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Old 03-04-2002, 12:46 PM   #1 (permalink)
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Question How to calculate turning radius?

Ok this is the first time I have ever designed a steering system. This is for the buggy that I am building. Right now I am playing with how many degrees the wheels need to turn to achieve a good turning radius. So based on the wheelbase and wheel degree and possibly tire width if that is a factor how would I figure out the radius?
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Old 03-04-2002, 01:09 PM   #2 (permalink)
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Ummm, drive in a circle? I would say just make it turn as sharp as you can, and don't worry about it.
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Old 03-04-2002, 01:18 PM   #3 (permalink)
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well i cant really drive it cause its still on paper. but i still would like to know so that the wheels can be as close to the frame as possible
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Old 03-04-2002, 02:06 PM   #4 (permalink)
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I figure you measure how sharp your front axle can possibly turn and then figure out how to make the tires fit at that angle, there really is no such thing as too sharp a turning circle.
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Old 03-04-2002, 05:04 PM   #5 (permalink)
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I think there are too many variables to consider to make this calculation practical. Think of what happens when you turn with the locker on compared to it not being on. Is your foot on the gas? Out of gear? It's too much.

I semi-sorta agree with just makin it go as sharp as the axle will let you (or almost as sharp as it can to help save a few u-joints).
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Old 03-04-2002, 05:30 PM   #6 (permalink)
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opps I think i left out an important fact which is this is going to be ifs 2wd
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Old 03-04-2002, 05:43 PM   #7 (permalink)
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Draw it on paper to scale...don't forget the akerman effect...bwahahaha

time to do some basic research...google.com
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Old 03-04-2002, 06:45 PM   #8 (permalink)
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The basic formula is 2 * (L / sine(90-A))

where L = length of wheelbase

and A is the angle of the line drawn from the center of the offside tire to the point where the nearside tire centerline intersects the rear axle centerline.

There's also a small correction factor I left out that has to do with tire width and caster/camber but you can add 6-12 inches to the above and be pretty close.

Last edited by 92xj; 03-04-2002 at 06:51 PM.
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Old 03-04-2002, 06:57 PM   #9 (permalink)
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thank you that is exactly what I was tryin to find
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Old 03-04-2002, 07:57 PM   #10 (permalink)
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first you disassemble your rig, measure everything twice, take a course in calc and mech engineering, put everything back together, and drive it in a circle. for fun you can dip your front inside tire in paint and drive in a circle to make a nice, well, circle.
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Old 03-04-2002, 08:07 PM   #11 (permalink)
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Hey ztec, I was playing with that formula on my Cherokee and I don't think its right - I think it should be sine (A) not sine (90-A).

Turning diameter = 2 * (L / sine(A))

Here are the calculations on mine.
Wheel base 101.4, track width 58.0, max turn of inside wheel 37&deg (I guessed on this, I'll measure tomorrow).

With those measurements, a 37&deg inside wheel turn means the angle for the outside wheel would be about 27&deg (you can get this part by sketching and using sines to factor in wheelbase and track width).

Turning diameter = 2 * (L / sine(A))
Sine of 27&deg is 0.454.
101.4 / .454 = 223 x 2 = 446 inches or 37 feet, which is about right for my XJ.

I don't know why that first formula was wrong, unless they're just defining how to measure angle A differently than what I used, but this one seems to work.
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Old 03-04-2002, 08:13 PM   #12 (permalink)
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Quote:
Originally posted by aaronlosey
first you disassemble your rig, measure everything twice, take a course in calc and mech engineering, put everything back together, and drive it in a circle. for fun you can dip your front inside tire in paint and drive in a circle to make a nice, well, circle.
Now, why would anybody want to make a joke out of a serious college-level wheeling question? *I* certainly never make jokes about anything.
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Old 03-04-2002, 08:34 PM   #13 (permalink)
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Quote:
Originally posted by aaronlosey
first you disassemble your rig, measure everything twice, take a course in calc and mech engineering, put everything back together, and drive it in a circle. for fun you can dip your front inside tire in paint and drive in a circle to make a nice, well, circle.
Yes I relize that driving in a circle is the easiest way. But I need to find out that I have enough radius before I build it
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