there are a couple folks here on TBN they have threads, going for there DIY post drivers.
google below
post driver site:tractorbynet.com
above will search just tractorbynet website
might try
diy post driver site:tractorbynet.com
--some units operate on a flywheel and cable. and basicly raise a weight up in the air and let the weight come slamming down into top of post
--other units use "air" from an air compressor to raise the weight
--some others use propane or a shot gun shell. i don't remember great detail just remember it used some sort of explosive to hammer post down.
--some attach to a backhoe or excavator like boom. to pick up posts off of trailer, point the end, and hammer the post down into the ground.
--some attach to FEL (front end loader) bucket, or just FEL itself.
--i think i remember 1 attached to 3pt hitch.
--there are a few that ya attach to post top, and push post and the hammer up into the air. and hit a button and away it goes.
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--most PHD (post hold diggers) for 3pt hitch = no down force. you can normally buy a "down force kit" for PHD. all it is is a hydrualic cyinder, that helps put some extra weight / force to help it dig down.
--there can be better "tips" to the auger bits for PHD in general that can make or break how well it digs down.
--a Hydraulic motor version of a PHD (post hole digger) will allow you to reverse the auger if you are getting stuck under stuff.
--some folks have built a hydrualic version of the PHD and mounted it to there FEL.
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--for standard metal T posts. i tend to use the backhoe, i stab the T post into the ground were i want it. and since the backhoe bucket can angle and adjust nicely. i can slip top of T post in just the right location of the bucket i have (may differ what bucket you have), and just push the T post into the ground. i did bend a couple T posts out of i don't know 50 or so. a quick chain and pull out and it was removed and another one went back down.
--if you have a "hammer drill" with correct attachment. to drive down "ground rods" that are any were form 8 to 12 feet long down into the ground. they can make quick work of putting T posts into the ground.
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i am not a large fan of 3pt hitch PHD, but they are cheap and work. a down force kit can be a nice option for them. though i would most likely put cash towards a backhoe or mini ex (mini excavator) hydraulic post hold digger. the backhoe style version just makes it so much nicer to pin point were you want a post more so when working in ugly situations with hills and like. and then with a 2nd person / spotter help drilling a nice straight down hole.
if you have a truck bare min, and more so a trailer. you can normally rent a mini ex or a skid steer. with a PHD on it. that would work straight through things nice and fast. if no truck/trailer. you should be able to get it delivered or rent a trailer as well.
a reminder corner posts and like most likely cost a small fortune to deal with. regular line posts can be cheaper.
one last tid bit. if memory serves from my own searchs in the past. for hammering posts down into the ground. you don't want a "sharp needle point" but a dull wide point on them. a sharp point more likely to bust off / crack is what i came to a conclusion of. i want to say the dull point was 1 to 2 inches in diameter maybe a little bit larger.
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and will mirror others. time of year makes huge difference, spring / fall when the ground is wet. other words before crops go into the fields, or after the crops come out of the fields.
if you are having problems with a hole fill with water let it seat over night and come back next day. and retry the hole.
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one thing i have not tried because i do not have a small enough auger bit. is to drill a pilot hole in a sense. with say a 2 or 3 inch auger bit. and then see if my TLB would be able to push down a 4" to 6" wood post.
