Bobcat Jerky Controls

[Blondie70]

Howdy
When I increase engine revs above idle...to about 1250, the controls are super sensitive. I don't want to work it at idle.
Is there any way to cut back on the sensitive ? Boom, Swing, Stick and Bucket.
The tracks and blade are ok
If I could pinch back on something to slow them down a bit but keep the power, it sure would be nice ! This is a 331 Bobcat.
Thanks, Pete

 

[cuttin edge]

Our 45 is quite jerkey unless you run it full throttle. I'm unaware of anyway of changing it from the cab. The thumb pressure can be changed from the seat. If the right person sees this, you might find out.

 

[The Learner]

Is it possible that the pilot circuit accumulator has failed?
You can get a feedback like an odd non engine vibration through the joystick and sometimes through the cabin floor

If you hop on the machine fire it up and rev up to 1500-1800 revs
Flick one joystick
(Pull boom up till the boom just moves then let go)
Does it continue to bounce up down up down
Or does it come to a stop after 3-4 motions
(Partial failure of accumulator)

Another why to test
Start machine
Lift boom 1-2 ft from ground
Turn off machine
Turn key to on position but don’t start
Lift and lower the left console
Try to lower the boom
If it doesn’t lower at all
(complete failure of accumulator)

That would be my first test as a former bobcat dealer mechanic

Cheers

 

[Blondie70]

Thanks Learner. I will do these tests and post here. I have the "deluxe" panel model with no key. After shutdown, I notice the gauges still have power and I could restart if needed. During this period, would it be considered same as key on for your test above...if so, I know nothing moves then because I have tried to lower the boom a bit to bleed off system but it does not move............
Where is the accumulator ...is it the small bottle looking tank...bout the size of a 2 liter drink ???
Thanks, Pete

 

[willie59]

Don't know the series or s/n of you 331 so this valve may be different, but the accumulator is mounted to the solenoid valve manifold, item 1

 

[The Learner]

On deluxe panel I believe you press stop. Run. Push your code and press enter. But not start. To have key on.

It’s not a 2ltr bottle should be about the size of your clenched fist like the picture supplied by willie

Another thing I thought of after I posted
Are your joysticks over adjusted?
Under the flexible rubber boots
You have 4 plungers
There should be roughly .5-1mm or 1/32” between each plunger and the contact ring
If this is done up to 0 or less than zero your machine is always trying to move even before you lean on a joystick

 

[Blondie70]

Thanks for the great info, Learner. I see the accumulator. I will do the test you mentioned. I will check the joystick adjustment also.
I will post back here the results.
Thanks again......Pete

 

[Blondie70]

I did the tests Learner suggested today. Reving to about 1600 RPM and raising the boom easy and just letting go of joystick caused no jerkiness...boom just stopped and slightly bounced couple times.
Now the key on and trying to set bucket down from 2' up did nothing. The boom did not lower. I wish I had a key, but I did what Learner said and the boom did not lower. I also tried before starting (when I had starter permissive) but boon no go down. This so called deluxe panel is not the best thing, I think. Much rather have a key as I could probably fix it if something went wrong...this panel is more complicated.
Anyway, these tests show good accumulator on one and bad accumulator on the other ??? Learner, can you make anything of it?
Thanks, Pete

 

[The Learner]

Is a hard thing to diagnose
The bouncy control alerts partial failure in my experience but doesn’t not tell you anything of total failure

Total failure is having no ability to lower the boom to the ground after an engine failure

The accumulator serve 2 purposes
Remove shock and vibration from the pilot circuit during operation
And allow some pilot pressure to be reserved for after the engine has lost power

The complicated part is I can’t remember if that is “key on” proceedure

Maybe someone else can chime in

 

[Blondie70]

Thanks. After shutdown, I can restart for about 30 seconds as the panel is live. Then the panel shuts down. Cannot start. Must re enter code to get it live again to start...seems like that would surely be "key on".
At any rate....is there any way to test the accumulator if I remove it ? Some shop I could send it to for testing and or a rebuild ?
Thanks, Pete

 

[The Learner]

If you take it out
your major hydraulic shops
don’t know what they are named over there
(Hose, fittings, pump, valve suppliers)
Should have testing equipment for accumulators

 

[Blondie70]

Thanks. I'm gonna get on it and start checking around.
Pete

 

[Blondie70]

Willie...my accumulator looks exactly like the one in the pic you posted....the manifold is different (no wires).I will call an accumulator specialist tomorrow and talk to him.
Pete

 

[Blondie70]

Learner............please tell me the operating pressure on the pilot accumulator ???? Talking to a guy in TX about it. His CO. repairs them.
Thanks, Pete

 

[willie59]

I don't know what series your 331 is, but on the G series 331 the pilot system is 435 psi.

 

[Blondie70]

Thank you Willie !
Pete

 

[John C.]

Just a quick tip. The accumulator stores oil so if the pre-charge is at 435 PSI and the pilot system runs at 435 PSI then no oil will go into the accumulator. In general you only want pre-charge pressure to be no more than it takes to move a spool on a pilot system. So if it only takes 50 PSI to move a spool then that's all the pre-charge pressure that you want. I generally never put more than half operating pressure for a pre-charge unless the factory specifies it.
Good Luck

 

[Blondie70]

Thanks John. Makes sense. I am going to pull the thing off as the guy at Accumulators Inc, in TX needs to know the thread size it has for attachment. I am assuming the thing cannot just be recharged with nitrogen as the bladder must be burst. They have small ones there, but I bet they are $$$$$$$$$$$$$$ if so, I will just live with jerky as I spent too much money for this machine !
He needed to know the operating pressure on it and the thread size and he will send me dimensions of the small ones he has to see if one will fit.
Hope to find something out on it by next week.
Will post here. Thanks, Pete