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Wedge brakes vs. Discs - half the stopping distance.

Discussion in 'Technical and Troubleshooting Torque' started by Loz, Nov 12, 2006.

  1. magnetic breaking principal by benz was flawed but good... nice, a no friction way of dealing witha dirty issue... If they could combine that with a dynamometer / moving coil assembly they could help bridge the gap for EV cars and bikes and generate power as they decelerate into a holding capacitor.

    +10 for getting rid of friction pads.

    this on ther hand appears to be a shapped friction pad on an offset caliper that is mehca-tronicaly applied to the disk surface instead of oil presure... so its fly by wire breaking...

    break the wire and fly? :shock:
  2. Electrical failure, at speed, such as what can happen in adverse conditions equates to a high velocity missile with no braking.

    I'm sure it works great, so long as it's working...
  3. Wedge brakes aren't new technology, they were used on certain heavy vehicles in the 1970's. The Denning interstate coaches we ran back them had wedge brakes.

    They worked good but buggers of things to get adjusted correctly though.

    They also had a servo feel to them as the braking effect kicks in... rather odd feeling... like a turbo delay on your brakes.

    The only difference I can see here is that they are electronically controlled rather than mechanically.
  4. Total load of crap. The limiting factor in braking any modern car is the capacity for the tyres to maintain grip. Any modern disc brake system has no prblem slowing a car/bike at pretty much any speed at a greater rate than the tyres are capable of.
  5. Whether or not the brakes can lock the wheels is not really a good measure of braking efficiency because it doesn't take into account how long it takes to achieve that level of braking. I mean plenty of old cars with front drum brakes could lock the wheels but that doesn't mean they're as effective as a 6 piston ventilated disc - since that will generate a given amount of braking (ie that required to lock the wheels) much faster, so braking distance will be greatly reduced. The biggest limiting factor to modern brakes is actually heat dissipation - these new wedge brakes might be more effective but that could just mean they might have a tendency to overheat.
  6. Actually, drum brakes can be incredibly effective, and sometimes more so than discs.
    Teh advantages of drum brakes are you can get a very large friction area in a small package, and they require lower hydraulic/air pressures to operate. They use a servo system to "wrap up" and self expand into contact with teh drum.
    This is why trucks stil use them, you can generate your own air on board, so loss of fluid or an air line is not catastrophic and you can store large volumes of compressed air for several safe stops if you lose a compressor, and you get massive surface area on teh drums/linings. Also air systems don't "dry up" or stick like hydraulic systems.
    Teh disadvangates of drums are weight (both from a rotating mass and unsprung weight point), not self adjusting, less driver "feel" and heat dissipation issues. They also don't work very well when wet.
    Don't expect drums to work too well after a couple of hard stops. Not only do they get hot, but the drum can "bell out" at it's open end when heated too much, causing loss of friction area!
    This is why discs are so popular today (light weight, feel, work at high temps), not so much because they offer superior stopping power.

    Regards, Andrew.
  7. All vehicles brakes (except parking brakes) work by converting kinetic energy to heat energy, then dissipating that heat energy asap.

    It follows that to work, the wheel has to be turning. Once it locks up you rely on the tyre to convert the energy to heat, by rubbing against the road. Tyres aren't very good at that, esp in wet weather, or oil, or gravel etc. Tyres are designed to do their job while turning.

    Disk brakes are more efficient than drums, solely because a disk dissipates the heat quicker than the drum can. Less weight in disks is easier to achieve, so another bonus is reduced unsprung weight. Drum brakes are more prone to "fade" due to retained heat, retaining heat means you can't keep generating more, equals less efficient.

    Another spin off is that disk brakes are easier to make, & easier to maintain, & basically self adjusting without requiring mechanical devices that could seize.

    They used to try to improve drum brakes with fins, spraying water on the outside surface etc. Drum brakes can be made to be "self energising", that is the shoe mounting is designed to allow the show to "wedge" itself into the drum, the harder it wedges in, the better heat conversion, the better the efficiency.

    Disk brakes normally require more effort to apply, they have no "self energising effect, so the tintops have power boosters to assist the steerer. Bikes tend to use more caliper pistons, bigger disk area, and a very high ratio between the master cylinder area and the caliper piston to give the mechanical advantage needed to work. If need be boosters can be added to bikes, but there is no need.

    Wedge actuated brakes have been around for ages, more often as a form of actuating drum brakes on heavier vehicles, even so the "S" cam actuators were superior, and easier to incorporate self adjustment via a simple ratcheting lever.

    I tend to agree that bikes just don't need this, we've only got one front wheel to cop all that braking effort now, we don't need more efficient anchors without a similar jump in tyre improvement.

    just my two cents worth :)
  8. [img:529:600:bed3b7b39a]http://www.richard-seaman.com/Aircraft/Museums/PearlHarbor/UssArizona/Outside/Anchor.jpg[/img:bed3b7b39a]
  9. So unexpected Ktulu, Forum Gold!
  10. Certainly an interesting prospect, but dependence on electrical power is a worry. I'd expect this to come out BMWs first, they already have a supporting technology in the pipeline (it's called Flexray) which removes hydraulic and mechanical linkages, in effect making everything fly-by-wire.
  11. it's all pointless imo - mercedes showed that a significant proportion of crashes occur because the driver didn't brake hard enough soon enough - ie not getting anywhere the potential of the braking system early in the process. Changing the brake actuation method will not change this flaw in your average untrained (ie practically everyone who doesn't do regular braking practice and speed and closure rate estimation practice) driver.

    Merc had the right idea with the unit that holds braking force a little longer after you get off the pedal if it senses a high braking effort and rapid pedal travel. Make the best of what you have - once you exhaust that capability, then move on to something with better performance.
  12. I agree with 97.34% of this .....

    Instead of looking at the benefit of greater braking performance look at it this way...

    No master cylinder (to become faulty), no brake hose (to become stretchy), No oil (to replace every 20k)....

    I think it will make bikes safer, because it is an area of maintenance that people tend to forget/avoid......

    Bring it on I say.... PROVIDING we can control input correctly.....
  13. Taken from the link.

    'A company official' will say anything if their getting paid to.

    Discs are fine, easy to maintain and stop very well.

    Drums are ok, bit more to maintain, more prone to fade but stop well when cool.

    Next thing 'A company official' will say is individual coils are new for ignition systems - Model T Fords had this in 1912 ish

    Makes me think of the Mag Lev train in Germany(?).
  14. I suggest thinking very carefully about the half stopping distance part. As people have already said, car braking is limited by tyres in almost every case (i.e. modern cars with unfaded pads and a brake booster).
    There's something about their test that they have neglected to mention and they're milking it for all it's worth (f***ing typical press release).

    Basically, don't get excited. If you think ABS intrudes on the driving experience, this is way worse. The servo effect is compensated for electronically which means that there's a computer constantly altering your input. At least with ABS you can test yourself and say "I'm going to brake as hard as I can without activating ABS".
    On the other hand it's a good idea for all the point A to point B muppets.