Jump to content


Photo

For rally fans: Weakness of 205T16 also known with Stratos?


  • Please log in to reply
47 replies to this topic

#1 Henri Greuter

Henri Greuter
  • Member

  • 4,802 posts
  • Joined: June 02

Posted 09 May 2012 - 14:37

This is for the rally fans among us.

In the Gp B heydays, the Peugeot 205T16 was the best of the bunch It had however one eery habit. If airborne, the transversal location of the angine enhanced a tendency of the car to raise or drop its nose (and vice versa for the tail) that was attributed to rotating forces around the crankshaft location, related with the ratotion of the crankshaft within the block.
Ari vatanen's horror crash in Argentina '85 is said to be related with this phenomen the car posessed.

I wondered, just about the only mid or rear engined rally car with tranverse engine I can think of is the fabled Lancia Stratos. But I never read anything about the Stratos having a similar habit of behaviour when airborne.
Now the Lancia had the engine pretty much above the rear axle thus not in the center of the car compared with the Peugeot, which may explain it.
But has anyone with interest for rallying ever heard about the Stratos being tricky once airborne?

Thanks,

Henri

Advertisement

#2 MatsNorway

MatsNorway
  • Member

  • 2,051 posts
  • Joined: December 09

Posted 09 May 2012 - 16:12

Did they really drive and jump the Stratos as hard as the Peugeot?

And it sounds like a myth.

It probably is a mix of Aero and weight distribution.

IF real it would be sensitive to throttle position and you would be able to "balance" the car with the throttle. And i have never heard about that in cars.


#3 BRG

BRG
  • Member

  • 11,509 posts
  • Joined: September 99

Posted 09 May 2012 - 18:50

Did they really drive and jump the Stratos as hard as the Peugeot?

Drive it as hard? YES! Jumps? Well it was used in the full range of WRC events of the time, although otherwise mainly on tarmac rallies, so it would have had to cope with any jumps that it encountered. I do not recall any question about its stance over jumps, but that may be a function of its higher overall weight, and the fact that it had a V6 that was probably heavier than the T16's little I4. This may have counteracted any rotational forces. I also think any problem with the T16 may have been about aero and weight distribution as much as the engine position.

As for your comment about balancing the car over jumps with the throttle position, that is a common practice - ask any Finn.

#4 GreenMachine

GreenMachine
  • Member

  • 763 posts
  • Joined: March 04

Posted 09 May 2012 - 23:24

... about balancing the car over jumps with the throttle position, that is a common practice - ask any Finn.


While airborne?

On launch, yes (as I understand it). But as I read the question, it was about adjusting the attitude of the car while in the air by manipulating the throttle.

#5 munks

munks
  • Member

  • 344 posts
  • Joined: January 03

Posted 10 May 2012 - 01:06

I think the effective rotational inertia of the engine might be on the insignificant side, but spinning up the driven wheels (or slowing them down with brakes) will most certainly adjust the pitch attitude of the car. (Think about it ... on solid ground your car squats or dives with the same inputs ... what would happen if the ground suddenly wasn't there?)

Edited by munks, 10 May 2012 - 01:06.


#6 Greg Locock

Greg Locock
  • Member

  • 4,499 posts
  • Joined: March 03

Posted 10 May 2012 - 10:50

I think the effective rotational inertia of the engine might be on the insignificant side, but spinning up the driven wheels (or slowing them down with brakes) will most certainly adjust the pitch attitude of the car. (Think about it ... on solid ground your car squats or dives with the same inputs ... what would happen if the ground suddenly wasn't there?)


Disagree. Put your mighty V8 into neutral. Blip the throttle. discuss the result.

For those of you without a proper V8 on the driveway, the car perceptibly rolls.

#7 saudoso

saudoso
  • Member

  • 4,601 posts
  • Joined: March 04

Posted 10 May 2012 - 11:01

From the theoretical point of view the smaller the distance between CG and crank axle, bigger the torsion effect since the moments of inertial drop.

As per Greg's example above, longitudinal front engines tend to have the crank really close to the CG. And you don't even nedd big V8s, the old chevy 2.4 4 bangers and 4.1 6 bangers we had around here twisted just fine.

#8 Greg Locock

Greg Locock
  • Member

  • 4,499 posts
  • Joined: March 03

Posted 10 May 2012 - 11:03

From the theoretical point of view the smaller the distance between CG and crank axle, bigger the torsion effect since the moments of inertial drop.

As per Greg's example above, longitudinal front engines tend to have the crank really close to the CG. And you don't even nedd big V8s, the old chevy 2.4 4 bangers and 4.1 6 bangers we had around here twisted just fine.

F--k me dead is this physics 101 week? the point of application of a torque to a solid body has no effect on the result.

#9 carlt

carlt
  • Member

  • 1,045 posts
  • Joined: June 09

Posted 10 May 2012 - 14:27

F--k me dead is this physics 101 week? the point of application of a torque to a solid body has no effect on the result.

even when gravity is factored ?

#10 rory57

rory57
  • Member

  • 89 posts
  • Joined: November 10

Posted 10 May 2012 - 17:07

Didn't the Ferrari engine have a gear drive to the gearbox? Did the engine perhaps run backwards relative to rear wheels ( in forward gears)? If so the reaction torques due to rotating parts accelerating during a jump would cancel somewhat. I bet the Flywheel of that Stratos engine was light compared to those of the big V 8 s referred to above.

#11 PhilG

PhilG
  • Member

  • 474 posts
  • Joined: September 06

Posted 10 May 2012 - 17:24

The effect of shutting the throttle whilst airborne is always for the front to drop , as the wheels etc decellerate, its how you jump an MX bike, throttle off in the air makes the bike come down front first, keeping it pinned keeps the front high, pulling in the clutch and stopping the rear wheel drops the front a lot.. same applies to WRC cars , keeping it pinned keeps the front high , getting out of the throttle makes it drop.

Edited by PhilG, 10 May 2012 - 17:24.


#12 munks

munks
  • Member

  • 344 posts
  • Joined: January 03

Posted 10 May 2012 - 17:37

Disagree. Put your mighty V8 into neutral. Blip the throttle. discuss the result.

For those of you without a proper V8 on the driveway, the car perceptibly rolls.


Good point and counter-example. I guess I was thinking that when the torque is geared up to the driven wheels it's a lot more significant. In your example, the moment of inertia in roll is small which helps exaggerate the reaction. If you were in gear, then the differential would end up canceling most of that reaction in roll, assuming that the engine-body-differential is one fairly rigid unit (which is a big assumption). The torque would then be multiplied by the diff ratio as it changed axes (I think; damn am I failing physics 101 here?), but on the other hand would be working against a bigger moment of inertia in pitch.

#13 MatsNorway

MatsNorway
  • Member

  • 2,051 posts
  • Joined: December 09

Posted 10 May 2012 - 18:36

wheelweight is the big factor here. WRC cars comes inn at 1230kg dry?

add 140kg +- of driver/Co +fuel and where at about 1400kg..

What is the weight of a WRC car wheel?

What is the weight of a motocross wheel and bike with driver?

The ratios might tell us something.

im leaning towards that if it does have an effect its minor and not likely to be the reason to the myth..

Posted Image

#14 munks

munks
  • Member

  • 344 posts
  • Joined: January 03

Posted 10 May 2012 - 19:53

wheelweight is the big factor here. WRC cars comes inn at 1230kg dry?

add 140kg +- of driver/Co +fuel and where at about 1400kg..

What is the weight of a WRC car wheel?

What is the weight of a motocross wheel and bike with driver?

The ratios might tell us something.

im leaning towards that if it does have an effect its minor and not likely to be the reason to the myth..


Greg's right, the weight of the wheels is irrelevant. It's the engine torque (possibly geared) vs. the moment of inertia for the vehicle that matters here.

But I think you have a good point about the aerodynamics - a big effective rear wing or spoiler is there for a reason, and it doesn't stop working just because the wheels are off the ground. (Unlike underbody aerodynamics, which may completely change when the wheels are off the ground: just ask Mercedes or Porsche.)

#15 GSpeedR

GSpeedR
  • Member

  • 35 posts
  • Joined: March 12

Posted 10 May 2012 - 21:27

Greg's right, the weight of the wheels is irrelevant. It's the engine torque (possibly geared) vs. the moment of inertia for the vehicle that matters here.


Do you think the component inertias are irrelevant if the driver applies the brakes mid-air?


#16 saudoso

saudoso
  • Member

  • 4,601 posts
  • Joined: March 04

Posted 10 May 2012 - 22:38

F--k me dead is this physics 101 week? the point of application of a torque to a solid body has no effect on the result.



S--t what was I thinking...

#17 munks

munks
  • Member

  • 344 posts
  • Joined: January 03

Posted 11 May 2012 - 02:29

Do you think the component inertias are irrelevant if the driver applies the brakes mid-air?


Initially, yes. But the wheel inertias change how long it will take to lock up the wheels, at which point there will be no more angular momentum exchanged. Similarly, accelerating will eventually cause the engine to hit the rev limiter, time depending on the inertias involved (oh, and the engine torque will be changing as the engine speeds up). Perhaps you would have preferred "mostly irrelevant".

#18 Kelpiecross

Kelpiecross
  • Member

  • 859 posts
  • Joined: October 10

Posted 11 May 2012 - 03:51

[quote name='munks' date='May 11 2012, 06:53' post='5705180']
Greg's right, the weight of the wheels is irrelevant. It's the engine torque (possibly geared) vs. the moment of inertia for the vehicle that matters here.

Surely not? If a jumping motorbike has a rear wheel with a very high moment of inertia (like - it's got lead weights inside the tyre attached to the rim) and the rider attempts to accelerate the rear wheel while airborne - won't the bike tend to rotate about the wheel instead of vice versa?


#19 PhilG

PhilG
  • Member

  • 474 posts
  • Joined: September 06

Posted 11 May 2012 - 07:22

Surely not? If a jumping motorbike has a rear wheel with a very high moment of inertia (like - it's got lead weights inside the tyre attached to the rim) and the rider attempts to accelerate the rear wheel while airborne - won't the bike tend to rotate about the wheel instead of vice versa?



It would and it does, hence why we tend to hear 'panic rev' when riders come up short on a jump, because it turns the bike round the wheel.

The same principle would work on a boxer twin, so its not about the crank.

Advertisement

#20 munks

munks
  • Member

  • 344 posts
  • Joined: January 03

Posted 11 May 2012 - 15:07

My mistake, you guys are right. Sometimes I forget that a moment of inertia isn't always measured with respect to the CG. By changing the vehicle/wheel ratios and considering their constraints relative to each other, you have moved the point about which the vehicle is rotating, and hence the relevant moment of inertia.

/sheepishly returns to the drawing board

#21 gruntguru

gruntguru
  • Member

  • 5,229 posts
  • Joined: January 09

Posted 12 May 2012 - 07:23

Interesting topic, I should have checked earlier. Couple of comments.
- The effect of a throttle blip will depend a lot on the rotational inertia of the engine. A production V8 with its massive flywheel would have much more inertia than a 4 cyl race car engine with lightweight everything.
- The rotational inertia of the drive wheels has got to be significant even given their speed is much lower than the engine.
- The transverse engine layout would offer greater control of mid-air pitch provided the engine rotates in the same direction as the wheels - less control if the rotation is opposite to the wheels.
- The longitudinal engine layout would offer some control of mid-air roll (accelerate the engine to roll the chassis in the opposite direction and vice versa)
- The longitudinal engine layout would offer some control of mid-air pitch (high engine speed reduces any pitch present (usually forward) and convert it to yaw via gyroscopic torque)
- The longitudinal engine layout would offer some control of mid-air yaw via the phenomenon described immediately above.

#22 MatsNorway

MatsNorway
  • Member

  • 2,051 posts
  • Joined: December 09

Posted 13 May 2012 - 11:07

I still want bike weight and wheel weight and the same for the car...

And i know someone here knows a thing or two about it. spitt it out.

#23 PhilG

PhilG
  • Member

  • 474 posts
  • Joined: September 06

Posted 13 May 2012 - 11:28

I still want bike weight and wheel weight and the same for the car...

And i know someone here knows a thing or two about it. spitt it out.



Well MX bikes are 105kg or there abouts, rear wheel i think is around 7kg with a tyre..

WRC is 1260 min wt (i think) and the wheels with mousse were quite heavy, ill see if i can come up with a figure.

What i do know is that the effect in the car is far more than i thought it would be, while testing a new crank back in the day , we did a load of full throttle jumps at Millbrook , over a blind crest, which were taken with the aid of a radio link to the other side (it was an open circuit).. the radio crackled as we hit the peak and the driver though it was because we werent clear, and he got off the throttle and the thing nose dived... even sitting as low as i was, all i could see out of the screen was tarmac... and as we carried on the driver , David Higgins, and i had the discussion about it , as he rides off road like me , and he said its just the same, but you dont go as far as dipping the clutch and hitting the brakes, cos the strain on the transmission would would just kill it.

Certainly a fun day, and interesting to hear how much reads over from bikes to cars..

#24 Greg Locock

Greg Locock
  • Member

  • 4,499 posts
  • Joined: March 03

Posted 13 May 2012 - 22:48

Interesting topic, I should have checked earlier. Couple of comments.
- The effect of a throttle blip will depend a lot on the rotational inertia of the engine. A production V8 with its massive flywheel would have much more inertia than a 4 cyl race car engine with lightweight everything.


If the throttle blip resuts in the same bmep vs time profile does the rotational inertia of the engine flywheel or driveline matter, if the engine's bore and stroke and number of cylinders is the same?

Edited by Greg Locock, 13 May 2012 - 22:51.


#25 gruntguru

gruntguru
  • Member

  • 5,229 posts
  • Joined: January 09

Posted 13 May 2012 - 23:35

Agree. The "Angular Impulse" would be proportional to area under BMEP vs time curve. A heavier flywheel would increase the time.

#26 NeilR

NeilR
  • Member

  • 455 posts
  • Joined: October 09

Posted 14 May 2012 - 01:32

perhaps use a fig of 25kg for the WRC wheel/tyre: 7kg wheel + 7kg tyre + brakes, hubs.

#27 MatsNorway

MatsNorway
  • Member

  • 2,051 posts
  • Joined: December 09

Posted 15 May 2012 - 06:40

perhaps use a fig of 25kg for the WRC wheel/tyre: 7kg wheel + 7kg tyre + brakes, hubs.


Good point. Brakes/diffs/shafts adds up.

#28 thiscocks

thiscocks
  • Member

  • 921 posts
  • Joined: October 07

Posted 15 May 2012 - 11:59

I remember on a wrc feature the drivers talking about excelerating to lift the nose up while in the air in about 2003, so it obviously has an effect. Seem to remember it being talked about after Richard Burns nose dived his 206 in finland I think...

#29 BRG

BRG
  • Member

  • 11,509 posts
  • Joined: September 99

Posted 15 May 2012 - 19:53

I remember on a wrc feature the drivers talking about excelerating to lift the nose up while in the air in about 2003, so it obviously has an effect. Seem to remember it being talked about after Richard Burns nose dived his 206 in finland I think...

I am rather doubtful about this. WRCs are 4WD, so both front and rear wheels would accelerate equally and surely cancel each other out (or the car would go up into the air, which seems unlikely...). Far more likely that the drivers concerned meant putting on the power just before takeoff to raise the nose.

#30 saudoso

saudoso
  • Member

  • 4,601 posts
  • Joined: March 04

Posted 15 May 2012 - 20:27

I am rather doubtful about this. WRCs are 4WD, so both front and rear wheels would accelerate equally and surely cancel each other out (or the car would go up into the air, which seems unlikely...). Far more likely that the drivers concerned meant putting on the power just before takeoff to raise the nose.



So you've falllen into the same trap I did. As it was harshly reminded to me, torque is application point independant.

I ran a bunch of experiments in the darkness of my mind, and this one convinced me:

If you try to release a stuck wheel nut with a pneumatic gun, the whell will start to turn. Let's say the nut was on the far right, the wheel will start turning left. If this idea about torque and leverage was true, once the nut hit the middle, the whell would sart to loose speend and then reverse. Would work like a pendulum. Wrong.

The effect of the two axles sum up.

#31 Kelpiecross

Kelpiecross
  • Member

  • 859 posts
  • Joined: October 10

Posted 16 May 2012 - 03:31

Good point. Brakes/diffs/shafts adds up.


I don't think the actual weights come into this debate too much - it's the distribution of the weight resulting in the moment of inertia of the rotating components. A driveshaft may be heavy but would have a low MOI.

I also think the gear that is used during the jump is important - the higher the gear - the higher the apparent MOI. Most jumps would be in the highest gear anyhow.

But I may be wrong as I only use the much-maligned MI method of analysis (MI is "Monkey Intuition").

#32 gruntguru

gruntguru
  • Member

  • 5,229 posts
  • Joined: January 09

Posted 16 May 2012 - 10:03

I also think the gear that is used during the jump is important - the higher the gear - the higher the apparent MOI. Most jumps would be in the highest gear anyhow.

Hmm yes, the higher gear allows the wheels to be accelerated to a higher speed, therefore higher angular momentum, therefore higher angular impulse.

#33 Wolf

Wolf
  • Member

  • 7,881 posts
  • Joined: June 00

Posted 16 May 2012 - 10:43

Are you sure, Grunt? The way I see it, it's the engine torque that counts the most: Torque = MOI x (angular acceleration) for wheel/vehicle, but angular acceleration is obtained from engine torque as angular acceleration = Engine Torque / MOI ; which leaves us with Torque = Engine Torque , meaning the higher torque exerted on the vehicle should be in lower gears.

#34 saudoso

saudoso
  • Member

  • 4,601 posts
  • Joined: March 04

Posted 16 May 2012 - 11:32

Isn't all the drive train free floating as rotation relative to the car body is concerned? The drive train will only contribute countering part of the torque the engine will deliver at it's mountings. The other part of that torque will be related to (almost) accelerating it's gut's to redline in a second.

My guess would be may be 4th, may be 7th gear. All depending on which wouldn't redline immediatelly and would redline right when the flight ends. Like gearing for a long straight.

Edited by saudoso, 16 May 2012 - 11:33.


#35 gruntguru

gruntguru
  • Member

  • 5,229 posts
  • Joined: January 09

Posted 16 May 2012 - 12:02

Are you sure, Grunt? The way I see it, it's the engine torque that counts the most: Torque = MOI x (angular acceleration) for wheel/vehicle, but angular acceleration is obtained from engine torque as angular acceleration = Engine Torque / MOI ; which leaves us with Torque = Engine Torque , meaning the higher torque exerted on the vehicle should be in lower gears.

Perhaps but time (accelerating the drive wheels from min to max engine rpm) is longer in the higher gear, so angular impulse (= torque x time) will be greater. Note - angular impulse also = delta angular momentum = I x delta wheelspeed. Delta wheelspeed is greater for taller gears.

#36 gruntguru

gruntguru
  • Member

  • 5,229 posts
  • Joined: January 09

Posted 16 May 2012 - 12:08

All depending on which wouldn't redline immediatelly and would redline right when the flight ends. Like gearing for a long straight.

To maximise the effect on total pitch, use the tallest gear, nail the throttle as the car launches and hold the revs at redline till the car lands. This will produce the greatest angular velocity (pitching forwards) as early as possible in the flight and maintain that velocity for as long as possible. To maximise pitch rearwards, hit the brakes and stop all wheels as soon as the car leaves the ground.

#37 Kelpiecross

Kelpiecross
  • Member

  • 859 posts
  • Joined: October 10

Posted 16 May 2012 - 13:31

Perhaps but time (accelerating the drive wheels from min to max engine rpm) is longer in the higher gear, so angular impulse (= torque x time) will be greater. Note - angular impulse also = delta angular momentum = I x delta wheelspeed. Delta wheelspeed is greater for taller gears.


Using the time-honoured principles of MI:

Picture an engine floating in space (with MI just about every situation ends up floating in space) driving a massive flywheel via step-up gearing.
If you momentarily increase the power output - what happens? The engine and the flywheel rotate in opposite directions but in proportion to their MOIs. As they are free floating the only thing restraning their rotations are their MOIs - the engine has a certain amount of MOI but, by virtue of the step-up gearing and the heavy flywheel, what the engine is driving might have many times the MOI - it may be almost impossible to accelerate. Thus the engine spins like a top.

Translating to jumping rally cars - while the car is flying it is essentially weightless (except for aerodynamic effects) - it might as well be in space - the more MOI the wheels have and the higher the gearing the more the car will rotate.

#38 PhilG

PhilG
  • Member

  • 474 posts
  • Joined: September 06

Posted 16 May 2012 - 18:43

To maximise the effect on total pitch, use the tallest gear, nail the throttle as the car launches and hold the revs at redline till the car lands. This will produce the greatest angular velocity (pitching forwards) as early as possible in the flight and maintain that velocity for as long as possible. To maximise pitch rearwards, hit the brakes and stop all wheels as soon as the car leaves the ground.


totally totally wrong.

You keep the throttle pinned to get keep the front up, you hit the brakes to get the front to come down.. 2 or 4 wheels, the result is the same.



#39 BRG

BRG
  • Member

  • 11,509 posts
  • Joined: September 99

Posted 16 May 2012 - 19:12

To maximise the effect on total pitch, use the tallest gear, nail the throttle as the car launches and hold the revs at redline till the car lands. This will produce the greatest angular velocity (pitching forwards) as early as possible in the flight and maintain that velocity for as long as possible. To maximise pitch rearwards, hit the brakes and stop all wheels as soon as the car leaves the ground.

Perhaps, in theory.

In practice, option 1 would probably lead to a drivetrain failure of some sort on landing, whilst option 2 would take you straight to the scene of the accident.

Advertisement

#40 gruntguru

gruntguru
  • Member

  • 5,229 posts
  • Joined: January 09

Posted 16 May 2012 - 22:37

totally totally wrong.

You keep the throttle pinned to get keep the front up, you hit the brakes to get the front to come down.. 2 or 4 wheels, the result is the same.

Totally totally correct (you are). A big whoops - I managed to reverse the direction. :blush:

#41 PhilG

PhilG
  • Member

  • 474 posts
  • Joined: September 06

Posted 16 May 2012 - 22:54

Perhaps, in theory.

In practice, option 1 would probably lead to a drivetrain failure of some sort on landing, whilst option 2 would take you straight to the scene of the accident.


Well you would think so , but thats what testing is for , my nosedive experience was part of a days testing of a new crankshaft, bearing in mind the drivetrain has already passed this .

100 full throttle jumps on tarmac .. just to see if the crank/flywheel was up to the job. Its what goes on behind the scenes that means these thing dont happen.

I dont think you'd ever want to hit the brakes in the air in a car, but on a bike it's used to get the bike to the right attitude, or simply to avoid a crash when you get it wrong.


#42 PhilG

PhilG
  • Member

  • 474 posts
  • Joined: September 06

Posted 16 May 2012 - 22:55

Totally totally correct (you are). A big whoops - I managed to reverse the direction. :blush:


:lol:
i re-read everything before i post , especially on here... nobody misses a thing lol :wave:

Edited by PhilG, 16 May 2012 - 22:55.


#43 MatsNorway

MatsNorway
  • Member

  • 2,051 posts
  • Joined: December 09

Posted 20 May 2012 - 09:14

In practice, option 1 would probably lead to a drivetrain failure of some sort on landing

RC cars got slipper clutches to save the drivetrain.
http://www.youtube.c...etailpage#t=23s

Posted Image

Considering Rally cars usually has full throttle on the jumps i would think they have it too.

Edited by MatsNorway, 20 May 2012 - 09:31.


#44 carlt

carlt
  • Member

  • 1,045 posts
  • Joined: June 09

Posted 20 May 2012 - 17:19

But I may be wrong as I only use the much-maligned MI method of analysis (MI is "Monkey Intuition").


"hey hey we're the monkeys and we love monkeyin' around"

#45 MatsNorway

MatsNorway
  • Member

  • 2,051 posts
  • Joined: December 09

Posted 21 May 2012 - 14:38

MX bike.

bike and dude 180kg / wheel weight 7kg = 25,7

WRC car

Car and dudes 1380kg / ((10kg wheel + 3kg disc) x 4) = 21.5

The difference is surpricingly low. About 20% more wheel weight for the bike. yes the bike got bigger diameter wheels but its clear that the car would be fairly sensitive to this.



#46 PhilG

PhilG
  • Member

  • 474 posts
  • Joined: September 06

Posted 21 May 2012 - 18:51

RC cars got slipper clutches to save the drivetrain.
http://www.youtube.c...etailpage#t=23s

Posted Image

Considering Rally cars usually has full throttle on the jumps i would think they have it too.


Slipper clutches are used in road racing extensively , and supermoto too , but they only slip on decelleration to stop the rear wheel hopping , under braking , you cant get one that slips like an RC car cos the loads are too high.

I prefer not to use one, the extra weight in the clutch pack is noticeable , and i prefer to control it myself with the lever, as ours are purely mechanical, the MotoGP boys have the beauty of electronics, but it just wont find its way onto cars


#47 gruntguru

gruntguru
  • Member

  • 5,229 posts
  • Joined: January 09

Posted 22 May 2012 - 12:11

MX bike.

bike and dude 180kg / wheel weight 7kg = 25,7

WRC car

Car and dudes 1380kg / ((10kg wheel + 3kg disc) x 4) = 21.5

The difference is surpricingly low. About 20% more wheel weight for the bike. yes the bike got bigger diameter wheels but its clear that the car would be fairly sensitive to this.

and don't forget, on the rally car all wheels contribute - on the bike, only half the wheels contribute.

#48 MatsNorway

MatsNorway
  • Member

  • 2,051 posts
  • Joined: December 09

Posted 22 May 2012 - 12:45

and don't forget, on the rally car all wheels contribute - on the bike, only half the wheels contribute.

i did not forget. he claimed 7 kg for rear wheel. the bigger dia would aid in rotating the bike.


OZ racing Leggenda rims:

http://www.northamer...ls-fitment.html
8.39 kilograms

Rec. Tire Size:205/45-17

what would a tire come in at?

Edited by MatsNorway, 22 May 2012 - 12:48.