Yeah I figured that out after I hit "Post" :imubash:Quote:
Originally Posted by Coach 2
By the way, what language works better for you?
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Yeah I figured that out after I hit "Post" :imubash:Quote:
Originally Posted by Coach 2
By the way, what language works better for you?
Last evening for me was little bit more TV because there was an interesting document about a 11 year old girl that had been run over by a tram. She lost her left foot but after recovering and with prosthesis she could continue with her enthusiasm for gymnastic with some limits. The other one was the movie “Slumdog Millionaire”. OK, these were off-topic but this was how I spent my yesterday evening.Quote:
Originally Posted by Antony Warmbold
Thanks for the clarification about “driving from the rear”. I suspected something like this but I was far from sure about it. How about the definition of suspension?
Hejsan sveisan gamla gubben. I’m not so old, just turned only 59. It’s of course OK for you to poke your nose here on this forum but otherwise be careful where you poke your nose.Quote:
Originally Posted by janvanvurpa
Btw, do you have any access to “surströmming” in the States?
Thanks for the explanations.
Yes, or at least I think so.Quote:
Originally Posted by janvanvurpa
I’ve explained this to myself in the following way. When cornering the outside wheels goes up (springs and shock absorbers are compressed) and due to the anti-roll-bar the inside wheels will follow this movement (how much depends of the stiffness of the ARBs). But when the inside wheels go up but not going to stay in the air and instead being in contact with surface, the body shell is straighten because the inside wheels (or the inside part of the ARB) is pulling the inside of the body shell down and straighten the body shell.
The ARBs transfer the weight from the inside to the outside and how much depends on the stiffness of the ARBs. The stiffer the ARBs are, the more weight transfer. Generally more weight on a wheel gives better grip but the next thing is the grip between the tyre and the surface. With more weight transfer (stiff ARB) only the outer wheel have to take care of the grip and if the friction is not enough, the wheel starts to slide. I believe that a roll of a car is not because of too fast approach to a corner but that the driver hit something on the inside of a corner that will roll the car. Whit a softer ARB, the weight transfer is more even between outside and inside wheels and the overall grip is better.
Correct me where I’m wrong.
What I’ve been written above is from a book I have, “The tuners handbook – the chassis”.
It includes chapters like basics of driving dynamics including camber, caster, toe, center of gravity and the axle that the body shell rolling around (I don’t remember the English word for this but it’s the axle between the front center of roll and rear center of roll that the body shell roll around in corners) and how the different adjustments / set-ups affects the handling of the car. Other chapters is about the springs, dampers, steering, transmission / drive train, breaks, tyres, rims, reinforcing the body shell (safety cage and reinforcement of suspension parts attachments points, protection of the chassis) and aerodynamics. At the end of the book is a summary of what affects under steering, over steering, traction when accelerating, to much nod when braking, to much curtsy when accelerating etc.
And…
A mega internet page about these things you can find here. I don't remeber who of the forum member originally posted this link. It’s about R/C cars but the physics are the same maybe an exception of the ratio between sprung mass and unsprung mass.
Quote:
Originally Posted by dimviii
Quote:
Originally Posted by Antony Warmbold
Thanks for the info. You’re building cars and you have good info about these things. Btw, are you driving yourselves also?Quote:
Originally Posted by dimviii
"What do you think was the hardest choice, to get the best feel for the surface?"
Hi Coach2,
Things became much easier for me when I got the proper diff maps in the car, around middle of 2005. Up until that time, the few times that we tested were mainly dedicated to diff mapping. It was by far the most complicated thing to figure out. On your own, you needed A LOT of km's to manage to have something good. So the toughest choices to make up until then was diff maps for the rally. There was a lot of unknown.
After the maps were sorted, suddenly, I started feeling much better the grip. Like I said this car had a very sane behavior so with the right diff maps it was really a very good car.
So, providing that you were not using completely wrong tires for a given surface, the feel for the grip was fantastic.
After that, you can adjust your ALS "brutality". It was important to have the ALS not too hardcore if it's very slippery.
Going harder on the damper clicks in compression (compared to the base setup) helped me get more feedback from the road grip and feel for it.
--Changing this on the focus was not an option, and not necessary, but having too "light steering" (strong power steering) like on the Corolla WRC was a real pain for me. The focus gave much better feel for the grip when you turned the wheel.
That's all I can think of right now!
Good night. :)
I had just discovered the blog, but I've read it all already. What a great source of info on privateers' side of WRC! Keep posting, please :)Quote:
Originally Posted by Antony Warmbold
I have bowed to your request: WRC behind the stages: The big No-NoQuote:
Originally Posted by kober
Cheers,
Thank you for a nice answer Antony W.Quote:
Originally Posted by OldF
Also, are you agree with this conclusion Antony.
Hi Coach 2,Quote:
Originally Posted by Coach 2
Your post & the things you agree with, that OldF wrote, makes sense to me. Although I'd like to stay cautious about how to explain: weight transfer, shift, and how it relates to grip because I don't have an engineer's knowledge on how the physics work. My area of expertise is rather hands on. But anyway, it sounds right to me!
@ Coach 2
I emphasize that what I’m saying is based on what I've read and how I interpret what I've been reading.
The author of the book I have says:Quote:
Originally Posted by OldF
“Paradoxically on the other hand, is that the anti-roll bar will increase the weight transfer from the inside to the outside.”
Btw, the author has a master of engineering degree from a technical university, so I think he know the theory. The “Tuners handbook 1 (tuning a four-stroke engine)” was based on his master thesis.
I had to make some Googling to find more information.
Here are web sites with an example.
Physics/ theories of Sway bar
This is imo the best web site I found explaining how the weight transfer occurs. There is probably a little error in the explanation.
“So now we have a 25 lb upwards thrust on the Right spring (should imo be the left spring) that happens to have a downward force of 125 lbs. So, we have to subtract that 25 lbs from the amount of weight actually making it to that sides contact patch & Add it to the contact patch of the Right.”
How Weight (or Load) Transfer Affects Handling of a Race car
Anti-Sway Bars: A Primer - Automotive Articles .com Magazine
“What a sway bar does is counteract the action of body roll during cornering by transferring spring rate from the inside wheel to the outside wheel in a corner. This means that you don't actually get any added spring rate; you just subtract it from one side and add it to the other.”
And few more “inside to outside” web sites.
TurnFast! Race Driving Techniques for Heel Toe Downshift, Driving Line, Cornering, Braking, and More
“On the outside tire, this downward pressure helps increase tire traction. However, on the inside tire, the anti-roll bar is pushing up on the suspension reducing the downward force the spring is trying to place to keep the tire on road. If the anti-roll bar is too stiff, it will overpower the spring, prevent it from extending enough to keep the tire on the road, and the wheel will
actually lift off the ground.”
Anti-roll bar
“Here is how they work: the anti-roll bar ties the left and right side springs and dampers together laterally…….. However in a turn, the weight transfer is from inside to outside. The inside wheels travels down (losing sprung weight) as the inside springs releases energy under weight transfer and the outside wheels travels up (remember the car weight is rolling inside to outside) as the outside springs absorbs more energy. This causes the anti-roll bar to twist its ends in opposite directions.”
Formula Sheane - The Cars
“Anti-roll bars control where the transferred weight goes. Let’s imagine your car has no front anti-roll bar and a rear anti-roll bar made from inch thick Titanium bar. When your car turns into a corner it is going to transfer weight from the inside to the outside. The titanium girder is going to resist that transfer. In doing so, it is going to put all the weight onto the outside rear tyre.”
More weight, more grip of course. But as said on web sites below (and the book) the weight transfer is not linear. The inner wheel is lifted up by the anti-roll bar as it’s commonly explained and it has less weight on it compared to the outer wheel.Quote:
Originally Posted by OldF
The outer wheel (tyre) has more weight (more grip), but at some point the outer wheel (tyre) loose the grip because it can’t handle the centripetal force made by the cornering of a car at high speed vs. the vertical force made by the weight transfer (which is not linear) to the outer tyre.
The friction coefficient between the surface and the tyre decides when it’s going to happen and when it happens, the car starts to slide.
Front Sway Bar, how it works
“Making the front sway bar stiffer adds weight to the outside front wheel while reducing weight on the inside front wheel, and vice versa at the rear.”
“Lateral grip for a tire increases with weight loading, but is not linear. Increasing load on a tire by 50% may only increase lateral grip by 30%. This represents a reduction of grip efficiency.”
“That is, if you overload one tire by reducing load on the other tire (on the same axle), the total lateral grip is reduced.”
FTW Racing - Fabricated To Win
“The problem here is that the weight to grip relationship is not linear. This means the grip lost by the more lightly loaded wheel is not made up by the increased grip of the more heavily loaded outer wheel and as a consequence their combined grip diminishes.”
“During a turn the vehicle goes into roll, the front roll bar dramatically transfers weight from the front inner to front outer, almost lifting the inner wheel off the ground.”
ARB's transfer weight from outside to inside, or put another way, transfer grip from outside to inside. But not all of the grip you lose on the outside is transferd to the inside. Some of the grip is lost. But what you get is better handling and faster weight shift. This is necessary on asfalt or when you have a lot of grip.[/QUOTE]Quote:
Originally Posted by OldF
I agree with the two last sentences.
The web sites I’ve read with a mention of understeer or oversteer (and also in the book) is saying that for example a stiffer ARB in the front compared to the rear (or no ARB at the rear), makes the car understeer (front looses the grip first => better grip in the rear) and visa versa.
As known the basic function of an ARB is to decrease the body shell rolling. For an example with an ARB in the front, the rear doesn’t roll (less weight transfer) as much as without any ARBs and the grip at the rear is more even between the inside and the outside.
Have a look at this web site: How Weight (or Load) Transfer Affects Handling of a Race car (same as in the beginning of this post).
Hello OldF, and thank you for the answer.
I think your answer (or what you refer to) are two ways of saying the same. I would also agree that he mean left when i wrote right. I will also try to make my answer readable for everybody, and not be to technical.
But some technical stuff is needed.
When a car is tilted due to centrifugal forces, the tilt is made by the weight which rests on the springs. In opposition to the suspension, that have a lot of weight that don't rest on the springs.
So, when you but on a ARB or put on a stiffer, you would limit the roll or tilt and by that keep more weight on the inner wheel. Less weight transfer. But you ad/transfer weight of the inner suspension (and also some of the weight that rest on the spring that has increased because of less roll) to outer by lifting it with th ARB.
But the most important (you and i could agree to this claim) by doing this (putting on ARB/stiffer ARB) the overall grip on the same axle is reduced.
“That is, if you overload one tire by reducing load on the other tire (on the same axle), the total lateral grip is reduced.”
And because of this reduction the car have less grip on the axle with ARB.
So as you wrote.
"The web sites I’ve read with a mention of understeer or oversteer (and also in the book) is saying that for example a stiffer ARB in the front compared to the rear (or no ARB at the rear), makes the car understeer (front looses the grip first => better grip in the rear) and visa versa".
Humble Coach 2.
Hi Coach 2,
Seems the problem is solved. Things can be explained in different ways and I explained in the way that suits my head. :)