Lorry cab tilt hydraulics - how on earth do they work?

[Endacy]

I have just bought a cab tilt pump and ram off of ebay:



The yellow labelled pipe had a t-piece and a cut off hose, the seller said this went to another ram, I suspect it may have done that or gone to a hydraulic lock mechanism for the cab. I removed the t-piece and screwed the hose directly to the ram.

The pump has a selector for up / down. It does not work how I thought it did! Turned one way, it pumped up, turned the other it retracted for a few strokes and stopped. Removing the filler cap made a hiss, and you could retract it for a few more strokes, then it would only move if you put the filler cap back on, and so on...

The pump pumps fluid out of ONE port, or BOTH ports, this is correct from a diagram I found of this sort of pump. It's not one or the other, so that can't be a normal double acting ram...

I played by connecting the single outlet (when selected that way via a single pipe to one port on the ram, it went up. I connected it to the other port on the ram, it made a funny noise and fluid slowly ran out of the other port, it didn't move.

Now whichever way I connect the hoses the ram goes up! I must have ******ed it up completely now. So how does that damn ram work and what's wrong here, I must be missing something, the ram must have valves or something in it? I must have killed a seal or something by playing as well hence it just going up now?

Help!

 

[piman]

Hello Endacy,

is that a double ram?

My feeling is that the hydraulics lift the cab and the weight of the cab brings it down?

Alec

 

[Endacy]

Well it looks like one. But when disconnected and moved by hand fluid came out of the bottom port when pushed in, AND when pulled out!! The upper port has a mesh thing inside it. So it can't be a standard ram?

Also if it were just a normal two way ram when I connected the pump out to each port it would have gone out and in...hence my confusion! I might end up trying to dismantle the ram!

 

[CKJDJK]

It may be that the down setting opens another port with a restriction in it. The pumps first couple of strokes is enough to bring the cab back over centre so the the cabs weight will assist to bring it down. The restriction is controlled by opperating the pump handle to lower the cab in a controlled manner. descent stops if the pump action is stopped.
Hope this helps
Chris

 

[Uniqueusername]

LOL, funny ******s aint they ?
Try this;
http://www.powerpackerus.com/documents/cab_tilt_manual.pdf

 

[Endacy]

Well these clearly aren't ideal to use as anything except cab tilt hydraulics!!!

I found that powerpack website too just now, seems it has to all the way up to come back down? Odd.

Well thanks so far. Looks like this'll just sit around at the moment...

 

[Uniqueusername]

No, you can reverse the direction at any time as long as it isn't in "free fall" in which case you won't be able to pump fast enough to overcome it.
The rams are pretty much universal apart from the restrictors / parachute valves, it's the pump that's usually the oddball part.

 

[Endacy]

I'll have another play then and report back, i'll try it with weight on it, perhaps thats the issue, it needs a bit of a load? I'll jack the bed of my radial drill up and see what it does.

 

[jugs]

LOL, funny ******s aint they ?
Try this;
http://www.powerpackerus.com/documents/cab_tilt_manual.pdf

Clever bit of kit,
We must be able to use them for other things lifting gas bottles, lowering your cupper onto the bench ????

 

[Endacy]

Thank you for the replies, I was clearly thrown off by the apparently double acting ram - it's isn't really. I wonder if they use the 'retract' part of the ram to regulate the use of fluid and also to store it. Not sure. Anyway I disconnected the jack from the table on my radial drill, bolted the pump to it and propped the ram underneath, it works, slow and HARD WORK! I have put that down to the tiny pipes and ports the fluid goes through. It also went down when pumped, and near the bottom slowly freefall down.

So i'm an idiot when it comes to these then, it does seem to work after all.

 

[Uniqueusername]

Double acting, yes it is. Power in, power out.
The retract part of the ram does indeed store oil
They are quite slow and fairly hard work, whether loaded or not. They weren't intended for anything except maintenance work and it helps keep fat truckers fit.