Waterjetting 37c - A Drilling Diversion

I was asked some questions about waterjet drilling of holes the other day, and it is amusing to remember where it all started, more than 30-years ago. My apologies again for the quality of the video, which has been transferred from 16 mm film, to half-inch tape and thence via a DVD to its current form, losing a little in each transition.

Figure 1. The Cygnet Project part 1.

Perhaps one of the more memorable parts of this was that we arrived on site on the Monday, and spent the afternoon setting up. Since there really wasn't that much to the rig we were done quite quickly, and were then faced with an hour before the end of the day. The overall object was to drill a hole 50-ft long, and we had arranged the camera crew to come for the filming on Thursday, so that we could work out all the snags first. But we had a pleasant surprise.

We put our first test nozzle on the lance, and started drilling - it drilled the full length with no problems, we added a second length - same result, and third . . . and then the fourth and within the hour we had achieved the goal for the week. (And run out of drill lengths).

We had the same sort of experience some years later in trials I helped with that were run by the University of Queensland in Australia, although this time we were self-propelling the drill head, so that when we ran out of the outer rigid frame we attached a length of hose, and it kept on drilling, until we had run through that also. Problem was that the drill was then pulling itself forward without any advance rate control, and if it went too fast it did not drill a large enough hole for some of the following structure (we had backward pointing jets for propulsion and hole cleaning).

So somewhere I have a photo of three of us holding the hose back to slow the advance as the drill moved forward, so that it would maintain the 15-cm diameter IIRC. And again we accomplished the goal well before we had expected, and without the need for a lot of sophistication in the design.

Early coal mining machines and their use

This is part of a series of Tech Talks that I write on Sundays. It is meant to provide some background information on the extraction of fossil fuels and metals from underground, both as general education and as a resource when, as with the Gulf oil disaster with the Deepwater Horizon, or with an underground mining disaster such as that at the Upper Big Branch Mine folk need to know what is going on. Thus, for example, at the beginning of the Deepwater Horizon spill, I combined some of these to describe some of the critical parts of creating a well.

Today, in that tradition, I am going to be describing how the extraction of coal progressed from manual mining of the coal, with a pick and shovel, to the next stage which was the early use of compressed air power and led into the mechanized mining that we use today. At the end of the last talk I showed the method by which the pattern of mining evolved, with a miner first undercutting the coal, then cutting vertical slots, and breaking out the ribs between to extract the coal in relatively large pieces.

Face layout at Houghton (A Pitmans Notebook, The Diary of Edward Smith, 1749).


The first step in mechanization was a change from the physical mining of the bulk of the coal, to drilling a hole in the coal face, inserting a stick of explosive, and breaking out the coal more rapidly. The miner then had to do less picking, and more loading of the coal into tubs. Initially the holes were drilled with a manual drill, with the miner bracing the bit with his body, as he turned it into the coal. The bit was held at the right height using the pinned prop that is shown in the picture.

Manual drilling a shot hole, Ashington 1911 (The Miners Anthony Burton)

Drills, over time, changed to first compressed air, and then, more recently to electric drills, though these, though more powerful, were heavier and drilling was done without the aid of the prop.

Power drilling the shot-hole (The Miners, Anthony Burton)

The shotfirer was generally the lowest level of administrator in the mine, and had to be certified, after an examination. The explosive was generally moved around in a wooden box, for protection, and fired in later years, with an electrical detonator, to allow a suitable safe distance. Earlier ignition used a burning fuse (as shown in many movies) and this was more hazardous since you could only get a certain distance away after lighting the fuse. The rod that was used to push the explosive into the hole, and stem the hole (usually with clay or coal dust) to contain the blast, was an initial sign of authority.

Charging a hole with explosive, note the wooden box. (The Miners, Anthony Burton)

Once the coal was broken into pieces, moving it with a shovel became a lot less work, than physically breaking it from the solid. But before the coal could be blasted down, it still required that it was first undercut to give a free surface to break to. And that was still done manually. Until, that is the invention of the cutter bar. Simplistically the first cutters was a series of small picks mounted into what are known as boxes, along a cutting chain that is itself fed around a long bar that is powered (very similar, on a much larger scale, to the bar of a chain saw).

The first of these was developed to help in the driving of the tunnels or rooms, from which the coal was mainly mined.

Picks on a Cutter bar (Colliery Deputy’s Handbook D.G. Maguire)

The initial bar could be swung through a 180 degree arc to undercut the coal at the face of the room, as mining advanced. The machines could cut at different heights above the floor, although the base of the seam was much preferred.

Early Arc wall cutter (Colliery Deputy’s handbook D.G. Maguire)

The earlier machines were manually moved around on rails, which in turn meant that the rails had to keep up with the face. And the early motion was relatively primitive.

With a single swing the cutter undercut the working face.

Two things remained to be mechanized. The first was breaking the coal into small enough pieces that it could be loaded into tubs or onto conveyors. A variety of different ideas were tried over the years. This one used compressed air and a variation on pneumatic pick action to break the coal:

Early percussive mining machine (The Miners, Anthony Burton)

My grandfather, I believe, worked with a variant of this machine.

But the last hold-out was to change from manually loading the coal to mechanized motion. After all If the coal was cut with power, and broken with power it made sense that it should also be loaded by power. Again there were a variety of machines that were tried, but then Joe Joy entered the picture with a machine that led into the tools of modern day mining.



And it is with this image of the Joy Gathering Arm loader (the arms rotate about their pivots to move the coal to the central conveyor) that I will pause, before moving into the modern version of this machine and its offspring. All the components for modern day machines had been invented, it was just a case of putting them together in the right way.