When the can motor came on the seen it changed everything for the hobbyist. This was especially true for the Brass Steam Locomotive enthusiasts. He or She now had a real work horse of a motor that could drive a locomotive with ease.
There are other aspects of the drive mechanism aboard the Brass Steam Locomotive that cause the user difficulty. However, in this case we are going to concentrate on the can motor and what it can do for you.
Can motors come in a variety of sizes and rpm (Revolutions Per Minute) ratings. Also, torque values plays an important part in the choosing of a can motor. Generally can motors range from about 5k Rpms to as high as 17k rpms. For example a very small motor that would fit in a HO 0-6-0 switch engine with a rating of 16k rpms would not have a very good torque value. An example is a coil wound motor becomes very powerful as you increase the coil wrap on the motor. Inversely, by removing coils from a motor will make the motor very fast but not ideal for pulling anything. Thus the very small can motor does not have the power of the larger can motors.
This can be compensated for because most can motors will fit in just about any HO steam engine. If the engine is small like a 0-6-0 switch engine you can find a motor that fits nicely in the range of 5k rpms to 12.5k rpms and use a high speed gear box at either 27:1 or 28:1 gear ratio. My wife and I usually stay away from the low geared gearboxes because they run way to slow for our liking. However, you may like that type of operation and would prefer the 36:1 to 37:1 gear ratio.
You are not looking for high speed with a locomotive but for speed and especially power to pull a large freight train or passenger train. This is also essential with the small switch engines ability to work a yard shuffling freight cars around. When I had slot cars I would unwind the coils on the motor. This made the slot car very fast. This is not what we are trying to do with a steam locomotive.
Depending on the size and type of steam locomotive will determine in most cases the size of can motor you are looking for. The beauty of a can motor is it will run at extremely low speeds yet will give you the power and speed to replicate a real steam locomotive based on scale.
If I were rebuilding a 4-8-4 Northern I would be looking for speed. They were high steppers and would cruse at over 100 mph. The ideal motor would be a 16k rmp motor with a 27:1 or 28:1 gearbox. This would be true for many engines including the large articulated locomotives. However, a Union Pacific Bull Moose 2-8-8-0 was a very slow and deliberate locomotive and had great pulling power at low speeds. This is known as tracktive effort. This locomotive would be best suited with a 12.5k rpm can motor and a 28:1 gearbox or 36:1 gearbox depending upon the likes of the hobbyist as far as speed is concerned.
The key to all of this is there are different can motors that will meet your needs and definitely improve your steam engines performance and please you as a hobbyist.
Joy Ball has been involved in the restoration and maintenance of a variety of Brass Model Locomotives. Through her years of expertise, Mrs. Ball has perfected the art of train restoration often spending countless hours preserving vintage Brass Locomotive to the running condition of even the newest Brass Model Replicas. It should be noted that the above article was written by Joy