Ackerman Excel calcualtion file, Plot your graph

[cazman]

I just sourced this file that allows you to plot your Ackerman and scub radius.

There are infinite uses for it but i have my own uses, only problem is I work full time and study so i dont have time to accuratly plot my S13.

Can anyone have a play round with it and see if they can plot theirs etc?

[hispanicpanic]

i used win geo for calculating all my suspension characteristics. A lil more complicated, but i don't really trust an excel file made by someone else, and i don't really feel like looking through every cell and checking their math. Also, ackerman many times depends on track speeds and driver prefference. 140% ackerman feels awsome for tires with high slip angles and tracks with low speeds, but once you're going 100+ on tires with little to no slip angle, things get really dangerous. How much slip angles do your tires have, you ask??? Good question. The manufacturer sure as hell won't tell you, and to find out experimentally is retarded expensive.

http://www.mitchellsoftware.com/products.htm

tire data

http://www.millikenresearch.com/fsaettc.html

unfortunately milliken mainly does 10inch and 13 inch tires for FSAE.

[hispanicpanic]

sorry i couldn't answer your question, but just thought i'd give you some personal insight. But i do agree, 240's could use more ackerman. I would make an adjustable setup ( 140%, 120%, 100%, 80% etc).

[Matt93SE]

Thanks for the input. Now translate that to engrish.

[cazman]

^ Reference thanks to TIP

There isn’t a universally agreed way to express how much Ackermann (toe-out increase with steer) a
car has. The closest thing we have is to take the plan-view (top-view) distance from from the front
axle line to the convergence point of the steering arm lines, divide the wheelbase by that number,
and express the quotient as a percentage. If the steering arms converge to a point on the rear axle
line, that’s said to be 100% Ackermann. If they converge to a point twice the wheelbase back, that’s
said to be 50%. If they converge to a point 2/3 of the wheelbase back, that’s said to be 150%. If they
are parallel, that’s zero Ackermann. If they converge to a point twice the wheelbase ahead of the
front axle, that’s said to be –50%.
Supposedly, with 100% Ackermann, the front wheels will track without scuffing in a low-speed turn,
where the turn center (center of curvature of the car’s motion path) lies on the rear axle line in plan
view. This is actually not strictly true, even for the simplest steering linkage, which would be a beam
axle system with a single, one-piece tie rod. With either a rack-and-pinion steering system or a
pitman arm, idler arm, and relay rod or center link, we can’t fully predict what the Ackermann
properties will be at all, merely by looking at the plan view geometry of the steering arms. The
whole mechanism affects toe change with steer.

[hispanicpanic]

thats where optimum K comes in handy

I think they still have a free demo on their website. It does almost everything the full version does, but you can't save anything.

[Matt93SE]

thats where optimum K comes in handy

I think they still have a free demo on their website. It does almost everything the full version does, but you can't save anything.

you can take screenshots though, right?


I'm familiar with the theory behind what Ackerman is and why you'd want to change it, but it's the 'what to set it to' that I don't get.. I guess that's why the good race setup shops make the big bucks!

[hispanicpanic]

you can take screenshots though, right?


I'm familiar with the theory behind what Ackerman is and why you'd want to change it, but it's the 'what to set it to' that I don't get.. I guess that's why the good race setup shops make the big bucks!

right. But if you look at the input section, they ask for things that are impossible to determine (slip angle of tire). I'm also not familiar with half the terms they use for their input variables. Do you know who made that spreadsheet?

[Matt93SE]

No idea. I haven't looked at the file yet.

I've seen some data on various tires' ideal slip angles. I forget who/what/what numbers, but I've seen them in the past.