OP
Home-Built Hydraulic Post Pounder; Speeding up the freefall
- Thread starter KubotaCrossing
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Birdhunter1
Veteran Member
2 hour drive to st. Louis airport and about 8 hour air ride and layover time to Missoula from my house, I don't think it would fit carry on and checking in as baggage would be expensive.
However that drive time could be done in 24 if I know I have a good Elk guide at the other end. My wife can easily spend a day or week in Missoula.
The guy making the fitting for me is the high school Metal shop teacher, he took dimensions and is having a student do it as his semester exam. Donation to the class of course afterwards but he is the only one I can get to build it or take measurements. You might try a local vo-tech school if they have a machine shop and see what they can do for you.
However that drive time could be done in 24 if I know I have a good Elk guide at the other end. My wife can easily spend a day or week in Missoula.
The guy making the fitting for me is the high school Metal shop teacher, he took dimensions and is having a student do it as his semester exam. Donation to the class of course afterwards but he is the only one I can get to build it or take measurements. You might try a local vo-tech school if they have a machine shop and see what they can do for you.
OP
KubotaCrossing
Member
Rick,
I'd like to address the four hoses that you questioned. Here's the current setup:
Firstly, I don't have rear remotes on this tractor but I do have a Front End Loader and associated spool bank.
So. I tapped into Power Beyond (PB) port on the FEL spool bank. I got the idea reading the installation instructions from those guys that put out after-market remotes kits. It's a poor man's way to tap into the hydraulics.
Looking at the valve spool in my diagram. The "From Pump" line originates from the PB port on the FEL. The PB outgoing line on this valve spool connects to the other end of the line that I interrupted at the FEL.
The "WorkPortB" line is obvious. The "Tank" line goes to the hydraulic fluid filler cap on the tractor - unrestricted. That's four lines.
Why did I do it this way? Trial and error.
Originally I didn't have a PB "adapter" on this spool valve. So I plugged it. I left the Tank port line going straight to the tank on the tractor. Result: same slow up/down but my 3pt stopped working. Well thats a problem because I use the 3pt to adjust the pitch of the PP.
Then I thought about plugging the Tank port and sending all the fluid to the PB port. I caught myself before doing it. No way that line can handle all that dumped fluid.
Okay, so then I thought about plugging the Tank port, remove the PB adapter and pipe all the fluid to the Tank. Internally on the spool valve the Tank and PB port are connected if you remove the PB adapter. Well that resulted in the 3pt not working again -- there way no line returning to the FEL spool bank.
Why do I have four lines? The short answer is I need hydraulic power after this hydraulic tap, in my case the 3pt.
Whew! Remember you asked
Ed
I'd like to address the four hoses that you questioned. Here's the current setup:
Firstly, I don't have rear remotes on this tractor but I do have a Front End Loader and associated spool bank.
So. I tapped into Power Beyond (PB) port on the FEL spool bank. I got the idea reading the installation instructions from those guys that put out after-market remotes kits. It's a poor man's way to tap into the hydraulics.
Looking at the valve spool in my diagram. The "From Pump" line originates from the PB port on the FEL. The PB outgoing line on this valve spool connects to the other end of the line that I interrupted at the FEL.
The "WorkPortB" line is obvious. The "Tank" line goes to the hydraulic fluid filler cap on the tractor - unrestricted. That's four lines.
Why did I do it this way? Trial and error.
Originally I didn't have a PB "adapter" on this spool valve. So I plugged it. I left the Tank port line going straight to the tank on the tractor. Result: same slow up/down but my 3pt stopped working. Well thats a problem because I use the 3pt to adjust the pitch of the PP.
Then I thought about plugging the Tank port and sending all the fluid to the PB port. I caught myself before doing it. No way that line can handle all that dumped fluid.
Okay, so then I thought about plugging the Tank port, remove the PB adapter and pipe all the fluid to the Tank. Internally on the spool valve the Tank and PB port are connected if you remove the PB adapter. Well that resulted in the 3pt not working again -- there way no line returning to the FEL spool bank.
Why do I have four lines? The short answer is I need hydraulic power after this hydraulic tap, in my case the 3pt.
Whew! Remember you asked
Ed
Birdhunter1
Veteran Member
On my Mahindra 2638 I have found I have to bungee cord the remote valve to get constant flow and when doing that the three point wont work, but it wont drop either, so with my log splitter it will hold it where I set it then I can go full flow and run the splitter from the valve on the splitter.
The post driver should work the same way, except it has feet that rest on the ground to drive a post... however I will need it in constant flow. No problem as I'll just have to release a bungee cord between posts. This could get old fast on a job with alot of posts. BUT the on/off the tractor on a job setting 150 posts will wear you out so I either pay my dad, nephew and now my son to be on the tractor so I don't have to which saves me a ton of time and energy. I'm only 40 but on and off a tractor 150 times a day will wear you out.
My last tractor had awesome hydraulics, I wish every tractor I was ever on were setup the same way. This new one isn't the same and while it irks me everything else is much better. You may not like this news but setting this up where everything will work independently will be a headache and likely costly. Somehow you need a constant flow to the valve on your splitter and an unrestricted flow back to the hydraulic reservoir. You'd be surprised dealers and experienced operators cannot understand that but that's what you've got to have. In my search for finding a fitting off the shelf at multiple hydraulic mine repair shops, tractor dealers and oddball supply places to thread into my tractor to adapt to a 3/4" hose from the driver noone could understand why a different way wouldn't work. Then I found one Mahindra dealer in Texas who had a service manager who knew exactly what i was wanting to do and has a Shaver on an older tractor and is currently on the search for an adapter to make it work. Finally I contact the high school metals shop teacher, told him what I wanted, (come to find out) he has a post driver too and he is custom making it.
A $20 part is needed that is holding up a few thousand dollars worth of work that there is not a soul who can tell me what off the shelf thread size it is on the tractor. I'm only 40 and was running this thing with my dad when I was a kid on 4 different tractors now, its only ever worked by being piped one way.
The post driver should work the same way, except it has feet that rest on the ground to drive a post... however I will need it in constant flow. No problem as I'll just have to release a bungee cord between posts. This could get old fast on a job with alot of posts. BUT the on/off the tractor on a job setting 150 posts will wear you out so I either pay my dad, nephew and now my son to be on the tractor so I don't have to which saves me a ton of time and energy. I'm only 40 but on and off a tractor 150 times a day will wear you out.
My last tractor had awesome hydraulics, I wish every tractor I was ever on were setup the same way. This new one isn't the same and while it irks me everything else is much better. You may not like this news but setting this up where everything will work independently will be a headache and likely costly. Somehow you need a constant flow to the valve on your splitter and an unrestricted flow back to the hydraulic reservoir. You'd be surprised dealers and experienced operators cannot understand that but that's what you've got to have. In my search for finding a fitting off the shelf at multiple hydraulic mine repair shops, tractor dealers and oddball supply places to thread into my tractor to adapt to a 3/4" hose from the driver noone could understand why a different way wouldn't work. Then I found one Mahindra dealer in Texas who had a service manager who knew exactly what i was wanting to do and has a Shaver on an older tractor and is currently on the search for an adapter to make it work. Finally I contact the high school metals shop teacher, told him what I wanted, (come to find out) he has a post driver too and he is custom making it.
A $20 part is needed that is holding up a few thousand dollars worth of work that there is not a soul who can tell me what off the shelf thread size it is on the tractor. I'm only 40 and was running this thing with my dad when I was a kid on 4 different tractors now, its only ever worked by being piped one way.
Birdhunter1
Veteran Member
Short solution for you, build a hydraulic tank onto the frame of your driver, put a gas powered pump or pto powered pump on it, pipe to as a stand lone unit and start pounding posts.
CobyRupert
Super Member
Delete
OP
KubotaCrossing
Member
Lord willing we're this close >< to resolving this.
Keep the ideas coming tho fellas cause it's always a good idea to have a plan B!
Keep the ideas coming tho fellas cause it's always a good idea to have a plan B!
old and tired
Veteran Member
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Plan "C" since I like outside the box... :confused2: Cap off the air port, so that you will compress the air that's in the top to give push back pressure. I don't think it would give you full movement of the piston rod but maybe you can make faster (more) shorter pounds??
Or instead of cap it off, have some sort of a bladder tank to return air pressure to the "fall".
Or instead of cap it off, have some sort of a bladder tank to return air pressure to the "fall".
CalG
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You might "rethink" the mechanism.
Use the hydraulic cylinder to raise the weight up to a mechanical latch.
When the cylinder retracts to it;s fullest, it releases the latch by way of a mechanical link.
The weight drops in free fall. Ready to be raised again up to the latched position.
If simple dumb steel works, there is no reason to pump oil ;-)
Use the hydraulic cylinder to raise the weight up to a mechanical latch.
When the cylinder retracts to it;s fullest, it releases the latch by way of a mechanical link.
The weight drops in free fall. Ready to be raised again up to the latched position.
If simple dumb steel works, there is no reason to pump oil ;-)
CobyRupert
Super Member
I was thinking that, before I deleted my post....but that’s “cheating”. I’d be too stubborn, even if it cost me 3 times as much and took twice as long to get it working; there’s a hydraulic solution dang it!
Have we determined where the restriction is yet? Spool valve? Hoses? Cylinder vent? (I assume we can eliminate back into tractor by using short big hose and a bucket? )
OP
KubotaCrossing
Member
Yepper. Back in post #14 I said:
"Several contributors have suggested that the problem is that the hydraulic fluid flow is being unduly restricted. The spool valve has a 3/4" work port. I'm currently reducing that down to 1/2" hose, then finally the port on the cylinder is only 3/8"."
In that post I outlined 3 possible ways of addressing that restriction via "plumbing" changes. I'm was looking forward to getting feedback on those approaches. Sorry for being so wordy it. No hydraulics suppliers out here so trial and error costs me about a week for each pass.
Yeah, I'm still looking to resolve this with a 100% hydraulics solution.
PS
Here's post #14:
https://www.tractorbynet.com/forums...lic-post-pounder-post5902531.html#post5902531
CobyRupert
Super Member
Ok, spool port size, hose size, cylinder port size.
My background isn’t in hydraulics, but will a 3/8” diameter (3/8” thick?) “port” have more or less resistance than (say) 10’ of 1/2” hose?
Same with spool valve: What relationship does the port size have to the internal passages?
Where do you think the major restriction is that stopping it from working? Or do you think it’s all of them adding up?
Doesn’t your second option (using 2 cylinder ports without the tee) mean less fittings?
My background isn’t in hydraulics, but will a 3/8” diameter (3/8” thick?) “port” have more or less resistance than (say) 10’ of 1/2” hose?
Same with spool valve: What relationship does the port size have to the internal passages?
Where do you think the major restriction is that stopping it from working? Or do you think it’s all of them adding up?
Doesn’t your second option (using 2 cylinder ports without the tee) mean less fittings?
Birdhunter1
Veteran Member
The issue could be the cylinder itself. The only experience I have is the Shaver that I own and a few other model Shaver copy cats. On mine the piston rod does not have seals on it just a nut and an alignment guide. If the cylinder you are using is a dual acting cylinder converted to single acting it is possible the seals on the piston are creating a drag not allowing it to drop fast.
BravoXray
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I agree. We made a driver for shoreline sheeting back in the 90's. We used a hydraulic cylinder to lift the hammer with a mechanical trip mechanism at the top that disengaged the hammer and let it fall. Worked like a charm.
You'll never be able to get the hydraulic fluid the flow out fast enough to make it work to it's potential, as flow restrictions increase the faster you try move it out of the cylinder. You are also fighting the internal friction of the piston and the friction of the glands on the rod.
If I'm not mistaken, a post pounder uses the hydraulics to raise the sledge upwards and into the channel where it compresses a very stiff spring. The latch is released and the spring adds quite a bit more downward acceleration than just gravity by itself. Stick a rail car spring in there are watch your posts turn into toothpicks !
OP
KubotaCrossing
Member
"Yeah I'm Free! Free fallin"
In the last episode of this saga I was stumped by the problem of not being able to get the weight to drop with enough force to actually drive a fence post. After several trial and error attempts I've got it fine tuned and doing what I want.
The problem boiled down to simply not being able to evacuate the hydraulic fluid in the cylinder on the down stroke fast enough. Doing the math, I would have to evacuate something like 64 ounces of fluid in under a second for this to work. It just wasn't doable with the cylinder, spool valve and plumbing I had on hand.
The solution was a simple set of mods to the hydraulic cylinder (see attached image) and converting the spool valve. Originally I started out with an off-the-shelf double-acting tie-rod cylinder. Since it's a tie-rod cylinder it was easy to take apart and reassemble. The modifications were:
1) Plug the hydraulic port on the rod-end of the cylinder, plug the B port on the spool valve and remove the hydraulic hose. My spool valve came as a 4-way with a kit to make it a 3-way. This mod effectively converts the cylinder into a single-acting cylinder.
2) Remove the plunger at the end of the rod. It's held on with a big nut so that was easy. Replace the 2" plunger with a 1"-ish O.D. disk/plunger. This replacement disk is smaller in diameter than the modified cylinder bore (see step 3) but it doesn't act as a plunger in a double-acting cylinder does. In fact, fluid passes by it easily. The purpose of the disk/plunger is two-fold:
a) prevents the rod from shooting out the end of the cylinder when the rod is fully extended
b) centers the rod in the modified cylinder on the up and down strokes
Functionally, I could have stopped here. After the first two mods I was able to get the the weight to free-fall unencumbered. But I wanted to do a little more tinkering and see if I could speed up how fast the rod extended (lifted the weight.) After trial and error, came up with mod 3.
3) Insert a smaller diameter pipe into the cylinder. This effectively reduced the bore of the cylinder and the amount of fluid needed to fill it. Wow what a difference it made.
So how and why does this work? On the up stroke, fluid is pumped into the closed cylinder. The cylinder fills to the point where pressure is finally exerted on the rod and disk/plunger equally. Fluid washes right on by the disk/plunger. Somethings got to give so the rod extends lifting the weight. On the down stroke the valve is opened and the weight pushes the fluid out. In this setup the down stroke is displacing only the equivalent volume of the rod and disk/plunger, not the whole volume of the entire cylinder bore as in the original setup. So instead of evacuating 64 ounces of fluid, it's displacing something like 14-16 ounces.
Thinking about it now. Since the fluid washes right on by the disk/plunger, I can send fluid to either the top or the bottom of the cylinder -- it doesn't matter. I'll need to take another look at that and see if I can further simplify the plumbing.
So what's next is coming up with some scheme to adjust the driver left-right and in-out. I could d it with hydraulics but think maybe first cut will be with simple turn-buckles.
Cheers!
In the last episode of this saga I was stumped by the problem of not being able to get the weight to drop with enough force to actually drive a fence post. After several trial and error attempts I've got it fine tuned and doing what I want.
The problem boiled down to simply not being able to evacuate the hydraulic fluid in the cylinder on the down stroke fast enough. Doing the math, I would have to evacuate something like 64 ounces of fluid in under a second for this to work. It just wasn't doable with the cylinder, spool valve and plumbing I had on hand.
The solution was a simple set of mods to the hydraulic cylinder (see attached image) and converting the spool valve. Originally I started out with an off-the-shelf double-acting tie-rod cylinder. Since it's a tie-rod cylinder it was easy to take apart and reassemble. The modifications were:
1) Plug the hydraulic port on the rod-end of the cylinder, plug the B port on the spool valve and remove the hydraulic hose. My spool valve came as a 4-way with a kit to make it a 3-way. This mod effectively converts the cylinder into a single-acting cylinder.
2) Remove the plunger at the end of the rod. It's held on with a big nut so that was easy. Replace the 2" plunger with a 1"-ish O.D. disk/plunger. This replacement disk is smaller in diameter than the modified cylinder bore (see step 3) but it doesn't act as a plunger in a double-acting cylinder does. In fact, fluid passes by it easily. The purpose of the disk/plunger is two-fold:
a) prevents the rod from shooting out the end of the cylinder when the rod is fully extended
b) centers the rod in the modified cylinder on the up and down strokes
Functionally, I could have stopped here. After the first two mods I was able to get the the weight to free-fall unencumbered. But I wanted to do a little more tinkering and see if I could speed up how fast the rod extended (lifted the weight.) After trial and error, came up with mod 3.
3) Insert a smaller diameter pipe into the cylinder. This effectively reduced the bore of the cylinder and the amount of fluid needed to fill it. Wow what a difference it made.
So how and why does this work? On the up stroke, fluid is pumped into the closed cylinder. The cylinder fills to the point where pressure is finally exerted on the rod and disk/plunger equally. Fluid washes right on by the disk/plunger. Somethings got to give so the rod extends lifting the weight. On the down stroke the valve is opened and the weight pushes the fluid out. In this setup the down stroke is displacing only the equivalent volume of the rod and disk/plunger, not the whole volume of the entire cylinder bore as in the original setup. So instead of evacuating 64 ounces of fluid, it's displacing something like 14-16 ounces.
Thinking about it now. Since the fluid washes right on by the disk/plunger, I can send fluid to either the top or the bottom of the cylinder -- it doesn't matter. I'll need to take another look at that and see if I can further simplify the plumbing.
So what's next is coming up with some scheme to adjust the driver left-right and in-out. I could d it with hydraulics but think maybe first cut will be with simple turn-buckles.
Cheers!
Last edited:
Birdhunter1
Veteran Member
I should have mentioned earlier the rod on the Shaver has nothing on the end except a fluted rod guide to keep it aligned in the bore of the case. Other than that it is just a rod in a tube.
