Hydrostatic transmission on dozers

[Andy Philpott]

Hi everyone, I am looking for advice from anyone who is or has operated bulldozers around 22 - 25 tonne with HSS trans.
I at present operate a Komatsu D65px 15 & pretty much 100% of the time push shingle in rivers as well as clearing scrub , push trees & track construction in rivers.
My machine is due for replacement & several of the options to replace it have HSS transmissions & my concern is that when pushing shingle in long slots for cuts & banks etc the trans type may suffer from overheating & premature wear!
My present machine is perfect for the job but we have to consider all options available.
I have heard from several operators that have used machines with the HSS trans & recon they may suffer under hard pushing.

Any advice would be greatly appreciated.

 

[Nige]

I don't know what others think, but IMHO if you're generally working on long pushes (over 50m one way) with a full-ish blade I would've thought that a torque converter/divider coupled to a powershift transmission would be the weapon of choice.

 

[Welder Dave]

Probably be a good idea to talk to JD or others that have Hystat dozers in that size and see what they say about long pushes. The guy that did clearing for me had a JD 850J WLT and really liked it. It replaced a smaller D6D. He also has a Case 850K? but it's half the size. The large hystat loaders seem to hold up fine doing all kinds of different jobs.

 

[lantraxco]

Hystats are the cat's ass as long as the engineers provided sufficient cooling. But then torque converters are the same game, they run at or below 95%, down to 0 at full stall, so typically you will need more cooling with the torque than with the hystats. With hystats as new, you typically see 95% pump and motor, so you lose 5% of your input horsepower to heat at the pump, and then you lose 5% of what's left at the motor to heat.

After my babbling, in a nutshell, as long as the engineers provided sufficient cooling, the hystats can push forever without doing any damage other than normal wear.

Now if we had a direct drive D8..... with a straight stack... that would be cool.

 

[Tones]

Andy, in the ambient temperatures you have there I think a hydrostatic drive would be fine.

 

[John C.]

The only big issue I've heard with hystats is the cost of repairing them when something breaks. When a power shift or converter fails, the pieces are generally left in the bottom of the case of the component. When a hystat fails, the shrapnel goes everywhere. I've seen two machines now, that weren't completely dismantled and all the components cleaned out, that failed again soon after returning them to work. The loader I've heard about cost over $50K to do the rebuild the second time. Operationally, everyone I've talked to loves running them.

 

[irncwby44]

I’m with John C on this one. Hystats are awesome to run but when and if they grenade I’ve never seen a cheap fix. Keep it cool and change the Hyd oil and filters often. Also we take oil samples on ours.

 

[Tinkerer]

I've run them. The only time I saw the convertor temp go up is when they are stuck in mud.
If the operator keeps his head out of his ### while it is heating up you shouldn't have a problem.
As long as the tracks can turn you will not have a problem. Unless there is something fundamentally wrong in the drive line before you start those hard and long pushes.