When will FMCSA force disc brakes upon the industry?

Carbon-carbon brakes are the ultimate for total heat rejection capacity. And they do last a long time. They are the pits for for braking torque. Cost for carbon-carbon brakes is enormous, though it might be reduced some by true mass production. They are better in many ways, but not in all ways.
For carbon-carbon brakes the required swept area for a given braking torque is much higher than the present drum brake and material used in them. Multiple discs are common on aircraft. Race cars use single discs, but the rotor size is large compared to weight of vehicle. A truck would probably need multiple discs, or larger wheels, or higher application pressures (difficult if you stick with the given air systems) if carbon-carbon were used. Also, the temperatures reached on carbon-carbon brakes is extreme, much higher than present drum brakes.
As long as the design requirements are a single stop, on level ground, at speeds less than about 55mph, the drums have the advantage. Change the requirements (politically speaking this is likely) then the advantage may swing to discs. As it stands today, I think a good disc is better than a bad drum, but a good drum gets the job done, usually.
I was attempting to be a little humorous about the fancy materials for drum brakes, though technically they would work. I would never expect to see any of those materials used, except the rarest cases. I have designed a titanium brake drum for a very special purpose (one of a kind and no not for a truck or a car) and we looked at some rather exotic materials before settling on the titanium. These materials were considered standard stuff in my previous industry.
How about electric motors/generators that convert the kinetic energy into stored energy in a battery, then give it back on the next throttle up?
Ok, maybe I am stirring the pot. My bad. But the engineer in me has escaped, again, and he is having so much fun!

 

i would think some sort of regenerative dynamic braking would be the bees knees. its a tad more expensive but its the "eco Friendly" cough cough solutions.

 

Our company bought three new trucks equipped with disc brakes all the way around back in 1982. Nobody wanted to drive them because they'd scare the heck out of ya on the long down grades. They couldn't hold you back................

Some other problems as I recall were constant and ongoing brake release problems after setting the parking brake. And another thing, the brake pedal had absolutely no feel to it, kinda like stepping on a block of wood as I recall.

Two of the trucks were converted to drum brakes shortly after the third truck crashed and burned near sunset point on I-17 north of Phoenix. One fatatility, the driver who happened to be a decorated viet nam vet.

 

Sorry there Kiviknon, my English education was shortened to allow for more physics. Sometimes I forget to add that extra 'return'. And of course my spelling, typing, and grammar have been known to be less than perfect, usually much less.

yestirday i couldn't spel enganere, today i are one! (old engineering joke, with a lot of truth to it)

 

For those comparing 80s disc brakes to those of today... should remember that 80s drums wouldn't stand a chance against today's drums either, so not really a fair comparison. Now I did look up some information the other day and saw that on average an all steel disc brake setup adds about 200 lbs per axle to the truck...but they have new steel and aluminum hubs that shave off about 100 lbs an axle (making them lighter than drums).

So now the question does anybody have a modern (2009+) truck with disc brakes that could share their experiences? (especially if they're running the lighter hubs)

 

UPS is testing this using hydraulics rather than electric. Much as Honda/Toyota/etc have discovered with the electric hydrids; I'm sure getting brake feel somewhat normal is quite the challenge for the engineers. But what a simple way to borrow some 'stop' for some 'go'.

 

Hydraulics can certainly be made to work. My studies in the past always came to the same conclusions and that is : The system to be used depended on the systems already on the vehicle. Large trucks do not normally have a major hydraulic system, where as virtually all have significant electrical system.

But my studies were always focuses on much smaller vehicles, so that could have major impact. The energy levels involved in stopping a large heavy truck, could be large enough that storing the energy in accumulators is lighter, more efficient than batteries. We are talking about 500 million ft lbs of energy. Accumulators last longer than batteries, etc. So Hydraulics at this size might be better way. It would be an interesting trade study (I am sure someone did it already).

Only real down side that I know of is that accumulators that size can be very dangerous if damaged. But big batteries are not the safest things either.

Additionally, it might be desirable to not combine the system.

In the past, getting feel in the system was considered difficult for hydraulics, but with computer controls getting feel is just a matter of defining what is 'good feel' (You will get a lot of variations since it is mostly a matter of opinion).

Either way, it could certainly add to mileage in a 'stop and go' type truck.

All is of interest to me. And actually, I know, and prefer, a lot more about hydraulics than electrics.

 

I don't recall any problems with drum brakes back in the 1980's or the 70's or the 60's .........They worked just fine. I left the biz in 1989, drum brakes were still working just fine.