TB 1140 Slew Problems

[Taat]

Sounds like the slew brake clutch pack is worn

Maybe, but still if I understand the operation correctly then the slew brake applies after a few seconds. And if I am on an incline and pulling dirt towards me the slew brake won’t even apply because there is constant pilot pressure since I am operating the hoe attachment. And there is this slight drift when operating which is probably because the oil isn’t under pressure in the slew motor, because I believe that the machine should hold position without slew brake engaged…
Also when I had the motor apart it didn’t seem like the friction disks would be worn. And the slew brake does hold nicely, it’s just when the oil is not at the right temperature it takes more than 10 seconds to engage. When the oil is hot it engages in about 5 seconds. In the video the oil was not at a working temperature that is why it took longer.

 

[Mick-the-fitter]

So we are talking very hot thin oil, have you had the brake valves out of the motor?

 

[Taat]

Yes I did, I cleaned everything and put back together as it was.

 

[Mick-the-fitter]

Yes I did, I cleaned everything and put back together as it was.

New o rings?

 

[Taat]

New o rings?

Yes, everything. I even had the new O-rings and backup rings made for the relief valves, at the cylinder repair shop.

 

[Mick-the-fitter]

Can you just take out the brake valves for photo? Label Left and rght

 

[Taat]

Can you just take out the brake valves for photo? Label Left and rght

You mean the relief valves of the slew motor right?

 

[Mick-the-fitter]

You mean the relief valves of the slew motor right?

Yes, I’m send pictures for the right motor, the serial number was correct,

 

[Taat]

Yes, I’m send pictures for the right motor, the serial number was correct,

Thank you! I will take them out tomorrow, when I have time. What are you suspecting to be wrong with the relief valves?

 

[Mick-the-fitter]

Yes, I’m send pictures for the right motor, the serial number was correct,

Thank you! I will take them out tomorrow, when I have time. What are you suspecting to be wrong with the relief valves?

Not sure just checking orings and backing rings

 

[Taat]

Not sure just checking orings and backing rings

Hello. So I didn’t get to taking the relief valves out, but I have some screenshots from the video when I was recording the parts. The pictures ate just from one relief valve. Hope these will suffice.

 

[Mick-the-fitter]

Hello. So I didn’t get to taking the relief valves out, but I have some screenshots from the video when I was recording the parts. The pictures ate just from one relief valve. Hope these will suffice.

These are now the original seals were fitted?

 

[Taat]

These are now the original seals were fitted?

They were made according to the dimensions of old ones

 

[Mick-the-fitter]

They match what the moot or drawing says! I needed to check because if for some reason the o rings and backing rings were reversed they would cause leakage!

 

[Taat]

They match what the moot or drawing says! I needed to check because if for some reason the o rings and backing rings were reversed they would cause leakage!

Maybe I will take them out one day and replace them with the ones that were included in the seal kit that I have gotten later. Just in case if maybe the cylinder repair shop didn’t made them up to spec.

 

[Taat]

Another observation that I made when testing the leakage is that even when I don’t engage the slew function there is constant very thin drizzle of oil coming through the case drain. So to my thinking is that this oil is either coming from the makeup line through check valves (maybe I didn’t pay close enough attention to poppets and its seats), or through the main high pressure lines (that would indicate some kind of issue in the control valve…).
Or is that small drizzle of oil even though the slew controls aren’t touched normal? I don’t really know, but I think both could still create this slow drift. What do you think @Mick-the-fitter ?

 

[Mick-the-fitter]

Another observation that I made when testing the leakage is that even when I don’t engage the slew function there is constant very thin drizzle of oil coming through the case drain. So to my thinking is that this oil is either coming from the makeup line through check valves (maybe I didn’t pay close enough attention to poppets and its seats), or through the main high pressure lines (that would indicate some kind of issue in the control valve…).
Or is that small drizzle of oil even though the slew controls aren’t touched normal? I don’t really know, but I think both could still create this slow drift. What do you think @Mick-the-fitter ?

Wear is going to be the main factor here, how many hours had the machine done when you acquired it? And what regularity has there been in changing in hydraulic oil?

 

[Taat]

Wear is going to be the main factor here, how many hours had the machine done when you acquired it? And what regularity has there been in changing in hydraulic oil?

I got the machine last fall, it had about 12.200 hours, now it has about 12.500… I replaced about 120 litres of oil when I got it and its filters. No metal particles in old filters, but oil is pretty dark still as you can see in the videos I posted.
I don’t know how it was serviced prior to me but apart from this slew motor problem and a cracked valve plate in the main front pump the machine is in a pretty good shape.

 

[Mick-the-fitter]

I got the machine last fall, it had about 12.200 hours, now it has about 12.500… I replaced about 120 litres of oil when I got it and its filters. No metal particles in old filters, but oil is pretty dark still as you can see in the videos I posted.
I don’t know how it was serviced prior to me but apart from this slew motor problem and a cracked valve plate in the main front pump the machine is in a pretty good shape.

Ok so it could be down to the pistons and liner tolerances in the motor! Leakage into the case, you could check the leakage from the case when cold, hold the arm and bucket against something solid, the relief valves will dump for safety, run a hose out from the case drain to a clean drum, time the hold precisely(30 seconds) measure the oil amount,
Then do the same when up to running oil temp(hot) another clean drum and (30 seconds) measure the difference, the reliefs will open the same, and if the case amount is different the rotating parts will be the issue!

 

[Taat]

Ok so it could be down to the pistons and liner tolerances in the motor! Leakage into the case, you could check the leakage from the case when cold, hold the arm and bucket against something solid, the relief valves will dump for safety, run a hose out from the case drain to a clean drum, time the hold precisely(30 seconds) measure the oil amount,
Then do the same when up to running oil temp(hot) another clean drum and (30 seconds) measure the difference, the reliefs will open the same, and if the case amount is different the rotating parts will be the issue!

Ok that makes sense and thank you for this explanation. I will do this test as soon as I can. I believe the results will be different. The bores on the cylinder block were conical when I measured them with the micrometer, but I did not think that would be enough of a leakage to cause drift so I just reused it. I will try to make a drawing for representation.
Only the middle part of the bores would be up to tolerance (0.025mm of difference), top and bottom parts are up to 0.075mm wider than the piston width.