Unicyclist Community

Go Back   Unicyclist Community > Unicycling Discussion > General Unicycling Discussions

Reply
 
Thread Tools Search this Thread Rating: Thread Rating: 2 votes, 5.00 average. Display Modes
Old 2012-08-13, 12:27 AM   #16
Nurse Ben
XC Muni
 
Nurse Ben's Avatar
 
Join Date: Jul 2008
Location: Northern Cascades, USA
Age: 53
Posts: 4,644
At a standstill on flat ground, your body will balance on the unicycle best in a neutral position, which is when the frame is perpendicular to the ground, so adjusting the seat angle relative to the frame will help you achieve your individual neutral position based on where you seat on the seat, how your posture/body type weights the seat, and the terrain your ride.

I have adjustable seat posts on all my unis, and through trial and error I have adjusted my seat angles to positions that are most comfortable, ie minimal taint pressure, comfortable jewels, moderate pressure on my sit bones, and ease of movement on the saddle.

Now if you want to say it doesn't matter, that's all fine and good, and maybe the lot of us are princess and the pea types, but I can tell a big difference when I'm setting up a new seat.

My XC unis tend used to be set up flatter than my DH unis, which makes sence based on terrain choice, but over time that difference has become less and less, so now all of my unis are set up so that the butt pad portion of the seat is perpendicular to the frame.

I think Mike's pics tell the story, good posture and good balance go hand in hand, so adjusting the seat helps the rider individualize the uni for better balance.
__________________
I dream of hamsters and elderberries

Last edited by Nurse Ben; 2012-08-13 at 12:32 AM.
Nurse Ben is offline   Reply With Quote
Old 2012-08-13, 01:30 AM   #17
GizmoDuck
Adventure Unicyclist
 
GizmoDuck's Avatar
 
Join Date: Apr 2002
Location: Wellington, NZ
Age: 40
Posts: 3,653
Quote:
Originally Posted by ImFalling View Post
Yes. But given that seats are all curved, moving the seat forward/backwards means changing the angle between the nose and the pressure point. Its just semantics.
That is something that I try to change in my modifications or custom seats. They should be flat.

Last edited by GizmoDuck; 2012-08-13 at 01:37 AM.
GizmoDuck is offline   Reply With Quote
Old 2012-08-13, 01:35 AM   #18
GizmoDuck
Adventure Unicyclist
 
GizmoDuck's Avatar
 
Join Date: Apr 2002
Location: Wellington, NZ
Age: 40
Posts: 3,653
Quote:
Originally Posted by Nurse Ben View Post
I think Mike's pics tell the story, good posture and good balance go hand in hand, so adjusting the seat helps the rider individualize the uni for better balance.
In my #14 post, I see what Mike and Harper are getting at, but the effect you get from tilting the seat is the same as adjusting the seat forward and backward (horizontally).

If you got rid of the curvature of the seat, and any hardware related to angle adjustment, you save weight and reduce redundant seat height (important for short people).

Having forward/backward seat adjustment is less complex than angle adjustment.

Last edited by GizmoDuck; 2012-08-13 at 01:38 AM.
GizmoDuck is offline   Reply With Quote
Old 2012-08-13, 11:21 AM   #19
jbtilley
Muni Foot
 
jbtilley's Avatar
 
Join Date: Jul 2011
Location: North Carolina
Posts: 761
Interesting read. I look forward to the Various Crank Arm Lengths - why are they needed??? thread.
jbtilley is offline   Reply With Quote
Old 2012-08-13, 11:59 AM   #20
Nurse Ben
XC Muni
 
Nurse Ben's Avatar
 
Join Date: Jul 2008
Location: Northern Cascades, USA
Age: 53
Posts: 4,644
Quote:
Having forward/backward seat adjustment is less complex than angle adjustment.
Yes, that would be a nice option, just like a bike. You have some fore/aft positioning on the fixed posts, but still not enough.

Quote:
If you got rid of the curvature of the seat, and any hardware related to angle adjustment, you save weight and reduce redundant seat height (important for short people).
I have a stack of minicell foam cut ups where I mocked some seat designs, but after a bunch of tries I could not get close to the comfort of the KH Freeride. I think the movement of the pelvis on a unicycle seat is significantly different than on a bicycle seat, so flat might not be all that great.

I'd like to have a seat with a narrower waist.
__________________
I dream of hamsters and elderberries
Nurse Ben is offline   Reply With Quote
Old 2012-08-13, 04:39 PM   #21
Klaas Bil
Sir Prince of Newsgroupia
 
Join Date: Jan 2003
Location: Ede, Netherlands
Age: 65
Posts: 5,235
I agree with ImFalling. Given that a typical uni seat is curved, what you do when tilting the seat up and down is moving your sitting location back and forth. And since - again - a typical uni seat is narrower in the middle, a bit wider in the front and a bit more wider in the back, you can find a spot where you sit most comfortably. I found for myself that I sit most comfortably on a location a bit back from the middle (more 'flesh' to support my weight), while my thighs move around the narrowest part of the seat, where there is minimum rubbing and chafing. On a standard non-adjustable seat the narrowest part is approximately the lowest, and hence where you sit. That means that I tilt my seats a little bit nose-up compared to non-adjustable seats, but not nearly as much as some other riders.

One can argue that Ken's original questions could really be asked for a 'hypothetical' seat (curved or not) that has the same width everywhere. For real-life uni seats, I think there sure is an effect of tilting (beyond just tilting the frame in compensation).
Klaas Bil is offline   Reply With Quote
Old 2012-08-13, 05:31 PM   #22
GizmoDuck
Adventure Unicyclist
 
GizmoDuck's Avatar
 
Join Date: Apr 2002
Location: Wellington, NZ
Age: 40
Posts: 3,653
Quote:
Originally Posted by Klaas Bil View Post
I agree with ImFalling. Given that a typical uni seat is curved, what you do when tilting the seat up and down is moving your sitting location back and forth. And since - again - a typical uni seat is narrower in the middle, a bit wider in the front and a bit more wider in the back, you can find a spot where you sit most comfortably. I found for myself that I sit most comfortably on a location a bit back from the middle (more 'flesh' to support my weight), while my thighs move around the narrowest part of the seat, where there is minimum rubbing and chafing. On a standard non-adjustable seat the narrowest part is approximately the lowest, and hence where you sit. That means that I tilt my seats a little bit nose-up compared to non-adjustable seats, but not nearly as much as some other riders.

One can argue that Ken's original questions could really be asked for a 'hypothetical' seat (curved or not) that has the same width everywhere. For real-life uni seats, I think there sure is an effect of tilting (beyond just tilting the frame in compensation).
Yes, that is the other issue. Seat angle adjustment doesn't necessarily translate to seat angle adjustment; it translates to which part of the saddle you end up sitting on, because of saddle curvature.

The whole point of a seat that widens out at the back is because that is where the weight should be supported (ie the 'sit bones' or ischial tuberosities of the pelvis).

How many people actually plant their weight on the widest part of the saddle? What is intended to happen isn't what happens in reality.
GizmoDuck is offline   Reply With Quote
Old 2012-08-14, 09:03 PM   #23
knoxuni
wes style!!
 
knoxuni's Avatar
 
Join Date: Jun 2010
Location: central ohio
Age: 23
Posts: 5,978
Send a message via Skype™ to knoxuni
I have mine set up now were my weight or butt bones are on the widest part of the seat.
__________________
Roses are red, violets are blue, may I procreate with you so I can ride a g32!! - Alan hogan
knoxuni is offline   Reply With Quote
Old 2012-08-16, 04:56 PM   #24
Zzagg
Marchons, marchons, caricature abre
 
Zzagg's Avatar
 
Join Date: Jun 2004
Location: France, NANTES (Bretagne)
Age: 44
Posts: 3,884
Quote:
Originally Posted by tholub View Post
Did you do anything to test this hypothesis, like tilting your seat all the way up and all the way down to see if it feels any different?

It does.
This statement is true and therefor should have made a point.
When asking about the effects of a change in whatever setting, it's always usefull to try and imagine the extremes of the range of this setting.
I couldn't ride a unicycle while seating on a full up tilted seat, same goes for a full down tilted seat.
__________________
GILD: "You get to play every game in the world, in the finest game setting known to man, your imagination."

One of these days I'm gonna change my evil ways.
Till then I'll just keep riding on
Zzagg is offline   Reply With Quote
Old 2018-05-25, 03:42 AM   #25
Scoox
Wheel enthusiast
 
Scoox's Avatar
 
Join Date: Apr 2018
Age: 37
Posts: 124
Sorry to resurrect this old thread, but since seats are... well, just seats, I suppose the topic is timeless.

I was just thinking about this too. I arrived at a similar theory.

Firstly, if 1) the saddle was a constant width throughout, and 2) its curvature was a perfect arc, then all tilt settings would feel identical to the rider, and therefore there would be no need to adjust tilt as long as the seat was sufficiently long front and back. Some riders may want their seat longer at the back and some longer at the front, so manufacturers would have to make seats that are long both ways to satisfy everyone's needs. This would make the seat heavier, so seat that can be moved back and forth pleases everyone whilst keeping weight down (as well as materials and therefore cost).

For argument's sake we'll assume saddles are arc-shaped, now let's add in two constraints:

1. The equilibrium position requires that the rider's centre of mass (from the sit bone up) lies vertically above the wheel axle.

2. Saddle width is not constant, and riders will subconsciously position themselves so as to maximise comfort, which usually means sit bones on the widest spot of the saddle. Call that the sitting spot. Furthermore, the sitting plane must be horizontal (i.e. parallel to the ground) so that the rider doesn't slip forwards or backwards on the saddle.

The first constraint is a fact, and the second one a requirement. Now can this requirement be satisfied for any given angle of the frame with respect to the vertical? Short answer is no:

Name:  Saddle angle (800x800).png
Views: 116
Size:  61.3 KB

Figure 1: Saddle in neutral (horizontal position), the red arrow is perpendicular to the saddle at the sitting spot.

Figure 2: In order to achieve equilibrium, rider tilts frame forward. Now the sitting spot is directly above the wheel axle (green dotted arrow) but the sitting spot plane is not parallel to the ground plane; instead it's aggressively tilted forwards like a slide—bad.

Figure 3: Seat angle is adjusted until sitting spot coincides with the top of seat tube, and the red and green dotted arrows are co-linear, thus ensuring all constraints and requirements are satisfied (equilibrium and comfort).

Another side effect of seat angle adjustments is that the position of the handle (and brake lever if one is present) are affected as denoted by the fat red dot.

Even if the seat was a perfect arc of constant width, from a mechanical perspective the optimal configuration is one where the rider's weight lies directly above the top of the seatpost, as this ensures only axial compression forces are exerted on the seatpost. An off-axis load will exert both compression and torque, the latter usually being mechanically more taxing and an important consideration if the seatpost crown (don't know the correct name for this) is welded. In the following diagram representing a frame+saddle, the right configuration would be stronger:

Name:  Saddle angle 2 (800x800).png
Views: 116
Size:  35.6 KB

Riders tend to compensate for inadequate saddle configurations by hunching forward. This achieves the equilibrium and comfort at the sit bones, but negatively affects comfort elsewhere e.g. the lower back. A bit like an ergonomic chair vs a cheap crappy chair: both get the job done but the former does the job better.

Last edited by Scoox; 2018-05-25 at 04:00 AM.
Scoox is offline   Reply With Quote
Old 2018-05-25, 06:17 AM   #26
johnfoss
North Shore ridin'
 
johnfoss's Avatar
 
Join Date: Apr 2002
Location: El Dorado Hills, CA
Age: 56
Posts: 16,869
I probably shouldn't dip my toe into this thread, but....

I learned to ride in 1979 on crappy old Schwinn seats. 40 years later, we are using exactly the same type of seatpost, which has become the de-facto standard thanks to KH and Nimbus, I think. This is not the newer Pivot post, of course, but the smile-shaped post top with the four bolt slots, allowing for maybe 1/2" of adjustment to the front or rear.

Dial the clock back to 1979, with seats that were not great, pockets not full of money to experiment, and a nearly non-existent market that offered mostly worse alternatives for other seats. Bradley Bradley and I figured out in our first few weeks of riding that we preferred sliding the seat all the way forward. This put the front higher, and seemed to provide a little more crotch/butt support for long rides in a time without seat handles, handlebars or advanced foams inside.

I have no idea what you are trying to get at with those diagrams, much less the 2012 part of this discussion. Moving the seat on a Schwinn/KH-style 4-bolt seatpost does exactly what it appears to do when you slide the seat back and forth in those slots; tilts the seat. The frame moves slightly to the front or back, in relation to the frame, but this is irrelevant; the tilt is all you can feel.

For many years after our early Schwinns, we rode Miyata unicycles with no seat angle adjustment. We didn't particularly miss it; instead we shoved extra foam into the seats to give them a little more cushion. At least those seats had handles at the front and rear (before the "actual" handle; you could still get a pretty good grip on those bumpers).

What is my point? I guess it is to ask what's the point of this thread. Have a nice day!
__________________
John Foss
www.unicycling.com

"The miracle is this: the more we share, the more we have." -- Leonard Nimoy

Last edited by johnfoss; 2018-05-25 at 06:21 AM.
johnfoss is offline   Reply With Quote
Old 2018-05-25, 09:20 AM   #27
Mikefule
Bridge of Otherwhere: on Kindle
 
Mikefule's Avatar
 
Join Date: May 2002
Location: Long Bennington, Lincolnshire, England.
Posts: 7,136
Think of the unicyclist as 3 linked beams with 2 (hinges): the torso (the hips) the thighs (the knees) and the lower legs.

The angle between the torso and thighs is important for comfort and efficiency of pedalling. In turn, this angle affects the angle between the thighs and the lower legs.

You can of course change the angle of the seat by tilting the frame backwards. Tilt the frame backwards and the saddle will point upwards.

However, that will move the seat back behind the axle. Therefore, it will move the rider's backside back behind the axle.

The riders backside has mass: more in some cases than in others.

In order to compensate for the mass of the backside being further behind the axle, some other mass has to move forward of the axle. Therefore, if the backside is moved too far backwards, the torso has to lean forwards to compensate.

Thus, the unicycle is balanced as normal, but the rider is in a less comfortable and efficient position. The "hinge" between the torso and thighs is a smaller angle than ideal, the thighs are slightly more horizontal than ideal, and the angle between the thighs and lower legs is also changed.

It is easiest to visualise these effects by considering exaggerated extremes:

1) If the seat were exactly over the axle, the rider would be in a very upright posture. The rider would look like a capital I

2) If the frame were angled back say 45 degrees (for illustration) the torso would need to lean forwards uncomfortably. The rider would look like a question mark: ?

The best approach is first to find a riding position that is comfortable and efficient. That will probably involve the torso being reasonably upright, and the backside only slightly behind the axle. Then, once the best riding position has been found, the angle of the seat can be adjusted so that it supports the backside comfortably in the backside's correct position.

There is some comparison here with bicycles. A racing bicycle will have a steep seat tube angle so that the rider's weight is almost over the bottom bracket. A granny bike/cruiser/shopper will have a shallower angle but the rider cannot pedal so effectively. There are differences too, of course, because a bicyclist has another wheel to help to balance the machine.
__________________
My first novel, Bridge of Otherwhere, Michael Wilkinson, on Kindle. A tale of subtle magic, mystery, friendship and love. Tinyurl.com/Bridge-of-Otherwhere For US$ page: TinyURL.com/OtherwhereBridge
Mikefule is offline   Reply With Quote
Reply

Tags
adjustment, angle, needed, seat


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Why is it you see a clown walking down the road when you're not on your uni? Gadge Just Conversation & Introduce Yourself 7 2012-08-15 12:10 AM
why can't unicyclists have it too? Palacki808 General Unicycling Discussions 34 2012-04-28 04:46 PM
Seat angle adjustment 101 Krashin'Kenny General Unicycling Discussions 4 2004-09-13 10:53 PM
Adjustment tips needed! jokkeri General Unicycling Discussions 22 2002-10-09 10:48 PM


All times are GMT. The time now is 03:13 PM.


Powered by vBulletin®
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Copyright © 2001-2016 Gilby
You Rated this Thread:
Page generated in 0.33283 seconds with 11 queries