Today's Message Index:
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1. 09:22 AM - Re: Tail wheel strut bending (David Kulp)
2. 11:03 AM - Re: Tail wheel strut bending (John Hauck)
3. 11:14 AM - Ms. Dixie update (Paul Petty)
4. 03:40 PM - Re: Tail wheel strut bending (Dana Hague)
5. 06:02 PM - Re: Tail wheel strut bending (Jim Kmet)
6. 07:51 PM - Re: Tail wheel strut bending (David Key)
Message 1
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| Subject: | Re: Tail wheel strut bending |
Kolbers,
I've watched the thread about bending the tailwheel strut, including the
question of replacing with a solid rod rather than a tube. I'd like to
note that when considering your choice it'd be well to consider the
resistance to bending in addition to weight and cost. I tube is
inherently more rigid and resistant to bending than a solid rod even
with considerably less mass and weight. The reason is because a rod
only has surface tension on the one surface for the length of the rod,
whereas a tube has two surfaces; both the OD surface and the ID surface;
hence, almost double the surface tension of a rod.
Surface tension is the reason it's possible to float a piece of metal on
water (you all remember the kids trick of putting a straight pin on a
piece of tissue paper floating in a glass of water, and when the tissue
gets sogged and sinks, the pin is left "floating" - not really floating
in the sense of displacing an equal weight of water, but of "floating"
on the surface tension of the water in the glass) and why water skeeters
can casually skate on the surface of a pond with only the balls of their
little feet making contact with the water.
A note of interest for those who recognize the validity of the Bible, it
is worthwhile to realize that all miracles are consistent with nature,
i.e., hungry Jesus turning rock into bread was a definite no-no, but
when the two walked on the water, it was a kind of strengthening or
extension of the laws of nature, not a contradiction of those laws.
Water to wine was accelerated fermentation, etc. Cool, huh. (This
"aside" IS Kolb related because without the laws of nature, air wouldn't
support a Kolb and they'd just be funny-looking go-karts)
Anyway, back to the initial thought, please research the required wall
thickness - a piece of discarded TV antennae will NOT do the trick - but
the bottom line is, far less metal will provide far greater strength
using tubing rather than with a rod.
Dave Kulp
Bethlehem, PA
Message 2
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| Subject: | Re: Tail wheel strut bending |
Anyway, back to the initial thought, please research the required
wall thickness - a piece of discarded TV antennae will NOT do the
trick - but the bottom line is, far less metal will provide far
greater strength using tubing rather than with a rod.
Dave Kulp
Bethlehem, PA
Dave:
Lot depends on how the strut is heat treated, tube or rod.
My strut has been thoroughly tested over more than 2,500 hours in
extreme conditions with, probably, more tail wheel weight than most
mkIII's. What I fly with works well, is reliable, and will get you
there and back home.
Do have a problem with buoyancy. Can not get my tail wheel strut to
float. ;-)
john h
in soggy hauck's holler
Message 3
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| Subject: | Ms. Dixie update |
Hey gang,
Intalling the wireing harness in Ms Dixie today! Thought some of you might enjoy
a few pics. Just ate lunch and headed back to the shop. FYI these Adel clamps
work great to secure any wireing harness but are hell to install.
enjoy..... http://groups.msn.com/AerialWorld/kolbra012.msnw?Page=5
--------
Paul Petty
Kolbra #12
Ms Dixie
painting and reassembly
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=89322#89322
Message 4
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| Subject: | Re: Tail wheel strut bending |
At 12:20 PM 1/21/2007, David Kulp wrote:
>... I tube is inherently more rigid and resistant to bending than a solid
>rod even with considerably less mass and weight. The reason is because a
>rod only has surface tension on the one surface for the length of the rod,
>whereas a tube has two surfaces; both the OD surface and the ID surface;
>hence, almost double the surface tension of a rod...
Sorry, but this is incorrect. Surface tension is a phenomenon relating
only to liquids, not to solids. A solid's strength is a function of
stress, or force per cross sectional area. A solid bar is always stronger
(and stiffer) than the same diameter tubing. Actually, in bending, it's a
matter of moment of inertia. For the same weight, a tube will be stiffer,
yes, because you can make it larger diameter.
You are correct that the outer fibers are the most important; moment of
inertia equals pi*r^4/4 (double the diameter and it's 16 times
stiffer). Thus the difference between a solid bar and a piece of tubing
isn't that much. For example, a 1" solid bar is about 46% stiffer than a
1" diameter 1/8" wall tubing. The 1" solid bar is only 6.7% stiffer than a
1" diameter 1/4" wall tubing... but it IS stiffer.
-Dana
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Message 5
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| Subject: | Re: Tail wheel strut bending |
That settles it, I`m going to drill out my solid rod to make it hollow,
I`ll have the best of both. : )
----- Original Message -----
From: Dana Hague
To: kolb-list@matronics.com
Sent: Sunday, January 21, 2007 5:38 PM
Subject: Re: Kolb-List: Tail wheel strut bending
At 12:20 PM 1/21/2007, David Kulp wrote:
... I tube is inherently more rigid and resistant to bending than a
solid rod even with considerably less mass and weight. The reason is
because a rod only has surface tension on the one surface for the length
of the rod, whereas a tube has two surfaces; both the OD surface and the
ID surface; hence, almost double the surface tension of a rod...
Sorry, but this is incorrect. Surface tension is a phenomenon
relating only to liquids, not to solids. A solid's strength is a
function of stress, or force per cross sectional area. A solid bar is
always stronger (and stiffer) than the same diameter tubing. Actually,
in bending, it's a matter of moment of inertia. For the same weight, a
tube will be stiffer, yes, because you can make it larger diameter.
You are correct that the outer fibers are the most important; moment
of inertia equals pi*r^4/4 (double the diameter and it's 16 times
stiffer). Thus the difference between a solid bar and a piece of tubing
isn't that much. For example, a 1" solid bar is about 46% stiffer than
a 1" diameter 1/8" wall tubing. The 1" solid bar is only 6.7% stiffer
than a 1" diameter 1/4" wall tubing... but it IS stiffer.
-Dana
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There are no bugs in this software, only unfulfilled features.
Message 6
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| Subject: | Re: Tail wheel strut bending |
Ouch!
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