What is this screw?

On Aug 15, 6:25*pm, Espressopithecus (Java Man)
wrote:
In article 76906c10-abc8-43c5-8b88-09ad3c1d9726@
34g2000hsh.googlegroups.com, says... Its to let out some of the energy accumulated during a hard ride so
that the frame will not get weaker with time.

And here I thought it was for tuning the frame's ride characteristics! *
Silly me!

Java

Mine goes to eleven.

In article ,
Phil W Lee phil(at)lee-family(dot)me(dot)uk wrote:

(Bob Weissman) considered Sat, 16 Aug 2008
22:17:57 GMT the perfect time to write:

OK, I'll bite on this thread.

My road bike, a Trek Pilot 5.0, has one of these bosses on the back of
the seat tube. What is this one for?

See the pic at
http://www.trekbikes.com/us/en/bikes/2008/road/pilot/pilot50/

You can move the zoomer and see the screw just above the front
derailleur on the backside of the tube.

Thanks,
- Bob

I'd guess (and it's only a guess) at a mount for some optional
mudguard (fender for the English impaired ;-) ) - I see the frame &
fork have the other necessary fittings.

To 'splain, the Pilot is Trek's "century" bike. Not quite a tourer, but
meant for non-racers who nonetheless want to ride something light and
quick, perhaps on a century ride. Thus the accommodation for fatter
tires than is usual, the fender mount, and while it's not obvious, the
bike is configured to have a hand position slightly higher than their
racier Madone (Trek says 15mm; your stem may vary).

I like to think of it as the bike Grant Petersen would make if he used
carbon fibre.

--
Ryan Cousineau http://www.wiredcola.com/
"In other newsgroups, they killfile trolls."
"In rec.bicycles.racing, we coach them."

In article ,
Clive George wrote:
wrote in message
Maybe a rear fender mount?

Admittedly, the bike doesn't look like the kind that attracts fenders.

"Designed to accommodate 28c tires as well as front and rear fenders."

Looks like you could be right :-)

All this time, I never clicked on the link which revealed this answer.

Thanks, guys.

- Bob

Ryan Cousineau wrote:
In article ,
Phil W Lee phil(at)lee-family(dot)me(dot)uk wrote:

(Bob Weissman) considered Sat, 16 Aug 2008
22:17:57 GMT the perfect time to write:

OK, I'll bite on this thread.

My road bike, a Trek Pilot 5.0, has one of these bosses on the back of
the seat tube. What is this one for?

See the pic at
http://www.trekbikes.com/us/en/bikes/2008/road/pilot/pilot50/
You can move the zoomer and see the screw just above the front
derailleur on the backside of the tube.

Thanks,
- Bob
I'd guess (and it's only a guess) at a mount for some optional
mudguard (fender for the English impaired ;-) ) - I see the frame &
fork have the other necessary fittings.

To 'splain, the Pilot is Trek's "century" bike. Not quite a tourer, but
meant for non-racers who nonetheless want to ride something light and
quick, perhaps on a century ride. Thus the accommodation for fatter
tires than is usual, the fender mount, and while it's not obvious, the
bike is configured to have a hand position slightly higher than their
racier Madone (Trek says 15mm; your stem may vary).

I like to think of it as the bike Grant Petersen would make if he used
carbon fibre.

Or the standard road bike, before silly fashion dictated impractical
frame clearances, made from CFRP.

--
Tom Sherman - Holstein-Friesland Bovinia
“Mary had a little lamb / And when she saw it sicken /
She shipped it off to Packingtown / And now it’s labeled chicken.”

In article , sunsetss0003
@REMOVETHISyahoo.com says...
Andre Jute wrote:
On Aug 15, 10:44 pm, Rex Kerr wrote:
I was looking at a coworker's bike today and noticed that it has an
interesting 'braze-on' that I've never seen before. On the bottom of
the top-tube there is a single small screw, similar to a waterbottle
screw about 1/4 of the way back from the headtube.

These fellows are sending you up, Rex. That screw may be used for
racing numbers, and often is, but that is simply because it is
conveniently placed. But that is a secondary purpose, mistaken as a
primary use only by the ignorant -- and deliberately by these
practical jokers. Nor is the screw an adjuster for some mystical tai-
chi force from the Far East.

Not at all. Instead that screw answers to standard, straightforward
physics, easy engineering. It is a Frequency Matching Device, FMD.
What it matches is the frequency of the ripples on the road, hammered
in by generations of traffic of a limited number of wheelbases
travelling at a very limited speed range, over the decades. There are
subtleties, like the top layer ripples not being precisely overlaid on
the previous generations of ripples, causing microripples, but we
should first deal with the principle before descending to details. The
bike itself has a range of vibrating frequencies depending on the tube
specification, thickness, butting, lugs, fixing methoded and so on,
amended by the microfrequencies of various more or less firmly fixed
components, several of which rotate, of course not perfectly centred,
around several non-concentric points, with their masses displaced at
the ends of pendula of various lengths.

As you can imagine, all these frequencies cause harmonics (badly named
-- they should be called disharmonics), which is the afterbirth of the
fundamental frequency, and equally dangerous as decayable waste if not
dealt with promptly. The screw which baffles you is intended to dial
out the major nexus of disharmonics caused between the road
frequencies and the bicycle frequencies, which medical science now
realizes is the main cause of RSI in cyclists (and you thought eating
tarmac is the cause of injury!).

If you are interested in the mathematics behind the science, you can
go here
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
where I show how we calculate the noise (disharmonics) an amplifier
makes. The math is the same for the combination of road disharmonics
and bike frequencies, whether beneficial (possible) or not (the more
likely case).

Of course, the screw works by providing, at a crucial point where
these additive frequencies combine themselves into higher-order
frequencies (and mostly extremely nasty odd higher orders too), a
vibration of its own, adjusted by screwing the bolt in and out to
leave less or more vibrating length unsupported. This is negative
feedback and, despite what the engineers here will tell you, is not
necesssarily a good thing, because it creates only nasty odd and
higher order residual artifacts (by its nature it cannot do otherwise,
since it starts, always, with the sum of 1 and 2 which is the odd
number 3). Here is an article describing the residuals of negative
feedback as a series of ever smaller but nastier monkeys on the back
of your music
http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
-- the same applies to unwanted vibrations in your bike, the source
of RSI.

I hope this helps bring lightness from dark. Unlike what those other
chaps told you, my explanation answers in every respect to the laws of
physics. I've put in this sentence because the less imaginative
Fogelite clowns will now tie themselves up in knots to prove their
physics is better than ours, while we get on with what is important:
women and fast cars and good liquor.

Note that a racing number hanging on this screw will disturb the
delicate balance of fundamental and disharmonic frequencies already
generated between bike and road, and finetuned with The Screw. The
heavier the number is, the less adverse the effect, because a heavier
number will send lower-order frequencies into the pipeworks, and if
the number's material is chosen correctly, they will be even order
frequencies as well, thus providing another barrier against RSI.

Next they will be selling us small wood pucks at only $500/set of 4, to
mount on our bicycles to "tune" the vibrations.

Thanks, I've just applied for the patent. ;-)

Java

In article ,
Phil W Lee phil(at)lee-family(dot)me(dot)uk wrote:

(Bob Weissman) considered Sat, 16 Aug 2008
22:17:57 GMT the perfect time to write:

OK, I'll bite on this thread.

My road bike, a Trek Pilot 5.0, has one of these bosses on the back of
the seat tube. What is this one for?

See the pic at
http://www.trekbikes.com/us/en/bikes...pilot/pilot50/

You can move the zoomer and see the screw just above the front
derailleur on the backside of the tube.

Thanks,
- Bob

I'd guess (and it's only a guess) at a mount for some optional
mudguard (fender for the English impaired ;-) ) -

A knee slapper.

--
Michael Press

In article ],
Ryan Cousineau wrote:
To 'splain, the Pilot is Trek's "century" bike. Not quite a tourer, but
meant for non-racers who nonetheless want to ride something light and
quick, perhaps on a century ride. Thus the accommodation for fatter
tires than is usual, the fender mount, and while it's not obvious, the
bike is configured to have a hand position slightly higher than their
racier Madone (Trek says 15mm; your stem may vary).

Thanks for the cogent explanation.

- Bob