How Much Slack Do You Give Your BrushHog?

[OkieG]

Does your PTO shaft ever contact the front edge of your brush hog deck when backing up??

When brush is too thick to drive over, I will sometimes back into it, brush hog first. Any slack in the top link will allow the front of the deck to raise up if the tail wheel gets temporarily stopped.

With what I believe is only a moderate amount of slack, my deck has pinched the shield between itself and the spinning PTO shaft often enough to have worn completely through the shield.

Here's a picture of the contact I'm talking about. In this picture I have backed the tailwheel into an object that has blocked it. The front of the deck has risen and is touching the PTO shaft shield. The contact is highlighted in the picture. The shield has been replaced, however, and is still pretty new.

OkieG

 

[OkieG]

Here's a closer view of the shaft and deck pinching the shield.

OkieG

 

[OkieG]

Now, without adjusting the toplink, and with the brush hog sitting flat on the ground, here's a shot of how much toplink slack it takes for contact to occur.

Does that look like too much?

OkieG

 

[OkieG]

Once again, without moving the toplink, this picture shows how much tail drop there is for mowing across dips in the ground, or backing into a ditch, for example.

Sorry about picture quality. It was getting dark this evening when these were taken. The brush hog is hanging over some steps...my simulated ditch.

OkieG

 

[OkieG]

Finally, here's a picture of toplink fully retracted (the way I prefer to back into brush...PTO shaft can't contact deck) and fully extended (for getting weeds in ditches or slopes when I have to back up to the edge). For normal forward operation, I choose a toplink position somewhere between the two limits, but usually on the "more slack" side of middle. This picture is just to give an idea of range of motion limits with the hyd. toplink.

With the manual toplink, adjustment was a real pain (didn't get done). And to have enough slack to do some chores, risked unwanted contact when backing up. It happened often enough to ruin the original shield. Now, with the hyd. assist, I try to remember and shorten the link before backing, but the potential for contact is still there, if I forget or don't take out enough slack.

Is this an adjustment problem, only? Or is there bad geometry at work here? I know operator error is partly to blame.

OkieG

 

[JerryG]

This problem is common with compact tractors. Most brush hogs are designed with dimensions taken from utility tractors. The way to solve the problem is to drill another set of holes, lower on the BH for the lift arms. To determine the location of the pin holes, with the unit on the tractor. Level it and the see where the lift arms would be on the BH IF the lift arms were level. Drill your holes at that location. This will help maintain a more constant distant between your PTO shaft and the mower deck.

 

[OkieG]

Jerry,
So, the brush hog is sitting flat on the ground for taking the measurement? Then, adjust the 3PH lift arms until they are parallel to the ground? Then, remount the lift pins at that location. Did I get that right?

OkieG

 

[To20Chris]

Hmm, I'm going to have to think about this! I run my brush hog on an old Ferguson, it does not even have position control so I use chains to limit the height of the deck. It has a screw-type top link. But the key difference would seem to be that when I lift it it stays more-or-less level.

In your first pic, you have it raised, but the tail wheel is still on the ground? I guess I'm going to have to look at mine again to remember the geometery. I know when it is on the ground the back of the deck is supported by the wheel, the front by the chains (3ph arms on a modern 3ph), and the part that attaches to the top link is slack. I think when I lift it it uses up the slack in the top link, which raises the back.

I guess that answers your actual question - when I'm mowing and the front end of the tractor drops, the back of the deck lifts pretty quick. Which is another way of saying that I don't have much slack. The deck will be made to accomodate a certain amount of vertical angular movement on the back of the 3ph. You can obviously add to that with that hydraulic top link, but you will have to manually control it. If you try to set up too much slack, then the back will drop when you lift it - it can't tell the difference.

Sorry for rambling!

 

[KiotiJohn]

OkieG, I think I see the problem. You have the rear of the mower too low. Move it down to the first or second hole to raise the rear and lower the front. To properly use the mower, the rear should be a few inches higher than the front. The part to which I'm referring is that triangle shaped frame just in front of the tailwheel. It probably has at least 3 holes for adjustment. Try it in the first hole (lowest hole) first, and if that is too severe, move it up to the second. I suspect that when you lower your mower now, the deck will be just about even front to back and that's a mistake. Give it a shot, I think you'll quit hitting the shaft. John

 

[JerryG]

I'm sorry, after reading that it didn't sound right. Level the mower, like you are going to mow. With the mower in the mowing position, see where the lift arms would be IF they were level to the ground or deck. That is where the pins should be placed.