We have built a few Manportable 2000 drills this year. Also we sold a 50 HP Gopher Underground drill. All of the 2000s are now equipped with our new Link Chuck. The first chuck we made has now been in steady use since September 2009. No parts have yet required replacement, not even the jaws. I don’t know if there is another chuck on the market that could work this long with no replacement parts. If there is, it is not as simple or light a device as this chuck is. It is turning out to be an amazing chuck.
We are now building a Hydracore 4000 with a single 203 HP Isuzu engine. It is one of the most powerful machines we have ever made. Its main intended use is to drill H size in fairly difficult ground conditions.
It is worth asking how much power do you need? Most people think more is always better, but there is an actual limit to how much torque should be put on the rod string, just as there is a limit to how much you can pull back on a rod string. Boart Longyear recommends as a maximum torque 410 ft-lbs. for BO, 560 ft-lbs. for NO, and 1000 ft-lbs. for HO. There are maximum speeds for drilling as well. I know that some people may have drilled faster and some others a lot slower, but I think that for BO 1800 rpm is about the maximum that can normally be used. For NO I think that 1500 rpm is a normal maximum. For HO I think the maximum figure would be 1200 rpm. Often a speed of 35 percent less than these speeds is better. Torque times rpm divided by 5252 gives you the horsepower. By doing this simple calculation you get 140 HP for BO, 159 HP for NO, and 228 for HO. Those figures are the maximum horsepower you are ever likely to need for drilling with these sizes, to any depth. You can’t put more horsepower to these rod strings without wrecking them. At lower speeds you will need proportionally less power. I think you would have to drill really deep before you would need this much power for drilling BO. Maybe it would be deeper than the tensile strength of the rods would allow.
I know that many holes have been drilled to 5000 feet or more of NO with machines with 175 HP engines. Drills with this amount of power are probably all that would ever be necessary to drill to this depth. To go deeper, the important thing is not to have more horsepower, it is to keep the rod torque low by keeping the hole in good condition.
This is why a Hydracore 2000 can keep up with much larger machines. They have enough horsepower and pullback to put an NO rod string pretty close to it’s limit for torque, even at maximum drilling speed, and also for pullback. Having more would only cause trouble.
The Hydracore 4000 we are building right now which probably will have about 180 HP available at the drill head will be able to exceed the maximum recommended torque on an HO rod at any rpm less than about 900. For HO you really don’t need more.