For drivers ed, I have to do a poster about basically anything that has to do with driving. Other people are doing posters on stuff like drunk driving. I am going to make a poster about physics. I have a rough draft due Friday. On my poster, I think I will mainly describe the three main car movements that affect its handling: Pitch, yaw, and roll. I am going to take screenshots from LFS, and use them as examples on my poster.

To link this to what we learn in drivers ed, I am also going to say how because of these forces, when you see a sign warning about a sharp curve, you really should slow down to the suggested speed. Especially if you don't know the road at all. But, if you drive on a certain road every single day, then you sometimes know how fast you can safely drive. Like, on some corners where I live, I almost got hit head-on by a soccer moms in her huge SUV who drove halfway into my lane. Now, I slow down on that corner, and drive with my right tires touching the shoulder lane to avoid soccer moms in huge SUVs that don't know anything about the handling of their cars. Especially since the car I drive is my dads Saturn SL2, which only weighs 2,400lbs (1088kg). I don't think a head on collision with a my dads car, and a SUV twice its weight, with both cars travelling at ~30mph would be too fun. It would basically be like hitting a wall @60mph.

Maybe on my poster, I will include something that has to do with the physics of a crash. That is also another important aspect to driving. I honestly do not go more then 5mph over the speed limit at all, because I am afraid of crashing. As well as you can drive, it only takes one "twat" (as they say in the UK :P) to total your car. So, if anyone can help me on what to include on my poster, it would be nice. I knew that I just had to do a project that included LFS somehow!

If you want an EASY A+, then just make a poster on how to drive Stick (manual transmission, if thats what you guys call it). Its not a hard thing to make a poster on, and if you make it pretty, youl get a good grade

great! is it for school? and I found this in my newspaper:

9 out of 10 accidents involving Pedestrians at 64km/h are faital
1 out of 10 accidents involving Pedestrians at 32km/h are fatal.

as much as I hate to say this SLOW DOWN (in real life )

BTW I'm only 14 and not alowed to drive a real car yet

Quote from Sketchyrollin564 :

If you want an EASY A+, then just make a poster on how to drive Stick (manual transmission, if thats what you guys call it). Its not a hard thing to make a poster on, and if you make it pretty, youl get a good grade

I'm in the US too, I just dont display it on the forum to avoid discrimination by those mean limeys.

Bearing in mind that this is a project for a drivers ed course, I don't think it's a good idea to say that you should ever exceed posted speeds, even if they're only advisory. While the yellow suggested speed signs you see on the approach to corners etc are just advisory and are therefore not directly enforceable, you should bear in mind that (a) posted advisory speeds are based on ideal driving conditions and (b) most jurisdictions have a statute which says something like "regardless of the posted speed limit, it is illegal to drive faster than is safe for current conditions"; so, driving faster than the indicated advisory speed could be viewed as driving recklessly. Again, for the purposes of the drivers ed course.

imo just doing something simple

i (when i did this project for drivers ed) just made a little pop up poster thing showing how to properly change lanes and how semis can only drive on the 2 right lanes on highways

dont make it something more complicated than it needs to be

Quote from wheel4hummer :

I don't think a head on collision with a my dads car, and a SUV twice its weight, with both cars travelling at ~30mph would be too fun. It would basically be like hitting a wall @60mph.

Don't worry, it wouldn't be like hitting a wall. It'd just drive over you and crush you
That might be the biggest problem with SUVs, because they are that high and heavy, they and other cars can't use their crumple zones and "crash-softening" structures and crashes with them usually end really bad. SUVs should generally be banned everywhere
If you however drive ~60km/h and have a fairly new car, don't worry about hitting a wall, that might be the best crash that can happen to you

(That didn't really help you with your poster, did it? )

Quote from herki :

Don't worry, it wouldn't be like hitting a wall. It'd just drive over you and crush you
That might be the biggest problem with SUVs, because they are that high and heavy, they and other cars can't use their crumple zones and "crash-softening" structures and crashes with them usually end really bad. SUVs should generally be banned everywhere
If you however drive ~60km/h and have a fairly new car, don't worry about hitting a wall, that might be the best crash that can happen to you

(That didn't really help you with your poster, did it? )

You obviously hadn't read my post in the "Rock Crawler" thread a week or so ago, hehe. Read the text I quoted from another forum .

http://www.lfsforum.net/showthread.php?p=343188#post343188

SUV's should not be banned. That would be like saying ban sports cars because people crash from not being able to handle the extra power and speed of these cars. If you think SUV's are a risk to you sharing a road with you in your car, why not trade that car in for an SUV and be the one who is safe...

[/sorry OT]

Quote from mrodgers :

You obviously hadn't read my post in the "Rock Crawler" thread a week or so ago, hehe. Read the text I quoted from another forum .

http://www.lfsforum.net/showthread.php?p=343188#post343188

SUV's should not be banned. That would be like saying ban sports cars because people crash from not being able to handle the extra power and speed of these cars. If you think SUV's are a risk to you sharing a road with you in your car, why not trade that car in for an SUV and be the one who is safe...

[/sorry OT]

[continuing OT]
It's completely different from saying sports cars should be banned, because with your reasoning it's the drivers' fault for crashing. My point was that due to the height of a SUV all the "hard" parts penetrate the "soft" parts of a normal car during a crash, so that is not the drivers' fault but the fault of the general construction concept of SUVs.
Even if I think SUVs are a danger to people in normal cars, I would never think of trading in a normal car for a pointless gas-guzzling lump of steel. If you want to go offroading, get a proper offroad car, if you want to drive on the street, get a proper street car. SUVs are neither good onroad nor good offroad, thus rendering them pointless. I'm happy that we don't have to many of them over here in Germany because of the petrol prices.
If you still want to defend SUVs, please name one good point about them. (And no, bling doesn't count )
[/OT]

edit: If I haven't made it clear: My point is that SUVs are a danger to other people on the road while sports cars would only endanger the driver him/herself. And btw: Which sane person would think of driving a sports car offroad. It's a bad idea even with normal road cars, so those people deserve to be punished

I think that SUVs are perfectly safe as long as the driver fully understands the limitations of their car. The thing is, alot of people who drive SUVs (I'm talking about "soccer moms" mainly) just dont understand how different an SUV is. I do not think SUVs should be banned, just people who think they can drive the speed limit in the snow just because they have an SUV.

Now I will ask some questions about physics. Here are a few questions I have for certain people on this forum (mainly people like Tristan who have actually raced a real car :nod:

1. When you apply the brakes, your car pitches forward. When it pitches forward, more weight is on the front of your car. Would that cause your front tires to not grip as well, therefore causing understeer?
   
2. When you go into a corner, and you have excess roll because of your setup, then more weight transfers to the side of your car facing the outside of your car. Does too much roll cause understeer?
   
3. When you use the gas, your car pitches backward. Is that what causes you to oversteer when you press the gas too early in a corner?

Thanks to anyone who helps.

Quote from wheel4hummer :

[*]When you use the gas, your car pitches backward. Is that what causes you to oversteer when you press the gas too early in a corner?[/LIST]

From what i've learned from driving on LFS, is that when you are turning the car is sometimes leaning over. When it does this, the inside wheels will have less weight on them than the outside ones. So if you step on the gas when the inside wheels have less traction than the outside ones, they start to spin. More so if you've got a locked differential. Some of this comes from drifting, where they use Weight Transfew techniques to unsettle the traction of the rear wheels. I'm probably wrong about that, but its what I feel it as.

Quote from wheel4hummer :

[...]

1. When you apply the brakes, your car pitches forward. When it pitches forward, more weight is on the front of your car. Would that cause your front tires to not grip as well, therefore causing understeer?

[...]

No, AFAIK more weight = more grip. I think this becomes a negative effect at some time but I know putting more weight over wheels that are braking will give them more grip (a good technique in karting is to push yourself back into the seat when braking)

I'd suggest the basics of oversteer, understeer and how to correct them, as well as why a car rolls (which is much easier to do than Joe Average thinks).

Quote from wheel4hummer :

I think that SUVs are perfectly safe as long as the driver fully understands the limitations of their car. The thing is, alot of people who drive SUVs (I'm talking about "soccer moms" mainly) just dont understand how different an SUV is. I do not think SUVs should be banned, just people who think they can drive the speed limit in the snow just because they have an SUV.

I posted my comment up above half jokingly. The quote I have in the link I posted was strictly a joke posting on another forum. (that link coincidentally points to your thread about rock crawling, doesn't it?) Anyways, herki and I chatted a short bit in pm to not veer off topic too much. About the SUV's driving in snow... I have been driving 4x4 small pickups and small SUV's for the last 12 years. I can tell you that I can drive the speed limit in the snow. Not because I drive a 4wd and think I am invincible, but because I know how do drive in snow and how the vehicle will react.

Quote :

Now I will ask some questions about physics. Here are a few questions I have for certain people on this forum (mainly people like Tristan who have actually raced a real car :nod:

1. When you apply the brakes, your car pitches forward. When it pitches forward, more weight is on the front of your car. Would that cause your front tires to not grip as well, therefore causing understeer?
   
2. When you go into a corner, and you have excess roll because of your setup, then more weight transfers to the side of your car facing the outside of your car. Does too much roll cause understeer?
   
3. When you use the gas, your car pitches backward. Is that what causes you to oversteer when you press the gas too early in a corner?

Thanks to anyone who helps.

Think a moment on what is happening when the weight of the vehicle is transfered around under various situations. When weight is transfered, a force is pushing down harder on the corner that the weight is transfered to. There is more traction (avoid the term grip, I think it looks better using the term traction) between the tire and the road surface. That said, let's look at the three points that you question...

1. Does more weight being transfered to the front of the car cause the front tires to loose traction therefore inducing understeer? No. The weight being transfered forward under braking takes that weight off of the rear wheels causing more force on the front and less on the rear. This would induce oversteer rather than understeer. The rear tires now have less force acting on the road surface, therefore having less traction.

2. I have to think about this one.....

3. Does a car oversteer in a turn when the weight is transfered to the rear under throttle? Again, the weight transfering to the rear of the car will create more traction on the rear tires. What will induce oversteer is the difference in how the differentials apply power to the left and right wheels. When a car is turning, the outside wheel needs to travel a greater distance than the inside wheel. The rear differential's job (in RWD cars) is to apply the power to the correct wheel. With typical stock road cars, the differential will be an open diff. This will apply the power to the inside wheel. It allows the outside wheel to travel at the speed it needs while "pushing" the vehicle by the inside wheel. If heavy throttle is applied, the inside wheel recieving the power will want to spin. But the outside tire is the one with all the weight transfer, thus more traction. So, it will hold the vehicle in the direction of travel while the inside tries to spin. With locking differentials, there is more control over which wheel gets power delivered to it in a turn. More power will be delivered to the outside wheel up to a 50/50 split between the two with a fully locked diff. When they are locked together recieving even power, this is where oversteer happens. When you apply too much throttle, the wheels want to spin, loosing cornering traction and because the wheels are locked together recieving the same power, both wheels will spin rather than the inside wheel while the outside keeps a stable traction to corner.

Of course, the way the suspension is set up on the car has a lot to do with it. The suspension setup is basically nothing but controlling weight transfer. But I'm sure you are not talking racing, but simple on road driving here for your project.

Did that all make any sense? I have it in my head what I want to say, but I'm having trouble putting it down in words. Especially in this tiny reply window at home where I can't easily look at what I typed while being able to type more.

If I understand the project you are doing here, I think you can use screenshots in LFS for support very well. When talking about weight transfer and using LFS screenshots for support, be sure to use Bob's roadsets so the weight transfer is very evident in the shot. Also, you can hit the F key to show the forces. Showing the red, green, and blue forces arrows would be a great way of graphically supporting what you explain in your project. Also perhaps there is something in F1Perf or the replay analyser that you could use.

Good luck with it.

2. That depends on the relative roll stiffness (relative to the mass supported by the springs) at the front vs at the rear. If it's stiffer at the rear, then it will lead to oversteer. All road cars are setup to be stiffer at the front, so lateral acceleration (i.e. cornering) causes unbalanced weight transfer, thus roll, and this example, increased understeer. Note that if the car was oversteering for some other reason, it would only reduce oversteer instead of creating understeer, but the effect always alters handling in the same 'direction'.

Quote from wheel4hummer :

I think that SUVs are perfectly safe as long as the driver fully understands the limitations of their car. The thing is, alot of people who drive SUVs (I'm talking about "soccer moms" mainly) just dont understand how different an SUV is. I do not think SUVs should be banned, just people who think they can drive the speed limit in the snow just because they have an SUV.

Now I will ask some questions about physics. Here are a few questions I have for certain people on this forum (mainly people like Tristan who have actually raced a real car :nod:

1. When you apply the brakes, your car pitches forward. When it pitches forward, more weight is on the front of your car. Would that cause your front tires to not grip as well, therefore causing understeer?
   
2. When you go into a corner, and you have excess roll because of your setup, then more weight transfers to the side of your car facing the outside of your car. Does too much roll cause understeer?
   
3. When you use the gas, your car pitches backward. Is that what causes you to oversteer when you press the gas too early in a corner?

Thanks to anyone who helps.

1. Nope, like sombody said, more weight = more grip, to a certain extent. What causes the understeer, is hitting the brakes too hard, or too quick, thus LOCKING the wheels, creating understeer.

2. Too much roll doesnt really cause understeer (depending on car), but the stiffer suspension is just quicker reaction. Stiffer suspension in the rear, and less body roll in the rear (especialy on RWD cars), is what causes oversteer. Oversteer is when the rear wheels loose grip before the front wheels. Understeer is when the front wheels loose grip before the rears. What happens when a wheel is spinning? Your not gripping. I hope this makes sence.

3. What causes the overster is just too much power to the rear wheels, at too quick of a time. The trick with RWDs, for grip, is to be smooth. Dont SLAM on the gas, and dont just throw the steering wheel in one direction as quick as you can. This doesnt mean you have to be slow, but you gotta be smooth with it. Kinda like trying to draw a good circle with a pencil. you dont have to go super slow, you just gotta be smooth, and not make sudden movements.


Anyways, i hope this helped some, and made sence. Im not the best at explaining things.

Quote from Sketchyrollin564 :

2. Too much roll doesnt really cause understeer (depending on car), but the stiffer suspension is just quicker reaction. Stiffer suspension in the rear, and less body roll in the rear

Stiffer springs really dont do much in terms of body roll. Anti-roll-bars are what reduce body roll.

Quote from Sketchyrollin564 :

Oversteer is when the rear wheels loose grip before the front wheels. Understeer is when the front wheels loose grip before the rears.

It is not really which wheels lose grip before the other ones. If my rear wheels lose grip before my front wheels, I still will understeer if the front wheels lose grip.

There is no actual measure of grip really (what is grip anyway?). Although there is an amount of friction at each tire. The more friction a tire makes, the better the grip. But the friction doesn't change (as long as the tires temperature stays the same, no wear, etc). There is slip angle though. Lateral Gs are what cause you to understeer anyway.

Quote from Sketchyrollin564 :

3. What causes the overster is just too much power to the rear wheels, at too quick of a time.

No, that is not what causes oversteer. What about FWD cars? They oversteer too.

I'm gonna post some replays later maybe. The UF1 is a good car to start studying physics with, because it has such a simple suspension!

Quote from wheel4hummer :

Stiffer springs really dont do much in terms of body roll. Anti-roll-bars are what reduce body roll.

I can't completely agree on this one ... Stiffer springs do have quite an effect on body roll, anti-roll bars are the ones that are helping to adjust the body roll and car dynamics. Just try out which has less body roll in LFS: a car with soft springs hard stiff ARBs or the other way round