"Actually you are the first person to bring up this issue"

Carl Fogel writes:

I can't make the angles work out as you suggest.

In fact, an upright seems to have a steeper and less effective
braking angle from center of gravity to contact patch, 61 degrees
versus 54 degrees for the recumbent.

Here's how I tried to figure the angles. I gather that the ratio of
the adjacent (longer) to the opposite (shorter) legs of a right
triangle should give the tangent of the angle that I want.

http://www.ransbikes.com/2004Bikes/Rocket.htm

When I measure things for the recumbent from where I expect the
belly button to be to the contact patch, I get a right triangle with
an adjacent side of about 75mm on my screen and an opposite side of
55mm.

(If anything, the center of gravity should be further back than the
navel, given the rider's reclining position.)

With 75/55 = 1.3636, my tangent-angle lookup shows an angle of about
54 degrees.

When I look at "Bicycling Science" 2nd edition and do the same thing
for figure 8.6 (the upright bike with numerous details and an
indicated center of gravity, page. 197), I get a 45-inch adjacent
side and a 25- inch opposite side, 45/25= 1.8, and my tangent-angle
lookup says about 61 degrees.

I think you'll find that with the legs forward as in the recumbent,
the CG lies ahead of the usual middle of the gut or belly button, the
body being angled similarly to that of an upright rider except that
the heavier part is more forward. The angle for the short wheel base
recumbent isn't any better than that of the conventional bicycle and
in the case of the one in question, it did an endo surprisingly easy
in the parking lot test.

Here's the corrected address for the blue trike:

http://www.ihpva.org/incoming/2002/dragonflyer/df1a.jpg

For some reason that URL doesn't work and returns a message:

"I am sorry, the URL you are looking for could not be found."

Jobst Brandt

Carl Fogel writes:

I can't make the angles work out as you suggest.

In fact, an upright seems to have a steeper and less effective
braking angle from center of gravity to contact patch, 61 degrees
versus 54 degrees for the recumbent.

Here's how I tried to figure the angles. I gather that the ratio of
the adjacent (longer) to the opposite (shorter) legs of a right
triangle should give the tangent of the angle that I want.

http://www.ransbikes.com/2004Bikes/Rocket.htm

When I measure things for the recumbent from where I expect the
belly button to be to the contact patch, I get a right triangle with
an adjacent side of about 75mm on my screen and an opposite side of
55mm.

(If anything, the center of gravity should be further back than the
navel, given the rider's reclining position.)

With 75/55 = 1.3636, my tangent-angle lookup shows an angle of about
54 degrees.

When I look at "Bicycling Science" 2nd edition and do the same thing
for figure 8.6 (the upright bike with numerous details and an
indicated center of gravity, page. 197), I get a 45-inch adjacent
side and a 25- inch opposite side, 45/25= 1.8, and my tangent-angle
lookup says about 61 degrees.

I think you'll find that with the legs forward as in the recumbent,
the CG lies ahead of the usual middle of the gut or belly button, the
body being angled similarly to that of an upright rider except that
the heavier part is more forward. The angle for the short wheel base
recumbent isn't any better than that of the conventional bicycle and
in the case of the one in question, it did an endo surprisingly easy
in the parking lot test.

Here's the corrected address for the blue trike:

http://www.ihpva.org/incoming/2002/dragonflyer/df1a.jpg

For some reason that URL doesn't work and returns a message:

"I am sorry, the URL you are looking for could not be found."

Jobst Brandt

Carl Fogel wrote:

Aaaargh! My mother won't let me out without my mittens on strings. A
capital D may be needed in "dragonflyer":

http://www.ihpva.org/incoming/2002/Dragonflyer/df1a.jpg

Aaaargh! We need a side view to make any sense of longitudinal over-
turning stability. The other recumbent picture does that adequately.

Jobst Brandt

Carl Fogel wrote:

Aaaargh! My mother won't let me out without my mittens on strings. A
capital D may be needed in "dragonflyer":

http://www.ihpva.org/incoming/2002/Dragonflyer/df1a.jpg

Aaaargh! We need a side view to make any sense of longitudinal over-
turning stability. The other recumbent picture does that adequately.

Jobst Brandt

Tim McNamara writes:

I don't know but do suspect that changing the dropout design might
be the easier solution, and I don't know but do suspect that
changing the location of the brake would be the better solution.

If you consider forks without offset at the dropout end, as they
are commonly made today, where offset is achieved at the fork
crown, No change other than placing the mounting lugs for the disc
brake caliper on the front side is required. I think the same
caliper would be adequate for most brands with the distance between
caliper and fork leg remaining as it is today. This requires a new
fork strut anyway.

Changing the dropout is not a reasonable option because the dropout
would need to face upward, which would release the wheel on normal
wheel loads, while reversing loads of rider and brake force, being
opposite, could still cause QR loosening. The dropout should be
loaded in the same direction at all times as it is with rim brakes.

I was thinking of facing the open end of the dropouts forward, so
that the normal load would be directed into the end of the fork leg,
and the lower "jaw" of the dropout would constrain the braking
force. This wouldn't be suitable?

As I said, I believe that as long as there is a large reversing load
on that joint it has the ability to loosen a threaded fastener. Now
is not the time to introduce half baked solutions, especially if it
requires changing the fork anyway.

Besides, I like QR's and they are not in contention with any solution
other than positioning the caliper ahead of the fork.

Jobst Brandt

Tim McNamara writes:

I don't know but do suspect that changing the dropout design might
be the easier solution, and I don't know but do suspect that
changing the location of the brake would be the better solution.

If you consider forks without offset at the dropout end, as they
are commonly made today, where offset is achieved at the fork
crown, No change other than placing the mounting lugs for the disc
brake caliper on the front side is required. I think the same
caliper would be adequate for most brands with the distance between
caliper and fork leg remaining as it is today. This requires a new
fork strut anyway.

Changing the dropout is not a reasonable option because the dropout
would need to face upward, which would release the wheel on normal
wheel loads, while reversing loads of rider and brake force, being
opposite, could still cause QR loosening. The dropout should be
loaded in the same direction at all times as it is with rim brakes.

I was thinking of facing the open end of the dropouts forward, so
that the normal load would be directed into the end of the fork leg,
and the lower "jaw" of the dropout would constrain the braking
force. This wouldn't be suitable?

As I said, I believe that as long as there is a large reversing load
on that joint it has the ability to loosen a threaded fastener. Now
is not the time to introduce half baked solutions, especially if it
requires changing the fork anyway.

Besides, I like QR's and they are not in contention with any solution
other than positioning the caliper ahead of the fork.

Jobst Brandt

Jobst Brandt wrote:
Carl Fogel writes:
I can't make the angles work out as you suggest.
In fact, an upright seems to have a steeper and less effective braking
angle from center of gravity to contact patch, 61 degrees versus 54
degrees for the recumbent.
Here's how I tried to figure the angles. I gather that the ratio of
the adjacent (longer) to the opposite (shorter) legs of a right
triangle should give the tangent of the angle that I want.
http://www.ransbikes.com/2004Bikes/R....ransbikes.co-
m/2004Bikes/Rocket.htm
When I measure things for the recumbent from where I expect the belly
button to be to the contact patch, I get a right triangle with an
adjacent side of about 75mm on my screen and an opposite side of 55mm.
(If anything, the center of gravity should be further back than the
navel, given the rider's reclining position.)
With 75/55 = 1.3636, my tangent-angle lookup shows an angle of about
54 degrees.
When I look at "Bicycling Science" 2nd edition and do the same thing
for figure 8.6 (the upright bike with numerous details and an
indicated center of gravity, page. 197), I get a 45-inch adjacent side
and a 25- inch opposite side,
45/25= 1.8, and my tangent-angle lookup says about 61 degrees.
I think you'll find that with the legs forward as in the recumbent, the
CG lies ahead of the usual middle of the gut or belly button, the body
being angled similarly to that of an upright rider except that the
heavier part is more forward. The angle for the short wheel base
recumbent isn't any better than that of the conventional bicycle and in
the case of the one in question, it did an endo surprisingly easy in the
parking lot test.
Here's the corrected address for the blue trike:
http://www.ihpva.org/incoming/2002/d...ttp://www.ihp-
va.org/incoming/2002/dragonflyer/df1a.jpg
For some reason that URL doesn't work and returns a message:
"I am sorry, the URL you are looking for could not be found."
Jobst Brandt


Dear Jobst

Here's a double-size picture of the rocket recumbent with dreadfull
artistic lines and angles calculated off x-y pixel positions

If anything, it looks as if it would brake even better than
originally thought--about a 50 degree angle from COG to contact patc
versus 61 degrees for the upright with an almost identical wheelbase i
"Bicycling Science.

http://home.comcast.net/~carlfogel/d...cketdiagram.jp

o

http://tinyurl.com/yrtg

Possibly the recumbent that you remember wasn't quite identica
to this one

As for Tom's elusive blue Dragonflyer, there are a dozen luri
views here

http://www.ihpva.org/incoming/2002/Dragonflye

Yes, double-checked that one. (Sorry about my incorrect corrections o
addresses.) This picture gives an almost side-view

http://www.ihpva.org/incoming/2002/Dragonflyer/df2.jp

Weird-lookin' thing

Carl Foge


-

Jobst Brandt wrote:
Carl Fogel writes:
I can't make the angles work out as you suggest.
In fact, an upright seems to have a steeper and less effective braking
angle from center of gravity to contact patch, 61 degrees versus 54
degrees for the recumbent.
Here's how I tried to figure the angles. I gather that the ratio of
the adjacent (longer) to the opposite (shorter) legs of a right
triangle should give the tangent of the angle that I want.
http://www.ransbikes.com/2004Bikes/R....ransbikes.co-
m/2004Bikes/Rocket.htm
When I measure things for the recumbent from where I expect the belly
button to be to the contact patch, I get a right triangle with an
adjacent side of about 75mm on my screen and an opposite side of 55mm.
(If anything, the center of gravity should be further back than the
navel, given the rider's reclining position.)
With 75/55 = 1.3636, my tangent-angle lookup shows an angle of about
54 degrees.
When I look at "Bicycling Science" 2nd edition and do the same thing
for figure 8.6 (the upright bike with numerous details and an
indicated center of gravity, page. 197), I get a 45-inch adjacent side
and a 25- inch opposite side,
45/25= 1.8, and my tangent-angle lookup says about 61 degrees.
I think you'll find that with the legs forward as in the recumbent, the
CG lies ahead of the usual middle of the gut or belly button, the body
being angled similarly to that of an upright rider except that the
heavier part is more forward. The angle for the short wheel base
recumbent isn't any better than that of the conventional bicycle and in
the case of the one in question, it did an endo surprisingly easy in the
parking lot test.
Here's the corrected address for the blue trike:
http://www.ihpva.org/incoming/2002/d...ttp://www.ihp-
va.org/incoming/2002/dragonflyer/df1a.jpg
For some reason that URL doesn't work and returns a message:
"I am sorry, the URL you are looking for could not be found."
Jobst Brandt


Dear Jobst

Here's a double-size picture of the rocket recumbent with dreadfull
artistic lines and angles calculated off x-y pixel positions

If anything, it looks as if it would brake even better than
originally thought--about a 50 degree angle from COG to contact patc
versus 61 degrees for the upright with an almost identical wheelbase i
"Bicycling Science.

http://home.comcast.net/~carlfogel/d...cketdiagram.jp

o

http://tinyurl.com/yrtg

Possibly the recumbent that you remember wasn't quite identica
to this one

As for Tom's elusive blue Dragonflyer, there are a dozen luri
views here

http://www.ihpva.org/incoming/2002/Dragonflye

Yes, double-checked that one. (Sorry about my incorrect corrections o
addresses.) This picture gives an almost side-view

http://www.ihpva.org/incoming/2002/Dragonflyer/df2.jp

Weird-lookin' thing

Carl Foge


-

wrote:
I think you'll find that with the legs forward as in the recumbent,
the CG lies ahead of the usual middle of the gut or belly button, the
body being angled similarly to that of an upright rider except that
the heavier part is more forward. The angle for the short wheel base
recumbent isn't any better than that of the conventional bicycle and
in the case of the one in question, it did an endo surprisingly easy
in the parking lot test.

I have verified that one can lock and skid the front wheel during hard
braking on a classic LWB design such as the one pictured below. Such a
bike stops alarmingly fast on clean dry pavement when both brakes are
applied just short of locking the wheels.

http://www.easyracers.com/images/riding.jpg
http://www.easyracers.com/images/riding2.jpg

This bike does pretty well on dirt roads and trails, too.

http://tinyurl.com/3ge8o

--
Bill Bushnell

wrote:
I think you'll find that with the legs forward as in the recumbent,
the CG lies ahead of the usual middle of the gut or belly button, the
body being angled similarly to that of an upright rider except that
the heavier part is more forward. The angle for the short wheel base
recumbent isn't any better than that of the conventional bicycle and
in the case of the one in question, it did an endo surprisingly easy
in the parking lot test.

I have verified that one can lock and skid the front wheel during hard
braking on a classic LWB design such as the one pictured below. Such a
bike stops alarmingly fast on clean dry pavement when both brakes are
applied just short of locking the wheels.

http://www.easyracers.com/images/riding.jpg
http://www.easyracers.com/images/riding2.jpg

This bike does pretty well on dirt roads and trails, too.

http://tinyurl.com/3ge8o

--
Bill Bushnell