JCB 3c mk2 adding third service to back hoe, Problem

[Tom.S]

Hi All.

All help gratefully received.

I have a JCB 3c mk 2 on a J plate, 1972 I think. I am trying to pipe the back hoe for a grab, cone log splitter etc.

I have got hold of the foot control valve out of a 3cx Extradig D/E plate, white cab, from a breakers and fitted in place. Teed off the 1" flow and return pipes feeding the rear spool block, but nothing!

I have tried several ways of piping the foot valve, before the rear spool block, after and also in the flow only.

Today I have piped the foot valve out to another tractor and it worked fine, so all the components work just not together. What am I doing wrong??????

Does anyone have any idea what I'm doing wrong please or can it not be done.

Looking forward to your thoughts

Tom

[essexpete]

Some of those era machine were fitted with a tandam pump to get enough oil flow to run the 3rd service whilst the standard controls are operated. That is an aside really an would not stop the 3rd service working. I never had one apart on our JCB so where have you taken the flow to the extra spool valve? When the main spool block is not in use there will be a flow of oil through it supply and return. If you just T into the flow and return oil will flow via the easiest route. Have you tried dead ending one of the main services whilst operating the third? Putting it another way the new spool needs to be in series rather than parallel. Do you know if the new spool is fitted with it's own relief valve?

[Tom.S]

Thanks essexpete for your input.
I've taken the flow from the return side of the main spool block and returned it where the pipe joins the chassis (tank) keeping it in series. When I put it in before the main block, the back actor stopped working unless your foot valve was open. I do think the foot control has its own relief valve, it's a Parker hydraulic block self contained unit.

Its a standard machine with one pump at the front, the oil leaves there and goes to the front load block. Out the loader block to the back actor then out the block to the tank. Thought it would be easy to T into adding another block after the back actor and before the tank, but no.

Do you think / would it be possible that new block is being supplied oil from both flow and return, with the supply lines being bigger. does it need a non return fitting placing on return side of the new valve ?

[dixie-normous]

Hi Tom, as Essexpete says they used a dual pump with the 3rd service run direct from the second pump. Have you tried disconnecting the feed and return from the rear spool block and running it direct to the pedal to see if it works? (Just out of curiosity), it may be the flow rate through the rear spool that is causing the problem. If it works that way you could put a diverter valve before the rear spool to send oil to the pedal but that would be a pain in the hoop as you won't be able to use the back actor and the 3rd sevice at the same time. The only other option would be to get hold of a dual pump and run a second direct feed to the 3rd service
John

[Tom.S]

Hi John, thanks for your ideas, Ill give them a got over the next few days and report back.

[Tom.S]

Hi John, I plumbed the foot pedal direct into the flow and return - disconnecting the main block and all works well. So I plumbed the foot pedal in after the main block with out T-ing off ( removing the 1" return pipe) and both back actor and third service work. but the return from the main block (back actor) is all flowing through the foot pedal valve and 1/2|" pipes not 1". things get warm quickly!!!! Thinking of adding a small relief pipe T-ed around the foot valve just to ease the flow.

[dixie-normous]

That may work but you may find you lack pressure to the foot pedal. Another alternative is an electronic diverter valve after the main block operated by a push switch under your left foot, that way the 3rd service only operates when you press the switch down and meaning you don't have to take your hands off the controls. As long as the valve has a high enough flow rate to let the oil return through it when switched off it should be ok, assuming you don't need to use the 3rd service for long periods