Pedersen self energizing brakes.

wrote:

Chalo Colina writes:

They worked well and proved to be safer for me (because they gave me
the option of quick stops) than any other brake I used during the
same span of time.

For trucks, this may work, but if you are riding in mountains with
braking descents, you are engaging in a dangerous gamble because you
cannot predict what brake effect will result from your grip on the
lever. Do you descend curvy mountain roads. I was thinking of this
as I descended the Sierra this weekend on Ebbetts and Sonora Passes
where banking into turns at high speed while braking would be
disastrous with a servo brake.

I submit that if the response curve of your brakes is a factor in being
able to stay upright and on the road, then you have allowed too small a
safety margin. A powerful brake helps me (and I speak for myself here)
to maintain a decent safety margin in such conditions, since I can not
only arrest my acceleration but also reduce my speed, quickly if
necessary.

Riding on winding roads at 50mph is dangerous only if you engage in it.
But on the 10% to 20% grades I am likely to encounter on a daily
basis, a weak brake like the Record sidepull is a menace even at
walking speed, because I can easily encounter circumstances where my
acceleration due to slope exceeds my deceleration from the brakes.
This is my experience, and I don't think it's typical-- but I do think
it's an exaggerated variation of what many riders face. It's easier to
ride within safe limits than it is to cope with circumstances where
your brakes can't slow you down.

Banking steeply at high speed on narrow roads is placing a great deal
of trust in many different parts of your equipment, as well as external
circumstances beyond your control. It's your choice to do it or not,
but it does not constitute normal riding, and it seems to me to be a
bit backwards to fault a brake for applying braking force when you've
imposed a situation where braking force is almost unusable.

This isn't about brake force but rather control. The way you say that
I see only a truck braking in a straight line. I'm sure you have seen
the picture of descending while leaning at speed with two fingers on
both brakes. It is there that servo brakes are out of place, as was
the Campagnolo Delta brake that was not as hazardous as a servo brake.

Right. And any brakes at all are out of place at the velodrome. It
does not follow that all riders should use weak brakes (or no brakes)
because of this.

For every track racer at the 'drome or unladen cycle tourist flying
down alpine passes, there is an overweight guy riding his bike in city
traffic with groceries in the panniers and his kid in a trailer.
Should he be using brakes that are designed not to provide too much
stopping force?

Heck, for every track racer or supported alpine tourist, there is a
couple on a tandem carrying more speed than either one of them would be
capable of producing. I expect that there are many more situations
where a stronger brake would be of benefit than where a subtler brake
would be an advantage.

Stopping power and control are separate concepts. The servo brake has
miserable control.

Having spent years on SE brakes, I would not call their control
"miserable". It is, as I have said, more abrupt and less consistent
than the best conventional brakes. But it would be feasible to ride in
such a way that one could use even a brake that was either fully on or
off. This would be preferable to being able to accelerate downhill
with the levers pulled all the way to the bars. I can do this on some
steep slopes with my drum-braked bikes-- and those brakes are more
powerful than many caliper brakes I have tried. One of my friends has
commented while we were riding on how effective these same drum brakes
seem to be, but her basis of comparison is her (well-maintained)
vintage Modolo caliper brakes. And her GVW is probably 40% of mine.

Don't use them unless you don't descend mountain roads...

By that measure, they should be appropriate for almost every bicycle
rider, almost all the time. Choosing your brakes based on what works
best when bombing mountain passes is like choosing your regular
footwear based on how it performs for dancing en pointe.

Chalo Colina

In article . com,
"Chalo" wrote:

Stopping power and control are separate concepts. The servo brake has
miserable control.

Having spent years on SE brakes, I would not call their control
"miserable". It is, as I have said, more abrupt and less consistent
than the best conventional brakes. But it would be feasible to ride in
such a way that one could use even a brake that was either fully on or
off. This would be preferable to being able to accelerate downhill
with the levers pulled all the way to the bars. I can do this on some
steep slopes with my drum-braked bikes-- and those brakes are more
powerful than many caliper brakes I have tried. One of my friends has
commented while we were riding on how effective these same drum brakes
seem to be, but her basis of comparison is her (well-maintained)
vintage Modolo caliper brakes. And her GVW is probably 40% of mine.

Don't use them unless you don't descend mountain roads...

By that measure, they should be appropriate for almost every bicycle
rider, almost all the time. Choosing your brakes based on what works
best when bombing mountain passes is like choosing your regular
footwear based on how it performs for dancing en pointe.

I used the SE brakes on my mountain bike some years ago (rear was a
Suntour, front was a Scott). Because of the flexy seatstays, the back
brake was limited in how much braking force I could apply. However, I
had to detune the front brake to make it more controllable (i.e.,
lengthen the straddle cable). Otherwise, it was too easy to lock up the
front brake. After reading Jobst's rants about SE brakes having poor
controllability, I switched to conventional cantis and didn't really
notice the lack of power over the SE brakes. Now a days, V brakes are
far superior to either conventional cantis or SE brakes that I haven't
looked back. Setting up brake pads with V brakes is so much easier and
that alone is worth the switch.

--
Mike DeMicco

Mike DeMicco wrote:

Now a days, V brakes are
far superior to either conventional cantis or SE brakes that I haven't
looked back. Setting up brake pads with V brakes is so much easier and
that alone is worth the switch.

Linear-pull brakes have the obvious and noteworthy drawback that they
are incompatible with levers intended for any other kind of brake.
From what I can tell, there is no completely satisfactory way to use
them with drop bars or with any handlebar that is larger than 22.2mm in
diameter.

In every other functional respect, they do seem to have improved upon
cantilever brakes.

Chalo Colina

Chalo wrote:

Linear-pull brakes have the obvious and noteworthy drawback that they
are incompatible with levers intended for any other kind of brake.
From what I can tell, there is no completely satisfactory way to use
them with drop bars or with any handlebar that is larger than 22.2mm
in diameter.

What about those cam adaptors (V-Daptor?)?

In every other functional respect, they do seem to have improved upon
cantilever brakes.

I actually prefer the old style -- better modulation, better tire clearance. I
still have them on my mountain bike. But if you need the power, linear pull
brakes are the way to go. They're easier to set up too.

Matt O.

Chalo Colina writes:

They worked well and proved to be safer for me (because they gave
me the option of quick stops) than any other brake I used during
the same span of time.

For trucks, this may work, but if you are riding in mountains with
braking descents, you are engaging in a dangerous gamble because
you cannot predict what brake effect will result from your grip on
the lever. Do you descend curvy mountain roads. I was thinking of
this as I descended the Sierra this weekend on Ebbetts and Sonora
Passes where banking into turns at high speed while braking would
be disastrous with a servo brake.

I submit that if the response curve of your brakes is a factor in
being able to stay upright and on the road, then you have allowed
too small a safety margin. A powerful brake helps me (and I speak
for myself here) to maintain a decent safety margin in such
conditions, since I can not only arrest my acceleration but also
reduce my speed, quickly if necessary.

THis sound much like a helmet war response. The way you say that it
rings like "anyone who rides faster than I, is crazy." And "You
should have seen them, descending like madmen!" I think we've all
hear these characterizations and passed over their meaning.

In essence, you are claiming that brake technology is off base and
that the development of linear brake response is not useful. THis is
typical of the bicycle industry, where apparently different physics
and control theory work.

Riding on winding roads at 50mph is dangerous only if you engage in
it. But on the 10% to 20% grades I am likely to encounter on a
daily basis, a weak brake like the Record sidepull is a menace even
at walking speed, because I can easily encounter circumstances where
my acceleration due to slope exceeds my deceleration from the
brakes. This is my experience, and I don't think it's typical-- but
I do think it's an exaggerated variation of what many riders face.
It's easier to ride within safe limits than it is to cope with
circumstances where your brakes can't slow you down.

Speak for yourself. The brakes I ride have served well and have
brought me down more fascinating mountain roads than most riders have
seen, much less ridden.

Banking steeply at high speed on narrow roads is placing a great
deal of trust in many different parts of your equipment, as well as
external circumstances beyond your control. It's your choice to do
it or not, but it does not constitute normal riding, and it seems to
me to be a bit backwards to fault a brake for applying braking force
when you've imposed a situation where braking force is almost
unusable.

Let's talk about brakes and brake response instead of what you think
is a safe speed and gradient for bicycling. I don't see this has to
progress into personal insults or critique of riding style. The
concepts are simple and can be considered. I mentioned some of the
conditions under which brakes make a difference. Surely if we never
brake in a curve or exceed 15mph, we wouldn't care much about linear
or non-linear brake response.

This isn't about brake force but rather control. The way you say
that I see only a truck braking in a straight line. I'm sure you
have seen the picture of descending while leaning at speed with two
fingers on both brakes. It is there that servo brakes are out of
place, as was the Campagnolo Delta brake that was not as hazardous
as a servo brake.

Right. And any brakes at all are out of place at the velodrome. It
does not follow that all riders should use weak brakes (or no
brakes) because of this.

To what sort of weak brakes are you alluding? I'm unclear on what are
you talking about? This doesn't make sense. What does a velodrome
have to do with brake linearity?

For every track racer at the 'drome or unladen cycle tourist flying
down alpine passes, there is an overweight guy riding his bike in
city traffic with groceries in the panniers and his kid in a
trailer. Should he be using brakes that are designed not to provide
too much stopping force?

This is getting weirder and weirder. Please let's get back to brakes.

Heck, for every track racer or supported alpine tourist, there is a
couple on a tandem carrying more speed than either one of them would
be capable of producing. I expect that there are many more
situations where a stronger brake would be of benefit than where a
subtler brake would be an advantage.

What do you mean by a "stronger brake" and a "subtler brake"? And
what do track racers have to do with brakes. I can't tell whether you
are serious or not about this whole subject by the way this is
drifting.

Stopping power and control are separate concepts. The servo brake
has miserable control.

Having spent years on SE brakes, I would not call their control
"miserable". It is, as I have said, more abrupt and less consistent
than the best conventional brakes. But it would be feasible to ride
in such a way that one could use even a brake that was either fully
on or off. This would be preferable to being able to accelerate
downhill with the levers pulled all the way to the bars. I can do
this on some steep slopes with my drum-braked bikes-- and those
brakes are more powerful than many caliper brakes I have tried. One
of my friends has commented while we were riding on how effective
these same drum brakes seem to be, but her basis of comparison is
her (well-maintained) vintage Modolo caliper brakes. And her GVW is
probably 40% of mine.

So what does this mean with respect to brake design, a bicycle not
having power to implement power brakes as cars have we have limited
choices. Servo brakes have been tried in all sorts of vehicles and
have failed the test of time.a

Don't use them unless you don't descend mountain roads...

By that measure, they should be appropriate for almost every bicycle
rider, almost all the time. Choosing your brakes based on what
works best when bombing mountain passes is like choosing your
regular footwear based on how it performs for dancing en pointe.

That may be more true than it at first seems. I notice that many
riders find no problem with colored tires that have miserable wet
traction. This seems to support the suspicion that most riders don't
lean into corners enough to put their tire traction to the test.
Meanwhile they write endlessly about hydroplaning on slicks and tires
slipping from pedaling torque. This also doesn't add up.

Just the same, as you see, the Campagnolo Delta brake died for lack
of funtion and that was for racers and sports tourists to descend
mountain roads.

Matt O'Toole wrote:

Chalo wrote:

From what I can tell, there is no completely satisfactory way to use
them with drop bars or with any handlebar that is larger than 22.2mm
in diameter.

What about those cam adaptors (V-Daptor?)?

I have never used a cable multiplier that did not add enough friction
and mush to the system to basically negate the advantages of a
linear-pull brake. Likewise, the Dia-Compe 287-V does not seem to pull
enough cable to be a straightforward replacement for true LP brake
levers.

I actually prefer the old style -- better modulation, better tire clearance.

When I set cantis up to deliver similar power to a linear-pull brake,
they seem at least as touchy as linear-pulls, and are much likelier to
squeal or honk. They also must be set much closer to the rim.

LP brakes vary a lot in the amount of tire clearance they provide.
Some of them are challenged by a 2.1" tire, others accept 2.35" tires
without a problem. Brake stud placement has an effect on this.

Chalo Colina

On 6 Jun 2005 12:31:09 -0700, "Dirtroadie" wrote:

Once the wedge is driven (and the system is in equilibrium) how much
have we increased force P? We haven't - P must still equal 2*D since
the only force on the right end of the lever is still the force D.

A braking bicycle wheel/brake system is *not* in equilibrium. For ****'s
sake.

Jasper

On 6 Jun 2005 14:10:51 -0700, "Dirtroadie" wrote:

OK when a brake is actuated it "pushes" on the rim. According to
Newton, the rim must also be "pushing" back i.e. trying to move the pad
away from the rim.
The quantity of these balanced forces is reflected in the tension on
the brake cable.

No. The tension in the brake cable is equal to one force, not to the
balance of them. In equilibrium (which requires a *stopped bike*, not a
stopping bike), if you remove all the return springs and pull on the
brakes, you can increase brake cable tension from nothing to infinity
(modulo material strengths) simply by pulling on the brake lever harder.
The tension isn't the sum of the forces, which is zero (keep in mind this
is a *vector* sum, not an arithmetical sum).

Now when we add the additional force of the "self
energizing" effect, where does that additonal force go if not into
cable tension? Of course that is in a system where we are assuming
non-real things such as a friction-free system.

Inasmuch as the additional force affects brake cable tension, it *reduces*
it.


Jasper

Jasper Janssen wrote:

No. The tension in the brake cable is equal to one force, not to the
balance of them. In equilibrium (which requires a *stopped bike*, not a
stopping bike),

For the sake of this discussion, it is the cantilever arm which IS
stopped, forget the rest of the bike.

if you remove all the return springs and pull on the
brakes, you can increase brake cable tension from nothing to infinity
(modulo material strengths) simply by pulling on the brake lever harder.

Yes. And that tension must be balanced somehow or it can't be created
in the first place. If the brake pad is not, for example, braced
against the rim, one cannot create this "infinite" tension you
describe. Try removing a wheel from a bike and then squeezing the
corresponding brake lever - squeeze it very hard. How much tension can
you sense at the brake lever?

The tension isn't the sum of the forces, which is zero (keep in mind this
is a *vector* sum, not an arithmetical sum).
I agree that the sum of the forces is zero. That was exactly my point.
That is what I am referring to as "equilibrium."
http://www.physicsclassroom.com/Clas...ors/U3L3c.html

Now when we add the additional force of the "self
energizing" effect, where does that additonal force go if not into
cable tension? Of course that is in a system where we are assuming
non-real things such as a friction-free system.

Inasmuch as the additional force affects brake cable tension, it *reduces*
it.

Oh?

DR

Jasper Janssen wrote:

A braking bicycle wheel/brake system is *not* in equilibrium. For ****'s
sake.

Thank you for your eloquent, articulate and insightful analysis.