Hitachi EX15

[v8druid]

Not as I understood it .. all he proved was the left pilot worked, he still never got left slew at any point

what I'm not sure of at this point, is whether left and right are the two different slices or just the same one getting pulled left for left slew, and right for right slew

I understood he'd swapped P1 & P2 left/right supplies Muz .... at the motor?
lever right it slewed right, but no action from lever left.
with P1 /P2 swapped over lever right was nothing, but lever left made her slew right ..... with the left spool ... so spool must be working, as is the right with P1/P2 the right way round.

the slew is the same slice in the block Muz going left/right and there's no RV in the slice for the slew, so that can't be at fault.


Hitachi_EX15_Short_Service_Manual valve block P60 .pdf

[Muz]

I'm in the NW Highlands so Inverness is nearest town.

I am not 100% sure that oil is getting to the swing motor. When I swing right I can clearly feel the oil flow with my finger on the hose but I feel nothing on the left. Anyway, the pressure gauge will prove it one way or the other.

It wont .. a flow meter might tell you something but if there's no resistance to flow you will see no pressure. You need to work out what feeds each side of the slew, start with the one you know works, (your guage will help you here) look for commonality in what should be the 'other' side and try and establish back at the block how the valve works so you can start eliminating what's wrong, you wont find it until you unravel the sequence of flow .. like I said earlier.. if you can stopper it off and prove/ or not that the service its self is working from the block, you will have established something, these problems are always a conundrum .. but by a process of elimination you will get there

Where abouts in the NW are you ? .. will be up that way in two weeks for some holiday and fishing time

[nic9]

Where are you Nic .... back of beyond to be 80 miles from anywhere in the UK

trouble is with the gauges ...... if it is bleeding straight to tank you'll not get much in the way of pressure showing up .... but that in itself will at least tell you, your either losing it, or it's not getting there in the first place
stopping off the pipe after the tee-ed in gauge will tell you if there is pressure arriving at the dead end
if it is, the fault is beyond the stop off/blanked end.
if you test at P1 & P2, it'll tell you which circuit is the left and which poppet to be examining

Bloody annoying fault mate .... and almost certainly likely to be summat simple

good luck

I'm in the NW Highlands so Inverness is nearest town.

I am not 100% sure that oil is getting to the swing motor. When I swing right I can clearly feel the oil flow with my finger on the hose but I feel nothing on the left. Anyway, the pressure gauge will prove it one way or the other.

My pressure guage and assorted bits haven't turned up yet, and the weather is crap so I can't go fishing - all in all, not a happy time.

[Muz]

Nic has proved the service Muz, by swapping the pipes ...... lever left, it slewed right IIRC and lever right still would not slew left? .... Correct Nic????

Not as I understood it .. all he proved was the left pilot worked, he still never got left slew at any point

what I'm not sure of at this point, is whether left and right are the two different slices or just the same one getting pulled left for left slew, and right for right slew

[v8druid]

thought just occurred to me Muz .....

this is a similar-ish sort of fault to what our Deutche friend had a few months ago ... sort of

bleeding to tank and allowing the boom to drop ... he pulled the anti-shock valve out of his circuit which was bleeding his circuit, when stationary.

as said .... sort of ...... but very different

[v8druid]

I was on the flat emptying the bucket into the trailer when it stopped slewing.
I've ordered a pressure gauge and some bits so I can do some more testing before pulling things apart. I'm 80 miles away from help here so I need to be cautious....

Where are you Nic .... back of beyond to be 80 miles from anywhere in the UK

trouble is with the gauges ...... if it is bleeding straight to tank you'll not get much in the way of pressure showing up .... but that in itself will at least tell you, your either losing it, or it's not getting there in the first place
stopping off the pipe after the tee-ed in gauge will tell you if there is pressure arriving at the dead end
if it is, the fault is beyond the stop off/blanked end.
if you test at P1 & P2, it'll tell you which circuit is the left and which poppet to be examining

Bloody annoying fault mate .... and almost certainly likely to be summat simple

good luck

[v8druid]

Always handy to have though I dont think they will reveal much here, as Graham has said earlier ... and I mentioned here



So you need to find out which . I was suggesting earlier you stopper off both slew feeds and see if you then get an engine note change which will prove the servo operation of the left/right slew, if that works and the engine note is loaded in both directions, then the fault is in the motor I would suggest.

Nic has proved the service Muz, by swapping the pipes ...... lever left, it slewed right IIRC and lever right still would not slew left? .... Correct Nic????

the pressure has got to be going to tank and the make ups are the most likely or........ the anti-shock set up in the RVs, which looks a right can of worms.

Possible an abrupt stop, or the weight carrying the slew beyond pressurised motion, may also result in the make ups bleeding oil into the circuit, from the T line, at port M, to prevent cavitation and a little crumb/debris fragment could well have trapped the poppet open on that circuit. ....... it's sort of like a CLRV (cross line relief valve) set up on a motor, to prevent damage on start/stop/run down/run up ..... except this is stop/run down only

Certainly the easiest first port of call

[Muz]

I've ordered a pressure gauge and some bits so I can do some more testing before pulling things apart. I'm 80 miles away from help here so I need to be cautious....

Always handy to have though I dont think they will reveal much here, as Graham has said earlier ... and I mentioned here

there no change in engine note on the faulty side, its not getting loaded, but at least he can identify the faulty line and trace it back. Either the oil is going back to tank somehow, or the service isnt being pulled on.

So you need to find out which . I was suggesting earlier you stopper off both slew feeds and see if you then get an engine note change which will prove the servo operation of the left/right slew, if that works and the engine note is loaded in both directions, then the fault is in the motor I would suggest.

[nic9]

initial thoughts after a look at the manual Nic ... were you slewing on a slope ... downhill to the left, when this occurred ?????

there's two 'make up' valves in that top slice ... they allow back-flow from the T line, (which incidentally is port M, between P1 and P2, as surmised), via a poppet valve arrangement to prevent cavitation, when the slew over speeds (i.e. it free slews faster than the oil supply arrives into the motor under pressure) Page T3-2-4 .. P55/487 of the pdf

A rubber crumb or anything else in a poppet will keep it open and bleeding pressure direct to the tank.

there are also two RVs in the circuits, that look to me like balanced pressure relief valves ... same page .. same top slice ....again any slightest bit of tish in those will hold them open and dumping.
I had one of these cartridge balanced valves apart out of my Hydrema last year ... awe inspiring engineering .. but would not want to have to buy one
some tiny porting in them and ultra sensitive zebberdees ... you really need to take exceptional care stripping and handling their components

That said though ... my money's on a bit of tish in the poppet make up valve for the left slew.

The following/successive 2 pages in the manual cover the balanced RVs .... last resort stuff TBH GULP !!







[ATTACH=CONFIG]3634[/ATTACH]

I was on the flat emptying the bucket into the trailer when it stopped slewing.
I've ordered a pressure gauge and some bits so I can do some more testing before pulling things apart. I'm 80 miles away from help here so I need to be cautious....

[v8druid]

initial thoughts after a look at the manual Nic ... were you slewing on a slope ... downhill to the left, when this occurred ?????

there's two 'make up' valves in that top slice ... they allow back-flow from the T line, (which incidentally is port M, between P1 and P2, as surmised), via a poppet valve arrangement to prevent cavitation, when the slew over speeds (i.e. it free slews faster than the oil supply arrives into the motor under pressure) Page T3-2-4 .. P55/487 of the pdf

A rubber crumb or anything else in a poppet will keep it open and bleeding pressure direct to the tank.

there are also two RVs in the circuits, that look to me like balanced pressure relief valves ... same page .. same top slice ....again any slightest bit of tish in those will hold them open and dumping.
I had one of these cartridge balanced valves apart out of my Hydrema last year ... awe inspiring engineering .. but would not want to have to buy one
some tiny porting in them and ultra sensitive zebberdees ... you really need to take exceptional care stripping and handling their components

That said though ... my money's on a bit of tish in the poppet make up valve for the left slew.

The following/successive 2 pages in the manual cover the balanced RVs .... last resort stuff TBH GULP !!







tachi slew valve slice.JPG

[Muz]

might be worth pulling the park changeover section off then to look for debris ... as long as you dont take the top head off you shouldnt be interfering with any timing plates, if it only comes off with the top, you'll need to take it to a specialist , because them timing plates is black magic to fix

[nic9]

The low and high pressure zones must reverse in order to get the motor to turn the other way, so there must be a changeover valve to do that, it may just be the ball bearings right enough and a good old bit of rubber crumb has done the business. What make of drive is it ? Eaton ? sumitomo ? should be on a plate on it

It's KYB (Kayaba).

[Muz]

The low and high pressure zones must reverse in order to get the motor to turn the other way, so there must be a changeover valve to do that, it may just be the ball bearings right enough and a good old bit of rubber crumb has done the business. What make of drive is it ? Eaton ? sumitomo ? should be on a plate on it

[v8druid]

Yeah Ive not examined a swashplate drive motor for a slew drive .. only ever assumed they worked from a drive going to the 'input' shaft to drive the pistons and hence create pressure

I'd be guessing that the valve on the top is a dump at stall set up, due to the nature of the operation of the motor i.e. an RV at stall pressure ... bit of crud in the left hand valve and you'd have no drive at all and for it to occur suddenly would also support that theory ?? (perhaps)

the ball valves in the section pic

swingmotor marked.JPG

are 'praps hiding under these ......

swing marked.JPG

???

this is a damned good animation of an in line axial piston motor's function ..... only thing missing which could confuse is the drive spindle .....

I'd assume that there is a separate T line due to the need to be able to dump at stall .....
valving that feature, by conventionally just reversing the line flows could present some significant issues and much easier to just go with an additional/independant T line to bleed pressure back to free tank, as and when the motor reached a stall point

It would explain a lot

[Muz]

Yeah Ive not examined a swashplate drive motor for a slew drive .. only ever assumed they worked from a drive going to the 'input' shaft to drive the pistons and hence create pressure