[UK-CONTEST] Gin Poles/Falling Derricks

[Paul_group]

On 23/06/2010 17:05, Robin Thompson wrote:
> I managed to find a couple of feet of steel tubing with the same i/d as the
> ali scaffold poles to bridge the join around one of those stupidly designed
> couplers - been up for 20 odd years now with no problems...
>
> 73
> Robin
> G3TKF
>


Hi Robin

Its worth noting for anyone else contemplating using this method of 
connection that un protected steel / aluminium interfaces are quite poor 
for corrosion. this is a concern where it cant be inspected. The 
connector should be radiused at each end to avoid a sharp transition and 
thus fracture point.

Using a solid section here would be very dangerous as water needs to run 
down the inside past the connection and out of the bottom of the 
structure. Take care if you set the bottom of the tube into the ground 
even by accident, a slug of soil will prevent drainage. Look from time 
to time that water isn't trapped. This is by far the most common failure 
point of vertical tube structures - assuming they were designed properly 
and not overloaded in the first place.

When you have climbed a 150 foot tubular mast dragging a gin pole up 
behind you it tends to focus the mind on how good the connectors are and 
whether there has been any frost damage. Of course we are no longer 
allowed to climb them!



Regards Paul



>> -----Original Message-----
>> From: uk-contest-bounces at contesting.com [mailto:uk-contest-
>> bounces at contesting.com] On Behalf Of Pete Lindsay
>> Sent: 23 June 2010 13:26
>> To: Tom Boucher
>> Cc: uk-contest at contesting.com
>> Subject: Re: [UK-CONTEST] Gin Poles/Falling Derricks
>>
>> Tom ,
>>
>> Just use a standard scaffolding coupler they are cheap and very
>> strong. I have had many "jaybeam" type couplers fail but since
>> changing to these 20 years ago not a single problem since. When we
>> have had the occasional "incident" the coupler has never failed even
>> when the scaffolding pole has ended up looking like a banana !
>>
>>
>> Pete, G4CLA
>>
>> On 23 June 2010 11:51, Tom Boucher<tom at telemetry.demon.co.uk>  wrote:
>>> Does anyone know a source of external 2 inch mast couplers without that
>> weakening slot? They do exist because I have one. I also have some
> internal
>> expanding couplers which are probably stronger than the external things.
>>>
>>> Tom G3OLB
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>>>
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-- 
73 de Paul GW8IZR IO73TI
http://www.gw8izr.com