On Sun, 16 May 2004 09:12:13 +0100, Tony Williams
wrote:

In article ,
T i m wrote:
Hi folks,

I'm trying to make a special drill for drilling out the stump of
a 9" sq wooden gate post but want to leave the surrounding
concrete intact.

Bizarre sideways thought.....

Hi Tony,

Sideways yes, bizarre, possibly not!

Could the stump be pumped out hydraulically,
or at least freed enough for a straight lift?

I was considering a 'straight lift' one I'd given some of the wood
somewhere to go. (ie, create a 'gap' across the middle by chain
drilling. collapse one side onto the other (creating some 'space),
extract chunks using screw eye (coach bolt) on long lever (scaffold
pole) over hole?)

Drill one hole down the centre, about an inch dia,
and right through the bottom. Fill the hole with
water until it will take no more. 1 inch steel
bar as the piston, and a sledgehammer.

I like it! ..

Only reservations (ever the pessimist)

I can't remember how 'sound' the bottom of the hole is and therefore
it might

1) blow the 'bottom' of the hole *if* it is intact.

2) Simply force the water down / sideways into the surrounding ground.

I assume of the piston 'stroke' can be made long enough (depending on
how much energy you can apply to the 'piston') the effort would still
be applied to the bottom of the post by a huge ratio even with some
'losses?

Post = 9" x 9" = 81 sq inches. Assume piston 1 sq" = 80:1 mechanical
advantage. If this was backed up with some vertical 'pre-load'
(scaffold pole tension lever from above ..) Hmmmm ;-)

The other neg might be the post being soaked my swell up and jam
itself back in the hole?

Brilliant idea though!

All the best ..

T i m