Position of a caliper

Here are our CFD links and discussions about aerodynamics, suspension, driver safety and tyres. Please stick to F1 on this forum.
User avatar
NickT
2
Joined: 24 Sep 2003, 12:47
Location: Edinburgh, UK

Post

Forgive my ingnorance :shock: but I still cant get my head around this :? Surely the position of the caliper is irrellevent when considering the forces being put into the upper and lower outboard suspension joints as the braking moment will be a rotational moment about the wheel centre :?:
NickT

RH1300S
RH1300S
1
Joined: 06 Jun 2005, 15:29

Post

Yes, but the if the caliper is mounted on the upright (in this case it is) - if behind the upright the direction the caliper will be moved in is upwards (and rotating). If you grab a spinning bicycle wheel with your hand, from the back your hand will be pulled up; from the front, downward.

User avatar
Ciro Pabón
106
Joined: 11 May 2005, 00:31

Post

Sorry, I think NickT and DaveKillens are right. No matter where your hand is on the "bike", the force to the car is finally passing through the suspension joints, so no effect for caliper position.

BTW, excuse my ignorance, and a little out of thread:

why are not longitudinal stabilizing bars used to counteract the oversteer under braking?

(besides the difficulty of designing an element that goes trough the entire length of the car). Have they ever been tried or is just another crazy idea that could not work?
Last edited by Ciro Pabón on 18 Apr 2006, 18:52, edited 1 time in total.
Ciro

User avatar
NickT
2
Joined: 24 Sep 2003, 12:47
Location: Edinburgh, UK

Post

Hhhhmmmm...... I can see that as your hand is free to move, but what happens if your hand is fixed to the upright:?: Think about the forces on the upper and lower upright mounts, surely they are the same with a front or rear hand/caliper mounting :?:
NickT

RacingManiac
RacingManiac
9
Joined: 22 Nov 2004, 02:29

Post

If a bike can pop a wheelie(so can a top fuel dragster), why can't the same thing be achieved with braking torque....

About the anti-pitch/dive bar, I think its not feasible for a regular car as the distance the bar needs to span is too great and hard to package, but I can see someone trying that at some point in Formula SAE when cars have ~ 60 inches of wheelbase....

User avatar
NickT
2
Joined: 24 Sep 2003, 12:47
Location: Edinburgh, UK

Post

Bikes (motor and paddle) frequently do do wheelies on the brakes, they are called Stoppies. Been trying to perfect them on my mountain bike for years :shock: with various degrees of success :twisted:
NickT

DaveKillens
DaveKillens
34
Joined: 20 Jan 2005, 04:02

Post

RH1300S wrote:Yes, but the if the caliper is mounted on the upright (in this case it is) - if behind the upright the direction the caliper will be moved in is upwards (and rotating). If you grab a spinning bicycle wheel with your hand, from the back your hand will be pulled up; from the front, downward.
Visualize your hand as the caliper on the right front brake, observed from standing outside, to the right of the car. If your hand was behind the center of the wheel, and you gripped the brake, your hand would be forced up. If it was fixed to the upright, it would be exerting a clockwise torque against the upright. If your hand was in front of the wheel centerline as you gripped the brake disk, you would exert a torque that too was clockwise. The location may be different, but the resulting force remains in the same direction and force.

dumrick
dumrick
0
Joined: 19 Jan 2004, 13:36
Location: Portugal

Post

RacingManiac wrote:About the anti-pitch/dive bar, I think its not feasible for a regular car as the distance the bar needs to span is too great and hard to package, but I can see someone trying that at some point in Formula SAE when cars have ~ 60 inches of wheelbase....
As a matter of fact, that piece of engineering marvel called the Citroen 2CV originally had interconnected central mounted springs, linked to the front and rear wheels of each side to achieve a anti-pitch and dive effect (and quite successfully, also). The 2CV had naturally (was a Citroen!!!!!) fully independent suspensions.
Image
http://home.iprimus.com.au/hobbier/chri ... pslow.html
Last edited by dumrick on 18 Apr 2006, 20:37, edited 1 time in total.

manchild
manchild
12
Joined: 03 Jun 2005, 10:54

Post

I agree about what's been said but I think we shouldn't mix position of calliper with location of point where calliper is attached. What I'm trying to say is that those might not always be identical positions or at least angles.

RacingManiac
RacingManiac
9
Joined: 22 Nov 2004, 02:29

Post

dumrick wrote:
RacingManiac wrote:About the anti-pitch/dive bar, I think its not feasible for a regular car as the distance the bar needs to span is too great and hard to package, but I can see someone trying that at some point in Formula SAE when cars have ~ 60 inches of wheelbase....
As a matter of fact, that piece of engineering marvel called the Citroen 2CV originally had interconnected central mounted springs, linked to the front and rear wheels of each side to achieve a anti-pitch and dive effect (and quite successfully, also). The 2CV had naturally (was a Citroen!!!!!) fully independent suspensions.
Image
http://home.iprimus.com.au/hobbier/chri ... pslow.html
it'll be more difficult to do with double wishbone though......most system nowadays are still hydralic based....which I guess is the same idea as the 2CV...

dumrick
dumrick
0
Joined: 19 Jan 2004, 13:36
Location: Portugal

Post

RacingManiac wrote:it'll be more difficult to do with double wishbone though......most system nowadays are still hydralic based....which I guess is the same idea as the 2CV...
In fact, in a thread here lost by the tides of time, there was mentioned an interesting system that was fitted in the WRC Citroens (still Citroen :D) that connects hidraulically the shock absorbers from diagonal sides (front left/rear right and front right/rear left), that was supposed to be responsible for a certain amount of the Xsara dominance in WRC. The function of this system is partly to control the lift and dive movements of the body of the car.

DaveKillens
DaveKillens
34
Joined: 20 Jan 2005, 04:02

Post


dumrick
dumrick
0
Joined: 19 Jan 2004, 13:36
Location: Portugal

Post

Thanks mate, that was it!!! :wink:

User avatar
Ciro Pabón
106
Joined: 11 May 2005, 00:31

Post

Thanks, Dumrick, great example of a longitudinal stabilizing system.

Now, if we use the movement of the antidive system to keep constant the distance between the diffusser and the road... :lol:
Ciro

RacingManiac
RacingManiac
9
Joined: 22 Nov 2004, 02:29

Post

University of Western Australia has the system, they purchased the license for it and integrated on their FSAE car.......