Quill seat posts for MTB?

On Sun, 4 Dec 2016 20:32:32 -0500, Frank Krygowski
wrote:

On 12/4/2016 7:12 PM, John B. wrote:
On Sun, 04 Dec 2016 08:11:18 -0800, Joerg
wrote:

On 2016-12-02 16:38, John B. wrote:
On Fri, 02 Dec 2016 09:38:30 -0800, Joerg
wrote:

Folks,

In the old days they were available but can't find modern ones for MTB.

https://www.youtube.com/watch?v=5EkigpkVXLY

Fixing a seat post only at the top (kind of) works for regular bikes
that aren't used on harsh turf but not for MTB with heavy loads. Mine
started creaking to no end and that's probably not good for the frame.
So I am looking for a longer seat post but ideally with quill.

Any hints who still carries that?

Why is clamping the seat post with a clamp at the top actually
different from clamping the seat post at the bottom?


It needs to be clamped at the top _and_ the bottom. If you clamp it only
in one place there will always be an ever so slight rocking. This
produces creaking, wear and most annoyingly a gradual sagging.


Theoretically at least the seat post is supposed to be sliding fit in
the seat tube with minimal play so clamping at one end is very much
the same as clamping at the other.


"Minimal" is the key word here. It cannot be zero and even if it was it
would wear with use. A minimal gap is required in order to get the seat
post in and out and also because of the usual factory tolerances. This
causes minimal rocking back and forth. A quill at the bottom in addition
to the usual clamp at the top will avoid that. Not a new concept, I had
that on an old bike.

Aside from the creaking, no matter how hard I adjusted the top clamp the
only way I could prevent a gradual sag when riding a lot of washboard
turf was to smear toothpaste around the top of the post where it clamps.
Not the gel type for electric brushing but the regular stuff with some
grit in there. Coincidentally that's also how I prevented the MTB stem
from coming loose without exceeding the 5Nm torque limit.

As you mention a friend who is a machinist I suggest that the only
problem with making a seat post is how to tighten the bottom clamp. A
through bolt running from the top of the post to the clamp nut at the
bottom is certainly doable just as the old 1 inch quill stems. Added
to a conventional "top clamp" that should hold the seat post even if
an elephant should sit on it.

The problem comes about because the seat covers the top of the seat
post and makes tightening the quill bold difficult but given that once
the "correct" seat position is determined one doesn't usually
re-adjust he seat frequently it should be easy enough. Just install
the seat using the normal clamp and adjust to fit. Then remove the
seat, tighten the quill bolt and reinstall the seat.

Sounds workable to me.

You know, there is another solution. Simply drill a series of holes in
the seat post, say 1/2" apart. A hole through the seat tube and Bob's
your uncle. Use a 1/4" grade 8 bolt, maybe 735 pounds tensile
strength, probably in the neighborhood of 440 pounds sheer strength.

If one used a "spring cotter" rather than a nut it could even be field
adjustable without tools.

--
cheers,

John B.

Bolt no good...no surface area (s)

On 2016-12-04 22:39, John B. wrote:
On Sun, 4 Dec 2016 20:32:32 -0500, Frank Krygowski
wrote:

On 12/4/2016 7:12 PM, John B. wrote:
On Sun, 04 Dec 2016 08:11:18 -0800, Joerg
wrote:

On 2016-12-02 16:38, John B. wrote:
On Fri, 02 Dec 2016 09:38:30 -0800, Joerg
wrote:

Folks,

In the old days they were available but can't find modern ones for MTB.

https://www.youtube.com/watch?v=5EkigpkVXLY

Fixing a seat post only at the top (kind of) works for regular bikes
that aren't used on harsh turf but not for MTB with heavy loads. Mine
started creaking to no end and that's probably not good for the frame.
So I am looking for a longer seat post but ideally with quill.

Any hints who still carries that?

Why is clamping the seat post with a clamp at the top actually
different from clamping the seat post at the bottom?


It needs to be clamped at the top _and_ the bottom. If you clamp it only
in one place there will always be an ever so slight rocking. This
produces creaking, wear and most annoyingly a gradual sagging.


Theoretically at least the seat post is supposed to be sliding fit in
the seat tube with minimal play so clamping at one end is very much
the same as clamping at the other.


"Minimal" is the key word here. It cannot be zero and even if it was it
would wear with use. A minimal gap is required in order to get the seat
post in and out and also because of the usual factory tolerances. This
causes minimal rocking back and forth. A quill at the bottom in addition
to the usual clamp at the top will avoid that. Not a new concept, I had
that on an old bike.

Aside from the creaking, no matter how hard I adjusted the top clamp the
only way I could prevent a gradual sag when riding a lot of washboard
turf was to smear toothpaste around the top of the post where it clamps.
Not the gel type for electric brushing but the regular stuff with some
grit in there. Coincidentally that's also how I prevented the MTB stem
from coming loose without exceeding the 5Nm torque limit.

As you mention a friend who is a machinist I suggest that the only
problem with making a seat post is how to tighten the bottom clamp. A
through bolt running from the top of the post to the clamp nut at the
bottom is certainly doable just as the old 1 inch quill stems. Added
to a conventional "top clamp" that should hold the seat post even if
an elephant should sit on it.



That is exactly what I was planning to do if I can't find an
off-the-shelf quill post.


The problem comes about because the seat covers the top of the seat
post and makes tightening the quill bold difficult but given that once
the "correct" seat position is determined one doesn't usually
re-adjust he seat frequently it should be easy enough. Just install
the seat using the normal clamp and adjust to fit. Then remove the
seat, tighten the quill bolt and reinstall the seat.

Sounds workable to me.


I'll see if there would be a spot in the top plate that can be drilled
without compromising its integrity. The cone that spreads apart the
newly slit section of the post bottom does not need much force if
shallow-angled and greased. So a 4mm or similar all-thread should suffice.

The MTB is only ridden by me and due to electrical wiring and such the
seat height can't easily be adjusted anyhow. So I'd just mount it like
usual, mark the post and then do the mods. That way the all-thread
pulling in the cone can be tightened and shortened while the seat is
off. If can still be adjusted up and down a bit but the seat would
always have to come off in order to access the tightening nut on the
all-thread.


You know, there is another solution. Simply drill a series of holes in
the seat post, say 1/2" apart. A hole through the seat tube and Bob's
your uncle. Use a 1/4" grade 8 bolt, maybe 735 pounds tensile
strength, probably in the neighborhood of 440 pounds sheer strength.


I am not going to drill the frame :-)

Voids the warranty and who knows what else it could do.


If one used a "spring cotter" rather than a nut it could even be field
adjustable without tools.


A spring latch like on walkers or market umbrellas would prevent the
post from sliding down but not from rocking. Rocking is the key problem
I have, resulting in nasty creaking and probably wear in the frame.

--
Regards, Joerg

http://www.analogconsultants.com/

On Saturday, December 3, 2016 at 12:30:15 AM UTC-8, John B. wrote:
On Fri, 2 Dec 2016 19:09:33 -0800 (PST), Doug Landau

Why is clamping the seat post with a clamp at the top actually
different from clamping the seat post at the bottom?

Theoretically at least the seat post is supposed to be sliding fit in
the seat tube with minimal play so clamping at one end is very much
the same as clamping at the other.

- Because if clamped at the top, the pinch bolt will be under tension, and able to absorb the tension put on it by the post, before the welds can experience it.

Google brandt+pretension

Certainly the pinch bolt is tightened. But is the pinch bolt, in some
manner independent of all else? Just floating there in space absorbing
all stresses and strains imposed on it? Or is it simply a clamp that
transfers loads imposed on it to the bicycle frame.

Is the fact that all seat posts have some minimum insertion limits
important? Given that the seat clamp tension bolt "absorbs the
tension"?
The minimum insertion limit is so that the seatpost doesn't come busting thru the seat tube at its (the seatpost's) bottom edge, not having enough leverage, when pivoting where it exits the seattube, when lateral load is applied at the top of the post.

Remove the pinch bolt, push sideways on the seat, or even forward or back, and the ears that the pinch bolt goes thru will be spread a little bit, right? In other words, the post is trying to make the opening at the top of the seattube an oval, by placing tension on the walls, at the opening, from the inside, right?

I suggest that if tight, the pinch bolt will absorb this tension, which then cannot be experienced by the tube itself, until it exceeds the tension in the pinch bolt.

The pinch bolt simply compresses the seat tube to clamp the seat post
in place and resists further distortion to some extent but force
applied to the seat post is absorbed by the seat tube. Can't be any
other way.

The pinch bolt, once under tension, will prevent whatever it is compressing from experiencing tension from being pushed from the inside. In this case, the lip and upper end of the seat tube.

Can't be any other way.
You are not understanding. https://www.google.com/webhp?sourcei...nsioned+steel+

due to electrical wiring ? the bike or yours ? use the sand stupid

On Sunday, December 4, 2016 at 10:39:53 PM UTC-8, John B. wrote:
On Sun, 4 Dec 2016 20:32:32 -0500, Frank Krygowski
wrote:

On 12/4/2016 7:12 PM, John B. wrote:
On Sun, 04 Dec 2016 08:11:18 -0800, Joerg
wrote:

On 2016-12-02 16:38, John B. wrote:
On Fri, 02 Dec 2016 09:38:30 -0800, Joerg
wrote:

Folks,

In the old days they were available but can't find modern ones for MTB.

https://www.youtube.com/watch?v=5EkigpkVXLY

Fixing a seat post only at the top (kind of) works for regular bikes
that aren't used on harsh turf but not for MTB with heavy loads. Mine
started creaking to no end and that's probably not good for the frame.
So I am looking for a longer seat post but ideally with quill.

Any hints who still carries that?

Why is clamping the seat post with a clamp at the top actually
different from clamping the seat post at the bottom?


It needs to be clamped at the top _and_ the bottom. If you clamp it only
in one place there will always be an ever so slight rocking. This
produces creaking, wear and most annoyingly a gradual sagging.


Theoretically at least the seat post is supposed to be sliding fit in
the seat tube with minimal play so clamping at one end is very much
the same as clamping at the other.


"Minimal" is the key word here. It cannot be zero and even if it was it
would wear with use. A minimal gap is required in order to get the seat
post in and out and also because of the usual factory tolerances. This
causes minimal rocking back and forth. A quill at the bottom in addition
to the usual clamp at the top will avoid that. Not a new concept, I had
that on an old bike.

Aside from the creaking, no matter how hard I adjusted the top clamp the
only way I could prevent a gradual sag when riding a lot of washboard
turf was to smear toothpaste around the top of the post where it clamps.
Not the gel type for electric brushing but the regular stuff with some
grit in there. Coincidentally that's also how I prevented the MTB stem
from coming loose without exceeding the 5Nm torque limit.

As you mention a friend who is a machinist I suggest that the only
problem with making a seat post is how to tighten the bottom clamp. A
through bolt running from the top of the post to the clamp nut at the
bottom is certainly doable just as the old 1 inch quill stems. Added
to a conventional "top clamp" that should hold the seat post even if
an elephant should sit on it.

The problem comes about because the seat covers the top of the seat
post and makes tightening the quill bold difficult but given that once
the "correct" seat position is determined one doesn't usually
re-adjust he seat frequently it should be easy enough. Just install
the seat using the normal clamp and adjust to fit. Then remove the
seat, tighten the quill bolt and reinstall the seat.

Sounds workable to me.

You know, there is another solution. Simply drill a series of holes in
the seat post, say 1/2" apart. A hole through the seat tube and Bob's
your uncle. Use a 1/4" grade 8 bolt, maybe 735 pounds tensile
strength, probably in the neighborhood of 440 pounds sheer strength.

If it bears weight (your pin), it'll ovalize the holes in the seat tube, and be loose and rattle. It will bear weight because, as Gene pointed out, its flat head can't hold against the round tube.

On Sunday, December 4, 2016 at 10:39:53 PM UTC-8, John B. wrote:
On Sun, 4 Dec 2016 20:32:32 -0500, Frank Krygowski
wrote:

On 12/4/2016 7:12 PM, John B. wrote:
On Sun, 04 Dec 2016 08:11:18 -0800, Joerg
wrote:

On 2016-12-02 16:38, John B. wrote:
On Fri, 02 Dec 2016 09:38:30 -0800, Joerg
wrote:

Folks,

In the old days they were available but can't find modern ones for MTB.

https://www.youtube.com/watch?v=5EkigpkVXLY

Fixing a seat post only at the top (kind of) works for regular bikes
that aren't used on harsh turf but not for MTB with heavy loads. Mine
started creaking to no end and that's probably not good for the frame.
So I am looking for a longer seat post but ideally with quill.

Any hints who still carries that?

Why is clamping the seat post with a clamp at the top actually
different from clamping the seat post at the bottom?


It needs to be clamped at the top _and_ the bottom. If you clamp it only
in one place there will always be an ever so slight rocking. This
produces creaking, wear and most annoyingly a gradual sagging.


Theoretically at least the seat post is supposed to be sliding fit in
the seat tube with minimal play so clamping at one end is very much
the same as clamping at the other.


"Minimal" is the key word here. It cannot be zero and even if it was it
would wear with use. A minimal gap is required in order to get the seat
post in and out and also because of the usual factory tolerances. This
causes minimal rocking back and forth. A quill at the bottom in addition
to the usual clamp at the top will avoid that. Not a new concept, I had
that on an old bike.

Aside from the creaking, no matter how hard I adjusted the top clamp the
only way I could prevent a gradual sag when riding a lot of washboard
turf was to smear toothpaste around the top of the post where it clamps.
Not the gel type for electric brushing but the regular stuff with some
grit in there. Coincidentally that's also how I prevented the MTB stem
from coming loose without exceeding the 5Nm torque limit.

As you mention a friend who is a machinist I suggest that the only
problem with making a seat post is how to tighten the bottom clamp. A
through bolt running from the top of the post to the clamp nut at the
bottom is certainly doable just as the old 1 inch quill stems. Added
to a conventional "top clamp" that should hold the seat post even if
an elephant should sit on it.

The problem comes about because the seat covers the top of the seat
post and makes tightening the quill bold difficult but given that once
the "correct" seat position is determined one doesn't usually
re-adjust he seat frequently it should be easy enough. Just install
the seat using the normal clamp and adjust to fit. Then remove the
seat, tighten the quill bolt and reinstall the seat.

Sounds workable to me.

You know, there is another solution. Simply drill a series of holes in
the seat post, say 1/2" apart. A hole through the seat tube and Bob's
your uncle. Use a 1/4" grade 8 bolt, maybe 735 pounds tensile
strength, probably in the neighborhood of 440 pounds sheer strength.

If one used a "spring cotter" rather than a nut it could even be field
adjustable without tools.

--
cheers,

John B.

1/4" ?!? Way overkill. The shear strength of a #6 screw is 1500 Lbs

WELL, I have seen this bolt in post n the bolt bends, the hole ovals...no bearing surface area. 'Like' the post comes loose so....? where's one on the floor off the rack.... hole bolt post ?

Now here's a wannabe mountain ear who goes on abt hammering pins with rocks but a dollop of sand into the post lube ?

1/4" ?!? Way overkill. The shear strength of a #6 screw is 1500 Lbs

a .25 inch bolt in grade 5 is not taking 1500 pounds the way ura gonna use it in the field.

I doahn have the equation for this but that bolt under 75 pounds over 10 miles/700 miles will fail. more surface area. gotta replace bolt.

the old saw is a 6 legged sofa under 4 fat women...calculate pressure under sofa feet vs shinylvinyl/carpet or hardwood flooring.

On Mon, 05 Dec 2016 07:29:09 -0800, Joerg
wrote:

On 2016-12-04 22:39, John B. wrote:
On Sun, 4 Dec 2016 20:32:32 -0500, Frank Krygowski
wrote:

On 12/4/2016 7:12 PM, John B. wrote:
On Sun, 04 Dec 2016 08:11:18 -0800, Joerg
wrote:

On 2016-12-02 16:38, John B. wrote:
On Fri, 02 Dec 2016 09:38:30 -0800, Joerg
wrote:

Folks,

In the old days they were available but can't find modern ones for MTB.

https://www.youtube.com/watch?v=5EkigpkVXLY

Fixing a seat post only at the top (kind of) works for regular bikes
that aren't used on harsh turf but not for MTB with heavy loads. Mine
started creaking to no end and that's probably not good for the frame.
So I am looking for a longer seat post but ideally with quill.

Any hints who still carries that?

Why is clamping the seat post with a clamp at the top actually
different from clamping the seat post at the bottom?


It needs to be clamped at the top _and_ the bottom. If you clamp it only
in one place there will always be an ever so slight rocking. This
produces creaking, wear and most annoyingly a gradual sagging.


Theoretically at least the seat post is supposed to be sliding fit in
the seat tube with minimal play so clamping at one end is very much
the same as clamping at the other.


"Minimal" is the key word here. It cannot be zero and even if it was it
would wear with use. A minimal gap is required in order to get the seat
post in and out and also because of the usual factory tolerances. This
causes minimal rocking back and forth. A quill at the bottom in addition
to the usual clamp at the top will avoid that. Not a new concept, I had
that on an old bike.

Aside from the creaking, no matter how hard I adjusted the top clamp the
only way I could prevent a gradual sag when riding a lot of washboard
turf was to smear toothpaste around the top of the post where it clamps.
Not the gel type for electric brushing but the regular stuff with some
grit in there. Coincidentally that's also how I prevented the MTB stem
from coming loose without exceeding the 5Nm torque limit.

As you mention a friend who is a machinist I suggest that the only
problem with making a seat post is how to tighten the bottom clamp. A
through bolt running from the top of the post to the clamp nut at the
bottom is certainly doable just as the old 1 inch quill stems. Added
to a conventional "top clamp" that should hold the seat post even if
an elephant should sit on it.



That is exactly what I was planning to do if I can't find an
off-the-shelf quill post.


The problem comes about because the seat covers the top of the seat
post and makes tightening the quill bold difficult but given that once
the "correct" seat position is determined one doesn't usually
re-adjust he seat frequently it should be easy enough. Just install
the seat using the normal clamp and adjust to fit. Then remove the
seat, tighten the quill bolt and reinstall the seat.

Sounds workable to me.


I'll see if there would be a spot in the top plate that can be drilled
without compromising its integrity. The cone that spreads apart the
newly slit section of the post bottom does not need much force if
shallow-angled and greased. So a 4mm or similar all-thread should suffice.

I would really suggest something larger. Most
quill" stems use about a 6 mm bolt so perhaps there is a reason :-)

Another point, you seem to be talking about a hollow seat post, split,
with a cone shaped wedge to spread the bottom of the post. This is
going to take a hammer to drive out if you ever try to move the seat
post and I doubt that a 4mm bolt the length of the seat post is going
to suffice.



The MTB is only ridden by me and due to electrical wiring and such the
seat height can't easily be adjusted anyhow. So I'd just mount it like
usual, mark the post and then do the mods. That way the all-thread
pulling in the cone can be tightened and shortened while the seat is
off. If can still be adjusted up and down a bit but the seat would
always have to come off in order to access the tightening nut on the
all-thread.


You know, there is another solution. Simply drill a series of holes in
the seat post, say 1/2" apart. A hole through the seat tube and Bob's
your uncle. Use a 1/4" grade 8 bolt, maybe 735 pounds tensile
strength, probably in the neighborhood of 440 pounds sheer strength.


I am not going to drill the frame :-)

Voids the warranty and who knows what else it could do.


If one used a "spring cotter" rather than a nut it could even be field
adjustable without tools.


A spring latch like on walkers or market umbrellas would prevent the
post from sliding down but not from rocking. Rocking is the key problem
I have, resulting in nasty creaking and probably wear in the frame.
--
cheers,

John B.