weinmann semi automatic brakes -- what is it?

Discussion in 'Cycling Equipment' started by geos, Apr 13, 2006.

  1. geos

    geos Guest

    hello,

    does anybody know this weinmann model of "semi automatic" brakes? I
    can't find any information on the net. I would appreciate any technical
    details and history details, when they were produced, what was their
    braking efficiency etc. can they be compared to campagnolo deltas?

    any information and personal experience with this brakes would be helpful.

    http://img527.imageshack.us/img527/6392/weinmann8cm.jpg

    thanks,
    geos
     
    Tags:


  2. JeffWills

    JeffWills Guest

    geos wrote:
    > hello,
    >
    > does anybody know this weinmann model of "semi automatic" brakes? I
    > can't find any information on the net. I would appreciate any technical
    > details and history details, when they were produced, what was their
    > braking efficiency etc. can they be compared to campagnolo deltas?
    >
    > any information and personal experience with this brakes would be helpful.
    >
    > http://img527.imageshack.us/img527/6392/weinmann8cm.jpg
    >
    > thanks,
    > geos


    "Semi-automatic" refers to the adjusting mechanism, I think. It
    self-adjusts the slack in the cable.

    As to the brakes "efficiency", well, I dunno. I can just barely
    remember seeing these brakes when they were new in the late '80's... I
    think. I don't ever remember seeing them on a bike.

    Jeff
     
  3. Jeff Wills writes:


    >> Does anybody know this Weinmann model of "semi automatic" brakes? I
    >> can't find any information on the net. I would appreciate any
    >> technical details and history details, when they were produced,
    >> what was their braking efficiency etc. can they be compared to
    >> Campagnolo deltas?


    >> Any information and personal experience with this brakes would be
    >> helpful.


    http://img527.imageshack.us/img527/6392/weinmann8cm.jpg

    > "Semi-automatic" refers to the adjusting mechanism, I think. It
    > self-adjusts the slack in the cable.


    > As to the brakes "efficiency", well, I dunno. I can just barely
    > remember seeing these brakes when they were new in the late '80's...
    > I think. I don't ever remember seeing them on a bike.


    It's like the Modolo Kronos that was a forerunner to the Campagnolo
    Delta-I and Delta-2, both of which had the same fatal design error of
    a variable mechanical advantage. It took Campagnolo years to
    discover why riders crashed with these brakes. The brake has a
    variable mechanical advantage (MA) getting more aggressive as pads
    wear. Beyond that, the MA increases with harder brake application as
    pads bulge and brake arms flex.

    Brakes must have a constant ratio of hand force to brake effect to be
    controllable. This design uses a parallelogram with the brake arms
    attached to two corners and the cable pulling the other two corners
    together, giving a mechanical advantage that goes from zero to
    infinity, mathematically: a tangent function. Note that the brake
    arms are short and pivot so that the pads rise into the tire with wear
    (known as cosine effect).

    Observing this, It seems that these engineers never learned about the
    "bell crank" or for instance, parallel universal joints on car
    propeller shafts.

    http://tinyurl.com/eoj5u

    Note that motion in equals motion out, the two legs of the mechanism
    having the same cosine error that the bell crank cancels

    It's a stupid idea for several reasons and it was even worse when
    Campagnolo went through two versions before giving up on the concept.
    I don't know if they ever discovered why the brake is a dud. It's
    like Shimano and their Octalink (also two versions) showing that they
    did not understand why it fails.

    Don't ride these things. Put them in your museum of failed ideas.

    Jobst Brandt
     
  4. geos wrote:
    > hello,
    >
    > does anybody know this weinmann model of "semi automatic" brakes? I
    > can't find any information on the net. I would appreciate any technical
    > details and history details, when they were produced, what was their
    > braking efficiency etc. can they be compared to campagnolo deltas?
    >
    > any information and personal experience with this brakes would be helpful.
    >
    > http://img527.imageshack.us/img527/6392/weinmann8cm.jpg
    >
    > thanks,
    > geos


    I just installed one on the front of my TT bike. The spring force is
    noticably higher than modern dual pivot brakes. It's not easy for me to
    modulate, and I don't like it's performance. But it's only my TT bike,
    and I think it's aero.

    Since I use a housing stop in the headset, I sawed off the adjustable
    part (top 25mm or so), but I kept the rubber cover on. I can't see how
    to get it off without tearing it.
     
  5. geos

    geos Guest

    thanks to all who replied,

    cheers,
    geos
     
  6. On 14 Apr 2006 04:50:57 GMT, [email protected] wrote:

    >Brakes must have a constant ratio of hand force to brake effect to be
    >controllable.


    Why? You've stated this as an axiom numerous times, but I don't believe
    I've seen the reasoning behind it. I'd think that at least small
    variations in MA wouldn't make a brake uncontrollable (although probably
    harder to do so).

    Jasper
     
  7. Jasper Janssen writes:

    >> Brakes must have a constant ratio of hand force to brake effect to
    >> be controllable.


    > Why? You've stated this as an axiom numerous times, but I don't
    > believe I've seen the reasoning behind it. I'd think that at least
    > small variations in MA wouldn't make a brake uncontrollable
    > (although probably harder to do so).


    If the MA is variable, you cannot dose braking such that you don't
    crash some time or other. Today we have disc brakes on cars for that
    reason. Drum brakes have a variable response because they have self
    servo action, the harder you brake the greater the mechanical
    advantage of actuation. You must have hear of brake lock-up. This
    became so apparent in racing that the hazard to general driving was
    obvious. Although disc brakes dissipation power more poorly, their
    advantage in function far outweighs that problem. Just the same,
    you'll note that highway trucks still use drum brakes for their
    greater braking ability... and leave long dual skid marks on highways.

    I think you can visualize an increasing brake effect when you pull on
    the hand lever of your bicycle and how it would keep you from braking
    hard for fear of a lock-up, especially on wet roads. That is what the
    Delta brake did.

    If you look in the RBR archives, you'll find defenders of that brake
    and some rude comments.

    Jobst Brandt
     
  8. Dan Burkhart

    Dan Burkhart New Member

    Joined:
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    Sorry Jobst, the reason trucks still use drum brakes has nothing to do with superior performance and everything to do with reluctance to change. In Europe, heavy trucks have pretty much converted to discs for their lighter weight, lower maintenance, and, wait for it, superior stopping power. Here in North America, inter vehicle compatibility is a much greater issue than it is across the pond. Fleets with hundreds of power units and thousands of trailers need to have the flexibility to pull any of their trailers with any of their tractors. Mixing these brake types on multi unit vehicles creates an imbalance that is not only unsafe, but also illegal. Retrofitting fleets of this size is not feasable considering the fierce competitive forces these days, and attrition is not an option because of the reasons I have already put forth.
    Government regulation mandating stopping distances that only disc brakes can achieve is the only way they will ever come in to common usage, but most of the industry and goverment regulators alike remember all too well the fiasco that was the antilock provision of FMVSS 121. Here was a situation where an undeveloped technology was foisted on an unsuspecting public in the name of safety. People died as a result.
    Don't look for any such regulation soon.
    Dan Burkhart
     
  9. Dan Burkhart writes:

    >>>> Brakes must have a constant ratio of hand force to brake effect
    >>>> to be controllable.


    >>> Why? You've stated this as an axiom numerous times, but I don't
    >>> believe I've seen the reasoning behind it. I'd think that at
    >>> least small variations in MA wouldn't make a brake uncontrollable
    >>> (although probably harder to do so).


    >> If the MA is variable, you cannot dose braking such that you don't
    >> crash some time or other. Today we have disc brakes on cars for
    >> that reason. Drum brakes have a variable response because they
    >> have self servo action, the harder you brake the greater the
    >> mechanical advantage of actuation. You must have hear of brake
    >> lock-up. This became so apparent in racing that the hazard to
    >> general driving was obvious. Although disc brakes dissipation
    >> power more poorly, their advantage in function far outweighs that
    >> problem. Just the same, you'll note that highway trucks still use
    >> drum brakes for their greater braking ability... and leave long
    >> dual skid marks on highways.


    >> I think you can visualize an increasing brake effect when you pull
    >> on the hand lever of your bicycle and how it would keep you from
    >> braking hard for fear of a lock-up, especially on wet roads. That
    >> is what the Delta brake did.


    >> If you look in the RBR archives, you'll find defenders of that
    >> brake and some rude comments.


    > Sorry Jobst, the reason trucks still use drum brakes has nothing to
    > do with superior performance and everything to do with reluctance to
    > change. In Europe, heavy trucks have pretty much converted to discs
    > for their lighter weight, lower maintenance, and, wait for it,
    > superior stopping power. Here in North America, inter vehicle
    > compatibility is a much greater issue than it is across the pond.
    > Fleets with hundreds of power units and thousands of trailers need
    > to have the flexibility to pull any of their trailers with any of
    > their tractors. Mixing these brake types on multi unit vehicles
    > creates an imbalance that is not only unsafe, but also illegal.
    > Retrofitting fleets of this size is not feasable considering the
    > fierce competitive forces these days, and attrition is not an option
    > because of the reasons I have already put forth.


    I can tell you are truly sorry. Why the cynical intro? The point is
    that brakes with variable mechanical advantage are not readily
    controllable and that long truck skid marks on highways are there
    because their drum brakes have relatively poor control. As I
    mentioned previouslt on this subject, you won't find drum brakes on
    railroads, where skidding occurs more easily and has expensive
    effects. I also spent a few years in the development of early disc
    brakes and was involved in work to get discs to work as easily as the
    drum brakes they were to replace. Today most brakes are power
    assisted because disks require far greater contact force and not
    having the servo effect of drum brakes.

    Drums on trucks are far less expensive, less maintenance and have
    greater heat dissipation surface than discs.

    > Government regulation mandating stopping distances that only disc
    > brakes can achieve is the only way they will ever come in to common
    > usage, but most of the industry and goverment regulators alike remember
    > all too well the fiasco that was the antilock provision of FMVSS 121.
    > Here was a situation where an undeveloped technology was foisted on an
    > unsuspecting public in the name of safety. People died as a result.
    > Don't look for any such regulation soon.


    I think you are confusing the issues. Drum brakes have plenty of
    stopping power and good stopping distance. What they don't have is
    control that is essential in operating them at the transition between
    tracking and skidding, especially in curves and on wet roads. I don't
    contend that the Campagnolo Delta brake did not stop the bicycle, but
    that its varying mechanical advantage made it difficult to control.

    Jobst Brandt
     
  10. Dan Burkhart

    Dan Burkhart New Member

    Joined:
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    Long skid marks are often the result of normal brake application on a vehicle with unequally loaded axles. I should mention that anything I offer on this issue is based not on advanced theory, but on about 4 million miles of heavy vehicle operation over a span of 34 years, with a couple of years in the middle of that working as a driver trainer and certified air brake instructor.
    During that time, I had zero opportunity to assess disc brake performance for myself, so all I have is anecdotal from other drivers with the experience, manufacturers propaganda, and my own questionable reasoning.
    I don't pay too much attention to what goes on in that world anymore as I have moved on to other pursuits, but for a while there back in the 80s and early 90s, all the heavy vehicle brake systems manufacturers were busy developing their disc brakes in anticicpation of a wholesale industry changeover. Some small fleets tried them out, but they were only practical for an operation that used only their own dedicated equipment. It would mess them up if they ever had to lease a trailer.
    But anyway, I'm rambling now.
    For your claim of greater heat dissipation of drums, the brake makers counter that drums confined within the wheel are less able to dissipate heat than a vaned rotor that is more exposed to air flow. The drum brake is also more prone to fade when over used on long descents. The expansion of a heated drum means a loss of mechanical advantage as the chamber stroke, and consequently the angle of application between the push rod and slack adjuster changes. Expansion of a disc on the other hand reduces the application stroke.
    It seems though, that the industry has pretty much given up on the idea of converting to discs, and from anything I have read lately, most efforts are directed at imrovements and refinements to the drum based systems.
    Dan Burkhart
     
  11. Dan Burkhart writes:

    >>>>>> Brakes must have a constant ratio of hand force to brake effect
    >>>>>> to be controllable.


    >>>>> Why? You've stated this as an axiom numerous times, but I don't
    >>>>> believe I've seen the reasoning behind it. I'd think that at
    >>>>> least small variations in MA wouldn't make a brake
    >>>>> uncontrollable (although probably harder to do so).


    >>>> If the MA is variable, you cannot dose braking such that you
    >>>> don't crash some time or other. Today we have disc brakes on
    >>>> cars for that reason. Drum brakes have a variable response
    >>>> because they have self servo action, the harder you brake the
    >>>> greater the mechanical advantage of actuation. You must have hear
    >>>> of brake lock-up. This became so apparent in racing that the
    >>>> hazard to general driving was obvious. Although disc brakes
    >>>> dissipation power more poorly, their advantage in function far
    >>>> outweighs that problem. Just the same, you'll note that highway
    >>>> trucks still use drum brakes for their greater braking
    >>>> ability... and leave long dual skid marks on highways.


    >>>> I think you can visualize an increasing brake effect when you
    >>>> pull on the hand lever of your bicycle and how it would keep you
    >>>> from braking hard for fear of a lock-up, especially on wet roads.
    >>>> That is what the Delta brake did.


    >>>> If you look in the RBR archives, you'll find defenders of that
    >>>> brake and some rude comments.


    >>> Sorry Jobst, the reason trucks still use drum brakes has nothing
    >>> to do with superior performance and everything to do with
    >>> reluctance to change. In Europe, heavy trucks have pretty much
    >>> converted to discs for their lighter weight, lower maintenance,
    >>> and, wait for it, superior stopping power. Here in North America,
    >>> inter vehicle compatibility is a much greater issue than it is
    >>> across the pond. Fleets with hundreds of power units and
    >>> thousands of trailers need to have the flexibility to pull any of
    >>> their trailers with any of their tractors. Mixing these brake
    >>> types on multi unit vehicles creates an imbalance that is not only
    >>> unsafe, but also illegal. Retrofitting fleets of this size is not
    >>> feasable considering the fierce competitive forces these days, and
    >>> attrition is not an option because of the reasons I have already
    >>> put forth.


    >> I can tell you are truly sorry. Why the cynical intro? The point
    >> is that brakes with variable mechanical advantage are not readily
    >> controllable and that long truck skid marks on highways are there
    >> because their drum brakes have relatively poor control. As I
    >> mentioned previously on this subject, you won't find drum brakes on
    >> railroads, where skidding occurs more easily and has expensive
    >> effects. I also spent a few years in the development of early disc
    >> brakes and was involved in work to get discs to work as easily as
    >> the drum brakes they were to replace. Today most brakes are power
    >> assisted because disks require far greater contact force and not
    >> having the servo effect of drum brakes.


    >> Drums on trucks are far less expensive, less maintenance and have
    >> greater heat dissipation surface than discs.


    >>> Government regulation mandating stopping distances that only disc
    >>> brakes can achieve is the only way they will ever come in to
    >>> common usage, but most of the industry and goverment regulators
    >>> alike remember all too well the fiasco that was the antilock
    >>> provision of FMVSS 121. Here was a situation where an undeveloped
    >>> technology was foisted on an unsuspecting public in the name of
    >>> safety. People died as a result. Don't look for any such
    >>> regulation soon.


    >> I think you are confusing the issues. Drum brakes have plenty of
    >> stopping power and good stopping distance. What they don't have is
    >> control that is essential in operating them at the transition
    >> between tracking and skidding, especially in curves and on wet
    >> roads. I don't contend that the Campagnolo Delta brake did not
    >> stop the bicycle, but that its varying mechanical advantage made it
    >> difficult to control.


    > Long skid marks are often the result of normal brake application on
    > a vehicle with unequally loaded axles. I should mention that
    > anything I offer on this issue is based not on advanced theory, but
    > on about 4 million miles of heavy vehicle operation over a span of
    > 34 years, with a couple of years in the middle of that working as a
    > driver trainer and certified air brake instructor.


    When you have an empty trailer, you don't need to make heavy brake
    applications, these are loaded trucks that cause these skids. I've
    watched the white smoke from the tires as they brake on highways.

    > During that time, I had zero opportunity to assess disc brake
    > performance for myself, so all I have is anecdotal from other
    > drivers with the experience, manufacturers propaganda, and my own
    > questionable reasoning.


    Discs are not easily cooled for high load applications. That is why
    railway discs have mass to store the entire brake application and then
    cool off before the next time used.

    > I don't pay too much attention to what goes on in that world anymore
    > as I have moved on to other pursuits, but for a while there back in
    > the 80s and early 90s, all the heavy vehicle brake systems
    > manufacturers were busy developing their disc brakes in
    > anticicpation of a wholesale industry changeover. Some small fleets
    > tried them out, but they were only practical for an operation that
    > used only their own dedicated equipment. It would mess them up if
    > they ever had to lease a trailer. But anyway, I'm rambling now.


    Well that fell in the water when the physical and economic realities
    came to bear. I doubt that you will see widespread use of discs on
    heavy haul trailers. The complexities are not worth the effort.
    That, however has little to do with variable ratio bicycle brakes as
    you take this ever farther away from the issue.

    > For your claim of greater heat dissipation of drums, the brake
    > makers counter that drums confined within the wheel are less able to
    > dissipate heat than a vaned rotor that is more exposed to air
    > flow. The drum brake is also more prone to fade when over used on
    > long descents. The expansion of a heated drum means a loss of
    > mechanical advantage as the chamber stroke, and consequently the
    > angle of application between the push rod and slack adjuster
    > changes. Expansion of a disc on the other hand reduces the
    > application stroke.


    Drums are not confined to the inside of the wheel, you can see them
    exposed when you follow such a vehicle. Besides, this is not a still
    air zone as one is led to believe by all the wheel vents that
    passenger cars have. All they do is expose how much brake dust can
    accumulate on wheels. There is plenty of ventilation for those brakes
    without the aerodynamic looking wheel designs.

    > It seems though, that the industry has pretty much given up on the
    > idea of converting to discs, and from anything I have read lately,
    > most efforts are directed at imrovements and refinements to the drum
    > based systems.


    Yes???

    Jobst Brandt
     
  12. Dan Burkhart

    Dan Burkhart New Member

    Joined:
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    I'll keep going as far away from the issue at hand as you care to take it. I have crawled around under enough trucks, done enough pre-trip inspections and hands on brake adjustments to confidently state that, on a dual wheel application, the brake drum is almost totally enclosed within the inner wheel. The current (gradual) shift towards wide base single tires offers an improvement in this situation. Ventilation is a huge issue here.
    Railway brakes? Not much advancement there since the stage coach brake design they were based on. However, in this case, the simpler the better. Application forces are linear, and, as you say, heating the wheel is not a problem.( Except for traction wheels.)
    Dan
     
  13. Dan Burkhart writes:

    > I'll keep going as far away from the issue at hand as you care to
    > take it. I have crawled around under enough trucks, done enough
    > pre-trip inspections and hands on brake adjustments to confidently
    > state that, on a dual wheel application, the brake drum is almost
    > totally enclosed within the inner wheel. The current (gradual) shift
    > towards wide base single tires offers an improvement in this
    > situation. Ventilation is a huge issue here.


    > Railway brakes? Not much advancement there since the stage coach
    > brake design they were based on. However, in this case, the simpler
    > the better. Application forces are linear, and, as you say, heating
    > the wheel is not a problem.( Except for traction wheels.) Dan


    Railway disc brakes are as up to date as any brakes on cars and
    trucks. That freight trains use wheel shoe brakes is because stopping
    a freight train is a singular event and not done with great
    acceleration. Today, their brakes are pretty much adjuncts to the
    dynamic braking of locomotives, used as a hand brake on a car and an
    emergency brake. It is an entirely different task than a highway
    vehicle that needs to alter speed often for the flow of traffic.
    Passenger trains, in contrast use only discs and do plenty of
    stopping. I think you should look at these brakes and see how large
    and advanced in design they are.

    Back to truck brakes, so where do you put discs if the drums are
    entirely enclosed by dual wheels? I don't see the bearing of this on
    whether drum brakes are readily controlled in brake applications.

    Jobst Brandt
     
  14. Jasper Janssen wrote:
    > On 14 Apr 2006 04:50:57 GMT, [email protected] wrote:
    >
    > >Brakes must have a constant ratio of hand force to brake effect to be
    > >controllable.

    >
    > Why? You've stated this as an axiom numerous times, but I don't believe
    > I've seen the reasoning behind it. I'd think that at least small
    > variations in MA wouldn't make a brake uncontrollable (although probably
    > harder to do so).
    >
    >


    Perhaps it's a matter of what you're used to. I've been using Deltas on
    one bike for 16 years and I find the "progressive" action quite
    pleasant , giving excellent modulation. OTOH, I find "modern", dual
    pivot brakes devoid of feel, with a kind of "on/off switch" action. In
    that regard, I much prefer older, single pivot sidepulls much better
    than dual pivots.

    IMO, of course. YMMV, etc., etc., etc.
     
  15. On 15 Apr 2006 00:08:55 GMT, [email protected] wrote:

    >I think you are confusing the issues. Drum brakes have plenty of
    >stopping power and good stopping distance. What they don't have is
    >control that is essential in operating them at the transition between
    >tracking and skidding, especially in curves and on wet roads. I don't
    >contend that the Campagnolo Delta brake did not stop the bicycle, but
    >that its varying mechanical advantage made it difficult to control.


    Doesn't a brake that routinely skids the wheels have bad stopping power?
    If your wheels are skidding you're not stopping with anywhere near the
    theoretical maximum.. why ABS was invented.

    Jasper
     
  16. Jasper Janssen <[email protected]> wrote:
    > If your wheels are skidding you're not stopping with anywhere near
    > the theoretical maximum.. why ABS was invented.


    ABS was invented to allow control which is lost once the vehicle
    skids, not to improve stopping power.

    --
    MfG/Best regards
    helmut springer
     
  17. On 14 Apr 2006 23:01:36 GMT, [email protected] wrote:

    >If the MA is variable, you cannot dose braking such that you don't
    >crash some time or other. Today we have disc brakes on cars for that
    >reason. Drum brakes have a variable response because they have self
    >servo action, the harder you brake the greater the mechanical
    >advantage of actuation. You must have hear of brake lock-up. This
    >became so apparent in racing that the hazard to general driving was
    >obvious. Although disc brakes dissipation power more poorly, their
    >advantage in function far outweighs that problem. Just the same,
    >you'll note that highway trucks still use drum brakes for their
    >greater braking ability... and leave long dual skid marks on highways.
    >
    >I think you can visualize an increasing brake effect when you pull on
    >the hand lever of your bicycle and how it would keep you from braking
    >hard for fear of a lock-up, especially on wet roads. That is what the
    >Delta brake did.


    I can see how it would be bad to have a point where MA goes to infinity,
    or too high, either as designed or after wear and/or flex are taken into
    account, but I still don't see how a hypothetical brake with MA varying
    from, say, 8 to 2 or 4 to 2 over the stroke which is ever seen in use
    (including flex, wear, and Chalo-style or tandem riders which take an
    awful lot of force to reach .6g).

    If brake pad wear was not an issue, I could see a (again hypothetical)
    brake which would move the shoes 1 or 2 cm with the first 5 mm of lever
    travel and then go to standard MA for 1 mm away from the rim to the rest
    of the stroke -- with advantages in pad clearance while changing wheels
    and continuing with bent wheels. I very much doubt those advantages would
    be worth the problems, though.

    Jasper
     
  18. G.T.

    G.T. Guest

    Helmut Springer wrote:
    > Jasper Janssen <[email protected]> wrote:
    >
    >>If your wheels are skidding you're not stopping with anywhere near
    >>the theoretical maximum.. why ABS was invented.

    >
    >
    > ABS was invented to allow control which is lost once the vehicle
    > skids, not to improve stopping power.
    >


    Not stopping power but stopping distance. And during a similar
    discussion on rec.photo.digital.slr-systems, where it was quite
    off-topic, I found several documents where the goal was to reduce
    stopping distance during panic stops.

    Greg

    --
    "All my time I spent in heaven
    Revelries of dance and wine
    Waking to the sound of laughter
    Up I'd rise and kiss the sky" - The Mekons
     
  19. G.T. <[email protected]> wrote:
    > Not stopping power but stopping distance. And during a similar
    > discussion on rec.photo.digital.slr-systems, where it was quite
    > off-topic, I found several documents where the goal was to reduce
    > stopping distance during panic stops.


    References? Bosch happens to have driven that for cars, and their
    goal was control...


    --
    MfG/Best regards
    helmut springer
     
  20. G.T.

    G.T. Guest

    Helmut Springer wrote:
    > G.T. <[email protected]> wrote:
    >
    >>Not stopping power but stopping distance. And during a similar
    >>discussion on rec.photo.digital.slr-systems, where it was quite
    >>off-topic, I found several documents where the goal was to reduce
    >>stopping distance during panic stops.

    >
    >
    > References? Bosch happens to have driven that for cars, and their
    > goal was control...
    >


    Actually my part of the discussion was just about stopping distance so
    I'll back off on the goals of the original designers. There never was a
    consensus as to the goals but Bosch was mentioned.

    This is what one other poster said but I never bothered to fact check it
    (and below this are quotes from studies about stopping distances):

    "This is *one* of the reasons it was invented. It was actually
    developed first for aircraft, an early version being Dunlop's Maxaret
    system used in the 1950's to reduce the chance of aquaplaning during
    landings on wet runways.

    Aquaplaning leads to *both* loss of directional control *and*
    significant lowering of retardation effects of the brakes. Although
    you can argue that directional control is more important, the system
    was developed to solve a problem that comprises of both aspects.

    So, no, it wasn't developed just to reduce stopping distances, neither
    was it developed *just* to maintain directional control. It was
    developed to allow aircraft to attempt landings on a runway they
    usually couldn't do due to heavy rain / surface water conditions.

    The first cars to have ABS (The British Jenson FF GT production car -
    mid 60's, which was a first in two respects: first all wheel drive and
    first ABS) used a slightly enhanced version of the Dunlop Maxaret
    system too. But being a bulky, unreliable and expensive addon it then
    went out of fashion for 20 years until modern electronic versions made
    it a feasible option again.

    Drivers of the Jenson FF have noted that the ABS could be overridden
    by stamping hard on the brakes, due to it's mechanical nature - so
    long as you are expecting the fibrating-foot sensation. So, it's not
    much use in a panic-brake scenario.

    Dunlop & Jenson are both British companies, located at the time very
    close to each other. Germany's Bosch had apparently been developing
    ABS since the 30's but wasn't until 1978 the first Merc's got them."

    ===================================================================

    Stopping distance:

    "During 1988-91, NHTSA performed two extensive series of stopping tests
    involving vehicles with four-wheel ABS or RWAL, on various road
    surfaces. The tests confirmed that four-wheel ABS was highly effective
    in preventing yawing and allowing the driver to steer the car during
    panic braking. Stopping distances decreased substantially with
    four-wheel ABS on wet surfaces, but decreased only slightly on dry
    pavement and increased on gravel."

    From the US Department of Transport:

    "ABS may shorten stopping distances on wet or slippery roads and most
    systems may shorten stopping distances on dry roads."
    http://www.nhtsa.dot.gov/cars/problems/Equipment/absbrakes/page1.html

    From a small US car company called General Motors:

    "Q. Does ABS reduce stopping distances?

    A. Yes, in braking situations where the wheels on a non-ABS
    equipped vehicle would lock up, ABS will generally provide shorter
    controlled stopping distance. The amount of improvement in stopping
    distance depends on many factors, including the road surface, severity
    of braking, initial vehicle speed, etc."

    http://www.gmfleet.com/us/products/specialized/police/safety/abs.html#2

    An educational site:

    "Stopping distance on many slippery surfaces will also increase with
    locked wheels. Four-wheel ABS prevents wheel lock-up in situations in
    which the wheels might normally lock, such as on slippery roads."
    http://www.abs-education.org/faqs/faqindex.htm

    A forensic company:

    "In general, the real benefits of ABS are realized in straight line,
    emergency braking. Under these conditions, ABS installations provide
    full steering control, complete vehicle stability and shorter stopping
    distances."
    http://www.waltersforensic.com/articles/accident_reconstruction/vol2-...

    The AAA:

    "Under most conditions, a vehicle with a good anti-lock brake system
    can stop in a slightly shorter distance than an average driver could
    accomplish in the same vehicle without ABS"
    http://www.aaafoundation.org/resources/index.cfm?button=abs#stop


    --
    "All my time I spent in heaven
    Revelries of dance and wine
    Waking to the sound of laughter
    Up I'd rise and kiss the sky" - The Mekons
     
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