at one time a number of years ago, there was a company called "Fence Hand", that I have a VCR tape of the machine, (there is no address on the tape or any more information than what I am going to type, and the only picture I have of it is on the tape) and could find nothing on the net,
The machine was a three point mount and tray that held the rod type post, (no flange stabilizer on bottom of post) A rod like in rebar,
this tray was slanted so gravity would feed the rods down,
the next item was a shaft that was drive by a hydraulic motor, and this shaft had two short arms on it, that would extend up to the tray, (on back of tray there must have been to "L" shaped stops for the rods to set against, the shaft would rotate and the arms pick up one post and swing it up and over to the "driver",
the driver was mounted about in the middle of the unit, and was an arm that pivoted, two cylinders operated, (I do not know but looked like they were operated by one valve, there may have been some type of sequencing or it may just have been the size of the the cylinders),
any way there was a tilt cylinder and driver cylinder, the tilt would tilt it 90 degrees, flat and up and down, when flat it could receive the rod from the rotating shaft,
the driver cylinder, had a driver head that was "U" shaped, (guessing there may have been a magnet in it as well to hold the fence rod until driven, there was some extensions on the "front" side of it as to catch the post as it was flipped into the driver, the second cylinder after being rotated into an up right position would then drive the post by retracting, they would raise the driver, pull forward, lay the driver flat, and load another post and repeat the process,
it had a place for rolls of wire that could unroll as one drove forward, and there was an attachment on the post loader so it could be used as wire winder as well.
one more thing the unit was three point mounted, they had feet on it and would set it down ever post, (If I was doing it I would consider either a trailer or caster type wheels on it, (they set the post depth). So one would not have to mess with an additional lever. raising and lowering the three point,
it looked fairly slick really, but the posts had to be perfect, straight, and the insulators had to be put on and taken off, (some do not like to remove them), (and the wire was the factory reels, and rolled back up on the factory reels),
at the time I was using Tee posts for most of my fencing and could not see any way of modifying it for tee posts unless one hand feed the posts on to the driver. So I never looked into it further.