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URT sucks?



 
 
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  #11  
Old June 26th 03, 09:23 PM
Spider
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Default URT sucks?

wrote in message . com...
"Dave Stocker" wrote in message ...


snip

What I tried to say in my original post was that URT, like any other
suspension type, has its pros and cons and it has its niche. When people
say URT sucks, they are usually extrapolating the shortfalls of a particular
design to the principle.

-Dave



Thanks for the informative post Dave


You had to quote that whole damn thing to write six words of "me too?"

Sheesh.

Spider
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  #13  
Old June 26th 03, 10:06 PM
Dave Stocker
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Default URT sucks?

"P e t e F a g e r l i n" schrieb im Newsbeitrag
...

|
|So if I am wrong in my assumptions about how this thing works, then I ask
|you: How does it work?

As noted before, when seated it is quite active, contrary to your
claim, and when standing, it is considerably less active, but active
nonbetheless, also contrary to your claim.


Ok, you said this a couple of posts ago:
Actually false. The Ibis Bow Ti is active when you are out of the
saddle. Less active than when you are seated, but active nonetheless.


I misread this as:
Actually false. The Ibis Bow Ti is active when you are out of the
saddle. Less active when you are seated, but active nonetheless.


So I understood a claim that it was more active out of the saddle than in
it. This went against my understanding of how URT works and was scratching
my head coming up with a reason it could be so. So now that that is out of
the way, we can safely say it acts like every other URT: less active out of
the saddle than seated.

I think it is possible to generalize quantitatively how pivot location and
rider wieght affect how the suspension acts, but I want to sleep first.

-Dave



  #14  
Old June 26th 03, 10:08 PM
P e t e F a g e r l i n
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Default URT sucks?

On Thu, 26 Jun 2003 22:56:02 +0200, "Dave Stocker"
wrote:

|"P e t e F a g e r l i n" schrieb im Newsbeitrag
.. .
| Apparently you missed this part:
|
| "Unified Rear Triangle (URT) "
|
| "Placements ranges from very close to the BB (Trek/Gary Fisher) to in
| the middle of the downtube (John Castellianos patented "Sweet Spot" on
| for example Schwinn, Ibis)"
|
| The Bow Ti is a URT.
|
|
|No I did not miss it. Just because Ibis used Castellianos' "Sweet Spot", it
|does NOT automatically follow that the Bow Ti is a URT.

Sigh...you can lead a horse to water, but...


|snip more of the same
|
| |
| |The inherent problem with this design is that the rider is in effect
| |standing on the swingarm. This is less of a problem when the rider is
| |seated, but the natural tendency when going over larger obstacles, rough
| |terrain, or technical sections is to stand up, rendering the rear
|suspension
| |almost useless. The flip side to this effect is that during sprinted or
| |climbing out of the saddle, the suspension's lack of movement is
|considered
| |a bonus, as less energy is wasted in suspension movement.
| |
| |There have been several very popular URT bikes in the past, most notably
|the
| |Klein Mantra, the Trek/Gary Fisher Y-bikes, and the Ibis Sweet Spot.
|There
| |have also been twists on the URT design in the form of the GT iDrive and
|the
| |Paul Turner desiged Maverick."
| |
| |LOL! This is all consistent with what I said.
|
| How can it be consistent with what you said, when you claim that the
| Bow Ti should not be labeled as a URT, and each article shows that the
| Bow Ti is a URT?
|
|
|The seated vs standing part is consistent with what I said.

Again, bull****.

You wrote that the suspension is only active if the rider remains
seated. That is incorrect.

As I said
|earlier, there was no specific mention of the Bow Ti in any of these.

The Bow Ti is a Sweet Spot bike----------------URT.

It's really not that difficult.


But
|this is a moot, bucause I already said in my last post that I now agree that
|the Bow Ti is a URT. So what is the problem?

Hmmm...I would ascribe it to some reading comprehension issues on your
part or an inabilty to understand exactly what "Sweet Spot" means (URT
with the pivot located in the middle, rather than at the extremes).

  #15  
Old June 26th 03, 10:19 PM
Dave Stocker
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Default URT sucks?

"P e t e F a g e r l i n" schrieb im Newsbeitrag
...


The Bow Ti is a Sweet Spot bike----------------URT.

It's really not that difficult.

But
|this is a moot, bucause I already said in my last post that I now agree

that
|the Bow Ti is a URT. So what is the problem?

Hmmm...I would ascribe it to some reading comprehension issues on your
part or an inabilty to understand exactly what "Sweet Spot" means (URT
with the pivot located in the middle, rather than at the extremes).


I started this thread hoping to talk a bit about the physics of these
things. Oh well, it was not to be...

-Dave


  #16  
Old June 27th 03, 06:31 AM
Dave Stocker
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Default URT sucks?

So here goes:

Let:
L= the distance from the pivot to the rear dropout
l= the distance from the pivot to the BB
TL = "Theta L", the angle between a plumbline dropped at the pivot and L
Tl = "Theta l", the angle between a plumbline dropped at the pivot and l
R = Rider wieght
F = the force up on the rear wheel due to terrain

Now FL acts as a lever on Rl. You could model the rider by suspending an
equavalent wieght to the rider from the point where the L line is directly
above the BB. I will call this point l'.
l' = l*Sin(Tl)

If the line between the pivot and L were level (TL=90deg), at equilibrium we
would have:
FL = R*l'

Any greater F and we get travel.

We account for TL!=90deg by:
FL = (R*l')*Sin(TL)
so
F = ((R*l')*Sin(TL))/L

on a low pivot bike such as mine l~l' and Sin(TL)~1, so I have:
F = R*l/L or F=R/10 in my case; about 18lb

On a high pivot bike, you have to keep all of those ugly thetas:
F = (R*l*Sin(Tl)*Sin(TL))/L

I fiddled with some arbitrary pivot placements and came up F figures as much
as 3 or 4x as my bike, but still much lower than I has expected. This is
not the same a preload and it does have a dampening effect on the upstroke.

-Dave


  #17  
Old June 27th 03, 06:50 AM
Sorni
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Posts: n/a
Default URT sucks?

"Dave Stocker" wrote in message
...
So here goes:

Let:
L= the distance from the pivot to the rear dropout
l= the distance from the pivot to the BB
TL = "Theta L", the angle between a plumbline dropped at the pivot and L
Tl = "Theta l", the angle between a plumbline dropped at the pivot and l
R = Rider wieght
F = the force up on the rear wheel due to terrain

Now FL acts as a lever on Rl. You could model the rider by suspending an
equavalent wieght to the rider from the point where the L line is directly
above the BB. I will call this point l'.
l' = l*Sin(Tl)

If the line between the pivot and L were level (TL=90deg), at equilibrium

we
would have:
FL = R*l'

Any greater F and we get travel.

We account for TL!=90deg by:
FL = (R*l')*Sin(TL)
so
F = ((R*l')*Sin(TL))/L

on a low pivot bike such as mine l~l' and Sin(TL)~1, so I have:
F = R*l/L or F=R/10 in my case; about 18lb

On a high pivot bike, you have to keep all of those ugly thetas:
F = (R*l*Sin(Tl)*Sin(TL))/L

I fiddled with some arbitrary pivot placements and came up F figures as

much
as 3 or 4x as my bike, but still much lower than I has expected. This is
not the same a preload and it does have a dampening effect on the

upstroke.

Or just push down on the saddle and furrow your brow a bit.

Bill "sorted" S.


  #18  
Old June 27th 03, 07:12 AM
Dave W
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Posts: n/a
Default URT sucks?

On Thu, 26 Jun 2003 22:56:02 +0200, "Dave Stocker"
wrote:

"P e t e F a g e r l i n" schrieb im Newsbeitrag
.. .
Apparently you missed this part:

"Unified Rear Triangle (URT) "

"Placements ranges from very close to the BB (Trek/Gary Fisher) to in
the middle of the downtube (John Castellianos patented "Sweet Spot" on
for example Schwinn, Ibis)"

The Bow Ti is a URT.


No I did not miss it. Just because Ibis used Castellianos' "Sweet Spot", it
does NOT automatically follow that the Bow Ti is a URT.

snip more of the same

|
|The inherent problem with this design is that the rider is in effect
|standing on the swingarm. This is less of a problem when the rider is
|seated, but the natural tendency when going over larger obstacles, rough
|terrain, or technical sections is to stand up, rendering the rear

suspension
|almost useless. The flip side to this effect is that during sprinted or
|climbing out of the saddle, the suspension's lack of movement is

considered
|a bonus, as less energy is wasted in suspension movement.
|
|There have been several very popular URT bikes in the past, most notably

the
|Klein Mantra, the Trek/Gary Fisher Y-bikes, and the Ibis Sweet Spot.

There
|have also been twists on the URT design in the form of the GT iDrive and

the
|Paul Turner desiged Maverick."
|
|LOL! This is all consistent with what I said.

How can it be consistent with what you said, when you claim that the
Bow Ti should not be labeled as a URT, and each article shows that the
Bow Ti is a URT?


The seated vs standing part is consistent with what I said. As I said
earlier, there was no specific mention of the Bow Ti in any of these. But
this is a moot, bucause I already said in my last post that I now agree that
the Bow Ti is a URT. So what is the problem?

-Dave


Haven't you figured that out yet? It's Pete "never wrong" Fagerlin. As
soon as you realize this you'll save yourself a whole lot of crap,
like you just went through.
  #19  
Old June 27th 03, 07:13 AM
Dave W
external usenet poster
 
Posts: n/a
Default URT sucks?

On Thu, 26 Jun 2003 23:19:10 +0200, "Dave Stocker"
wrote:

"P e t e F a g e r l i n" schrieb im Newsbeitrag
.. .


The Bow Ti is a Sweet Spot bike----------------URT.

It's really not that difficult.

But
|this is a moot, bucause I already said in my last post that I now agree

that
|the Bow Ti is a URT. So what is the problem?

Hmmm...I would ascribe it to some reading comprehension issues on your
part or an inabilty to understand exactly what "Sweet Spot" means (URT
with the pivot located in the middle, rather than at the extremes).


I started this thread hoping to talk a bit about the physics of these
things. Oh well, it was not to be...

-Dave


not with that guy it ain't.


  #20  
Old June 27th 03, 05:16 PM
Spider
external usenet poster
 
Posts: n/a
Default URT sucks?

Dave W wrote in message . ..
On Thu, 26 Jun 2003 22:56:02 +0200, "Dave Stocker"
wrote:

"P e t e F a g e r l i n" schrieb im Newsbeitrag
.. .
Apparently you missed this part:

"Unified Rear Triangle (URT) "

"Placements ranges from very close to the BB (Trek/Gary Fisher) to in
the middle of the downtube (John Castellianos patented "Sweet Spot" on
for example Schwinn, Ibis)"

The Bow Ti is a URT.


No I did not miss it. Just because Ibis used Castellianos' "Sweet Spot", it
does NOT automatically follow that the Bow Ti is a URT.

snip more of the same

|
|The inherent problem with this design is that the rider is in effect
|standing on the swingarm. This is less of a problem when the rider is
|seated, but the natural tendency when going over larger obstacles, rough
|terrain, or technical sections is to stand up, rendering the rear

suspension
|almost useless. The flip side to this effect is that during sprinted or
|climbing out of the saddle, the suspension's lack of movement is

considered
|a bonus, as less energy is wasted in suspension movement.
|
|There have been several very popular URT bikes in the past, most notably

the
|Klein Mantra, the Trek/Gary Fisher Y-bikes, and the Ibis Sweet Spot.

There
|have also been twists on the URT design in the form of the GT iDrive and

the
|Paul Turner desiged Maverick."
|
|LOL! This is all consistent with what I said.

How can it be consistent with what you said, when you claim that the
Bow Ti should not be labeled as a URT, and each article shows that the
Bow Ti is a URT?


The seated vs standing part is consistent with what I said. As I said
earlier, there was no specific mention of the Bow Ti in any of these. But
this is a moot, bucause I already said in my last post that I now agree that
the Bow Ti is a URT. So what is the problem?

-Dave


Haven't you figured that out yet? It's Pete "never wrong" Fagerlin. As
soon as you realize this you'll save yourself a whole lot of crap,
like you just went through.


While he might not have figured that out, he certainly knows not to
take advice from Dave "always wrong" Wussyass, because banging your
head against the wall is so much more productive.

Spider
 




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