Introduction

I have wanted for a long time to build a clockwork locomotive for my 16 mm scale narrow gauge garden railway, largely inspired by a couple of locomotives built by Marc Horovitz a number of years ago. I had considered getting one of the old O gauge mechanisms from the 1930s, but demand by collectors had made the cost of them prohibitive for such a kitbashing exercise. I searched for other non-railway sources of wind-up motors (old gramophones, movie cameras, alarm clocks and other such beasts) but nothing was available to meet my requirements for size, speed, power and weight. One day, some of my garden railway friends were discussing building things with Meccano (a British metal construction toy, similar to American Erector product) in their childhood. To power the mechanical creations, Meccano had two clockwork motors in their product line. The "Magic" motor was the smaller of the two, roughly 2.5" long, 0.75" wide, and 1.5" tall, and had a simple on/off lever. The "Motor No. 1" was much larger (4" long, 1" wide, and 3" tall) and had a reversing as well as an on/off lever. I understand that Meccano continue to manufacture these up into the 1970s.

One of my garden railway colleagues tells a wonderful story about playing with his Meccano clockwork motor as a child. He soon discovered that by soaking the spring in 3 -in-1 oil, more energy (and hence, a longer run) could be extracted from the spring as the leaves would slip more easily over each other. Suffice to say the oily mess that resulted on the living room carpet from his discovery prompted his parents to quickly replace it with the more expensive Meccano electric motor!

Settling upon a Mecanno motor, I canvassed the local garden railway crowd, and in a few days, I was able to acquire both the Major and No. 1 motors for my experiments. (It should be noted that they can also be readily obtained from online auctions such as eBay and used Meccano suppliers in the U.K.)

The Drive System

I took the two motors, (which had been stored for quite a while) cleaned and oiled them and began playing around. I soon realized that the larger reversible motor was best suited to garden railway use. Even though there is a tremendous amount of reduction gearing in the motor, I found the shaft speed still too fast. Therefore some sort of reduction in the drive was required between the motor output shaft and the wheels. I found suitable ladder chain and nylon sprockets (in two sizes) were available from a model airplane supplier called Hobby-Lobby off the internet. Two sizes of sprockets were available (8 tooth and a 16 tooth), I figured a 2 to 1 reduction would reduce the speed down to what I wanted. Ladder chain would also be used for the drive to connect the two axles.

A dig through the parts box yield a pair of O gauge Brandbright metal wheelsets, with 1" diameter wheels. I sat down at the computer and drew the motor and the wheels to scale and began playing around with the arrangement. I had two major design constraints. Firstly I wanted the motor on/off and reversing controls be easily reachable, perhaps from the cab of whatever I was building. Secondly, the motor had to sit low enough that it could fit inside the outline of a 16mm scale narrow gauge locomotive.

After some adjustments, I was able to come up with a design for the drive. The motor's output shaft would have a small sprocket which would be connected to a larger sprocket for 2 to 1 reduction. A second ladder chain loop would in turn drive one axle by a second set of small sprockets. And finally, the second axle would be driven off the first axle by and set of sprockets and chain.

I laid out the design on the computer and drew it up full size to get a feel for the layout of the model. With a bit of fiddling, I was able to come up with a chassis design I was happy with. It would be an outside frame beast, with a wheel base of 3.75" and a length of 7.25". A drawing of the drive system can be found here.

Chassis Construction

Figuring that the locomotive with the motor would be a bit of a weighty beast, I opted for a rather robust chassis. I fabricated a frame of K&S 1" by 1/16" brass, fastening it together with 2-56 brass bolts and 3/8" brass angle. Holes were drilled for the axles as well as for mounted more 3/8" brass angle which would hold the motor in place. The neat thing about Meccano motor is that it part of a construction toy product line and there are holes everywhere on it, making mounting it very easy.

Control

Once of the things that I wanted to be able to do is control the locomotive from two levers in the cab (on/off and direction). I also wanted to do this without altering the original Meccano motor. The motor as supplied controls on/off and direction through two levers that move up and down on one end of the motor. I wanted levers that translated the movement to a "fore and aft" motion in the cab. Obviously, this would require some sort of linkages to translate this movement to where I wanted. This turned out to be the most difficult and time-consuming part of the whole project. Even with my university engineering textbook on kinematics, and full size drawings on the computer, it took a lot of fiddling to get the levers and linkages to work the way I wanted them to. I ended up using mostly model airplane control linkages and bits to construct what I needed. The levers in the cab came from the surplus box- they are the reverser levers which Roundhouse Engineering supplies with their live steam locomotive kits. I obtained a couple from friends who added radio control to their steamers and did have a need for the levers. A drawing of the brake lever arrangement can be found here. A drawing of the direction lever arrangement can be found here.

The "Fuel Gauge"

I realized that the clockwork motor would eventually be housed deep inside the locomotive, with no way of telling whether or not the spring was wound or not. (In the spirit of the old time clockwork enthusiasts, I did not want to suffer the indignity of having the locomotive run out of power before it reached it's destination.) As the spring unwinds, the diameter gets bigger. I devised a simple "fuel gauge" which would allow the operator to see if the spring was wound or not. I installed a spring loaded arm that very lightly rests against the spring. The other end of the arm has a needle that points to a gauge marked "Full" and "Empty" with a couple of graduations in between, just like the one on an automobile. I painted the indicator needle a bright orange, which the operator can easily see through the side of the locomotive.

Bodywork

I looked on the internet at a number of pictures of tram locomotives to get a general idea of the body before settling on a design for the 16mm scale model. The critical design feature was that I wanted to carry the key on-board the locomotive (as all prudent clockwork operators should do, in case they need to wind up the motor at any time- besides it would keep the key from getting lost). Therefore, the side body skirting was made tall enough to hide the key. The bodywork was constructed out of 0.016" thick K&S brass sheet. I first cut four pieces of brass of the same height for four quarters of the body. I then annealed each with a small gas torch, I then wrapped each one around a piece of broom handle to produce a 90 degree bend. With the "four corners" of the body bent to shape, I cut each to the proper length in order to make the body. The door openings and steps were then cut out (I was clever enough to line up the door openings such that one provided access to the motor for the key to wind it). To get the perfect half circle of the step, I first drilled a number of holes inside the area to be removed. A steel washer with an inside hole the same diameter as the step hole was temporarily glued in position to the brass sheet. The washer acted as a template to allow the hole to be filed to correct shape.

The roof supports were made from 1/8" K&S square tube. The fancy scrollwork for each support post was bent to shape from scraps brass wire and soldered together in a wooden jig. I feel that the scrollwork was worth all the fiddling as it really gives the locomotive some character. The roof was also made from 0.016" brass sheet, bent to the proper curvature with a friend's metal roller. The body was assembled with 0-90 bolts and nuts. K&S angle was used in places to stiffen the body and to attach the roof to the supports. The whole body is assembled as one unit and is designed to be easily be removed from the chassis. 16 mm scale centre buffers, lamp irons, lamps and handrail knobs from Brandbright completed the locomotive. I had fully intended to paint the tram engine a dark green colour, but after receiving several comments on how delightful it looked in natural brass, I left it as such. It occasionally gets a bit of polishing from a kitchen Scotchbrite pad or some Nevrdul wadding.

I thought for a long time for a name for my tram engine (as they tend to do in the UK). The Furzebrook Railway in England named each of their narrow gauge locomotive with the Latin equivalent to the number of the locomotive (i.e.: locomotive number two is known as "Secundus"). I named my creation "Windus", figuring it was suitably majestic sounding name that also provided an indication of the source of it's power.

Operation

I found that the completed locomotive runs at a very sedate speed. On average, it runs between 50 and 60 feet on a single winding. This is not great, but it allows for one trip around my humble little garden railway! I was most impressed at how much the tram engine will haul- it is capable of pulling a 9 pound anvil on a flat car. More typically, it will haul a half a dozen 16mm scale wagons with ease.

Conclusion

I really enjoyed my first experiment in the world of clockwork. It has certainly inspired me to build some more spring-powered models. I hope it will inspire you as well and I look forward to seeing your creations.