Position of a caliper

DaveKillens · Post 19 Apr 2006, 15:43

As a layman engineer, I am a great fan of systems like this. It's simple, inexpensive, reliable, and passive. Yet it solves some serious suspension issues.
To me, that's darn good engineering. make something simple, instead of finding a complex solution.

Ciro Pabón · Post 19 Apr 2006, 22:33

DaveKillens wrote:But if the brake caliper was allowed to float freely relative to the suspension, and an arm located between the caliper and chassis was used to transmit brake force, then you could influence the movement of the chassis relaitive to brake force and torque.

I read this post from DaveKillens and I thought: yeah, he is right, there are no arms between the caliper and the body, only the wishbone arms...

Well, after going through this thread I was looking for clutch pictures when I found this picture of 2005 Toyota's transaxle.

Suddenly I realized that this huge carbon composite wings behind the transaxles are joining the body of the car with the wheels. Well, it is the rear arm of the wishbone, I thought. Huge arm, probably for huge torque demands...

I never took a close look to an F1 transaxle before. I have made some, "layman engineer" questions on suspension, so here goes another:

Are there some invisible joints that allow the wheel to move? Does the carbon thing flex only? It is the rear arm of the wishbone? If so, where are the joints? Does this affect the conclusion of this thread on caliper position?

BTW, funny how the full carbon fiber part ressembles an airplane...

RacingManiac · Post 19 Apr 2006, 22:47

If I had to guess, and this is a somewhat educated one, the carbon fairing is actually the rear toe-link, which on F1 car is quite common to be located in the wake of the driveshaft for aero purpose. So it is actually a suspension component and is probably hinged at either end, hidden from view in that pic. It may be connected with a rodend, or like the a-arms, with a flexture.....

speedrcr · Post 20 Apr 2006, 16:24

I have had this discussion with quite a few people over the years. My conclusion is that the position of the caliper does not affect wheel loading (other the CoG position). The caliper/rotor interface is a force-couple with the spindle. The shear force being input by the rotor must be reacted by a force of equal magnitude but opposite direction by a load applied at the spindle. Since the caliper is mounted to the spindle/upright structure it is considered a "closed" system. Therefore, the only resultant seen by the chassis/suspension is the torsion load. As an experiment, lift the front wheels off the ground on your fwd car. Spin them up to 20 or so mph and hit the brakes. The do not move in the vertical plane! If they did, then you would have an unbalanced force system, the sky would fall, babies would cry, and Ferrari would win another championship....not a good day.

DaveKillens · Post 20 Apr 2006, 19:05

Mounting the caliper at the bottom would give a lower center of gravity, but it would not alter the forces transmitted through the suspension components under braking. But it would decrease the moment of inertia of the entire wheel assembly. But then again, that may not be desired. Having the caliper at right angles to the centerline of rotation of the upright would maximize the moment of inertia, and add a damping effect. Maybe that's a good thing. Of course there's the gyroscopic effect of the brake disk and wheel assembly, and not to mention gyroscopic coupling, but maybe a little added inertia is beneficial.
Most likely the package issues are very important. If the brake caliper is located on the bottom, it's uncomfortably close to the lower upright bearing, something a source of heat would be an issue. As well, the brake line would have to run and be exposed lower down. It would be more vunerable to something striking it or snagging it. Keeping any brake lines concealed and up high to avoid damage is important.

NickT · Post 20 Apr 2006, 19:13

Suspension movement is acheived using flexures at the chassis side mountings

These used to be titainum or something similar, but are now carbon fiber

Hope this helps

RH1300S · Post 20 Apr 2006, 22:22

speedrcr wrote:I have had this discussion with quite a few people over the years. My conclusion is that the position of the caliper does not affect wheel loading (other the CoG position). The caliper/rotor interface is a force-couple with the spindle. The shear force being input by the rotor must be reacted by a force of equal magnitude but opposite direction by a load applied at the spindle. Since the caliper is mounted to the spindle/upright structure it is considered a "closed" system. Therefore, the only resultant seen by the chassis/suspension is the torsion load. As an experiment, lift the front wheels off the ground on your fwd car. Spin them up to 20 or so mph and hit the brakes. The do not move in the vertical plane! If they did, then you would have an unbalanced force system, the sky would fall, babies would cry, and Ferrari would win another championship....not a good day.

Good description - I certainly saw the torsion aspect, but imagined another force too..........I think you have convinced me

Ayrton · Post 04 Jul 2006, 06:57

The other day I was thinking about this when I was looking at the design of our fsae car. I agree with dave about the moment being the same whether the brake caliper is fore/aft of the the upright but... if you have the caliper on the front of the car won't the inertial force created by the breaking force applied to the rotating wheel increased the vertical load on the tire? Whereas if the caliper is in the read it lessens the load on the tire (and if it the care were light enough and the breaking force massive: lift the tire off the ground)

I thought of an anology that got me going on this. When you are on a scale it displays a certain weight - but if you were to exert an inerntial force it with a body movent the scale would read more weight momentarily. Under the same reasoning if the wheel is suddenly applied a braking force by the brake pad can't it pass a vertical force on it that would pull the rotor and the rest of the wheel assembly up?

NickT · Post 04 Jul 2006, 13:55

Sorry, but no

Because, as speedrcr wrote, it is a closed system the torsional load is the same with the caliper mounted at the front or the rear. If you think about the upright mountings see it is the same torsional loading in the same direction regardless of whether it monted at the front or rear of the upright.

f1.redbaron · Post 05 Aug 2006, 00:42

Just in case anybody wanted an update...

Last week during Friday's practice, Steve Matchett answered this question. He was talking about the position of the caliper on a Honda, and he said that ideally, teams would put it as close to the ground as possible, to keep the CoG as low as possible.

So, manchild, you were the first one to say that...and you were right!

manchild · Post 05 Aug 2006, 01:42

me, me, me

manchild · Post 24 Dec 2006, 23:50

It appears that Mclaren has applied such solution at USGP 2006.

http://mediacenter.gazzetta.it/MediaCen ... V=Formula1

ss_collins · Post 27 Dec 2006, 15:39

I seem to remember a few years ago Minardi running its rear calipers at the bottom of the disc - anyone got any pics?

Reca · Post 27 Dec 2006, 18:12

sscollins wrote: I seem to remember a few years ago Minardi running its rear calipers at the bottom of the disc - anyone got any pics?

I don’t have pictures but Minardi indeed is the team that introduced the rear caliper at the bottom (although not perfectly horizontal) in 1999, since then gradually all the teams adopted it and it's a common solution since a few years now.

McLaren used the front caliper at the bottom in 2003, then reverted to vertical (possibly mid season) till 2005, when they put it again at the bottom on the Mp4/20, possibly helped by the fact that the no keel design already requires the lower wishbone to attach quite high on the upright. The 2006 Mp4/21 kept the same solution.
In 2003 also Jordan had the front caliper at the bottom but reverted to vertical for following years.

Edit : I checked my pics, McLaren had the front caliper at the bottom in 2002 already with the Mp4/17 that then was upgraded for 2003 waiting for the 18 debut that never happened. Then they reverted to vertical front calipers during 2003.

tomislavp4 · Post 28 Dec 2006, 15:05

What´s this?
http://mediacenter.gazzetta.it/MediaCen ... V=Formula1
Some kind of magnetic dumper or....