Is it possible to rebuild a HST damper?

   / Is it possible to rebuild a HST damper?
  • Thread Starter
#31  
I don't think you can rebuilt it , They have oil and pressure in them ...

No, that damper definitely can't be rebuilt. Do you agree that it's shot based on the video of it being pushed down but not returning on it's own?
 
   / Is it possible to rebuild a HST damper? #32  
When its attached its extended all the way?
 
   / Is it possible to rebuild a HST damper?
  • Thread Starter
#33  
No, that damper definitely can't be rebuilt. Do you agree that it's shot based on the video of it being pushed down but not returning on it's own?

When it's attached it's not fully extended. It's about 2/3 extended. You can see in my second video above when it is in action (it's the black rubber one behind the centering damper in the front). If you put the pedal in reverse, the damper compresses. When you press the pedal forward, that damper extends.
 
   / Is it possible to rebuild a HST damper? #34  
Its looks like its junk how much is a new one ?
 
   / Is it possible to rebuild a HST damper?
  • Thread Starter
#35  
Its looks like its junk how much is a new one ?

That was my thought too. It's about $100. The original issue I'm trying to solve is the pedal not returning to center - the machine creeps when you step off the pedal. The centering damper seems to work fine; has good return rate, etc., and it's not an adjustment issue (you can adjust where the centering point is). And, I see his other damper looks like toast and am hoping that is the issue. But, I have to say, I don't quite see the relationship of how this damper influences the pedal return. I guess the pedal must need a certain amount of force from that damper, and without it the pedal somehow doesn't snap to center properly.
 
   / Is it possible to rebuild a HST damper? #36  
That was my thought too. It's about $100. The original issue I'm trying to solve is the pedal not returning to center - the machine creeps when you step off the pedal. The centering damper seems to work fine; has good return rate, etc., and it's not an adjustment issue (you can adjust where the centering point is). And, I see his other damper looks like toast and am hoping that is the issue. But, I have to say, I don't quite see the relationship of how this damper influences the pedal return. I guess the pedal must need a certain amount of force from that damper, and without it the pedal somehow doesn't snap to center properly.

Ya sometimes my tractor will creep when its real cold out then when it warms up its ok back and forth on the pedal for a bit
 
   / Is it possible to rebuild a HST damper? #37  
The damper is there so the pedals return to neutral gradually when you take your foot off. Otherwise the tractor slams to a stop like mine does. I have to let off the pedal a bit gradually.

The gas is in the damper to account for the space the rod takes up when the piston is fully seated. Some dampers just have atmospheric pressure air. There are reasons why that's not optimal in vehicle suspension but that's not relevant here.

If it is a gas pressure damper, and from the screw on the side that looks like a gas port it looks like it might be, then the other spring might be there to counteract the gas pressure. If the gas pressure is gone then the spring would be pushing the pedals past the neutral point. If it's easy to remove the spring you could try running it without to test this theory.

If there's a gas port the damper is might be rebuildable. Suspension rebuilders have equipment to put new nitrogen in shocks. But a rebuild would probably cost you about as much as the $100 for a new one.
 
   / Is it possible to rebuild a HST damper?
  • Thread Starter
#38  
The damper is there so the pedals return to neutral gradually when you take your foot off. Otherwise the tractor slams to a stop like mine does. I have to let off the pedal a bit gradually.

The gas is in the damper to account for the space the rod takes up when the piston is fully seated. Some dampers just have atmospheric pressure air. There are reasons why that's not optimal in vehicle suspension but that's not relevant here.

If it is a gas pressure damper, and from the screw on the side that looks like a gas port it looks like it might be, then the other spring might be there to counteract the gas pressure. If the gas pressure is gone then the spring would be pushing the pedals past the neutral point. If it's easy to remove the spring you could try running it without to test this theory.

If there's a gas port the damper is might be rebuildable. Suspension rebuilders have equipment to put new nitrogen in shocks. But a rebuild would probably cost you about as much as the $100 for a new one.

The one with the screw on the side is the centering damper. That one certainly controls the speed of the return and centering between fwd/reverse. But this is not the damper with the issue. The one that seems to have an issue is the one that looks like a little gas strut. I believe it's the combination of this gas strut and the centering damper which returns the pedal to neutral gradually when you take your foot off. With both disconnected and the engine off, the pedal just flops back and forth with no resistance (not sure if this changes when engine is running). At any rate, it seems the gas strut is toast per this video:
 
   / Is it possible to rebuild a HST damper? #39  
The damper is not meant to return on its own. No damper is. So the behavior looks normal to me.

In a spring-damper system, all a damper is meant to do is slow the rate of motion of the "sprung" mechanism. It's up to a spring to do the motion. So the spring is what would center things back up (in this case, there could also be something internal to the HST).

As long as the damper isn't stuck, it moves freely, and it still provides resistance when moving, then it appears to be OK.
 
   / Is it possible to rebuild a HST damper?
  • Thread Starter
#40  
The one with the screw on the side is the centering damper. That one certainly controls the speed of the return and centering between fwd/reverse. But this is not the damper with the issue. The one that seems to have an issue is the one that looks like a little gas strut. I believe it's the combination of this gas strut and the centering damper which returns the pedal to neutral gradually when you take your foot off. With both disconnected and the engine off, the pedal just flops back and forth with no resistance (not sure if this changes when engine is running). At any rate, it seems the gas strut is toast per this video:


Hmm...here are my observations:
1. when engine is running, if I push the pedal forward and let go, it moves back to center but then stops before it gets to dead center keeping the tractor in motion
2. with engine not running, if I push the pedal fwd/back and let go it seems to come back to a center position (but you can't tell if it's actually centered or just off)
3. with engine not running and with both the damper (orange) and centering damper (blue) unattached,4the pedal just flops forward and back with no resistance
4. the blue centering damper just returns to a centering position from either position
5. the orange damper has resistance pushing in, when I let go it starts to push out on its own but then stops. There is still resistance to extend it by hand.

So, there is no spring in the system. Either the orange damper provides this by providing force when it extends (and I have something to fix), or the HST provides all the 'sprung' force to return on it's own (if so, I'm screwed).

IMG_8201.jpg
 

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