Rapid Brake Bias Adjuster

[hardingfv32]

How might the balance bar mechanism at the master cylinders be designed to facilitate rapid brake bias adjustments?

Are the rapid adjustments simple high/low movements, from one adjustment stop to the other?

Is there still a facility for fine bias adjustment that is available to the driver?

Brian

[Jersey Tom]

Define "rapid."

From that Ferrari video not long ago it looked like there was the standard continuously adjustable bias adjustment and then a small control with which the driver could do a step change more or less around that centered point.

[langwadt]

How might the balance bar mechanism at the master cylinders be designed to facilitate rapid brake bias adjustments?

Are the rapid adjustments simple high/low movements, from one adjustment stop to the other?

Is there still a facility for fine bias adjustment that is available to the driver?

Brian

That is what they are adjusting when you see them put their one hand down in cockpit next to the left leg
I think it has few fixed settings they can switch between

[hardingfv32]

Define "rapid."

Well, I was thinking of the adjustment that we see the driver doing when he moves his hand to the side of the cockpit.

The rule seem to preclude the use of a motorized bias adjustment system. We are then left with a mechanical or hydraulic solution. Can the rapid movements of the cockpit lever be converted to some kind of screw type system that is common for most bias bar systems?

Brian

[piast9]

As far as I know this system is really, really simple. There are two master cylinders but unlike in the road car one is for the front and one for rear brakes. The master cylinders are placed in parallel one beside the other. The pistons in these cylinders are connected with transverse bar and the brake pedal acts at the place on this bar which is adjusted with brake balance lever. If the place is closer to the rear brake master cylinder then the bias is shifted back. If it is closer to the front brake master cylinder the brake bias is shifted to the front.

[hardingfv32]

As far as I know this system is really, really simple... and the brake pedal acts at the place on this bar which is adjusted with brake balance lever...

Simple?? What is the design of this bias bar mechanism? The normal threaded rod system, unless motorized (forbidden by rules), is going to be slow to adjust. So how is the motion of the cockpit level converted to a motion at the bias bar? A large pitch thread system?

Brian

[Jersey Tom]

As far as I know this system is really, really simple... and the brake pedal acts at the place on this bar which is adjusted with brake balance lever...

Simple?? What is the design of this bias bar mechanism? The normal threaded rod system, unless motorized (forbidden by rules), is going to be slow to adjust. So how is the motion of the cockpit level converted to a motion at the bias bar? A large pitch thread system?

Brian

A common setup comprises two MC's which are parallel, side by side to each other as piast9 indicates. They are both actuated simultaneously by means of a bar perpendicular to the axes of the MC's. Where the pedal force is actuated on that bar, is how a brake bias adjuster works. As that point moves closer to one MC or the other, force is biased in that direction.

The cockpit knob adjustment ultimately is translated to a linear displacement of that point via a screw thread. A lever adjuster is even easier to implement as it is a direct linear translation by itself through a push/pull cable or something of that nature.

[hardingfv32]

A lever adjuster is even easier to implement as it is a direct linear translation by itself through a push/pull cable or something of that nature.

The details of 'something of that nature' are what interests me. I would say that a 'direct linear translation' would be much more difficult to do than you think if one considers the accuracy require by this adjustment. Very few classes of race cars adjust brake bias multiple times per lap. Those who do are expecting a high level of refinement in the adjustment. Beyond the normal threaded bias bar adjuster and one motorized system, there does not seem to be anything else available commercially. If a lever system was easy to do, I would expect it to be commercially available.

Brian

[gato azul]

AKAIK, the adjustment they make is independent of the normal bias bar adjustment, which they still have and use.
Ask yourself what would happen, if after a bit of travel, one MC could not move anymore, or only against a spring (which would mean that one part of the force coming from the pedal, is taken up by the spring), but the pedal and other MC still move.
What would that mean to the brake force/pressure distribution and the bias? Maybe the bias is not constant over the full range of pedal movement &/or brake pressure range?

And please stop with this, "but I have never seen it in a shop/catalog , so I doubt it exist" way of thinking, that's pretty childish - sorry no offence intended, but there is a lot of stuff in use, that you can't buy down at Demon Tweaks or Summit or wherever you get your stuff from.

[Jersey Tom]

A lever adjuster is even easier to implement as it is a direct linear translation by itself through a push/pull cable or something of that nature.

The details of 'something of that nature' are what interests me. I would say that a 'direct linear translation' would be much more difficult to do than you think if one considers the accuracy require by this adjustment. Very few classes of race cars adjust brake bias multiple times per lap. Those who do are expecting a high level of refinement in the adjustment. Beyond the normal threaded bias bar adjuster and one motorized system, there does not seem to be anything else available commercially. If a lever system was easy to do, I would expect it to be commercially available.

Brian

Push pull cable along with a lever in a slotted guide for the three settings. Easy, "commercially available" and cheap. Pretty much the same setup as what some racecars use for cockpit-adjustable front or rear ARB.

[hardingfv32]

Ask yourself what would happen, if after a bit of travel, one MC could not move anymore, or only against a spring (which would mean that one , is taken up by the spring), but the pedal and other MC still move.
What would that mean to the brake force/pressure distribution and the bias? Maybe the bias is not constant over the full range of pedal movement &/or brake pressure range?

And please stop with this, "but I have never seen it in a shop/catalog , so I doubt it exist" way of thinking,

1) I would question 'one MC could not move anymore'. This would seem against the basic safety premise of a dual master cylinder system... that you have one circuit available in the other circuit fails.

2) Losing 'part of the force coming from the pedal' is not acceptable with the forces required to stop a F1 car.

3) The quote is "If a lever system was easy to do, I would expect it to be commercially available." This statement is accurate when discussing the easy of designing a lever type system. IF it were easy, it would become commercially available. This say nothing about wether it is possible or not.

Brian

[hardingfv32]

Push pull cable along with a lever in a slotted guide for the three settings. Easy, "commercially available" and cheap. Pretty much the same setup as what some racecars use for cockpit-adjustable front or rear ARB.

Yes, the lever end of the system is common, but what is the rough design of the bias bar mechanism that uses linear motion from the shaft/cable?

Brian

[Jersey Tom]

Push pull cable along with a lever in a slotted guide for the three settings. Easy, "commercially available" and cheap. Pretty much the same setup as what some racecars use for cockpit-adjustable front or rear ARB.

Yes, the lever end of the system is common, but what is the rough design of the bias bar mechanism that uses linear motion from the shaft/cable?

Brian

Exact same as one that uses a twist action. The twist knob you usually see in a car ultimately creates a linear displacement at the balance bar. Moving the force application point from side to side is what creates the biasing action. Whether the thing moves directly with a push/pull action, or with a screw thread, is immaterial. All of this stuff is commercially available, and cheap. Could do the whole thing for a couple hundred bucks (including fab/assembly) and with almost entirely off the shelf pieces.

[silente]

In my opinion the basic point is still, as JT said at the beginning, to define quick.

A complete turn of a standard brake bias adjuster can (depending also on the thread in use, the goemetry of the system, etc) shift brake balance up to 1.5 - 2% in some cases. In my experience that is an adjustement that most of the drivers could feel quite well. Sensitive drivers can feel the difference produced also by 0.5% shift.

Just to make an example, in my experience also with full wet conditions you don´t move brake balance more than 5-6% (at least on single seater cars).

Maybe this numbers are different when you have huge level of downforce as in formula 1.

So i would say that also a basic system with a threaded bar moving toward one or the other MC would be quite "fast" to adjust for many application.

Of course formula one is using something different, but it is a very top end performance example and actually drivers are doing a lot more operations in their cockpit than what you would do with a lower level race car.

[riff_raff]

I'd imagine that there more effective ways to adjust F/R brake bias than the old tried-and-true method of dual MC's and a pedal balance bar using screw threads. One thing I would imagine that F1 brake systems use is a hydraulic circuit that circulates the brake fluid through the caliper to keep it from overheating. An in-line check valve and a return line that moves the fluid in a loop after each application of the brakes.

I'd also think that the clever engineers in F1 would have come up with some sort of adjustable or dynamic valving system that would work better than the old balance bar.