Re: Pedal-crank interface, fretting, and gouging.

Quoted message said:

i'm confused. if the pedal shaft is coated with re loctite , no
movement no excessive pressure will occur?
but i'm ignorant-are both shaft and crank aluminum?

The forces involved are beyond loctite's bond.

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

A Muzi said:

Quoted message said:

i'm confused. if the pedal shaft is coated with re loctite , no
movement no excessive pressure will occur?
but i'm ignorant-are both shaft and crank aluminum?

The forces involved are beyond loctite's bond.

Dear Andrew,

The forces are beyond even the grip of duct tape.

But a paste made from the wompom would work:

Now the thick inner shell of a Wompom
You can mould with a finger and thumb.
Though soft when you began it
It'll set as hard as granite
And it's quite as light as aluminium.

The full materials description follows.

Carl Fogel

You can do such a lot with a Wompom,
You can use every part of it too.
For work or for pleasure,
It's a triumph, it's a treasure,
Oh there's nothing that a Wompom cannot do.

Now the thread from the coat of the Wompom
Has the warmth and resilience of Wool
You need never wash or brush it,
It's impossible to crush it
And it shimmers like the finest sort of tulle.

So our clothes are all made from the Wompom;
Modern Gowns, Sportswear, Lingerie (Going up)
They are waterproof and plastic
Where it's needed they're elastic
And they emphasise the figure as you see.

Hail, to thee blithe Wompom.
Hail, to thee O Plant!
All-providing Wompom.
Universal Aunt!

You can shave with the rind of a Wompom,
And it acts like a soapless shampoo.
And its root in little doses
Keeps you free from halitosis
Oh, there's nothing that a Wompom cannot do,
Nothing that a Wompom cannot do,
Nothing that a Wompom cannot do.

Now the thick inner shell of a Wompom
You can mould with a finger and thumb.
Though soft when you began it
It'll set as hard as granite
And it's quite as light as aluminium.

So we make what we like from the Wompom,
And that proves very useful indeed.
From streets full of houses
To the buttons on your trousers
With a Wompom you have everything you need.

Gaudeamus Wompom,
Gladly we salute!
Vade mecum Wompom,
Philanthropic Fruit!

Oh, the thin outer leaf of the Wompom
Makes the finest Havana cigar
And its bottom simply bristles
With unusual looking thistles
But we haven't yet discovered what they are.

You can do such a lot with a Wompom,
You can use every part of it too.
For work or for pleasure,
It's a triumph, it's a treasure,
Oh there's nothing that a Wompom cannot do.

Oh, the flesh in the heart of a Wompom
Has the flavour of porterhouse steak.
And its juice is a liquor
That will get you higher quicker
And you're still lit up next morning when you wake.

Wompom! Wompom!
Let your voices ring!
Wompom! Wompom!
Evermore we sing!

To record what is what in a Wompom
Needs a book twice as thick as Who's Who
I could tell you more and more about this fascinating flora
You can shape it, you can square it,
You can drape it you can wear it,
You can ice it, You can dice it,
You can pare it, You can slice it,
Oh there's nothing that a Wompom cannot do!
Nothing that a Wompom cannot do!
Nothing that a Wompom cannot do!

A Muzi said:

Quoted message said:

i'm confused. if the pedal shaft is coated with re loctite , no
movement no excessive pressure will occur?
but i'm ignorant-are both shaft and crank aluminum?

The pedal shaft is not aluminum. Usually it's steel.

Quoted message said:

Quoted message said:

The forces involved are beyond loctite's bond.

Loctite is more than "bond." That is, it's anti-loosening properties
work differently than, say, putting Super Glue on the threads.

Loctite acts as a gap filler. In tight metallic spaces (assuming the
right types of metals) it turns to hard plastic. When it does this, it
fills the slight clearance space between a male and female thread.
This filling is beneficial in preventing loosening of threads.

Here's why: If a nut and bolt had frictionless thread, you could
loosely screw the nut onto the bolt, then grab the bolt head and let
the bolt hang vertically. The mere weight of the nut would cause it to
spin right off, sliding down the thread's helical ramp. If instead of
the nut's weight, you had a larger tensile load on the assembly, the
same thing would happen. Good thing threads have friction, right?

But threads generally have to have clearance space to allow easy
installation. So if you took a real nut and bolt and screwed them
loosely together, then hung things vertically, you can shift the nut
radially (side to side) on the bolt a few thousandths of an inch.

If you did this carefully enough, each time you shifted the nut
sideways on the bolt, it would slide down the thread ramp a little bit,
despite the friction.

You can see this on a bigger scale by making a ramp on your desk (prop
up one end of a book) and putting some small object on the ramp (maybe
an eraser). Apply force on the eraser sideways; it moves sideways, but
it also moves down the ramp a bit, despite the friction.

So a sideways relative motion of a mating thread causes some tiny loss
in bolt tension. Do it often enough - as on an old Harley Davidson -
and the tension is gone, the nut is loose, and parts are left behind on
the highway.

Hardened Loctite takes up space to prevent that side-to-side motion. I
think this action is at least as important as its adhesive action.

Now I don't know the relationship between the bond strength and the
compressive strength of hardened Loctite. If I were to try Loctite
thread locker on pedals, I'd use the purple (weakest) stuff. Maybe
it's too soft to prevent the motion in that laterally loaded
pedal-crank joint. But I'd guess it would prevent almost all of the
motion.

There are other problems with this idea, though. Not all metals
trigger the solidification of Loctite. In particular, aluminum and
plated steel aren't the greatest. See
http://www.loctite.com/int_henkel/loctite_us/index.cfm?&pageid=214&layout=2
about halfway down.

- Frank Krygowski