Home  ·   Reference  ·   Roster   ·   Photos   ·  Inventory   ·   Contact us   ·   Links



Radio Control Installation in an Aster Mikado


by using computer-controlled R/C equipment!

by Ross Schlabach



Equipping live steam locomotives with R/C gear adds a new dimension to the operation of these models and reduces the need to chase them around the track. This can be especially advantageous on ground level railroads. But with the convenience R/C brings, it also creates some distinct challenges. Most live steam locomotives were not designed with any consideration for the installation of R/C gear. This is a total reversal from model airplanes where R/C installation is an integral part of the design. With live steam locomotives, we are forced to work around back head layouts, tender configurations, and the method of firing.


Before we launch into an R/C installation, there’s an important regulatory issue to address. Radio control, or R/C, equipment is available in a number of frequencies under rules updated by the FCC in 1991. Generally speaking, modern R/C model operation is done using radios operating on either 72 megahertz or 75 megahertz. For licensed ham operators only, there are also frequencies available on 50 & 53 megahertz. The 72 megahertz range is for the exclusive use of flying models and should not be used on trains or other surface type models. Our frequency band for ground-based models like trains is 75 megahertz, and this is what you should look for when you go to purchase your R/C gear.


An important choice in R/C equipment is the type of modulation that the radio uses. R/C transmitters are made to operate on AM or FM. Equipment operating on AM is generally more subject to interference than gear using FM. There is also a subset of FM called PCM, or Pulse Code Modulation. PCM gear is normally of the highest quality (read: expensive) and it is the pulse code modulation feature that provides additional protection against interference. With our trains, we are operating equipment that generates a large amount of radio noise from metal-to-metal contact and even gas burner noise.


This noise can cause glitching which makes servos jump around rather than hold their intended positions. There is no guarantee that FM or even PCM-FM gear will completely eliminate that noise (and therefore glitching), but FM radio sets can provide better protection against interference and this is what I recommend -- with a PCM set being the best choice if you can find what you need – and can afford it. All this being said, I’m aware of some engineers using AM radios with few if any glitching problems. So take any opportunity to talk with people using different types of R/C equipment and learn what works best for them – it might work for you, too!


To get equipment that will give you the best capabilities and the most flexibility, you can purchase transmitters designed for model aircraft operation and have them retuned for ground frequency operation. JR will gladly retune many of their aircraft radio sets to the 75 MHz we need, and its probably best to order the equipment new and have them retune it before delivery – the additional cost is negligible. 


For years, live steam modelers have used R/C gear to equip their locomotives, but there has been little effort expended to take advantage of the modern-day capabilities of today’s computer operated R/C transmitters. Instead, modelers used inexpensive AM radios and equipped their locomotives in the simplest fashion – sometimes requiring them to constantly hold a control stick to one side to get the locomotive to run. With modern day equipment, you can set it and forget it.


As an example, it is possible to equip a locomotive with R/C control of throttle, blower, and drain cocks, and have the transmitter orchestrate the operation of each through the operation of only one control stick -- using channel mixing and a feature called offset. This simplifies locomotive operation while greatly improving the running process. Another feature of modern day R/C transmitters is that many of them can accommodate settings for more than one engine – in some cases up to 10 different models. I had over 15 years’ experience in using these features on both R/C helicopters and planes, so I was ready to take advantage of these special features on my trains.


There’s one last warning I need to give you before I jump into the details of an R/C installation in an Aster Southern Mikado. Make sure that you have already operated the locomotive and that it runs properly before you tackle an R/C installation. You simplify the job by knowing you already have a smooth running engine.  If you encounter subsequent problems with the R/C equipped locomotive, you will be reasonably certain that the problems are limited to your R/C installation and not some underlying mechanical troubles.


Now, let’s look at an R/C installation on the Aster Mike. In equipping the Mikado with R/C gear, I was faced with a couple of decisions. Was I going to try to incorporate servo control of the reverser; and was I going to equip the blower with servo control? Reversers come in two basic configurations: screw-type and lever. The lever system is much easier for implementing an R/C installation, but you may still encounter some problems. Space is usually a bigger problem in equipping the reverser for R/C control.


The second but maybe more important issue is radio glitching. With any R/C installation in a live steam locomotive, the risk of glitching is magnified by the radio interference created by metal-to-metal contact. Since engines respond slowly to steam throttle changes, the effects of glitching on throttle operation are normally unnoticeable. But if the reverser channel glitches, the steam supply to cylinders can be cut off instantly and the drivers screech to a halt – possibly causing a derailment.


There are “glitch buster” circuits you can buy that slow down servo response and thereby eliminate most of the effects of glitching, but I did not want to add another component to my installation. So, I decided to leave the reverser – and the glitch buster -- out of my R/C installation. Since I do very little switching and the installation was going to be a real squeeze anyway, leaving this out was really a “no-brainer”. The blower, however, was another matter.


On alcohol-fired locomotives, the blower is an integral part of the engine’s operation. At any time the engine is stopped, the blower must be turned on to maintain proper draft for the fire. Failure to activate the blower can result in the fire going out or the flames working their way around the bottom edge of the firebox in a desperate search for oxygen. This latter tendency is a characteristic of the Mike, and these flames can easily find their way into the cab with destructive results – especially to unprotected R/C gear. And I have melted servos as proof of this claim. So my installation was going to incorporate blower control – with the special plus of a Bangham whistle!


The first challenge was where to locate the radio gear. I decided the tender bunker was ideal since it would protect the sensitive receiver and battery from heat. I chose to install a very small, 7 channel FM airplane receiver that was factory re-tuned from 72 mHz to a 75 mHz ground frequency. Seven channels sounds like too many but this is what gives you the mixing capabilities. Before this causes you to stop reading, it is possible to do this specific installation with a simple four-channel radio, but I want to give you some idea of the full capabilities of modern day R/C equipment.




Back to the tender installation. The way I install receivers and batteries is to attach them to the underside of a false coal load. (See photo) The “floor” for the coal load can be made of lite plywood on feet to provide a space under the coal load for the R/C gear. The top of the coal load is made with a thick layer of soft balsa. The balsa can be carved into a nice coal load shape, covered with glue, and sprinkled with “coal” for a prototype appearance. This coal load can also be used to disguise the antenna. I normally use base-loaded antennas to do away with the long antenna wire.

The item at the bottom of the picture is the base-loaded antenna.

These can be purchased at hobby shops and are frequently used on R/C cars or helicopters. The base-loaded antenna is short enough to fit into the balsa block that forms the shape of the coal load. It is important to remember to put the antenna as far away from noise sources as possible. This means high in the coal load – above the metal sides of the tender. FM needs a clear “line of sight” from the transmitter to the antenna, so you don’t want to bury the antenna deep inside the tender or cab! (Recent experience suggests that AM gear – despite its reputation for lower tolerance to radio interference – may allow you more latitude on the placement of antenna.) The receiver is attached to the underside of the coal load with double-sided tape – also available at hobby shops. Then the battery is attached too using Velcro so that it can easily be removed for recharging.


For simplicity sake and to eliminate another possible radio interference source, I omit the ON/OFF switch between the battery and receiver and control power to the receiver just by unplugging the battery connection. Use the switch if you wish and have the space to do so. There is another reason I attach my radio gear onto the underside of the coal load and not just lay it in the coal bunker space. If you do the latter and then spill alcohol (or water) during a fueling stop, you could short out the radio – and probably start a fire in the process! With my setup, the radio/coal assembly is removed and well clear of any hazard.


Another issue to remember in designing the tender radio installation is to provide adequate access for servo wires to reach from the cab. Either position the receiver so that the servo leads reach, or purchase servo extensions for use in those situations where you have to put your radio gear all the way in the back of the tender or have a long reach to the cab. In every installation, you want to have servo, battery and On/Off switch leads as short and as neat as possible since they can interfere with antenna reception if they are in close proximity to the antenna. 


Installation of servos in the cab comes next. When I equip a locomotive for R/C operation, I try to make the installation as “non-invasive” as possible. I don’t drill extra holes if I can avoid it, and I make my R/C connections so that they can be easily disconnected for manual operation. I’d hate to travel many miles to a steam-up and not be able to run my engine due to some kind of R/C equipment failure. The “non-invasive” installation allows you to still be able to operate your locomotive if the radio gear fails or batteries die – and it doesn’t deface the engine.


I wanted control for throttle, blower, and whistle, so I needed three servos. When selecting servos, there are competing concerns. Larger servos may be more powerful and more immune to heat in the cab, but in most cases there is not much excess space for these bigger servos. I have used smaller Futaba and HiTec brand servos with good results over the last two years but I try to keep them away from heat sources – if possible.


Also keep in mind that individual controls on locomotives may require more or less servo power, and this changes from engine to engine. If you have problems moving a reverser lever, then don’t expect a small servo to do that same job. Look for a more powerful servo, and by all means try to reduce the drag or other mechanical interference in that control linkage.


The throttle, blower, and whistle all required very little force with the whistle control needing the least of the bunch. I used two Futaba servos with about 28 oz. of torque each to operate the throttle and blower – and even this was overkill. Servos with 15-20 oz. of torque should have been fine; but the ones I used were compact – and more importantly my hobby dealer had them in stock! The whistle was operated with a servo only providing about 10 oz. of torque. 

The blue object is the small whistle servo.  It is attached to the cab roof with double sided tape.


Look at the picture of the cab interior, and you will see that the throttle and blower servos were mounted vertically on a brass plate that allowed them to sit on either side of the water glass. I made the plate especially to fit around the water glass and the bottom of the plate was an “L” shape that attached to the cab floor using existing cab mounting screws and holes.


The whistle servo was entirely a different challenge. The Bangham whistle uses a valve actuator mounted on the left side of the boiler. Operation of its actuator arm would require a pulling motion on a wire “cord” that could feed from the arm back through a hole (or window) in the front of the cab to the servo arm. This dictated that the servo be attached to the inside of the cab roof. I attached the miniature servo to the cab roof with double-sided servo tape. I must admit this has only been modestly successful since heat sometimes causes the tape to lose its grip – costing me the use of the whistle for the rest of the run. When the cab cools, the tape regains its adhesive power and servo operation returns to normal. So far, this has only been a Summer issue since the cab is much cooler during winter operations.


It would be best to permanently attach a small servo mounting bracket to the roof interior but there is not enough clearance for such a bracket. As an alternative, I could epoxy the servo to the roof but then I’d have future problems if the servo ever needed replacement. I’ll probably come up with a better installation for this servo, but for now it is easier to just periodically replace the double-sided tape as its “stick” wears out. And this is consistent with my “non-invasive” approach.


One feature of R/C installation I’m going to gloss over is actually setting up the servo “throws” because this is normally a trial and error process. You work to match up the throws of the servo with the limits of the desired control movement. For instance, you want the “full down” position of the throttle control on the transmitter to position the servo to fully close the locomotive throttle – no more and no less. Suffice it to say that different brands of R/C transmitters have different features for setting control limits.


Computer radios are by far the most flexible in this regard and allow you to set not only the outer limits of a servo’s throw, but you can increase or decrease the total range of movement as well. The manuals that come with the radios generally do a decent job of explaining this part of the installation process. Also, take a look at the two cab photos and you can see the limits of the servo movement and the methods of attaching the linkages. Most of the parts shown are available in a well-equipped hobby shop. Show these pictures to the hobby shop employee and he (she) should be able to help you pick out the parts you will need.


Actual control of the servos is accomplished by the transmitter. With a simple, four channel radio, you can easily operate all three of these controls. But the operation is not as simple and hassle-free as it can be. Here’s an example using some model airplane terms that shouldn’t trip you up. If you use a simple 4 channel radio that is set up in normal model airplane configuration, there are controls for: throttle (up and down on the left stick); rudder (left and right with the left stick); elevator (up and down on the right stick); and aileron (left and right using the right stick). Each of these controls sends signals to a specific channel on the receiver.


Out of these four possible controls on the transmitter (throttle, rudder, aileron, elevator) only one, the throttle, stays where it is put. The other three spring back to the center after you release that stick on the transmitter and the action of the servos match this stick movement. So for our installation, we want our throttle servo connected to the transmitter’s throttle channel and wherever we place the left stick -- up or down -- it will stay put and the actual throttle control in the cab will do likewise.


For the whistle, use the rudder channel and blow the whistle by moving the left-hand stick to the right. The whistle blows until you release the stick. For blower on this simple installation, use either the aileron or the elevator channel. To operate the blower, merely move the right-hand stick in the appropriate direction and the blower would operate as long as the stick was held in position. It is possible to open up the back of the transmitter case and remove one or more of the centering springs so that the stick would not re-center when released, but this the best way to set up your equipment? I think there is a better and more efficient way.


Some functions could be much easier with a computer radio. The throttle and whistle controls will operate the same as in the above example – even in a computer-controlled transmitter. Setup of control throws and limits of movement can easily be set. The operation of the blower can be automatically tied to the throttle, too. By using a feature known as mixing, we can “mix” the operation of the blower with the operation of the throttle so that the blower automatically comes ON any time the throttle is CLOSED. As we slowly open the throttle, mixing will slowly close the blower.


With another radio feature called “Offset” you can set the point where the blower starts to open or close. It may sound complicated, but take a few minutes with your instruction manual to learn how to set the features and once you complete this programming, the blower will always follow those preprogrammed instructions without you having to remember to do anything other than just operate the throttle. This programming means that you can even let your child run your engine and everything will work “automatically”. Of course, the computer transmitter won’t tell him when to close the throttle to prevent a runaway – but that’s something for Mom or Dad to teach them anyway! 


There are also times when we want the blower to be closed even when the throttle is closed – like when you are firing up the engine. And we may want the blower open during the initial movement of the engine to assist with maintaining the draft – regardless of throttle position. These conditions are the only times you need to even think about the blower and these can easily be controlled by a three-way switch on the transmitter (commonly labeled for Flaps or Landing on model aircraft transmitters) to override the normal blower mixing. Leave the switch in position 0 and the blower operates normally with the throttle. Move the switch  to position I and the blower is OPEN regardless of the throttle position; turn the switch to position II the blower stays CLOSED regardless of throttle movement.


Want to put R/C gear in another locomotive? With computer-operated R/C equipment, there are transmitters that can store program settings for 2 or more locomotives. So you don’t have to buy a bunch of transmitters – one for each engine. I have a transmitter that can take settings for 7 different models. This means that as I add locomotives, I only need to buy a receiver and the servos to go in each locomotive. And I can even have engines share batteries! This keeps the cost down, means fewer batteries and transmitters to charge, and there’s less to haul to the track.



Hopefully, I’ve given you an idea of what can be accomplished by bringing together today’s computer R/C technology with our live steam hobby. But I know I’ve just scratched the surface. The manuals that accompany the transmitters have much more detailed information about the operation of different features of the radio equipment. In fact, I’ve probably missed some other features that can be of use too. So there’s lots to learn and lots of enjoyment to be gained from R/C operation of your live steam locomotives. As Nike says, “Just do it”! 



Appreciation for permission to publish this original article on SouthernSteamTrains.com is expressed to Ross Schlabach.




Home    ·    Reference   ·    Roster    ·    Photos    ·   Inventory    ·    Contact us    ·    Links