This type of intermodal crane is similar to the large ship unloading cranes you see at major ports, except it is smaller and does not have the large boom off of one end. My crane is freelance and not built to scale, but the real thing would typically be used in a railroad yard for transferring standard containers from a truck to a railroad car, or vice versa. The hoisting and trolley movement functions are each powered by an Erector P55 motor. The entire crane is on wheels, four in each base, but travel on wheels is not powered (yet). The control panel is located at the bottom of the left leg in the photo. The model is about 39” long by 13” wide by 29” high overall.
Instead of a hook, the crane has a lifting frame which attaches itself to a container, and containers can be transferred from train to truck or vice versa as in the real thing.
The trolley is pulled in either direction by two cords (the trolley itself is not powered). Each cord runs from one end of the trolley, around a pulley which is powered by the motor drive at the left end of the gantry, across the inside of the gantry, around another idler pulley at the opposite end, and then back to the opposite end of the trolley. Thus, a continuous loop is formed. The trolley stops automatically at each end of the gantry, even if power is still applied. Here’s how that works:
The trolley rails on one side of the gantry are electrically insulated from the frame. There are three rail sections – a long center rail (an MB angle girder), and a short stop rail (a BE angle girder) at each end. The stop rails are electrically isolated from the long center rail, which is always alive. When the trolley switch is thrown – say to the left – the motor circuit is completed through an insulated rail, the trolley’s wheels and axles, and the gantry’s frame (ground) – and the trolley moves to the left. When it rolls onto the left stop rail, which is dead, the circuit is broken and the trolley motor stops. Now we throw the trolley switch to the right. This makes the left stop rail alive, the circuit is again made, and the trolley rolls to the right. When the trolley rolls onto the right stop rail, which is now dead, the circuit is again broken and it stops. At any time, only one stop rail is alive and the opposite one is dead. Model railroaders have long used this technique for automatic control of their trains.
There’s a lot of wiring in the photo – that is because all of the wiring from both motors (four wires each) and the three insulated rails congregate at a long barrier terminal next to the trolley motor. Two cables run from there to the control panel at the bottom of the left leg.
The hoisting cord runs from the winding drum (EK or MR) to a pulley on the underside of the trolley, down around the pulley on the lifting device (or hook), back up to another pulley on the underside of the trolley, and across to the opposite end of the gantry where the end of the cord is fixed.
The hoisting and trolley power units are each mounted on a standard frame and are each designed to use almost any type of low voltage motor. Power units with different kinds of motors can be interchangeable. In addition to the Erector P55 power units, I have power units with efficient DC operated gearhead motors which can run on penlight cells. I can swap out both the trolley and hoisting power units in about half an hour. At the convention I used batteries and DC motors for power. The wiring system and control panel will work with either kind of power unit. The consequence of this is, there are four wires needed for each motor. Two additional jumpers have to be installed for DC motors. The wiring and control system will also work with sideplate motors such as the P58, and even Gilbert Meccano sideplate motors! It is not designed for 110 volt motors as these cannot be reversed by remote control. I favor the DC motors because I can exhibit the model without needing a power plug-in. Remote controls can be added easily.
The lifting device is a rectangular frame with a small hook dangling at each of the four corners. It is positioned just over and a bit to one side of the container. The trolley is then moved slightly so the open parts of the hooks are under the side rails on the container. When the device is lifted the hooks grab onto the container so it is also lifted. Precise control of motor speed is needed! (Learned this the hard way at the convention!)
The container has opening doors at one end. It fits perfectly on a Lionel Standard Gauge flat car, suggesting the crane could be the center of a train layout at some point.