Lift arms rising by themselves

[pycoed]

I'm using a tractor with a TPH mounted implement basically for the first time ( an Universal 445DT sold as a Long445 or Allis 5045 in USA ) & running a 5 ft Rhino topper similar to a Bush Hog with a rear castor wheel.
I've selected position control & set the TPH arms for a suitable height to cut very thick 3 ft high rushes, & positioned the stop so I can get back to that height after raising the topper. I start to cut at about 3 mph but I find after 100yds or so the arms are starting to lift by themselves, so I have to hold the TPH lever down against the stop continuously. The land is basically flat, but it seems that the tussocks of rushes each push the arms a little higher until after 1-200yds the rear wheel is completely off the ground & the topper will continue to rise to max height.
Is this normal? I had assumed that once set to a height the lift arms would stay put? What should I set out to check if it does represent an issue with the hydraulics?

 

[RonMar]

Not specifically familliar with your 3PH control valve. Does it have a draft control that could perhaps be overriding your control? A loose or hung linkage could also perhaps be pulling the control valve away from center, applying pressure to the cylinder.

 

[3RRL]

I start to cut at about 3 mph but I find after 100yds or so the arms are starting to lift by themselves, so I have to hold the TPH lever down against the stop continuously.
Sounds like the lever is moving away form the stop? And when you "hold the TPH lever down against the stop", does it go back down and cut at the height you set? Is that what I'm reading? If that's what's happening, check the spring loaded friction screw that keeps your lever in the position you set it. That screw might be set to loose. Tighten it so the lever still slides but it is more snug and doesn't move with vibration. From what I read, maybe that's all it is.

 

[pycoed]

I start to cut at about 3 mph but I find after 100yds or so the arms are starting to lift by themselves, so I have to hold the TPH lever down against the stop continuously.
Sounds like the lever is moving away form the stop? And when you "hold the TPH lever down against the stop", does it go back down and cut at the height you set? Is that what I'm reading? If that's what's happening, check the spring loaded friction screw that keeps your lever in the position you set it. That screw might be set to loose. Tighten it so the lever still slides but it is more snug and doesn't move with vibration. From what I read, maybe that's all it is.

That's what you read correctly Rob, once held against the stop it cuts at the set height. When I first got this tractor (its 30 years old ) a few weeks back, I noticed the lift lever was stiff to move, so I soaked the pivot with Plus gas releasing oil. Lever now moves beautifully smoothly - obviously too smoothly. I didn't know about the friction screw! Thanks for the heads up, I'll give it a go today.

 

[3RRL]

That's what you read correctly Rob, once held against the stop it cuts at the set height. When I first got this tractor (its 30 years old ) a few weeks back, I noticed the lift lever was stiff to move, so I soaked the pivot with Plus gas releasing oil. Lever now moves beautifully smoothly - obviously too smoothly. I didn't know about the friction screw! Thanks for the heads up, I'll give it a go today.

John, boy that would be great if that's all it is. BTW, I saw a guy who used vise grips to hold position...shees.

 

[Soundguy]

3RRL gave you the correct advice.. however.. if this becomes a constan't problem.. invest in a set of limit chains.. they cost about 25-30$ or you can mke em yourself... lif tthe mower just above where youwant it.. set the chains into the bracket.. relaxe the lift.. mower settles to where you want it.. and go.. if you need to lif the mower to clear an obstacle.. no problem.. then drop it and rest assured it goes back where you want it..

( still... fix the friction disk.. if the oil is making it too smooth.. hit it with some brak cleaner spray... )

Soundguy

 

[pycoed]

3RRL gave you the correct advice.. however.. if this becomes a constan't problem.. invest in a set of limit chains.. they cost about 25-30$ or you can mke em yourself... lif tthe mower just above where youwant it.. set the chains into the bracket.. relaxe the lift.. mower settles to where you want it.. and go.. if you need to lif the mower to clear an obstacle.. no problem.. then drop it and rest assured it goes back where you want it..

( still... fix the friction disk.. if the oil is making it too smooth.. hit it with some brak cleaner spray... )

Soundguy

Seems to stay put nicely, now I've introduced some friction into the equation! Thanks for the advice, even though it WASN'T hydraulics!
Cut another 3 acres tonight, with no problems at all except the weather - now it's pouring down again & we have storms forecast for tomorrow

 

[tnau664]

I just about freaked when my lift stating doing the old rise up. I had been running a very heavy plow using the draft control instead of lift. Big Dean gave me the same advice. Tightened the screw and no more problems.

Terry