More woes around hydraulics, thumb etc

[Storrsy]

Ok, so trying to fit the thumb grab to my 3 tonner. Nothing to do with welding this time, but my Tak only has on/off aux hydraulics so no proportional control. Basically plugged it into the machine to day and despite having no proportional control the thumb/ram actually extends in a beautifully controlled manner with no pump noise at all however when I try to retract the ram, (Close the thumb against dipper) it’s too fast and the pump is straining- not nice, Pump is either trying to push too much fluid, but I don’t understand why it’s so nice in one direction but not in the other. Any simple ideas for ways round this, ideally I’d get the joystick switched for proportional control but not even sure if this is possible.
Thanks for all the forthcoming solutions!

 

[craig]

I would think extending the ram is taking a larger volume of oil, where as retracting, is less the volume of the chrome rod.
Some kind of flow reducer/overflow valve fitted in the retracting side?

 

[GazCro]

Switch the pipes round for a start and see if it's the same. Make sure tap for single acting circuit is fully closed (I'm sure your tak will have one)

 

[Smiffy]

Have you tried flipping the hydraulic lines over ?? Just to check it's the if the symptoms are reversed or not
If they are it's as above if they arnt it might be to do with the size of the flow and return pipework if one side is larger to accommodate a breaker or if it has the single and double acting switch it might not be fully over

 

[Storrsy]

Switch the pipes round for a start and see if it's the same. Make sure tap for single acting circuit is fully closed (I'm sure your tak will have one)

Yes I’ve tried switching pipes around, and it’s in double acting mode- it’s deffo when the ram is extracting which is the issue. I could put a flow reducer in but the pump will still kick out the same flow so will be making that nasty straining sound still. A bit controversial but the offset boom is off a proportional pedal on the floor- wondered what would happen if I switched the pipes around with auxiliary! My gut tells me not to go fiddling with things like that even though I’m my mode it should work, but then I’d expect the offset ram to display the same problem so perhaps robbing Peter to pay Paul!

 

[Storrsy]

Or would adjusting the pressure relief valve on the valve block make a difference?

 

[Storrsy]

I would think extending the ram is taking a larger volume of oil, where as retracting, is less the volume of the chrome rod.
Some kind of flow reducer/overflow valve fitted in the retracting side?

Hmm overflow valve -id better get googling. I’ve tried flow restrictiors, they slow it down but obviously doesn’t stop the pump over straining.

 

[GazCro]

Hmm overflow valve -id better get googling. I’ve tried flow restrictiors, they slow it down but obviously doesn’t stop the pump over straining.

Your not gonna stop the the pump straining unless you knock revs off though. When you press those buttons its full flow. I have heard of people fitting change over valves to use boom slew as an extra aux line but it would have to be a last resort.

 

[Storrsy]

If I put a flow restrictor in- to get the speed right, but then adjusted the pressure relief on the valve block for that hose, so that it reliefs as the pressure though the flow restrictor builds- would that work?

 

[Storrsy]

If hose A is opening the ram, turning an auger, lifting post knocker hammer- I’d be happy to retard the pressure on hose B as generally that is reversing auger, returning thumb to its rest, so not actually actions that require much flow or pressure.

 

[GazCro]

If I put a flow restrictor in- to get the speed right, but then adjusted the pressure relief on the valve block for that hose, so that it reliefs as the pressure though the flow restrictor builds- would that work?

Relief valve on valve block will govern both lines. Also adjusting it will alter pressure not flow and you'll possibly end up with a thumb that wouldn't crush a coke can. In some ways you'd be better off converting joystick switches to a left hand foot pedal on the floor like smaller taks.

 

[doobin]

If hose A is opening the ram, turning an auger, lifting post knocker hammer- I’d be happy to retard the pressure on hose B as generally that is reversing auger, returning thumb to its rest, so not actually actions that require much flow or pressure.

Nope. Restricting the actual return will raise back pressure when using auger etc which is a no no. The flow reducer needs to be on the thumb hose itself.
You need a flow reducer that diverts excess pressure straight back to the other line. So the engine can put out the whole flow but only the amount you choose will go to the ram, the rest will just loop back.

It won’t be hard to do.

 

[V8Druid]

Flowfit Hydraulic 3 Port Adjustable Flow Control Valve c/w Relief Valve, 1/2" BS | eBay

Flowfit Hydraulic 3 Port Adjustable Flow Control Valve c/w Relief Valve, 1/2" BSP Ports.

www.ebay.co.uk

 

[Storrsy]

Flowfit Hydraulic 3 Port Adjustable Flow Control Valve c/w Relief Valve, 1/2" BS | eBay

Flowfit Hydraulic 3 Port Adjustable Flow Control Valve c/w Relief Valve, 1/2" BSP Ports.

www.ebay.co.uk

Ok, this looks good, it says the excess flow must be returned to tank. So assuming this is fitted to Hose B can I T the excess flow back into hose A where it would go back to tank?

 

[V8Druid]

Ok, this looks good, it says the excess flow must be returned to tank. So assuming this is fitted to Hose B can I T the excess flow back into hose A where it would go back to tank?

depends whether it goes through the valve block or not ... but you'll probably need a direct to tank line TBH ... you'd need to trace the line you're intending to tee into and you'd also need a check / one way valve in the line or when operated in the opposite direction you'd load the flow control valve in reverse - not good

 

[Storrsy]

depends whether it goes through the valve block or not ... but you'll probably need a direct to tank line TBH ... you'd need to trace the line you're intending to tee into and you'd also need a check / one way valve in the line or when operated in the opposite direction you'd load the flow control valve in reverse - not good

Oh golly, this is starting to get complicated for my little brain. Perhaps another job for the pros! Anyone know any good plant engineers in Devon!?

 

[craig]

Flowfit Hydraulic 3 Port Adjustable Flow Control Valve c/w Relief Valve, 1/2" BS | eBay

Flowfit Hydraulic 3 Port Adjustable Flow Control Valve c/w Relief Valve, 1/2" BSP Ports.

www.ebay.co.uk

That was the type of thing I was calling an overflow valve earlier on

 

[V8Druid]

Oh golly, this is starting to get complicated for my little brain. Perhaps another job for the pros! Anyone know any good plant engineers in Devon!?

Rory'd sort you out .... more than capable

 

[V8Druid]

That was the type of thing I was calling an overflow valve earlier on

handy valve ... bleeds off the excess you don't want

 

[Storrsy]

depends whether it goes through the valve block or not ... but you'll probably need a direct to tank line TBH ... you'd need to trace the line you're intending to tee into and you'd also need a check / one way valve in the line or when operated in the opposite direction you'd load the flow control valve in reverse - not good

On my Tak the cab tilts up giving access underneath to all the valve block next to the hydraulic tank etc, is there any reason why the flow restrictor valve could be be fitted where the hose comes out of the valve block and there for just a short little hose for the excess to go straight into the tank?
Rather than it being plumbed all the way out along the arm, like to keep the arm clutter free if poss...