So initially I thought it was just a drum brake that applied the braking force on the face of the drum in stead of on the circumference. But it seems the key invention here is some camming system that automatically increased the braking force as speed increased. So this system supposedly did not require a brake booster as part of the hydraulics.
I wonder what prevented this camming innovation from being transferred to the more conventional drum brake of the time?
I'm not an engineer, but I do have some wrenching hours under my belt. I see a flaw in the design: The two halves of the drum are held together by machine screws/bolts. The braking pressure from the pads is applied directly to these screws. If they are not properly fastened, or if they are loosening over time, then braking force will be directly impacted. A failure could result in a total loss of braking ability. A conventional drum or disk brake is kind of fail safe in that regard: The mechanical pressure from the brake pads is not transferred through any fasteners. I see this design less resistant to poor maintenance practice. Maybe they somehow accounted for this and the article failed to mention it.
The mechanism reads a lot like an admittedly more sophisticated version of what existed in early mountainbiking as the "self energizing" Pedersen brake. More braking for less force, but terrible at dosing. I'd be surprised if this mechanism did not suffer from the same problems.
Leading shoes on drum brakes were self-energizing like the old Pedersen mountain bike brakes. With a leading shoe the pivot point is after the braking surface, so the friction tends to push the shoe harder against the drum. Most drum brakes had one leading and one trailing shoe.
Some motorcycles even twin leading shoes on the front (maybe even four leading shoes with two sided drum brakes). These had issues with modulation like the Pederson brakes. You also had twin trailing shoes when backing up, so you had to squeeze the brakes extra hard then.
> A conventional drum or disk brake is kind of fail safe in that regard: The mechanical pressure from the brake pads is not transferred through any fasteners.
A slight nitpick, the torque applied to the caliper from the disc, through the pads, does travel through the caliper mounting bolts. It's a lateral force rather then a axial one but it does go through fasteners.
On most, no, little to no braking force is taken up by the fasteners themselves. For most designs the calipers sit inside a frame that takes the braking force, and the fasteners simply hold the caliper in alignment within that frame.
This wikipedia photo happens to be from an AMC pacer, but it does show the frame that takes the braking torque load (https://en.wikipedia.org/wiki/File:Detail_of_-_AMC_Pacer_-_r...). The frame is the lighter metal object at the top above the top edge of one of the pads.
I go to pains to not mention torque, because I'm not talking about that. I'm talking about the physical pressure exerted by the pads on to the surrounding structure. The forces involved even when the vehicle is not moving.
The start of America's automotive golden age was ripe with innovation. You could buy a car in 1964 with methanol injection! They had turbos 20 years before Saab!
Unfortunately for America, Europe's scarcity cars were not fit for her market, so Detroit had very little competition. They also had no resource constraints. Once certain dimensions of consumer preference settled, Detroit coasted.
Europe and Japan were poor, so they had to work to make good cars. They were also culturally open to each other.
The american car industry took a deep nose dive because the cars they were building in the 70s and 80s struggled to crack 100,000 miles without a major issue, and the interiors literally fell apart in your hands. I'll never buy a GM or Ford because I grew up in them and the door handles were falling off and stuffing was shooting out of the splits in the seats. The paint not even 10 years old was so oxidized it would rub off on your clothes if you rubbed against it. If GM and Ford are better now, I wouldn't know because I haven't been in one in literal decades. The only reason they're still around today is the chicken tax (it's a real thing, look it up) and the fact that you can't buy a full size car anymore outside of marques like the Mercedes S class and BMW 7 series and a handful of others, largely top end halo cars.
I kind of want some for my 80 series, the factory hand brake is terrible (linkages rust and it tends to drag on the rhs wearing prematurely). The sealed design is awesome. The only drawback I can see is the separate high pressure pump and control package seems like a pretty high complexity tax. And I bet they're not cheap.
EDIT: Another question I wasn't able to figure out from their brochure is how they integrate with the factory front disc brakes.. Like, is there some kind of balance control?
My dad and I have an old Case backhoe that we got with bad brakes. Turns out they're very similar to this design, with a ball and ramp assembly that pushes clutch discs outward into friction surfaces. A couple notable differences are that they use a a band around the disc assembly, connected to the pedal, that slows the disc assembly causing the ramps to engage. And also, they're attached to a couple of splined shafts coming out of each side of the differential, rather than on the wheels/axles. Anyway, apparently they're notoriously troublesome, and were a lot more difficult to rebuild than I would have thought.
Interestingly, the ball and ramp mechanism persists in mechanical disc brakes for bicycles, at least on the Avid BB-7's (possibly others, those are the ones I have).
In that case the ball and ramp are in the caliper attached to the frame. I don't think they're self-energizing in that application; the balls aren't all traveling in the direction the rotor is.
I'd say they're at least 85% as good as hydraulic disc brakes while being 1% of the hassle to maintain.
What is the hassle with maintaining hydraulic disk brakes on a bicycle? On my motorcycle, you replace the brake fluid and inspect the rotors to make sure they are in tolerance every couple of years, check the pads for wear, the lines for damage and replace if needed every oil change, and that is pretty much it. I would imagine that bicycle hydraulics are even easier to maintain, if only because they don't have nearly as much energy to dissipate as motorcycle brakes do.
1. The knowledge of how to deal with hydraulics across the industry is slowly accumulating. We've been fixing bikes with bowden cables for a hundred years give or take a bit. We've been dealing with hydraulics for 25 years give or take a few, and it's a really recent development that they've trickled down to the low end of the market and penetrated the road market at all. The knowledge of how to fix them is not as widespread as you'd think.
2. Compounding the above, we have two competing systems (naturally). SRAM runs DOT fluid and Shimano runs mineral oil. The bleeding procedures are different (naturally). Surprisingly, the hygroscopic nature of DOT fluid is a non-issue. Both systems run hard for a year are basically due for a fluid change.
2.5. Some of the bleed procedures are consistent within a manufacturer's line over time. Often times they are not. Step one of a bleed is usually RTFM because the brakes you're looking at are probably different from the last three sets you've done.
3. Everything is small. The entire master cylinder assembly has to fit inside the brake lever. On a road bike, your hand wraps around all of that, plus the shift mechanism. Access to the reservoir cap, which is also the bleed port is about as good as they can make it, but it's still one more damn thing to peel back the rubber hood.
4. The calipers are similarly small, leaving less room for sealing, etc.
5. There's little room for manufacturing variation in the mounts as well. In theory this would affect mechanical disc brakes as well. In practice, they hold up better when the caliper is mounted cockeyed. Park Tool makes an extremely elaborate facing kit to rectify problems with mounts. The shop I work at part-time has one, and I've had to use it. The fact that the rotor is non-rigid does buy you some tolerance back, but sometimes it isn't enough.
All of the above adds up to a lot more hassle than mechanical disc brakes not because it's insurmountably hard to do the work. The major factor is that a good set of mechanicals is so damn simple and reliable. The set on my mountain bike has 7000 miles of touring, plus mountain biking, and I doubt I've spent cumulatively 3 hours working on them.
1. Despite being relatively new, bicycle hydraulic brakes are dead simple. There isn't much to learn, unlike the switch to discs which was a much bigger change. You also don't really need to fix them when a pre-bled set of Shimano MT-200 brakes is 25$, in case you find yourself with a hairy problem a bleed won't fix.
2.1 The industry is converging on mineral oil, as SRAM now has mineral oil brakes. Also, their hygroscopic nature actually is a problem: good quality mineral oil brakes last years between bleeding, which is rare for DOT fluid.
2.2 Mineral oil bicycle hydraulic brakes are very different from hydraulic oil on cars or some bikes - it's a sealed hydrophobic system. You don't need to bleed them unless there is a leak or dirt gets past the seal, and if you don't the worst that happens is that they gradually get mushy.
Meanwhile, if you don't bleed motorcycle or car brakes you can very suddenly lose braking power when you need it, for an unwisely designed sealed DOT system your brake line can literally burst open. But that's not a problem with modern good quality mineral oil hydraulic brakes.
2.3 This is a SRAM problem. Shimano hydraulic brakes are bled almost identically, and though doing a full flush changes a bit every now and then the change is always very minor (and you rarely need to do a full flush)
3. Things don't need to be big. You're not going to be messing with the master cylinder realistically speaking. Also on the most widespread hydraulic brakes there is no rubber hood around the bleed port, just screws that have o-rings around them.
4. The calipers aren't small at all. Look at top of the line weight weenie road bike calipers to see what an actually small caliper is. Common mountain bike calipers are not especially limited by size, they just don't need to be bigger than they are. In mountain bikes they get bigger if you pay more.
5. This is completely false. 2-piston or better yet 4-piston hydraulic calipers, along with convex-concave washers (this is very very important) offer by far the most flexibility as to mount facing. You can easily trick yourself into thinking that mechanical disc brakes are better due one of the pads being rigid and easy to offset as to accommodate a skewed rotor: this almost always backfires hard down the road once the pads start to wear askew. Also, for extreme cases we have floating rotors. The big thing though is to use concave/convex washers: after doing that I've often had bikes that just wouldn't work right with mechanical calipers work perfectly with cheap hydraulic calipers, I'm talking about a good 5 degrees out of alignment on the mounts in the pitch/roll axis.
I've put 9000 miles on my bike and I've only bled it once in 4 years. I haven't had to do any hydraulic specific maintenance at all, the most time I've spent was changing pads, changing/truing rotors, and aligning my calipers (often while waiting for my concave convex washers to come, after which it took all of 2 minutes and a business card).
The bicycle parts are lighter/smaller/cheaper. They are more fiddly. But energy-wise, because they are so much smaller/lighter/cheaper they are dissipating a smaller amount of energy across a vastly smaller set of parts. Heat is still an issue. A 500lb motorcycle+rider dissipates heat across a pair of front disks, both of which can weigh more than an entire bicycle front wheel. A 200lb bicycle+rider focuses everything on a single disk that weighs in at a couple ounces.
They're not such a hassle. There's millions of people riding about on MT-200 brakes that never saw an Allen key since they left the factory. They used to be a lot more finicky, and some niche ones still are, but mass market hydraulic brakes are extremely easily to maintain.
I have these brakes on a vintage massey ferguson 178 tractor. the mechanism tends to push back up the pedal when pressed, and the stopping force is weak. there is a reason mf moved abandoned the design.
Looks more like a typical manual car clutch setup, but interesting anyhow. Definitely more complex than the modern equivalent. Would not want to work on these..
Early brake discs were often maintenance nightmares. Discs built into the hub (so you need to disassemble wheel bearings to take the discs off) or even worse, Jaguar's inboard rear discs (reduced unsprung mass, but you needed to remove the driveshafts and they were buried in the middle of the car). Lots of premature optimization went on.
The pads are very thin and i dont see how they could be made thicker, them being inside the mechanism. I am not sure they would last nearly as long as conventional pads.
I don’t know enough to comment on the design overall, but my immediate thought was it looked much harder to replace the pads than in disk or drum brakes.
I wonder what prevented this camming innovation from being transferred to the more conventional drum brake of the time?
I'm not an engineer, but I do have some wrenching hours under my belt. I see a flaw in the design: The two halves of the drum are held together by machine screws/bolts. The braking pressure from the pads is applied directly to these screws. If they are not properly fastened, or if they are loosening over time, then braking force will be directly impacted. A failure could result in a total loss of braking ability. A conventional drum or disk brake is kind of fail safe in that regard: The mechanical pressure from the brake pads is not transferred through any fasteners. I see this design less resistant to poor maintenance practice. Maybe they somehow accounted for this and the article failed to mention it.