Homemade dingo brush cutter

[kevin37b]

Hard to do all that welding with no warpage . Those skids are gtb. a problem . You need castors on the front . Nice work .

 

[aczlan]

In line with what J_J said, the minimum tip speed is generally considered to be ~10,000 Feet Per Minute (FPM). A zero turn will often have tip speeds in excess of 18,000FPM.
The Bush Hog SQ series cutters have tip speeds ranging from 11,400 FPM to 14,963 FPM (per http://www.bushhog.com/images/stories/documents/manuals/SQ160.pdf).
The equation would be: (((cutting circle diameter in feet)*3.14)*RPM)=FPM Tip speed
With a 42" diameter cutting circle, the equation would be: (((42/12)*3.14)*1100)=12,089 FPM Tip speed
If you drop the RPMs to 1000, you get: (((42/12)*3.14)*1000)=10,990 FPM Tip speed
Looking at the SQ142 with its tip speed of 11,400FPM, they have the output shaft on their gearbox spinning at 1037.31 RPMs when the input shaft is at 540RPM. That means that they have a gearbox with a ratio of ~1.92 on it.

I would try to get at least 11,000 FPM in your design.

Aaron Z

 

[Xfaxman]

Looking good :thumbsup:

I also recommend a castor wheel on the front. Then with your hinge it would work just like my 7 footer.

Tilt the QA plate down so the mower can follow the dips and high spots on the ground.

 

[Msc2177]

Thanks for all the replies. I actually have a 1:1.47 gearbox. I thought previously was just 1:1 so that should help too. It may still be a little slow. My motor is rated for 590 rpms at 15.8gpm. I don't know the true output of my machine. Online specs say 11gpm so I guess I'll see how it does. I am planning to put swivel casters on it. Trying to decide placement and size. It's starting to get a little heavy and I still lack putting the pump and chain guards on.

 

[aczlan]

Thanks for all the replies. I actually have a 1:1.47 gearbox. I thought previously was just 1:1 so that should help too. It may still be a little slow. My motor is rated for 590 rpms at 15.8gpm. I don't know the true output of my machine. Online specs say 11gpm so I guess I'll see how it does. I am planning to put swivel casters on it. Trying to decide placement and size. It's starting to get a little heavy and I still lack putting the pump and chain guards on.

With a 5.9CI motor and 11.4GPM on your aux circuit (per http://www.toro.com/professional/sws/brochure/Track_specs.pdf ), that will give you an input RPM of 446 and an output RPM of 655 which gives you a blade tip speed of 7205 FPM.
If there was a way to combine in your loader hydraulics (another 6GPM @ 3000 PSI), that would give you a combined flow of 17.4 GPM which would give you a input RPM of 681, an output RPM of 1001 and a blade tip speed of 11001FPS.
At the rated output of 590RPM, you would have 867RPM on the blades for a tip speed of 9531FPS.

Aaron Z