Ackerman Principle

[sasquatch]

Hi everyone
this is regarding the ackerman principle and how you can check it. I know the principle says center of rear axle, left front, and right tire when turning all of their radius will share a common center point. My question is there a way you can check this short of putting ink on the tires and rolling them around
Thanks

[doodlebug]

Welcome aboard!
Have you considered a piece of butcher paper, a framing square and a pencil?
Cheer's, Neil.

[Finster]

Not sure if this will work, but what about a sandwich of white poster board and carbon paper? I know you can get big sheets or rolls of it for copying patterns. The top layer of paper keeps your wheels clean and the bottom tracks the wheels, if it works. Hope this helps.

[sasquatch]

thanks for the replies this project has twin front drives and i would like to get it turning right

[jmking]

Ackerman is the relationship between the turning angle of front tires. Neutral Ackerman occurs when the pitman arm is directly in line with the ball joints on the steering arms. Both tires with turn at roughly the same angle. Negative Ackerman occurs when you place the pitman arm behind the imaginary line that connects both ball joints on the steering arms. Negative Ackerman causes the inside tire to turn more than the outside tire. Positive Ackerman occurs when pitman arm is located in front of that imaginary line.

You should be able to tell where the servo pitman arm is located in relationship to the steering arms. I would always run a negative Ackerman on our off road race cars.

[Espeefan]

It's a very good question, and after thinking about it for a while, what I would do is build the truck with a single steering axle first, take care of the alignment, set the toe in/out, and adjust your servo's arm so that it is parallel with the steering knuckle arm, and then drive it around. See how close you are to achieving a good ackerman set-up. Once you are happy with it as a single steer axle truck, set up your second axle to match the first, and bolt it to the chassis. Reduce the steering throw, little by little, of the second axle, until the truck corners nice, without the second axle fighting the first. When the tires roll without scrubbing or slipping, you've got it!

[CustomRCmodels]

since you guys discussing this here ,
I would like to point out a thread I had posted a while back :
corrected steering for Tamiya COE trucks, Mercedes,Volvo,Scania,MAN
http://rctruckandconstruction.com/showthread.php?p=515#post515

[sasquatch]

Thanks for all the replies very helpful, sourcing material to get this project started will be moving to Big Boys of the Road for the build under 96 foot Wilson