HO Projects 2026

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Assembling MDC 36' Old Time Cars

Part 2: Couplers & Trucks

1.  Couplers

a. De-burring the Mounting Post
coupler1

Use the 5/64 drill bit and drill the hole all the way through the post.

Then use the Dremel with bit 9905 and lightly chamfer the opening. 		coupler2

The hole is slightly indented after chamfering.

b. Cleaning Up the Chassis End
coupler3

Use a flat needle file and remove the flash around the outside of the coupler pocket and the end of the underframe. 		coupler15

A razor knife can also be used. Mine has a dull blade.
coupler16

Use the flat file to smooth the top of the mounting post. 		coupler14

Top of post should be shiney and smooth. Remove the sharp edge at the front of the pocket. After cleaning up, it should look shiney.
coupler17 The last step is to clean up the inside of the pocket. Use the flat file and remove any flash or burrs. Also do around the outside of the post. The underframe shown here has not had the end cleaned up.

c. Covers and Screws
coupler18

A variety of pocket covers:
  • plastic with detail, offset hole
  • plastic with center hole
  • metal with center hole
 coupler9

Kits may have a variety of screws:
  • .170 x 2-56 thread
  • .170 coarse thread
  • .110 coarse thread
I could not get the short screw to thread in when I de-burred the coupler post. The issue with the longer coarse thread screw is that it tends to want to tilt when threading in. De-burring helps some, but care has to be used when threading it in.

The mounting post can be drilled out and tapped for a 2-56 screw like the bolster. Be sure and use a panhead screw and not a flathead. The flathead will not have a good look due to the inverted head protruding.

d. Coupler Cover Issues
coupler10

The offset plastic cover doesn't fit well. 		coupler11

The center hole style fits well.
coupler12

An issue with the plastic covers is that they can be over tightened causing them to bend or crack. 		coupler13

Shown is long coarse screw which has bottomed out in the hole. It can't be tightened enough to hold the cover in place. This is why the hole is drilled out first.

e. Plastic Coupler Cover Helps
coupler14 coupler15
coupler16 coupler17
To keep the plastic cover from spinning, cut a piece of .040 x .060 styrene strip to .250 (1/4"). Fit it in the coupler pocket. Next, place a bit of styrene cement on the top edge and then install the cover. Wait for a minute or two, remove the cover, and put more cement on the inside where the styrene sets on the cover (shown with arrow).
coupler18 coupler19
If the plastic cover cracks, open up the ends and put a small amount of styrene cement on the edges with a toothpick. I don't like liquid cement as it doesn't have good strength. Clamp the cover in a flat clamp to make sure it is flat while drying.

2.  Trucks
truck1 I found two styles of trucks in the kits:

LEFT--the thickness of the ring around the mounting hole is thick.

RIGHT--the ring is thin. These trucks have Kadee 33" ribbed back wheels installed. The advantage over the stock wheels is that the wheel gauge is fixed, where as with the stock wheelsets the gauge and centering can be disturbed.
I used two methods for mounting the trucks:
de-burring for the long coarse screw and tapping for a 2-56 screw.

a. Using the Coarse Screw
truck1a Use the 5/64 drill bit to drill out the hole. Then use the Dremel and the 9055 bit and lightly chamfer the top of the hole as was done on the coupler pocket. Put the screw into the truck and set the truck on top of the bolster. Installing the truck in this fashion allows the screw to be guided by the truck hole.
truck2 truck3

b. Using a 2-56 Screw
truck4 truck5
truck6 truck7
Drill out the hole with a .055 drill bit (2-56 tap drill). Thread the hole with a 2-56 tap. Use the included fine thread screw or a 2-56 x 1/4" (or longer) screw. If the screw is a bit loose on final assembly, place a dab of styrene cement in the bolster hole.
HO Projects 2026

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