?How to baby the HST?

[Bob_Young]

The question is whether there are any operating techniques that can be used to reduce the strain on an HST when doing ground engagement work.

I'm in the process of converting a quarter acre of former thicket and rock/trash pile into lawn for the neighbor. Started the job with the gear L4300 and used a 65" Box Blade to rip up roots, rocks and assorted junk. The L4300 had to go to the tractor shop before the job was finished to get a backhoe installed....where it's been waiting over 2 weeks for the correct subframe to arrive.

Decided to finish with the HST B7610 and a 48" BB. Am still ripping up lots of roots and stuff....and it's hard jerky going. So naturally I'm wondering whether there's anyway to reduce the wear and tear on the HST (I'm still quite new to them).

My approach has been to operate in 4WD Low range at a moderately high power setting (2000 to 2200 RPM) using only enough pedal to move at a very slow walk. The idea is to power into the roots/rocks rather than ram into them. Some of the roots are just too big and all four spin until I back off and raise the BB. My idea is that the HST should survive this if there are no large, sudden shock loads and if it is operating at less than rated power. I've been monitoring HST temperature (by feel) and it's never been more than very warm; but certainly not hot...I could leave my hand on the cooling coils indefinitely without discomfort.

So, TBN HST gurus, are there better approaches? Maybe operate at a lower RPM but with more pedal? Any obvious danger signs/sounds I should look for. Am I worrying about nothing?

When/if the L4300 returns, I'll get to dig out a few stumps and some of those big roots....life is good
Bob

 

[john_bud]

I think you are, if anything, being overly cautious. Being in 4wd and lowest range is smart. Thats where you get the most power. Running the engine at PTO speed on down to 1/2 PTO speed is fine - depends on the work. Plowing -> rpms up at PTO speed. Dragging a box blade around to smooth -> 1/2 pto speed can be used in light soils. That's more to save fuel costs than to baby the HST.

Biggest killer is low fluid level. Make sure it's up at the correct level !
Next biggest is heat. You're checking that now and that's smart. (good job!)
Last is dirty filters. Change them per schedule and you'll be fine.

My experience is that the HST is actually as tough or tougher than a gear trans. Neither are very dainty -> both can take abuse and come back for more.

Enjoy!
jb

 

[texasjohn]

John_Bud took the words out of my mouth.... agreed, you are doing all the right things... 4wd, high rpm, low speed.... it's a tractor and made to do exactly what you are doing..keep on...

 

[chrisjbell]

One thing to remember about the HST - it is a hydraulic transmission, no belts or anything like that. You're making it go by pushing fluid - you can theoritically pop a seal but as long as your relief valves are working correctly it is pretty tough to break the trans.

 

[RalphVa]

Your tractor has the same 3,000 psi system used on tanks, airplanes, ships and many other commercial equipment. It's sturdy. Change the fluid and filters on schedule and just use it. Watch the fluid level if you notice a leak; otherwise, it you fill it correctly and with the right amount at fluid/filter change time, don't worry about the level. The HST will give you a lot less grief (maybe no grief) than a clutch system.

Ralph

 

[Mike_Lipke]

[QUOTE= Maybe operate at a lower RPM but with more pedal?

This is not a good idea. When you are working that unit, 2/3 to full rpm is better for the pump.

 

[Bird]

I've been monitoring HST temperature (by feel) and it's never been more than very warm; but certainly not hot

That, in itself, is a bit surprising. It's quite normal for the hydraulic fluid to reach temperatures of 100 degrees above the ambient temperature, so in Texas, at least, you won't be holding your hand on anything with hydraulic oil in it for very long. But like the other guys have said, just go on with your work and don't worry about it.

 

[yellowandbeige]

Always warm it up well before doing any real grunt work with it. Keep the fluid and filters clean and fresh. Always operate at or near pto speeds. And work it hard without worry.
Y&B

 

[john_bud]

That, in itself, is a bit surprising. It's quite normal for the hydraulic fluid to reach temperatures of 100 degrees above the ambient temperature, so in Texas, at least, you won't be holding your hand on anything with hydraulic oil in it for very long. But like the other guys have said, just go on with your work and don't worry about it.

You got that right, Bird! My old industrial loader specs call out lift speed and load at a temperature of 160F. That was the anticipated nominal fluid temperature. I'm not so sure I would want to have 200F fluid as that will degrade the seals about faster than 160F. But, seeing it once in a while wouldn't be a surprise.