Many model railroaders have older model rolling stock from Tyco, AHM, older Riverossi, and the list goes on. Most, if not all, have the snap-in style trucks which present several problems to the modeler. Truck mounted coupler boxes (instead of body mounted), mis-aligned couplers and sagging/floppy couplers are just few of these problems. See fig 1.
Figure 1 Car bolster when the snap-in truck has been removedTo replace snap-on trucks with screw-mounted
ones, you may need to rebuild the car’s truck bolsters to accept screws. This is accomplished by inserting styrene
tubing, gluing the tubing in place, and drilling and tapping a screw hole in the tubing.
Evergreen Scale Models sells styrene parts for the model railroader including tubing of various diameters. Take a look at their tubing chart and you'll see that they produce a 1/8" diameter tube that is exactly what is needed. The inside diameter of their 1/8” tubing is slightly smaller than the clearance diameter of a 2-56 screw.So to prepare the bolster for the tubing enlarge the opening by drilling it out with a 1/8" drill bit. Do not use a power drill!! Do it by hand. Then glue a small piece of 1/8” tubing into the hole using a plastic glue such as Testors tube of model glue or Plastruct Plastic Weld (work with these in a ventilated area). The author has also used Testors Plastic Cement with great succcess. See fig 2.
Figure 2 Testors Plastic Cement
Once the glue has set (let it set according to the manufacturer's instructions), how to remove the excess tubing is up to the reader. You could use flush-cut sprue cutters but the author has found that sometimes these crush the tubing. He recommends you use a flush cutting saw such as a razor saw. Small versions of these can be found that are relatively inexpensive. Do not use a hacksaw. It will ruin the bolster.
After sanding it smooth and even with the bolster, drill and tap it with a no. 50 tap set. KaDee makes a set (#246) containing all three components. See fig 3. You can then replace the snap-on trucks with new trucks attached with 2-56 screws.
Figure 3 Kadee #246 Drill & Tap Set for 2-56 Screws
If the hole the plastic pins snapped into is already larger than 1/8”, you’ll have to do the same sort of thing, but in two steps. Drill the hole out with a 3/16” bit, glue in a piece of 3/16” tubing, then glue a piece of 1/8” tubing inside of that. Then, drill and tap as before. See fig 4.
Figure 4 Completed bolster with 3/16 and 1/8" tubing before drill and tap
Note: This brings up an important point. The tubing made by Evergreen is designed to telescope into the next even or odd larger size. Read the note at the bottom of the chart in the Evergreen link given above.
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I have found the old sprue from plastic model kits can be used to fill the bolster hole.
ReplyDeleteAgreed that sprues can be made to work but there are two things you have to be very careful of. First, you have to have the proper diameter sprue to fit snugly in the opening which can be difficult to find. Second, since the sprue occupies the entire opening, you must be very careful that you drill the screw opening in the exact center of the bolster. This can be more difficult than you would think. It's weird to see crooked cars rolling down the track.
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