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Shaper part repair options/opinions sought

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  • Shaper part repair options/opinions sought

    I have been running my Whipp shaper and figuring out how it works. One thing that is very annoying is that the yoke follower that drives the ram has significant wear on the bosses the yoke acts upon. It makes a loud clank twice per stroke as the ram changes direction.

    This is the yoke:



    This is the follower. You can see how the normally round bosses have been hammered by long use. The bosses are nominally 1.750" diameter but across the hammered area are only 1.720". There is some corresponding minor wear on the yoke itself but it seems to be made from sterner stuff and the wear is slight.



    The question is how to approach a repair? The part is cast so I don't want to try building it up with welding. I can turn it just fine in my lathe so several other options exist.

    I could cut the bosses off and fit new ones made of hardened alloy, fitted into a machined recess and held via a bolt.

    I could turn down the boss and fit a sleeve of some sort which is the direction I am leaning. The question here is what sort of sleeve to fit?

    It could be plain steel (I have no cast iron large enough). It could be hardened steel. Or, it could be something with some compliance to really eliminate all noise. The operation of this part is very simple, it just actuates the ram. I don't think adding compliance here would make a difference but I may be wrong. The ram itself is quite heavy, well over 100 lbs on this machine. I was thinking of using acetal sleeves. Acetal has excellent periodic impact resistance, better than mild steel and and recovers from impact instead of permanently deforming as steel does.

    Suggestions?
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  • #2
    Shaper Repair

    Hi Evan,
    Do you think that after turning it down that roller bearings could be put on the trunnions. The clearances could be minimized to prevent any excessive slack. If the rollers in the bearings are large enough it should work.
    Chuck

    Comment


    • #3
      Needle roller bearings would work, but they'd have to have some significant rotation to them during use or they will become damaged. I would almost be tempted to make up a plastic slider piece that would fit over the turned-down bosses, and slide within the yoke. Possibly the yoke would have to be machined out a little to accomodate.

      Another thought is to leave all that metal alone and just use an insert strip to take up the extra play. I'm thinking of maybe some spring steel strip like found in a measuring tape.

      You could heat that strip in one spot to bend a 90 in it, then attach it with a bolt tapped into the end of the forks. One per side, of course. Another way to attach the strip would be to wrap it around the bosses, overlapping a bit where the boss doesn't contact anything, then drill through the overlap into the boss, tap and screw down. I don't think I'd want to remove any metal from the parts, unless just enough to accomodate a shim, if that's what you do.

      I don't know how much room there is to fill, but another material that might be good for that is steel banding. That seems to have some properties that would give it a decent lifespan for this application.

      I imagine some kind of EP lube would be good there.
      Last edited by darryl; 06-02-2007, 02:46 AM.
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

      Comment


      • #4
        I don't have any suitable bearings to try and that sounds like a possibly expensive solution, especially if they can't take the small periodic motion which is a major problem for rolling element bearings.

        I can't think of a way to machine the yoke faces although the wear there is no more than a few thou so it shouldn't make that much difference. It's too large and heavy for my machines to handle.

        Why do you object to the idea of removing more than a tiny amount of metal from the parts? I don't think taking off maybe .100" will reduce the strength enough to matter. The inner end of the left pin is already intentionally undercut about that much.
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        Comment


        • #5
          How about turning the bosses down and slipping square blocks over them? This will give you something that resembles a steam engine crosshead; the bosses will turn in close-fitting holes, and the outer face of the blocks will have a larger contact area in the yokes than a cylinder (like the previous bosses).

          Not sure if the yokes are deep enought to accommodate this solution, but it may work.

          Ian
          All of the gear, no idea...

          Comment


          • #6
            That's how the yoke arm itself is driven from the bull gear. That may be a possible solution if there is room. I will have to check on that.
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            • #7
              If there's not enough room to allow for a sliding block, could you machine the ends of the yoke flat and bolt a plain bearing into each side of the yoke? Then make a short link to fit between the yoke end bearings and the bosses on the block that locks to the ram.

              This leaves you with only rotating bearings, none sliding at the end of the yoke. It'll move the block forwards (or backwards, depending if you go for a leading or a trailing link), maybe the machine has enough room to accommodate this.

              Ian
              All of the gear, no idea...

              Comment


              • #8
                Turn it down and use plain steel as the ring.
                I'd sooner replace rollers than have to machine the fork later when a hardened bush or bearing has worn it.

                [edit] Just re-read this bit,
                I was thinking of using acetal sleeves. Acetal has excellent periodic impact resistance, better than mild steel and and recovers from impact instead of permanently deforming as steel does.
                Evan this isn't quite true, although it's a good medium and better than steel or bronze it does deform. Many big trucks have these are spring eye bushes and they wear very well, far better thna anythig used previous. However if there is side float in the hangeer brackets it deforms the bush out and so reduces it's diameter causing slack.

                Looking at the room you have, and I think you just have enough what about using acetal sleeves slightly longer than the cast boss and secure it with a top hatted washer and countersunk screw into the end of the boss.
                This will give you a bush that cannot squeeze out.

                May be possible to top hat the acetal sleeve ? Only you know how much room you have.




                .
                Last edited by John Stevenson; 06-02-2007, 05:07 AM.
                .

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



                Comment


                • #9
                  Thanks for that info John. Yes, I think there is just enough room either side to restrain the bushing. I shall need to check the full range of motion to be sure. Then acetal is what I will try first. Do you have any suggestion on the amount to take off the trunnion to allow for the bush?
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                  • #10
                    Personally I'd go for a wall thickness you were thinking of at around 0.100" to 0.125" but from the pic's I'm not sure what you have to play with.
                    [edit] just read 1.750" so yes somewhere around the above figures.

                    Any more will weaken the trunnion and any less will hammer the bush out.

                    One thing about acetal is that it's self tolerancing , a few thou up and it becomes a snug fit.

                    You should have the quietest shaper around

                    .
                    .

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



                    Comment


                    • #11
                      I tried the acetal trick on a power hacksaw linkage once,different machine,but the same exact linkage.It worked for about two hours,the point load did it in,too small a contact area for the plastic to stand.It compressed/squeezed out and fell off.

                      The usual cure for that is a 4140 ring .125" wall as John suggested with a shrink fit.
                      I just need one more tool,just one!

                      Comment


                      • #12
                        Well, it's worth a try and I might try making the acetal bushes in a block shape to help spread the load. It isn't difficult to remove the ram enough to access the part and if the acetal doesn't work out I have some nice annealed 1040 material to make steel bushings with. I suspect the acetal may hold up as the action of the shaper is very smooth with relatively low acceleration and deceleration of the ram, as long as it isn't loose.

                        Thanks guys. I shall let you know how it works when I have time from sundeck construction to play with it.
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                        • #13
                          Wow, first off I hve to say that that thing is surprising to me, I never thought the drive mechanizm on a shaper would be so crude as far as the potentual for wear,,What lubricates it Evan, Do you just reach in there and aply grease now and then?

                          Like allot of the guys my first thought was needle bearings but this whould only address one of the problems, Im with Ian B --- a really good plain bearing block style fix for you that would last forever if kept lubricated, why they did not do something like this in the first place makes me wonder as this is the "heart" of your machine...

                          turn your drive yokes down to what you deam sutible to keep the strength yet allow a compatible sleeve to slip over (preferably a sleeve with zirk fittings and an oil groove cut in the center)
                          Then, DO NOT make the outer part of the sleeve round, Make it square and build it to tolerence to glide between the yoke drive, it might end up having one rounded side for clearence of the yoke drive and thats ok however, try to milk as much surface area out of this as you can, have small grease holes coming from same zirk that lubes inner bushing to lube outer block slides, Now you have a wonderful gliding action with tons of surface area while the other part is a perfect pivot, excellent fix,,, I would not even consider using acetal but thats your call...

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                          • #14
                            I agree with AK's assessment. If you can replicate the bull gear pin to yoke bushing concept then you will be home free. I would recommend 660 bronze, but steel could work as the two other parts are cast iron.

                            My Ammco needed new bushings (and shafts) for the the yoke to ram connector but it isn't a direct connection like yours. I religiously lube the machine now as there was clearly a lack thereof in its previous life.

                            Regards,

                            Geoff

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                            • #15
                              Bronze is another possibility and I have the material to make bushes or blocks. The only problem with the sliding block idea is that the trunnions come very close to the bottom of the yoke in operation. I could make the blocks with a round bottom to fit the yoke... I'm still going to try acetal first.

                              I knew there was a reason I have been saving this piece of 660 bronze.

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