Cities Turning to Bicycles

In article ,
Nate Nagel wrote:

Alan Baker wrote:

In article ,
(Nate Nagel) wrote:


Arif Khokar wrote in message
...

Alan Baker wrote:


I've driven my brother's Nissan Pathfinder (even before it had its
shocks replaced) and it can easily -- easily -- more than double the
advisory speeds on most ramps.

Advisory speeds are based on the comfort level of a driver driving a
1939 Ford Vehicle. The lateral force would be enough to have a "ball on
a string" deviate 10 degrees from the vertical position. Most drivers
take curves such that the deviation would be between 12 and 14 degrees,
IIRC.

found this site:

http://manuals.dot.state.tx.us/dynaw...BookTextView/4
00
9;cs=default;ts=default

I don't see any mention of a 1939 Ford, but essentially that appears
to be correct. They do apparently allow higher G-forces for very slow
speed turns, but 10 degrees is the recommended value for 35 MPH or
higher. In any case the maximum value allowed is 14 degrees, still
far less than people seem to find acceptable in day to day driving. I
wouldn't be surprised if a 10 degree ball bank indicator reading *was*
perfectly safe and comfortable in a bone stock '39 Ford, honestly.
Perhaps it's time to revisit these standards; how often is a vehicle
in regular use anywhere in the US older than the mid-late 1960's?

Key quote: "The speed to be posted on the curve should not be reduced
arbitrarily below that determined by the procedures provided in this
section." Hmm, looks like *that* recommendation isn't followed across
the board...

Note that there really isn't *any* hard standard for advisory speeds
for exit ramps, although obviously I have no way of knowing if that
section of this document is derived from the Green Book or is unique
to the state of TX.

nate


It also shows how stupid the system is.

A ball bank indicator? One big problem with it: in addition to the
movement of the ball due to lateral g forces, you also get movement due
to the roll of the vehicle. And since different vehicles roll different
amounts, you automatically get inconsistent results.


Maybe *YOUR* car has perceptible roll at under 0.5G G

nate

*Every* car does.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

Nate Nagel wrote:
Frank Krygowski wrote:

Brent P wrote:

In article , Frank Krygowski wrote:

Brent P wrote:


I would suggest Frank ride his bicycle through a decreasing radius
turn that wasn't visable until he was in it such that it forced him
to brake hard. This would probably be the best lesson as to why
this sort of design should be avoided. Braking while turning is as
ill-advised on a bicycle as it is driving. Probably more so.



:-)

Almost every time I make a turn on the bike, it's done with a
decreasing radius, and with braking while in the turn! This is
normal for a bicycle!




Sheesh. Newbies!




Not braking by coasting frank. braking with the brakes. Coasting is
normal on the road, not squeezing the hand brakes.



Yes, braking with the brakes, Brent. While in a curve. Every day.
It's quite normal.



google for "friction circle" to see why that's a bad idea (yes, on a
bike too.)

It's only a bad idea if you enter the turn at a speed where *all* of
the available traction is used for cornering, i.e. too fast. But since
many turns are entered before the driver can completely see the
turning radius throughout the turn he should always leave sufficient
margin so there is still traction available for braking in addition to
cornering. Fortunately the mathematics of perpendicular vector addition
help us out here. The equation of a circle is x^2 + y^2 = r^2 where we
can use 'x' for the traction available for braking and 'y' for the
traction available for cornering, and 'r', the resultant is the total
available traction. Let's assume the total traction is 1. Then
entering the turn so fast that cornering alone requires a traction of
1.0 would leave nothing available for braking. But entering even a
little slower, say where cornering only requires a traction of 0.9 now
allows us to use some braking up to a traction of sqrt(1-.9^2) = 0.44

Because the forces are perpendicular we can use our brakes up to almost
44% of maximum and simultaneously corner at 90% of maximum without
exceeding 100% of the available traction. Even if the driver (or
cyclist) cuts it closer and is cornering so fast that he's using
95% of the available traction he can still apply the brakes at 31% of
maximum before risking a skid. And even the real thrill-seeker
who corners at 99% still has 14% of maximum braking available to him
before initiating a skid. So yes, the brakes should be applied
carefully and with some caution while cornering, but there is nothing
about "friction circles" (really just basic vector force addition)
that says no braking should be combined with cornering.

I live near a 3500' hill which I frequently ascend and descend on my
bicycle, usually in the company of other cyclists. The road is very
winding and, as is common of many mountain roads, has turns where the
radius of curvature varies. I use my brakes on the way down in
most of the turns and don't think I've ever seen anyone descend this
hill without doing a substantial amount of braking while in the turns.

Nate Nagel wrote:
Frank Krygowski wrote:


Yes, braking with the brakes, Brent. While in a curve. Every day.
It's quite normal.

google for "friction circle" to see why that's a bad idea (yes, on a
bike too.)

I don't need to google friction circles. I know all about them.

It's interesting that Brent claimed _I_ was talking about racing, i.e.
limit of adhesion situations, now that you are using a term that really
pertains only to that situation.

If a vehicle is not undergoing extreme lateral acceleration, there is
plenty of friction available for braking as well as turning. And, as on
freeway exit ramps, I have sense to stay away from ten-tenths cornering
moves.

--
--------------------+
Frank Krygowski [To reply, remove rodent and vegetable dot com,
replace with cc.ysu dot edu]

In article , Frank Krygowski wrote:
Nate Nagel wrote:
Frank Krygowski wrote:


Yes, braking with the brakes, Brent. While in a curve. Every day.
It's quite normal.

google for "friction circle" to see why that's a bad idea (yes, on a
bike too.)

I don't need to google friction circles. I know all about them.

It's interesting that Brent claimed _I_ was talking about racing, i.e.
limit of adhesion situations, now that you are using a term that really
pertains only to that situation.

It was your quote about what a 'skilled bike racer' does. You are
basically telling us we are wrong to apply racing techniques to
driving on the public roads while at the same time chastising us for
not doing so and prefering not to have to.

Frank Krygowski wrote:

Nate Nagel wrote:

Frank Krygowski wrote:


Yes, braking with the brakes, Brent. While in a curve. Every day.
It's quite normal.

google for "friction circle" to see why that's a bad idea (yes, on a
bike too.)


I don't need to google friction circles. I know all about them.

It's interesting that Brent claimed _I_ was talking about racing, i.e.
limit of adhesion situations, now that you are using a term that really
pertains only to that situation.

If a vehicle is not undergoing extreme lateral acceleration, there is
plenty of friction available for braking as well as turning. And, as on
freeway exit ramps, I have sense to stay away from ten-tenths cornering
moves.


But that's exactly what you were busting me on earlier - entering a
corner at, say, 6/10 and suddenly discovering that I needed 10/10 or
more - which can happen. You also suggested that I slow down in that
situation, implying braking...

nate

--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

Peter wrote in message ...
Nate Nagel wrote:
Frank Krygowski wrote:

Brent P wrote:

In article , Frank Krygowski wrote:

Brent P wrote:


I would suggest Frank ride his bicycle through a decreasing radius
turn that wasn't visable until he was in it such that it forced him
to brake hard. This would probably be the best lesson as to why
this sort of design should be avoided. Braking while turning is as
ill-advised on a bicycle as it is driving. Probably more so.



:-)

Almost every time I make a turn on the bike, it's done with a
decreasing radius, and with braking while in the turn! This is
normal for a bicycle!




Sheesh. Newbies!




Not braking by coasting frank. braking with the brakes. Coasting is
normal on the road, not squeezing the hand brakes.



Yes, braking with the brakes, Brent. While in a curve. Every day.
It's quite normal.



google for "friction circle" to see why that's a bad idea (yes, on a
bike too.)

It's only a bad idea if you enter the turn at a speed where *all* of
the available traction is used for cornering, i.e. too fast. But since
many turns are entered before the driver can completely see the
turning radius throughout the turn he should always leave sufficient
margin so there is still traction available for braking in addition to
cornering. Fortunately the mathematics of perpendicular vector addition
help us out here. The equation of a circle is x^2 + y^2 = r^2 where we
can use 'x' for the traction available for braking and 'y' for the
traction available for cornering, and 'r', the resultant is the total
available traction. Let's assume the total traction is 1. Then
entering the turn so fast that cornering alone requires a traction of
1.0 would leave nothing available for braking. But entering even a
little slower, say where cornering only requires a traction of 0.9 now
allows us to use some braking up to a traction of sqrt(1-.9^2) = 0.44


I'm not going to check your math, but it sounds about right,
neglecting the fact that a typical friction circle for a car is more
of a friction oval-esque kind of thing (and generally can't be found
under acceleration, unless you have ridiculous amounts of power.)
However, on principle, I try to do all my braking before a corner at
least on the street as, what happens if I enter a corner at what I
think is 6/10 and it turns out to be 10/10 and I suddenly find that I
can't brake? (the exact situation Frank's been chastising me about
and claiming I'm unskilled for finding myself in.) What would have
happened had I followed Frank's recommendation to "slow down" once I
discovered the curve was tighter than I thought? What would have
happened if I'd entered the initial part of the curve "hot," planning
on trail braking to the apex?

Alternately, if I'm planning on trail braking into a corner, that
might leave me closer to the circle than I want to be on the street,
even if it's not a 10/10 corner...

I guess my point is that you are correct there is a time and place for
trail braking but generally I don't really see much need for it on the
street. I generally try to corner under very light power so I'm
holding a constant speed and have as big a cushion between my actual
state and the limits of the friction circle as possible at any given
time and speed. (obviously depending on the corner that might be
difficult on a bike unless you have short cranks, but you get the
idea)

nate

Nate Nagel wrote:
Frank Krygowski wrote:

If a vehicle is not undergoing extreme lateral acceleration, there is
plenty of friction available for braking as well as turning. And, as on
freeway exit ramps, I have sense to stay away from ten-tenths cornering
moves.

But that's exactly what you were busting me on earlier - entering a
corner at, say, 6/10 and suddenly discovering that I needed 10/10 or
more - which can happen. You also suggested that I slow down in that
situation, implying braking...

This doesn't seem to make sense to me.

If one is driving (or riding) reasonably well under one's limits (as one
should be doing in traffic on public roads) and paying attention (also as
one should be doing in traffic on public roads), then there aren't many
things that should "suddenly" push one over these limits. If something
as unextraordinary as a decrease in curve radius will push you over the
edge, then you are driving to close to it; if you are driving sufficiently
fast that you can't see what is ahead in time to react to it appropriately,
then you are driving too fast!

This isn't rocket science.


--
greg byshenk - - Leiden, NL

Alan Baker wrote:

The huge mistake is for advisory limits to be set so inconsistently that
one doesn't have an honest idea for what speeds can be used in such
situations.

This is almost certainly true (and it is at least arguably true that
advisory speed limits are indeed seriously inconsistent), as is the
earlier comment that decreasing radius turns are to be avoided if
possible.

I would note, though, that such things have absolutely nothing to do
with speed humps or residential speed limits (or even speed limits on
urban surface arterials). I don't know if anyone is actually suggesting
that they do; I am justing noting the fact.


--
greg byshenk - - Leiden, NL

In article 4b39d.135425$wV.11486@attbi_s54,
Brent P wrote:
In article , Frank Krygowski wrote:
Nate Nagel wrote:
Frank Krygowski wrote:


Yes, braking with the brakes, Brent. While in a curve. Every day.
It's quite normal.

google for "friction circle" to see why that's a bad idea (yes, on a
bike too.)

I don't need to google friction circles. I know all about them.

It's interesting that Brent claimed _I_ was talking about racing, i.e.
limit of adhesion situations, now that you are using a term that really
pertains only to that situation.

It was your quote about what a 'skilled bike racer' does. You are
basically telling us we are wrong to apply racing techniques to
driving on the public roads while at the same time chastising us for
not doing so and prefering not to have to.

Hmm. Recap here. Frank thinks it is perfectly reasonable to

a) Post the exact same warning signs on a constant curve, and increasing
radius curve with the same entry radius as the constant curve.

b) Have the increasing radius of the curve be hidden to traffic
entering the curve

c) Excoriate drivers who enter the increasing radius curve in the
same way as the constant curve, and then have to use racing maneuvers
to avoid leaving the roadway

using as evidence

d) The "fact" that most drivers, even those unfamiliar with the road,
get through without such maneuvers and without leaving the roadway

even though

e) Barriers at the side of the roadway show many signs of impact, and
no data is available on the maneuvers most of those who DIDN'T hit had to take
to avoid doing so.

And he "thinks" he's being perfectly reasonable.

In article ,
Matthew Russotto wrote:
In article 4b39d.135425$wV.11486@attbi_s54,
Brent P wrote:
In article , Frank Krygowski wrote:
Nate Nagel wrote:
Frank Krygowski wrote:


Yes, braking with the brakes, Brent. While in a curve. Every day.
It's quite normal.

google for "friction circle" to see why that's a bad idea (yes, on a
bike too.)

I don't need to google friction circles. I know all about them.

It's interesting that Brent claimed _I_ was talking about racing, i.e.
limit of adhesion situations, now that you are using a term that really
pertains only to that situation.

It was your quote about what a 'skilled bike racer' does. You are
basically telling us we are wrong to apply racing techniques to
driving on the public roads while at the same time chastising us for
not doing so and prefering not to have to.

Hmm. Recap here. Frank thinks it is perfectly reasonable to

a) Post the exact same warning signs on a constant curve, and increasing
radius curve with the same entry radius as the constant curve.

b) Have the increasing radius of the curve be hidden to traffic
entering the curve

c) Excoriate drivers who enter the increasing radius curve in the
same way as the constant curve, and then have to use racing maneuvers
to avoid leaving the roadway

Ack. Substitute "decreasing" for "increasing" above. Everyone but
Frank knew what I meant, of course.

using as evidence

d) The "fact" that most drivers, even those unfamiliar with the road,
get through without such maneuvers and without leaving the roadway

even though

e) Barriers at the side of the roadway show many signs of impact, and
no data is available on the maneuvers most of those who DIDN'T hit had to take
to avoid doing so.

And he "thinks" he's being perfectly reasonable.