Jeff Liebermann wrote:
On Thu, 28 Aug 2008 12:07:01 +0100, Ian White GM3SEK
wrote:

On the other hand,
I've never damaged one by end-on impact.

I have. It split the tubing just below the locking area. The problem
is that there are many types of locking mechanisms. You need to know
what's inside and how it works before applying the traditional brute
force.

That's a fair point. From what Ed did (and did not) say, I was assuming
his pole had a simplest kind of tapered friction lock... which turns out
to be so. These often can be freed by end-on impact when twisting
doesn't work and squeezing might crush the thin walls.


For example, some poles use external compression or cam type locking
mechanisms:
http://www.telescopingpoles.com/specs.html
http://www.briarwoodproducts.com/newtools.htm
These do not jam and will respond properly to the inertial hammer
(brute force) disconnect method. However, they add width which is
often undesireable.

Internal locks, with expanding cores, cams, or wedges are a different
story. To prevent collapse, most become tighter when loaded in
compression, especiallyl those that take advantage of a slight conical
taper in the tubing:
http://www.google.com/patents?id=78duAAAAEBAJ
http://www.google.com/patents?id=fvc5AAAAEBAJ
http://www.google.com/patents?id=i2ZMAAAAEBAJ
http://www.google.com/patents?id=_hMBAAAAEBAJ
(Look at the drawings). Banging on these internal locks will jam them
only worse.

I couldn't find a picture of the inside of the common window washer
fiberglass pole. It has partial threads molded into the fiberglass.
1/4 turn to lock. Bang on that design, and you'll split the tubing
(like I did).



But even so... hitting something with a hammer shouldn't always be
condemned as "brute" force. Sometimes it *is* the most intelligent thing
to do.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek