FB100-Backhoe
Member
Hello guys,
I´m writing from spain, my name is Tomás, and I found this excellent forum searching internet for help with the problem (if it really is one) of my backhoe. It´s a 1999 Fiat-Hitachi FB100 with about 10.000 working hours, and I think this is very similar to some New Holand and Case backhoe models.
This machine has a conventional hydraulic system with a tandem-gear pump, no load sensing, no servo-hydraulic, no fancy joysticks. The backhoe valve assembly is built up by 4 HUSCO-valve sections, in this order (from pressure inlet): Boom-swing-bucket-dipper, all of them equipped with relief valves, except the bucket and dipper rod-end sides. Between every two sections there is a spring-loaded check-valve. There is a inlet-end cover feeding pressure to the backhoe carriage clamp-mechanism. The outlet end cover incorporates a back pressure valve and regenerative check valve.
All hydraulic is working fine, and with speed varying with motor rpm. Steering, loader and stabilizer without any problem, and even the hoe while not combining cylinder movements with the boom cylinder. I try to explain: All three cylinders (boom, dipper and bucket) have a lot of power and work with more than enough speed. Also the combination of dipper and bucket cylinder is working fine and fast. But when I try do do a combined movement including the boom cylinder, I only can do this moving either the boom very slow (this means, not to move it´s control lever more than to half it´s way or even less) or, moving boom faster but of cost of dipper oder bucket cylinder speed. A combined movement of two or three of the sections can only be done very slowly, but this independent of motor rpm. If I rise rpm the problem still is the same, only at a little bit higher "total speed", but in my opinion very below for doing a serious, paid job in a given time.
I don´t remember if this was the same when I bought the machine 10 years ago, by this time I was a total backhoe-newbie and use the machine only for pleasure doing some work on my own property. I learned how to maintenance, repair and even improve this machine; I´m not afraid of doing difficult tasks when I know what I have to do.
All the three backhoe cylinders are in well condition, they hold their position even under load, so I think I can exclude internal cylinder leakages and I suppose that the "problem" also can not be produced by bad, worn or hanging vale spools, as every one of the sections work absolutely fine. I also think that the problem will not be caused by the relief valves, because of the good load-holding of every cylinder. And I can hear them well when they begin to work moving either cylinder to it´s end position (or "overloading" it). The only items I really don´t know if the can produce this problems are the check-valves between the sections, or the back pressure valve and regenerative check valve at the outlet.
And I don´t know if that what I´m experiencing is a absolutely "normal" physical princip, equilibrating the pressurized hydraulic fluid between forces to equilibrate them.
So, I hope that I have described the problem less or more understandable and I would greatly apreciate if somebody can give me any hints (or even if you all agree that what I´m observing ist "totally normal"). If you have questions or need more details of the internals of the valve body, don´t hesitate to ask me.
Best regards and thanks in advance for reading this long text.
Tomás
I´m writing from spain, my name is Tomás, and I found this excellent forum searching internet for help with the problem (if it really is one) of my backhoe. It´s a 1999 Fiat-Hitachi FB100 with about 10.000 working hours, and I think this is very similar to some New Holand and Case backhoe models.
This machine has a conventional hydraulic system with a tandem-gear pump, no load sensing, no servo-hydraulic, no fancy joysticks. The backhoe valve assembly is built up by 4 HUSCO-valve sections, in this order (from pressure inlet): Boom-swing-bucket-dipper, all of them equipped with relief valves, except the bucket and dipper rod-end sides. Between every two sections there is a spring-loaded check-valve. There is a inlet-end cover feeding pressure to the backhoe carriage clamp-mechanism. The outlet end cover incorporates a back pressure valve and regenerative check valve.
All hydraulic is working fine, and with speed varying with motor rpm. Steering, loader and stabilizer without any problem, and even the hoe while not combining cylinder movements with the boom cylinder. I try to explain: All three cylinders (boom, dipper and bucket) have a lot of power and work with more than enough speed. Also the combination of dipper and bucket cylinder is working fine and fast. But when I try do do a combined movement including the boom cylinder, I only can do this moving either the boom very slow (this means, not to move it´s control lever more than to half it´s way or even less) or, moving boom faster but of cost of dipper oder bucket cylinder speed. A combined movement of two or three of the sections can only be done very slowly, but this independent of motor rpm. If I rise rpm the problem still is the same, only at a little bit higher "total speed", but in my opinion very below for doing a serious, paid job in a given time.
I don´t remember if this was the same when I bought the machine 10 years ago, by this time I was a total backhoe-newbie and use the machine only for pleasure doing some work on my own property. I learned how to maintenance, repair and even improve this machine; I´m not afraid of doing difficult tasks when I know what I have to do.
All the three backhoe cylinders are in well condition, they hold their position even under load, so I think I can exclude internal cylinder leakages and I suppose that the "problem" also can not be produced by bad, worn or hanging vale spools, as every one of the sections work absolutely fine. I also think that the problem will not be caused by the relief valves, because of the good load-holding of every cylinder. And I can hear them well when they begin to work moving either cylinder to it´s end position (or "overloading" it). The only items I really don´t know if the can produce this problems are the check-valves between the sections, or the back pressure valve and regenerative check valve at the outlet.
And I don´t know if that what I´m experiencing is a absolutely "normal" physical princip, equilibrating the pressurized hydraulic fluid between forces to equilibrate them.
So, I hope that I have described the problem less or more understandable and I would greatly apreciate if somebody can give me any hints (or even if you all agree that what I´m observing ist "totally normal"). If you have questions or need more details of the internals of the valve body, don´t hesitate to ask me.
Best regards and thanks in advance for reading this long text.
Tomás