21 June, 2021B
The drawings and photos below are for an operating incline railway that was built by the London Model Railroad Group for its 'O' scale model railway club located at London, Ontario, Canada. This is a single car model loosely based on a double car incline that operated at Port Stanley, Ontario.
The mechanism is driven by a geared slow speed motor and controlled by an electronic timer circuit. The car waits for a preset time at the top and bottom of the incline before being slowly lowered down or pulled up the track.
The first drawing shows the basic incline railway system layout. The drive mechanism is located below the layout benchwork for easy access.
Next is a photograph of the cable car near the top of the incline. The idler wheel is at the end of the rails. The car is equipped with spring loaded buffers and was built with brass stock material. Detailing is limited as the incline is not very close to the viewing area.
The next photograph shows the drive mechanism and motor as they were built for the incline railway. The terminals are for the motor (1,2) and for the timer circuits control inputs (3,4,5). The drive motor uses six stages of gear reduction to achieve its low speed output. The entire assembly is mounted on pieces of wood which are attached to the layout benchwork with aluminum angle stock and bolts.
The drawing below is of an idealized version of the prototype cable car drive mechanism. The motor is not shown in this drawing.
A brief description of some of the assembly components follows. A similar mechanism is used to control the large horizontal traveling fence gates that are seen at many industrial facilities. If you could get a look at one of these or find a used one a lot of design hints could be gained.
There is a considerable amount of machine shop work needed to construct the drive mechanism. For our model we were able to find two narrow take up drums and machine them so that they fit together to make one drum.
GROOVED TAKE-UP DRUM - A cast aluminum drum with a continuous smooth groove, much like a thread. The drum winds in or pays out the cable (cord) as it rotates. One end of cable is fixed to the drum and enough is wound onto the drum to allow for the total length of travel of the car along the incline. As the cable is pulled in or payed out the car is raised and lowered along the track. The diameter of this drum greatly affects the speed of movement of the car. The diameter should be as small as practicable for the length of cable needed for the cars travel. A smooth drum could also be used as long as the cable will lie flat when being drawn in.
The CABLE is a thin cord that will not stretch and is not overly elastic so that the car does not have a jerking motion as it travels. Some experimentation will be needed to find the right material.
TRAVELER BLOCK - A solid brass piece that has smooth holes to follow the guide rods on either side of the mechanism and a threaded centre hole so that as the drive shaft turns the traveler moves back and forth. The small holes in the top of the traveler are for lubrication. The brass rods that extend from the ends of the block make contact with the springs and are used to operate the control circuit.
BRASS TERMINAL BLOCKS - Form the start and stop switches for the the inclines control circuit. These are small blocks of brass with a horizontal threaded hole through the block. A long 6/32 machine screw is threaded through the hole and a wire attached to the block is connected to the control circuit.
6/32 MACHINE SCREWS - Run through the brass terminal blocks are used to make adjustments to the stopping positions of the car. When the adjustments are set the nuts are used to lock the screw in place. The springs on the ends of the machine screws are from retractable ball point pens and simply prevent the rods of the traveler from being bent through repeated contact with the screws.
THREADED DRIVE ROD - supports the take up drum and moves the traveler block back and forth along the guide rods. It was made from round bar stock, turned down and threaded as needed to mount the drum. The drive end is also turned down for the motor coupling connection and to allow a thrust bearing to be formed by the fibre washers and the left angle iron piece. The two nuts set and lock the clearance of the thrust bearing. The full diameter of the rod is threaded with regular U.N.C. thread along enough of its length to allow full travel of the traveler block.
HARDWOOD BOARD - The motor and drive mechanism are mounted on a 1-by hardwood board. The board acts as insulation for the control contacts and the common of the drive frame. A second board supports the drive mechanism and holds the motor.
CAR - The car for the incline railway can be of any design but needs to be heavy enough to travel down the incline under its own weight.
The schematic is for the automatic cable car control circuit that operates the drive mechanism in the above drawing. It is essentially dual timers that are switched by a simple two transistor SET - RESET flip-flop circuit. Two timers allow the time that the car remains at the top and bottom of the incline to be set independently. The outputs of the timers control a solid state double pole double throw relay made with six transistors.
The flip-flop circuit is controlled by two mechanical contacts that are built into the drive mechanism. When the car reaches the top or bottom of the incline one of the contacts is made, the car stops and the appropriate timer begins its cycle. The car waits for a preset time before returning to its previous position. The frame of the drive mechanism acts as the common connection of the control circuit switches.
IC 3 is part of the L.M.R.G. circuit and therefore was left in for this article. IC 3 can be omitted from the circuit and the mechanical contacts connected directly of the bases of Q1 and Q2 if desired. This would simplify the circuit but would not change its operation in any way. A schematic of the circuit without IC 3 follows.
Please note that when the car is stopped the outputs of the timer chips (pin 3) are high. In effect the timers are always triggered except when the voltage across C1 or C2 is above the reset threshold of the timer (2/3 Vcc).
The voltage Vcc is the power supply voltage of the circuit (12 volts DC).
The car is sitting at the bottom of the incline to start.
Contact S1 is closed and the Q1 side of the flip-flop is turned off (not conducting). The Q2 side of the flip-flop is on (conducting).
Capacitor C1 charges through R1.
When the voltage across C1 reaches 2/3 of Vcc the output (pin 3) of timer IC 1 goes to a low state.
Transistors Q3,4,5 of the relay will turn on. The motor and drive will pull the car up the incline.
When the car reaches the top of the incline the S2 contact on the drive mechanism will close.
The Q2 side of the flip flop will be turned off and the Q1 side will turn on.
The voltage across C1 will drain through Q1. When the C1 voltage drops to below 1/3 of Vcc the output of timer IC 1 will go high. The relay is turned off and the car will stop.
When the Q2 side of the flip flop turns off the voltage across C2 begins to build through R2 and the IC 2 time cycle is started.
When the voltage across C2 reaches 2/3 of Vcc the output of timer IC 2 goes low and transistors Q6,7,8 of the relay are turned on.
The motor is reversed and the drive mechanism lowers the car down the incline.
When the car reaches the bottom contact S1 makes and the Q1 side or the flip-flop is again turned off and the Q2 side is turned on.
The voltage across C2 will drain through Q2. When the C2 voltage drops to below 1/3 of Vcc the output of timer IC 2 will go high. The relay is turned off and the car will stop.
The car is now at the bottom of the incline and the IC 1 timer restarts its cycle. The operation will now repeat itself.
The diameter of the cable drum has a large effect on the speed at which the car is raised or lowered. For example if the drum has a diameter of 2 inches the length of cable pulled in or let out for each turn of the drum will be 6.3 inches. A 2.5 inch diameter drum will use 7.8 inches, a 3 inch drum will use 9.4 inches for each turn of the drum. Choosing a smaller diameter drum will give a slower speed to the car for a given drum RPM.
It is not necessary to have the car at one end of its run when turning the power on or off. The car will move, after the time delay, in the direction to which the Q1/Q2 flip flop defaulted when the power is turned on. After this normal operation will resume.
Although IC 3 is not absolutely necessary for the incline railway circuit it will allow photocells to be used to control the flip flop if desired.
The diode D3 is used to prevent both timer IC's from having a low output at the same time. Although this should never occur, it would cause a short circuit through the transistor relay if both sides of the relay were on at the same time.
Diodes D4 and D5 allow the relay and motor circuit to be supplied from a lower voltage source than the timer circuit. A separate power source could be used for the motor if desired.
The solid state relay could be replaced by two mechanical relays. They could be driven by Q3 and Q6.
The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.
If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.
Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.
21 June, 2021