Any hydraulic eng. designer's out there?

[jmc]

From what I have read on this thread, I thought the OP was wanting something to cut low hanging branches off tree, not cutting under brush at ground level.

It seemed relevant because he was thinking about building his own and it would be simpler if he controlled it intermittently, like the brush shark, rather than run it continuously. I haven't read that web page recently but earlier I think they discussed why they went with intermittent.

It's the same mechanism as a pruner- just mounted differently.

 

[SPYDERLK]

I did a little looking at the Samurai. Looks like it uses a stator rotor type motor. 3cuin size with 3 gpm oil and only 500psi. Thats only about 20ftlbs of torque and less than 1hp. Not sure how the motor is mounted, gear reduction or belt driven, but the 3 cuin motor with 3 gpm should spin about 230rpms. The sickle bar should be moving pretty fast, but I dont know how those sickle blades will hold up to a lot of limb cutting. Looks to me like something to trim hedges with and not trees. I think something with a little heavier cutter might do pretty well. I havent seen one in person so maybe I am just over thinking it.

The motor is mounted to drive the blade directly via an offset roller on its shaft. The pressure is an average pressure since it varies with load thruout the ~ 2" stroke of the blades. The size of the pressure spikes will vary with the force needed to make the cut. When the pressure spikes reach your system hyd relief pressure the motor stalls. -- With 2500psi relief this tends to be a little above a 1" cut in hardwood.

 

[muddstopper]

Oh if you were closer! I do appreciate your offer:thumbsup:

It will be snowing up your way before long, a trip south might be in your near future.

 

[muddstopper]

The motor is mounted to drive the blade directly via an offset roller on its shaft. The pressure is an average pressure since it varies with load thruout the ~ 2" stroke of the blades. The size of the pressure spikes will vary with the force needed to make the cut. When the pressure spikes reach your system hyd relief pressure the motor stalls. -- With 2500psi relief this tends to be a little above a 1" cut in hardwood.

That makes sense about the pressure build up. I would like to see one work, but I just dont have the need for such and attachement

 

[SPYDERLK]

That makes sense about the pressure build up. I would like to see one work, but I just dont have the need for such and attachement

Ours works well. You have to be alert when cutting in the upper size range tho. A stall, by its nature precipitous, requires that you stop forward motion quickly or risk damage.

 

[muddstopper]

Ours works well. You have to be alert when cutting in the upper size range tho. A stall, by its nature precipitous, requires that you stop forward motion quickly or risk damage.

The part about stalling and equipment damage is what would worry me. Not being a trail trimming kind of person, I see limbs in the 3-4-5in range I might be cutting. Buying a piece of equipment that according to the manufacturer is limited to cutting 1 1/2in and less dia limbs, and having to go very slow or risk stalling and damage, just doesnt appeal to me. I trim around my fields every year with a chainsaw. I cut the low hanging limbs this year and next year the bigger limbs seem to droop down to take the place of the smaller limbs. I am not cutting miles of trails or fence line so a chainsaw works well enough for what I do. Heck, my wife uses a pair of loppers to trim around the yard. A good set of loppers will cut 1 1/2 in limbs with ease. I am sure each type of equipment has its place in the real world and what will work for some, wont work for others, but I would want a demo before buying any of the equipment that has been mentioned. With a demo, you will know if it will do what you want before you lay down your hard earned cash.

 

[bigdeano]

I was going to build something to trim blackberries and tree limbs along roads. I decided for simplicity to use a 5' chainsaw bar with a hydraulic motor drive for the chain. i was going to bolt teeth every 6" on the bar to keep brush in position for cutting. Seems like it would be more durable than a sickle bar setup. I haven't built it because I don't need it that bad.

 

[MossRoad]

The problem with long blades and circular blades is pinching the blades. I know I've pinched my chainsaw many times, more-so in smaller toppings when you can't tell which way the load is sprung on the small branches. We also had a circular blade on a weed eater. Very easy to pinch that one, too. That's why the large capacity, low cycle time sickle type sounds interesting. It'll do much larger branches than a conventional sickle mower. It won't fling things like a brush or flail will when elevated 90 degrees. It seems like it would be much safer and put less vibration onto the tractor as well.