
Radek
RE: Racing car without swaybars?
ISTR that when the highway up Pikes Peak was paved only with gravel, the fast racers would remove swaybars, or at least use thinner bars. I think their operating theory/guess was that increased body roll would put more weight on the outside tires, causing them to dig deeper in the gravel, forming a dynamic/transient berm and allowing increased corner speed.
If they were right, your answer depends on the surface you're racing on.
If you have a mix of surfaces, maybe you need a dynamically disconnectable swaybar, which you can clutch/declutch with whatever time you can free up from other driving tasks...
Mike Halloran
Pembroke Pines, FL, USA
RE: Racing car without swaybars?
The track is 100 percent asphalt
I had in mind without sway bar, for compensating roll use stiffer springs
RE: Racing car without swaybars?
If we can achieve an acceptable body roll and good corner balance without swaybars, there is no reasons for swaybar use?
Radek
RE: Racing car without swaybars?
Mike Halloran
Pembroke Pines, FL, USA
RE: Racing car without swaybars?
Thanks Mike
RE: Racing car without swaybars?
Adding a sta-bar increases wheel rate - making that end of the car less compliant, resulting in greater variation of wheel loads over whatever suspension movement occurs. It also reduces the "independence" of wheels on a nominally independent suspension. I think years ago it was Porsche whose opinion was that avoiding the need for a sta-bar was a goal to be sought, reasonable perhaps in the days of low, 1500 lb sports roadsters with horizontally opposed engines and no other single item of substantial mass other than the driver.
Powerful RWD solid axle cars may not use a rear sta-bar at all; this is normal at least in oval track racing whether on asphalt or on dirt.
There is a clear advantage to having a rear stabilizer bar in the very narrow situation of drag racing a car with a solid rear axle. What you're trying to do there is use roll stiffness distribution to oppose driveline torque and equalize the rear tire loading for maximum total longitudinal grip. Rear sta-bars used in this manner tend to be far stiffer than would be sensible for street driving, and may even be coupled with the removal of the front sta-bar.
Norm
RE: Racing car without swaybars?
I have now a stiff front spring for travel limitations and 0.7" front sway bar for body roll limitations
Also very stiff rear springs and big bar for understeer compensation - this causing inner rear wheel traction loss during acceleration out of slow corners
I mean ,when swaybars stiffness decrease the same values front and rear - I get better acceleration out of slow corners
BUT - what will be the impact on the corner balance - when I have the front rollcenter low than the rear?
will to more oversteer?
is correctly?
RE: Racing car without swaybars?
You need to keep load on the inside rear, this means reducing rear roll stiffness or increasing front roll stiffness. Unfortunately this means an increase in understeer.
I have a load transfer calculator that may be of use to you for this purpose?
RE: Racing car without swaybars?
This is my load distribution dilemma
How can I get this calculator?
RE: Racing car without swaybars?
Default inputs are Mazda MX5, you'll need to know a fair amount of detail to fill it in for a Sierra, but most of it should be available if you don't already know it.
At the moment the ARB calculation is only a basic straight, right angled arm one, I've not yet got round to angled arms or anything else. Should still be useful as a comparison between two different setups on the same car, just not between cars with different suspension designs.
Ideally you want the LTD being within a few percent of the weight distribution for a RWD car.
Roll angle is defined as that generated by suspension movement alone. Tyre deflection is not accounted for.
Erm, any more questions, give me a shout!
RE: Racing car without swaybars?
This thread is mostly about AWD, but I think a slightly more robust rule of thumb would be LLTD should be biased towards the undriven axle, and towards the front of the car. A good rule of thumb for RWD road cars would be LLTD on front axle = WD+5%
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Racing car without swaybars?
Seems to work OK in IE11, which was released only very recently . . . and I'm guessing that the unsprung mass entries represent the entire unsprung mass at each "axle" rather than for just one corner.
Norm
RE: Racing car without swaybars?
RE: Racing car without swaybars?
That is when cornering what percentage of the load transfer takes place on which axle. If the RCH is zero at both ends then it is the same as the roll stiffness distribution.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Racing car without swaybars?
On FWD Honda's, they worked best at around 46% LLTD when the WD was around 62%.
I have to disagree on the LTD being the roll stiffness distribution. As you change the lateral acceleration, the LTD changes, the RSD does not.
Norm, good to hear it works on the latest version. I'm not all that bothered about re-scripting it for the older versions, people should be well away from them now but I still need to mention it as there are a few dinosaurs lurking that are still using IE6-9!
The unsprung mass is that in each corner.
How do you quote on this horrible forum software?
RE: Racing car without swaybars?
nice toy
sorry , but what it means : LTD,LLTD,RSD, etc.
Thank You,
Radek
RE: Racing car without swaybars?
RSD = Roll stiffness distribution. The percentage of the total roll stiffness taken by each axle. This is fixed.
RE: Racing car without swaybars?
[quot name]paste text here[/quot] . . . misspellings of the word "quote" are intentional else you won't see it. Including the name is optional.
Norm
RE: Racing car without swaybars?
how to estimate CoG height for calculation?
RE: Racing car without swaybars?
RE: Racing car without swaybars?
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Racing car without swaybars?
What is the typical value of the CoG height for example:
WRC car (asphalt - low version)
WTCC car
DTM car
NASCAR
I know that my calculation will be incorrect,but help understand the connection.
RE: Racing car without swaybars?
You and I have a very different understanding of FLLTD then. How can it NOT change?
At 0g the FLLTD is 50%. At the point of both wheels lifting, it is also 50%.
At any point between those two extremes, it is dependant on the RSD and the SWD.
In a 50/50 WD vehicle, with a non equal RSD, the stiffer axle will transfer load faster, up until the inside wheel is completely unloaded and lifts off the road, at which point the LT across that axle is 100%. The softer axle will be at less than 100% load transfer as the inside wheel is still loaded, and so the FLTTD at that point is not 50%. Past this point, the softer axle continues to transfer load until it to has transferred 100% of it's static load, at which point the FLLTD is once again 50%.
Please explain how you think it remains constant.
RE: Racing car without swaybars?
RE: Racing car without swaybars?
Work from those examples and have a think about where the weight is in your car. A saloon car with a high roofline, large glasshouse, upright engine with heavy DOHC head and perhaps high mounted turbocharging equipement is all going to add to that height significantly.
An upright alloy block with heavy DOHC head is going to have a higher CG than a cast iron block V8 with pushrod alloy heads, a lot of sound deadending removed from the floor of the car will move it up, poly windows will move it down, so on so on.
RE: Racing car without swaybars?
look ,is nothing superfluous
RE: Racing car without swaybars?
Really, the only way to be sure is to determine it with a tilt test, but it's a bit time consuming as you need to replace the front suspension with rigid links to do it accurately.
RE: Racing car without swaybars?
Just to expand on this some more.
At 0g, '0% LT', FLLTD is 50%. At point of both wheels become unloaded, FLLTD is also 50%. Lets call this '100% LT'.
Let's look at 10%, 20% and 30% LT.
2000lb 50/50 SWD, with a 60% front RSD.
At 10% LT there is 200lbs LT, of which 60% is taken by the front.
Front LT is 200 x .6 = 120lbs. The outside front tyre has 500+120 = 620lbs load.
Rear LT is 200 x .4 = 80lbs. The inside fear tyre has 500-80 = 420lbs load.
FLLTD is (620+420)/2000 = 52%
At 20% LT there is 400lbs LT, of which 60% is taken by the front.
Front LT is 400 x .6 = 240lbs. The outside front tyre has 500 + 240 = 740lbs load.
Rear LT is 400 x .4 = 160lbs. The inside fear tyre has 500-160 = 340lbs load.
FLLTD is (740+340)/2000 = 54%
At 30% LT there is 600lbs LT, of which 60% is taken by the front.
Front LT is 600 x .6 = 360lbs. The outside front tyre has 500 + 360 = 860lbs load.
Rear LT is 600 x .4 = 240lbs. The inside fear tyre has 500-240 = 260lbs load.
FLLTD is (860+260)/2000 = 56%.
Thus, FLLTD varies with acceleration.
RE: Racing car without swaybars?
but a dramatic increase torsional stiffness!!really
RE: Racing car without swaybars?
It won't affect the CG greatly, but it will certainly raise it slightly vs having no cage at all.
Given the spartan interior and I'm guessing an iron block DOHC engine, as a total guess I'd probably quote your CG being in the 19-20" region.
RE: Racing car without swaybars?
but engine is 4.0 V6 (60 °) SOHC mustang cast-iron block+alu heads
RE: Racing car without swaybars?
RE: Racing car without swaybars?
More reliably, there is this NHTSA database (the CG information starts on page 10).
http://www.nhtsa.gov/DOT/NHTSA/NRD/Multimedia/PDFs...
Norm
RE: Racing car without swaybars?
I think you may be confusing lateral load transfer with the relationships among the resulting wheel loads after the load has transferred.
LLT = Lateral Load Transfer, which is only the 120 and 80 numbers in that particular case.
The only way the distribution of LLT can vary is if there is some nonlinearity involved. The only way that would amount to much would be if said nonlinearity is significant - such as in the case where an inside wheel lifts, or where significantly nonlinear-rate springs are fitted at one end and linear rate springs at the other.
Norm
RE: Racing car without swaybars?
FLLTD = Front Lateral Load Transfer Distribution i.e. how much load transfer has happened at the front. It changes with lateral acceleration.
Perhaps it should be called 'Front Diagonal'.
Whatever it is called, the differential between front and rear load transfer is not constant.
RE: Racing car without swaybars?
You'll note that your 120/80, 240/160, and 360/240 load transfers are all in a 60/40 distribution.
Adding outside front and inside rear cornerweights and expressing that as a percent of total car weight is crossweight or "wedge" in circle track slang, and this will of course vary.
Norm
RE: Racing car without swaybars?
RE: Racing car without swaybars?
Radek