Measuring "comfort" in bicycle frames?

"Anders Bro Bystrup" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Currently I'm helping out a Danish cycling magazine with setting up a testing facility to measure
stiffness in bicycle frames - similar to how German Tour Magazin tests (BB and headtube stiffness,
respectively). We would like to measure the frames ability to absorb shock as well.

I talked to a few engineers regarding this and they all told different stories. One said it's all
about frequency: you apply vibration with a certain frequency to the frame and measure the
frequency on the frame.

Same

Quoted message said:

frequency = zero dampening.

Another guy said it's a lot more complicated and that there's no simple

way

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of measuring this. However, measuring deflection (dunno if it's the

correct

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term for this, hope you understand) only is the way to go, if it has to be simple. Trad. steel
frames are generally considered comfortable but steel has the worst dampening caracteristics of
all construction materials, so

the

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comfort must come from deflection of the thin diametre tubes.

Comments, please!

Wbr, Anders B. Bystrup Denmark

- hoping that Jobst Brandt or other experts of this newsgroup will share their knowledge

How about the hammer test; either the tyre is hit by a hammer, or bike is set on a plate which is
hit by hammer, and then the amplitudes, accelerations and frequencies are measured on the bike
saddle, pedals and handlebars?

Obviously tyres, saddle paddings and handelebar tapes are dumpening most of the vibrations, but as
bikes are normally ridden with those, they should be included in the measurements.

Antti

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

Quoted message said:

How about the hammer test; either the tyre is hit by a hammer, or bike is set on a plate which is
hit by hammer, and then the amplitudes, accelerations and frequencies are measured on the bike
saddle, pedals and handlebars?

Obviously tyres, saddle paddings and handelebar tapes are dumpening most

of

Quoted message said:

the vibrations, but as bikes are normally ridden with those, they should

be

Quoted message said:

included in the measurements.

We are interested in measuring frames only. Frames and bikes will be ridden as a part of the tests
but we want to add measureable facts to the subjective riding impression.

Wbr, Anders

"Anders Bro Bystrup" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

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

Quoted message said:

How about the hammer test; either the tyre is hit by a hammer, or bike

is

Quoted message said:

Quoted message said:

set on a plate which is hit by hammer, and then the amplitudes, accelerations and frequencies
are measured on the bike saddle, pedals

and

Quoted message said:

Quoted message said:

handlebars?

Obviously tyres, saddle paddings and handelebar tapes are dumpening most

of

Quoted message said:

the vibrations, but as bikes are normally ridden with those, they should

be

Quoted message said:

included in the measurements.

We are interested in measuring frames only. Frames and bikes will be

ridden

Quoted message said:

as a part of the tests but we want to add measureable facts to the subjective riding impression.

Wbr, Anders

Well, then just make the measurements without bike components, but I wouldn't then recommend to make
predictions or judgements about the frame "comfort" without the related stuff. Or, might be worth to
make measurements with frames only, and normally equipped bikes?

Antti

Anders Bro Bystrup said:

We would like to measure the frames ability to absorb shock as well.

That concept is a creature of the marketing department, not engineering.

Quoted message said:

I talked to a few engineers regarding this and they all told different stories. One said it's all
about frequency: you apply vibration with a certain frequency to the frame and measure the
frequency on the frame. Same frequency = zero dampening.

That's amusing. Wrong, but amusing. In a classical spring-mass-damper system, the motion of the
system (frequency of the frame) if _undamped_ will be a superposition of the natural frequency of
the system itself and the input frequency. If the input frequency matches the natural frequency
of the spring, you get resonance, a steady build-up of amplitude. If the frequencies are close
(input and natural) you get "beats", fluctuations of amplitude, like hitting two neighboring keys
of a piano.

If the system _is_ damped, then the frequency of the response will settle down to that of the input,
with an amplitude and phase shift.

This is very basic differential equations stuff.

Now, a bike frame isn't quite a simple spring-mass system, but to first order it is. The best way to
find the natural frequencies of the system is to look for resonance response by varying the input
frequency; you still get some resonance even with a damped system. No real structure is totally
undamped, just like no circuit is resistance-free.

--

David L. Johnson

__o | Accept risk. Accept responsibility. Put a lawyer out of _`\(,_ | business. (_)/ (_) |

David L. Johnson said:

Anders Bro Bystrup said:

We would like to measure the frames ability to absorb shock as well.

That concept is a creature of the marketing department, not engineering.

Quoted message said:

I talked to a few engineers regarding this and they all told different stories. One said it's
all about frequency: you apply vibration with a certain frequency to the frame and measure the
frequency on the frame. Same frequency = zero dampening.

That's amusing. Wrong, but amusing....

...

Quoted message said:

This is very basic differential equations stuff.

Confirmed, if need be. Setting aside the beauty of non-homogeneous differential equations I believe
one should take a much more prosaic attitude. I have long had an idea of how to assess comfort, and
in a way to 'measure' it. Here is how.

Take two different frames, build them into bicycles with exactly the same components, from tyres to
seat. Let the same guy ride them asking him to carry out a 'blind test'. The two bikes should have
tyres inflated to a somewhat different pressure, one bike from the other, in a way that, say, the
conventional steel frameset would feel just as mushy as the carbon fiber one.

There you have it. The two frames have become equally shock absorbing thanks to the different air
pressure in the tubes. Hence, the difference in the rolling resistence, which is a known function of
the pressure, is a measure of the ability to absorb shocks.

Isn't that all that one might want to measure, after all?

Sergio Pisa

Anders Bro Bystrup said:

We are interested in measuring frames only. Frames and bikes will be ridden as a part of the tests
but we want to add measurable facts to the subjective riding impression.

I think you should do a "library search" to avoid repeating what has already been done. Besides
that, I would be interested in the goals of the research. Why and for what reason is frame stiffness
being researched? What effects of frame stiffness on riding are defined?

As mentioned in other threads on this subject, ride comfort does not come from frame flexibility but
rather its wheelbase, saddle position between front and rear wheels and handlebar position. The fork
of a bicycle is angled to receive significant (occurrence times amplitude) axially. Therefore the
fork can be ruled out as well as the rear triangle. That leaves only the flex in top and downtube.
That is easily measured by applying a static load.

Lateral stiffness, the one most often discussed, is simple to quantify by anchoring the frame by its
dropouts on horizontally rotatable swivels and putting a side load on the BB. To make a doctoral
thesis of this is ridiculous. The University of Aachen together with Tour Magazine make more of this
than there is in my estimation.

It almost rings of the old saw that steel frames get soft with use.

Jobst Brandt [email hidden]

"Mike S." <mikeshaw2@coxDOTnet> wrote in message news:E4dlb.71850$vj2.9970@fed1read06...
|
...snip
|
| The best way I can think of it to get frames made of different materials
in
| the same size and angles. That way, the only thing that changes is the material, not the rider's
| positioning on the bike itself.
|
| The best way to do the test is to have the same set of components put on
all
| the bikes. Run 32 hole Open Pros, with brand X tires inflated to the
same
| PSI, the same saddle, etc. That way, you isolate the way the frame
reacts
| vs. the components.
|
...snip
|
| Mike
|
|

I vaguely remember some magazine's shoot-out between frame materials. I think the biking mag
did exactly what you are suggesting (ie, built bikes with similar geometry and size out of
different metals). Darned if I can recall the results though. Maybe someone else here can
remember the details.

Jean

Phil Brown said:

Quoted message said:

We are interested in measuring frames only. Frames and bikes will be ridden as a part of the
tests but we want to add measureable facts to the subjective riding impression.

Quoted message said:

This seems like a troll but your tests will be meaningless. You don't ride frames, you ride
bicycles and as a result your tests will have no meaning.

Quoted message said:

Besides, how do you quantify "Comfort?"

In units of comfort, of course! The SI (Systeme Internationale) unit of comfort is the "jobst."
For obscure historical reasons comfort is measured inversely to the usual meaning (darn those
French engineers) and one jobst is about equal to Sheldon's Real Man Saddle, much too large for
everyday use, like Farads. Frame comfort engineers generally speak in terms of millijobsts,
although there are persistent rumors that Colnago is coming out with a frame that will break the
microjobst barrier.

Might have been the Rinard Frame Deflection Test by Damon Rinard
sheldonbrown.comrinard frametest.htmlOpen ↗

but I have to agree with Jobst Brandt, What effects of frame stiffness on riding are defined? I have
to believe measuring comfort in a bicycle frame is measured by the person riding the bike. 10
riders, 10 different opinions. -tom

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

Quoted message said:

I vaguely remember some magazine's shoot-out between frame materials. I think the biking mag did
exactly what you are suggesting (ie, built bikes with similar geometry and size out of different
metals). Darned if I can recall the results though. Maybe someone else here can remember the
details.

Jean

Quoted message said:

...snip
|
| The best way I can think of it to get frames made of different materials
in
| the same size and angles. That way, the only thing that changes is the material, not the rider's
| positioning on the bike itself.
|
| The best way to do the test is to have the same set of components put on
all
| the bikes. Run 32 hole Open Pros, with brand X tires inflated to the
same
| PSI, the same saddle, etc. That way, you isolate the way the frame
reacts
| vs. the components.
|
...snip
|
| Mike
|
|

I vaguely remember some magazine's shoot-out between frame materials. I think the biking mag did
exactly what you are suggesting (ie, built bikes with similar geometry and size out of different
metals). Darned if I can recall the results though. Maybe someone else here can remember the
details.

Jean

IIRC it was Bicycle Guide. Again, IIRC, all they did was test different steel frames. Now that
there's other things out there than steel, I'd like to see the test done again.

I'm curious to see what "the experts" think of the new materials.

Mike

<Snip>

Quoted message said:

We easily confuse what we hear with what we feel (which may explain why we misunderstand each
other so often on rec.bicycles.tech.)

Carl Fogel

Some just want to misunderstand. Gets them all excited to argue with people...

Mike

Jean said:

I vaguely remember some magazine's shoot-out between frame materials. I think the biking mag did
exactly what you are suggesting (ie, built bikes with similar geometry and size out of different
metals). Darned if I can recall the results though. Maybe someone else here can remember the
details.

Yes, the "experts" pontificated but couldn't guess which was which, even knowing what materials were
in the selection, after riding. They gave the #1 rank to the Thron bike.

--
Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971

Quoted message said:

I vaguely remember some magazine's shoot-out between frame materials. I think the biking mag did
exactly what you are suggesting (ie, built bikes with similar geometry and size out of different
metals). Darned if I can recall the results though. Maybe someone else here can remember the
details.

Jean

In 'RoadBike Action', May 1995, Vol. 3, Nr. 5, p. 12-31, ISSN 1069-2648, 'The Ultimate Road Bike
Shootout' was made with 5 'identical' bikes made by a Harry Havnoonian in the different materials,
steel, aluminium, titanium, carbon fiber and metal matrix.

----
Jan Kloster Staunstrup GIM-lab. Aalborg University, Denmark.

"staunstrup" <[email hidden]> wrote in message "]news:[email hidden]...
|
| > I vaguely remember some magazine's shoot-out between frame materials. I think the biking mag did
| > exactly what you are suggesting (ie, built
bikes
| > with similar geometry and size out of different metals). Darned if I
can
| > recall the results though. Maybe someone else here can remember the details.
| >
| >
| > Jean
| >
|
|
| In 'RoadBike Action', May 1995, Vol. 3, Nr. 5, p. 12-31, ISSN 1069-2648, 'The Ultimate Road Bike
| Shootout' was made with 5 'identical' bikes made
by
| a Harry Havnoonian in the different materials, steel, aluminium,
titanium,
| carbon fiber and metal matrix.
|
| ----
| Jan Kloster Staunstrup GIM-lab. Aalborg University, Denmark.
|
|

The shoot-out you cite sounds familiar (especially Havnoonian building the frames). So what were the
results of the test?

Jean

Quoted message said:

The shoot-out you cite sounds familiar (especially Havnoonian building the frames). So what were
the results of the test?

Jean

I doubt it makes sense but it goes like this:

Overall rating on a scale to 100:

(True temper) steel: 70 (Fudendo) aluminium: 80 (Furiosa) titanium: 85 (Vitesse) carbon fiber: 90
(STD tube mixture)metal matrix: 75

Components and forks was identical, but since all five was constructed with the same type of bonded
stainless steel lugs, and the test was purely subjective and filled with arguments like 'precise',
'predictible', 'sweetest', 'controlled', it speaks for it self. What about this one 'Titanium's
shock absorption qualities allow the rider to change lines....'

Then I spotted the German TOUR magazine, and have since been able to keep clear of that kind
of 'test'.

-jan

"staunstrup" <[email hidden]> wrote in message "]news:[email hidden]...
| > The shoot-out you cite sounds familiar (especially Havnoonian building
the
| > frames). So what were the results of the test?
| >
| > Jean
|
| I doubt it makes sense but it goes like this:
|
| Overall rating on a scale to 100:
|
| (True temper) steel: 70 (Fudendo) aluminium: 80 (Furiosa) titanium: 85 (Vitesse) carbon fiber: 90
| (STD tube mixture)metal matrix: 75
|
| Components and forks was identical, but since all five was constructed
with
| the same type of bonded stainless steel lugs, and the test was purely subjective and filled with
| arguments like 'precise', 'predictible', 'sweetest', 'controlled', it speaks for it self. What
| about this one 'Titanium's shock absorption qualities allow the rider to change
lines....'
|
| Then I spotted the German TOUR magazine, and have since been able to keep clear of that kind
| of 'test'.
|
| -jan
|
|

That's an interesting ranking. Glad to know it is based on "sweetness" and other such well-measured
qualities. Thanks for the info.

Jean