[Rhodes22-list] Fw: Preparing To Set New Dock Pilings With A Hydraulic Drill

[Michael Meltzer]

I am pretty sure Rodger wanted this posted to the list with the picture attached, Doing that for him now.

MJM

----- Original Message ----- 
From: Roger Pihlaja 
To: Michael Meltzer 
Sent: Sunday, June 27, 2004 5:10 PM
Subject: Fw: Preparing To Set New Dock Pilings With A Hydraulic Drill


Michael,

Enclosed is an article for the Rhodes List along with 3 annotated pictures.

Roger

_____________________________________________________________

Hi Everybody,

As many of you recall, my dock on Sanford Lake was destroyed by ice this spring.  We've spent the previous month demolishing & removing the wreckage of my dock as well my neighbor's boat hoist from in front of my property.  We are now just about ready to start building the new dock.  To that end, I've built myself a new toy, a hydraulic drill for sinking the new dock pilings.  The three attached pictures illustrate how it works.

In picture 1, you can see the entire set-up.  The hydraulic drill is run by a 6.75 hp pressure washer.  Our house well water is stepped up to 2-1/2 gal/min @ 2800 psi in the pressure washer & this high pressure water is fed to the hydraulic drill thru 25 ft of high pressure hose.  The hydraulic drill itself is fabricated from 2 inch nominal diameter, schedule 40, galvanized steel pipe & fittings.  High pressure water enters the drill thru the T-Handle on the upper end.  The drill runs hydraulically full in order to give it sufficient weight to reduce the tendency to lift up in reaction to the water jet.  There is a small hole bored in the cutting head.  The high pressure water is forced out thru this orifice at sonic velocity, about 1200 ft/sec.  Yes, this is a highly dangerous tool!  It can cut right thru your foot if you get in the way of the water jet.  That's the reason for the large T-Handle, in order to provide sufficient leverage to keep the drill under control when it is cutting.

Picture 2 is a close-up of the cutting head.  The lake bottom where I live is composed of hard gravelly mud.  Note the four 7/16 14UNC grade 8 bolts protruding out of the cutting head.  The ends of these hardened steel bolts have been ground down to chisel points and 7/16 14UNC wing nuts have been epoxied in place on each of the bolts.  These wing nuts act as "mud impellors" or stirrers.  The chisel points on the hardened steel bolts acts to pop the gravel particles loose as the hydraulic jet blasts its way down thru the hard mud.  In use, the T-Handle is used to rotate the cutting head 90 degrees back and forth.  The gravel and mud cuttings are forced up and out the annular space in between the 2 inch pipe and the bore hole.  Yes, this tool makes an incredible "mud slick".

Picture 3 shows my son, Daniel and his friend Keith using the hydraulic drill to set new stairway pilings for my next door neighbor, whose dock was also destroyed by ice this spring.  Hey, when you're trying something new, it's good to experiment with someone else's dock 1st!  Note that the hill Daniel & Keith are working on is so steep that they are both wearing climbing harnesses & belayed off to trees at the top of the hill.

The new hydraulic drill worked great its 1st time out.  The cutting rate is about 12 inch/min.  The installation of our new dock should go smoothly with this tool.

Roger Pihlaja
S/V Dynamic Equilibrium



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