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equation for calculating steering angles?
Delinquent - 8/10/07 at 03:10 PM

In 2 books I've got, it gives a formula for calculating the turning circle as:

Tc = W/Sin L

Whers

Tc = Turning Circle
W = Wheelbase
L= Lock angle of the outside wheel.

I've done the maths on this (well ok, someone helped me....) and it comes up with an angle for the outside wheel of 14 deg - which seems extremely small?

Is the equation wrong, does anyone know of an alternative, or am I just imagining needing more?!

[Edited on 8/10/07 by Delinquent]

RickRick - 8/10/07 at 03:12 PM

i don't quite know how it applies to big cars, but on rc cars the inside wheel turns quite a bit more than the outside wheel.

also you didn't mention what the turning circle was to give 14 degrees

02GF74 - 8/10/07 at 03:20 PM

quote:
Originally posted by Delinquent
In 2 books I've got, it gives a formula for calculating the turning circle as:

Tc = W/Sin L

Whers

Tc = Turning Circle
W = Wheelbase
L= Lock angle of the outside wheel.


never come across this but it seems correct to me.

let's say wheels never turn, so angle is 0.

divie by 0 gives infinity i.e. the car never turns, this is what you would expect if you put sterring in straight ahead position..

now lets say wheels turn 90 degree, sine 90 = 1. so turning circle is smae as wheel base. basically you can imagine the car rotating on t he inner rear wheel i.e. wheelbase - so equation again matches what you would measure.

matt_claydon - 8/10/07 at 03:21 PM

Seems likely such a formula would use the radius of the turning circle, although without drawing it out and thinking about it I couldn't say for sure.

Would that give you a better answer?

Edit: Post above sounds correct, although tying in with what I said above, wheels at 90 degrees would in fact give you a turning circle of twice the wheelbase.

i.e.
Tc = 2W/Sin(L)

[Edited on 8/10/07 by matt_claydon]

Delinquent - 8/10/07 at 03:25 PM

my apologies, I am at a base level being a bit of a retard - it clearly states later on that that gives the radius - which I came across only after someone on another forum pointed it out a couple of minutes ago!

sorry about that!

britishtrident - 8/10/07 at 05:46 PM

One of the things in engineering that a simple graphical solution will give you a good answer -- with its own built in sanity check.