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  • Shovel / Loader Bushings

    Has anyone out there replaced bushes & pins on earthmoving equipment? I'm looking to buy a used 4 ton loader (the sort that steers by pivoting in the middle) and I'd like to know how difficult it is to rebush / repin the bearings on the shovel arms, bucket etc.

    I have a decent sized mill, and access to a 12" x 36" lathe, so machining shouldn't be a problem. I'd guess the largest pins are around 2" diameter. I have enough lifting equipment to get the heavy bits off if needed.

    What's the usual repair tactic? Is it to:
    - machine up new bushes & pins and press the bushes in?
    - ream the old bushes in-situ & make oversized pins?

    In the case of the first option (new bushes), do the bushes need reaming to fit once in place?

    Any recommendations on bush / pin materials? Grateful for any words of wisdom from the group.

    Many thanks,

    Ian
    All of the gear, no idea...

  • #2
    The best way if it is possible is to line-bore the welded in bushings in place and make press in bushings to bring it back to the original size.You can do this so long as the bushings you have aren't eggshaped too badly.

    If they are egg shaped then you will have to do one of two things,either weld up the eggshape or cut the whole bushing out and entirely make a new one and weld it in.

    If you decide to cut and weld in new ones the method I use is to cut the weld itself and make the od of the bushings a little larger than the original.When you make the new bushings make the bores about .008-.010" oversized becuase when you weld them in the weld will cause them to shrink slighly.When you set up to weld them make sure that you have both bushings in place on the pin so the pin will keep the alignment,once you have the bushings tackwelded in place in three or four positions remove the pins and finish welding.If you are replacing bucket pins or arm pins where there are two sets seperated by a distance I use a long length of pin material to align all four bushings before welding so when the joint is complete all pins are on the same axis and plane.

    The line boring alternative will work best if you can mount bearings (pillow block)on either side of the bushings to be bored and make yor own boring bar to fit,just a toolbit in a crosshole powered by a 3/4 or 1" drill motor.Set it up and take lite cuts.003-.005" per pass,if more than one set of bushings is envolved then do the same as above using a long enough bar to span all bushings.

    One word about pin material,don't use cold rolled(1018-1020)waste of time,it is too soft and pounds out quickly.My favorite material is 4140-B7,it is cold rolled and heat treated to 38-40 rockwell c ,it still machines good,but is nearly three times as tough as common colled rolled,another alternative is through hardened hydraulic cylinder rod,a good bit harder than even the 4140,but even tougher.

    Make sure the pins are locked stationary to the machine frame and the grease is fed through the working bushing and not through the pin,I have seen through experience that gun drilled pins fail and they always fail in the crosshole.

    I just need one more tool,just one!

    Comment


    • #3
      Thanks Wierd,

      That's exactly what I was after - I like the idea of using hydraulic rod.

      The machine I'm going to look at doesn't look to be too bad, so I'm hoping I don't find severely oval holes (if I do, the rest of the machine is probably shot, and I'll look further).

      I'd been thinking that the various holes would have been bronze lined - from what you say, it sounds like this isn't the case. If I need to bore the existing bushes out, is rebushing with hard bronze a good idea?

      I was wondering how to line bore the bushes - a 4 ton loader is a bit big to hold in my mill's vice! I hadn't thought of a pair of plummer blocks and a drill.

      Thanks again,

      Ian
      All of the gear, no idea...

      Comment


      • #4
        Ian,
        You work in the oil rig game. One of my customers Mirage Machine tools supplies a range of clamp on boring machines that can do this work.
        Any chance you could 'borrow' one ?

        Also bronze bushes aren't a good idea. They cause the shaft to wear more than the bush in dry applications.
        Daft as it sound Devcon plastic bushes last up far better and cause less wear to the pin.
        Plus side is they are 'self reaming' if you have a big enough hammer, and can take up ovality by spreading to fill.

        John S.
        .

        Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



        Comment


        • #5
          "Daft as it sound Devcon plastic bushes last up far better and cause less wear to the pin"

          First time I saw large "plastic bushings" was on the back of a deep sea dragger.The shaft was ~10 feet long and 120mm in diameter.The plastic bushings were mounted in a steel
          "pillow block".They were about 12-15 mm thick.Ask the chief how they were holding up and he said in broken English 'Great'.
          Plastic bushings are used in shrimp and crab plants on stainless shafts.They hold up longer then regular bearings or bronze bushings.But they are still a hard sell to some people.

          [This message has been edited by motorworks (edited 05-23-2004).]
          please visit my webpage:
          http://motorworks88.webs.com/

          Comment


          • #6
            Ian,most of the loaders I see are in the 6-12yrd bucket variety,it is quite common for them to have hardened steel bushings in them,the mfgs use needle bearing races for their wear bushings.

            You might try going to the mfg for the weld bushings and wear bushings,even the pins.I know JohnDeere and Komatsu both supply replacements for their units and they are quite reasonably priced.

            One more piece of info that might help,the amount of wear and lubrication the pins recieve is determined by the material the loader will be moving.

            For topsoil and clay the normal grease and bushing material is fine,stone,stone dust and river gravel you need extra heavy grease with indicator dye(starts out red and clear like strawberry jam and turns black as it gets dirty letting you know when to grease the joints)for beach,silica and quartz sand you need thin grease and the wear bushings should be the graphite impregnated fiberglass,if you use steel,bronze or mon-poly plastic the silica dust will eat them in short order.

            I don't know how much experience you have on these loaders,but believe it or not the operator is at least 50% of the wear on a set of bushings.A good operator can load 8 hours a day for a year or better on a set,a novice can get maybe 3 months.

            I'll try and post a link to the bushings I'm talking about.
            I just need one more tool,just one!

            Comment


            • #7
              Look here-

              http://www.mcmaster.com/

              Page 1008,look for the PTFE/NOMElined fiberglass bearings with the 25,000 pv rating

              Hope this helps
              I just need one more tool,just one!

              Comment


              • #8
                Realizing it isn't the same, but a cherry picker they rented at work has a big bronze shaft. About 5" diameter, I wonder if that would work in the right alloy. Probably not for long.
                david
                A serious accident is one that money can't fix.

                Comment


                • #9
                  When I did this exercise on a Loader/Backhoe I was able to buy 4140 "ground round bar" in the exact size I needed for the pins. This saved a lot of machining as I only had to drill the cross-bolt holes and cut to length. Better finish than I'd get on the lathe. Original pins were quoted at $150 each here in Oz. I bought 3' of bar for $20. I used round hollow section (same material) for the bushes and machined to suit. Still going great.

                  Chris.

                  Comment


                  • #10
                    Thanks again guys,

                    It would never have occurred to me to use steel bushes in the pivots, let alone polymers in that service! I'll look at the reinforced PTFE bushes. I can appreciate that the bushes (especially at the bucket end) lead a pretty rough life, and often don't see a grease gun from one job to the next.

                    John, little hope of finding a bolt-on boring machine here offshore; we might be able to rustle up a gas axe and a 48" pipe wrench though...

                    Wierd, on the operators - I'm sure that the operators who give the bucket a good hard rattle with the hydraulics to shake soil & clay loose are the ones with machines that eat bushes for breakfast. I'd not heard about different greases for different applications; I'll be digging 'oles in clay & soil. Experience on loaders? Er - about 15 minutes so far...

                    Chris, how much clearance did you allow between the rod & bush bore?

                    Great advice, many thanks.

                    Ian
                    All of the gear, no idea...

                    Comment


                    • #11
                      Actually,the good operators keep the ruts smoothed over and filled in the loading yard,bouncing over them all day beats the pins right out,plus the good operators climb off the machine at the end of the day and walk normally,the novices are huanched over and holding their backs

                      No you don't ram the pile,and you don't power into it either,both will kill a tranny or torque converter.Best way is to approach in low gear at half trottle with the bottom of the bucket at a 5* down angle,as soon as the edge digs in to the pile you apply power,tilt the bucket up and raise the bucket all at once,by the time the bucket is rocked up on the stops and lifted to daylight your foward motion should be stopped and the engine returned to idle,shift to reverse and back out,don't worry,after you practice 6 or 700 time you'll get the hang of it
                      I just need one more tool,just one!

                      Comment


                      • #12
                        Wierdscience, you must have run a loader in your past life. Everything you have been saying on this thread is soooooo true!!! I built a miniature bulldozer in 1986 with a front end loader on it, steel pins and bushings. The undercarriage didn't last long, so upgraded to plastic type [Redco 750] bushings for much improved life. A few years later, I built a backhoe using steel pins and steel bushings. Yes, I use the Extreme Pressure grease, and yes, if you don't pay attention, the pins will break. In fact right on the pre drilled grease cross hole, just like you said. Anyhow, heres a picture of my machine in action on the side of a mountain. The footprint on my machine is 36" wide and 60" long. Still runs great with over 1000 hours on it. Anyhow, I just had to tell you wierd, that you are right on..... as to all the tips re pins and etc....

                        Comment


                        • #13
                          Errol,
                          You built that!? I'm impressed, do do have any more photos and info?

                          Comment


                          • #14
                            Ian, I think I made the holes in the bushes .010" bigger than the pins. I have no idea what the clearance should be, but I had no trouble with fit after welding the bushes in place and it was a heck of a lot better than before (one pin was broke!).

                            Chris.

                            Comment


                            • #15
                              Peter S, Here'a another one for ya. My daughter splitting wood back with my wood splitter just built last winter. Powered by remote hydraulics from the bulldozer. To give you an idea of size... the pads are 6" wide. total width of machine is 36".

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