First post been reading forum for several years. my experience is life long farmer, ten years cat field mechanic, two years service manager, independent mechanic 12 years. Any help would be greatly appreciated. Vibromax vm106d requires excess force to rotate steering wheel. Steering system pressure is correct, both cylinder packings are good, hmu orbital motor new. return filter replaced. The orbital motor is open centered and return oil is charge for hydrostatic pumps. There have been no other operational complaints on machine. Back pressure is my belief but not sure how to determine due to return going into both hydrostatic pumps.
Welcome to HEF kgwfarm . I'm sure someone with Vibromax knowledge will be along soon .
Have no idea about vibromax but if you wondering about the flow - check charge pressure on hydrostatic pumps, if you know the correct charge pressure that should be.
What is the models of pumps? Usually charge is 250-350 psi. But here the kicker: pressure available for the gerotor in the orbital valve have to be calculated as delta P between pumps charge pressure and whatever you have coming in to steering. For example if you have 2000 psi at port P of sterring and your charge pressures on the pump is 350, then your available pressure for steering is 1650.
Thanks for response. Will have to get pump brand when machine returns, hard to steer but is runnable and back out on a job. Charge pressure is 350 psi as per spec. Steering pressure is 2100psi, spec. 2030psi.While checking cylinder packings, rod extended, and head end line removed. No oil bypassing piston seals while turning steering wheel continuously. However significant oil flow from removed line. Could oil be back flowing from hydrostatic pumps in return line of steering motor that is also charge supply to hydrostatic pumps. Thanks again for advise will be able to do further checks when machine returns.
Hydraulic schematic for machine. Steering/charge circuit highlighted.
Check the case drain of motors for obstruction, theoretically one of the shuttle valves on Hydrostatics can have damage and passing system pressure to change circuits. But I never had that experience. Usually shuttles come together with port reliefs, it’s kind of weaker spring valves on top of a strong spring valve. Check the seat of the shuttle for damage.
2030 is a spec for orbitrol or its Vibromax specs?
Sorry, I’m driving and will be driving for two more days, can’t really look at diagram.
2030 psi is vibromax spec. Thanks. I do not have the machine at this time and may be a week or more before have it back.
Also check both pumps for being off null, that may cause some back feeding to charge circuit. But the main thing is case drain! Everything in closed loop goes through case drain!!!
To get you in right direction - rig up the line bypassing pumps to tank, after return filter. Lower the pressure 350 psi ( because you took pumps out of the picture) and see if it will get better, if it will start investigating pumps. About oil coming out: look at the diagram of orbitrol, two check valve in counter balance group, both of them will be open when steering not used because charge pressure will be feeding through tank port - so oil coming out of hoses is normal at neutral power steering. Another thing ( I’ve been burned on it recently) question diagrams and specs, there’s always discrepancies! First thing I would do is increase power steering pressure another 350 psi. Because not only you loosing 350 psi Delta P on gerotor of orbitrol but also on cylinders!
Frankly this is stupid system IMHO.
I agree with last post! Will do as advised when machine returns, and update on results. THANK'S
Get this: let’s say steering craps out, throws bunch of debris on to return filter, filter gets clogged, bypass opens up and rest of debris go straight for pumps, which closed loop and will recycle those debris killing both pumps whatever in the loop with them. Good for manufacturers - bad for owner!
Owner has been warned but had to have machine for job.
That was hypothetical - just to show the stupidity of it. Manufacturer saved money on this, if you factor in how many this units produced- lots of money. I don’t remember who told me but I think there’s the law was passed recently that manufacturer of AG and EC must separate safety systems like steering and breaks from rest of the systems - which for me only makes sense!
Hey! Check this site out - lots of good information about hydraulics! And it’s funny! http://www.insanehydraulics.com/
Still waiting on customer to get to a point where we can stop mchine to perform test. I appreciate the help, and not wanting to leave thread hanging. Originally believed machine would be available before now.
I am interested in why the orbitrol was replaced in the first place? Was it totally dead or did it become weak?
During cylinder test return line from cylinders to hmu had oil flow. Beleived internal failure of hmu. Both steering cylinders packing checked good, and steering system pressure checked good. Customer wanted to try hmu as probable cause and get machine to job site.
No, what was the initial problem? Why you started testing cylinders?
Steering wheel was requiring excessive force to rotate.
Wanted to eliminate a blown or leaking packing first.
Got it. So as far I understand with the new one it’s all the same? Want to make sure that you understand correctly - flow out of hose normal only at steering neutral! Actually if in that system if you pushing oil to the head side of the cylinder, your rod end hose is open to the return gallery of the steering system which is also a charge gallery of hydrostatics ( unless I missed a check valve in the diagram). So having flow on that hose is normal when trying to operate the steering. Plus it tees in to the head side of the another cylinder which can be leaking.
Flow i was seeing at cylinder stall and continous rotation of wheel to pressurize cylinder barrels and check leakage of seals. Return line disconnected so oil would show if seals blown. I use this test often on cylinders and don't get flow from return line that is disconnected. Sorry for long explanation just want to make sure we are discussing the same thing.
I got you! To test cylinders that way on this system you would have to disconnect steering from drive. Did you test both cylinders this way, or just one and then saw this flow and moved on to orbitrol? Because the other one might be leaking if you didn’t test it.
Tested both and witnessed flow described both times.