Hydraulic cylinder question

[mickeyf]

I don't have much practical hands on experience with hydraulics. I am fixing up an elderly and somewhat abused horizontal bandsaw. It has a hydraulic cylinder that holds the frame up until a valve is opened which then allows the frame to come down against the counter-action of a spring.

I can lift the frame to extend the cylinder its full distance (about 4 inches) with the valve closed but when I allow the frame's weight to push on it, it retracts perhaps an inch before it starts holding. At this point it holds as expected until I open the valve and then retracts the rest of the way, as expected . Since it is close to the pivot point of the frame, this lost inch translates to a much greater loss of height further away.

I am assuming that this first inch of travel is because it needs to be purged, or needs more fluid, or both. I'm not sure how to fix this, partly because the fittings have been brazed in place by a previous owner - the only access to it is to remove the valve, or possibly I could unscrew the end cap, but I have not tried that.

Any advice on 1) am I correct that the operation of this thing would be improved by purging/topping up, and 2) how do I go about this given the limited access?

Thanks in advance.

[oxford]

Does the nut at the valve come off or is that brazed on as well?

[mickeyf]

Yes, the nut comes off. I have checked that thinking it was a needle valve, but it is more of a ball end than needle, so control is not "fine".

[JoeLee]

It sounds like you may have air in the cylinder. The end cap looks like it unscrews. I would take it apart.
You you can buy hydraulic cylinder tubing and new fittings. Replace whatever seals or o-rings are on the inside.
There are probably a couple check balls in there too.
That wouldn't happen to be off a Kalamazoo saw with it?

JL....

[J Tiers]

Almost certainly there is less fluid than it should have. The unrestricted travel is before the piston hits the fluid. Probably there is always a little such travel, but maybe not. The fluid probably goes thru a one-way valve when you lift the saw, so you probably feel it release on the way up as well.

My Atlas saw has the same system, but no brazing and no external piping. I had that same problem, which went away when I added fluid. It took less than I thought.

[tom_d]

That banged up tube on the side drains the oil from the valve as gravity retracts the cylinder and sends the oil to the top side of the piston. That top area acts as a reservoir. Open the valve and pull the rod out and oil is forced down that tube from the top side of the piston into the lower side of the piston. Close the valve and the oil stays there, holding the piston.
I would try extending the rod with the valve positioned as the high point. Open the valve and remove that nut. Hopefully it's not brazed in place. Remove the valve, then pour oil into the opening until full. Reassemble and try the cylinder again. You should, at this point, have the lower chamber full of oil, not air, and it should work properly. If for some reason there is a way to overfill the lower chamber then the cylinder will not retract completely. If so then just crack the valve nut and let oil leak out until the cylinder can completely retract. There is hydraulic jack oil available at most large 'box' stores, and most auto parts places. If none available then simple, straight 30 weight non-detergent engine oil should be adequate.

[Noitoen]

There must always air inside and it only functions properly in the vertical position. The volume is different on top and bottom of the cylinder because of the rod and if you pull it up too much, air will go to the bottom thus the springiness feel

[I make chips]

It certainly appear to have been repaired several times. All that brazing on it has likely cooked the internal o rings to death. Yes it relies on oil transfer from bottom to top for it's movement. Your assembly relies upon laying it down, tipping it etc., to bleed most of the air out of it before the needle valve has it's needle and nut screwed on. The tricky part is how much air volume vs oil is required. If yours is just worn out and you can't rebuild it or find a new one, you might have to get creative.

Consider this outfit although I have no idea as to shipping to you. It's usually pretty cheap. https://www.surpluscenter.com/Hydraulics/

[Doozer]

One idea would be to buy a new assembly from Grizzly or another supplier
that sells band saws. They are all about the same and yours is beat dead.
Spend some money and get on with life. Stop spray painting a turd.

-D

Band Saw Lifting Hydraulic Cylinder Made In China - Buy Hydraulic Cylinder,Hydraulic Cylinder,Hydraulic Cylinder Product on Alibaba.com

[JoeLee]

I think you would be better off finding a replacement that will fit, even if you have to do a little machining / modification to make it fit. Several make saws use that type cylinder. That one doesn't look like it's worth savaging. Who ever put all that brass around that fitting was a true cob artist. The heat may have warped the cylinder out of round and the piston will never seal properly causing fluid bypass and or air getting where it doesn't belong. There are some listed on ebay too.

https://duckduckgo.com/?q=horizontal+cut+off+saw+hydraulic+cylinder&t=ffnt&atb=v225-1&iar=images&iax=images&ia=images

JL..........

[I make chips]

^ Aww c'mon Dooz, you mean a Krylon overhaul won't work?

Oh nice! Looks like Joe Lee has the answer.

[Doozer]

^ Aww c'mon Dooz, you mean a Krylon overhaul won't work?

Oh nice! Looks like Joe Lee has the answer.

Keep putting more paint on it, and let me know when it starts working.
I am waiting....

-Doozer

(might take more than one can. May have to go to the store and buy more). -D

[cijuanni]

For the love of all that is holy, don't put anymore paint on it without 1st putting on more braze!

[JoeLee]

There must always air inside and it only functions properly in the vertical position. The volume is different on top and bottom of the cylinder because of the rod and if you pull it up too much, air will go to the bottom thus the springiness feel

The cylinder isn't always vertical. It has to function between vertical and pretty close to horizontal. And It has to be oriented in the proper position in relation to the tube / fittings to work properly.
The volume of fluid between top and bottom of the piston changes as it moves. In thought, the piston should actually be locked between fluid top and bottom. It's like a closed circuit.
You shouldn't have any air under the piston. That would cause sponginess. Also should be a way to bleed it.

Last option would be to replace the cylinder with a heavy spring and tension adjustment like the smaller horizontal saws have.

JL............

[mickeyf]

Thanks for all the responses.

Yes, it is off a Kalmazoo. (8x24 it seems)
The cylinder DOES work, I just thought it ought to have a little more travel than it does than with the softness at maximum extension.
If I'm understanding Noitoen correctly, it may already be working as well as I should expect it to.
Being "thrifty by nature" (ok, tightwad, cheapskate, your choice of euphemism) I will probably first try the procedure suggested by tom_d, which is kinda what I was after. "Nothing to lose."
I do have some jack oil from when I recently topped up my engine hoist which had set for a long time and showed similar symptoms. But it had a labeled fill plug, not welded shut connections.

As I said, it *does* work, I just won't be able to get the maximum capacity out of the saw without it holding the frame a bit higher. I thought I'd finish re-assembling the saw and see how well the rest of it behaved before doing anything as drastic as replacing the cylinder. It appears that the cylinder is strictly to hold the frame up while loading it, and downward feed pressure adjustment is handled by the counter balance spring.

I will be sure to braze it up real good before putting more paint on it! 🤣

On a side note, this is a very old saw, and I didn't expect Kalamazoo to have a particular part I inquired about. However, it would have been nice of them to at least say "sorry, we can't help you." rather than ghosting me. When I had a question about a no-longer-current Amflo mister, they actually responded and tried to help me. (No, I never did get the mister working.)