Andre Jute wrote:

Those brakes aren't dodgy, Don, they're hyper-competent; what I forgot
to add is that they have a built-in modulator. They stop the one-
eighth of a ton of me and the bike and light touring gear from thirty
kph in 11 feet. I know, because I chewed up a pair of tyres while I
practiced that one to perfection. But I agree with you, for casual use
those roller brakes are overkill.

A fat man on a granny bike braking at over 1g!
Don't the laws of physics apply in Eire these days?

--
Eiron.

On Sat, 08 Sep 2007 08:42:58 +0100, Eiron wrote:

Andre Jute wrote:

Those brakes aren't dodgy, Don, they're hyper-competent; what I forgot
to add is that they have a built-in modulator. They stop the one-
eighth of a ton of me and the bike and light touring gear from thirty
kph in 11 feet. I know, because I chewed up a pair of tyres while I
practiced that one to perfection. But I agree with you, for casual use
those roller brakes are overkill.

A fat man on a granny bike braking at over 1g!
Don't the laws of physics apply in Eire these days?

Quite so. That comes out at 1.05g. Centre of mass combined with
wheelbase tell us that he performed the last 8 feet of that stop flat
on his face in the road. But that is a perfectly legitimate way of
stopping your bike.

Anyone who wants to do the sum the easy way just pop this

(30 kph)^2 / (2 * 11 ft) in g

into Google. I rarely use an other calculator these days.

d

--
Pearce Consulting
http://www.pearce.uk.com

Don Pearce wrote:
On Sat, 08 Sep 2007 08:42:58 +0100, Eiron wrote:

Andre Jute wrote:

Those brakes aren't dodgy, Don, they're hyper-competent; what I forgot
to add is that they have a built-in modulator. They stop the one-
eighth of a ton of me and the bike and light touring gear from thirty
kph in 11 feet. I know, because I chewed up a pair of tyres while I
practiced that one to perfection. But I agree with you, for casual use
those roller brakes are overkill.
A fat man on a granny bike braking at over 1g!
Don't the laws of physics apply in Eire these days?

Quite so. That comes out at 1.05g. Centre of mass combined with
wheelbase tell us that he performed the last 8 feet of that stop flat
on his face in the road. But that is a perfectly legitimate way of
stopping your bike.

I just tried a normal stop from 20mph on decent tarmac. It took 12 yards
which averages 0.37g, and the back wheel was hopping about. I expect 0.5g
would be a reasonable maximum if I moved down and back, or a bit more if
I wasn't so fat. Perhaps André meant 11 yards, or perhaps he's just won
another thousand euros after betting that someone would point out the
deliberate error. :-)

--
Eiron.

On Sat, 08 Sep 2007 13:10:34 +0100, Eiron wrote:

Don Pearce wrote:
On Sat, 08 Sep 2007 08:42:58 +0100, Eiron wrote:

Andre Jute wrote:

Those brakes aren't dodgy, Don, they're hyper-competent; what I forgot
to add is that they have a built-in modulator. They stop the one-
eighth of a ton of me and the bike and light touring gear from thirty
kph in 11 feet. I know, because I chewed up a pair of tyres while I
practiced that one to perfection. But I agree with you, for casual use
those roller brakes are overkill.
A fat man on a granny bike braking at over 1g!
Don't the laws of physics apply in Eire these days?

Quite so. That comes out at 1.05g. Centre of mass combined with
wheelbase tell us that he performed the last 8 feet of that stop flat
on his face in the road. But that is a perfectly legitimate way of
stopping your bike.

I just tried a normal stop from 20mph on decent tarmac. It took 12 yards
which averages 0.37g, and the back wheel was hopping about. I expect 0.5g
would be a reasonable maximum if I moved down and back, or a bit more if
I wasn't so fat. Perhaps André meant 11 yards, or perhaps he's just won
another thousand euros after betting that someone would point out the
deliberate error. :-)

I'd be very surprised if you could ever reach 0.5g on a pushbike,
unless it is a recumbent. You just sit too tall with respect to the
front wheel position. If your back wheel was hopping, you had reached
the limit, and it is really difficult to do anything but move your
body forwards under braking - there is nothing to brace against.

So maybe he did mean 11 yards, but that would be a shame because it
would mean those fancy brakes couldn't actually match a normal set.

d

--
Pearce Consulting
http://www.pearce.uk.com

On Sep 8, 1:22 am, (Don Pearce) wrote:
On Sat, 08 Sep 2007 08:42:58 +0100, Eiron wrote:
Andre Jute wrote:

Those brakes aren't dodgy, Don, they're hyper-competent; what I forgot
to add is that they have a built-in modulator. They stop the one-
eighth of a ton of me and the bike and light touring gear from thirty
kph in 11 feet. I know, because I chewed up a pair of tyres while I
practiced that one to perfection. But I agree with you, for casual use
those roller brakes are overkill.

A fat man on a granny bike braking at over 1g!
Don't the laws of physics apply in Eire these days?

Quite so. That comes out at 1.05g. Centre of mass combined with
wheelbase tell us that he performed the last 8 feet of that stop flat
on his face in the road. But that is a perfectly legitimate way of
stopping your bike.

Anyone who wants to do the sum the easy way just pop this

(30 kph)^2 / (2 * 11 ft) in g

What's this nonsense, Don, a wiki written by you and the equally
useless Eiron? Didn't they teach you in tech school to use compatible
units? You're mixing Imperial and Metric measures hand over orange.
Here is a reliable authority on the subject:

"The maximum braking force that can be applied to a vehicle through
its wheels -- the mass of air having its own retarding force -- is
limited by the friction between the tire and the road, and is equal to
the weight of the vehicle multiplied by the coefficient of friction.
On a dry pavement, this coefficient could be as high as 1; with a
coefficient of unity, retardation would be 1g or 32.2ft/s^2 and the
stopping distance in feet would be V^2/29.9 where V is the speed in
mph. I must stress though that this is on an ideal surface such as
does not exist outside a test facility..."
(p98, Designing and Building Special Cars, by Andre Jute, Batsford,
London 1985)

That math is properly and correctly developed elsewhere in this
thread, where you can go find it.

into Google. I rarely use an other calculator these days.

You should learn how and you won't perpetrae further ****ups like in
this post.

Andre Jute
Our legislators managed to criminalize fox-hunting and smoking; when
they will get off their collective fat backside and criminalize
negative feedback? It is clearly consumed only by thickoes.

On Sat, 08 Sep 2007 17:44:24 -0700, Andre Jute
wrote:

On Sep 8, 1:22 am, (Don Pearce) wrote:
On Sat, 08 Sep 2007 08:42:58 +0100, Eiron wrote:
Andre Jute wrote:

Those brakes aren't dodgy, Don, they're hyper-competent; what I forgot
to add is that they have a built-in modulator. They stop the one-
eighth of a ton of me and the bike and light touring gear from thirty
kph in 11 feet. I know, because I chewed up a pair of tyres while I
practiced that one to perfection. But I agree with you, for casual use
those roller brakes are overkill.

A fat man on a granny bike braking at over 1g!
Don't the laws of physics apply in Eire these days?

Quite so. That comes out at 1.05g. Centre of mass combined with
wheelbase tell us that he performed the last 8 feet of that stop flat
on his face in the road. But that is a perfectly legitimate way of
stopping your bike.

Anyone who wants to do the sum the easy way just pop this

(30 kph)^2 / (2 * 11 ft) in g

What's this nonsense, Don, a wiki written by you and the equally
useless Eiron? Didn't they teach you in tech school to use compatible
units? You're mixing Imperial and Metric measures hand over orange.
Here is a reliable authority on the subject:

"The maximum braking force that can be applied to a vehicle through
its wheels -- the mass of air having its own retarding force -- is
limited by the friction between the tire and the road, and is equal to
the weight of the vehicle multiplied by the coefficient of friction.
On a dry pavement, this coefficient could be as high as 1; with a
coefficient of unity, retardation would be 1g or 32.2ft/s^2 and the
stopping distance in feet would be V^2/29.9 where V is the speed in
mph. I must stress though that this is on an ideal surface such as
does not exist outside a test facility..."
(p98, Designing and Building Special Cars, by Andre Jute, Batsford,
London 1985)

That math is properly and correctly developed elsewhere in this
thread, where you can go find it.

into Google. I rarely use an other calculator these days.

You should learn how and you won't perpetrae further ****ups like in
this post.

Andre Jute
Our legislators managed to criminalize fox-hunting and smoking; when
they will get off their collective fat backside and criminalize
negative feedback? It is clearly consumed only by thickoes.


Google handles mixed units perfectly happily. That is one of its
biggest joys. The calculation works BECAUSE I included the units;
without them it would have assumed they were dimensionless numbers,
and failed. Try it before you condemn through ignorance.

While what you quote about the maximum braking force above is all fine
and dandy as far as it goes, it ignores the fact that a bike is tall
with respect to its wheelbase, and any attempt to approach that
maximum will result in it toppling. As I said, at 1g, you will be face
down in the road. Eiron actually tried the experiment and found an
empirical limit at about 0.35g, and my back-of-an-envelope
calculations show him to be pretty much spot on.

d

--
Pearce Consulting
http://www.pearce.uk.com

Don Pearce wrote:

While what you quote about the maximum braking force above is all fine
and dandy as far as it goes, it ignores the fact that a bike is tall
with respect to its wheelbase, and any attempt to approach that
maximum will result in it toppling. As I said, at 1g, you will be face
down in the road. Eiron actually tried the experiment and found an
empirical limit at about 0.35g, and my back-of-an-envelope
calculations show him to be pretty much spot on.

I tried it again this morning, and managed to brake in 18 feet from 30kph,
to mix my units in the approved Jute manner, which works out at 0.65g.
This was sitting further back and lower, with hands on the drops.
Still, 0.65g seems a bit high for a pushbike so I'll have to repeat the
test on my next excursion until I get consistent results.

I expect that Jute never did any braking tests at all on his granny bike;
rather he picked 1g as a figure to be proud of and fudged some numbers
to fit.
When challenged, he picked another, believable number . . .

--
Eiron.

On Sun, 09 Sep 2007 11:58:39 +0100, Eiron wrote:

Don Pearce wrote:

While what you quote about the maximum braking force above is all fine
and dandy as far as it goes, it ignores the fact that a bike is tall
with respect to its wheelbase, and any attempt to approach that
maximum will result in it toppling. As I said, at 1g, you will be face
down in the road. Eiron actually tried the experiment and found an
empirical limit at about 0.35g, and my back-of-an-envelope
calculations show him to be pretty much spot on.

I tried it again this morning, and managed to brake in 18 feet from 30kph,
to mix my units in the approved Jute manner, which works out at 0.65g.
This was sitting further back and lower, with hands on the drops.
Still, 0.65g seems a bit high for a pushbike so I'll have to repeat the
test on my next excursion until I get consistent results.

I expect that Jute never did any braking tests at all on his granny bike;
rather he picked 1g as a figure to be proud of and fudged some numbers
to fit.
When challenged, he picked another, believable number . . .

I'm guessing he found it in the same place he found his driver.

d

--
Pearce Consulting
http://www.pearce.uk.com

On Sep 8, 12:42 am, Eiron wrote:
Andre Jute wrote:
Those brakes aren't dodgy, Don, they're hyper-competent; what I forgot
to add is that they have a built-in modulator. They stop the one-
eighth of a ton of me and the bike and light touring gear from thirty
kph in 11 feet. I know, because I chewed up a pair of tyres while I
practiced that one to perfection. But I agree with you, for casual use
those roller brakes are overkill.

A fat man on a granny bike braking at over 1g!

Find the fat on my pic overlooking Dunworly Bay, several places on my
bike pages, and I won't put you in hospital when I run into you. You
mean an opa bike, not an oma bike (or granny bike as you ignorantly
have it). You wouldn't know either if you saw them, sonny.

Don't the laws of physics apply in Eire these days?

Same as everywhere else. Here is a reliable authority on the subject:

"The maximum braking force that can be applied to a vehicle through
its wheels -- the mass of air having its own retarding force -- is
limited by the friction between the tire and the road, and is equal to
the weight of the vehicle multiplied by the coefficient of friction.
On a dry pavement, this coefficient could be as high as 1; with a
coefficient of unity, retardation would be 1g or 32.2ft/s^2 and the
stopping distance in feet would be V^2/29.9 where V is the speed in
mph. I must stress though that this is on an ideal surface such as
does not exist outside a test facility..."
(p98, Designing and Building Special Cars, by Andre Jute, Batsford,
London 1985)

The math is developed elsewhere, where you can go find it.

--
Eiron.

Do come again, Eiron. It is always a giggle when you take yourself
seriously.

Andre Jute
Impedance is futile, you will be simulated into the triode of the
Borg. -- Robert Casey

On Sat, 08 Sep 2007 17:39:11 -0700, Andre Jute
wrote:

On Sep 8, 12:42 am, Eiron wrote:
Andre Jute wrote:
Those brakes aren't dodgy, Don, they're hyper-competent; what I forgot
to add is that they have a built-in modulator. They stop the one-
eighth of a ton of me and the bike and light touring gear from thirty
kph in 11 feet. I know, because I chewed up a pair of tyres while I
practiced that one to perfection. But I agree with you, for casual use
those roller brakes are overkill.

A fat man on a granny bike braking at over 1g!

Find the fat on my pic overlooking Dunworly Bay, several places on my
bike pages, and I won't put you in hospital when I run into you. You
mean an opa bike, not an oma bike (or granny bike as you ignorantly
have it). You wouldn't know either if you saw them, sonny.

Don't the laws of physics apply in Eire these days?

Same as everywhere else. Here is a reliable authority on the subject:

"The maximum braking force that can be applied to a vehicle through
its wheels -- the mass of air having its own retarding force -- is
limited by the friction between the tire and the road, and is equal to
the weight of the vehicle multiplied by the coefficient of friction.
On a dry pavement, this coefficient could be as high as 1; with a
coefficient of unity, retardation would be 1g or 32.2ft/s^2 and the
stopping distance in feet would be V^2/29.9 where V is the speed in
mph. I must stress though that this is on an ideal surface such as
does not exist outside a test facility..."
(p98, Designing and Building Special Cars, by Andre Jute, Batsford,
London 1985)

The math is developed elsewhere, where you can go find it.


Go and ask your driver. He will put you straight about braking.

d

--
Pearce Consulting
http://www.pearce.uk.com