**The Science Behind Car Steering: Understanding Ackermann's Solution**

As far back as carriages, people realized that the inside wheels and outside wheels follow different paths when turning. To correct this, we use what's called an **Ackermann steering angle**, named after Rudolph Ackermann, who patented it in England for German carriage builder Georg Lankensperger.

The solution of Ackermann steering is rather elegant. If you take the rack, slide it back, and angle your steering knuckle position inside 90 degrees, you'll see that the tires, when rotated, are at different angles.

**Motorcycle Steering: A Simplified Example**

A motorcycle has two wheels, which eliminates concerns about inside and outside wheel paths. The path of the center of the rear tire is shown, with lines drawn at 90 degrees from each tire. This illustrates how the turn radius is the intersection of the angle of the front tire and the angle of the back tire.

**Car Steering: Applying Ackermann's Principle**

In a car, the angle of the tire that will create the least slippage is the tangent line to the circle at that point. However, this angle differs for the inside and outside tires if it's a straight rack and pinion with the steering knuckle in line with the wheel.

To achieve Ackermann's solution, the rack is moved back, and the steering knuckles are placed in line with the center of the rear axle. When turning, the two wheels will have different angles, allowing them to follow sliplessly along their respective paths.

**Adjusting Steering Angles**

The connection between the rack and the steering knuckle is made with a tie rod. To adjust how far your wheels can turn, you can move the rack forward or back. However, the steering angle is still determined by the relationship of the knuckle to the spindle of the wheel.

**Racing Applications: Pro-Ackermann and Anti-Ackermann Setups**

In racing, there are pro-Ackermann and anti-Ackermann setups. While friction provides grip, sometimes you want your tires to grab more. To determine sharp paths for the car rather than following them, a pro-Ackermann setup may be used.

However, in sharp-cornering tracks, an anti-Ackermann setup might be better suited. This is likely the topic of another video.

**Drifters and Unconventional Steering**

People who race drift cars often use unconventional steering setups. For example, Dai's car uses a heavy-duty delivery truck steering rack imported from China. The tie rods connect in front of the spindle to maintain space for turning.

However, drifting requires tires to be at the same angle, all the way through straight sections. This is opposite to the curved path desired in Ackermann's solution.

**Conclusion**

Steering angles are crucial in car design and racing applications. Understanding the principles behind Ackermann steering can help drivers and engineers optimize their vehicles for specific tracks and driving styles.

Make sure you subscribe to our channel, where we get to do cool things like visit Dai's garage! We also want to thank LastPass for sponsoring this video. We use LastPass to manage all of our accounts here at Donut.

WEBVTTKind: captionsLanguage: en- Hey, thanks to LastPassfor sponsoring this video!Stick around to the end and find out more.Today, we're talking aboutone of the most importantfunctions of a vehicle,right up there withgoing and not going.Steering!(distorted music)If we didn't have steering, we'd all justgo in a straight line,and never be able to turn,and that might work if the earth is flat.But, it's not flat you dummy!Steering covers a whole world of stuff,and there's no way I could fit everythingthere is to know about steeringinto one of these episodes.Even if I used my secret blinking code,which I know none of you have figured out,'cause I still haven't been rescued.So, we're gonna focus on rackand pinion steering system,and then take a look at steering angles.If y'all behave, we mighthave a very special guest.(racecar engine)Alright, special guest is Dai Yoshihara.Alright, rack and pinion steeringgets mentioned all the time,but, nobody talks about what it is.Well, 'cause it's not really that special.I mean, it's how cars turn.But, it sure sounds cool, huh?All it really means isthere's a rack that gets movedby a pinion gear, that's it.It's a pretty simple mechanismused to convert rotationinto linear motion.It really took off in the seventies whenArthur Ernest Bishop developeda variable-ratio rack and pinion system.A rack and pinion gear setis enclosed in a metal tube,with each end of the rackprotruding from that tube,a rod, called a tie rod,connects to each end of the rack,the pinion gear is attachedto the steering shaft.When you turn the steering wheel,the gear spins, moving the rack.The tie rod at the end of each rackconnects to the steeringarm on the spindle.The rack and pinion gearset does two things.One, it converts rotational motionof the steering wheelinto the linear motionneeded to turn the wheels.And, two, it provides a gear reduction,making it easier to turn the wheels.So, this system allows a better road feel,and, requires less effort to turn.Car's pretty heavy, andwhen you're turning a wheel,you're fighting inertia.If you're moving, thecar wants to go straight,and that wants to straighten the wheel.Some folks need a handwhen it comes to turning,so that's where thepower steering comes in.- You know, I like to getcertain amount of self-steering.- And, self-steering is whenyou let go and it comes back.- Yeah, I don't really let go let go,but, you know.- Spin it in your hand?- Yeah, kinda yeah.- Okay.- More, the better, to be honest.'Cause, when we do like lock to lock,it really quick, so if I try to feedsometimes it's not fast enough.- In this case, partof the rack's modifiedto form a hydraulic pistonand cylinder arrangement.The cylinder's fed on two sidesby openings, to whichfluid lines are attached.The piston's connected to the rack,and moves between these two openings.When pressurized fluid is fedto any one of the openings,the piston gets pushed, andmoves in the opposite direction,dragging the rack along with it.At the same time, the otheropening vents out the fluid,on the other side of the piston.This is how power's provided,which, significantlyminimizes the effort neededto steer your vehicle.The fluid's stored in a reservoir,and gets pressurized with thehelp of a rotary vein pumpdriven by the car's enginethrough a belt and pulley arrangement.It pulls the low pressurefluid from the reservoir,and pressurizes it beforesupplying it to the cylinderand the hydraulic steering system.So, the fluid pressure doesmost of the steering work,while the driver controlsthe direction of the turn,with the help of a valve system.We poked around onDai's car and it ends upbeing that hanging out withhigh horsepower monsters,waiting for a run, heatsup your steering fluid,so it won't work right.- These guys sit in aline with cars runningfor like, up to three hours straight.When you start boilingover the temperatureof the power steering fluid,it starts to break down.So, then your power steering gets weak,and then it eats otherparts inside the pumpand you get cavitation.You don't go this far sliding the carin the wrong direction withoutpower steering assisting.- And, in your car, with abelt running off the engine,even if you're not turning the wheel,you're sucking a little power.So, now we're seeing more and moreelectric power steering popping upto replace these old hydraulic bad boys.Electric power steering uses inputfrom sensors on the steering wheelto apply assistive torquevia an electric motor.Not only does this get rid of the dragon the engine from the hydraulic system,but, this is part of the same systemthat gives us lane keep assist,and camber control and crap like thatfrom the car commercials thatrepeat all the time on Hulu.Okay, so what happens nowwhen you turn the wheel?Your car turns.But, it's not onerevolution to get the wheelsto turn all the way.The steering ratio is the ratioof how far you turn the steering wheelto how far the wheel's turned.For instance, if one complete revolution,or 360 degrees, of the steering wheelresults in the wheels ofthe car turning 20 degrees,then the steering ratio is 360divided by 20, or 18 to one.I like those odds.A higher ratio meansthat you've gotta turnthe steering wheel moreto get the wheels toturn a given distance.However, less effort's requiredbecause of the higher gear ratio.The gear ratio on mostdaily drivers' chosenso that you gotta make upfour complete rotationsof the steering wheel to get the wheelsto turn from lock to lock.Generally, lighter, sportier cars havelower steering ratios thanlarger cars and trucks.The lower ratio gives thesteering a quicker response.You don't have to turnthe steering wheel as muchto get the wheels toturn the same distance.Dai's car takes only one and a half turnsto go from lock to lock.And, lock to lock on thisdrift missile is 140 degrees.So, he's got a steeringratio of four to one.- Really?- Yeah.(laughing)- Wow, I didn't even know that.- It's crazy!And, some cars havevariable ratio steering.Which uses a rack and pinion gear setthat's got a different tooth pitch,that's the number of teeth per inch,in the center than it has on the outside.This makes the car respondquickly when starting a turn.The rack's near the center.And, it also reduces effortnear the wheel's turning limits.So, now let's get into steering angle.Steering angle can refer to two things.First, it can be the degreeto which a wheel can turn,affecting the turn radius.This is something that'sdifferent on all cars,and it can be pretty easily modified,but, we'll talk about that in a second.The second meaning of steering angleis the difference between the angleof the two wheels when turning.Why is this important?Now, your car and Dai's car havedifferent problems to solvewith that rack position.So, let's start with normal people cars.As far back as carriages,people realized that the inside wheelsand the outside wheelsfollow different paths.To correct this, we use what's calledan Ackermann steering angle.It's named after Rudolph Ackermann.But, he didn't invent it.It was invented by theGerman carriage builderGeorg Lankensperger in Munich, in 1817.Ackermann just patented itin England for ol' Georgie.The solution of Ackermannsteering is rather elegant.If you take the rack, slide it back,and angle your steering knuckle positioninside 90 degrees, you'llsee that the tires,when rotated, are at different angles.Now, let's pull back.Here's a motorcycle going around a circle.It's just got two wheels.So, there's none of the concernswe were just talking about.We're showing the path ofthe center of the rear tire.If we draw that line at90 degrees from each tire,you see that the turnradius is the intersectionof the angle of the front tireand the angle of the back tire.Easy peasy.You also see that the pathof the front tire's slightly widerthan that of the back tire.The longer the wheel base,the greater this difference.Now, back to a car.The angle of the tire that'llcreate the least slippage,is the tangent line tothe circle at that point.It's different for theinside and outside tires.If it's a straight rack and pinionwith the steering knucklein line with the wheel,the wheels are at thesame angle to one another,and they'd slip.The elegant solution in Ackermann's patentwas to move the rack back, andplace the steering knucklesin line with the center of the rear axle.Now, when turning therack from left to right,you can see that the twowheels angle differentlyfrom one another, so while turning,the two tires have different angles,and follow sliplesslyalong the respective paths.On cars, this connection'smade with a tie rodthat connects the rackto the steering knuckle.You wanna adjust how faryour wheels can turn,you can move the rack forward or back.But, the steering angleis still determinedby the relationship of the knuckleto the spindle of the wheel.In racing, there's pro-Ackermannand anti-Ackermann setups.This is an oversimplification,but, because friction is grip,sometimes you want yourtires to grab more.To determine sharp paths for the car,rather than to follow them.So, at rack position,further to the front?- Gives it what they wouldcall like a crab walk,where both wheels are very parallel.So, the thing can just go sideways,versus it being back in this scenariowhere it doesn't have as muchequal Ackermann steering angle,which kinda causes the carto follow a track more.Oval tracks are more likelyto use a pro-Ackermann setup.But, in sharp-cornering tracks,it may be better to use anti-Ackermann.But, that's probably another video.Okay, now let's talk about drifters.(solemn piano music)No, people who race drift cars!Okay, first you got somuch crap up in those cars,you probably won't beusing a traditional setup.Dai's car is right-hand drive,so, he had to import a steering rackfrom a heavy duty delivery truckthat you can only find in China.That's research.But, to fit everything around this,and keep things from hittinganything else when he turns,the tie rods connect infront of the spindle.If you want to maintainan Ackermann setup,you continue the angleyou had before the wheel,in front of the wheel.But, in drifting, you might not wantan Ackermann steering angle.Remember, Ackermann's designedto help wheels follow a curved path.Some tracks will require a carto make a nice curvedpath around the turn.In which case, the wheelsshould have different angles.But, other courses couple these turnswith super straight transition,where the car goes sideways,behind the front tires.In these parts, you want the tiresto be at the same angle, allthe way through the straight.Like, to swing the back out 140degrees to either side, man!Look at that guy go!(race car engine)So, it's up to a driver and his crew chiefto figure out what setup's bestfor their style, and the track.Steering angles!Make sure you subscribe, it'show we get to do cool thingsand go to places like Dai's garage.And, thanks again to LastPassfor sponsoring this video!We have so many differentaccounts here at Donut.We use LastPass to manage all of that!Seriously, we used to beat events and been like,"Hey, Eddie! What's the password"for our Instagram?".And then, you wind up getting locked out.LastPass relieves the troubleof looking for passwords,and the anxiety around gettinglocked out of your accounts.With LastPass, you don'thave to write, remember,or reset your passwords.It lets you keep track of 'em easily.So you can stay sane, like me.Put your passwords onautopilot with LastPass.How's it work?LastPass autofills your credentialson mobile sites and apps,for iOS and Android.When you open up an app, or a site,it just fills in yourusername and password for you.Making a login easy.You get unlimited password storage,free cross-device sync,and password breach alert,where they send you an alertif your password is breached.Click the link below to findout more about LastPass.We got a bunch of new shows on the horizonand subscribing helps us make 'em.Special thanks to Dai Yoshiharafor letting us visit his garage,take a look at that sweetsweet drift missile.Follow him @daiyoshihara.Follow us @donutmedia.Follow me @bidsbarto.Check out this episode on turbo,and check out this latestepisode of Miracle Whips,'cause it's pretty cool.Don't tell my wife, I renteda garage next to Dai's.That's not weird.