Wurfitt?

In article <[email hidden]>,
Peter Clinch <[email hidden]> writes:
|>
|> I don't need to look it up, but furthermore I know from *direct
|> empirical experience* that I can place my weight backwards from its
|> normal position quite instinctively when heavy braking is needed.

Doubtless. So how far does that shift your composite centre of
gravity, and how long does it take (that is a very relevant question,
if you think about it).

|> > And, if you read what YOU said again (quoted above), you were claiming
|> > that people could ride them without any form of acclimatisation. Yet
|> > you are now referring to "initial problems"!
|>
|> I made no such claim, I simply said that the basic action is the
|> same: you get on, you turn the pedals, you go. ...

Of the dozen or so people on the course, every one who had not
ridden a recumbent before got on, started to turn the pedals and
fell off. They ALL needed instruction before they actually went
anywhere - usually very little, but some.

Regards,
Nick Maclaren.

Simon Brooke said:

To be precise, a Brompton has a wheelbase of between and 1015mm and 1045mm
depending on model. Compare that to the wheelbase of a conventional 60cm
framed Cannondale road bike (that's a large size, to you): 1009mm, or 6mm
shorter than the wheelbase of a short wheelbase Brompton. Of all my bikes
(and I'm as tall as you) only one of my mountain bikes has a wheelbase
longer than a Brompton.

So you're not merely wrong, your claim is the opposite of the truth.

You might have a point, but you quote the wrong statistics.
I'd rather brake a racing bike with a castor underneath the
bracketshell, than an ordinary with a wheelbase of 2.0m 😉

/Marten
(still remembering that folding bike my parents bought which had such
short chainstays I fell flat on my back taking off 😉 )

Nick Maclaren wrote on 12/05/2007 19:35 +0100:

Quoted message said:

In article <[email hidden]>,
Tony Raven <[email hidden]> writes:
|>
|> As a taller faster rider of many folding and full size bikes I can
|> state your observation is wrong. I have no more difficulty stopping on
|> my Bromptons or Bike Friday than on my full size bikes equipped with
|> similar brakes. ...

Yes, you have said that the laws of physics don't apply to you before.

No, I have said your mistaken interpretation of the laws of physics does
not apply to me. As a lifelong physicist I have a healthy respect for
the laws of physics but not for people who pretend reality can't happen
because of their mistaken physics.

But then by now we are used to the rest of the world being wrong and
Nick Maclaren (and his many other people) being the only one who is right.

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

In article <[email hidden]>,
Simon Brooke <[email hidden]> writes:

I have omitted most of your quotes, as they were almost all out of
context.

|> To be precise, a Brompton has a wheelbase of between and 1015mm and 1045mm
|> depending on model. Compare that to the wheelbase of a conventional 60cm
|> framed Cannondale road bike (that's a large size, to you): 1009mm, or 6mm
|> shorter than the wheelbase of a short wheelbase Brompton. Of all my bikes
|> (and I'm as tall as you) only one of my mountain bikes has a wheelbase
|> longer than a Brompton.

My wife has just bought a fairly standard mountain bicycle (Giant),
and it has a wheelbase of c. 110 cm (nearly as long as mine!) But
the wheelbase is NOT the only thing that matters - the reason that
my centre of gravity is so far back is the frame angle, not the
wheelbase. The other aspect is how high the rider is, and the
riding position on those things is normally considerably higher than
what I think you are calling a 'conventional road bike'.

However, you have also omitted one very important point. That is
that people tend not to ride what you feel is a conventional bicycle
in the areas where there are a hell of a lot of pedestrians stepping
out suddenly. Such riders tend to avoid those areas (even I did,
when I was riding around Cambridge!), and the typical bicycle ridden
in such situations is not what you think it is.

|> So you're not merely wrong, your claim is the opposite of the truth.

I have certainly heard that the Brompton may have fixed the defects
of older folding bicycles, though I admit that I thought that it had
only alleviated them. I will take a look at it, because a ridable
folder would be useful, and the last time I looked was quite a long
while ago.

Certainly, if it puts the centre of gravity for a 6'+ rider back from
the front wheel more than 2/3 of the height, I should be interested
to know. Does it?

Regards,
Nick Maclaren.

Simon Brooke wrote on 12/05/2007 18:38 +0100:

Quoted message said:

Obviously, on any given bike, a taller rider has a higher CoG; however, for
any given rider, the maximum stopping force on a Brompton vs a
conventional 700c wheeled bike is the same.

To be precise, a Brompton has a wheelbase of between and 1015mm and 1045mm
depending on model. Compare that to the wheelbase of a conventional 60cm
framed Cannondale road bike (that's a large size, to you): 1009mm, or 6mm
shorter than the wheelbase of a short wheelbase Brompton. Of all my bikes
(and I'm as tall as you) only one of my mountain bikes has a wheelbase
longer than a Brompton.

So you're not merely wrong, your claim is the opposite of the truth.

Measurements on my Brompton and Cannondale (no need to measure the Bike
Friday as it was custom made to the same geometry as the Cannondale).

Distance from front wheel contact patch to vertical line through the
centre of saddle for both: approx 800mm.

Distance of saddle above the floor for both: 1070mm

Distance from saddle to handlebars: approx 600mm Brompton; approx 700mm
Cannondale (and handlebars are higher on the Brompton)

So the only difference between all three is my CoG will be slightly
higher and further back on the Brompton because of the slightly more
upright position.

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

in message <[email hidden]>, Nick Maclaren

(') said:

In article <[email hidden]>,
Simon Brooke <[email hidden]> writes:

I have omitted most of your quotes, as they were almost all out of
context.

|> To be precise, a Brompton has a wheelbase of between and 1015mm and
|> 1045mm depending on model. Compare that to the wheelbase of a
|> conventional 60cm framed Cannondale road bike (that's a large size, to
|> you): 1009mm, or 6mm shorter than the wheelbase of a short wheelbase
|> Brompton. Of all my bikes (and I'm as tall as you) only one of my
|> mountain bikes has a wheelbase longer than a Brompton.

My wife has just bought a fairly standard mountain bicycle (Giant),
and it has a wheelbase of c. 110 cm (nearly as long as mine!) But
the wheelbase is NOT the only thing that matters - the reason that
my centre of gravity is so far back is the frame angle, not the
wheelbase. The other aspect is how high the rider is, and the
riding position on those things is normally considerably higher than
what I think you are calling a 'conventional road bike'.

Consider this illustration:
http://www.jasmine.org.uk/~simon/tmp/stability-comparison.jpg

I have taken this picture here:
http://www.bicycledoctor.co.uk/graphics/bromptonm6rplus.jpg
and this picture here:
http://www.cannondale.com/bikes/06/CUSA/large/7RWA3Tblk.jpg

and simply overlaid them; I chose these two because they are reasonably
large, and similar in scale so that the wheelbases approximately match (in
reality the wheelbase of the Brompton is very slightly longer).

As you see, with the contact patches in more or less the same place, the
bottom bracket of the Brompton is slightly further back, the seat tube of
the Brompton is slightly more laid back, the saddle of the Brompton is
slightly further back, the handlebars of the Brompton are higher but
considerably further back.

As you say, the riding position on the Brompton is typically more upright,
putting the centre of mass very slightly higher but considerably further
back. So I think we can say that you are comprehensively wrong on all
counts, as you could very easily have seen for yourself had you bothered
to verify your data.

Quoted message said:

However, you have also omitted one very important point. That is
that people tend not to ride what you feel is a conventional bicycle
in the areas where there are a hell of a lot of pedestrians stepping
out suddenly. Such riders tend to avoid those areas (even I did,
when I was riding around Cambridge!), and the typical bicycle ridden
in such situations is not what you think it is.

That is the most blatant case of goalpost shifting I've seen in a long
while.

Quoted message said:

Certainly, if it puts the centre of gravity for a 6'+ rider back from
the front wheel more than 2/3 of the height, I should be interested
to know. Does it?

A picture is worth a thousand words in these cases, isn't it?

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; So, before proceeding with definitive screwing, choose the
;; position most congenital.
-- instructions for fitting bicycle handlebars

Nick Maclaren said:

Doubtless. So how far does that shift your composite centre of
gravity, and how long does it take (that is a very relevant question,
if you think about it).

A very simple answer: "adequate to keep me from going over the bars".
Whatever compensation tall riders other than yourself make for
their high CoM when riding folders is: "adequate to keep them from
going over the bars". I don't know if they're all doing the same
thing to compensate even, but whatever it is it works, and can be
seen to work, and however many equations you want to write and laws
you want to post doesn't alter that. Everyone is obeying the laws
of physics, simply as they have no choice in the matter. But
they're using their brakes, from speed, and not going flying.

All those reviews and reports and discussions of folders I've read
over the years... were they /all/ exclusively by short people or
folk that never use the brakes or go fast? Or is it all some big
conspiracy not to mention they're death traps? Or have you just
got it wrong? Occam's razor strongly suggests option 3.

Quoted message said:

Of the dozen or so people on the course, every one who had not
ridden a recumbent before got on, started to turn the pedals and
fell off.

As did I first time I tried. So that means I can't ride one? No,
means I didn't have the technique tuned, and in my case (and most
others I see) there was simply far too much pulling on handlebars
that didn't work the way I was used to and conditioned for.

Well Nick, this thread should naturally end soon, because you're
digging a hole for yourself so effectively your CoM is currently
heading for the Moho at great speed, so you don't have to worry
about how high it is any more!

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

In article said:

I have certainly heard that the Brompton may have fixed the defects
of older folding bicycles, though I admit that I thought that it had
only alleviated them. I will take a look at it, because a ridable
folder would be useful, and the last time I looked was quite a long
while ago.

I'm 6'2" and haven't come across a folder which would be ridable
with the upright position you insist on with the standard stem
and bars.
But since you've often complained about the difficulty of finding
a diamond frame that allows that, it's not a folder-specific
disadvantage.

Nick Maclaren said:

Look, this has nothing to do with falling off - it has to do with not
endangering pedestrians in the typical situations that urban utility
bicycles are used in.

So if riding a bike that can't achieve 0.75g of braking (not that I think
your estimates are accurate anyway) in an urban situation is irresponsibly
dangerous, how is anyone supposed to ride in the same situations in the
wet?

Quoted message said:

My observation is that the WORST cyclists for endangering pedestrians
are not the wannabe racers, not the riders of clapped-out heaps of
junk, but the taller and faster riders of folding bicycles. I have
more often seen them swerve between pedestrians (often elderly ones)
at speed to avoid stopping than any other group of cyclist (pro rata
to numbers, of course). And the reason is simple physics; they CAN'T
stop in a hurry, so they don't TRY to.

How many times have you seen these kamikaze folding bicycle riders collide
with a pedestrian?

Anthony

Simon Brooke said:

in message <[email hidden]>, Nick Maclaren

(') said:

However, you have also omitted one very important point. That is
that people tend not to ride what you feel is a conventional bicycle
in the areas where there are a hell of a lot of pedestrians stepping
out suddenly. Such riders tend to avoid those areas (even I did,
when I was riding around Cambridge!), and the typical bicycle ridden
in such situations is not what you think it is.

That is the most blatant case of goalpost shifting I've seen in a long
while.

Based on my experience as a cyclist (with both diamond frame and a folding
bike) and as a pedestrian in Cambridge it's also complete rubbish anyway.

Alan Braggins wrote on 13/05/2007 08:27 +0100:

Quoted message said:

Simon Brooke said:

in message <[email hidden]>, Nick Maclaren

(') said:

However, you have also omitted one very important point. That is
that people tend not to ride what you feel is a conventional bicycle
in the areas where there are a hell of a lot of pedestrians stepping
out suddenly. Such riders tend to avoid those areas (even I did,
when I was riding around Cambridge!), and the typical bicycle ridden
in such situations is not what you think it is.

That is the most blatant case of goalpost shifting I've seen in a long
while.

Based on my experience as a cyclist (with both diamond frame and a folding
bike) and as a pedestrian in Cambridge it's also complete rubbish anyway.

Seconded. To say nothing of a successful ten year campaign in Cambridge
to have an area where there are "a hell of a lot of pedestrians stepping
out suddenly" in front of cyclists re-opened to cycling.

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

Simon Brooke said:

in message <[email hidden]>, Nick Maclaren

(') said:

My wife has just bought a fairly standard mountain bicycle (Giant),
and it has a wheelbase of c. 110 cm (nearly as long as mine!) But
the wheelbase is NOT the only thing that matters - the reason that
my centre of gravity is so far back is the frame angle, not the
wheelbase. The other aspect is how high the rider is, and the
riding position on those things is normally considerably higher than
what I think you are calling a 'conventional road bike'.

Consider this illustration:
http://www.jasmine.org.uk/~simon/tmp/stability-comparison.jpg

Somewhere I've seen a diagram of a Moulton and a diamond frame bike
showing the wheel contact points, bars, saddle, and cranks all in
almost exactly the same place, but I can't find it now.
(The Moulton is a "one size fits most" design but not a folder, of
course. Putting drop bars on the Brompton would interfere with the
fold.)

Quoted message said:

As you say, the riding position on the Brompton is typically more upright,
putting the centre of mass very slightly higher but considerably further
back. So I think we can say that you are comprehensively wrong on all
counts, as you could very easily have seen for yourself had you bothered
to verify your data.

Typically more upright, yes, but not more upright than Nick's diamond
bike. That he can't find a folder or Moulton type bike that allows
his position for someone his size is a legitimate complaint. But it
doesn't invalidate Pete's point about a one size fits _most_ design,
nor justify ignoring the actual physics of the situation.
(The Brompton has longer seatposts available as an option, but when using
them the standard stem won't allow the bars to be raised well above the
saddle in the manner of, say, a Pedersen http://www.pedersenbicycle.dk/8.htm)

Alan Braggins said:

(The Brompton has longer seatposts available as an option, but when using
them the standard stem won't allow the bars to be raised well above the
saddle in the manner of, say, a Pedersen http://www.pedersenbicycle.dk/8.htm)

IIRC the NS Moulton comes with highly adhustable bars, though since
they rotate rather than slide you may not get the perfect up/along
combination for you. And there is another practical difficulty, of
course, which is having to knock off a bank first... ;-/

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

Nick Maclaren said:

In article <[email hidden]>,
John Kane <[email hidden]> writes:
|>
|> > A long time back, I did some calculations that indicated that the
|> > simplest way that most cyclists could improve their performance was
|> > to staple their ears onto their head. That isn't JUST a joke,
|> > incidentally, as it reduces your aerodynamic cross-section by about
|> > 0.1%. That gives an equivalent improvement on the flat to 1-10 pounds
|> > off the weight of the bicycle, depending on the speed of the rider.
|>
|> Would tape do? I dislike getting bloodstains on the jersey.

Probably. But it's SO much less amusing to propose :-)

Hmm... I wonder how much more useful this would be for a cyclist with
ears perpendicular to his head.

Cheers,
Luke

--
Lincoln City 0-2 Southend United (AET)
Swansea City 2-2 Southend United
We went up twice with Tilly and Brush

Alan Braggins said:

Somewhere I've seen a diagram of a Moulton and a diamond frame bike
showing the wheel contact points, bars, saddle, and cranks all in
almost exactly the same place, but I can't find it now.
(The Moulton is a "one size fits most" design but not a folder, of
course.

A Moulton AM has a shortish 540mm toptube, not much rake due to the
small wheels and very long chainstays.
--
/Marten

info(apestaartje)m-gineering(punt)nl

In article said:

Alan Braggins said:

(The Brompton has longer seatposts available as an option, but when using
them the standard stem won't allow the bars to be raised well above the
saddle in the manner of, say, a Pedersen http://www.pedersenbicycle.dk/8.htm)

IIRC the NS Moulton comes with highly adhustable bars, though since
they rotate rather than slide you may not get the perfect up/along
combination for you.

Yep - http://www.alexmoulton.co.uk/images/gallery/large/bars.gif

(But that doesn't help Nick find a folder, rather than a seperable
non-diamond frame bike. Bike Friday might be able to do him a suitable
custom bike, but that has the same "first choose your bank" problem
that an NS Moulton does. I know the SP Brompton based machines can have
non-standard stems, but not whether they would do the job.)

Alan Braggins wrote on 13/05/2007 14:20 +0100:

Quoted message said:

(But that doesn't help Nick find a folder, rather than a seperable
non-diamond frame bike. Bike Friday might be able to do him a
suitable custom bike, but that has the same "first choose your bank"
problem that an NS Moulton does. I know the SP Brompton based
machines can have non-standard stems, but not whether they would do
the job.)

The Brompton steering will be far to sensitive for Nick with his balance
problems. A Bike Friday or Airnimal would be much better but they are
not foldable in the same way. The best option might be a Bike Friday
Tikit when they come available. They're about £600 in the States but no
doubt quite a bit more here.
http://www.bikefriday.com/images/email/1325-tikitfeb07/

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

In article <[email hidden]>, Alan Braggins
[email hidden] says...

Quoted message said:

The Brompton has longer seatposts available as an option, but when using
them the standard stem won't allow the bars to be raised well above the
saddle

It can't be particularly difficult to fit some high rise bars, can it?

Rob Morley wrote on 13/05/2007 17:21 +0100:

Quoted message said:

In article <[email hidden]>, Alan Braggins
[email hidden] says...

Quoted message said:

The Brompton has longer seatposts available as an option, but when using
them the standard stem won't allow the bars to be raised well above the
saddle

It can't be particularly difficult to fit some high rise bars, can it?

They are already high rise and if they are too high they will foul the
ground when you try to fold them.
--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

In article <[email hidden]>, Tony Raven
[email hidden] says...

Quoted message said:

Rob Morley wrote on 13/05/2007 17:21 +0100:

Quoted message said:

In article <[email hidden]>, Alan Braggins
[email hidden] says...

Quoted message said:

The Brompton has longer seatposts available as an option, but when using
them the standard stem won't allow the bars to be raised well above the
saddle

It can't be particularly difficult to fit some high rise bars, can it?

They are already high rise and if they are too high they will foul the
ground when you try to fold them.

I meant /really/ high rise. Or a stem extension to use the standard
bars. You could fit a quick release to the clamp so you could fold them
back, but that might not inspire huge confidence when jamming on the
brakes. There are ways I can think of to overcome this, but they're
more within the capability of a framebuilder than a home mechanic.