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Pneumatically Actuated Hi/lo

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Just thinking ahead to when I have a chassis to attatch my engine & gearbox to, and of the fiddly job of fabricating the hi/lo and diff lock linkages for the transfer box.

Then the idea struck me of using little pneumatic actuators to twiddle the bits on the transfer box from, well, anywhere - no linkages required. I'm probably going to have some sort of air supply on the truck anyway, and I guess you can get actuators that don't need pressure to stay where they're put.

So - is this a monumentally stupid idea or could it actually work and save me a lot of farting around? And does anyone have any good links to stuff that'd do the job? :rolleyes:

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Hmm, assuming it would be used in the way it was designed, would dirt ingress into such fine tolerance parts cause you serious problems?

At least the linkage is 'KISS' principle.

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Hi FF, I don't know about your LR but my HI/LO changes while in motion are never completly "smooth" and the stick always needs a little bit of carefull coaxing as the speed and revs change as the gears synchronize - I reckon a "dumb" hydraulic/air piston might damage stuff unless you were at a complete standstill.

IMHO - human touch is better but then I am pretty traditional (proof being that I drive a Defender ;) ).

Adam

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Isn't this shuffling of knobs part of the Landrover experience? I thought that was part of the "pleasure" of driving them. :D

As Deano said, "KISS", as unless the actuators were 100% sealed (possible?) then one runs the risk of having an unreliable transmission. There would also need to be some facility to bypass/ reconnect linkages in the event of trouble while sitting in a lake, imho. ;)

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unless the actuators were 100% sealed (possible?) then one runs the risk of having an unreliable transmission

I'm assuming you can buy sealed units since several people (Paul W included) have used pneumatics on their trucks. I suppose hydraulics run from a pressure-dropped tap on the steering box would be another way of doing it, not sure if that's any more or less plausible though. Fabricating a linkage to extend the levers to sit in the right place (LT230 in a Series) you run the risk of ending up with something unreliable anyway :unsure:

changes while in motion are never completly "smooth" and the stick always needs a little bit of carefull coaxing

I tend to switch gears whilst stationary as I've never enjoyed the sound of grinding cogs :o

The changing-whilst-dead (no air supply) problem is not a biggie - if you disconnect the (push-fit) hose, or just have a control valve with a "neutral" position you should be able to twiddle the levers on the transfer box by hand if needed.

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I think you'd struggle with hi-lo and it does need some persuaion sometime.

If you could do hi - neutral - lo, you'd have a fighting chance.

Cylinders that are air tight are automatically water/grit tight :P

Would work quite well for difflock, but I'm not sure if you've got that

I need the shifters from an LT230 - so let me have your spares :D

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Yes it will work - but go for pneumatic rather than hydraulic.

When you open the valve, it just exerts a constant force on the thing it's moving. I would experiment with different pressures to find one which reliably engages without snapping anything off!

If this were my project - I would use closed loop hydraulic.

Simply connect two rams together (each port on one to the coresponding port on another). You will need a fill port and bleed nipple on each circuit (although the leakage is so small as it's not generally under pressure, once you fill it and bleed it, I doubt you'll need to touch it again).

The pressure is low - so you can use pneumatic fittings and rams.

This gives you a remote linkage - only connected by flexible lines.

I've done this a couple of times - including for the steering on a novel bicycle! If you get all the air out it provides a very positive and subtle linkage.

Si

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Well that's a flippin' cunning idea Si... will have to investigate that!

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i dont see any reason why its not possible . . . i would approach it the same way as described simonr.

the P38 is servo operated between Hi and Lo. You throw the lever over to the left and it does the rest. 3 seconds of pause, and then clunk, its slotted over.

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Yes it will work - but go for pneumatic rather than hydraulic.

When you open the valve, it just exerts a constant force on the thing it's moving. I would experiment with different pressures to find one which reliably engages without snapping anything off!

If this were my project - I would use closed loop hydraulic.

Simply connect two rams together (each port on one to the coresponding port on another). You will need a fill port and bleed nipple on each circuit (although the leakage is so small as it's not generally under pressure, once you fill it and bleed it, I doubt you'll need to touch it again).

The pressure is low - so you can use pneumatic fittings and rams.

This gives you a remote linkage - only connected by flexible lines.

I've done this a couple of times - including for the steering on a novel bicycle! If you get all the air out it provides a very positive and subtle linkage.

Si

With this hydraulic arrangement, you would cylinders with lip seal pistons. Some have piston ring type seals that naturally leak a small amount and these would get out of sync over time.

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I know it wont sort your hi/lo out chaps but have you considered using the Disco II diff lock mechanism? Is a remote cable operated affair designed to operate the diff lock on the LT230 box.

HTH

Jon

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With this hydraulic arrangement, you would cylinders with lip seal pistons. Some have piston ring type seals that naturally leak a small amount and these would get out of sync over time.

I suggested using pneumatic cylinders since the pressures are low. Use ATF or even diesel as hydraulic fluid and the pistons come fitted with particularly good lip seals to start with.

Anything designed for hydraulic is going to be a bit to heavy.

Lastly, even with piston rings, you will be pressurising either end of the cylinder the same number of times and the pressure is zero once it is in gear and you have taken your hand off the lever. Any leakage will cancel out.

Sewing machine or castor oil work pretty well too, as does brake fluid if you need something less viscose.

Si

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FFS.

Surely to God all you need is a couple of 'lines of code' to a MegaSuart ECU and "Job Done"

Coat going on right now with tin hat :lol:

Nige

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