Upgrading a TYCO F unit with an Athearn BB drive

The subject of replacing a TYCO F unit drive and chassis with an Athearn Blue Box drive and chassis was is the topic of this post.
It is actually quite easy. The only thing that poses any difficulty is the potential interference with the shells inside support pieces for the various TYCO shell types. TYCO went through several variations (most likely different manufacturers) . Four example shells are shown below:
The support plastic surfaces are shown in the picture, particularly in the bottom two shells. These need to be carefully cut out so as to not damage the shell. They will not need to be flush with the other surface, but reduced down to the point where they will no longer interfere with the fit or function of the drive. For comparison. A typical Athearn shell is shown in the picture below.
A second difference between the shells is in the coupler areas. The Athearn Units have chassis mounted coupler pockets on both ends and the TYCO (and old Life Like) units have shell mounted in the front (pilot) and truck mounted in the rear. This can be handled in a couple of ways, depending on the condition of the TYCO shell that you going to use.

To use the Athearn chassis as is, there needs to be some significant work done to the shell to provide the clearance for the coupler pocket. This is difficult to do and will likely require some additional paint touch up.
A second option is to modify the Athearn chassis. A modified typical blue box chassis is shown in the picture below.
A common practice for modifying Athearn units (with metal couplers) to DCC is to cut off the chassis mounted coupler pockets, mounting the couplers on the shell. I believe this is done to reduce the electric short potential between a metal coupler and chassis.
In our case cutting the front coupler pocket off will maintain the integrity of the chassis and clear the interference with the TYCO front mounted coupler.

The TYCO engine that I’m modifying is shown in the next few pictures.

The shell is in good shape, but the metal parts on the drive have spent too long in a very moist environment. I find these old locos in flea markets and garage sales and they all suffer from this problem, such a pity.
As it happens this is one of the last TYCO units that were made and the process to get it apart is different from the earlier ones. In this case the weight was held in by pure friction when the plastic clips are snapped in place. Pry them open and the weight falls out. I guess this is why I find some many without weights.
As shown in the pictures, the two trucks are held with plastic tabs in eyes on the shell. This is the more typical TYCO construction technique.

The power truck can be removed by using a small screw driver to slip between the shell side and the tab on one side. Gently pry the attachment apart. The power truck will rotate out of the shell. Gentle pressure is all that is required.

The front truck is a little more difficult. It is held in place with a plastic bar with tabs that fit in either side of the shell. Gently spread the shell sides apart as close to the bar tabs as you can. Hold the bar flush on one side so the other side comes free of the eye. Then rotate the truck and bar out of the shell, as shown in the picture below.
The final part of the disassembly process is to cut the front light assembly wires from each truck. If you plan on using these trucks later, you should leave some small length of this wire on the truck so a wire can be splice on to it for the next application. The light assembly can remain in the shell because it will not interfere with the Athearn drive. (Removing the coupler box from the Athearn chassis has also removed the Athearn light support.) If you want a conventional light, this assembly is an option.

The yellow wire in the picture will attach directly to the chassis and the black wire will attach to the top of the front Athearn truck. This will require some soldering to provide the proper connections.

The actual Athearn chassis that was used is shown below. Note the coupler pocket has been removed from both ends of the chassis.
As with the TYCO unit, I get these at various places and this is a common condition for these used chassis. If the rear couple pocket was in place, the shell would need to be trimmed for a proper fit. With the chassis in this condition the shell does not need to be trimmed. Instead a coupler pocket will need to be mounted to the shell. I’ll discuss that in another paragraph. This chassis is a powered unit chassis. You can tell that by the shiny metal strip between the motor mounting holes on the top of the chassis. additionally, the truck mounts on the bottom of the chassis are also shinny metal. In the manufacturing process, all the chassis were painted over the whole surface. Then the ones that were going to be used for powered units were additionally worked to establishing these electrical contact points. If you have a non powered chassis, you will need to create these contacts either in a manner similar to shown in these pictures or by soldering wires to the trucks like you would if you were modifying the drive from DC to DCC. The DC to DCC configuration is not part of this discussion, so I will not include it here.

The initial assembly checks of the shell and the chassis are shown in the next picture.
Note the tabs on the chassis are pushing the shell apart on each side. This TYCO chassis does not have the eyes opened for the tabs. These eyes are part of the details that are molded in this TYCO shell. In older versions, these eyes were used to hold the weight. In that case all three would be open already (not shown). The center detail (eye) on each side approximately line up with the tabs from the chassis. The eye may need to be elongated to ensure a proper fit. For this shell I used a small drill and file to open an eye in the detail to catch with the tab. This opening is shown in the picture below.
This will likely leave some roughness around the eye as highlighted in the pix. When the shell is on the chassis this roughness is not noticeable.

The last thing that needs to be done is the rear coupler pocket. The shell is not thick enough to just attach the coupler pocket directly to it. A larger surface to attach the pocket needs to be built up inside the shell. This new surface should be flush with the bottom edge of the shell where the pocket will be placed. I do this by gluing a few plastic shims to the surface. Do this until attachment surface is more than half of the coupler pocket length. After the glue dries, you can attach the pocket with a screw or just glue it on, as shown in the next picture. The bonding from the glued surface will be more than enough for the trains you will pull. This picture shows a Kadee coupler, the process will be the same for any coupler system.
The assembled Athearn chassis with a working motor and power trucks is shown in the following two pictures.
The first shows the bottom of this drive system. Here you can see that I have used the more recent screw type motor mounts. These are the best mounts to use on Athearn locos. The old style rubbery type mounts would become brittle with age and heat. They would then break apart and the loco would be useless. These new mounts are more robust.

As seen from above, this is a typical Athearn blue box DC loco system. The strap needs some additional work to remove the rust and improve the electrical conductivity. A second option here would be to wire it for DC with the anticipation of using DCC. The wire strap would be eliminated and the top of the two trucks would be wired to the top of the motor. For best performance the trucks need to be completely cleaned and properly lubricated. again, this is the subject of another post.

The mated TYCO shell with the Athearn blue box drive is shown in the next two pictures.
More work needs to be done on the shell because it is missing its horns. In addition it could be stripped and painted for the road of your choice.

The task at hand has been accomplished. The TYCO shell has been fitted with an Athearn BB drive and will perform admirably in a DC layout.

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