Doosan pivot pins. Old story, new to me

Ok all you experienced hands. Looks like I inherited a half done job…again.

Got a DL250 in the shop halfway split. Front and back are up on blocks and I guess whoever was doing it isn’t going to finish the job. I’m told it needs pins and bushings. Is there somewhere a good how-to on splitting this thing to replace the bushings? Pins are the easy parts but it would be impossible to cut out and replace the bushings or bearings that reside in the rear half. I get to write up a procedure for this, and get to supervise. Too heavy for my broke down back to be wrestling.

Any and all advice will be appreciated!

As it sits…

Keep an eye on your messages ............

I don't what anyone else thinks but from the looks of it getting the top pin out with the cab in place would have been difficult enough. Installing new bearings into the top hitch, setting the bearing adjustment, and then lining everything up to install a frozen new pin into the hole, without first removing the cab, is going to be damn nigh impossible.

I would hazard a guess that the guy that got this far ran into just that issue, Nige. Our truck shop manager, who has worked for a few equipment dealers says he isn't touching it. He's a Case guy and I am guessing they are different enough to make him want to distance himself.

I have a 30t crane available, as well as others, so I can lift and move pretty much anything I need to on it, but just at first blush, I'd think the counterweight would make moving the rear half (heavy half, I presume) fraught with problems. Unfortunately, this machine was driven into the shop bucket first, so it will be a little awkward to pick, but I think I can get the front out. If you notice, there is a puny looking turnbuckle holding part of this together, so I see some risks in simply trying to slip it apart, after breaking the rest of the hoses off the bulkhead. If I had a bridge crane in the building, or better yet a dual, I'd be more comfortable with using some spreader bars and some I-beam under each half rather than sitting on wood blocks.

And you're right...the bearing clearances I don't have specs for or any procedure in hand for setting the preload. The cab may end up being removed. Fortunately, this is not a rush job. It's been sitting as you see it for at least 90 days.

This is how we did everything up to the size of a 994 which goes 220 tons all up if we were going at it from the rear of the machine. Just needs adequately sized tooling bearing in mind the weight of the machine you're working on IMO.

• Set the bucket on the ground.
• Block the back side of the front frame up to the required height. Already done in your case according to your photos.
• Pull the cab.
• Pull all the connections (drive shafts, brake lines, electrical, hydraulics, etc) that cross the articulation hitch. On your Doosan the drive shaft to the rear axle might have to come off as well, I dunno. It will to some extent depend on how (and where) the park brake operates.
  
• Get a suitably-sized forklift under the counterweight to take the load. TBH the weight won't be anywhere near what you expect because on its wheels the rear frame is still somewhat balanced, especially with the cab already off. We used to put some 1-2" timber on top of the forks so there was little chance of them slipping steel-on-steel.
• Chain the loader counterweight to the forklift mast so that the rear frame of the loader HAS to move with the forklift.
• Pull the upper & lower hitch pins.
• Reverse the forklift until you have enough room to work in the area around the hitch.
• Set the rear frame on blocking front and rear. Normally they always want to tip backwards because of the counterweight but it makes people more comfortable if they are blocked at both ends.

When reassembling it's the reverse of the above but you might just need two jacks, one under each side of the back side of the front frame, in place of the blocking that's there now, to do the fine adjustment necessary to line up the hitch pins.

Check your email ...........

Turns out we have an old Roanoak lift in the truck shop next to mine, but the head is off and they haven't needed to put it back together. Now I'll get them to get it running and about the time they do, I may be ready to work on this Doosan. I believe it is a 20k lift. Overall it's in good shape, just had a blown head gasket, so we did the valves since the head was off, and got a fresh radiator for it. Just need to reassemble it. (I hope) But there are still others I can bring in if that doesn't work out. Just happened that the owner was about to ask me to look into it. He didn't know I was already studying up on it. So the timing was about right.


Oh, and Nige, earlier in the thread you referred to a "frozen pin". I gather that you meant shrunk with a cold bath to ease the fit. That right?

Tony Wells said:

Oh, and Nige, earlier in the thread you referred to a "frozen pin". I gather that you meant shrunk with a cold bath to ease the fit. That right?

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Yessiree Bob. F**k beating the sh1t out of the pins with an FBH to get them in. A couple of gallons of liquid cold and they’ll drop right in there.

Re-reading this. Forgot an important point.
Wheel chocks under the front tyres, both sides of the machine front and rear, so it doesn't go anywhere if it gets accidentally bumped.

Agreed. Fronts chocked solid, but rears have to roll back during the actual separation, then chocked solid again.

Tony Wells said:

Agreed. Fronts chocked solid, but rears have to roll back during the actual separation, then chocked solid again.

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100%. To eliminate any possiblity of movement requires a total of 8 wheel chocks.
TBH I would chock both sides of the front axle first, then install two chocks on the front side of the rear axle - thus preventing the rear rolling forward when the hitch pins are pulled. The rear will roll away from those two chocks as it is pulled backwards and they can be repositioned and two additional chocks installed once the rear end of the machine is in its final resting place.

That's the way I see it. First things first though. Have to determine for sure that the cab has to come off. Pretty sure it does, so that's where it starts. I have a welder/fabricator and a mechanic to work with on this once we get the lift back together. Will not be soon, I'm afraid. Too many hotter irons.

FWIW I would remove the cab now and before doing anything else if for no other reason than to ensure that the rear half of the machine is biased to be “tail-heavy” when you come to move it backwards.

I feel that the cab has to come off at some point before you try to reassemble because otherwise there would be no space to either check bore alignments between the front and rear frames or to start the upper pin in the bore. Even if the pin is frozen it will likely need some form of persuasion. IMHO how much persuasion it might require would be totally dependent on how good the bore alignment is. My late grandfather had a saying for circumstances like this - "99% preparation, 1% perspiration".