Ackerman Steering – Explained

Ackerman Steering – Explained


hey everyone in this video I’m going to be going over the acraman principle or Ackermann steering now I want to go into this because I’m going to start going into four-wheel drive and all-wheel drive and it’s an important principle to understand before I go into those the name acraman comes from a guy named Rudolf Ackerman who actually was the guy who patented this idea the problem was it wasn’t his idea the German there was a German inventor that came to him he was a lawyer Rudolf Ackerman and so he patented the idea but somehow his name got placed on it I’m sure he did that but so it’s not really his idea but anyways he’s got the name what what’s happening here so now back before the Ackermann steering was around some of the tires would slip because they had come to a different point so after men steering the reason it exists is that so your tires do not slip when you go around a corner now how you achieve this is by having a central point at which all your tires are rotating around so you can see that the angle of this tire this inside left tire is going to be greater than this outside right tire so with that angle being Reiter they can come to a central point and then all four tires can rotate around one point which means the tires don’t have to slip as they go around if these two had the same angle then they’d have to slip around some uncommon point and so that it wouldn’t be it wouldn’t work as well especially at high speeds so the acronym principle is is great for for solving this problem now one thing that you have to see when you look at this is that look at each path each radius so each tires path has a different radius now what that means is each tire is rotating at a different rate so the one on the outside travels a further distance than on the inside in the same time so it’s rotating more quickly so in descending order the angular velocity of each tire goes for one – two – three – four that’s the descending order so this is rotating the fastest and this is rotating the slowest because it’s got the smallest distance to travel now what does this mean well this means your right side is moving faster than your left side when you go on the left-hand turn and vice versa if you go on a right-hand turn also what this means is that the front tires because they’re traveling a greater distance as you can see than the rear tires they are moving faster than the rear tires when you turn so this is the real reason that you need a differential and four-wheel drive if you’re if you’re in four-wheel drive on a pavement or something like that we have enough traction enough grip then you’re going to need a differential so that you can split the speeds between the front tires and the rear tires otherwise you’re going to have some buckling it’s not going to work out and you’re going to have you’re going to wear the tires and you’re going to be slipping you’ll have understeer so you want it so that you have a differential if you put in a center differential right there then that would allow these tires to rotate at a different rate than these tires and then you put in a differential at the front and differential the back and that would allow each of these two tires – once again rotate at different rates so this is important before I go into my four-wheel drive and all-wheel drive explanations so I really hope this makes sense and then I’ll be going into these more complicated ideas of four-wheel drive and all-wheel drive

Only registered users can comment.

  1. If i had a little mechanical design background, and wanted to pursue a career in say automotive design, would a mechanical engineering degree be the best way to go? I am a drafter/designer in civil engineering. I am planing on going back to school to complete an engineering degree, and would prefer to do mechanical to civil. I love it!

  2. I'm not sure what the best way to go is, but it's certainly one way of doing it. I've written an article on my website with a bunch more info: howdoesacarwork(dot)com -> FAQs -> Future Plans.

  3. can you tell me wat s ackermann angle and how to calculate it? does the toe out affect the ackermann angle?

  4. There are infact some cars that steer on all four wheels.
    One exempel of that is the Nissan Skyline GT-R.

  5. It's quite odd that WRC cars are 4WD, and they don't have a center differential. New regulations simply banned those.

  6. help help help
    in case of a two wheel drive when the frontaxles dont have differential or any other thing that changes speed, how does both ie left and right front tyres move at different speed.
    or do they move at same speed,if so wouldnt one tire slip

  7. Yes, one tire would slip. However it's unlikely that any relatively modern car not have a front differential, it's pretty standard.

  8. All of you guys are so spun out…Ackerman is about tire wear…rolling resistance…when a car turns…it defines a sgment of a circle…THE CENTER of the circle defines the radius…as the car turns..the Tires describe four DIFFERENT radii…the tires need to be 90° to the radii to promot travtion, reduce wear…Mr Ackerman was an employee of the Conastoga wagon Company…this shit is nothing new..

  9. Thank you for making these videos! Loved to get the F1 radiator explained, but in this one did you not skip the actual explanation of the mechanics? I mean shure wheels go around at different speeds, but how to achieve the different turning angles for the inner and outer front wheel, mechanically some might ask.
    I found it at Wikipedia though:-)

  10. Cool video… I always noticed on cars that the inside tire always seemed turned out farther than the outside tire… now it all makes sense. Keep up the good work!

  11. I like your explanations.  Would really like to see one on Bump Steer.  Perhaps sometime you could do one on that subject!

  12. Hi @Engineering Explained , I notice that front wheel axes cross at the center of the circle of the curve, that means they are not parallel. I mean, not only do they spin at different angular speed, but also they steer at different angles. Is it really that way?
    Thanks very much for your time, I recently started to watch your videos and you are the best at explaining, it's all very clear, interesting and useful. Thanks a lot.

  13. No idea what all this is about – Ackerman steering and differential gearing were around long before the motor car. Horse drawn carriages had wheels that revolved independently of each other so scrubbing wasn't a problem. The reason Erasmus Darwin came up with the idea of Ackerman steering was because on one of his medical calls his carriage overturned and he suffered a broken leg. He was sitting outside of the triangle subtended by the front axle's central pivot and the rear wheel hubs when the axle turned through 90 degrees, his portly stature caused the carriage to fall over. Introducing kingpins and four point location (as opposed to three) made for stability. This is why this arrangement is used on motor cars. Differential gearing is used to solve the problem of wheels revolving at different speeds when cornering. 

  14. It has been shown in the video that all the wheels turn for a common center.
    So, the angular velocities of all the wheels will be the same.
    Their linear velocities would be varying. ( as the radius from the center varies)
    The descending order discussed might be true for linear velocities, but not for angular velocities.

  15. okay, my question to anyone here: does the most tight turning circle of a car change if it's going at different speeds, aka if the steering wheel is at full lock can you turn sharper at certain speeds, what about reverse vs forward? is it always the same?

  16. are the left and right front tires each at a different angle ?

    if you turn the steering wheel than the angle of both tires is the same no? but only their speed differs in a corner

  17. +engineeringexplained: if front is moving faster than rear than how can ang. velocity intermix them as 1,2,3,4 ? This implies that right moves faster than left which is correct. If Front moved faster than back should it be 1,3,2,4?

  18. as far as controlling ackermann and bump steer does a rack and pinion setup or a bellcrank setup offer better control and handling?

  19. It's important to note that the condition illustrated in his drawing is ONLY valid for low-speed cornering, ie. where there is no slip angle at any of the tires. When this is the case, the instantaneous center of rotation of the chassis will be about a point that lies on a line that is colinear with the rear axle. As the velocity increases, and slip angles develop, that point of rotation will move forward, as the car develops a side slip angle (beta). At some velocity (known as the tangent velocity) the front and rear wheels will describe the same radius. Find an empty parking lot and drive at a constant radius at a very low speed. You should notice that the car corners with a 'nose out' attitude. As you increase the velocity (and therefore the yaw rate) you will notice that the car begins to 'nose in' as the car develops side slip angle, and finally has a tail-out attitude. Again, the condition described in the video is only valid for low speed maneuvering (as if you were pulling into a parking space).

  20. thank you very much for all these great vids!!! anytime I question something in the mechanics of , or I need a definition explained in visual I come here. Everytime. thank you. thank you. keep it up!

  21. Hey jason!
    Can you make a video on Front Steer vs Rear steer, 
    what should be the Ackerman percentage for off-road cars?

  22. Hello. Can you please make one video about car steering ratio ? I'm interested how i can count car interior steering wheel degrees and wheels turn degrees.

  23. nice video.. but i just hate the way to create chapping sound every time u start a new sentence..
    besides the video was helpful

  24. 90% of the vehicles I see still have the outside tire plowing in a full turn. Trucks cars van buses doesn’t matter. No vehicle truly has a accurate steering system

  25. Been watching your videos forever.. looked up ankermenn and noticed… i never subbed.. well thats fixed xD

  26. Hi, could you give me an idea of whats happening to my vehicle. I have done wheel alignments to my car several times however i still get understeer.. It is a constant 4wd car, manual with transfer case. CV's are good.

  27. Question: Why do sports cars have terrible turning radiuses (Raidia?) ? Is it only because of the handling? That you want a stiffer, more stable, suspension?

  28. Good video, but not as good as your current videos. You've refined your craft. It's spelled Ackermann with two Ns. Invented by builder Georg Lankensperger in Munich in 1817. You can see this easily in many Lego vehicles, where the steering mechanism forms a trapezoid rather than a parallelogram.

  29. Can anyone explain, if he says front wheels move faster than rear wheels as you turn, shouldnt it be 1 and 2 at front wheels in terms of velocity?

  30. Good to revive a old topic but thanks for your video now I understand how AMG 4matics are good for nurburgring but sucks at low speed turns. Can you explain a bit more on its negative effect for example causing Tyre crabbing or juddering at low speed turns in cold weather? Merc owners are so angry about their expensive car making embarrassing turning noise around town.

Leave a Reply

Your email address will not be published. Required fields are marked *