Category Archives: Repair techniques

AHM Rivarossi C-Liner tune up

A common engine type from the 1980’s and 90’s is the Rivarossi based C-liner. These were initially imported into the US by AHM. Subsequently by IHC. When IHC and Rivarossi had a falling out, the manufacture went to Mehano. These were basically clones of the Rivarossi design, with some minor design changes.

A typical version of this engine is shown in the following figure:

The drives have two basic configurations. These are shown in the following figures:


A key difference is the attachment of the front truck. The Rivarossi version had the truck held on with a bolt. In this case, the electric power was picked up from one side of that truck and the other side of the rear truck. This allows the bolt to carry the appropriate connection. Drives with this configuration have few problems with the electrical circuit to the motor.

The later versions have the truck with a plastic tube with tabs that is molded on the truck. The tube is has a hole in it. the track power is picked up on either side of this truck. The wires carrying the power are brought through this hole.

A common problem with this second variation is the tabs or tube break off and the wires easily break free, eliminating the power connection. This problem is significant. The solution will be discussed in a later edit of this post.

Both versions have essentially the same Rivarossi style motor.

Later versions of other engine models used a smaller motor with a similar installation. The techniques discussed here apply to those engines as well.

The power truck is held in place with screws on the Rivarossi version and with a metal rod on the AHM version. To clean the motor area it is best to remove the power truck. To do this remove the wire connections by disconnecting the spring that holds the brushes. The spring is a critical part, so be careful to not lose it or the plastic tube that covers one side. Then remove the brushes and metal clips. Handle the metal clips carefully, because the solder sometimes will break easily. Pay attention to how these connections were made so they will be put back the same way when reassembling.

The screw removal on the Rivarossi version is straight forward. The rod removal requires a little thought. You can see the rod on either side of the chassis. To get it started you need to push from one side with a small diameter screw driver or other tool. Push the rod out from one side so it can be pulled with a set of pliers from the other side. See the next figures:

The most common complaint is that these engine make a very loud growl and tend to smell during operation. Likely caused by electrical arching occurring where the brushes contact the communicator. This is a result of a build up of dirt and crud on both surfaces. This is shown in the following figure:

The crud and smell is usually from too much lubrication in the wrong places. The only spots on the upper part of the engine that need any lubrication are the bearings that hold the rotor. These are shown in the following figure:

A very small amount of Lebelle quality oil is all that is needed. A little on a small artist brush would do the job.

The most important step is to clean the communicator and brushes. The communicator needs to be brass colored and shiny. The brushes also need to be cleaned as well. These brushes are metal colored and will also tend to shine. The trick is to maintain the curvature that has been formed in the brushes.

For these motors, when the brushes get worn down the metal support will cause an arcing with the communicator. This will the system short out and not run. So short brushes need to be replaced.

The circuit design requires that the electrical continuity be provided with wipers and metal pieces held together against a post with a spring. These parts corrode and add resistance to the circuit. Typical condition of these parts is shown in the following figure:

As earlier, where these parts touch, they should be clean and shiny where they touch, as shown in the following figure:

The next step is to clean and lubricate the trucks. The truck bottom covers are held in place with either screws or bolt and nuts. The later versions are held with screws. The earlier versions have one or two bolt-nut combinations. The bolt option is shown in the following figure:

What the designers were thinking when they insisted in using the bolt-nut attachment is not clear. The nut notoriously gets lost. When I get one of these I glue the nut in place before removing the bolt.

After the glue dries, the bolt can be removed. Remove the screws and the truck bottom cover readily comes off. As shown in the next picture:

The first thing to do here is to remove the wheels and gears and clean everything. This includes the vertical wipers that are the electrical contact with the wheel. Frequently these wipers and the back of the wheels have a build up of crud. They also will suffer from the fretting caused by passing current through different metals. This coating needs to be periodically removed. So it must be done as part of this tune up.

At this time replace all the traction tires. As the tires age the get brittle and absorb some of the track gunk. They lose their grip and they break and are missing. Both are bad for performance.

Then reinstall the wheels and gears. Lightly oil the bearing surfaces and the gears. Normally gears would require grease, but for HO models the grease friction is too much. A small amount of oil is enough.

Before replacing the truck bottoms the couplers need to be brought up to the desired integrity. Techniques to do this will be part of a future update of this post.

Reattach the truck bottoms.

The final step is to apply some vibration absorbing tape to the outside of the chassis as shown in the following figure:
Note that the rod hole has been covered. I find the rod can come loose at shell removal for no apparent reason causing a lot of headaches. This helps dampen the vibration and eliminate the stray rod problem.

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The results of this kind of tune up are shown in the following figure:

PC2 is defined in the performance criteria post. Clearly all three engines in this test set show appreciable improvement. The efficiency is a relative change. The efficiency equation was used, but the maximum draw bar force was used instead of the actual point force. Thus it is representing change. As such it shows a good benefit.

All critical parameters made positive movements. The draw bar force increase and the noise reduction were the most significant.