my home made hydraulic hedge cutter

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liveaboard
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my home made hydraulic hedge cutter

Post by liveaboard » Wed Mar 16, 2016 5:31 pm

hedgecutter.jpg
It’s been a slow few days here on home machinist, so I thought I’d share this hedge cutter attachment for my tractor that I built last year.
I knew I would need one when I planted the 300 meters of hedge 5 years ago. I didn’t know that they’re so expensive. I bought the old tractor for 5000 euros, and a second hand cutting attachment would cost at least as much again.
So I made my own.
It needs to be able to cut 3 meters [10 feet] out from the tractor at 3 meters [still 10 feet] high. I also wanted it to work forward, backwards, and on either side of the tractor. Vertical or horizontal of course.
I bought the cutting blades, a 2.4 meter lead screw, and 2 hydraulic motors new. 3 hydraulic cylinders I had lying around, most of the rest of the machine is made from scrap.
I couldn’t source a thin hydraulic cylinder 2.2 meters long, so I opted for a long screw driven by a little hydraulic motor to extend the boom.
Since the whole thing wants to flip over and rotate, I had some trouble coming up with a design for rotating the blade where the linkage wouldn’t be in the way; so I used a rather elaborate setup where the actuating linkage is all the way at the other end of the boom, and a telescoping torque tube will swing the blade through a pair of gears. The 2.4 meter long extension screw [actually a 22mm lead screw] is inside that.
So when the boom is retracted, there’s a screw in a 1” pipe in a 1/14” pipe in a 2” pipe in a 3” pipe in a 4” pipe.
Simple really.
I made a webpage with build photos here; http://aljezurfarm.com/hedge_cutter_project.htm
I didn’t really explain the whole machine, but you can figure it out.
And here’s a video of it working;


Russ Hanscom
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Re: my home made hydraulic hedge cutter

Post by Russ Hanscom » Wed Mar 16, 2016 8:06 pm

Very good, most ingenious. Always amazing what clever minds can create.

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Re: my home made hydraulic hedge cutter

Post by liveaboard » Thu Mar 17, 2016 5:14 am

Thanks; it was my most ambitious machine so far. I'd never worked with hydraulics before.
And of course I had no idea if it would work until it was completed, and all the hydraulic hoses made. I had a few breakages and about 5 hose failures; I seem to have the bugs ironed out now, it worked without a hitch for the last few cuttings.
Maybe I shouldn't have written that... a statement like that can cause breakage.

I'm working in another implement to collect the cuttings; on the first test it's a total failure, it doesn't wok at all.

rrnut-2
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Re: my home made hydraulic hedge cutter

Post by rrnut-2 » Thu Mar 17, 2016 6:09 am

Nice work! I had wanted to build something like that for trimming trees and brush on
snowmobile trails. Never got around to it.

Jim B

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Re: my home made hydraulic hedge cutter

Post by liveaboard » Thu Mar 17, 2016 6:14 am

It was a silly amount of work. Only worthwhile for the challenge and satisfaction of doing the thing really. And because there's no chance of working for money where I live.
However, if you do make something, make it very strong; mine gets stuck on branches thicker than about 3/4". double the torque would be good.
I'm limited by the small original hydraulic pump on the tractor. If I want more torque it means less speed.

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Re: my home made hydraulic hedge cutter

Post by Carm » Thu Mar 17, 2016 7:51 am

There should be an applause smiley.

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Re: my home made hydraulic hedge cutter

Post by RSG » Thu Mar 17, 2016 8:25 am

Really cool LB! Glad I don't have a hedge that big to trim :roll:
Vision is not seeing things as they are, but as they will be.

Russ Hanscom
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Re: my home made hydraulic hedge cutter

Post by Russ Hanscom » Thu Mar 17, 2016 9:08 am

Don't know whether you have seen them but there are really really big commercial units used to prune wind breaks and large fruit trees. They employ a series of large circular saws (20"+dia) driven by high HP electric motors. Not much slows them down but they have the advantage of a serious power source.

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Re: my home made hydraulic hedge cutter

Post by warmstrong1955 » Thu Mar 17, 2016 10:05 am

Nice!
Fun stuff designing the hydraulics!

We used to mount some Slashbuster brand hydraulic driven brush cutters on excavators at an equipment dealership I worked for some time ago.
Serious piece of gear. 48" model....with several vids.

http://www.slashbuster.com/HD480B.htm

Or....here:

https://www.youtube.com/watch?v=kVpxN1D5d6U

:)
Bill
Today's solutions are tomorrow's problems.

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Re: my home made hydraulic hedge cutter

Post by liveaboard » Thu Mar 17, 2016 6:49 pm

Yes, I spent some time going through all those youtube vids, looking for ideas.
Those massive spinning blade things look incredibly dangerous; I wonder if anyone will insure them? Imagine one getting loose, or the boom tipping, or...

I'm not sure I really designed the hydraulics; more like improvised them out of material I had or could get cheap.
I wanted to have a rack of manual levers, but the cost was just too high, not only for the valve block but for the 10 long tubes it would need. I was watching ebay for a valve block when the electric one turned up; I was the only fool brave enough to bid on it.
The tubes and fittings were a big chore and a big expense. I worked on that with the guy at a nearby tractor shop.

It occurred to me that instead of a hydraulic motor and a crankshaft to turn rotation into linear motion, I could have used a hydraulic cylinder with an automatic valve setup to make it reciprocate. Too many unknowns in that for me I decided.

Thanks for all your compliments!

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warmstrong1955
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Re: my home made hydraulic hedge cutter

Post by warmstrong1955 » Thu Mar 17, 2016 8:54 pm

Determining how oil, and how much oil, gets from point A, to point B.....that's designing. :)
That includes mechanical methods to make it happen, ie; lever, foot pedal, switch....whatever.
No matter if it's on the cheap....or with a fist-full of dollars.
It's all fun!

I know of no incidents with any of the Slashbusters where the wheel came loose. I have seen teeth fly off, and the tooth pockets with 'em. Not much seein' really...more like watchin' things fly.... A warranty thing. No one in front, and the guard catches anything toward the operator and on the sides.
First ones we sold were to the DOT in Alaska.
I can tell ya, when you stood next to one, and the wheel was fired up....it would make ya back up a step or seventeen. 4 foot in diameter and 2-1/2" thick.....and not quite balanced....whoa......
All in all....not that much heavier than a loaded bucket though....so tipping....no real concern.

:)

Bill
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Re: my home made hydraulic hedge cutter

Post by liveaboard » Fri Mar 18, 2016 8:26 am

It's true, I did have to do some calculating, and it was fun. I actually measured the oil flow [with a stopwatch as I fed it into a drum], figured out the speeds, the crankshaft torque, and the blade stress at stall.

I was thinking more of some other machines I saw with huge open circular blades; one had a group of 4, it was utterly huge. And it moves. While the blades spin unprotected by anything.

Our local county has a bulldozer-like 'forest grinder' called a Galoway 200. It has a horizontal drum of carbide stud blades where the bulldozer blade would normally be.
I saw it working; they were pushing it through the soil as it ate tree stumps, bushes, and rocks. behind it was very pretty chips and soil. not as monstrous as those machines you posted, but pretty darn impressive. They use it on abandoned or derelict land along the roads, for fire prevention. Because there is no known way to stop people from throwing cigarette butts out of their car windows.
galowtrax 200 aljezur.jpg

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