use of hydraulic brake separately in each wheel.

[himanu]

can any one tell me , how we control a brake of each wheel separately of 4 wheeler to one brake paddle ?......is it possible ?.......
brakes are hydraulic ( 2 drum brake in back wheel and 2 disk brake in front wheel )......

[himanu]

can any one tell me , how we control a brake of each wheel separately of 4 wheeler to one brake paddle ?......is it possible ?.......
brakes are hydraulic ( 2 drum brake in back wheel and 2 disk brake in front wheel )......

[RyMan]

2 proportioning valves. 1 in the front circuit and 1 in the rear. That's about as close as you will get. OR you could think about the function you want to achieve and design something from the ground up around that. Your call.

[PatClarke]

Easy Himanu,

Use 4 separate brake pedals!

And you only need to ask the question once!

Pat

[Menisk]

Actual serious question here for Pat (mainly a curiosity). The rules say the brakes have to be operated by one control do they mean pedals or are they talking about hydraulics. I like the idea of a hand clutch and two brake pedals, one for normal braking and one for rear only braking that actuates the same hydraulic cylinder as the normal pedal does for the rear. Kinda in a way that if you push the main pedal it takes the rear pedal with it.

[PatClarke]

You have been looking at too many tractors Menisk!

Don't ask me rules questions, 'cause on here I can only give an opinion.

Which is... 'One control' to me means one driver control to apply the brakes'. But if you are serious, then lodge a query with the rules committee, tha's what they are there for!

Pat

[woodsy96]

A rear brake pedal? Interesting - I would be thinking more along the lines (haha) of cutting brakes - two levers on the side of cockpit, offroad style. One operates the left rear brake only, one operates the right rear brake only.

More turn in please?

[Dunk Mckay]

Theoretically if you have pedal that does operate all the brakes then you do have that one control.

If you happen to have another pedal that does something else what does it matter? Howver brake circuitry is not something I've worked with so I'm all to familiar with the rules that apply. But if you can have a brake bias adjsutment to the system then why not a pedal for just the rears. Provided you can always lock up all four wheels.

[Owen Thomas]

You could always be super pro and adjust your brake bias on the fly, if you have that capability.
OR if you wanna be real creative you could have servos operating proportioning valves (1 front/back, 1 additional for each circuit operating left/right), and still have just one pedal. The more switches on your dash the better!

[Adambomb]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Owen Thomas:
You could always be super pro and adjust your brake bias on the fly, if you have that capability.
OR if you wanna be real creative you could have servos operating proportioning valves (1 front/back, 1 additional for each circuit operating left/right), and still have just one pedal. The more switches on your dash the better! </div></BLOCKQUOTE>

Very true...actually as I recall rally cars use a fast-action lever for brake bias for that purpose. Although the cutting brake does sound interesting...

[Menisk]

I just like the idea of being able to have an open diff and fiddle brakes on the rear so you can tap the pedal to brake the inside wheel and jam all the power to the outside wheel to use the rear to help point the car a bit. It could be twitchy as fuck, I have no idea.

[Buckingham]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I just like the idea of being able to have an open diff and fiddle brakes on the rear so you can tap the pedal to brake the inside wheel and jam all the power to the outside wheel to use the rear to help point the car a bit. It could be twitchy as fuck, I have no idea. </div></BLOCKQUOTE>

You don't need fiddle brakes to be able to use your feet to help the car turn... a good wheelman with a dash-mounted brake bias adjust knob will suffice http://fsae.com/groupee_common/emoticons/icon_smile.gif

Use some good ole fashioned lateral load transfer with a limited slip diff and all the drive power goes to the outside wheel as it is... If you want more yaw moment, push the right foot down harder.

[Warpspeed]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Menisk:
I just like the idea of being able to have an open diff and fiddle brakes on the rear so you can tap the pedal to brake the inside wheel and jam all the power to the outside wheel to use the rear to help point the car a bit. It could be twitchy as fuck, I have no idea. </div></BLOCKQUOTE>
Some full time four wheel drives do something like this. Three fully open diffs, and a traction control computer gizmo to lightly brake any spinning wheels. A sort of reverse ABS.

It would be an interesting design exercise to add a second pair of rear brake calipers to an FSAE car, some wheel speed sensors, and trick software to make an electronic "diff".

Steering angle, lateral G sensor, wheel speeds ??? you could really have some fun with something like that.

Keeping it completely separate to the main braking system would be wise I think, at least initially.

[Menisk]

Wouldn't that constitute brake by wire? Sure you have a legal primary system, but it's still brake by wire in the secondary one which is prohibited.

[Warpspeed]

A very interesting objection.

As the "electronic diff" would be entirely separate to the vehicle's main braking system, and it's function has nothing at all to do with braking, I suppose a smart lawyer could argue it is not really a "brake by wire" system.

I think it follows the spirit and intent of the rules, if not the letter.

[Dunk Mckay]

Not a bad idea. But, you would have to empirically prove that these brakes were not also used during brake testing, to lock all four wheels. Something that may be easier said than done. Yeah you could just take them off, but then you're not runnning your car witht he same setup as the dynamic events.

On another note has anyone ever had brakes not quite strong enough to lock the wheels permanently whcih gives an ABS like effect? We did eventually pass brake test after bleeding them properly(sigh), but actually stopped over a longer distance when they locked up fully.
(And yes I realise that at a higher speed the same effect would not quite work and the car would go flying into a marshall/tire wall).

Whcih brings me to my next question: If you were able to run the "secondary brake pad system" how easy would it be to restrict (even if just through driver restraint) the force applied through the normal brake pedal and have the additional calipers work as an ABS system?

[Warpspeed]

Thinking about this a bit more...

The "electronic diff" only needs to be active during near full acceleration.
In fact, you could turn it completely off during braking without any disadvantage.

As for ABS, that definitely would open up a can of worms regarding the "brake by wire" rule IMHO.

I see the intent behind the rule about brake and steer by wire is pretty clear. Major screw ups could, and probably would lead to a crash.

But I see a major failure in a traction control system as being far more benign.