Safe Speed Forums

Just caught a programme on Discovery called "How It's Made"

The programme was describing a new version of disc brakes, in stead of the friction surface just being a couple of square inches, there is a series of pads all round the disc.
Apparently, it has been trialled on a Porche 911 turbo on a race track in a race.
Is there anywhere on the web with more info on this please?

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Semper in excreta, nur quantitat variat.

Not sure if this is exactly what you watched but i've heard about a new brake system where instead of a caliper with a brake pad in it gripping only a small part of the surface of the disc, NEWTECH have a system where there is a brake pad that is a ring that grips the disc all the way round. The Saleen S7 supposedly has it but the NEWTECH web site seems to allways be slow at loading and usually wont load at all. Hope this helps.

This doesn't make too much sense to me. Brake pad area is a trade-off. Obviously the greater the contact area the greater the distribution of the force and the less heat per unit area is generated for a given degree of braking power. However, since the area is increased, the overall power dissipated is the same and with the greater covered area, the disc has much less opportunity to convect the heat away. Furthermore, the increase in unsprung weight that inevitably results will compromise the optimum handling.

Yes. I've been puzzling the same puzzle since the original post appeared. I can't make sense of it either.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

not seen this...

i know a few brake suppliers have been toying with twin discs tho'

Twin discs would be good. I'm guessing they'd have to be a couple of inches separate so as to be able to clamp each one individually with direct hydraulic pressure with a compound caliper (as opposed to two separate calipers). The weight increase would be marginal and potential maximum retardation force nominally doubled with almost double the rate of heat dissipation.

Of course they're part way there with the ventilated discs (which is actually in practice two thin discs separated by spacers)

Aircraft use multiplate brakes. Much like a clutch with several plates in parallel. Also used on tractors and Tanks....!

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Speed camera policy Kills

Isn't it a bit pointless unless the grip of the tyres is seriously uprated to match? (And can that be done?)

In emergency and on decent dry metalled roads, most people with current brake pedal pressure requirements can't/don't reach the point of maximum grip - which is when the wheels are skidding but turning (if that makes sense).

Also in development is an electronically controlled "wedge" braking system which requires much less actuator force to apply. This is related to full "brake by wire" (i.e. non-hydraulic) systems where the high power required to actuate conventional calipers could not be easily provided electrically. How much "feel" this would have is anyone's guess. It does, however, address the issue of insufficient pedal pressure being exerted by drivers similarly to the BrakeAssist arrangement on Mercs.

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Malcolm W.
The views expressed in this post are personal opinions and do not represent the views of Safespeed.

I think this is whats being referred to. As you say, aircraft brakes use a 'pack' of stationary elements (stators) and rotating members (rotors, unsurprisingly). Consider a simple car brake disk (circular) and a couple of pads that grip perhaps 40 degrees or so. The system in question grips around all 360 degrees and can be multi-layered, i.e. numerous rotors and stator layers.
The stators attach to the hub and remain stationary, the rotors spin around with the wheel. Both elements can float inwards and outwards to a certain degree, they have to else the system won't work. When the brake is applied, a hydraulic piston forces the rotors and stators together.

Neat system, but I have strong doubts that it would work well for vehicle braking systems where the big problem is always getting the heat out.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Are control systems and actuators now sufficiently fast to make a "switch mode" braking system, overcoming a lot of the heat problem? I guess one can do this on planes given that tyres flatspot on landing and therefore can afford to act as the "inductor"

Can't see it being much use outside the race track.

I have never driven anything (without ABS) which couldn't lock up it's wheels on a dry road.

It will add a lot of initial expense though a set of pads might last a lot longer.

Hmmm, this is becoming a thread for the tech forum
For a light aircraft touching down at 80 or so knots, overheating isn't that much of a problem. Larger aircraft don't use their brakes on landing for intial decceleration, they have other systems such as thrust reverse or reverse pitch propellers. Thus, heat dissipation isn't a tremeandous problem and anti-skid mechanisms prevent lockups.
One of the tests a commercial aircraft must undergo before it is given its release to service certificate is an aborted take-off from maximum speed down to stationary using the brakes and then sit there for (I think) 15 minutes. The brakes will catch fire and deflate the tyres under such extreme circumstances.
Modern F1 cars use the brake pack system discussed above, and look at how those dancers glow cherry red under braking

Virtually any disc brake glows when used hard and the carbon discs used in F1 don't even work properly until they're at about 800 Celsius!... One of the many fun things about the 24 hour Le Mans race was to sit at the end of the Mulsanne Straight (before it was emasculated) and watch the cars at night slowing from 200+ mph down to about 40 for Mulsanne Corner - the discs would get white hot - sufficiently so to light the side of the road!!

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"Politicians are the same the world over... We build bridges where there aren't any rivers." - Nikita Kruschev

ermmm... reference please?