Just make it front wheel steer.

This is my project.So I cant change it.

Is it all wheel drive, rear wheel drive or front wheel drive?

it is rear wheel drive ,as we build our car for BAJA saeindia 2012 competition.

Well then, you've got plenty of time to work on 2013, cause BAJA saeindia 2012 is already over.

but for documentation of project I need this angle ,so plz help me.

Can't do it. Measure it.

I could not able to measure slip angle by any method & I don't have any reference book or any other useful info on net of mechanical negative four wheel steering mechanism for finding out slip angle.

Could you find a large paved area, with the most flat, level, and uniform paving possible, and drive the vehicle in a circle? At very low speeds, the circle's diameter should match your drawing [I am assuming that it indicates maximum turn, or full-lock position]. If you drive faster, the size of the circle will increase despite no change in steering wheel position. Measure the new circle size, and redraw; although WHEEL angles are the same, TRAVEL angles will have changed. The difference should give the slip angle for that single condition. Drive faster still, measure larger-yet circle, and repeat. Eventually, you will have enough conditions to draw a curve showing slip angle changes vs. speed Still, it will be only the steady-state version for that particular pavement. Will that satisfy the needs of your project?

Entering or leaving a real-world curve, where road camber, body roll, rise/fall of terrain, braking/acceleration, and many other parameters affect the results, would take a major testing program. It MIGHT be possible to record steering wheel position while driving fast enough to exceed the low-speed, geometry-only steering situation, simultaneously recording (Video? Sensors? Both?) vehicle position throughout a driving session, and mathematically derive slip angles from the comparison. However, the math is far beyond my knowledge and resources, and may well be much more than you actually need or want. In principle, a full-featured math model should be able to predict all of the results, but this is super-computer territory, and small errors in assumptions could drastically change the actual results. "Full-featured" would include such things as how much fuel is in the tank, and where it has moved to due to the forces acting upon it, and the influence of that upon instantaneous CG position. Stiffness of the body structure, and its influence on the actual geometry, would also be needed; hence, "super-computer territory".

sir, I will work on this practical approch.

You would need to provide a drawing, or at least a sketch, for anyone to determine the relevant angle(s).

I don't see how the CG would enter the picture as far as steering geometry alone is concerned.

It may only be a difference in the terminology used, but the last I read, "Slip Angle" was the difference between steering angle and actual travel direction; it would vary with speed, traction between tire and supporting surface, tire construction (radial vs. bias-ply), CG, and very likely position of tire/wheel assemblies relative to frame/body due to spring compression or extension, roll angle, yaw, etc. It was a dynamic value, not static, and would likely be different for each wheel on a vehicle. A drawing would provide almost none of the required information; even an detailed CAD model would only take you as far as the geometry for ASSUMED values of roll angle, traction, distortion of the tire carcass, etc.

Can you re-state the question to clarify this? What is the definition of the angle you seek? In any case, we lack much of the needed information, as has already been noted by others.

Sir,

I am working on four wheel negative steering mechanism. We transfer the rotary motion of steering rod perpendicularly to rear rack-pinion by bevel gear arrangement.So for the calculation of cornering force I need slip angle of rear wheels as I am refeering book of Vehicle dynamics by Thomas Gillespie.I agree with you as you mention the dependence of slip angle on various parameter.I showed the drawing of this.If you know the other method or formula for calculating slip angle of rear & front then plz tell me.As I could not found the references on mechanical four wheel steering.

Mahesh, your circle center should be in line with the axis of the rear axle and not the CG of the vehicle. I can't say if your 9.46 degrees is correct or not because you did not provide other dimensions but...your geometry layout is incorrect since your circle center is not line with your rear axle, assuming of coarse you're referring to Ackerman steering. Having said this, true Ackerman steering geometry is more suited to low speed applications on solid ground. It's less important at high speed on loose dirt.

sir,

The project is for negative four wheel steering,but mistakely I not mention at the top.As far as four wheel steering (-) the instantaneous centre should be in between rear & front axle as I shown in the instantaneous centre diagram from my calculation & as per our wheelbase ,trackwidh ,velocity & all parameter considered.As I preferring the book of Vehicle dynamics by Thomas Gillespie.

What is meant by "negative steering? Is that neg.camber;neg.castor; neg, king pin inclination; negative scrub off-set. Same suspension front and rear?...it seems to me you will have to assume a lot? !

the negative steering means if front wheels rotate in right then rear wheels rotate in left direction,as bevel are used to transfer motion of steering rod to rear wheels . So it can not been changed.

Mahesh, what do you mean by "it can not be changed". Is your front steering mechanically connected to the rear?? Do the rear wheels turn opposite to the front wheels regardless of what speed the vehicle is moving.??

exactly sir,it transfer the motion of steering rod to rear rack-pinion by bevel gear arrangement as it can not be changed due to insertion of that bevel gears prior to front rack-pinion.As per our mechanical 4ws concern the rear wheels turn in opposite to that of front wheels & vice-versa regardless of speed.In our vehicle the speed attained is max 45km/hr & 4ws works effectively.

When you mentioned "baja" in a previous post I was thinking desert racing where they reach speeds of +100km/hr. 4ws (especially mechanically connected) would be a very bad idea! I didn't catch the "SAE". At 45km/hr you'll be fine. From a practical perspective, Ackerman type setups are not necessary for dirt because the tires don't grab like they do on pavement. From an academic perspective, I can understand the need to document your project. FYI, I have independent hydraulic 4ws on my trail Jeep. Works great off road but it's too dangerous for highway driving.

Yes Sir, you are right that this 4ws is dangerous for speed greater than 45km/hr. In india for baja competition (started from 2007) they will provide us 305cc B&S engine & there is adjustement of governer setting for each engine by them.So defenitely the speed of vehicle not reach above 45km/hr.SAE means society of automotive engineers.In India baja competition called as SAEINDIA BAJA.Sir, any idea about my question as you not mention any answer on that particular calculation ??

Your diagram shows that the front wheels turn at an greater angle inwards than the rear wheels turning outwards but I understand that you say it is exactly the same in the rear as in front.

Driven wheels will have a greater slip angle than non-driven wheels; Also with everything else being equal, will the tires with less of the vehicles mass on them have a greater slip-angle.If the "kingpin-inclination is greater in front, the front wheels will have less rubber on the road in a sharp turn....more slip!

To my mind you have to many uncertentys to arive at an answer without a practical test.

Only my commen sence speaking!

yes sir , I agree with you that driven wheels have greater slip angle .In our vehicle cg is 2:3 & also rear wheel drive so it is not easy to predict theoretically slip angles of front wheels & rear wheels.But frm geometry front wheels have 9.62 degree as shown in fig.Is it practcal angle of front or less than that ??

http://qbx6.ltu.edu/asik/Vehicle_dynamics_tw_dw.htm

Plenty of stuff on the web...should have what you need somewhere.

slip angle is determined by the alighnment of the tires when the vechicle is stationary compared to the change in tire geometry as the vechicle goes though a turn. it involves how the side walls react.

it is different on every tire/vechicle set-up. read [hughs] about supensions.