3930 hydraulic flow questions

hbarski · Feb 15, 2006

I have a 3930 with a hydraulic heat problem. The tractor has front and rear remotes that power a FEL and the till-n-trim cylinders on the 3-point. I am trying to install a grapple to the FEL and I am beginning to think I may have "bought" a hydraulic problem. Tractor is a 93 model that I bought back in June of 05.

See the attachment for a schematic.

My question is, shouldn't this be a series circuit? I have two thin adapter plates installed for the hydraulic tapoff and return.

Should I reroute the hydraulics to a series circuit "before" I install the grapple control valve?

If I install another valve to control the grapple, will I be inducing more heat, if I tap into the power beyond on the FEL circuit?

I could use some expert 3930 hydraulic advice.

Soundguy · Feb 16, 2006

Looking like an OC ciruit ( though.. with NH.. could be some CC stuff in there! ).

In any case.. I don't see why you couldn't use the PB port on the spool for the loader.

Ultimately, you have finite flow, and will be limited to how many circuits you can operate at once, and the speed of those circuits.. however.. no reason you can't add another branch circuit, where it is provided for.. etc.. like the PB port., or even a tap for another set of spools where the loader spool is attached.

As for heat? I think that bay adding circuits and hoses, you will not be contribuiting to heat specifically.. heat will be a byproduct of the work performed by the pump, and pressure/cyl action. IMHO.. the more hoses you have, the more cooling surfaces you are adding.. For instance.. adding another power and return, or lines to a DA cyl, are just another place for that oil to disipate heat to the open air before returning to the sump.

If you think your oil temp is getting too high, consider putting a oil cooler in the low pressure side, assuming your tractor does not already have one. Many of the smaller NH tractors have them up near the radiator,... and my 7610s does as well.

If you have a hyd filter inthe return side.. you can get a heat sink for it.. several companies sell an aluminum clamp on het sink fin set for spin on filters... just dab some heat sink compound and attach with clamp... gives you a marginal increase in cooling... could also add this to your tractors built in spin on filters.. etc..

Soundguy

hbarski · Feb 16, 2006

I am beginning to have concerns over how the unit is plumbed. I have talked to a New Holland mechanic who said that all systems should be setup in a series flow circuit. And based upon a few other folks' comments, I believe he may be right.

By looking at the attached image, and comparing it to the first image, my system currently looks like two independent circuits. And on top of that, the low pressure return fluid (cylinder exhaust) is having to overcome bypass return pressure and is being returned into the tapoff plates. (NH mechanic said he had never seen two plates installed) Power byond is plugged off currently on both the front a rear hydraulics valves.

Soundguy · Feb 16, 2006

Hmm.. maybee I'm misunderstanding here. Are these not the factory 2 port remotes that you are using? For instance.. i have 2 spools on my 7610s.. each spool has a 2 port adapter on it.. etc.. My 5000 has a single spool, and thus only 2 ports.

On the 7610s.. I can run 2 seperate, independent circuits.

That's what your first schematic looked like.. 2 circuits.. 1 for loader.. 1 for T&T.. right?

soundguy

Soundguy · Feb 16, 2006

In that second schematic, it shows pressure from the pump delivered to a tapping block.. whish has a pressure and return port.. presure would be fed to a spool.. also has a connection to return, and has PB.. that feeds the 3pt lift line.

High pressure relief is tied right after the pump.... I don't see how you would be forcing pressure back down the pump output line in order to be making the relief open, to dump return oil.. In fact.. from looking at it.. if you have OC valves.. looks ok.. .. now if you had a CS valve.. i can see the relief opening, assuming PB wasn't connected while valve was closed....

Weird setup since you say PB ports are plugged... Does your 3pt lift work?

I was also assuming that you were using oem spools.. still not sure if that is the case ??

As far as 'series'.. thiking about the hyd flow.. pump.. spool, cylinder, and either return or back to spool then return, depending on sa or da cyls.. then that is series.. however.. usually you can add parallel sets of series circuits.. thus a tractor having more than one set of spools tapped off thier hyds section... AFAIK all circuits do not have to be series with each other.. etc... in other words.. you could use top spool even if bottom spool was unused. If all circuits had to be series with each other.. it would seem you would have to use jumper hoses in all spool sets present, ( or have OC valves installed, and hoses connected ) ), or it would preclude your use of 3pt... My spools are not used on my 5000 or 7610s.. very often, and my 3pt works fine.. etc..

Soundguy

hbarski · Feb 16, 2006

<font color="blue"> Are these not the factory 2 port remotes that you are using? </font>

The top-n-tilt is an aftermarket add on, but the FEL is a 7209 Ford loader. Both units were put on by previous owners. The 2 hyd tap-off block looks aftermarket, and are very thin. Nothing like the thick New Holland block. According to the second diagram, the power beyond port should have be routed into the tapp-off blocks return port or another valve in series, and system exhaust fluid should have been routed into the sump return. Mine is no where like that.

hbarski · Feb 16, 2006

<font color="blue"> I don't see how you would be forcing pressure back down the pump output line in order to be making the relief open, to dump return oil. </font>

My limited intelligence says that with the power beyond plugged off on the FEL spool valve, high pressure bypass and system exhaust (cylinder low pressure) are being returned to the tap-off return port. It makes me think the cylinder exhaust fluid has to overcome the bypass pressure that is being forced out the spools return port istead of the power beyond port.

MadReferee · Feb 16, 2006

That last diagram looks just about like the Kubota aux hydraulic setup. Whatever is connected to the aux plate top should also have power beyond since the plate top connections break the series circuit between the loader and the 3pt control. If nothing is connected to the plate then you either have a jumper on the plate top connections or a different plate top cover with an internal connection (Kubota does it this way).

Nothing magical or unusual here other than the way the prior owners connected to the plate top.

Soundguy · Feb 16, 2006

I agree. If the 3pt is working.. there must be an internal port connecting it.. otherwise looks fine. Circuit does not look like it could be causing the problem he thinks about return fluid being forced back down pump output line, and thru relief... no evidence to support that premis.. especially since it is a single feed line, and fluid would have to be moving thru the spool to actuate that cyl.. thus no room for expelled fluid back into that circuit.. etc, unless noting moved, as ram was stuck or bottomed, and then the relief would open.. etc..

Soundguy

hbarski · Feb 17, 2006

So in both of your opinions, this is a non-issue.

When I add a directional control valve to control the soon to be installed grapple, I can just tap into the power beyond at the FEL circuit and route return fluid to the sump, or do I have to tie back into the tap-off return plate?