Changing Wheel Sets on Rolling Stock

Changing Wheel Sets on Rolling Stock

By Roger Heid


There have been some questions and issues regarding the need to change wheel sets on rolling stock. I will try to give you some general guidelines to shed some light into this. For a starter, I will try to explain why it sometimes becomes necessary to change the wheels.

Here is one reason. Rolling stock that is designed to be used on an AC 3-rail track system typically comes with wheels that are made of all metal which includes the axles. Maerklin products are an example. On that track system, the outer rails are of the same polarity. The center rail or studs provide the other polarity, thus requiring the need of a pickup shoe.

So, if you happen to choose a Maerklin made piece of rolling stock, but your track system is of the DC 2-rail type, you are out of luck. On a DC 2-rail system, there is no center track. One side of the track carries one polarity, the other side provides the other polarity, namely Plus (+) and Minus (-). Since the wheel axles on this Maerklin car are made of metal, conducting electricity, this Maerklin car will cause a short circuit, making train operation virtually impossible. You need to buy a complete DC wheel set from Maerklin.

For obvious reasons, the axles of a DC wheel set are made of non-conducting materials. You can see the difference now. I just explained one reason why wheel sets need to be changed. But wait, there is more to it. This replacement wheel set you have to buy from Maerklin, not from Roco, for example.

Roco wheel sets are not interchangeable with Maerklin wheel sets and vice versa. There is a difference in physical measurements between the two. Maerklin offers DC wheel sets, Roco offers AC wheel sets. This holds true for most manufactures.

Let me explain further. Not all wheels are the same. There are variations in wheel diameters and flange diameters. The difference in flange diameter can cause problems on certain track brands and types, especially on turn outs. Confusing? You bet.

Let us do this step by step. If the wheel diameter of the chosen replacement set differs too much from the original, you will wind up with coupler height problems. I think this explains itself. All manufactures offer wheel sets of varying configurations, such as diameters. Beware!

Now, if your track system is of the Maerklin AC 3-rail ilk, and you fall in love with a Roco product, you will not run into an electrical problem. However, your new car may derail on a turn out, caused by an adverse difference in the wheel configuration. In this case, you need to get an AC wheel set from Roco. That will solve the problem, most likely.

Now, if you pursue the DC 2-rail world, you may possibly run into some additional problems, so I understand. Not all brands and types of 2-rail tracks are equal. Being a Maerklin user, I am not so familiar with all the differences and codes inherent to 2-rail track systems. These issues would have to be dealt with by the DC 2-rail gurus.

Here is one more thing. I have a nice digital read-out caliper assisting me in solving some problems I had run into. My rolling stock consists of several different makes, not all Maerklin. That’s why I am aware of these situations.

I hope that this short blog will be expanded by the grace and virtue of comments left by other knowledgeable railroad fans.





One Response to Changing Wheel Sets on Rolling Stock

  1. Ernest Robl says:

    There are several other reasons for changing wheelsets.

    Some early HO models (even by the major manufacturers) were made with wheels with deep flanges. These worked okay on the then common code 100 (2.5mm) or heavier model rail, but these flanges can be a problem on more prototypical code 83 rail.

    Also some models were or are delivered with plastic wheelsets. These plastic wheels, even if they conform to more contemporary standards, are both subject to wear and accumulate dirt much more than metal wheels.

    I have a number of Kleinbahn and Klein Modellbahn cars that were originally delivered with plastic wheels. These have been replaced with metal wheelsets, either from these manufacturers or from Roco (these work just fine).

    Also Kibri offers kits of freight cars and track maintenance equipment with plastic wheelsets. Kibri instructions already include the numbers of the appropriate Roco metal wheels for either DC or AC use. Even if you don’t plan to run these models, the metal wheels look better.

    And, these do run much better with the metal wheels.

    As Roger noted, wheelsets come in various sizes and you need to select the appropriate replacement size for the wheels to look correct and for the couplers to be at the correct height.

    – Ernest

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