My first intention was to have everything (battery, receiver and both servos) hidden away in a box on the back of the wagon. Also, as an important requirement, I wanted to modify the existing metalwork as little as possible so as not to loose its value if I removed the RC at some time in the future. Unfortunately, I couldn't devise an easy way of coupling the steering servo to the front axle from there so I ended up mounting it under the body, between the rear wheels. Also, the antenna, in the form of a length of wire, needed to be stretched out to get a useful range. I therefore devised another bit of "load" to look like a long thin box or pile of planks, leaning up against the cab roof. Both of these solutions still require electrical connections into the main box but they are easily concealed.
The choice of RC equipment was easy. I chose the cheapest two channel setup I could find at the time! The next job was to find a suitable dummy load to contain the electronics. My first idea was a cigar box, and a cigar smoking friend promised to save one for me, but that never happened. I was thinking about using my (very poor) woodworking skills to make one from scratch. I decided against that and eventually found a small tea caddy of the ideal size. It also turned out to be a better shape than the cigar box; being roughly cubical instead of flat, it enabled the speed control to be taken through the window in the back of the cab.
The tea caddy was first prepared by sanding off all printed markings and applying a clear varnish to provide a nominal protection from water (always a good idea on a steam engine). I cut a hole in one side to line up with the cab window with the box in its intended position. Unfortunately, this position was changed at a later stage so the hole had to be enlarged and is now more visible than was originally intended. I fitted a plywood floor inside the back of the wagon. This served a dual purpose. Firstly, it provided something to fix the box to, rather than the metalwork. It also covers up the electrical wiring between the box, the antenna and the steering servo under the chassis.. The box is mounted upside down, with the lid fixed to the floor. This means that the innards are easily accessible when the rest of the box is lifted off. Inside are the battery pack, on/off switch, receiver electronics and the servo connected to the engine reversing lever. The latter is not as useful as it sounds because the engine (a single cylinder single acting type) is not self starting. This means that, once stopped, the flywheel must be spun by hand to start it again. Therefore, the engine can't be reversed remotely. However, a degree of speed control is available and, of course, it can be stopped instantly in an emergency. This is useful as, with remote control, the driver can be several yards away.
The linkage between the servo and the reversing lever is not as simple as one would think. Several layouts were tried and rejected before one was found that worked satisfactorily. An interesting and totally unexpected problem occurred right from the start. The original arrangement had a metal rod attached at the front end directly to the reversing lever. When I first tried the servo it immediately went into violent, almost random, vibrations. My first assumption was a loose connection but this was soon disproved when I found that as soon as I touched the rod with a finger, the vibrations almost disappeared. Also, disconnecting it from the lever had the same effect. After much puzzling and experimentation, I came to the conclusion that the rod must be acting as a secondary antenna, the effect of which was randomised by the electrically loose connection to the main chassis through the reversing lever. I could reduce the vibrations somewhat by "earthing" the rod to the chassis with a short length if braid. To stop the effect completely, I had to attach the rod to the lever through a piece of plastic, thus insulating it.
Having solved that problem, I found that the push and pull on the lever at a slight angle caused the cylinder to not seat properly, causing an almost constant steam leak. I tried several ideas to solve this one and, in the end, I connected the lever to a second lever mounted directly behind it. I then connected the control rod to this second lever. This arrangement enabled the action on the main lever to be straight back or forward.
Another problem, which was obvious from the start, was that the control rod could not be permanently fixed at its front end. To get free access to the boiler for filling and firing, the bodywork, including the cab, is hinged at the rear end and can be lifted up clear of the boiler. This, of course, would have been impossible if the control rod had been fixed at both ends. To get round this I fitted the front end of the rod with a U shaped piece, which slipped over the plastic piece (mentioned above).
This arrangement for operation of the reversing lever was clumsy. It worked but it looked all wrong. I later revisited the design and altered it to be much simpler. I fitted a vertical extension to the lever, the extension having the U shaped piece instead of the control rod. The extension was vertically in line with the lever and the control rod was bent at right angles to fit into it. With this layout, there was no tendency to twist the lever as it moved and so there was no need for the second lever and extra linkage. The plastic insulator was attached to the control rod. This arrangement works just as well and is much simpler, looking much less obtrusive.
The next problem was where to mount the steering servo and how to connect it to the front axle. The obvious place to mount the servo was under the boiler right next to the axle. This was totally out of the question for several reasons. Mainly, there wasn't room. Even if I could find a smaller servo, it would have been too visible. Also, that position would probably have been too hot. Therefore, I mounted the servo under the body, between the rear wheels. This solves all the above problems but introduces the one of how to get the motion to the front axle. I did this by means of a pair of light chains. This doesn't look as bad as it seams because steering was often done with chains on this type of vehicle in real life. In order to get a useful swing for the axle, I found that I had to cross the chains over under the boiler. This is not totally realistic but is not too obvious from a distance. The chains are fed either side of the firebox and alongside the chassis members to the servo arms. The servo itself is mounted on pillars and its electrical connections are fed via flexible ribbon cable and a plug & socket connection to the receiver above. The latter facilitates the lifting of the body as mentioned earlier or removing it completely if required
Overall, the appearance of the end result is quite pleasing. The fact that it is radio controlled is far from obvious until you get quite close. Several observers have been surprised when this apparently bog standard Mamod Steam Wagon dodges them instead of vice versa!
Midwest Fantail Launch ("Firebird")
The reasoning behind this project is somewhat more practical than that behind the Mamod Steam Wagon. When a model boat is out in the middle of a pond or otherwise out of reach, you want some control over it, especially when you are aware of the fact that it is (literally) running out of steam. The model was purchased as a kit of parts; or to be more correct, two kits; one for the hull and one for the steam engine and boiler. The two kits were designed to go together but sold separately. The kit for the hull came with recommendations for fitting radio control. The two internal seats were designed to be easily removable and it was recommended that the battery was mounted under one and the servo and receiver under the other. With no reason to do otherwise, I followed these recommendations.
As with the Mamod Wagon, the choice of RC equipment was easy. I chose the cheapest I could find. Ironically, even though I needed only one channel, the cheapest system I could find was two channel. I pondered whether to install a throttle for speed control but decided against it as the last thing you want in a boat is the possibility of a stalled engine! Installation was a lot simpler than with the Mamod Wagon. Being wooden hulled, there were no problems of the type described above and there was plenty of space to put everything.
The servo for the tiller and the receiver are mounted under the rear seat, fixed in place by good old double sided sticky pads. (What did we do before they were invented?) A stiff wire goes from the servo, through a slot in the stern decking, to the tiller. The antenna, in the form of a length of wire, is taken up a flag pole at the stern. The battery holder is mounted by similar means to the underside of the forward seat, with a switch mounted in the lower decking near the receiver.
I made a few other modifications to the original design of both the hull and the boiler. However, these had nothing to do with the radio control. I am pleased with the end result, which is on the border line in definition between a toy and a model. The hull, although not based on a specific prototype, is a quite realistic interpretation of a typical real life design. The engine and boiler are not so realistic but are, nonetheless, pleasing to the eye.