Landings

[Rani]

I've noticed that WRC cars seem to be landing (after big jumps, of course) on their back wheels a lot more than they use to in prior seasons. Is this because of setup changes or because engineers are taking the CG of the cars more to the rear?
If anyone could explain I'd love to hear it.

[Steve Boyd]

I very much doubt it's the CG moving to the rear - the old Quattro's with the engine in front of the front axle used to land tail first whereas Porsche 911's had a habit of kicking up the tail if you didn't attack the jump correctly. I think it's more to with set-up and driving technique. The less time in the air the quicker - all the time the wheels are off the ground you're decellerating. It also helps to preserve radiators, intercoolers, sump & aerodynamics if you land flat or slightly tail first. You're also less likely to spear off the track with a tail first landing as the drag of the rear wheels landing first will tend to keep the car straight. A heavy front landing can cause the car to land unpredictably sideways which isn't good if you don't expect it.

[Buzz Lightyear]

big rear boot spoilers.

[SubaruNorway]

and the bonnet scoop on the impreza

[Bazza2541]

I think the direction the crank rotates in may have something to do with it too.
I seem to remember that Peugeot reversed the rotation of the crankshafts on their Group B 205's to reduce the nose down effects of landings. Anyone else remember this? Or was I drunk?

[Daniel]

Not that I remember. That was the reason for the evo 2 aero package

[Bazza2541]

The way I remember it being explained to me was along this line..............
The crank in an engine wants to stay stationery and rotate the engine around it, so if its a transverse engine rotating clockwise it lifts the nose, anti-clockwise drops the nose.
But then again its almost twenty years ago so I may be remembering it wrong.

Did Mitsubishi not reverse the engine in the EVO 3/4 for the same reason?

[Zico]

The principle you describe is used by motocross riders to help with their bike positioning in mid-air and landing, so there may well be some truth in it. I may be wrong but I would have thought the hugely increased overall mass/crank torque ratio a rallycar has over a motocrosser means it should have a minimal effect.

I always thought Mitsu (as well as Ford with the Escort Cosworth) adopted a transverse engine mounting solely for weight distribution purposes.. If thats what you meant?

[J4MIE]

Accelerating/braking whilst the car is airborne can have an effect too I believe, some kind of gyroscopic effect or something?

[shurik]

Accelerating/braking whilst the car is airborne can have an effect too I believe, some kind of gyroscopic effect or something?
exactly, also significant whether you ease the throttle or push it to the metal right before takig off.

[janvanvurpa]

The principle you describe is used by motocross riders to help with their bike positioning in mid-air and landing, so there may well be some truth in it. I may be wrong but I would have thought the hugely increased overall mass/crank torque ratio a rallycar has over a motocrosser means it should have a minimal effect.

I'm ex-moto-crosser.
We did this "gas it hard" thing to raise the nose, tap the rear brake to lower the nose thing, and it really worked.
But all of the bikes I rode were REAR WHEEL DRIVE.
Not been in the air in my 4x4 Cossie, so can't say if it would really help.



I always thought Mitsu (as well as Ford with the Escort Cosworth) adopted a transverse engine mounting solely for weight distribution purposes.. If thats what you meant?

Misterbitchy was making traverse engined Galants and Lancer in FWD form, making the 4wd is an add on to the exsisting FWD gearbox (on the road car which the Homologation is based on) .

The Escort Cossie engine is North/South, same as the Sierra where Ford got the floor from to make the Escort Cos. (Floor shortened to reduce Escort Cos wheelbadse to 100.5" from Sierra nad Sapphire's 102.7"

Re original qusetion of landing on rear wheels first:


Now you know they're looking to make what? with those silly wings everybody tacks on???
Downforce!!!

Well all that is airflow PUSHING THE WING (and the bootlid and the rest of that end of the car) downwards.

So it seems the wings work, they push down.

[Carlo]

Bazza is correct, both the Pug and the Evo 4 onwards had engine rotation changes that enabled them to fly better and land better.

The advent of large rear wings on todays cars ,just as before with the Quattro has also assisted in a tail down attitude on landing.

As decribed by many,changes to the vehicles attitude is often induced by the driver / rider through the use of brakes, throttle, balance and the timing of these applications

[Rani]

big rear boot spoilers.
Wouldn't that make the cars understeer badly?
Or would they counter this with suspension and diff settings?
Anyhow the cars don't seem to push at all.
BTW thanks for the explanations, everyone.

[Daniel]

Bazza is correct, both the Pug and the Evo 4 onwards had engine rotation changes that enabled them to fly better and land better.

The advent of large rear wings on todays cars ,just as before with the Quattro has also assisted in a tail down attitude on landing.

As decribed by many,changes to the vehicles attitude is often induced by the driver / rider through the use of brakes, throttle, balance and the timing of these applications
Do you have any links/evidence to back this up? I've never heard this about the Evo2 T16 and google brings up nothing at all. Possibly an urban rally myth?

[Zico]

Do you have any links/evidence to back this up? I've never heard this about the Evo2 T16 and google brings up nothing at all. Possibly an urban rally myth?

I think it must be.. ??

[Daniel]

There is theory behind it no doubt..... but in practice I don't think it makes as much of a difference as is being made out (in cars). Could be extremely wrong but the main problem with the 205 T16 Evo1 was the weight distribution and this wasn't cured but the symptoms were by the aero kit.

[shurik]

Wouldn't that make the cars understeer badly?
Or would they counter this with suspension and diff settings?
Anyhow the cars don't seem to push at all.
BTW thanks for the explanations, everyone.
It's all about aerodynamics - usually production based race car has spoiler in front and a wing in back and while spoiler creates downforce by cutting the flow under the body, wing creates downforce because of it's shape. BUT, aerodynamic work differently if you compare an object close to the ground and in mid-air. Spoiler wont work on a car that is flying, while rear wing will do. So this may lead to a situation, when some car may land on it's back in common.

[Daniel]

I think it must be.. ??
I've thought about it long and hard and don't think it's true. Think about it. Think about the weight of the brake discs, wheels, tyres, driveshafts and so on which are all turning at high RPM already and already creating forces. I somehow doubt a crankshaft weighing a few kg is going to profound nose down effect that people are suggesting. The 205 had extensive aero work done on it for the Evo 2 and I think this indicates where the problem lay.

[shurik]

Keep in mind that crank rotates about 4 times faster than wheels at final gear :)

[Zico]

I've thought about it long and hard and don't think it's true. Think about it. Think about the weight of the brake discs, wheels, tyres, driveshafts and so on which are all turning at high RPM already and already creating forces. I somehow doubt a crankshaft weighing a few kg is going to profound nose down effect that people are suggesting. The 205 had extensive aero work done on it for the Evo 2 and I think this indicates where the problem lay.

To further confuse the issue.. Re- The Mitsi Evo IV, it is true they rotated it 180 Deg.. http://www.lancer-evo.net/community/viewtopic.php?t=7135

"The engine was still transverse, but mounted 180 degrees opposite to that of the Evolution III which, much of the annoyance of the competition specialists, meant accommodating a larger transfer box - it was bigger, heavier and more expensive to produce."

Annoyed... Bigger, heavier and more expensive... then why did they do it?

While Wiki states..
"The engine and transaxle was rotated 180° to better balance the weight and eliminate torque steer."


Hmmm...

[cut the b.s.]

I've thought about it long and hard and don't think it's true. Think about it. Think about the weight of the brake discs, wheels, tyres, driveshafts and so on which are all turning at high RPM already and already creating forces. I somehow doubt a crankshaft weighing a few kg is going to profound nose down effect that people are suggesting. The 205 had extensive aero work done on it for the Evo 2 and I think this indicates where the problem lay.

Keep thinking Daniel, I think you are wrong this time, I remember reading one of their engineers comments on this, I'll try to find the reference for it over the holidays, the engine rotation was certainly thought to be the culprit, the revs going up or down severly would alter the angle, from memory the planned balance shafts to elimate the problem but I'm not sure if this happened on the E2 or was planned, I'll see what I can find on this

[Daniel]

Keep thinking Daniel, I think you are wrong this time, I remember reading one of their engineers comments on this, I'll try to find the reference for it over the holidays, the engine rotation was certainly thought to be the culprit, the revs going up or down severly would alter the angle, from memory the planned balance shafts to elimate the problem but I'm not sure if this happened on the E2 or was planned, I'll see what I can find on this
As I said. Think about the physics. At the end of the day the crank weighs a few kg's. Think of how much energy is being put through the diffs, wheels, driveshafts and so on. All parts that you can't reverse the rotation of.

The main things that help a car fly are weight distribution and good aerodynamics. Remember Petter's flight (very 205 T16 Evo 1 like!) in Finland after losing the rear wing.

Plus it's all BS because a standard rotation engine rotates anti-clockwise right? Well the engine is mounted with the flywheel facing the left side of the car when viewed from the back so according to your theory gassing it will make the crank want to stay still and the car will want to go clockwise which in a 205 would raise the nose which is what you want.

Dirt bike. Flywheel on the left when viewed from behind
http://www.forty8.de/designcontest/bikes2006/janne_rautavuori.jpg

205 T16
http://www.ultimatecarpage.com/images/large/410-6.jpg (http://www.motorsportforums.com/forums/FCx(this.href);)

As you can see the flywheel is on the left of the car on both the bike and the 205 T16 therefore the gyroscopic effect in both the bike and car is acting in the same way.

I never stop thinking. I do remember something about the Evo having it's engine flipped but tbh I think that was more to do with it's roots as a RHD road car and the fact that the group A and WRC versions are LHD so packaging is easier if you rotate the engine.

[Daniel]

For those not familiar with the dirty great bit Evo2 kit on the 205 here it is :)
http://www.isitaboat.co.uk/rally/peugeot_205_t16/peugeot_205t16e2.jpg (http://www.isitaboat.co.uk/rally/peugeot_205_t16/slideshow/966138743/)

Here's a video to show you just how well the car worked on jumps. Don't be fooled by the bodywork. The 405 T16 is just a rebodied 205 T16.

Go to about 1:30 and you'll see what effect a dirty great big wing has on a car!
http://www.youtube.com/watch?v=Ciagqfd9s04

[Daniel]

Mitsubishi Evo 2 Engine bay with flywheel facing right.
http://www.dragtimes.com/images/11897-1994-Mitsubishi-Lancer-EVO.jpg

Evo 6 with flywheel facing left
http://www.xspeed.com.au/imagess/secret/mitsubishi/5/02evo6eng3.jpg


I guess there is some sort of gyroscopic effect involved but I suspect the main reason for rotating the engine was more in regards to packaging for the steering, brakes and so on as the car was built to be RHD but was rallied in LHD form.

[Livewireshock]

It is not a matter of pure mass. It is about the forces imparted on those masses. Because the crankshaft is directly connected to the pistons, the forces are immense & with the highest energy that can possibly be. Unlike the wheels & everything else behind the engine as energy is lost in the gearbox & drive train.

So you must keep in mind the force applied to the crank from the pistons compared to force applied to the wheels from the drive train.

Daniel, a crankshaft may only weigh a few kilos but the torque it is producing & the centrifugal force would allow it to spin the engine, if the crank was kept still. But because the engine is fixed on it's mounts, when the car is airborne, the whole vehicle now wants to rotate around the crank.

Think about a helicopter when the tail rotor has failed. The torque rotation is extremely dangerous & uncontrollable and in small helicopter, using a crank much smaller than a rally cars. Another example, look at the big massive drag bikes, the rider has to physically lean off to the opposite side of the inline crankshafts rotation, just to keep the vehicle travelling in a straight line & if the wheels left the ground it results in a big accident as the bike is spun off from underneath the rider.

[Daniel]

It is not a matter of pure mass. It is about the forces imparted on those masses. Because the crankshaft is directly connected to the pistons, the forces are immense & with the highest energy that can possibly be. Unlike the wheels & everything else behind the engine as energy is lost in the gearbox & drive train.

So you must keep in mind the force applied to the crank from the pistons compared to force applied to the wheels from the drive train.

Daniel, a crankshaft may only weigh a few kilos but the torque it is producing & the centrifugal force would allow it to spin the engine, if the crank was kept still. But because the engine is fixed on it's mounts, when the car is airborne, the whole vehicle now wants to rotate around the crank.

Think about a helicopter when the tail rotor has failed. The torque rotation is extremely dangerous & uncontrollable and in small helicopter, using a crank much smaller than a rally cars. Another example, look at the big massive drag bikes, the rider has to physically lean off to the opposite side of the inline crankshafts rotation, just to keep the vehicle travelling in a straight line & if the wheels left the ground it results in a big accident as the bike is spun off from underneath the rider.
I wasn't saying it would have little effect ;) I merely said that if it was operating in the opposite direction to the rest of the spinning bits on the car that the disadvantage would be somewhat cancelled out.

Anyway we've established that unless for some strange reason Peugeot decided to put a reverse rotation engine in the Evo1 205 (why would they?) that the statement at least for the 205 is seemingly no more than a myth and the better jumping of the Evo 2 was better explained by the huuuuuge aero kit.

[jonkka]

Could be extremely wrong but the main problem with the 205 T16 Evo1 was the weight distribution and this wasn't cured but the symptoms were by the aero kit.

Crap. If Audi was able to get their front-engined quattro down to almost fifty-fifty weight balance with S1 by mid-1985, do you really think that Peugeot's purpose-built 205T16 would not have been at ideal distribution a little more than year before? I don't have access to literature now but Peugeot's only weight distribution problem was not front-rear but slight left-right imbalance (because engine sat little bit on the one side, due to transfer box).

[Daniel]

Crap. If Audi was able to get their front-engined quattro down to almost fifty-fifty weight balance with S1 by mid-1985, do you really think that Peugeot's purpose-built 205T16 would not have been at ideal distribution a little more than year before? I don't have access to literature now but Peugeot's only weight distribution problem was not front-rear but slight left-right imbalance (because engine sat little bit on the one side, due to transfer box).
Someone else must have been posting as me yesterday. I meant the main problem was the aero :mark:

[Bazza2541]

Mitsubishi Evo 2 Engine bay with flywheel facing right.
http://www.dragtimes.com/images/11897-1994-Mitsubishi-Lancer-EVO.jpg

Evo 6 with flywheel facing left
http://www.xspeed.com.au/imagess/secret/mitsubishi/5/02evo6eng3.jpg


I guess there is some sort of gyroscopic effect involved but I suspect the main reason for rotating the engine was more in regards to packaging for the steering, brakes and so on as the car was built to be RHD but was rallied in LHD form.

Balls!
Mitsubishi were selling the LHD only TEL in the US from 1989, and they also got the reversed engine along with the EVO, so brakes/packaging whatever was not the problem.

Could it possibly be that the great Daniel does not know every little thing about rallying after all?

And FYI the Aero package was the smallest part of the 205 T16 EVO 2 upgrades.

[Daniel]

Could it be that your gherkin attacked my lollipop!

The fact of the matter is that the 205 had it's engine the "right" way around from the start....

[Steve Boyd]

Turning the engine round to alter the way a car flies - never heard so much nonsense in all my life. The only way a transverse engine could cause a car to rotate in mid air would be if it had a very heavy flywheel that was being accellerated & if this caused the car to rotate the wrong way then all you'd have to do would be to decellerate instead and it would rotate the opposite way. If the wheels aren't on the ground & the engine is running at constant rpm the torque output is minimal therefore the torque reaction between engine & body is minimal. Therefore no rotation.

The reason a helicopter spins out of control when the tail rotor fails is because the torque of the engine is working against the aerodynamic drag of the main rotor. It's Newton's third law of motion.

[shurik]

In fact because of the flywheel size, mass and velocity in some ocassions it may have same or even bigger inpact on car than all four wheels put together. I mean gyroscopic effect of course.
I really don't know if gyroscopic effect of an engine flywheel and it's impact on a car itself was studied, but I have a strong feeling that this may be an issue at some point of development , where the count goes for every gramm of unsrung mass or one additional hampster power is a considerable achievement.

Just to give you some info of what ammount of energy we're talking here..
If you remove couple of kilos from flywheel, in average it would be just like you've lightened the body of the car by 70kg at first gear, 35 on second, et cetera.. And all you did, is reduced flywheel's interia..

[Daniel]

How much do the following components on a car weigh?

Wheel x2, driveshaftx2, brake disc x2, hub x2, tyre x2 and 2x mousse? A lot more than a flywheel and the wheels are much bigger than a flywheel also. Then double this as there are of course two axles.

I somehow doubt that gyroscopic effect is investigated in development. The amount of time a car spends on the time in the air is minimal even somewhere like Finland and you can make a car fly better by getting good weight distribution and aerodynamics.

[shurik]

How much do the following components on a car weigh?

Wheel x2, driveshaftx2, brake disc x2, hub x2, tyre x2 and 2x mousse? A lot more than a flywheel and the wheels are much bigger than a flywheel also. Then double this as there are of course two axles.

I somehow doubt that gyroscopic effect is investigated in development. The amount of time a car spends on the time in the air is minimal even somewhere like Finland and you can make a car fly better by getting good weight distribution and aerodynamics.

tyre - around 8kg
composite disk - 4.2kg (dunno the wight of a stock disk, around 6kg I guess)
alloy wheel - 7kg
stock flywheel - around 8kg, 10inch diameter
dunno the weight of hubs and driveshafts, so let's say that the rotating mass of a wheel is around 20 kg. 21inch outside diameter

Agree here with you, Daniel, there's no use to dig into that gyroscope thing, unless you done the rest, you have 3 months in spare, you spent just a half of budget and you're bored to death. :D

[Daniel]

Then times that by 4 as there are 4 of each of these things. Do WRCars use composite/ceramic discs? If not then add even more weight :)

I couldn’t find anything on the internet about the 205 having gyroscopic effect issues on jumps and the overwhelming evidence shows that the engine was rotating in a way that would use this effect to the advantage of the car. Yet funnily enough the thing still nosedived. Also can't find any evidence of this being an issue for the Evo either. Sounds like an urban rally myth :)

As they would say in Mythbusters. Plausable but unlikely.

[Daniel]

It's funny how the people who insisted that the 205 T16 Evo 1 had gyroscopic effect problems seem to have disappeared into the wilderness leaving the OP somewhat confused. Why don't people look for evidence before posting things like that? :confused: I hear the flux capacitor on the Ford Focus WRC causes handling problems on tarmac which caused Marcus to crash in Ireland! Or at least someone told me that and didn't back it up with facts or evidence *snigger*

[Bazza2541]

It's funny how the people who insisted that the 205 T16 Evo 1 had gyroscopic effect problems seem to have disappeared into the wilderness leaving the OP somewhat confused. Why don't people look for evidence before posting things like that? :confused: I hear the flux capacitor on the Ford Focus WRC causes handling problems on tarmac which caused Marcus to crash in Ireland! Or at least someone told me that and didn't back it up with facts or evidence *snigger*

I posted it as a question. You on the other hand seem to think that you have a right to impose your opinions on others regardless.
It turns out that the engine reversal on the EVO's was primarily to do with the dreaded crankwalk issues, but did have an effect on landings. It also turned out that the engine 'reversal' on the T16 was done at a later date to help their rally raid cars with nose down landings over dunes. As to facts and figures, try Ralli-Art for the Mitsubishi things and whereever you like for the T16 stuff.
As the old saying goes there are none so blind as those who will not see.

[Daniel]

I didn't impose anything. I simply stated my opinion. Should I just agree to make it less painful for everyone who has to read this crap?

What you've just said about the 205 T16's goes directly against your theory because the 205 T16 engine is pointing in the "right" direction to have the effect that you speak of. I don't deny that there is an effect because we all know there is. But I simply don't think it's as big as the effect of aerodynamics.

There's no need to use that sort of language. You were the first one to get uppity with the whole "Perhaps the great Daniel doesn't know everything". All I did was use facts as best I could to explain my viewpoint and all you did was get more and more hostile.

Thanks for the pointers. I'm sure Jean-Claude Vaucard will have no problem speaking to me about gyroscopic effect :laugh: :rolleyes: When I asked you to back your argument up I didn't say "Point me to where I can find the answer" because I'm not the one trying to prove that this effect is as big as stated by Carlo and cut the b.s. That's their job and I think I've done more than enough to show that at least in the 205 it doesn't appear to have been the cause of it's nose down attitude over jumps.

[Bazza2541]

I didn't impose anything. I simply stated my opinion. Should I just agree to make it less painful for everyone who has to read this crap?


Yes you should. You post the majority of this 'crap', so please do make it less painful on the rest of us.

[Daniel]

Yes you should. You post the majority of this 'crap', so please do make it less painful on the rest of us.
Whatever..... I hope the OP got the information he/she needed.

[Bazza2541]

Whatever..... I hope the OP got the information he/she needed.


He/She most certainly did not get it from you.

[Zico]

Any fluent French speakers able to find any info on the issue from this nice 6 part documentary on the T16 ? Some great footage here...

Part 1 here.. http://uk.youtube.com/watch?v=oefSCaahWro&feature=related

(See part 4 for the Evo version..)