UPGRADE 1970'S BIKES

On Oct 6, 4:09 pm, Frank Krygowski wrote:
On Oct 6, 3:01 pm, Jay Beattie wrote:

On Oct 6, 10:53 am, Frank Krygowski wrote:

I usually have my straps set at a sort of compromise length, loose
enough to flip into very quickly, but tight enough to provide just a
bit of security against foot slips. They're tight enough that I can
bunny hop, which is good enough for me.

Based on all the trick riding I see, you don't need to be clipped in
to bunny hop the bike -- but I find it hard to do on a road bike
without clips, so I must be a flounder...

I just tried it, to be sure of my memory. As I thought, I can get the
rear wheel up just a little, maybe a couple inches, on a bike without
clips. That's my retro 3 speed. I seem to be pushing a bit rearward
on the pedals to do it, which seems to be the same thing I see in
videos likehttp://www.youtube.com/watch?v=Z19zFlPah-o

Look at ~2:00. See how his weight goes way back to lift the front end,
then, springing off the pedals, he leaps into the air, chasing the
front end with his body mass, until the handlebars are in his lap.
The rear wheel is still on the ground. Then he fluidly but
instantaneously transfers his body's inertia to the bike via the
handlebars. See how his elbows and knees - fully extended a fraction
of a second before - are bent at the top and the bike has come up
underneath him? There's no lifting it by the pedals.

I don't know if I've really got it figured out, but for me I think
it's almost all through the handlebars.

... although
there's obviously a lot more going on with someone at that skill
level. For example, he temporarily repeals the law of gravity...


Nice to see you embracing the inexplicable, but as we know (despite
whatever the preacher sells you on Sunday), nature and physics do not
ever take a break. If you ask him how he does it, he might say, "Ride
Bike!" If you had asked Jimi Hendrix how he plays the guitar...

Dan O writes:

On Oct 6, 4:09 pm, Frank Krygowski wrote:
On Oct 6, 3:01 pm, Jay Beattie wrote:

On Oct 6, 10:53 am, Frank Krygowski wrote:

I usually have my straps set at a sort of compromise length, loose
enough to flip into very quickly, but tight enough to provide just a
bit of security against foot slips. They're tight enough that I can
bunny hop, which is good enough for me.

Based on all the trick riding I see, you don't need to be clipped in
to bunny hop the bike -- but I find it hard to do on a road bike
without clips, so I must be a flounder...

I just tried it, to be sure of my memory. As I thought, I can get the
rear wheel up just a little, maybe a couple inches, on a bike without
clips. That's my retro 3 speed. I seem to be pushing a bit rearward
on the pedals to do it, which seems to be the same thing I see in
videos likehttp://www.youtube.com/watch?v=Z19zFlPah-o

Look at ~2:00. See how his weight goes way back to lift the front end,
then, springing off the pedals, he leaps into the air, chasing the
front end with his body mass, until the handlebars are in his lap.
The rear wheel is still on the ground. Then he fluidly but
instantaneously transfers his body's inertia to the bike via the
handlebars. See how his elbows and knees - fully extended a fraction
of a second before - are bent at the top and the bike has come up
underneath him? There's no lifting it by the pedals.

I don't know if I've really got it figured out, but for me I think
it's almost all through the handlebars.

An impulsive force applied to the handlebars and in a direction directly
away from the center of mass of the bike will do the trick. To verify
that, stand in front of the bike and apply such an impulse; both wheels
will leave the ground simultaneously. Alas, applying the same impulsive
force while riding the bike is quite awkward (try it, you'll see). The
way I believe it is done is in two steps: an upward pull, then a forward
push. Those can be efficiently applied and since the average direction
of the two force is through the CoM the result is nearly the same.

--
Joe Riel

there's a cable attached to the rider....

kinda lika jack knife dive into water.

one would believe lifting with feet/abdomen transfering that motion to the bars thru shoulders is a complete body motion.

its easy to do...getting effective height and control is difficult.

On Oct 6, 10:59 pm, Joe Riel wrote:
Dan O writes:
On Oct 6, 4:09 pm, Frank Krygowski wrote:
On Oct 6, 3:01 pm, Jay Beattie wrote:

On Oct 6, 10:53 am, Frank Krygowski wrote:

I usually have my straps set at a sort of compromise length, loose
enough to flip into very quickly, but tight enough to provide just a
bit of security against foot slips. They're tight enough that I can
bunny hop, which is good enough for me.

Based on all the trick riding I see, you don't need to be clipped in
to bunny hop the bike -- but I find it hard to do on a road bike
without clips, so I must be a flounder...

I just tried it, to be sure of my memory. As I thought, I can get the
rear wheel up just a little, maybe a couple inches, on a bike without
clips. That's my retro 3 speed. I seem to be pushing a bit rearward
on the pedals to do it, which seems to be the same thing I see in
videos likehttp://www.youtube.com/watch?v=Z19zFlPah-o

Look at ~2:00. See how his weight goes way back to lift the front end,
then, springing off the pedals, he leaps into the air, chasing the
front end with his body mass, until the handlebars are in his lap.
The rear wheel is still on the ground. Then he fluidly but
instantaneously transfers his body's inertia to the bike via the
handlebars. See how his elbows and knees - fully extended a fraction
of a second before - are bent at the top and the bike has come up
underneath him? There's no lifting it by the pedals.

I don't know if I've really got it figured out, but for me I think
it's almost all through the handlebars.

An impulsive force applied to the handlebars and in a direction directly
away from the center of mass of the bike will do the trick. To verify
that, stand in front of the bike and apply such an impulse; both wheels
will leave the ground simultaneously. Alas, applying the same impulsive
force while riding the bike is quite awkward (try it, you'll see). The
way I believe it is done is in two steps: an upward pull, then a forward
push. Those can be efficiently applied and since the average direction
of the two force is through the CoM the result is nearly the same.


Right, note in the video how when Danny lifts the whole bike into the
air at once his arms usually end up extended. I think it involves
lifting the front end and launching yourself up right behind it, then
thrusting the bars forward, rotating the bike in space underneath him,
bringing the rear wheel up along with the front - the relative inertia
of his upward flying body mass to maintain the front end off the
ground - viola! - both wheels off the ground.

It kind of cracks me up that Frank keeps his straps loose for
virtually no backward retention, thinks the retention is where he
applies force to bunnyhop, then thinks the force he applies is
backward at the pedal.

On Oct 7, 1:59*am, Joe Riel wrote:
Dan O writes:
On Oct 6, 4:09 pm, Frank Krygowski wrote:
On Oct 6, 3:01 pm, Jay Beattie wrote:

On Oct 6, 10:53 am, Frank Krygowski wrote:

I usually have my straps set at a sort of compromise length, loose
enough to flip into very quickly, but tight enough to provide just a
bit of security against foot slips. *They're tight enough that I can
bunny hop, which is good enough for me.

Based on all the trick riding I see, you don't need to be clipped in
to bunny hop the bike -- but I find it hard to do on a road bike
without clips, so I must be a flounder...

I just tried it, to be sure of my memory. *As I thought, I can get the
rear wheel up just a little, maybe a couple inches, on a bike without
clips. *That's my retro 3 speed. *I seem to be pushing a bit rearward
on the pedals to do it, which seems to be the same thing I see in
videos likehttp://www.youtube.com/watch?v=Z19zFlPah-o

Look at ~2:00. See how his weight goes way back to lift the front end,
then, springing off the pedals, he leaps into the air, chasing the
front end with his body mass, until the handlebars are in his lap.
The rear wheel is still on the ground. *Then he fluidly but
instantaneously transfers his body's inertia to the bike via the
handlebars. *See how his elbows and knees - fully extended a fraction
of a second before - are bent at the top and the bike has come up
underneath him? *There's no lifting it by the pedals.

I don't know if I've really got it figured out, but for me I think
it's almost all through the handlebars.

An impulsive force applied to the handlebars and in a direction directly
away from the center of mass of the bike will do the trick. *To verify
that, stand in front of the bike and apply such an impulse; both wheels
will leave the ground simultaneously. *Alas, applying the same impulsive
force while riding the bike is quite awkward (try it, you'll see). *The
way I believe it is done is in two steps: an upward pull, then a forward
push. *Those can be efficiently applied and since the average direction
of the two force is through the CoM the result is nearly the same.

That sounds like a possibility to me. However, when I do it on a flat
pedal bike, I certainly get the impression my feet are pushing a bit
backward on the pedals, and sort of trying to claw them upward, with
my toes pointed downward. I'm trying to understand that sensation.
(In the videos, it looks like the rider's toes are pointed down, too.)

I'll get more serious than I was a couple posts ago (since nobody
really repeals the law of gravity):

To understand a bike being bunny hopped, I think it may help to think
about how a skateboard is bunny hopped. The processes aren't the same
(there's obviously no direct upward pull from the shoes on the
skateboard) but I think there are some similarities.

As I understand it, the skater jumps his own body mass upward. That's
easy. And he'll soon lift his legs upward after his main body mass.
But (nearly) simultaneously with the initial jump, he kicks down on
the tail of the board. That levers the rest of the board upward,
pivoting on the rear wheels. The board's center of mass is rising, so
it's got upward inertia. It's also got rotational inertia, i.e. it's
starting to do a backwards somersault. But a split second later, the
skater's up-in-the-air foot applies downward force at the front half
of the board to level it and stop that backwards rotation. So in that
way, a pair of downward forces can produce upward motion of the board.

So how much of this applies to jumping a flat pedaled bike?
Certainly, the mass of the rider moves upward. But unlike the
skateboard, he certainly applies a direct upward pull on the
handlebars as his own body mass rises. That's easy to feel, and easy
to see in the videos.

But so far, all that's got us is a wheelie. Does the rider then push
either forward on the bars (as Joe says) or downward on the bars
(corresponding to the finish of the skateboard trick)? Seems either
might work. And what, if anything, happens with the feet?

It's raining pretty hard here right now, or I'd go out and play around
trying to feel what I'm doing. But again, I'm hampered by simple lack
of skill. I have to sense the forces during the brief duration of my
tiny flat pedal bunny hop. Maybe someone more skilled can use their
longer air time to analyze this?

- Frank Krygowski

On Oct 7, 11:14*am, Dan O wrote:

It kind of cracks me up that Frank keeps his straps loose for
virtually no backward retention, thinks the retention is where he
applies force to bunnyhop, then thinks the force he applies is
backward at the pedal.

I believe the foot technique is much different with my clips-and-
straps pedals, compared to my flat pedals. Certainly, the height I
can get is much different.

I just posted speculation about how a flat pedal bunny hop is done,
which is not saying I understand it completely. As I said, with flat
pedals I get the sensation of clawing upward and backward with my toes-
pointed-downward feet. Maybe that's an illusion, I don't know.

But when I do a hop with clips and straps, that "backward" sensation
is absent, and my toes don't point down at all. What I feel is much
simpler: I jump my body upward, then I pull the bike upward after
myself, exerting upward force on the bars (with my hands) and the
pedal straps (with my feet).

I've done that so many hundreds of times for so many years, with
anything from an empty bike to a commuting bike with variously loaded
briefcases, that I'd be astonished at proof that I'm not pulling
directly upward on those straps.

- Frank Krygowski

On 10/7/2012 2:34 PM, Frank Krygowski wrote:
On Oct 7, 11:14 am, Dan O wrote:

It kind of cracks me up that Frank keeps his straps loose for
virtually no backward retention, thinks the retention is where he
applies force to bunnyhop, then thinks the force he applies is
backward at the pedal.

I believe the foot technique is much different with my clips-and-
straps pedals, compared to my flat pedals. Certainly, the height I
can get is much different.

I just posted speculation about how a flat pedal bunny hop is done,
which is not saying I understand it completely. As I said, with flat
pedals I get the sensation of clawing upward and backward with my toes-
pointed-downward feet. Maybe that's an illusion, I don't know.

But when I do a hop with clips and straps, that "backward" sensation
is absent, and my toes don't point down at all. What I feel is much
simpler: I jump my body upward, then I pull the bike upward after
myself, exerting upward force on the bars (with my hands) and the
pedal straps (with my feet).

I've done that so many hundreds of times for so many years, with
anything from an empty bike to a commuting bike with variously loaded
briefcases, that I'd be astonished at proof that I'm not pulling
directly upward on those straps.

- Frank Krygowski



https://www.youtube.com/results?sear....1.Zb5U9aCBNPE

or

http://preview.tinyurl.com/99p39s2

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

Frank Krygowski writes:

On Oct 7, 1:59Â*am, Joe Riel wrote:
Dan O writes:
On Oct 6, 4:09 pm, Frank Krygowski wrote:
On Oct 6, 3:01 pm, Jay Beattie wrote:

On Oct 6, 10:53 am, Frank Krygowski wrote:

I usually have my straps set at a sort of compromise length, loose
enough to flip into very quickly, but tight enough to provide just a
bit of security against foot slips. Â*They're tight enough that I can
bunny hop, which is good enough for me.

Based on all the trick riding I see, you don't need to be clipped in
to bunny hop the bike -- but I find it hard to do on a road bike
without clips, so I must be a flounder...

I just tried it, to be sure of my memory. Â*As I thought, I can get the
rear wheel up just a little, maybe a couple inches, on a bike without
clips. Â*That's my retro 3 speed. Â*I seem to be pushing a bit rearward
on the pedals to do it, which seems to be the same thing I see in
videos likehttp://www.youtube.com/watch?v=Z19zFlPah-o

Look at ~2:00. See how his weight goes way back to lift the front end,
then, springing off the pedals, he leaps into the air, chasing the
front end with his body mass, until the handlebars are in his lap.
The rear wheel is still on the ground. Â*Then he fluidly but
instantaneously transfers his body's inertia to the bike via the
handlebars. Â*See how his elbows and knees - fully extended a fraction
of a second before - are bent at the top and the bike has come up
underneath him? Â*There's no lifting it by the pedals.

I don't know if I've really got it figured out, but for me I think
it's almost all through the handlebars.

An impulsive force applied to the handlebars and in a direction directly
away from the center of mass of the bike will do the trick. Â*To verify
that, stand in front of the bike and apply such an impulse; both wheels
will leave the ground simultaneously. Â*Alas, applying the same impulsive
force while riding the bike is quite awkward (try it, you'll see). Â*The
way I believe it is done is in two steps: an upward pull, then a forward
push. Â*Those can be efficiently applied and since the average direction
of the two force is through the CoM the result is nearly the same.

That sounds like a possibility to me. However, when I do it on a flat
pedal bike, I certainly get the impression my feet are pushing a bit
backward on the pedals, and sort of trying to claw them upward, with
my toes pointed downward. I'm trying to understand that sensation.
(In the videos, it looks like the rider's toes are pointed down, too.)

I'll get more serious than I was a couple posts ago (since nobody
really repeals the law of gravity):

To understand a bike being bunny hopped, I think it may help to think
about how a skateboard is bunny hopped. The processes aren't the same
(there's obviously no direct upward pull from the shoes on the
skateboard) but I think there are some similarities.

As I understand it, the skater jumps his own body mass upward. That's
easy. And he'll soon lift his legs upward after his main body mass.
But (nearly) simultaneously with the initial jump, he kicks down on
the tail of the board. That levers the rest of the board upward,
pivoting on the rear wheels. The board's center of mass is rising, so
it's got upward inertia. It's also got rotational inertia, i.e. it's
starting to do a backwards somersault. But a split second later, the
skater's up-in-the-air foot applies downward force at the front half
of the board to level it and stop that backwards rotation. So in that
way, a pair of downward forces can produce upward motion of the board.

So how much of this applies to jumping a flat pedaled bike?
Certainly, the mass of the rider moves upward. But unlike the
skateboard, he certainly applies a direct upward pull on the
handlebars as his own body mass rises. That's easy to feel, and easy
to see in the videos.

But so far, all that's got us is a wheelie. Does the rider then push
either forward on the bars (as Joe says) or downward on the bars
(corresponding to the finish of the skateboard trick)? Seems either
might work. And what, if anything, happens with the feet?

It's raining pretty hard here right now, or I'd go out and play around
trying to feel what I'm doing. But again, I'm hampered by simple lack
of skill. I have to sense the forces during the brief duration of my
tiny flat pedal bunny hop. Maybe someone more skilled can use their
longer air time to analyze this?

- Frank Krygowski

Something I did a dozen years or so ago was to stand on two low
sawhorses, one on each side of the bike, and from there test stategies
for yanking on the bars. That made experimenting easy. Doing so showed
me that it really wasn't practical to get the rear wheels off the ground
with a uni-direction yank; our body really isn't designed to do
that in the required direction. Nor was was yanking while applying a
torque to the bars (something I'd heard) feasible, at least not for me.
What did work was the lift and push.

I won't be attempting bunny hops any time soon. A month ago the front
wheel slid in a corner I've rounded a thousand times (downhill, slightly
offcamber). Don't know what I did wrong; I always go around the corner
aggressively, but assumed I had a reasonable safety margin. Apparently
the margin was exceeded. Cleanly broke the trochanter. Now I'm
sporting a 10 inch rod in the femur with a four inch screw through
trochanter. Have been walking with a cane for about two weeks now
(that's better than using a walker). Need to do something for an
aerobic workout, probably will be using the rowing machine for a awhile,
though could try the turbo-trainer.


--
Joe Riel

bummmer...the greater or lesser trochanter ? yawl losing bone mass ?

did you try spinning thru getting off into the part 2 hop from bottom spin ?

the Utubers are terrific,,,fluid.

On Sunday, October 7, 2012 4:17:00 PM UTC-4, AMuzi wrote:
On 10/7/2012 2:34 PM, Frank Krygowski wrote:

On Oct 7, 11:14 am, Dan O wrote:



It kind of cracks me up that Frank keeps his straps loose for

virtually no backward retention, thinks the retention is where he

applies force to bunnyhop, then thinks the force he applies is

backward at the pedal.



I believe the foot technique is much different with my clips-and-

straps pedals, compared to my flat pedals. Certainly, the height I

can get is much different.



I just posted speculation about how a flat pedal bunny hop is done,

which is not saying I understand it completely. As I said, with flat

pedals I get the sensation of clawing upward and backward with my toes-

pointed-downward feet. Maybe that's an illusion, I don't know.



But when I do a hop with clips and straps, that "backward" sensation

is absent, and my toes don't point down at all. What I feel is much

simpler: I jump my body upward, then I pull the bike upward after

myself, exerting upward force on the bars (with my hands) and the

pedal straps (with my feet).



I've done that so many hundreds of times for so many years, with

anything from an empty bike to a commuting bike with variously loaded

briefcases, that I'd be astonished at proof that I'm not pulling

directly upward on those straps.



- Frank Krygowski







https://www.youtube.com/results?sear....1.Zb5U9aCBNPE



or



http://preview.tinyurl.com/99p39s2



--

Andrew Muzi

www.yellowjersey.org/

Open every day since 1 April, 1971

Sure looks like the front wheel comes off high first and then the rear wheel is raised by rotating the rear end up which is aided by the low air pressure in the tire.

Cheers