Ackermann Principle

[artie on edge]

Firstly can I say that I feel that ackermann in a dirt car cant hurt. But, to what extent do you guys think its 'required'?
Have recently read a thread on an aussie site where a designer/builder states that it is completely unneccesary on a dirt car.

Yes, when in full slide I can see his point BUT... I have spent many a corner NOT sliding and during these moments, I couldnt help but wonder to myself how my car would be handling had I an Ackermann set up........

Your thoughts gentlemen?

[Nutz4sand]

I agree that when the machines sideways or close to it in a corner the outside tires doing 90% or more of the work then it does not matter so much.

But when you are still in a genral forward direction but on the brakes hard the amount of weight transferring to the front is high and with slight to medium turning both front tires are contributing to the direction and with good ackerman setup they will both be pulling the proper amount in the turned direction.

Not all turns are taken sliding sideways. Those turns not sliding sideways will benefit from a proper ackerman setup. So its a good thing to have.   Just my feelings on it.

[Entropy]

Having several conversations with various off road builders and driven a few high speed rides in the dirt over the years you will notice if it is wrong; the rig will certainly get to sideways but... it will get there on the edge of control rather then under-control.  When on a hard surface it will plow (understeer) until you throttle it to oversteer. It will also take more power to push it through the corner...
Well, that is my take on it anyway.

[LiveWire]

I have driven the same car with and without it it. I added Ackermann in that is. I find there is an amazing improvement in the way the car turns while diving into a corner. Just as Nutz4sand said, the weight transfer puts the bulk of the cars weight on the front tires during this transition. To slide the rear end, you have to first get the turn started.

[borris]

I'm amazed in how much different the opinions are from one site to another. I feel strongly that ackerman is a necessary ingredient in a proper designed steering setup.How much or little is a point of debate but to suggest that none is best is just not logical IMO.

[lee1969GB]

Think of it another way, If the front inside wheel is scrubbing along the ground it is acting a bit
like a fiddle or cutter brake so helps the buggy turn!

There seems to be a problem, the writing is going off the end of the screen.

[Dqracer]

Having no ackermann built in to the steering arms is desireable on an asphalt race car,by not having the inside front tire scrub while turning a sharper or smaller radius than the outside tire,is faster lap times. Ackermann will scrub off speed, increases tire drag and increases the tires slip angle which also builds heat into the tire.These are all undesirable effects of Ackermann on the race track. Ackermann is great for street cars as it adds stabilty and gives the driver a feel of responsiveness to the vehicle. On dirt or loose surfaces ackermann can help directional stability by having this scrub of the inside tire help the car rotate about the apex of the turn.   

[fabr]

I think you have that backwards.

[Dqracer]

Which part is backwards..?

[fabr]

Having no ackermann built in to the steering arms is desireable on an asphalt race car,by not having the inside front tire scrub while turning a sharper or smaller radius than the outside tire,is faster lap times. Ackermann will scrub off speed, increases tire drag and increases the tires slip angle which also builds heat into the tire.These are all undesirable effects of Ackermann on the race track. Ackermann is great for street cars as it adds stabilty and gives the driver a feel of responsiveness to the vehicle. On dirt or loose surfaces ackermann can help directional stability by having this scrub of the inside tire help the car rotate about the apex of the turn.   

The purpose of ackerman is to prevent,or at least minimize, tire scrub when turning.

[artie on edge]

Yeah, Im with Mastf here, read your post several times and... I just dont get it.

In my opinion (which isnt worth much but hey, its all I got). If you are cornering and the rear is tracking with the front (important point) Ackermann will always reduce tyre scrubbing and therefore reduce rolling resistance etc....

Which is why I asked the question in the first place...do love to see the opinions though, it all helps.

Now a car with no ackermann will do as I think you are suggesting...again IMO...

[artie on edge]

Btw...ackermann priciple is the name of the theory, in application its called Toe Out On Turns... subtle point...just thought Id throw it in to let you guys realise just how knowledgable I am... or was that to remind myself just how knowledgable I aint???

Damn I always get that mixed up.....

[lee1969GB]

Rear is tracking with the front?? Have you got 4 wheel steer? LOL,

[artie on edge]

NO I dont have a 4 wheel steer. Doesnt your rear end slide? Sorry am I missing something? You had better explain as I feel like im a goose......

[fabr]

Having several conversations with various off road builders and driven a few high speed rides in the dirt over the years you will notice if it is wrong; the rig will certainly get to sideways but... it will get there on the edge of control rather then under-control.  When on a hard surface it will plow (understeer) until you throttle it to oversteer. It will also take more power to push it through the corner...
Well, that is my take on it anyway.

I'm a little unclear here. Do your comments refer to a car with some ackerman or a car with 0 ackerman?