【龍Sir學堂 Ep16】認識電動車第二課 電動車的操控和舒適性與汽油車不同之處 原因何在？#revchannel

Turn quickly very stable no need to be afraid of corners However Is it most people who have sat in them thinks Hmm, the ride is a little bumpy? A double decker bus full of people if you measure it In fact, it may be 50:50 The roll centre Normally must be below the center of gravity Electric vehicles are often said to be powerful instant torque launch Maximum torque instantly from start We also know that the greater the strength the more important handling is Let's try to investigate How the handling of EV is People who have driven electric cars or even those who haven't driven them You will feel that EV turns very quickly Driving on the mountain road looks very good Or you can look online Some videos about moose testing Seeing the performance of electric vehicles is very good Why? Simple Low center of gravity for electric vehicles In the age of internal combustion engine cars To lower the center of gravity is no easy feat You may need to spend a lot of money For car manufacturers they may have to lay the engine on its side and lower the frame and tilt the seats backwards a lot of hassle just to lower the center of gravity a little Then those people buy the car spend a lot of money in aftermarket Changed the suspension Lower the vehicle further spend a lot of money Simply put you will pay a high price just to slightly lower the center of gravity it's so precious But when it comes to electric cars the centre of gravity suddenly dropped to very low It's born low Battery at the bottom Does that mean it won automatically? No disadvantage at all? If you purely focus on low center of gravity as the only parameter then it really wins But the world is not so simple Let's look at the bigger picture of overall performance of EV Turns quickly very stable no need to be afraid of corners but Is it most people who have sat in them thinks Hmm, the ride is a little bumpy? Even for models that are not performance-oriented It seems to be a little bumpy This turned out to be related to the low center of gravity there is a connection that's the bigger picture Let's try to investigate Firstly EV has a large battery at the bottom thus the battery almost accounts for a large portion of the weight of the car therefore EVs are easy to achive 50:50 uniform front to back weight ratio Is it a good thing? Of course it's a good thing because in the past Compared with ICE car, there is an engine in the front Front drive cars have 60% or more weight in the front 30% or so behind Turning is certainly not ideal But although that big battery helps achieve 50:50 front to back ratio The rotational inertia of the battery itself the considerable amount of weight cannot be ignored so it doesn't mean 50:50 is invincible Let me give an extreme example a double decker bus full of people you go to measure it In fact, it may be 50:50 but a double decker bus Is it very agile? Of course not So in that case If you take an EV compare it with front-heavy vehicles turn them together The performance of the EV definitely is more advantageous However if i have a well designed car Front engine rear wheel drive, with engine pushed far back or even mid-engine Such cars when compared to EV The handling of EV may not be as agile as those ICE cars that's the first point The second point is back to centre of gravity A low centre of gravity it's always beneficial But to be as low as an electric car there will be a problem That's, the characteristic of rolling totally different from ICE car We know when the car is turning there will be body roll Why? Because of centrifugal force It acts on the centre of gravity Acting on the centre of gravity is only half the story the other half is after all, where is the rolling centre? This is a comparatively more complicated concept What is the roll centre? In fact, it comes from the rocker arms of the suspension when you add up their geometry there will be an intersection point That point is when your car just starting to have body roll the car uses that point to be the centre of the rolling movement Note that the point changes after the car rolls We are talking about, when the car hasn't started rolling but the moment it starts to experience stress we can use this roll centre to calculate the amount of rolling force This is called the roll centre For double wishbone suspension The intersection point obtained by the extension lines of the two rocker arms The intersection point obtained by the extension lines of the two rocker arms Then take that intersection point Draw a straight line towards the center of the tire Then take that line and intersect it with the mid line of the car the intersection of the two lines That is the roll centre You can understand by looking at the picture The roll centre Normally below the center of gravity When the center of gravity is subjected to centrifugal force The body takes the roll center as the axis and thus roll to its side You can imagine If the distance is greater Of course the car wants to roll a little more Everyone may think More body roll, of course not good It's not so simple If there is no roll at all What will happen? For example take a refrigerator There are no wheels under the refrigerator no springs If you push the refrigerator push it to the side When it's about to tip over but right before it tilts that is, one side is close to leaving the ground The entire weight of the refrigerator will be stressed on the other side completely This is called weight transfer or load transfer That's what centrifugal force does If there is a suspension system that allows body roll This load transfer is less dramatic That is, the car rolls a little maybe the inside wheel still has a bit of interaction with the ground The outer wheel may be more stressed The inner wheel may be less stressed but not light enough to be weightless However, if your center of gravity all the way down so low that it is very close to the roll center When centrifugal force acts on it it doesn't roll much But the centrifugal force remains present So you feel like the car isn't rolling But in fact the inner wheels their weight acting on the ground actually becomes very light getting lighter and lighter almost equal to zero At zero the tires will be floating As the weight of the vehicle is unchanged When the weight on the inner wheel is getting lower and lower the weight is completely transferred to the outside wheel So it turns out don't think if there's no roll it's an absolute good thing Without roll, it will lead to when the car is subject to centrifugal force the load transfer becomes more violent To cope with such a drastic load transfer How did the car do so? You can see EV usually use wider tires Many people say The tires of the electric car are wider, of course because they are heavier Weight is one of the reasons The second reason is because of its low center of gravity Low enough to be close to the roll center so there is not much body roll Hence the load transfer is much more drastic When load transfer reaches its limit That is, the outer wheel is already bearing the full weight The inner wheel is equal to zero So we have to design a wheel under extreme condition it could take up the work of the other wheel And because it doesn't roll that lateral force directly acts on the wheel That tire wall We commonly call tire belly will be subjected to a large shear force Shear Stress Therefore, EV usually dare not use very high tire aspect ratio Usually use some thin tires 50 45 40 When you use thin tires plus wider tires How can the ride be comfortable? Therefore EV are often quite bumpy For expensive electric cars Air suspension can be used to solve this problem If not you only have two choices Firstly you carry on the the bumpiness Secondly you need the sacrifice the cornering ability Make the tires thicker then you can be more comfortable But you can't have your cake and eat it Because of your low center of gravity you have already enjoyed the cornering stability but the tires need to do more work There is no way for you to get performance on the one hand but also get comfort on the other hand This can be seen as EV although the center of gravity is low But despite the low centre of gravity still can't escape from some natural physical limitations How should we cope? Don't worry Because the automotive industry is actually a big team Some people make car body Some people make tires Some people make powertrain Those tire manufacturer Already working hard now I believe in the very near future Tires should be able to accommodate the need for comfort and performance If you have driven an electric car Or have ridden in an electric car Towards current electric vehicles in terms of comfort and performance possess your own opinion You can leave a message and share with everyone Let's communicate more Hope you all like this video If you haven't subscribed to our YouTube Remember to subscribe Leave a comment and share more And like us on Facebook and Instagram follow us too

Channel: REV Channel

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Id: CfrVTzfRCnU

Length: 9min 43sec (583 seconds)

Published: Fri Jul 07 2023