Anyone know about hydraulics?

[wizer]

Hi all

I managed to wangle a Scissor Lift Trolley from work. It's had a hard life, the wheels are shot ad the hydraulic lift is a little on the feeble side.

When you pump the table up, it only just pumps at the very bottom of the action. So pumping the table up takes about 50 pumps. I'm told that whilst it was full of PC's (they really fill these things up) the valve cap blew off (hence the black tape):

You can see at the other end of the pipe there has also been a leak:

Does anyone know about this stuff? I guess I need to fix the leak and then refill it. Anyone know what I refill it with?

I'm thinking about using it as an outfeed table and for cutting sheet stock.

 

[Steve (Correze)]

Hydraulic, not pneumatic

Hydraulic is oil (fluid), pneumatic is air.

Probably low on oil, at least as a first guess, are there any parts missing under the black tape?

If you got it for nowt, any old oil would do the job, or you could look for hydraulic oil, any farm machinery supplier or farmers supply shop will have general purpose hydraulic oil.

If it doesn't make a mess and holds position/load for long enough, I wouldn't even bother fixing the leak, just put a drip tray under it.

 

[wizer]

ooops, I knew that. Dunno why I was thinking Pneumatic.

I need to get that black tape off and have a look and generally give the thing a clean up. I'd rather fix it up so it doesn't continue to deteriorate. I'll have a look for hydraulic oil. I assume I can just pour it in? I don't have to pump it in under some sort of pressure?

I need to have a look at the wheels. I'm thinking the easiest thing to do would be to take them off and replace with 4 locking castors on a wood frame.

 

[Steve Maskery]

Wizer
You'll probably have to pump the fluid in, not under pressure exactly, but by suction. I remember helping my dad to do this when we were kids.

He had a tall bottle with a bung and two tubes in the neck. One tube went right down to the bottom of the bottle, the other was short, just to let air in and out.

The bottle is filled with hydraulic fluid, the long tube is connected to the hydraulic valve and you pump away.

Each time you pump, air is forced out of the system and bubbles up through the bottle. When you release the lever fluid is sucked into the system to replace the partial vacuum thus formed. Continue this until no more bubbles appear. Close the valve.

Looks like it could be a helpful piece of kit.
S

 

[wizer]

seems to make sense Steve thanks, I'll have a play.

 

[RogerS]

Maybe this might help? Same principle, I think?

http://www.carbasics.co.uk/how_to_bleed_car_brakes.htm

 

[newt]

Halfords sell brake fluid, should be ok.

 

[Nigel]

One word of caution if you intend to use as an outfeed table is to make some sort of height locking mechanism as the hydraulics will creep and upset any levels you set,

Cheers Nigel

 

[Oryxdesign]

WiZeR Do not use brake fluid it is not the same as hydraulic oil.
Simon

 

[wizer]

Thanks guys, I'm not mechanically minded, so this should be fun. I noticed on Halfords website that they do hydraulic fluid, I shouldn't imagine it takes more than a litre.

Locking mechanism :-k Perhaps something as crude as a pin drilled through the scissor?

 

[Nigel]

Or even cruder a length of 4x2 cut to the right length as a prop :lol:

Cheers nigel

 

[maltrout512]

Wizer as mentioned do not use brake fluid. Hydraulic oil has to withstand great pressure, so using anything else is a big no no. From what you have said, it sounds like there is a lot of ware in the piston on the pump. A new set of seals will help, but I think the bore will have ware in it too, which is a little bit more of a problem. Thats why its being taken out of use. Where the tape is would have been a rubber bung, which is now not there. This is where you fill the oil in. Remember that the ram has to be in the closed position (empty of oil) before you fill/top up. If not you over fill and oil runs out of the taped up hole when you release the ram, ie down position.

 

[wizer]

Thanks Malt, so the table fully up when the oil is added.

I will tackle it tomorrow and take some more pics.

 

[maltrout512]

No. The piston which comes out of its housing should be in the housing {down position} when filling with oil. If it is in the up position then all the oil is in the ram, not in the reservoir. So if you then filled to the level and then let the ram down it would overflow big time. It's only a one way ram. Pump to put up, release valve to go down.

 

[RogerS]

I thought you said the 'up' position...

 

[maltrout512]

Nice one Roger. :lol: :lol: :lol:

 

[wizer]

That was quite possible Roger. I have made some progress with it. I gave it a general wash and brush up to get rid of the years of grime. After that I checked the all the tube fixings to find out if they are leaking. I couldn't move the nuts in either direction, so left them be for now. In my local motor factor I found some oil for trolley jacks which I thought would be ok for this. I removed the tape and just poured the oil in.

As you can see I made my own bung out of an Ash offcut. This wasn't the most ideal material as the oil wicked up through the Ash. I will try to find something else for this.

However, the lifting action has greatly improved. It now takes just 15 pumps to get to the top. For now I am happy. I'll keep an eye on it and watch for leaks. But if it stays like this then it's fine.

I'm going to design a top for it and work out how I'm going to fix the wheels. This should be a useful addition to the workshop.

Thanks to all who helped, if you're interested there are more pics here