Page Updated 1/12/2005

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For more information on Kadee Couplers, see Knuckle Couplers


By Roger Hensley

There are times when you look at an old Tyco train set car and realize that with a few changes it can fill a need for a prototype car that is just not available in any of the modern kit or R-T-R cars. The same may be said for many of the old AHM, Life-Like, Model Power and Bachmann rolling stock or cabooses. Some people would never consider changing the couplers and trucks or modifying a train set car, but I do when I see possibilities.

Some Conversion Tools At this time, I will only consider trucks and coupler changes and replacement. Indeed, think of this as a general guide and not specific for all cars (impossible). For this example, I suggest Athearn Bettendorf or Roller Bearing (the old fixed bearing) trucks as they are readily available many places, Bettendorf being the best choice for most older cars. You may prefer another manufacturer's truck, but I have found these to be inexpensive, satisfactory and easy to upgrade to metal wheelsets if desired. You will need:
Suggested Parts and Tools List
Athearn Bettendorf Trucks - 140-90400
(or Athearn Roller Bearing Trucks - 140-90399)
Kadee 5's or 58's with coupler box (Coupler Draft Gear Box)
Kadee Coupler Height Gauge 380-205
Kadee .015 washers - 380-208
Kadee .010 washers - 380-209
number #50 drill bit - 947-50 (.70)
2-56 TAP - Walthers 947-1304
pin vise (I prefer the swivel head model)
2-56 x 1/4 screws for both bolsters and Kadee coupler pockets
(1/8 and 3/8 are good to have on hand. Self tapping 2-56 screws are also useful.)
Sheet styrene: .010, .015
Hobby knife
Fine tooth hobby file(s)
Testor's Liquid Plastic Cement with applicator brush.
(Super Glue, too if you wish)
Assorted leftover sprue strips from various plastic model kits.
Assorted small dowel pieces.
Modeling putty - Testor's, Squadron Green, etc.
A short length of track to test coupler height.

All of this is not necessary, but it sure helps to have it on hand for this and numerous other projects. Note that caboose trucks are generally smaller (shorter) than freight car trucks if you choose to use them.

The old trucks are probably Talgo style, meaning that the coupler is attached to the truck on an arm that moves with the truck. In this change, you will need to add a coupler and coupler pocket to the car body. That is more realistic anyway and while you have the car on the bench, you might as well do it all.

Remove the old truck. Generally this will be done by a gentle side to side motion as you pull the truck away from the body as it is held in place with a tab arrangement. Some other manufacturers use a push pin that will need to be removed.

It is easier to fit the new coupler pocket while the trucks are removed and the bottom of the car is open to you. But first (you knew there would be a 'but first') I suggest setting the car on the new trucks and run it up to the Kadee gauge to get a feel for how the coupler will mate to the gauge. You can check with an already Kadee'd car to see how the floor is in relation to the gauge. If there is no obvious problem, you may proceed.

Place the car upside down in or onto something soft to hold it without damage. If you don't happen to have a car cradle, then use a soft towel to make a nest.

Bolster Holes
sprue fill Fill the hole in the bolster where the old truck snapped in. There are several ways to do this. I have used pieces of sprue left over from a model that happens to fit. In that case, I cut it to length and simply glue it in place with the Testor's. Why Testor's when everyone recommends the latest and greatest something else? Testor's works for me every time. Some of the others don't. (Your mileage may vary.) Do not hurry. Let the glue dry.

wood fill What are other options? A small piece of wooden dowel or plastic rod may be used. For wood, use Super Glue Gel or appropriate contact cement. I am not a fan of Walthers Goo as I have found it to let loose after several years. When setup, file any excess material down flat and smooth. The last option is modeling putty to fill the hole. Let it dry thoroughly and watch for shrinkage. Add more if necessary. When cured, file away any excess.

When the bolster hole is filled, mark the center of the hole and using your pin-vise, drill the pilot hole for the 2-56 screw. Change to the TAP and carefully work the TAP into the hole backing it out periodically to clear the threads. When complete, test fit a 2-56 screw into each of the holes.

Coupler Pockets
Click for larger view Clean any flash off of the coupler box pieces.
Lay the coupler pocket (Draft Gear Box) on the end of the car roughly where it is to be mounted with the small lip over the car end sill. This will tell you how much if any fill material will be necessary to make the pocket level with the end sill. Level is important as it cannot dip either into the car or away for proper coupler alignment. The main part of the box will be the cover. Cut sheet styrene pieces as needed to raise the pocket and bring it to level.

Fill the area with the pieces again using Testor's, and let dry. Mark the center line of the body on the fill. This will guide you in placing the coupler pocket. Place the pocket top on the center line with the lip over the edge of the car's end sill and mark the hole using the raised pocket hole (that will hold the coupler) as a guide. Remove and drill and TAP as with the bolster process above. You will use a 2-56 screw to hold the coupler pocket cover in place when the coupler is installed.

When the hole has been preped, test with a screw and you will be ready to do the same to the other end. Do NOT glue the pockets in place yet. At this time, assemble the Kadee's complete with spring and cover and assemble both the couplers and trucks with their screws. Do not over tighten any of the screws. Test fit everything and then test against the Kadee gauge. If the coupler is slightly low, you can use the Kadee washers between the bolster and the truck to raise the car body. If the coupler is high, you will need to add to the coupler mounting pad that you have made. With everything in place, swing the trucks back and forth and watch for interaction between the wheels and the coupler pocket. Sometimes the wheels will strike the round protrusions on the sides of the coupler pocket. It mat be necessary to cut them off.

When you are satisfied that everything is right, disassemble the trucks and couplers and glue the coupler pocket in place. You may assemble the Kadee complete with spring and cover, put a drop of glue on the coupler box and styrene mounting pad and use the 2-56 screw to hold it all together until it dries. The alternative method is to glue the pocket top in place and then assemble the rest of the coupler with the screw after it has set up. Either is acceptable. Both ends are the same.

Mate! Notes
There may be times when it is necessary to glue the coupler together and glue it on the car, as in some caboose and tank car applications. I suggest gluing the top in place and then gluing the cover, spring and coupler onto the top using the side protrusions. Any glue in the coupler mechanism can ruin your day.

When screwing the trucks to the car, it is well to remember not to get the screw too tight. The common practice is that both trucks should swivel freely with one being a little more loose to allow a slight rocking motion to compensate for track irregularities

I hope that you have found this useful. - Roger

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