Seat angle?

Ken Marcet said:

I am designing a new seat for my homebuilt SWB above seat steering bike, and
am a bit curious about what kind of angle people have on thier bents. I am
thinking that not too much more than 20 to 30 degrees off of the vertical
line would probably be a good angle to start with. Any comments of feedback
is welcome.

Where is the bottom bracket/crank spindle (BB) in relation to the seat?
The appropriate range of seat recline angles can not be determined
without this information.

Normal convention is to measure seat recline angle from an imaginary
horizontal plane. Therefore, a Tour Easy might have a seat recline angle
of 70 degrees, while a NoCom would have a seat recline angle near 20
degrees.

--
Tom Sherman

"Tom Sherman" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Ken Marcet said:

I am designing a new seat for my homebuilt SWB above seat steering bike,

and

Quoted message said:

Quoted message said:

am a bit curious about what kind of angle people have on thier bents. I

am

Quoted message said:

Quoted message said:

thinking that not too much more than 20 to 30 degrees off of the

vertical

Quoted message said:

Quoted message said:

line would probably be a good angle to start with. Any comments of

feedback

Quoted message said:

Quoted message said:

is welcome.

Where is the bottom bracket/crank spindle (BB) in relation to the seat?
The appropriate range of seat recline angles can not be determined
without this information.

Okay well I didn't know that, this bike is still in the construction stage
and the final position of the bb/spindle has not been set into stone,
however according to my design plans the spindle will be about 1 & 1/2 to 2
inches above the seating surface.

Ken

Quoted message said:

Normal convention is to measure seat recline angle from an imaginary
horizontal plane. Therefore, a Tour Easy might have a seat recline angle
of 70 degrees, while a NoCom would have a seat recline angle near 20
degrees.

--
Tom Sherman

On Fri, 24 Dec 2004 07:01:40 -0500, "Ken Marcet" <[email hidden]>

wrote in message : said:

I am designing a new seat for my homebuilt SWB above seat steering bike, and
am a bit curious about what kind of angle people have on thier bents. I am
thinking that not too much more than 20 to 30 degrees off of the vertical
line would probably be a good angle to start with.

Do you mean off the horizontal line? I usually ride with my seat 30º
above horizontal on my SWB OSS bike.

"Just zis Guy, you know?" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On Fri, 24 Dec 2004 07:01:40 -0500, "Ken Marcet" <[email hidden]>

wrote in message : said:

I am designing a new seat for my homebuilt SWB above seat steering bike,

and

Quoted message said:

Quoted message said:

am a bit curious about what kind of angle people have on thier bents. I

am

Quoted message said:

Quoted message said:

thinking that not too much more than 20 to 30 degrees off of the vertical
line would probably be a good angle to start with.

Do you mean off the horizontal line? I usually ride with my seat 30º
above horizontal on my SWB OSS bike.

Wow you ride pretty darn flat, no my original thinking was I guess more
along the lines of a "semi" recumbent seat, because I was thinking 20 to 30
degrees off the vertical so I guess that would be 110 to 120 from the base
of the seat which will be parralell to the ground.

On Fri, 24 Dec 2004 07:33:47 -0500, "Ken Marcet" <[email hidden]>

wrote in message : said:

Quoted message said:

Do you mean off the horizontal line? I usually ride with my seat 30º
above horizontal on my SWB OSS bike.

Quoted message said:

Wow you ride pretty darn flat, no my original thinking was I guess more
along the lines of a "semi" recumbent seat, because I was thinking 20 to 30
degrees off the vertical so I guess that would be 110 to 120 from the base
of the seat which will be parralell to the ground.

I don't think that's remarkably flat, actually. SWB OSS bikes with
the BB above the seat are often set up this way, I think.

http://www.hpvelotechnik.com/
http://www.optimabikes.com/
http://www.challengebikes.com/

My view may be distorted by a Euro perspective (my bike is an Optima
Stinger), but most of the SWB OSS BB above seat bikes on these sites
seem to have seat angles well below 45º - any more upright and you
start to be too bent up to breathe properly (in my view anyway).

"Ken Marcet" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

"Just zis Guy, you know?" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On Fri, 24 Dec 2004 07:01:40 -0500, "Ken Marcet" <[email hidden]>

wrote in message : said:

I am designing a new seat for my homebuilt SWB above seat steering bike,

and

Quoted message said:

Quoted message said:

am a bit curious about what kind of angle people have on thier bents. I

am

Quoted message said:

Quoted message said:

thinking that not too much more than 20 to 30 degrees off of the
vertical
line would probably be a good angle to start with.

Do you mean off the horizontal line? I usually ride with my seat 30º
above horizontal on my SWB OSS bike.

Wow you ride pretty darn flat, no my original thinking was I guess more
along the lines of a "semi" recumbent seat, because I was thinking 20 to
30
degrees off the vertical so I guess that would be 110 to 120 from the base
of the seat which will be parralell to the ground.

Ken, horizontal is zero°. The origin is considered to be the your front
wheel with a direction vector towards your back wheel. This should get us
all talking in the same geometrical universe. Vertical would be 90°. At 110°
to 120° you would have your face in your crotch. 20° to 30° from vertical
would be 60° to 70° from horizontal. I think 45° is quite vertical enough
for a recumbent, and even at that you would carry a lot of weight on your
buns. The euro designers keep the seat back angle low so the big muscle
group up your back carries the body mass, and the glutes are free from
compression so you can get some power to the pedals.

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Ken Marcet said:

Okay well I didn't know that, this bike is still in the construction stage
and the final position of the bb/spindle has not been set into stone,
however according to my design plans the spindle will be about 1 & 1/2 to
2 inches above the seating surface.

Not really a high BB, but certainly not low. At 70deg from vertical you
are going to be folded over like Lance in full aero-tuck TT mode. If you
want to get an idea of what the commercial builders do, you'll find
details of seat angle(s), height and BB height for all the models of Trice
(Guy knows why I've been drooling here this afternoon), at
http://www.ice.hpv.co.uk/

You'll find that for speed the angle can be as low as 20deg from
horizontal, and at the "upright" end of the touring range, 50deg from
horizontal.

HTH

Mike

Mike Causer said:

Ken Marcet said:

Okay well I didn't know that, this bike is still in the construction stage
and the final position of the bb/spindle has not been set into stone,
however according to my design plans the spindle will be about 1 & 1/2 to
2 inches above the seating surface.

Not really a high BB, but certainly not low. At 70deg from vertical you
are going to be folded over like Lance in full aero-tuck TT mode. If you
want to get an idea of what the commercial builders do, you'll find
details of seat angle(s), height and BB height for all the models of Trice
(Guy knows why I've been drooling here this afternoon), at
http://www.ice.hpv.co.uk/

I believe the second sentence of the paragraph quoted directly above
should read "At 70deg from [horizontal]. This would be the position
favored by those who ride bikes from Lighting Cycle Dynamics. Certain
riders with "aerobellies" have complained about thigh to abdomen contact
while riding a P-38.

My RANS Rocket has the bottom bracket about 2 inches above the seat [1],
similar to what Ken Marcet is proposing for his homebuilt, and I have
the seat reclined at about 55 degrees from horizontal. This is about as
reclined as I would want to be before the hip angle becomes too open for
climbing and sprinting effectively. [2] Seat comfort has been fine for
me for rides up to 7 hours per day [3] - but as always YMMV.

[1] Using an estimated level of seat foam compression.
[2] Owners of ATP Vision SWB bikes may disagree, since they have a very
open hip angle.
[3] The farthest I have ridden the Rocket in one day is about 110 miles
(~180 km).

--
Tom Sherman

Arky Meedese said:

...
Ken, horizontal is zero?. The origin is considered to be the your front
wheel with a direction vector towards your back wheel. This should get us
all talking in the same geometrical universe. Vertical would be 90?. At 110?
to 120? you would have your face in your crotch...

From photographs, the Gold Rush [1] seat angle appears to be near 100
degrees (using the standard reference), as does the seat of the Cheetah.
However, these bikes were designed for maximizing sprinting power during
speed record attempts, and not for rider comfort.

[1] Not to be confused with the Gold Rush Replica, which is the
commercially sold bike that is a slightly modified of the Gold Rush chassis.

--
Tom Sherman

Ken Marcet said:

"Just zis Guy, you know?" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On Fri, 24 Dec 2004 07:01:40 -0500, "Ken Marcet" <[email hidden]>

wrote in message : said:

I am designing a new seat for my homebuilt SWB above seat steering bike,

and

Quoted message said:

Quoted message said:

am a bit curious about what kind of angle people have on thier bents. I

am

Quoted message said:

Quoted message said:

thinking that not too much more than 20 to 30 degrees off of the vertical
line would probably be a good angle to start with.

Do you mean off the horizontal line? I usually ride with my seat 30º
above horizontal on my SWB OSS bike.

Wow you ride pretty darn flat, no my original thinking was I guess more
along the lines of a "semi" recumbent seat, because I was thinking 20 to 30
degrees off the vertical so I guess that would be 110 to 120 from the base
of the seat which will be parralell to the ground.

30 degrees from the horizontal is way upright. 😉 See
<http://www.wisil.recumbents.com/wisil/costin/fmonkey.jpg> for a
reclined bike. 🙂

--
Tom Sherman – Near Rock Island

"Tom Sherman" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Mike Causer said:

Ken Marcet said:

Okay well I didn't know that, this bike is still in the construction
stage
and the final position of the bb/spindle has not been set into stone,
however according to my design plans the spindle will be about 1 & 1/2 to
2 inches above the seating surface.

Not really a high BB, but certainly not low. At 70deg from vertical you
are going to be folded over like Lance in full aero-tuck TT mode. If you
want to get an idea of what the commercial builders do, you'll find
details of seat angle(s), height and BB height for all the models of
Trice
(Guy knows why I've been drooling here this afternoon), at
http://www.ice.hpv.co.uk/

I believe the second sentence of the paragraph quoted directly above
should read "At 70deg from [horizontal]. This would be the position
favored by those who ride bikes from Lighting Cycle Dynamics. Certain
riders with "aerobellies" have complained about thigh to abdomen contact
while riding a P-38.

I do not have an aerobelly and I found the P-38 far from ideal as regards
the hip angle. I do not like to be that crouched over.

Quoted message said:

My RANS Rocket has the bottom bracket about 2 inches above the seat [1],
similar to what Ken Marcet is proposing for his homebuilt, and I have the
seat reclined at about 55 degrees from horizontal. This is about as
reclined as I would want to be before the hip angle becomes too open for
climbing and sprinting effectively. [2] Seat comfort has been fine for me
for rides up to 7 hours per day [3] - but as always YMMV.

Mr. Sherman is quite right about the importance of the hip angle. A more
open angle will increase comfort and a more closed angle will increase power
to the pedal.

Quoted message said:

[1] Using an estimated level of seat foam compression.
[2] Owners of ATP Vision SWB bikes may disagree, since they have a very
open hip angle.

You can vary the seat angle on the Vision quite a bit. I can get it so
closed that I do not like it. But I do admit I much prefer an open hip
angle, even if it impacts power to the pedal.

Quoted message said:

[3] The farthest I have ridden the Rocket in one day is about 110 miles
(~180 km).

Yes, I find about 100 miles is sufficient on any bike for one day. The
Vision seat will keep you comfortable no matter how many miles. But I do not
like to do centuries. After about 70 miles I have had it!

--
Regards,

Ed Dolan - Minnesota

Tom Sherman said:

Quoted message said:

Not really a high BB, but certainly not low. At 70deg from vertical you
are going to be folded over like Lance in full aero-tuck TT mode. If
you want to get an idea of what the commercial builders do, you'll find
details of seat angle(s), height and BB height for all the models of
Trice (Guy knows why I've been drooling here this afternoon), at
http://www.ice.hpv.co.uk/

I believe the second sentence of the paragraph quoted directly above
should read "At 70deg from [horizontal].

Yes, you're right.

Quoted message said:

My RANS Rocket has the bottom bracket about 2 inches above the seat [1],
similar to what Ken Marcet is proposing for his homebuilt, and I have the
seat reclined at about 55 degrees from horizontal.

My Speed Ross has BB 1.5cm above seat bottom (therefore in similar range),
and is at 41.5deg to horizontal. I'd call it a comfortable bike for
touring, despite the name. I've ridden more laid-back trikes and found
them no problem, probably in the 30degree range, but I know from
driving cars at around 20-25deg that vision gets to be a problem down
there.

Quoted message said:

This is about as reclined as I would want to be before the hip angle
becomes too open for climbing and sprinting effectively.

A runner is operating at what we would call 0deg from horizontal, and they
don't seem to have a problem. Having been a cyclist for so long I cannot
run more than a few steps now, so I think that the problem with "open"
positions is a matter of how the muscles have been trained. (As with the
advice to give the muscles time to adapt in the transition from upright to
'bent.)

Quoted message said:

[1] Using an estimated level of seat foam compression.

What is this "foam" of which you speak? ;-)

Mike

Mike Causer said:

On Fri, 24 Dec 2004 11:59:44 -0600, Tom Sherman wrote:
...

Quoted message said:

This is about as reclined as I would want to be before the hip angle
becomes too open for climbing and sprinting effectively.

A runner is operating at what we would call 0deg from horizontal, and they
don't seem to have a problem. Having been a cyclist for so long I cannot
run more than a few steps now, so I think that the problem with "open"
positions is a matter of how the muscles have been trained. (As with the
advice to give the muscles time to adapt in the transition from upright to
'bent.)

I am close to vertical when running on flat or moderate grades, but lean
forward considerably when running up steps or steep hills.

Quoted message said:

Quoted message said:

[1] Using an estimated level of seat foam compression.

What is this "foam" of which you speak? ;-)

Fourth item from the bottom on this web page:
<http://www.shoprans.com/Seat.asp>.

--
Tom Sherman – Near Rock Island

Have a look...

asme.pinetec.com/bio1999/data/pdfs/a0090747.pdf

db said:

Have a look...

asme.pinetec.com/bio1999/data/pdfs/a0090747.pdf

Which demonstrates that most power is developed at the trunk/leg angle you
are accustomed to, and says nothing about the best position after
developing the muscles for it.

Mike

It's on-topic experimental data, presented for what it's worth, not intended
to support or refute anything previously said.

I imply no position or argument on my part.

Thought some folks might not have seen it, and might have an interest.

The back angle data from this experiment appears to support a more "open"
seating position, with power (in this experiment) falling off as the "body
configuration" angle (included angle, backbone to thigh) becomes smaller
(e.g. closer to the crouch position.). Maybe this trend extends all the way
to a "zero" back angle, but there is no direct data here to support that
speculation. There's no "fall-off" in the power at the "open" end of the
back angle range in this experiment.

Dr. Too's results support a tighter riding position.

Of course real-world noise can make a lot of these considerations of no
consequence. Like a 5'6" 220 lb. rider paying $100 extra for a 25 gram
lighter crank. 🙂

Doug

"Mike Causer" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

db said:

Have a look...

asme.pinetec.com/bio1999/data/pdfs/a0090747.pdf

Which demonstrates that most power is developed at the trunk/leg angle you
are accustomed to, and says nothing about the best position after
developing the muscles for it.

Mike

"Mike Causer" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

db said:

Have a look...

asme.pinetec.com/bio1999/data/pdfs/a0090747.pdf

Which demonstrates that most power is developed at the trunk/leg angle you
are accustomed to, and says nothing about the best position after
developing the muscles for it.

No muscles ever get "developed" for anything unless you work at it like a
training athlete. Most of us who ride recumbents do so for recreation and
exercise. We are not athletes and our muscles never get "developed." That
being the case, what do you think is the best hip angle for speed and
climbing ability, open or closed? It's OK to use your common sense as you
try to figure this out.

--
Regards,

Ed Dolan - Minnesota

On Sun, 26 Dec 2004 15:37:17 -0600, "Edward Dolan" <[email hidden]>

wrote in message : said:

No muscles ever get "developed" for anything unless you work at it like a
training athlete.

Is the wrong answer. Any regular work that leaves the muscles tired
will develop them to some degree.

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

85% of helmet statistics are made up, 69% of them at CHS, Puget Sound

As an "older rider" I find 28 degrees tolerable, 25 possible and 20 too low.
At 25 I need the neck rest and there are problems because I peer through the
bottom of my multi-focals....

The MR Swiftlet has an adjustable CF seat. It works well from the lower
setting to about 35 degrees. The "European" style CF seats are not designed
to be used at 40 degrees - the bottom of the seat becomes too low, lacking
bum/butt support.

(The BB is relatively low.)

Paul W