Not your typical tires

Tim McNamara wrote:

I think it is believed to be a spring similar to the belief that
the curl in fork blades are springs.

There has been some published data measuring vertical flex of
bicycle fork blades under load. This flex was measured to be
greater in forks with larger offset and a lower, tighter curl at the
hub end; also, naturally enough, smaller diameter fork blades showed
more flex. The magnitude was small, maybe 1/4" at most. Whether
it's *useful* is a different story; the authors of the article
believed it was but I can't say that I was convinced. For one
thing, the load was static with weights applied to the front of the
bike.

I think static loads are appropriate for such measurements. As I
mentioned in another thread, speed of application of forces is
immaterial for structural metals.

No doubt forks flex but not enough to constitute a spring, certainly
not as much as the pneumatic tire furnishes. Most of the flex in
forks takes place in the steertube that generally has a lower bending
stiffness than the two fork blades it supports and whose bending load
is pivoted about the lower head bearing. This also causes fretting
damage to the lower and upper head bearing.

Time's a little tight this morning, I'll dig up the article and post
more specifics.

I'm curious what the goal of this study was.

Jobst Brandt

On 02 Nov 2008 11:56:11 GMT, wrote:

Carl Sundquist wrote:

Ignore the oval chain ring:

http://tinyurl.com/66ztbn

Look closely at the front tire at 1 & 7 o'clock.

Look _very_ closely at the rear tire at 1 & 3 o'clock.

Aren't you glad that your choices are limited to tubulars and
clinchers?

Solid non-pneumatic rubber tires are all they had for high wheelers
and that drifted into the safety bicycle, this one apparently by
Iver Johnson. I had a later IJ that had triangular taper BB and
steel cranks. Realizing that the torsional strength of a shaft is
roughly that of the largest inscribed circular shaft, a triangle
doesn't leave much and with steel cranks had a poor retaining bolt
to boot.

Is that not a valve at 7 o'clock on the front wheel?

I think that is where a valve wold go for a pneumatic tire, but these
may be tire anchor screws to keep the solid tire from walking around
the wheel and dismounting itself. I can't see any detail in the large
gap in these tires to see thier cross section but it seems to be
mostly solir rubber.

On another note, what was the benefit of the serpentine seatpost?

I think it is believed to be a spring similar to the belief that the
curl in fork blades are springs.

Jobst Brandt

Dear Jobst,

Both tire valves are visible if you look closely. The rear valve, at 3
o'clock, is almost obscured by the chain stays. Here's the original
page of photos:
http://tinyurl.com/66ztbn

You can see the valve caps on both valves. Here they are, cropped from
three photos and enlarged:
http://i33.tinypic.com/se885v.jpg

The holes for the valves are at the riveted rim joint.

Someone may have taken the old pneumatic tires and tubes off, leaving
the valves in place, and installed "cushion" tires as described in the
auction text. Cushion tires were hollow, but not inflatable, so they
flexed and wore rapidly.

I'd love to see the actual bike and find out exactly what's going on.

***

As for the odd seat post, that was just one early shape. It looks
strange to us, but it was cheap, easy, and simple to bend a solid rod
like that:

http://www.auctionflex.com/auctionim..._2BX0U29PG.jpg

http://www.auctionflex.com/auctionim..._2BX0U2N4Y.jpg

It's very easy to get at the clamping bolt under the seat and then
slide the seat back and forth on its long level section to suit the
rider.

Cheers,

Carl Fogel

Carl Sundquist wrote:

Ignore the oval chain ring:

http://tinyurl.com/66ztbn

Look closely at the front tire at 1 & 7 o'clock.

Look _very_ closely at the rear tire at 1 & 3 o'clock.

Aren't you glad that your choices are limited to tubulars and
clinchers?

Solid non-pneumatic rubber tires are all they had for high
wheelers and that drifted into the safety bicycle, this one
apparently by Iver Johnson. I had a later IJ that had triangular
taper BB and steel cranks. Realizing that the torsional strength
of a shaft is roughly that of the largest inscribed circular
shaft, a triangle doesn't leave much and with steel cranks had a
poor retaining bolt to boot.

Is that not a valve at 7 o'clock on the front wheel?

I think that is where a valve wold go for a pneumatic tire, but
these may be tire anchor screws to keep the solid tire from walking
around the wheel and dismounting itself. I can't see any detail in
the large gap in these tires to see their cross section but it
seems to be mostly solid rubber.

On another note, what was the benefit of the serpentine seatpost?

I think it is believed to be a spring similar to the belief that
the curl in fork blades are springs.

Both tire valves are visible if you look closely. The rear valve,
at 3 o'clock, is almost obscured by the chain stays. Here's the
original page of photos:

http://tinyurl.com/66ztbn

You can see the valve caps on both valves. Here they are, cropped
from three photos and enlarged:

http://i33.tinypic.com/se885v.jpg

The holes for the valves are at the riveted rim joint.

Someone may have taken the old pneumatic tires and tubes off,
leaving the valves in place, and installed "cushion" tires as
described in the auction text. Cushion tires were hollow, but not
inflatable, so they flexed and wore rapidly.

That was my suspicion, considering the non-pneumatic tires.

I'd love to see the actual bike and find out exactly what's going on.

***

As for the odd seat post, that was just one early shape. It looks
strange to us, but it was cheap, easy, and simple to bend a solid
rod like that:

http://www.auctionflex.com/auctionim..._2BX0U29PG.jpg

http://www.auctionflex.com/auctionim..._2BX0U2N4Y.jpg

It's very easy to get at the clamping bolt under the seat and then
slide the seat back and forth on its long level section to suit the
rider.

Thanks for the details. I find these bicycle interesting because they
often reveal that the ancients were up against difficult design
problems and found solutions that are often missing today.

Jobst Brandt

On 02 Nov 2008 20:27:05 GMT, wrote:

Carl Sundquist wrote:

Ignore the oval chain ring:

http://tinyurl.com/66ztbn

Look closely at the front tire at 1 & 7 o'clock.

Look _very_ closely at the rear tire at 1 & 3 o'clock.

Aren't you glad that your choices are limited to tubulars and
clinchers?

Solid non-pneumatic rubber tires are all they had for high
wheelers and that drifted into the safety bicycle, this one
apparently by Iver Johnson. I had a later IJ that had triangular
taper BB and steel cranks. Realizing that the torsional strength
of a shaft is roughly that of the largest inscribed circular
shaft, a triangle doesn't leave much and with steel cranks had a
poor retaining bolt to boot.

Is that not a valve at 7 o'clock on the front wheel?

I think that is where a valve wold go for a pneumatic tire, but
these may be tire anchor screws to keep the solid tire from walking
around the wheel and dismounting itself. I can't see any detail in
the large gap in these tires to see their cross section but it
seems to be mostly solid rubber.

On another note, what was the benefit of the serpentine seatpost?

I think it is believed to be a spring similar to the belief that
the curl in fork blades are springs.

Both tire valves are visible if you look closely. The rear valve,
at 3 o'clock, is almost obscured by the chain stays. Here's the
original page of photos:

http://tinyurl.com/66ztbn

You can see the valve caps on both valves. Here they are, cropped
from three photos and enlarged:

http://i33.tinypic.com/se885v.jpg

The holes for the valves are at the riveted rim joint.

Someone may have taken the old pneumatic tires and tubes off,
leaving the valves in place, and installed "cushion" tires as
described in the auction text. Cushion tires were hollow, but not
inflatable, so they flexed and wore rapidly.

That was my suspicion, considering the non-pneumatic tires.

I'd love to see the actual bike and find out exactly what's going on.

***

As for the odd seat post, that was just one early shape. It looks
strange to us, but it was cheap, easy, and simple to bend a solid
rod like that:

http://www.auctionflex.com/auctionim..._2BX0U29PG.jpg

http://www.auctionflex.com/auctionim..._2BX0U2N4Y.jpg

It's very easy to get at the clamping bolt under the seat and then
slide the seat back and forth on its long level section to suit the
rider.

Thanks for the details. I find these bicycle interesting because they
often reveal that the ancients were up against difficult design
problems and found solutions that are often missing today.

Jobst Brandt

Dear Jobst,

Here's another example of what Carl Sundquist called the serpentine
seat post:

http://www.auctionflex.com/showlot.a...ction=&lang=En
or http://tinyurl.com/67eka4

With no seat in the way, it's easier to see how the post worked.

Other companies used wooden-spoke wheels, too. Here's another
wooden-spoke bike, with the original wheels included in the auction:

http://www.auctionflex.com/showlot.a...ction=&lang=En
or http://tinyurl.com/5lflhe

This photo shows how early safety bicycle makers were still scratching
their heads over frame design:

http://www.auctionflex.com/auctionim..._21D1FEP66.jpg

You can just barely make out the rear sprocket on the other side of
the flip-flop hub mentioned in the auction text.

I'm impressed with the notion that a lady circa 1891 was going to stop
at the bottom of a hill and flip her rear wheel around for a lower
gear.

Cheers,

Carl Fogel

On Sun, 02 Nov 2008 19:10:48 +0000, jobst.brandt wrote:

Tim McNamara wrote:

I think it is believed to be a spring similar to the belief that the
curl in fork blades are springs.

There has been some published data measuring vertical flex of bicycle
fork blades under load. This flex was measured to be greater in forks
with larger offset and a lower, tighter curl at the hub end; also,
naturally enough, smaller diameter fork blades showed more flex. The
magnitude was small, maybe 1/4" at most. Whether it's *useful* is a
different story; the authors of the article believed it was but I can't
say that I was convinced. For one thing, the load was static with
weights applied to the front of the bike.

I think static loads are appropriate for such measurements. As I
mentioned in another thread, speed of application of forces is
immaterial for structural metals.

er, given the fact that deformation at low strain rates does indeed differ
from that of high strain rates, that's a ridiculous blanket statement
jobst.



No doubt forks flex but not enough to constitute a spring, certainly not
as much as the pneumatic tire furnishes.

ah, that old saw, which contradicted by...



Most of the flex in forks
takes place in the steertube

so what do you want jobst? elasticity or no elasticity? can't pick and
choose you know.


that generally has a lower bending
stiffness than the two fork blades it supports and whose bending load is
pivoted about the lower head bearing. This also causes fretting damage
to the lower and upper head bearing.

jobst, you don't even know what fretting is. otherwise you wouldn't
confuse it with brinelling.



Time's a little tight this morning, I'll dig up the article and post
more specifics.

I'm curious what the goal of this study was.

i'm curious as to whether you ever had a goal of studying.