I have had to install and/or repair over six miles of wire fence plus build several thousand feet of pipe fence for cattle handling areas, horse corrals and arenas. My high desert ground ranges from hard clay loam to rocks, with lots of mountainous, tree-filled terrain.
After trying manual post pounders, tractor loader buckets and 3 point hitch based post setters, none of them were providing good results for such a large volume of work. Manual tools are OK if you have a small project, and/or the budget and availability of young, strong laborers willing to work that hard; few will do it today. Loader buckets require multiple people and there are a lot of safety risks as well as the risk of bending the T posts and damaging the bucket if anyting slips or you hit a rock with the post. Risks multiply when trying to plant anything larger than a T post into the ground with a loader bucket. Hard, dry ground multiplies all the foregoing problems.
From strictly a cost and effort basis, it made sense to obtain something specifically intended to install fence posts.
I already had a 3 point tractor auger and had installed plenty of posts using the auger and concrete. This gets to be real expensive in terms of time, materials and labor costs.
After extensive review of available technology as well as asking around to the county extension agent, an agricultural university, feedlot operators and numerous farmers and ranchers, I went with a Rohrer pneumatic post pounder. My neighboring rancher had used their smallest model to install several miles of T post fence with good results. His only regret was that he should have bought the Rohrer pounder sooner and avoided the rotator cuff surgery on his shoulders caused by the manual tools. He also wished he had gotten a bigger model.
Contrary to most assumptions, these things do not require a big air compressor. A larger air tank will allow the pounder to install a bigger post without cycling the compressor as much, but for T posts they go in in just a few seconds. A piece of 2 3/8" steel drill stem can be pounded about 3 feet deep in hard clay loam soil in about 3 minutes. Setting up the pounder, aligning the post, etc., brings the total time budget for each post to about 4-5 minutes.
I wanted something more versatile than just a T post pounder, so I bought the largest Rohrer model, which is rated to pound 3.5" posts. I also bought adapters to handle T posts and 2 3/8" drill stem as well as 2 7/8" drill stem. Yes it was more money and is harder to use because of it's increased weight but it is not that bad. I can handle it alone and manage to put in 8' long drill stem posts at least 3 feet deep, that are plumb and accurate along a string line within a quarter of an inch. I just use a ladder or stand on the pickup tailgate or trailer to get high enough to hold the pounder atop the pipe when starting.
I already had the 110 volt shop air compressor and a gasoline generator and a small utility trailer on a pickup truck chassis to haul all of them plus the fence materials. This allows mobility all over the ranch and also serves as a mobile workshop with power tools, etc. In really rough terrain I can carry the generator and a smaller air compressor plus the post pounder on a large ATV.
I have mostly used mine for installing T posts and drill stem but have also been able to re-set old wooden posts in the soil. I also made a simple adapter from a piece of drill pipe and a heavy steel plate on the end, so that I could use the post pounder as a soil compactor. It works well. One could probably also adapt this for other uses as well. I heard of one fellow that uses his to split firewood, but I would not recommend that.
Here are a few hints that I have developed after placing several thousand posts with this device:
1. Absolutely positively maintain sufficient oil delivery to the tool! This is the number one cause of tool problems. IF the tool is properly lubricated by the operator, it has been absolutely trouble free. Without enough oil, it will overheat and bind up, and the seals will overheat. Not unlike any mechanical device that is run without enough lubricant.
2. If you need to plug your air compressor into an outlet because you lack a portable generator, use minimal extension cord and more air hoses.
3. Get a good in-line oiler for the air compressor rather than wasting time lubricating the post pounder at the air inlet after each post is installed. Make certain that the oiler is actually functioning properly. One down side to this is that the oil-filled hose will no longer be good for delivering air to paint spray guns or for inflating tires. However, the time and effort savings in my opinion are more than worth having to dedicate some air hoses to the post pounder effort.
4. Rohrer customer service was actually very good. I got lots of one-on-one help over the phone, and so far they are one of the best outfits I have dealt with in a while. They do stand behind their products.
5. Get a parts kit for spare O rings, etc., in advance so that you will have them on hand if something wears out. I would estimate that 99% of any problems would likely involve O rings and other seals. They are all standard sizes and can actually be found at any decent hardware store or auto parts store.
6. Consider cutting the bottom of the post at an angle or sharpening it in some manner. It makes a tremendous difference, especially in hard, dry ground. I now cut my drill stem posts at a 45 degree angle on the down end and it probably cuts the installation effort by at least a third. I have heard of others lubricating the bottom of the post in used motor oil or grease but I have never tried this because I have yet to find a situation that the pounder cannot handle. In certain situations like solid rock nothing of this type will typically work and you must drill holes, etc.
7. It is a good idea to wear some hearing protection because you are near the exhaust port of the pounder as well as having the concussion of the pounder occurring inches from your ears. Eye protection and good heavy gloves are also a good idea. There is enough oil in the exhaust that you should wear appropriate work clothes. This is normally not a problem if one is reasonably prepared to deal with fence installation type work.
8. I have had best luck placing drill stem type posts at least 2.5 to 3 feet deep in undisturbed soil. These have served as the basis for gate posts that have held up 10' wide welded steel gates weighing several hundred pounds that have been in operation for several years, with no problem. Punching the post into undisturbed soil effectively gives you the same effect as placing a post in a larger hole that is filled with concrete. The only difference is you eliminated the need to drill the bigger hole and also eliminated the need for the concrete.
9. Posts set in backfill, especially that which is not compacted sufficiently, will have correspondingly less success because the surrounding material is looser than undisturbed soil. In this instance I have sunk the post sometimes 2-3 feet deeper until it finally hits solid dirt underneath the fill.
10. Out here in the Southwest the top foot or so of soil can be like adobe. Sometimes this causes tractor based augers to bounce out of the holes. This usually means the pounder will simply need more time to get the job done. In a few really exceptional instances like inside a cattle pen where the soil had been compacted by animals for years, I have developed a trick of drilling a bunch of 1/8" holes in the bottom of a 5 gallon plastic bucket, placing the bucket over the intended post location, filling the bucket with water, and letting gravity do the rest. Either later that day or the next morning I have a mini soft spot right where I need it and even the toughest ground yields to the post pounder.
