Homemade Hydrolic Brush Cutter/ Land Clearing attachment for Bobcat

[cnicholls]

Hey Guys... im a new poster, but year long lurker.

I am a general DIY guy with many hobbies. The most recent has been fabrication of attachments for my older 743 bobcat. I am lucky to have a awesome scrap yard that i found about an hour away from my new house. They are a scrap yard, but mostly a combine graveyard. So most of my hydraulics come from there.. motors $20 cylinders $10-$30... hoses $5 with pioneer fittings!

Anyways. I am working on my latest attachment which is a Hydraulic Brush Cutter. The main gearbox and the blades are brand new from ebay.

The gearbox is made for a pto shaft that is a 1 to 1.98 up ratio. I welded to hubs together from tractor supply for the coupler. And the steel is from scrap I had laying in the pile. The sheet is 1/8 The main 3/8 U channel is from a grain truck frame I scrapped out.

My goal is to get it done for under $500 and I am under so far.

$ 20 Used hydraulic motor
$ 45 Hoses and adaptors
$ 19 Hub assemblies
$170 40HP Gear Box PTO
$ 68 22 ｽ Blades
$ 46 Carrier Hub


Its not quite ready for a spin yet, but I wanted to share I am a newbie welder so please don稚 judge my welds too much.

 

[davo727]

Nice work! What part of the world are you in?

Im sure you plan on keeping any and all persons way far away from your machine when its operating in case anything departs. :thumbsup:

 

[cnicholls]

Hey thanks,
I am here in Toledo, OH. I have gotten allot more done in on the cutter in the last few evenings, its getting darker out earlyer so i have more time to tinker in the garage. Have been welding all the seams. I moved the push bar forward, got the saftey screen in. Added the 3x4 U channel for the bottom runners. Ill take some pictures....

Do you think a 743 will spin this ok? It has a 11 gpm standard flow.

The pump is rated at 800 -900 rpm at 17 gpm max 3400 psi.

 

[jcims]

Hey thanks,
I am here in Toledo, OH. I have gotten allot more done in on the cutter in the last few evenings, its getting darker out earlyer so i have more time to tinker in the garage. Have been welding all the seams. I moved the push bar forward, got the saftey screen in. Added the 3x4 U channel for the bottom runners. Ill take some pictures....

Do you think a 743 will spin this ok? It has a 11 gpm standard flow.

The pump is rated at 800 -900 rpm at 17 gpm max 3400 psi.

I'm not sure if this is valid with hydraulic motors, but:

( 11 gpm / 17 gpm ) * 850 rpm = 550 rpm

Looks like you nailed it.

 

[VroomVroom]

I am interested in seeing how this works out as I need something to clear alder brush on old logging roads. Keep it up, send some pics.

 

[BHD]

are your cutting blades swinging or fixed?

 

[J_J]

What you haven't told us is the displacement and rpm, and the psi rating of the hyd motor. It may be a high speed low torque motor, or a high torque low speed hyd motor. What rpm do you expect the motor to run.

Using 540 rpm from a tractor PTO, as a reference.

If the gear box were connected directly, the brush hog shaft would turn at 1,069 rpm, with the PTO at 540. If the hyd motor, can turn at 1000 rpm, then the shaft speed will be 1980 rpm. What rpm are you expecting to achieve at the brush hog shaft? All this will determine blade tip velocity. You should also think of relief valves across the hyd motor.

You mentioned a pump. Is it a pump or a hyd motor?

 

[2458n]

I think he will be using the "pump" on the bocat. The high flow pump if the Bobcat is so equipped would be 16 gpm.

 

[J_J]

Are these the figures from your Bobcat?

[ Bobcat pump is rated at 800 -900 rpm at 17 gpm max 3400 psi ].


If that is the pump on the Bobcat, then the displacement of the pump would be about 4.4 cu in. Pumping 17 GPM's at 3400 psi, would take about 40 HP. and if you select the right hyd motor, you could be putting about 34 HP out to the brush hog.

If the hyd motor is around 6 cu in, running 17 GPM through it at 3000 psi, would give a torque of 238 ft lbs,and 655 rpm from the hyd motor, turning the gear box, at a 1 : 1.89 ratio, would turn the brush hog shaft 1238 rpm.

 

[cnicholls]

The pump is from my bobcat, that is rated at 11 gpm the motor is rated at max-17gpm @ 900 rpm.

My max is 11 so it will run slower, thus approx 550 rpm I am using a stock gearbox for a pto driven brush hog. So Im thinking it should work.

I am using a swing blade design. Not sure what to expect, but im nevious to try it out. Should be ready for showtime this week, got side tracked with paying jobs... i just hate that....