So, not exactly Excavator, but this is probably the most applicable section to put this. Problem is, the rotate function is very jumpy. Not smooth at all. The valve stack is hydraulic pilot from the joystick, no electronics. There are two sets of adjustment screws on the stack. Can't find any information from the manufacturer, can't see valve part numbers, etc. From the main stack, the hoses go to a Load Holding Motion Control valve, then to the swing motor. Is anyone familiar with this style valve stack and the adjustments?
Good day Geismar a French built road rail machine , the central screw I would guess is for stroke limiting , the offset screw I'm not so sure, but the maker will be of German make I cannot establish at this time. Kind regards Uffex
Do you mean the big offset screw? I was looking at the two threaded ones with jams nuts on the pilot side. I am thinking the smaller one is a pilot choke, and the bigger of the two for stroke limit? The motion control valve that is plumbed in the swing circuit is from Bosch/Rexroth. But I can't find any markings on the stack or even in their catalog that would hint that the stack is a Rexroth part. If I could even find the valve online, I could read the schematics and make the adjustments, but I have nothing to go on here.
Do the hoses surge? Do you have a case drain filter? If so, have you inspected contents? Check the return filter well for brass and steel. Is it related only to swing, no travel?
They don't surge that I can tell. The machine only has 500 hrs on it. New filters and total fluid change was done last week. It's in the shop for full maintenance. All other functions are smooth. I was hesitant to just start turning screws and see what happens . I have gauges, flow meters etc, I'd just really like to see the schematics or tips from anyone that has experience or seen this style valve before. Thanks for the help so far
I don't have intimate knowledge on that machine or valve bank. I troubleshoot everything based on symptoms. How many hoses go to your slew motor? Have you checked the oil in your slew gearbox. Is there any chance you have ice in the slew ring or slew box? You say your machine is pure pilot, no ppc's or pwm's With all other functions operating smoothly, we have to infer that the fault is in one of 2 subsystems, Pilot or pump through MCV. 1st step would be to T into pilot signals to spool caps. Is the pressure rise and fall smooth or erratic? That will dictate whether you look at the RCVs or the MCV.
Good day Dspin I am inclined to agree with your guess, it is a Bosch Rexwroth part, although I cannot find it in their website. My thoughts are parallel in as much I prefer to work from a Hydraulic schematic, have you tried Geismar support ? With those low hours, you should be able to get some support. Providing you measure the thread exposing to begin with, a half turn is unlikely to do harm. If you have no luck I can try my contacts working in that area, but it may take some time. Kind regards Uffex
The after sale support from them is... Lacking. We've had the field service tech here and he says it's normal. All my time in an excavator, I've never seen/felt a machine with such a temper on one function. I thought it was just me, but all the operators agree, it just doesn't feel right. To be honest... This machine highly capable, a ton of attachments, it's very useful... Like a Swiss army knife. But like a Swiss army knife it can do a lot of things, but it doesn't excel at any one of them. Any info you can dig up, I'd be very thankful. Thank you for taking an interest.
Good day Dspin I will try on your behalf I may need a serial number , looking at the main valve the caps look very much like "Linda" could you check the pump maker I suspect it is a load sensing system by "Linde", I have not seen a segmented block by that make but it is not to say that this is the Hydraulics behind the machine. Linde normally sold their pump and valve chest as a package. I will get back to you when I have some info. meanwhile if you could check out the pump make & serial number. Kind regards Uffex
There are quite a few pumps in there, but the pump that goes to the stack, is a Rexroth. The tag is below. Here is the tag on the machine also.
Good day Dspin The pump designation is for sure a Rexwroth load sensing system, as the issue is as I understand confined to the slew/swing circuit can you see any information on the slew motor? I have requested a hydraulic schematic from a couple of sources we will have to wait to see if I have luck, meanwhile I can try to connect the components from the information you provide. Kind regards Uffex
Unfortunately I will be out of the shop till Monday as I have had a death in the family. I will get more info as soon as I get into the shop. Thank you so much!
Hi Dspin Sorry you have a bad day, please take a look at the attachment when you get a moment, if your controller looks the same please try the following:- run the machine at full speed > drive the bucket cylinder to its full extreme ad hold it as to dead end the cylinder > slew the machine and see if the control is better or worse. This will give us a better picture of what the hydraulics are about, also if you can photo the hydraulic lines to the swing motor from the M.C.V. that will help this end. My contacts could not help me with information,I have Emailed Geismar copy in your mail box. Take care Uffe≈
Hi Dspin To keep you informed I have obtained a hydraulic schematic not from Geismar but a Russian post, it is rather like the Geismar back up service very faded Illegible almost useless.The symbols differ from the component makers. Kind regards Uffex
More news Dspin If my information is correct the slew motor is a Rexroth A6 motor quote “Cost savings through elimination of gear shifts ( Planetary gears ) and possibility of using smaller pumps – Compact, robust bearing system with long service life” This I suspect is the reason for poor quality slew control, more common 20 ton excavators have a smaller displacement motor driving through planetary transmissions. I would guess that space is at a premium, and omitting any transmission will lower production costs. I know that Volvo use direct slew drive on the larger wheeled machines and to the best of my knowledge has been excepted in the marketplace however, the design and make is not that of Rexwroth. The issue of control presents a challenge as the large variable displacement motor will adjust the speed according to the pressure. Improving the control unfortunately will be a method of experimentation involving both costs and time, from your comments I guess Geismar US. will be unlikely to participate. We can make suggestions to try, but we cannot be sure of success, real sorry we can not be more positive. Kind regards Uffex
I'm sorry to hear this... Thank you so much for digging into this. I am back in the shop this week, but it doesn't seem like we have many options to try and smooth this out. Many many thanks Dave
Hi Dave Something you could try without to much trouble of cost is to dampen the spool movement by use of chokes, I am not to sure of your circumstances if you sourced the machine from Geismar I would approach those folk for a return and refund if they cannot fix. There are many similar rail machines on the market without swing-slew issues. Kr Uffex
It appears there may be a set of chokes on the valve stack, hence why I was looking for a diagram of the stack. But I didn't want to start turning adjustments until I could see how it was put together. As far returning the machine... Unfortunately working for a government agency, that already signed off on the acceptance of the machine, we are stuck with it. It's a useful machine with a lot of capabilities but it's just that good at any of them. Judging by the way it is put together, we call it our "grade school science project" that we get to use in the real world.
I endorse your line of thinking a Hydraulic schematic would be real helpful, I have at this very moment received a reply from Geismar like the schematic no help at all.I have responded to the email a copy is in your PM KR Uffex
Good day Just to set the record straight Geismar service went from zero to a seven or eight thanks to a Harold Perry whom was first class support, his response enabled a good solution. Kind regards Uffex
Thanks to the data sheets that Uffex was able to get for us, I ended up finding that the breakaway pressure was set about 3 times too high. Brought it down to spec and it seems much better. Thanks for all your help! With people like this on the forum, I will definitely be sticking around and try to repay the favor.