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winchman
06-18-2009, 06:09 AM
My friend has a bush hog he pulls behind his 50HP Kubota tractor.

When he goes over a ridge, the rear wheel on the bush hog will come off the ground and swivel around so it's sideways to the direction he's going. When the wheel touches down again, it stays sideways and digs in. This results in a shallow gouge in the ground several feet long where the rear wheel is dragging with the weight of the mower on it. Then it'll straighten itself out.

The mounting arm for the rear wheel is rather short. It pivots in the front and has several adjustment holes in the back. In order to get it down where he wants it, he's got it in the highest adjustment hole. This puts the mounting arm at an angle so the pivot for the rear wheel is tilted forward.

Would this cause the problem he's having?

For comparison, here's a typical bush hog. You can see the pivot for the rear wheel is nearly vertical.
http://www.farmstar.com/mower/srtc.jpg

On his, the forward attachment for the arm is about halfway between the gearbox and the adjustment bracket at the back of the deck.

It doesn't look like it would be too hard to add some pieces so the mounting arm would be parallel to the deck and the pivot for the rear wheel would be vertical, but we don't want to go through the trouble if that's not the problem.

Roger

chief
06-18-2009, 09:00 AM
The picture doesn't display but I have an idea of your problem, I suggest drilling a small hole on the wheel bracket and adding a small bracket to the mower deck and attach a spring or springs. This will allow the wheel pivot but also return it to it's proper position.

winchman
06-18-2009, 10:15 AM
We thought about that, but the wheel needs to be able to rotate through 360+ degrees. Any kind of spring positioning would probably be wrecked in short order.

Roger

jb-mck
06-18-2009, 10:23 AM
The 3 point hitch is too tight or does not have a hinge bracket.

Hook up the bushhog on level ground. Set the 3 point lift to the desired position. Tighten the turn buckles on the two lifting arms to keep the bushhog from swaying too much (so it's not sloppy). Loosen the third arm so it has plenty of slack. The third arm is only used for lifting.

When you pick up the bushhog, the front of the bushhog should come up first, then the 3rd arm tightens and picks up the back. You should only be able to pick the back wheel up 12-18 inches.

I hope this helps. I doubt you will have to do any fabrication work to solve this problem.

jb-mck
06-18-2009, 10:27 AM
Also, Just noticed in the photo that you have the 3rd arm in a crossed possition. Where it connects to the hog should be above pin. This will give it freedom to rotate when traversing a ridge.

Ian B
06-18-2009, 11:01 AM
I'd guess the problem lies with the angle of the pivot tub eto the ground. If it's too steep and a line drawn through it would intersect the ground behind the point of contact of the wheel, then the wheel won't castor properly. Get the angle right, it should solve the problem (I'm guessing the wheel behaves itself when it's set lower).

Either cut & re-angle the pivot tube, or remount the front of the mounting arm higher.

The bushhog looks to be mounted correctly - I'm guessing that the short sloping link that the back end of the top link is attached to is free to swing, allowing the bushhog to find its own level.

Ian

dneufell
06-18-2009, 12:20 PM
I use a chain for the top link!.....works great......
all other implements I use the steel turnbuckle and the float setting on the
3 pt. hitch...........Dean

budedm
06-18-2009, 02:18 PM
How about if you take the wheel off from the very top. In other words, where that flat washer is, just remove the whole thing. Then, cut (file?) a V across the top of the tube, perfectly in line with the direction of forward travel. Then put a pin or bolt through the pivot pin where that flat washer is. You may need to make the rod longer somehow. Make sure the pin comes out of the V notch when the mower is lowered and the wheel is on the ground. When the mower is lifted, the wheel will fall and the pin will engage the V notch and the wheel will always swing forward. I know....I'm a genius. ;)

Cecil Walker
06-18-2009, 04:11 PM
Take this from a man who has sold literally thousands of rotary cutters (bush hogs).

Do just as jb-mck and/or dneufell stated....end of problem.

Cecil

Alistair Hosie
06-18-2009, 05:35 PM
You've got a nice little wheel smack on centre why not add another two .One each side so that it becomes more stable in use.Alistair

laddy
06-18-2009, 07:03 PM
I don't have a bush hog. What do you mean that the pin where it hits the hog should be above pin??? Thanks Fred

winchman
06-18-2009, 07:14 PM
We actually made a link to go between the upper rod of the three-point hitch, thinking that might solve the problem. Unfortunately, it didn't make any difference at all.

He also tried leaving the upper link disconnected, and that didn't help either. There are some places where he needs to lift the deck, so leaving the upper link loose isn't a long term fix anyway.

We're going to go ahead and make some parts to get the support arm horizontal and the pivot vertical. I'll post some before and after pictures, and let you know how it works.

Roger

andy_b
06-18-2009, 09:10 PM
maybe i'm off base here, but i don't think it should matter how far forward the pivot is tilted (if by forward you mean the top of the pivot is titled towards the front end of the tractor). the weight of the mower should always make the wheel want to flop to the back, and not the side. are you sure something isn't hanging up on the pivot? i am assuming the pivoting wheel looks just like the one in the photos. if the caster the wheel is bolted into is straight and not angled, then i could see the problem occurring.

and Cecil, jb-mck and dneufell, thanks for the tips. i just fired up an old rotary mower i picked up (weird how this thread was posted just when i needed it), and i think i'll use a length of chain for the top link as my mower just has a rigid top mount. i took the blades off to sharpen them. what a pain in my A$$!!!!!

andy b.

knedvecki
06-18-2009, 10:43 PM
I would suspect that the wimpy piece of square tubing holding the wheel pivot is flexing / twisting to cause additional problems.

cuslog
06-18-2009, 11:13 PM
I have a John Deere "bush hog" mower that does something similar.
The rear wheel tracks straight most of the time but there's a patch of sand on our place where nothing will grow. When I go over that patch of loose sand, the rear wheel flops sideways and leaves a big furrow through the sand.
Get back onto the grass (and weeds) and it tracks straight again.
My mower has seen a rough life though and the 2 arms that come down from the pivot (King pin ?) to the axle shaft of the wheel are bent so that the axle of the wheel is no longer perpendicular to the king pin. Really, I don't quite understand the geometry there, but I think that straightening those two vertical arms would probably make mine track straight through the sand.
Might be a similar problem with your friends.

Cecil Walker
06-19-2009, 11:29 AM
Bush Hog owners manual:

http://www.bushhog.com/ContentFiles/Documents/Manuals/Squealer.pdf

clint
06-19-2009, 02:14 PM
The top link of the 3 point hitch is used for leveling the bush hog, if it's a hard plastic like wheel you can try replacing it with a rubber tire like on a utility trailer. This is if your using the bush hog to mow your lawn, or for up keep in a area you want to look good landscape wise.. if it's being used as a bush hog to clear pasture/weed control it would not matter about a little dirt being moved around, however I have also used a bush hog for mowing my lawn, works great, and takes very little time.

Also please don't take this the wrong way, but a high quality cutter will not have these types of problems, I owned a couple cheapo off brand bush hogs, then purchased a old junky looking bush hog brand I forget the model but it was high end, just old, and rusty, but worked better than any other one I ever owned, or used.

They also make bush hogs with twin trailing wheels, which may solve your problem, or make it worse ?

winchman
06-19-2009, 10:06 PM
Here's what his bush hog looked like before we modified it:
http://img.photobucket.com/albums/1003/winchman/Welding%20Projects/Bushhogandboompole005.jpg

You can see how much the pivot on his is angled forward compared to the one in the original post.


Here it is after we cut the arm and added a piece to change the angle of the pivot for the rear wheel:

http://img.photobucket.com/albums/1003/winchman/Welding%20Projects/Bushhogandboompole007.jpg

The added section was necessary to maintain the clearance between the wheel and the deck when the wheel swings all the way around.

He tried it out on several of the places where had been gouging the ground, and it worked like it's supposed to. It also works better when he backs up with the deck lowered.

It looks like we cured the problem.

Roger