ATM Re: Tall Pier for Observatory

["Roger Davis" <batsc@netspace.net.au>]

Robert Haler asked for ideas on building his pier, and  Juan Herrero
advised "came back with the following:

> The engineer suggested the following design.  Instead of using a single
20" tube. Use  four 5" tubes in square formation
> about 3 feet apart. At the end of each stage build an small cement
platform
> that interconnects the four columns. Once cured, start  the next stage on
> top of this platform. Repeat until you reach the required height. 


A friend of mine had to do the same thing to mount his C14 on a Byers mount
in his new observatory a few years back.  After we had thought about it for
a while we did the following.  We scoured junk yards for old 44 gallon
drums!  After obtaining six of them we punched out the ends, stacked the
first two and welded them together.  We had previously dug down half the
height of the 44 into the ground till we hit solid mountain (he lives at Mt
Dandenong here near Melbourne Australia) and into the hole we set the two
44's.   We mixed up a batch of 'crete in a builders mixer and filled the
drums and packed around the bottom of them too.  We then ran two lengths of
reinforcing rod into the wet 'crete to add strength for later and let it
set for a day.  After the top layer had cured we then welded another two
drums on top, again mixed enough 'crete to fill them and more reinforcing
rod, and so on.  When we got to the sixth drum it was just below the floor
level.  He then used a length of 16" sonotube to bring the pier to the
correct height, about another 5' 6" and we then fired up the old mixer
again and filled the sonotube.  Along the way we threw in the odd bit of
fencing wire and coat hangers to add a bit more strength.   At each join we
used Bondcrete to ensure a good solid join between the wet and semi-dry
concrete layers.  We then let the whole lot sit for a week to cure
properly.  The only thing that would vibrate when you gave the thing a good
kick was the old vocal chords.  Ohh, by the way if you do your pier this
way, let the 'crete set before welding, hot welding and water do not mix!! 
 

Roger Davis
Binocular & Telescope Service Centre
Heidelberg, Melbourne, Victoria, Australia