Bachmann large 2-10-4 repower and regear project.

(White removable motor style)
    2-10-4
  1. Use original frame, wheels, valve gear, axle retainer, floor, trucks and all screws and spacers. Remove CAREFULLY all valvegear and cylinder blocks.
  2. Purchase: NWSL #136-6 28:1 double idler gearbox, NWSL #482-6 U-Joint kit, any can style motor under 7/8" width. (I used the flat can FF-18DPH KN158213 motor with 0.187" shaft. It is 1.425 long x 0.604 high x 0.797" wide.) And a strip of 0.030 x 0.188" styrene. And possibly some 0.187" DELRIN rod.
  3. The rear of the frame is held by the original motor screws. These will disappear. Carefully measure the rear frame width. Mine was 0.512" at the very top rear corner. The inside surface has ripples here. These must be cut away and a plastic block made to fill the space. Use a plastic thru bolt or (2) short screws that will not touch each other. The original width must be maintained.
  4. Bore the new axle gear to 0.146" to press on #3 axle. Mount with epoxy and wipe off all excess fully or axle will not run true in box. It goes on #3 axle.
  5. Bore gearbox axle slots to 0.148" to run axle.
  6. Measure input shaft length required, roughen and use epoxy to mount U-joint cup.
  7. Measure motor shaft required and cut, roughen, and mount U-Joint ball.
  8. Build gearbox carefully following NWSL instructions.
  9. Re-quarter axles carefully after mounting gear to #3 axle. Slide axle into gearbox and cap.
  10. Slot plastic axle retention floor carefully to clear only the gearbox cap.
  11. Remember the frame halves must always remain electrically isolated to prevent shorts.
  12. Scribe all cut lines on frame halves.

Milling

  1. Use a 1/2" endmill for motor recess. Cut this area first as factory motor boss is in the way.
  2. Verify your unit’s frame measurements against mine.
  3. Use Parallel plate under axle base edge of frame in vise.
  4. Clamp with a ½ x ½" x 2" piece of keystock along outside of axle/spring boss, with wider portion of frame above vise jaws.
  5. Ensure frame wider mid lip is dead straight level. Tap down tightly.
  6. The 0.626" depth of the recess is measured from the center of the rear axle on my unit. This depth barely started removing material from the visible curve of the boiler belly. Both frame halves must be cut equally.
  7. If a larger recess depth is required for other motors, use a ball end mill and leave all visual belly material intact – just hollow it.
  8. The original front assembly screws and spacer must be retained.
  9. The new rear frame screws will be used to mount the motor wires.
  10. Deburr all cut edges.

 

  1. Use a 3/8" endmill for the gearbox recess.
  2. My frame measured 1.0" from axle center to the frame top edge at the recess.
  3. Carefully measure and scribe the cut line on the frame top surface. This is very important.
  4. Clamp the frame half in the vise by the top surface and the axle boss bottom surface. Be extremely sure that the scribe lines are safely above the vise jaw.
  5. Ensure the frame is dead straight level in all directions. Use a dial indicator on a fixture arm in the collet.
  6. Cut to the 0.046" depth full frame height. Ensure the width is centered on the axle centerline.
  7. Then cut the extra depth area. The cutter radius forces a wider recess area here.
  8. Deburr all cut edges.
  9. Test fit the gearbox by assembling the frame with all spacers. Basically the recess slot was 0.260" at the bottom and 0.334" at the top on mine.

If all fits, assemble unit after proper lube is applied to all gears, axles, linkage, U-Joints and shafts. Re-glue cylinders to frame and attach valvegear.

Epoxy a styrene piece to the frame side to prevent the gearbox from rotating if required.

I mounted the motor with (2) 0.75" x 0.030" x 0.188" styrene strips under the case ends and RTV in the middle (only) to isolate vibrations. A mount could be fabricated, but the frames must be insulated carefully.

If the axle shafts are needed due to cracking or warping, Use DELRIN and turn 0.263" rods to 0.148" diameter, and bore the ends 0.077" to a depth of 0.15" to press onto the wheel studs. I replaced all four of mine.

I do not recommend it, BUT a good drill press and new cutters might be used to mill the frame. Shallow cuts are required. Only if the quill is very tight and sturdy. The depth of cut will be very difficult to control tho.

If all else fails, contact:

  • I will do the milling and assembly of your parts for $40.00
  • Fortress Group
  • mcanson@polarcomm.com
  • Box 74
  • Arvilla, ND 58214
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