Hey Hook,
What do they do if they hit a rock. Will theses push it out of the way? What if you hit bedrock and can't go down the 7', doe they cut them off and weld on the bracket to attach the 4x4 or 6x6? I have seen these used up here but have been a little hesitant especially if you need the post in a specific spot for a deck.
The operator experience takes over. I've seen them stop and go, shift from side to side or back and forth and almost always they get them in. The machines arm moves left & right and extends out 10'. On a couple, a poured footing was discovered and they cut a 1' section out of it to get by. They carry a diamond saw and a electric jack hammer with them. On a porch I did at my local pub, we hit solid rock at about 3 feet. We cut the pipe and moved on. It's still there and hasn't moved at all after 18 months.
They can pretty much put the pipe where you want it within an inch or two. The posts can also be put in at an angle of, I believe, 5 degrees and still be ok.
you will need dynamite to use those here,, nothing but solid rock around these parts..
I guess you just scrap off the dirt and pin to rock? These are designed to go lower than the frost line depth. Not sure what it is in your area, but here it's 42". They were invented in Canada where frost depth is much deeper. The green plastic sleeve will move with the frost, not the post.
We hit bedrock/ledge here at places and don't need to go deeper if we do.
Although I've no proof, I heard Derick Jeeter, (NY Yankees) built a house ON a lake using these.
