Ideas for rotary cutter build

[deanwerden]

If the blades are not allowed to free swing like a brush hog what happens when you hit more solid like a sapling? If going slow enough it will probably chew through it. If a little to solid what gives at that point? Blade bend, belts slip, stub shaft bends, etc..

I have been keeping my eye out for this mythical used 4 ft bush hog for 2 years and they are either 500 bucks and rotted to sh*t or new and $1400

 

[deanwerden]

A bush hog has no belt. Mowers have belts. There are reasons for this. Good luck with whatever you decide!

How about chains then?

 

[Shaneard]

How about chains then?

I would say there's a reason nobody has ever seen a bush hog with a chain on it other than to adjust the height or for guards.

 

[jb1390]

Yes you are correct I am essentially looking at building a rear finish mower that can take care of a few saplings in the way. Similar concept to the big 8'+ bush hogs that are sometimes a 2 blade design. I am going to build one either way just thought this design would take up less space both when in use and in storage.

You already have a MMM. You are essentially talking about building another, nearly identical mower to go on the back. If the MMM was not sufficient, not sure why moving it to the back would magically make it better. If you want a bush hog, buy a bush hog. If you are really bent on building it yourself, then build a bush hog. However, I would think your efforts would be better served building something that's not already commercially available on the cheap.

There are several reasons what you are talking about is different than comparing a 6' single to a dual spindle 8' cutter. the biggest difference is blade mass. Even an 8' cutter is spinning a lot of weight off each spindle. The blade momentum does most of the work for a bushhog. Trying to scale down an 8' cutter will require significantly reducing the rotating mass, which removes a significant amount of capability. I'm also not sure how you would make the blades swing in as small of a concept as you are thinking - and if you don't you will break things often.

Just buy a 4' bushhog if you have bushhog things to do.

Don't sweat the storage - many of them live outside. Mine does...... If you are really worried about getting it inside, they store pretty well standing up.

 

[CADplans]

The easiest DIY of a mower is to make the drive a car tire.
Mount the blades on a disk of steel,,, support the disk with a couple bearings.
Mount a car tire at 90 degrees to the disk, and PTO drive the car tire.
The inflation pressure of the tire controls the slip.

This design was used by many states for highway mowing for decades.
Then,,, they got flail mowers.

 

[bspeedy]

My neighbor just bought a 4-foot woods Brush Bull for 400 bucks. Great deal.

If you are going to build what is basically a rear finish mower, why not buy a cheap 4' or 5' finish mower and start from there?

 

[deanwerden]

Ok good info, The mass of the blades makes sense, I also like the tire driven set-up.

So can we at least agree that a 2 bladed bush hog style mower with heavy folding blades would at least be more successful in cutting tall grass than a mid mounted deck. The option of buying is well, not even an option. I can buy a 45hp gearbox for 120 bucks, might have 100 bucks in steel then misc bearings ect. I doubt I will have $500 into whatever I build. New is $1400 in Canada and I don't see any used ones within a 6 hour drive

Back to the drawing board I guess

 

[shaeff]

Too bad you're not closer to me, there's a 4' tow-behind model near me, it's rusty but mostly solid, for $150. Another one further down the CL page in really nice shape for $400.

 

[bcp]

Back to your no-gearbox belt drive mower idea, there used to be many more of these around. They seem to be out of style now.

















Bruce

 

[bspeedy]

Ok good info, The mass of the blades makes sense, I also like the tire driven set-up.

So can we at least agree that a 2 bladed bush hog style mower with heavy folding blades would at least be more successful in cutting tall grass than a mid mounted deck. The option of buying is well, not even an option. I can buy a 45hp gearbox for 120 bucks, might have 100 bucks in steel then misc bearings ect. I doubt I will have $500 into whatever I build. New is $1400 in Canada and I don't see any used ones within a 6 hour drive

Back to the drawing board I guess

Sorry - I'm all for ingenuity, but throwing away 500 dollars on something that is 90% the same as a cheap-o rear finish mower is not a good plan. 500 bucks will get you a great 4' bush hog that will actually work. I like to DIY, but sometimes it just doesn't make sense. Farm implements and trailers are two of those cases.