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optimistx
August 9th 03, 06:04 AM
Is seat suspension enough?

It is relatively complicated to have suspension in a bike so that front and
back are suspended with independent systems.

Is it really useful and necessary to do so in recumbents? Is it enough for
all practical purposes to suspend the seat only?

If in an upright bike you suspend the seat to move softly up and down, you
assumably get movement in accordance of pedaling, 'pogo'. The direction of
forces in legs is down. If the total force to the pedals in vertical
direction diminishes, the seat goes down. When it increases, it goes up. The
weight distribution of the driver varies between the pedals and the seat,
causing irritating movement up and down.

But in a recumbent there should be no 'pogo' in the vertical direction! ?

If the seat is prevented to move in a horizontal direction (forward and
backward, and side to side) but is free to move up and down within limits,
suspended, there seems to be a possibility to have one suspension system
instead of two and get almost as good results as with two.

Almost?

The suspended mass in this system is the driver plus seat, e.g. 70 kg, and
the unsuspended mass e.g. 15 kg. In two suspension system the corresponding
numbers might be 80 kg and 5 kg (at best). The difference in unsuspended
mass might be 3-fold, but the difference in suspended mass only 15 %.

Where and how does this make an observable difference? (feelings and beliefs
excluded for a moment :) )

If I in an unsuspended upright bike need to provide the bike with a
temporary 'suspension' when meeting an obstacle, I stand on the pedals
instead of sitting on the saddle. Then everything goes as smoothly as I can
imagine. If I have seat suspension in an recumbent, is that a practcally
equivalent system?

I intend to build my 3. recumbent for casual riding. For that project I need
to decide: 2 suspension systems or only one?

When asking this now I notice that it might be possible to observe some of
the essential differences by taking a 2-suspension bike and add different
weights around the front wheel and back wheel for the test rides... Sorry, I
might have bothered this newsgroup in vain :).

But seriously, has anyone of the readers tested these differences?
Observations?

Alan Weiss
August 9th 03, 12:56 PM
I have found that my unsuspended Gold Rush gives a smoother ride than my
3-wheel independent suspended Leitra. I believe that the difference is
mainly due to the Gold Rush's longer wheelbase, but the Gold Rush has a
much plusher seat, so that may be part of it, too. So your question
should take into account the bike design you are considering. Oh, one
other data point, my E2 has a lot of travel in the suspension of its
rear wheel, and the rear rider gets a silky smooth ride. The front wheel
is unsuspended, and the front rider gets jolted over bumps. I would use
a Pantour suspension hub on the front wheel, but I don't think there is
enough clearance between the fork and tire.

Alan Weiss
NJ Gold Rush, E2 tandem, and Leitra rider

Dean Arthur
August 10th 03, 01:24 AM
"Mother's Cut-Rate Recumbent" has front of seat on pivots and rear
attached to spring-loaded plunger from top of seat to frame.
You-build-It article at:

http://www.motherearthnews.com/menarch/archive/goto.asp?article=081/081-162-01&ID=2613&Num=4

David Luecke
August 11th 03, 05:37 AM
I can offer this bit of personal observation. On some of the rough stuff I
ride over, the rear suspension on my Vivo is working hard. Even on rougher
pavement or sidewalks it is pretty active. I have a fender now, so I can
reach back and rest my hand on top of that while riding, and it goes up and
down constantly. Or, I can reach down and feel the suspension pivot point,
and feel the rear triangle (I don't know what this is actually called - the
rear fork) change angle with respect to the bike frame. It moves rapidly
and constantly. This action helps soak up bumps for my comfort, but it also
helps keep the wheel in contact with the road, for traction.

If I had suspension on my seat instead, I may actually soak up jarring
better and give me more comfort; I don't know. But there is no way the
entire bike frame could pivot with respect to my body to keep the wheel in
contact with the road nearly as rapidly or effectively as the rear
suspension does.

I think for just street use, a seat suspension may very well make more
sense, since it allows for more elegant frame geometries, lighter weight,
and greater simplicity. For use on more varied terrain, suspesion near the
wheels is the way to go.


--
David Luecke
Ridin' a RANS Vivo (wahoo!)
Merritt Island, Florida USA

S. Delaire \Rotatorrecumbent\
August 15th 03, 01:01 AM
On the Rotator seat we use elastic cord to tie the fabric to the seat frame, on
the bottom section only. This works like a simple suspension and gives about 3"
movement. Not enough for curb jumping. Super on the cobblestones.
As a side benefit the fabric contours to the human shape, spreading the load
over a wider area which helps fight the dreaded "recumbent butt"
My 2 cents
Speedy
www.rotatorrecumbent.com



optimistx wrote:

> Is seat suspension enough?
>
> It is relatively complicated to have suspension in a bike so that front and
> back are suspended with independent systems.
>
> Is it really useful and necessary to do so in recumbents? Is it enough for
> all practical purposes to suspend the seat only?
>
> If in an upright bike you suspend the seat to move softly up and down, you
> assumably get movement in accordance of pedaling, 'pogo'. The direction of
> forces in legs is down. If the total force to the pedals in vertical
> direction diminishes, the seat goes down. When it increases, it goes up. The
> weight distribution of the driver varies between the pedals and the seat,
> causing irritating movement up and down.
>
> But in a recumbent there should be no 'pogo' in the vertical direction! ?
>
> If the seat is prevented to move in a horizontal direction (forward and
> backward, and side to side) but is free to move up and down within limits,
> suspended, there seems to be a possibility to have one suspension system
> instead of two and get almost as good results as with two.
>
> Almost?
>
> The suspended mass in this system is the driver plus seat, e.g. 70 kg, and
> the unsuspended mass e.g. 15 kg. In two suspension system the corresponding
> numbers might be 80 kg and 5 kg (at best). The difference in unsuspended
> mass might be 3-fold, but the difference in suspended mass only 15 %.
>
> Where and how does this make an observable difference? (feelings and beliefs
> excluded for a moment :) )
>
> If I in an unsuspended upright bike need to provide the bike with a
> temporary 'suspension' when meeting an obstacle, I stand on the pedals
> instead of sitting on the saddle. Then everything goes as smoothly as I can
> imagine. If I have seat suspension in an recumbent, is that a practcally
> equivalent system?
>
> I intend to build my 3. recumbent for casual riding. For that project I need
> to decide: 2 suspension systems or only one?
>
> When asking this now I notice that it might be possible to observe some of
> the essential differences by taking a 2-suspension bike and add different
> weights around the front wheel and back wheel for the test rides... Sorry, I
> might have bothered this newsgroup in vain :).
>
> But seriously, has anyone of the readers tested these differences?
> Observations?



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Tiger Cub
August 19th 03, 01:03 AM
"S. Delaire \"Rotatorrecumbent\"" > wrote in message >...
> On the Rotator seat we use elastic cord to tie the fabric to the seat frame, on
> the bottom section only. This works like a simple suspension and gives about 3"
> movement. Not enough for curb jumping. Super on the cobblestones.
> As a side benefit the fabric contours to the human shape, spreading the load
> over a wider area which helps fight the dreaded "recumbent butt"
> My 2 cents
> Speedy
> www.rotatorrecumbent.com
>

Speaking from 3 happy years with a Rotator Tiger, I can make a few
points based on "seat of the pants" type knowledge of the Rotator
suspended mesh-seat-fabric form of recumbent seat. I am quite happy
with both the seat and the bike.

-The elastic-suspended-bottom Rotator seat is a genuinely cushy ride.
This is due to seat seaign, long monotube frame design, and and the
Rotator's rider position centre of gravity. and Steve Delaire seems to
have found a pretty good recipe for providing great comfort but
without a speed penalty or complexity issues.

-It is a very effective simple, uncomplex, low technology solution to
the support of the human body, and the protection of that body from
small and large irregularities one travels along, through, and over.
This is a good thing. Burt Rutan is similar in some small way to this
in not over-engineering the solutions to the assorted design
challenges inherent in a lightweight structure like a bicycle or
airplane.

-The seat can be very low

-The seat can be very light

-The elastic cord will fray or cut in a fall (more like a
baseball-style slide actually), and replacement elastic cord, if you
bought cheap elastic, will fray and break from the stretching in the
normal course of suspending the body.

-The seat can be adjusted in a very wide range of positions. The ride
can be quite low and stretched out. I am always amazed at how flat and
low the rider looks on this bike when ever I see someone else riding
it. I possibly have my seat more reclined than typical, but it works
for me, perhaps cuz I am quite tall, on the other hand maybe shorter
test riders have to stretch out more to reach the pedals and this is
what I see.

-Assorted pockets for things can be sewn to the seat mesh. You can sew
sleeves and pockets for things such as camelbak sleeves, thermarest
pads, tool pouch, personal massagers, etc. Next winter I am doing a
pocket for the camel bak.

-I have not often had a sore butt riding this bike. It was very
comfortable the very first time I rode it.

-It is quite conformal to the shape of the rider. It fits you, it is
not one of those "you must fit it" rigid seats.

-The mesh is quite comfortable and keeps you fresh in warm conditions.
However when you go through a puddle, you get a back shower through
the seat. SO far this is the only negative thing I have found about
this seat or the entire bike for that matter -- and it is the only
time I swear "kaw-liss" at this bike, and I like to swear a lot.

-I think the seat may contribute to the slightly (and highly
debatable) homebuilt look the bike has. I only mention this cuz so
many people ask me if I built it myself. In fact that is a pretty
common ice-breaker people use to initiate a chat with me. (I think one
woman asked me "patantez vous ca toi meme?" -- as you can see my
french is awful-spelling, grammar, and pronounciation!) Often, this is
a cue to accellerate, especially when the ask how many gears the bike
has, so I just show them!

-The metal tubing that the seat is laced to, can be used to hook a
large seat bag on to. I took a normal "on top of the rear bike rack"
bag and had a little loop sewn on each end and hooked it on the seat.
it looks like it was made for the bike.

The seat can be fixed or repaired at any place that does sewing
repairs, like a shoemaker, a place that does luggage or backpack
repairs, or even a seamstress. I keep a metre ort so of spare cord in
the tool kit, and I know I will always get home if bad stuff happens
to the existing cord or elastic. (especially useful when far from home
-- the cord can even be used for towing the less fortunate
<-extremely not recommended!)


With the seat's simple, open construction, it is easy to attach a home
built tailbox. First, build a coroplast tailbox using some free
coroplast and a few ziplocks. With "democratic" elections, there's an
irregular but free supply of fresh coroplast once the vote is over and
the campaign signs become instant and pure landfill. Re-use!
Experiment! Go nutz and create a corpolast art-bike if speed isn't
your thing. Of course, this might add a bit too much attention for you
quieter types since the bike already attracts a considerable amount of
bystander attention. I might correct myself and state that it will
take a big bunch of ziplocks, not just a few. I prototype/temporarily
rig with the plastic covered wire that is available in a roll at the
hardware store (what am I talking about> it is the stuff like what is
used to close plastic bread bags, electronic component bags, etc.

And now, a digression involving one man's long-time fantasy accessory
for his rotator seat. I would like to get little speakers (small,
cheap, black golf ball sized) that attach on the bottom end of the
seat rail (on the outside of my thighs) so I can plug in my walkman
and hear the radio or motivational music. It doesn't have to be loud
(and no I don't ride with earplugs, or music at all now). I want the
sound to be very directional so when they are pointed upwards towards
my head and ears, no one off the side will hear it, all the sound will
go upwards only, not outwards around me (so it won't disturb other
riders). I'd like this designed for christmas please.

Digressing further, much, much further, I would also consider,
miracle-fabric-enclosed flat panel speakers that slide inside my bike
shorts on the top of my thighs would be also fine and dandy. (Hello
mit media lab, anyone looking for a thesis project?)

All in all, the seat is one of the best of the many good things about
the Rotator bikes. (besides the seat, this includes mid-drive, low
position, monotube design, oss, and for the tiger, a somewhat
manageable size and length of the bike).

People ask me, "is it (the bike or the seat) comfortable?" and I
reply, it is not only comfortable, it is fast. Not one or the other.
Both. And that's all I really want from a bicycle, even all I want out
of life!

tiger

Tiger Cub
August 19th 03, 01:03 AM
"S. Delaire \"Rotatorrecumbent\"" > wrote in message >...
> On the Rotator seat we use elastic cord to tie the fabric to the seat frame, on
> the bottom section only. This works like a simple suspension and gives about 3"
> movement. Not enough for curb jumping. Super on the cobblestones.
> As a side benefit the fabric contours to the human shape, spreading the load
> over a wider area which helps fight the dreaded "recumbent butt"
> My 2 cents
> Speedy
> www.rotatorrecumbent.com
>

Speaking from 3 happy years with a Rotator Tiger, I can make a few
points based on "seat of the pants" type knowledge of the Rotator
suspended mesh-seat-fabric form of recumbent seat. I am quite happy
with both the seat and the bike.

-The elastic-suspended-bottom Rotator seat is a genuinely cushy ride.
This is due to seat seaign, long monotube frame design, and and the
Rotator's rider position centre of gravity. and Steve Delaire seems to
have found a pretty good recipe for providing great comfort but
without a speed penalty or complexity issues.

-It is a very effective simple, uncomplex, low technology solution to
the support of the human body, and the protection of that body from
small and large irregularities one travels along, through, and over.
This is a good thing. Burt Rutan is similar in some small way to this
in not over-engineering the solutions to the assorted design
challenges inherent in a lightweight structure like a bicycle or
airplane.

-The seat can be very low

-The seat can be very light

-The elastic cord will fray or cut in a fall (more like a
baseball-style slide actually), and replacement elastic cord, if you
bought cheap elastic, will fray and break from the stretching in the
normal course of suspending the body.

-The seat can be adjusted in a very wide range of positions. The ride
can be quite low and stretched out. I am always amazed at how flat and
low the rider looks on this bike when ever I see someone else riding
it. I possibly have my seat more reclined than typical, but it works
for me, perhaps cuz I am quite tall, on the other hand maybe shorter
test riders have to stretch out more to reach the pedals and this is
what I see.

-Assorted pockets for things can be sewn to the seat mesh. You can sew
sleeves and pockets for things such as camelbak sleeves, thermarest
pads, tool pouch, personal massagers, etc. Next winter I am doing a
pocket for the camel bak.

-I have not often had a sore butt riding this bike. It was very
comfortable the very first time I rode it.

-It is quite conformal to the shape of the rider. It fits you, it is
not one of those "you must fit it" rigid seats.

-The mesh is quite comfortable and keeps you fresh in warm conditions.
However when you go through a puddle, you get a back shower through
the seat. SO far this is the only negative thing I have found about
this seat or the entire bike for that matter -- and it is the only
time I swear "kaw-liss" at this bike, and I like to swear a lot.

-I think the seat may contribute to the slightly (and highly
debatable) homebuilt look the bike has. I only mention this cuz so
many people ask me if I built it myself. In fact that is a pretty
common ice-breaker people use to initiate a chat with me. (I think one
woman asked me "patantez vous ca toi meme?" -- as you can see my
french is awful-spelling, grammar, and pronounciation!) Often, this is
a cue to accellerate, especially when the ask how many gears the bike
has, so I just show them!

-The metal tubing that the seat is laced to, can be used to hook a
large seat bag on to. I took a normal "on top of the rear bike rack"
bag and had a little loop sewn on each end and hooked it on the seat.
it looks like it was made for the bike.

The seat can be fixed or repaired at any place that does sewing
repairs, like a shoemaker, a place that does luggage or backpack
repairs, or even a seamstress. I keep a metre ort so of spare cord in
the tool kit, and I know I will always get home if bad stuff happens
to the existing cord or elastic. (especially useful when far from home
-- the cord can even be used for towing the less fortunate
<-extremely not recommended!)


With the seat's simple, open construction, it is easy to attach a home
built tailbox. First, build a coroplast tailbox using some free
coroplast and a few ziplocks. With "democratic" elections, there's an
irregular but free supply of fresh coroplast once the vote is over and
the campaign signs become instant and pure landfill. Re-use!
Experiment! Go nutz and create a corpolast art-bike if speed isn't
your thing. Of course, this might add a bit too much attention for you
quieter types since the bike already attracts a considerable amount of
bystander attention. I might correct myself and state that it will
take a big bunch of ziplocks, not just a few. I prototype/temporarily
rig with the plastic covered wire that is available in a roll at the
hardware store (what am I talking about> it is the stuff like what is
used to close plastic bread bags, electronic component bags, etc.

And now, a digression involving one man's long-time fantasy accessory
for his rotator seat. I would like to get little speakers (small,
cheap, black golf ball sized) that attach on the bottom end of the
seat rail (on the outside of my thighs) so I can plug in my walkman
and hear the radio or motivational music. It doesn't have to be loud
(and no I don't ride with earplugs, or music at all now). I want the
sound to be very directional so when they are pointed upwards towards
my head and ears, no one off the side will hear it, all the sound will
go upwards only, not outwards around me (so it won't disturb other
riders). I'd like this designed for christmas please.

Digressing further, much, much further, I would also consider,
miracle-fabric-enclosed flat panel speakers that slide inside my bike
shorts on the top of my thighs would be also fine and dandy. (Hello
mit media lab, anyone looking for a thesis project?)

All in all, the seat is one of the best of the many good things about
the Rotator bikes. (besides the seat, this includes mid-drive, low
position, monotube design, oss, and for the tiger, a somewhat
manageable size and length of the bike).

People ask me, "is it (the bike or the seat) comfortable?" and I
reply, it is not only comfortable, it is fast. Not one or the other.
Both. And that's all I really want from a bicycle, even all I want out
of life!

tiger

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