Larrys PM Research #4

Discussion in 'Engines From Castings' started by larryg, Apr 24, 2019.

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  1. Aug 13, 2019 #21

    larryg

    larryg

    larryg

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    So with the V block work done it on to other steps. For me it was figuring out how to hold the rod. Digging in the scrap box I found this black piece ( fixture);

    [​IMG]

    It was machined nice, square, and parallel. The rod itself has an offset of .1625" from the side of the big end and the small end. So I machined the end of another piece of scrap to .1625" as a spacer for the big enc. Centered on one end and .650" up from the end of the fixture I drilled a tight clearance hole for a 1/4" shcs and counter bored the back side. I also drilled and tapped a couple of 1/4-20 holes to align with the angle fixture I have to hold it vertical.

    [​IMG]


    So with the fixture bolted to the mill I aligned it to the travel,

    [​IMG]

    Once aligned I located the the rod end and drilled and tapped the for the rod bolts.

    [​IMG]

    lg
    no neat sig line
     
  2. Aug 13, 2019 #22

    larryg

    larryg

    larryg

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    One on the handicaps of my mill is there is no downstop for the spindle so I have to come up with a creative way to drill precision depth holes. On this set up I drilled the tap size holes through the rod cap and then went back and drilled the clearance hole for the rod bolt. To do this I set the drill to where I wanted to stop.

    [​IMG]

    From there I have a split shaft collar on the spindle that I set to stop the quill when the collar contacts the upper pulley,

    [​IMG]

    If I have to drill down from a surface I will lower the spindle contacting the surface with the bit, set the collar on the pulley, lift the spindle and then raise the knee the depth I need to drill to.
     
  3. Aug 13, 2019 #23

    larryg

    larryg

    larryg

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    Next step is to separate the rod cap from the rod. I used a slitting saw for this as used previously on the pillow blocks. So with the fixture I know that the center of the small end is ~ .650" above the table and the rod length is to be 7.12" and the saw is .055" so the top of the saw should be 7.825 or so above the table top and this was set with the height gauge.

    [​IMG]

    [​IMG]

    Also notice the block clamped to the spacer. I did this to keep the rod from moving sideways from the force of the sawing.

    [​IMG]

    We have successful separation...yea.

    lg
    no neat sig line
     
  4. Aug 13, 2019 #24

    larryg

    larryg

    larryg

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    So for boring the big end the fixture was separated from the angle and clamped in the vise,

    [​IMG]

    The end of the fixture was located,

    [​IMG]

    and then the end of the rod was located so as to confirm that the rod length was correct and where the center of the split was so the boring bar could be centered.

    [​IMG]



    The boring was done with the same setup as in the above picture. I did add an additional clamp that grabbed the sides of the rod and the fixture to keep the rod from moving sideways. It was just dumb luck that the fixture was the same width as the rod allowing this clamping to happen with our packing.

    [​IMG]

    [​IMG]

    For slotting the small end I replaced the SHCS holding the rod to the fixture with a shortened one that only engaged the rod to a depth of ~.235 so I would clear it with the slotting cutter.

    [​IMG]



    It all worked out and I now have the short block assembled and the crank will turn with less that 20ft-lb of torque..:)

    [​IMG]
     
    Last edited: Aug 14, 2019
  5. Aug 14, 2019 #25

    larryg

    larryg

    larryg

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    A couple of pictures of the fixture. As I said it was a piece from the scrap bin and the outside profile has nothing to do with this project.

    [​IMG]

    [​IMG]

    lg
    no neat sig line
     

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