Hydraulic dock lift

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Got a problem with a recent project I'm working on.  I'm repairing a 30+ year old hydraulic dock lift.  The lift is installed outside a local grocery store, and is their only means of unloading box truck deliveries.  The company that made the lift went out of business about 10 years ago.The lift has suffered severe corrosion to the base frame and one of the tubes in the scissors that raises and lowers the deck.  I've replaced the base frame, but had to torch out 1 of the pins that attaches one of the scissors beam to the frame.  I've got the lift working again by replacing the pins that attach the scissors to the base with some 1"x8" grade 8 hex head cap scews.  The actual pins are about 6" long, 1.125" diameter, with a highly polished surface.  Both ends of the pin are necked down to about 7/8" with a very fine pitch thread.  A threaded collar with a cotter pin is on each end of the pin to keep it in place.I'm preparing a replacement beam, and I figure I'm going to have to torch out another one of the pins.  I'd like to buy some replacement pins, but I'm not familiar with what the manufacturer used in this machine.Pic 1 is a view of the whole machine.Pic 2 is a closeup of one of the points where the scissors attaches to the original base frame.  You can also see how rotted the original frame was.Pic 3 is the new base frame I fabricated.Pics 4 and 5 are closeups of the rollers on the bottom of the scissors and the pins that hold the roller in place.The same type of pin is used to hold the other pivot points in place.I want to replace the two grade 8 HHCS that I've put in to get the lift working again and I know I'll need to replace another when I cut loose the rotted beam I'm going to replace next.  See the next post for more photos of the next piece of the project.I've searched McMasterCarr for a ready made pin of this type.  I can find threaded collars, but no pins.  I'm not having any luck finding them anywhere else, and I'm really hoping I won't have to pay a machine shop to make me some custom pins.  I'm a little concerned that these pins aren't simple mild steel either.  The bearing surfaces are highly polished, they almost look like they're chrome plated....Any ideas where to look?  anybody seen anything similar on another piece of equipment?  The lift manufacturer used to also make trash compactors, so I'm wondering if these pins are common on that type of equipment? Attached ImagesBenson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:just going to throw this out there- hydraulic cylinder shaft.  there are some variations out there, what I've dealt with had to be annealed in order to machine.
Reply:More pictures of the lift.  One shot of the beam I'm going to replace.  A couple shots of the pins I need to buy and where they get used.  One closeup of the pin that the whole scissors pivots on.  Same style as the pins that attach the scissors to the base frame and the deck, only bigger.I'm hoping I can get the collar off the outside of the main pivot pin, and then put it back after I swap out the beam.  But I'm afraid I'll have to torch the collar off or there are no threads left under all the rust. Attached ImagesBenson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:A couple last comments.  It's a very sturdy design.  I'm not sure what the lift capacity is.  But I bet its way more than the store really needs.  The hydraulic power supply is 5 HP 3 phase 240V.  The two cylinders are massive.  I had to lift the deck and scissors 3" into the air in order to get the new frame in place.  Not fun.  2x2x10 gauge tubing was a little lite weight for lifting this beast.  My 4 jack stands needed a cheater handle on the screws to get the last little bit of lift I needed.Did I mention that this repair went from, "whenever I find the money" to "I need it ASAP" because of a hydraulic line failure?  I cleaned up about 4 gallons of hydraulic fluid from underneath the machine and around it.  Not Fun.  The lift has to be in the up position to remove the hydraulic lines.  There's no safety latch or pawl on this beast.  so loss of hydraulic pressure causes the deck to drop...Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Could be...but I'm really hoping someone can point me to a company that makes these off the shelf.  I don't do this sort of machining myself, so making pins means paying someone else a lot of money to do the work.  I'll do it if I have to, but I'd rather find something off the shelf. Originally Posted by cd19just going to throw this out there- hydraulic cylinder shaft.  there are some variations out there, what I've dealt with had to be annealed in order to machine.
Reply:You need to have a machine shop quote it before you get too excited.  You might be surprised, the right shop could make what you want pretty quick, particularly if you could just use mild steel which is probably what I would do, that lift isn't going to last forever.  Someone could prove me wrong but I'd be amazed if you found these pre-made unless you found an old dealer of that lift or something.
Reply:How about Ohio Industrial supply I go there when I am stumped sometimes. They bought up Associated Supplies near me and those guys know their stuff, they always at least point me in the right direction.
Reply:stress-proof shafting is available from mcmaster. for the slow speeds involved, with grease applied should work fine.. plenty strong, saws and drills easily. comes ground in 1/16 increments. if you have to weld retainer caps or lugs on 11018 welds perfect.
Reply:There's no safety latch or pawl on this beast. so loss of hydraulic pressure causes the deck to drop...Sound like a bobby trap Those pins look a lot like the kind use for loader bucket pins and backhoe outriggers Etc Might got to a tractor / equipment repair and see if you could match themBacked my CATMA over your CARMA oops clusmy me  What would SATAN do ?? Miller Trailblazer 302 AirPakMiller Digital Elite  Optrel Welding HatArcair K4000Suitcase 12RC / 12 VSHypertherm PM-45Rage 3 sawRusty old Truck
Reply:Originally Posted by cd19You need to have a machine shop quote it ...
Reply:Here are some closeup shots of what I need.  As you can see there is almost no wear on the shaft itself.  The only damage is rust on the exposed ends.  All I need is 2 or 3 more of these to put the machine back in almost good as new condition.Killdozer, I'll check the local CAT dealership and see if they have anything similar.  Probably wouldn't buy it there, but at least I can find out if you're right and they're used in some other kind of heavy equipment.  It is not up to today's standards for "safe" equipment.  But it's typically just 3' off the ground, and even if the system sprung a leak the worst is a slow drop to the ground.  It's only a little nerve wracking if you have to work on it with the hydraulic system disconnected.  then you need to spend the time to properly block the machine so nothing moves.DBL612,  I thought about buying some stressproof TGP shaft and welding some retaining plates on the end.  That's probably where I'll end up.  I'd rather put in something threaded rather than welded, so if I or somebody else has to work on this thing again, it doesn't have to be torched apart.  Maybe I'll buy some shaft, then drill and tap the end for a bolt that will hold a retaining plate on one end.  I can weld the plate to the other end.  That makes it removeable...Fabn4Fun, right now there's no time pressure on this job and I can spare the time at the moment.  So a little time looking for a ready made part isn't a big deal. Attached ImagesBenson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:http://www.use-enco.com/1/1/81671-pr...ound-rods.html"Any day above ground is a good day"http://www.farmersamm.com/
Reply:I would heat those rusty ends until they were smoking hot, but not red, then hand-wire-brush the threads while still hot and let them cool naturally in air.  Hand wire brush again when cool, chase with die if necessary, then oil lightly and reuse.    That notched nut will come off  nicely if heated to a dull red.  You can treat it and the other end the same with a wire brush.   Use a plumbers brush for internal threads.Those pins, and the nuts on each end, have nearly zero tension on them, it doesn't take much to hold them in place.  A little blue lock-tight for comfort and I think they will last a lifetime.- MondoMember, AWSLincoln ProMIG 140Lincoln AC TombstoneCraftsman Lathe 12 x 24 c1935Atlas MFC Horizontal MillCraftsman Commercial Lathe 12 x 36 c1970- - - I'll just keep on keepin' on.
Reply:It very unlikely you will find those pins as standard stock but the nuts are readily available at a bearing  supply as kn nuts.Briggs weldnpower 225/210/cvLn-25 suitcaseMillermatic 130
Reply:Farmersamm, Mondo, Winmac.  Thanks for the posts.  The pin in the photo I will surely reuse.  But I'm going to need 2 more.  Getting the pin shown in the photo out wasn't hard.  The matching pin on the other side was another story entirely. The acess to the pins wasn't good for hand tools.  .  The other one was so badly rusted in place I had to hammer it out in 3 pieces after cutting it with a torch.  I had trouble putting out the fires that sprang up from the whole ground being soaked in hydraulic oil.  Even set fire to grease inside one of the scissors beams and had to bust out my travel size fire extinguisher.I found a lead on a local supplier who might have supplied the OEM with this hardware.  Going to pay them a visit.  Otherwise I'll buy some TGP shaft and make up two more pins on my own.  I'd like to replace with identical hardware, but I don't think it's mandatory in this case.  This lift probably moves two or threes times per day, 5 days a week.  Even over 30 years that just a few thousand cycles.  There's no visible rust on the pin where it bears on the mating surfaces of the frame and the beam.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Looks like drill rod to me. I'd cut a section to lenght,drill it,tap it screw on a cap and call it a day.Gizzmo
Reply:From your pictures the pins look to be chrome plated. If they are a standard inch size you probably could get them made at a hydraulic repair shop that does cylinder repair.
Reply:You might be able to adapt cat 3 lift pins.
Reply:Thought you all might like some progress pictures.  I've fabricated a replacement beam for one side of the scissors mechanism.I snapped these three shots last night after welding the end tabs to the beam.  For those interested, Millermatic 211 with 75/25 gas, 0.035" 70S-6 wire, and max voltage and wire feed speed.  The side plates are 1/2" thick A36.  the Tube is 1/4" wall ASTM A500.  The small gusset plates between the side plates are also 1/4" thick.  I figure the duty cycle on the machine is about 10% at those settings, so I welded 1 area, and then waited a while before welding the next bead.  The small gussets were gapped about 1/8-3/16" from the end of the tube, so there's 100% penetration to the inside on those welds.  I did back the machine off for those 4 welds, as there was more than enough heat to melt back the 1/4" plate.Then drilled a 1/4" hole dead center in the beam from each side.  Followed that with a 3" hole saw to bore a hole for the main pivot bushing.  That old drill press of mine doesn't have much torque.  So drilling those 3" holes took 5-10 minutes for each one.  Flooding the tool with WD40 aerosol spray helped keep things cool and flush the chips out of the groove.After some internal debate, I'm going to salvage the bushing from the old beam when I remove it tomorrow.  Then I'll clean up the OD and weld it into the new beam.  There is a lot of play in the ID of the bushing, so I'm not too concerned about it warping so much that it won't fit back on the pivot pin.The beam has a coat of primer on it that's being drying since last night, and I'll hit it with a top coat of semi gloss black before calling it a day. Attached ImagesLast edited by A_DAB_will_do; 09-13-2013 at 01:53 PM.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:FYI Mondo,I took my torch with a small welding tip back to the lift last weekend.  I wanted to double check my location measurements for the holes in the beam and the diameter of the main pivot pin.  I used a 0 size welding tip to slowly heat the lock nut on the 2" diameter pivot pin.  Then a hammer and a cold chisel to get it moving around and off.  Took maybe 10 minutes to have it off.  It took more time to drive out the 30 year old cotter pin that locked the nut in place.Heating it worked like a charm.  I boiled some of the grease in the joint; but at least I didn't set fire to it this time. ... Originally Posted by MondoI would heat those rusty ends until they were smoking hot, but not red, then hand-wire-brush the threads while still hot and let them cool naturally in air.  Hand wire brush again when cool, chase with die if necessary, then oil lightly and reuse.    That notched nut will come off  nicely if heated to a dull red.  You can treat it and the other end the same with a wire brush.   Use a plumbers brush for internal threads.Those pins, and the nuts on each end, have nearly zero tension on them, it doesn't take much to hold them in place.  A little blue lock-tight for comfort and I think they will last a lifetime.- Mondo
Reply:Originally Posted by killdozerd11There's no safety latch or pawl on this beast. so loss of hydraulic pressure causes the deck to drop...Sound like a bobby trap
Reply:end of the project and all is well, at least until rust kills some more parts on the lift.  I talked with the owner about getting a local outfit to blast and repaint the lift.  But the ball's in his court for now.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Well bout time you gotter donekidding ..nice workBacked my CATMA over your CARMA oops clusmy me  What would SATAN do ?? Miller Trailblazer 302 AirPakMiller Digital Elite  Optrel Welding HatArcair K4000Suitcase 12RC / 12 VSHypertherm PM-45Rage 3 sawRusty old Truck
Reply:Customer asked for some flexibility in payment plan, so I took some extra time in finishing the work.  That, and they needed to use the lift during the week, so it was just less hassle for both of us if I worked on the equipment on the weekends.Good for them and good for me...Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Grocery store. You could take payment in Food or products. DanNice repair!I like heat!I like paint, too.And Groceries!Did I say I'd like to have one of those for working on lawn mowers, lawn tractors, field mowers, and such?  Gawd I hate bending over and groveling about on the floor when servicing small machinery.  Makes me grumpy.  - MondoMember, AWSLincoln ProMIG 140Lincoln AC TombstoneCraftsman Lathe 12 x 24 c1935Atlas MFC Horizontal MillCraftsman Commercial Lathe 12 x 36 c1970- - - I'll just keep on keepin' on.
Reply:Nice repair. Is the reason it rusted out so badly due to water collecting in the angle iron frame? Did you cut a few drain grooves into the concrete?
Reply:Forhire,I simply replicated the original design.  The original lasted 30+ years, and if the owner gets it re-painted, I'm willing to bet it'll go another 30 years.  From my point of view, replicating the original design was a safer option from a liability standpoint; so I tried to get everything as close as possible to what was there.  A couple holes sounds like a logical design option; but I didn't think of it.  All the beams are hollow, and they're enclosed by the lift deck when the lift is in the down position.I'm not certain why the bottom of just one beam in the scissors rusted out.  The other 3 beams have corrosion on the bottom surfaces, but none of them with through holes like the beam I replaced.  Likewise, the base frame only rusted out in that corner; the rest of it was in relatively good shape.  The only theory I can come up with is that the concrete pad the lift rests on has a low spot in that same area, that retains water.  I've never been there when just after a rain or snowfall.  But in any case, correcting problems with the pad is beyond the scope of work I'm willing to take on.  I suspect it's also beyond the financial means of the store owner.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector