Roll Center & Vehicle Body Roll - Explained
Вставка
- Опубліковано 8 вер 2024
- The body roll of a car is influenced by the distance between the roll center and the center of gravity of the vehicle, The larger this distance, the larger the roll moment, and thus the more body roll the vehicle has. By manipulating the suspension geometry, you can alter the amount of body roll by increasing the height of the roll center and bringing it closer to the center of gravity.
Please feel free to rate, comment, and subscribe!
And don't forget to check out my other pages:
Facebook - / engineeringexplained
Official Website - www.howdoesacar...
Twitter - / jasonfenske13
Instagram - / engineeringexplained
To help create more videos, check out my Patreon page!
/ engineeringexplained
NEW VIDEO EVERY WEDNESDAY!
Currently working as a vehicle dynamics engineer in a shock absorber company, and i must say this is the most accurate vid i have ever seen, great job man, all your vids are gold! I love all of them and i put a smile on my face when i saw a vid related to my job :) you're helping me a lot with knowledge about all cars' areas
You've got a very good way of relaying technically complex information. Impressive teaching skills.... quite a rare thing. Please keep it up!
0:06 You lost me right there
DarkNight I made it to 0:07. Looks like I'm 16.7% smarter than you.
How don't u get it it's simple.
spoon games And how don't you get that they don't get it it's simple.
+spoon games If you are inquiring seriously, the definition he wrote for Roll Center is the definition for Roll Axis.
no fat chicks or car will scrape. got it!
As a mechanical engineering student and as a car enthusiast, your channel is the best place to go :D
After this video published ->Extended ball joints experienced an increase in sales hahaha. Good video
Wow! Your explanation was very complex, technical, mostly importantly; delivered in such a way that a person who doesn't have any idea about automobiles and how they functioncan simply understand/comprehend.
All of the videos that you post are my cup of tea man! More people need this type of automotive education because it honestly helps more than anything even with basic driving characteristics of daily drivers. I'm always looked at like I'm insane when I bring up suspension geometry and it's sad. Most people just want looks with little to no regard for safety and TRUE performance. Thank you so much for doing what you do and never ever stop!
A very nice explanation of what and where is the roll center. I think it would be helpful to explain that the optimum roll center height is well below the CG for both handling and road holding reasons. Rougly speaking, if the roll center is about 1/3 of the way between the ground and CG, it cancels 1/3 of the roll. The anti roll bar cancels another 1/3 and the remaining 1/3 should be allowed to happen. This deserves another video!
And here's the question. we have the macpherson suspension. Normally we lower the car (front macpherson) , as low as the tire size allows and the handling is improved as the result but in macpherson, the upper A-arm is the strut top and is fixed and has little to some mild angle. We lower the car, the lower A-arm is tilted downwards. It means if the angle of < is positive, turns toward zero, or even negative. The instantanious center is altered downwards. The biggest impact is noticeable on suspensions with short A-arms. The car that runs high has a jacking feel of one side. (body roll?) The same car lowered has great steering response, excellent cornering and fun to drive. So, on the contrary of what u'r saying, lowering the roll center helps until the jacking effect is minimized. I believe this is why we lower a car front 5 cm, but lowering the CG 5 cm doesn't seem to have a noticeable change. This is why lowering cars with solid axles or lifting them like offroad cars doesn't change things... I'm pretty much confused. with lowering the body roll decreases. but if we increase the moment length of body roll we will have more body roll.
Thank you Jason for another great video! It would be awesome if you could do an analysis of your Integra's suspension design. What the roll center is, what factors were behind some of the choices Honda made and how the basic design can be improved upon by regular enthusiasts (if it can at all). Thanks again for everything, love your channel!
Jason I saw the mathematical composition on your board and I knew I was in trouble. You are too smart! Thank yoU!
Thank you so much for taking a complex system and carefully explaining the components in an understandable way.
Thanks for the Video - One of your more difficult lessons. Ill re watch it a few times to get my head around it.
Thanks for these videos I used to be the most illerate in terms of how parts of a ride work but I'm starting to get it now
Hey, just wanted to say thanks for the videos you helped me learn more about cars and in detail whit good explanations keep it going man !!
Note that having your roll center above the ground makes the load transfer happen instantly as you begin to turn (don't have to roll the car to load up the springs). This can influence over/understeer (higher rear roll center -> oversteer)
Reply to very old comment - I'm just curious, why is instant load transfer in turn-in desirable versus waiting for the springs to load up? And are you referring to lateral or vertical load transfer?
@stephenabraham6787 My understanding is that if you aren't wasting energy in compressing springs, loading sway bars etc before the car turns in, it's going to turn in faster.
Pretty much, it has to lean before it can actually turn. The less it leans, the faster it turns.
I love these suspension design videos, it's overlooked so much and there's so much to learn from it
Great video, this is a complex topic and you explained it well.
How can anyone dislike such a gr8 explanation ..if they dislike please upload their own video otherwise dont see it .....it is not for them who dislike
I didn't hit the dislike button. But i think those people know the truth of (The rolling axis is not the axis where the body rotates wrt. The ground)
HELLO DEAR I AM YOUR FAN FROM PAKISTAN ; I have a question that my car radiator support is bent from bottom side of vehicle from previous owner. I have issues of. car wandering from my side specially when windy and increased body roll . suspension is checked out no issues found . so can hit to radiator supper at front can change the geometry of body roll ?
Superb explanation man. Its very simple and easily understandable!!!
Man I love your videos. They make so much sense...
1) What happens if your roll center is above the CG?
2) Does the height of the roll center above the ground matter? Or is it only its relation to the CG?
3) Why is everyone so concerned with the roll center being below ground?
If i put the roll centre above the centre of gravity there are any drawback? I have seen the swincar of Mecanroc and it uses sprung mass inertia to lean to the right direction and keep the wheel pressed to the ground. I would like to have my own car to do that
This is a great explanation! I guess this is why 86/Brz are so great to drive :)
There might be a few reasons for that. ;)
Engineering Explained hey bro i truely apreciate your videos :D , ive got a suggestion for your future videos could you plz use a 3d modeling software and explain the stuff on a green screen with the subject like a hologram ? can you do that please ?
axon magnus that is exactly what I was thinking about :-D but this minimalistic style is also cool ;-)
Yaaaaaa
I just sat through your entire suspension series. I consider myself to be quite clued up on cars having built a few and worked on many. You have taught me a thing or two. Great content - well done. May I suggest working on the way you present yourself a little better in terms of appearance. I really don't care what you look like, I just feel that you would reach a greater audience, also maybe try to go digital in presenting your diagrams etc? Your content is spot on - which is why I'm a fan. I appreciate your efforts, keep up the great work man.
MrCassidySA If appearance matters that much, the viewer can go elsewhere. The internet is incredibly diverse which is what makes it so wonderful. I like to teach; I'm not too worried about how you feel I look.
one thing you forgot to mention is, the center of gravity is figured from unsprung weight. that means all suspension components are removed (including the rear diff on rwd) and only the complete body and frame are used to find the cg.
What happens if the roll center of one end is above CG?? How does the body roll then? And what happens if the roll center is below the ground?? Why is it undesirable?? And why do off-road cars prefer more roll???
I believe the further the RC is from the ground, it creates a jacking force, the RC above the COG exerts more force on lifting the outside wheel than it does pressing the inside tyre into the ground which creates some undesirable handling characteristics
man you are a genius I loved each one of your videos and leaned alot, usually I dont comment saying thx on someones video after learning something but you are different, while I don't understand wtf you talking about in 20% of your vids since they are too technical for me I dont know any other person that knows more than you without a degree, idk how do you know these things Im guessing you are stealing from some website lol but still its good cuz I dont read.
oh shit you are a mechanical engineer so thats why I don't understand shit lol
first i wanna let you know that you are doing a great job
well i have a doubt
how is center of gravity related to my roll center(in context of minimize the body roll)??
the centrifugal force acting on the CG produces a torque about the roll center. This is known as body roll.
what are the average role centre heights recommended for racing cars? once you have determined the role centres how do you determine the heights of unsprung mass?
Is it possible to predict whether independent suspension versus solid axle would have less roll.
Would you say that independent suspension was less role-prone?
I'm not sure if I can make that leap based on this example.
That's not a knock on you by the way.
great upload, love getting back to the whiteboard.
Hi! First let me thank you and congratulate you on your channel. It's one of my favorites on UA-cam! Question: I see Tesla model S has larger brake discs in the back than in the front, and I am wondering if that has to do with the center of gravity being so low relative to the axles, or if there is another reason for this. Would love to see this explained in one of ur videos! Keep up ur outstanding work 😀
Nice Explanation.. Keep it Up!!!
Can you make a video explaining MagnaRide? Maybe even a video comparing MagnaRide technology to air-bags and traditional struts?
So how would you calculate roll centre for a go-kart which has no suspension? Would roll centre be the same as the CG?
IC is NOT the instantaneous roll center about which the suspension links are rotating! it is the instantaneous center of rotation for the wheel carrier. Please
awesome video as always!!!!
I need to knw about the roll centre of three link and trailing arm suspension.. Plz come up with that video..
We build off-road cars and one off the goals is to have a massive oversteer effect, the cars are rear driven, for that we need a lower roll center height at the back?
Corsários Baja probably not the best way of going about it as roll centres are not easily changed. Your better off tuning the over steer and understeer characteristics with springs and swaybars
Thank you so much!
Could you comment on when you would want a lot of roll center? Off road on tight courses?
Thankk you!!!!!!! Always great! Keep up the good work
Thank you. Please can you explain where the roll centre is on a panhard rod equiped live-axle vehicle?
Can you do a video on how torque is split in an uneven ratio in four wheel drive systems please
Similar topic.
When towing, it would be ideal to have the tow ball on or close to the tow vehicles roll center?
Thanks for the great videos.
Oh boy, the white board videos kill me. I try so hard to get it, but without a demo it's all over :(
How did you determine the angle to draw the intersecting lines from the wheels
(Great videos)QUESTION, I have an FJ Cruiser (Stock) and I get a lot of body roll, What do you suggest to correct that? Thanks.
During the turing the body roll around the roll axis but in many 6dof vehicle models i had seen that they take roll moment around the centre of gravity. So why is that ? The roll moment must be taken about the roll axis .
Question!! What if c.g and r.c is in one point?(I mean aligned) then there is no roll on carbody?
At 2:41 he says handling is better if roll centre is near to CG but isn't it supposed to be other way around?
What about the non-rolling overturning moment? Would be nice to hear something about that
question: if the 2 wishbones arms areparallels, how can i find the istantaneous center?
What would the equations of motion for the body roll be? i have a half car model in MATLAB however, its the front & rear. I was wondering if i can just use the same model but change the equations of motion in the system to simulate the roll
Isn't camber changes w/ suspension movement good for handling? Jason said that in his double wishbone video.
So how would you calculate the roll center position for a car with leading/trailing arm suspension?
It all seems very arbitrary - I not sure that you explained why the "dotted lines" are drawn as they are, and why they should be so
Video on front view swing arm geometry,side view swing arm geometry and anti features in suspension....
How does this work out for solid axles?
Do we have a video on roll steer or bump steer? I have a doubt about oversteering if my tie road length is longer than the control arms.
I've been studying this alot to help me understand why everybody is sayin NO to lowering car on McPhearson strut (mk1 VW golf)
I sort of understood it before but your video confirms my thinking, great job.
You also confirm my thinking that roll center changes when you corner-
but that implies that pretty much all mcphearson strut suspension desings put roll centre deep below the ground when cornering, so should it really be considered when choosing track day suspension?
Also, could this be used to move CG under roll centre? Would that make car lean against the corner like motorcycle?
I hope you answer, I cold think of hundred questions for you but I will contain myself (for now :D) I love your reviews also, keep them technical for us James May fans haha
Hey there! I got a question, why is the driver suspension lower than the passenger? I'm driving on the right hand side.
Are there any science behind why or just not set up properly? If adjusted will my alignment need adjusting?
Front are macpherson struts w/ fully adjustable coilovers
Rear are Multilink w/ fully Adjustable coilovers
Thanks!!
What if the upper control arm is angled such that the ball joint is lower than the attachment point on the frame (as it is on many cars)?
It’s like Forcé x distance = torque
what happens when we use different suspensions in rear and front. will the roll center axis be disturbed?
will front double wishbone and rear McPherson produce good result for rear wheel drive
it would be great if you could upload a video on Force based and kinematic based roll centres.( please refer a paper on roll center[force application points by MITCHELL] and about the geometric and elastic load transfer.
Okay, I have many questions---1. say we let the RC and CG meet by our design, and now the car corners, there will be a net load transfer happening. now as we have zero roll due to our geometry, means our spring won't take any loads of load transfer and all the vertical load for load transfer will be passed through the A-arms to the sprung-mass such that sprung body doesn't roll? obviously, we will have very high jacking but still, is this correct?
2. Suppose we have RC above the CG, then we will have pro roll right ? the car will roll into the turn but the wheel loads will be as usual as a higher load on the outside and lesser on the inside which will be reacted by the A arms towards ?? i am really confused !!! ,due to cornering forces and the net moment on the car.?
HELLO DEAR I have a question that my car radiator support is bent from bottom side of vehicle from previous owner. I have issues of. car wandering from my side specially when windy and increased body roll . suspension is checked out no issues found . so can hit to radiator supper at front can change the geometry of body roll ?
good video bro but i have a doubt what happens when a arms are parallel and what if they meet outside the vehicle?
Question: does me knowing this make me a smart person? Probably yes, but no matter how well I understand it or put it into practice I'll never be as smart as the man that did the original math to work this out... 😅 we're so lucky to live in an age where most complex equations have already been discovered ^^ all we gotta do is remember simple methods.. God I wish I was smart enough to discover an engineering breakthrough!
How does the lateral weight transfer during cornering depend upon the roll moment generated.
maybe you want to give a (very) brief explanation of what a roll center/body roll is. The best teachers I ever had were ones that could explain the science behind the idea, but also introduce the idea by giving a real life example. Example: "We've all felt that moment when we drive too fast around a turn...".
I recognize you're an engineering channel, and not catering to the laymen, but perhaps spending no more than 15-20 seconds on more poignant introduction could captivate a wider audience, resulting in (a) expanding your marketability, and (b) increasing the intrigue of potential engineers.
+Engineering Explained Can you please place the frame a bit lower , as I'm unable to view the diagrams that you've drawn and the caption simultaneously
Very nicely explained! Thanks for the upload. A question: any way to know how to minimise the roll of an already designed and manufactured consumer vehicle (boxy, tall family car)?
Swaroop Bhonde beefier sway bars would be my personal advice.
Swaroop Bhonde anti role bar will help, stiffer en flatter tires (more solid rim less uncontrolled bounce rubber), removing mass, lowering mass (drop the battery to the floor en u will Feel the differences).
the cheapest way is to fold down yore back seats when u dont use them.
SoY_FooD You really have to move the weight down, so lowering the car or making it lighter are the best options. Anti roll bars/sway bars wont do anything to actually change your roll center, they just resist the forces more.
true but it will counter some of the effects getting the result fore little money and needing less weight reduction to get a good ride
SoY_FooD Mat Guest Folding down seats is really something that looks promising! Will be trying out for sure! But beefier Sway Bars would in turn reduce the overall roll while not touching CG as well as Roll Centre? I believe Roll is basically toque exerted by the force (this force will get reduced due to Sway Bars?) while the distance between CG and Centre of Roll being the arm? Am I correct?
Joel Sägesser Sway bar modification would means possibly voiding warrantee? Will look out if anyone near place has expertise in it!
Question: What if upper and lower control arms are parallel? RC = CG?
i don't understand (unRelated to _this_ particular video... but): doesn't "launching" put stress on vehicles, especially manual transmission? The whole idea of engaging clutch while there is a big difference between wheel speed and engine speed- is this not stressful on the car and lead to premature wear?
If i introduce a leaning mechanism just like in tilting trike will i be able to overcome the roll over effect ?
Wayalife just talked about Roll Center and I still don't understand it. Can you do a solid-axle explanation of Roll Center?
Hey i hope you'll be able to answer this but since i got my first car, i have 3 questions.
1- im losing oil in compression returns. Is there a way to eliminate this issue?
2- is a cold air intake dangerous in winter?
3- is it true that slowing down on compression is damageable to your engine?
Thanks! Oh and great video, keep up the good work man :)
Gabriel Thériault
1. Not sure what you're asking.
2. I wouldn't say so. Bit of a generalization though. What about winter makes it dangerous? Super low temps? Shouldn't matter.
3. What is "on compression?"
1- there is a hose coming from the cylinder head that brings little compression leaks back to the intake. lots of oil is flowing through this hose and i wonder if there is a way to fix this.
2- i was told that a cold air intake here in canada is bad in winter. i was wondering if any problems could occur because of the cold or maybe snow.
3- you know when you downshift but you dont apply throttle, just to slow down without braking? I was told a lot of times that i was bad for engine health but deep in my heart, i dont think its true and you are pretty qualified to tell.
Gabriel Thériault
1. Maybe oil catch cans?
3. That's what oil is for, no problem letting off the throttle. In fact it's preferred in scenarios where you'd otherwise have to brake (going down a big hill) as your brakes won't overheat.
Alright much thanks! I'll look into an oil catch can
Gabriel Thériault Your oil problem could be a faulty or dirty PCV valve. This valve controls the flow of gasses back into the intake. When working properly the valve gets sucked closed by the intake vacuum at idle/closed throttle. It's possible that a stuck-open PCV could cause it to suck in an abnormal quantity of oil.
The valve is usually quite easy to remove and fairly cheap to replace. Sometimes they get blocked with sludgey oil and can be removed and cleaned out with some carburettor cleaner or similar solvent.
Engineering Explained Please, add subtitles. It is not easy to understand everything that you explain for those who do not speak English. I would greatly appreciate it.
With a short circuit asphalt race car that only turns left. Would you try to get the roll centre to the left of centre?
How can I fix roll center and drive angle issues on a lowered front wheel drive car when adjustable parts Don't exist for my car??
as a vehicle dynamics engineer, i'm rather skeptical to you trying to "minimize" everything. its always "optimizing". eg: high roll centers will have more jacking force. thus low traction.
Onkar Mohite Haha, the better word is most definitely "optimize." Typically it's better to let the spring/damper combo work out the road rather than stiff control arms, agreed! It's one of the many pieces of the puzzle.
To get the center roll in a macpherson system we take the axis of the damper or the axis of kingpin?
I know it's kinda late but the axis sholud be a line between the ball joint and a strut mounting point.
Would the same process apply to a suspension where the angle above the x-axis is higher for the upper control arm than for the lower? Take Formula 1 cars for example. It seems like on the Ferrari F2012 specifically and I believe a few McLarens both control arms are angled upward but it at least appears that the upper control arm is at a higher angle. would the instantaneous center just be outside the car and possible below the ground?
How would car behave if you could make these two lines kolinear? i guess that then you would have no roll at all? force would just want to push car out of corner?
Thank you for this video!!
Whats about rallysport? i guess you want depending on the driving style and surface a decent amount of body roll. Is a scandinavian flick without a good amount of bodyroll even possible? I guess not. What do you think?
Phil Langer The flick can be done better with smaller bodyroll.
Phil Langer Think about extremes... if the car has too much body roll, when you try to flick it, it will have a great amplitude of rotation, wich also means it's harder to "pull" it back arround, that's if the car doesn't flip ahah
H Scorpio thanks for your reply. i think you are right. my question is if the sligthly greater bodyroll supports the flick or not. Mortalomena said smaller is better, but i am still not sure!
No problem :)
It is possible to flick, you can see rally drives do it, nowadays we don't see wrc drives do it too much, because recent cars have more grip than the older ones, so it's faster to go as straight as possible (said by Colin McRae)
Phil Langer Glad to see a rally fan! scandi flick can also be aided by left foot breaking hard in (diving) and providing high throttle input (where rwd > fwd, most wrc are ~70/30 split) and thus removing grip from rear tires by spinning them. This moves the CG to the front of the car and allows the rest of the car to rotate around that point. Leading to some saying they steer with their feet more than their hands.
The flick is dependent on front to rear CG more than top to bottom (which is what this video discusses). Anti Dive (preventing rear to front CG movement) would have a bigger (negative) impact on Scandinavian Flick than Anti Roll.
AR set-ups can help reduce the chance of roll-overs in high grip, high speed, sharp turn scenarios, by counter balancing a higher CG. Since Rally cars need higher clearance they will have a higher CG than typical cars; so AR is even more important.
How to calculate the center of gravity point for any car (if possible please make a video for it)
What are your thoughts on Megan Roll center adjusters? Seems relatively cheap to purchase. Would the benefits be noticeable installing these. I currently have megan Racing sway bars and SPC adjustable rear arms and front adjustable ball joints with Figs LCA bushings lowered on BC coilovers with swift springs on my 07 IS350 Rolling on Vossen CV2 20in wheels.
Great video, thanks.
Hypothetically, can the CG ever be below the roll center (by artificially adding a ton of weight down low)? What would happen then?
Roll center can be raised or lowered with geometric changes, no weight needed. Dynamically it probably would ride like a go-kart, very responsive aka twitchy
How to locate roll centre and instantaneous centre of vehicle with leaf spring suspension?
how do we ensure that torque produced on rear and front sprung mass about roll centre are same
Can you tell something about non-rolling overturning moment?
#EngineeringExplained Can u talk about rake effect on car ? Advantages and disadvantages. Sorry for bad EN.
What mods can we do in practice that improves handling based on the principles he explained?
Why do formula one cars go for low roll centres?
And, setting the roll centre higher will increase the jacking forces. What's the ideal position for roll centre taking into account everything.
i know im 5 years late but is it possible to have a roll axis above the cg? it seems possible just thinking for a second but im not googling the right things or something because i cant find info, thanks.
So, in theory, if the roll center was HIGHER than the center of gravity, the vehicle would lean into corners, right? Why isn't that done? Seems like it would greatly increase passenger comfort. I suppose it would have awful effects on camber...
It may be more comfortable but it's harder to control. You actually want a low roll center to have more force on the outer wheels in a curve.
sick'!~ UA-cam recognizes underscores as _italics feature_