rear pivoted MC's, are they really better??

[counter]

hey guys, can anybody please let me know if rear pivoted master cylinders are more efficient than the fixed MC's?
and also the provision to keep variable pedal ratio by rear pivoted MC's is good (but cost is high), Is there any way by which we can keep variable pedal ratio with fixed MC's?
I want to do analysis (simulation in ADAMS)of pedal box, to know which system would be more efficient,does anybody ever make such analysis?

[MalcolmG]

Efficient in what terms? Cost-efficient? Space-efficient? Mechanically-efficient?

[counter]

mechanically efficient
Originally posted by MalcolmG:
Efficient in what terms? Cost-efficient? Space-efficient? Mechanically-efficient?

[Pico]

Should ask yourself what is mechanical efficiency, how would you calculate it...that will answer your question. MC selection is more so dependent on cost and packaging.

[Whis]

Test it.

There are teams that have done it. My team has not yet, though we will by the end of this year.

Make a car that accepts both MC types and then run brake pressure transducers and do braking runs at max breaking. Look for repeatability. Might wanna run a force sensor in there too.

[Mehul Botadra]

I think its easier to change the bias bar settings then if the MC's are in front. Because you have everything integrated into one mount. Its a better design.

[Trevor]

In my mind, without rear pivoting master cylinders (MC), every time you apply the brakes the pushrods are being bent slightly, leading to increased friction in the seals and (i would expect) less driver control of the actual braking force on the car.

With a properly setup system, the balance bar should be perpendicular to the MC pushrods at the braking force needed to lock the wheels. Usually you end up with different MCs or line pressures front/rear, leading to different amounts of travel at the MCs. Therefore, the balance bar must start out at an angle to end up perpendicular at full braking. Everytime you brake, the pushrods, seals etc. must bend slightly to allow for this movement.

Is this actually a significant effect? Do we really care?

Gotta test it.

Also as a side note, rear pivoting MCs are @#$%@#^$ing expensive.

[Pico]

Fixed master cylinder pushrods allow for some misalignment (4deg on AP2623). The pushrods do not bend since they're free to angle themselves (ie two force members). The piston runs on the bore and the seals are not subject to radial loads (other than constraint of their expansion from the pressure crushing them axially).
In any case any increase in friction is negligible compared to the applied force especially with the mechanical advantage of the pedal.

Counter > If I understand what you're trying to do: you can make your own trunnion balance bar however you might have to incorporate different MC mounts as well to keep the misalignment within the allowable.