lift cylinder mechanical puzzle

Time to tap the PM braintrust again. After replacing a blown hose, and a couple that were about to go, in my vintage forklift I decided I'd have a crack at putting new seals in the lift cylinder before cleaning up.

It's a displacement cylinder so I'm thinking I should be able to unscrew the gland nut without pulling the cylinder from the mast (and incredibly two of the gland nut spanner holes aren't buggered up!).

The roller chain yoke sitting on top of the ram has two setscrews. That yoke is mostly hollow with only about a 3/4" thick bore sitting on a shoulder on the top of the ram. A guide tube (hanging from copper wire in photo) slides inside of the yoke and ram:



When I separated the cylinder from the yoke I found that the guide tube won't lift out of the yoke/ram. I also found that the two setscrews in the yoke were a good 1/2" shy of actually touching the ram. The threaded setscrew holes go all the way through the yoke and halfway into the turned down hollow ram. The guide tube rides in a brass guide inside the ram; doesn't look threaded and there are no spanner holes or slots. Everything of course has been thoroughly massaged with hammers in years past.



With the two setscrews out I figured the yoke would just be sitting on the ram shoulder, but it doesn't want to move even with encouragement from a large brass hammer. Trying to move it only moves the entire ram.

Any suggestions? My next idea is to fabricate some spacers and use a porta-power to press the yoke off the ram, but that had better uncover some means of freeing the guide tube. Since I can afford to let this sit for a few days I thought I'd try for a sanity check before escalating the violence.

It could be threaded on but do the set screws go all the way through? There might be a pin still in it. set screws could be just to hold it

Also that top piece above the (yoke?)could be a threaded in witha shoulder to lock it in place

idacal said:

It could be threaded on but do the set screws go all the way through? There might be a pin still in it. set screws could be just to hold it

Click to expand...

idacal said:

Also that top piece above the (yoke?)could be a threaded in witha shoulder to lock it in place

Click to expand...

Good thoughts; thanks for the input.

I carefully cleaned out one of the setscrew holes; 1.543 deep where the yoke casting is 1.547 thick. It looks like chewed up brass at the bottom, so some original setscrew evidently grabbed the brass guide ring (the one I removed didn't, way too short). Similar on the backside; 1.26 hole for 1.31 thick. I'll clean that out too but there can't be much in the way of a pin there.

It would make sense that the (original) setscrews held the yoke on the ram(rod) through holes in the rod end and grabbed the outside of the brass guide ring, which in turn captures the guide tube. But if so it's on really tight.

If the yoke is screwed on how do I unscrew it? I can rotate the entire rod plus yoke assembly with my hands when I twist the yoke.

I doubt the guide rod has any threads; it feels like a sudden hard stop when I lift it up, and no catching or thread engagement when I twist it while lifted up.

My rockwell radial arm saw had brass plugs under setscrews to keep the ram tight but still able to slide vertically. I was able to tip it sideways and get them to slide out with some help from gravity.
Any way to apply air pressure or vacuum to help them come out? shoot some penetrating oil on them before trying.
If you try to tap them for a puller they will probably just spin in the bore. Maybe super clean and superglue on a pull rod? Line the bore with a straw first so you do not glue them in place.
Bill D

Bill D said:

My rockwell radial arm saw had brass plugs under setscrews to keep the ram tight but still able to slide vertically. I was able to tip it sideways and get them to slide out with some help from gravity.
Any way to apply air pressure or vacuum to help them come out? shoot some penetrating oil on them before trying.

Click to expand...

I've soaked everything with penetrating oil for a couple of days now. I've also now cleaned out the rear setscrew hole. Interestingly, the bottom isn't buggered like the front one; it has a clean bottomed bore that ends halfway into the turned down rod diameter (i.e. the setscrew dog fits a dimple in the rod). I can see setscrew dog marks on that bottom which looks like steel, not brass. I measured the front setscrew hole as only a few thou shy of going all the way through the rod and to the inner brass guide bushing. But, that setscrew and hole have been badly abused.

In either case no way to apply pressure to the backside, as long as the guide tube is still there.

Using a long pick I tried wiggling or moving the proposed plugs; no motion at all.

If you try to tap them for a puller they will probably just spin in the bore. Maybe super clean and superglue on a pull rod? Line the bore with a straw first so you do not glue them in place.
Bill D

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Any such plugs couldn't be thicker than about .20" or so, so not much meat to tap. There is no wiggle or motion down there so I doubt glue would grab well enough even if I could get the hole clean enough (these are 3/8" holes about 4D deep).

In desperation I could drill those holes deeper, all the way through both the outer rod and the inner brass guide bushing. I presumably wouldn't have to worry about getting metal debris in the hydraulics as it would fall inside the hollow rod interior.

It is possible, given the mangled front setscrew hole, that someone has already tried this.

Here's another idea, possibly just as desperate:



My working hypothesis at this point is that the inner brass bushing (that the guide rod rides in) was held in place by the front setscrew. The yoke is held on by both setscrews (one bearing on the rod diameter, one passing through).

But if the brass bushing is retained by other means, such as (very short) setscrews threaded into the rod diameter, I'll break something. If only the bushing is ruined it would be the easiest part to replace, assuming I could drag it out past any hidden retention.

Incidentally, the yoke has clearly been hammered hard on the bottom lip by previous owner(s). It could be I'm supposed to drive the yoke off first and then removal of the guide tube will be easy/obvious. I'm not man enough to hammer it off though; I'll need to press it off with some sort of split spacer around the guide tube.

how does the big steel spacer ring that you have held up by wire come off? I'm guessing your threaded between the non cromed rod and the yoke how to get it to break? I dont know I start with big pipe wrenches somtimes it works sometimes it doesn't those set screws dont seem big enough to be all the holds that together but it is all gravity also though.

idacal said:

how does the big steel spacer ring that you have held up by wire come off? I'm guessing your threaded between the non cromed rod and the yoke how to get it to break? I dont know I start with big pipe wrenches somtimes it works sometimes it doesn't those set screws dont seem big enough to be all the holds that together but it is all gravity also though.

Click to expand...

The "big steel spacer ring" is what I'm calling the "guide tube". I wish I knew how it comes off. It slides up and down and rotates freely but hits a hard stop when I try to pull it straight up. A circlip I'll bet, hitting the bottom of the brass guide bushing. So the real question is what's holding that bushing in. If it's just friction at this point I should be able to press it out with that porta-power ram. If not I'll break something.

If the yoke is threaded onto the rod I don't know how to hold the rod. Only the chromed part of the rod is accessible, so I can't use a pipe wrench (that cylinder leaks enough as it is). I'll try a strap wrench.

I think the yoke doesn't need much retention; the only force it sees is the load pulling it down onto the rod shoulder via the chain rollers. It would stay put even without the setscrews (and in fact the setscrews I removed were too short to retain anything).

More info:

I tried pressing the guide rod and brass bushing out:



though I was afraid to pump the ram up all the way. No joy.

One theory is that the yoke is threaded on the rod end. I tried cleaning off the chromed part of the rod and grabbing it with a strap wrench, no joy.

Then I tried whacking the ends of one of the the chain roller bosses with a brass hammer. I see I wasn't the first person to try that. Again no joy, though again I was afraid to whale away at max volume.

Then I tried the gland nut; it turns freely. Whew.

So another option is to pull the entire rod and hope there is some way to hold the rod securely at the bottom end, to try turning off the yoke. A lot more work as I'll have to remove the fork carriage.

You are correct in using a hammer to remove the crosshead. It is held by a close fit and rust.

You should remove the entire cylinder, as you will need to disassemble it further than thought. The guide rod is threaded into the bottom of the cylinder group.

I did a full write up on this type of cylinder a couple years ago for Zanrad. Clark CarLoader CL-4024 Mast Cylinder Problem

It is possible to reseal with out the factory tools for preloading the seals but takes some time to not cut chevrons.

Good luck,
Mike

Mikethemechanic said:

You are correct in using a hammer to remove the crosshead. It is held by a close fit and rust.

Click to expand...

With that encouragement I tried hammering upwards on the yoke (crosshead) some more, and it does seems to be moving!

It will need a lot more hammering to come all the way off.

You should remove the entire cylinder, as you will need to disassemble it further than thought. The guide rod is threaded into the bottom of the cylinder group.

Click to expand...

This I am having trouble visualizing. The guide rod rotates and moves up and down freely (loosely, even) until hitting a hard stop that keeps it from being pulled all the way up out of the brass guide bushing. Where would the threads be if they are on the guide rod?

I did a full write up on this type of cylinder a couple years ago for Zanrad. Clark CarLoader CL-4024 Mast Cylinder Problem

It is possible to reseal with out the factory tools for preloading the seals but takes some time to not cut chevrons.

Good luck,
Mike

Click to expand...

Hmmm ... is that not a standard single acting cylinder? The rod diameter looks a lot smaller than the cylinder diameter and I think I see a drain line in photo five. You also mention a nut that comes loose stopping the cylinder from retracting (nut holding the piston I assume); nothing mechanical is going to stop a displacement cylinder from retracting.

My cylinder is, I'm pretty sure, a displacement cylinder.

The yoke is off! Mikethemechanic was right, sometimes violence is the answer:



There are several dozen setscrew dog marks, this yoke has been off before (it's a 35 year old forklift).

But, I can't remove the yoke entirely because of the guide tube that passes through it. The top part of that guide tube, which is held in the mast crossbar with a big circlip, is one solid weldment. The guide tube slides up and down, and freely rotates, in a brass guide bushing set into the top of the rod. That rod does not appear to be internally threaded, and there is no visible snap ring or snap ring groove. The top of the guide bushing is pretty mangled but it looks like brass (the color doesn't come out well in the photo):



I can see no setscrews or pins in the now exposed turned-down rod end.

So how does that guide tube come out? Even if I pulled the entire rod I'd have the same problem; the cylinder is some 6' tall and I can tell the guide rod must be much shorter from its weight (light) and the degree it tilts in the bushing (quite a bit).

Surely the lift truck gods won't let me get this far without some solution.

Options I can think of:

1) Try pressing the guide tube and brass guide bushing out, per my earlier photo of the porta-power ram. Now that I know there are no visible setscrews or pins I can escalate the violence. It doesn't feel right though that the only brass guide bushing retention is a press fit.

2) Cut off the top of the guide tube so I can R&R the yoke and gland nut, then weld it back on afterwards. To keep the tube part from falling down inside the rod I could drill two holes transversely through the tube and insert a 3.370" long pin (the rod is 3.375" OD).

3) Cut a notch into the top rim of the turned-down rod end, into the brass guide bushing, to verify for sure that there are no threads or snap rings.

4) Pull the rod entirely? I don't see how that would help as I don't care about the wear guides at the bottom of the rod. But perhaps I could run the gland nut all the way down the rod and off the bottom end? This building only has a 12' ceiling and so I can't just yank the rod straight up, so a lot of extra work.

Success! I'm annotating this thread for posterity (I know I've found the PM back catalog to be very helpful).

Violence once again turned out to be the answer. I used a porta-power ram with right angle flanges (see photo in post #6) to force the guide tube and brass bushing out of the rod top. It was very tight. Once that was out the rest was easy:



The rod seals turned out to be chevron style vee packing (top, bottom, five pressure rings) that I was able to source through the nearest full service hydraulics shop I know of, Hagerstown Hydraulics. The wiper ring is an oddball, too thick for AN style and too thin for the "D" style. So on their advice I'm switching to an AN-32 wiper with a back-up ring. The combination gets me to within .009" of the groove width. No more puddles under the mast, hopefully.