A new chassis for a Bachmann U33B.

Discussion in 'The Academy' started by Ray Marinaccio, Jun 16, 2004.

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  1. Ray Marinaccio

    Ray Marinaccio Active Member

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    This is the start of the brass frame.
    The frame rails are 7/32" x 7/32" angles cut to 7 11/16" and notched to clear the steps.
    The end cross members are 3/16" x 3/8" rectangular tubing cut to 3/4".
    The bolsters and coupler mounting pads are 1/4" x 1/8" channel.
    The king pins were turned on the lathe. They are 3/32" dia. and 1/8" long with a .050" high and 1/8" dia. head.

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  2. Ray Marinaccio

    Ray Marinaccio Active Member

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    This is a crude drawing showing dimentions.

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  3. Ray Marinaccio

    Ray Marinaccio Active Member

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    3/32" holes were drilled in the bolsteres and the king pins were inserted and soldered in place.

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  4. Ray Marinaccio

    Ray Marinaccio Active Member

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    The frame rails and end cross members were clamped to a piece of wood and soldered.

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  5. Ray Marinaccio

    Ray Marinaccio Active Member

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    To solder the tops of the cross member, the frame was clamped in a vise with popsicle sticks as insulators.

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  6. Ray Marinaccio

    Ray Marinaccio Active Member

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    The coupler mounting pads were then clamped in place and soldered.

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  7. Ray Marinaccio

    Ray Marinaccio Active Member

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    .016" shims were placed between the frame and the wood to get the correct bolster heighth. The bolsters were soldered in place with the king pin 1 13/32" from the end of the frame. A heat sink was used to keep the king pins from moving during soldering.

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  8. Ray Marinaccio

    Ray Marinaccio Active Member

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    Frame with trucks installed.

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  9. Ray Marinaccio

    Ray Marinaccio Active Member

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    Frame with shell installed.
    Building the motor mount and fuel tank will follow as the project continues.

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  10. Ray Marinaccio

    Ray Marinaccio Active Member

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    Thanks Brian and Fred.
    The trucks are 1973-1983 vintage Athearn trucks. They willbe replaced with the 1980 and newer truck though because the mounting tabs for the metal sideframes come to close to the frame and will short out on curves.
    Any GE or Alco 4 axle truck could be used by moving or modifying the bolster.
  11. Ray Marinaccio

    Ray Marinaccio Active Member

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    Thanks jmarksbery and Robin.
    I swapped the trucks with another loco today and took measurements to calculate how far the motor needed to be recessed into the frame.
    I'm using a Bachmann motor with mount I got in a parts lot.
    The dimensions and possibly design of the mount may need to be different with a different choice of motor.
    To figure out the depth of the mount I measured the distance from the bolster plate on the truck to the center line of the worm shaft. Then subtracted that from the measurement of the centerline of the motor shaft to the bottom of the motors mounting bracket. Then subtracted the measurement of the frame bolster to the bottom of the frame. This came out to be 3/16" below the bottom of the frame rail.
    The one piece mount I designed will also include the frame floor and air tank hangers. It is made from .015" brass sheet.
    A large hole will be drilled in the center of the mount to fill the fuel tank with ballast after it is installed.
    There must be a .010" gap between the air tank hangers and the mount for the fuel tank to insert into.

    This is a crude drawing of the mount. The red lines in the upper diagram are the fold lines.
    I have the mount cut out and will get photos as I make the bends.

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  12. Ray Marinaccio

    Ray Marinaccio Active Member

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    After the dimentions were scribed onto a piece of .015" piece of brass sheet and cut out I began forming the bends. I started with the sides, clamping them between two 1/4" square bars in a vise and bending them over and flattening them out with a small hammer.

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  13. Ray Marinaccio

    Ray Marinaccio Active Member

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    This shows the first two bends completed.

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  14. Ray Marinaccio

    Ray Marinaccio Active Member

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    A 3/4" wide block was used for the next two bends.

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  15. Ray Marinaccio

    Ray Marinaccio Active Member

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    This shows those bends completed.

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  16. Ray Marinaccio

    Ray Marinaccio Active Member

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    The assembly was then clamped in the vise long ways as shown. The tops of the sides should be flush with the top of the vise. This will make the floor pannels higher than the sides so they will be up inside the frame rails. Then bend the ends down.

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  17. Ray Marinaccio

    Ray Marinaccio Active Member

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    The air tank mounting tabs were bent down as shown.

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  18. Ray Marinaccio

    Ray Marinaccio Active Member

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    The holes were drilled and the air tank mounts were filed.

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  19. Ray Marinaccio

    Ray Marinaccio Active Member

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    The assembly was then centered, clamped in place and soldered.

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  20. Ray Marinaccio

    Ray Marinaccio Active Member

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    Here's a photo of the project so far.
    The fuel tank will be next.

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