Articles - Experimental Doors
08/12/2005
This page documents how I built an experimental prototype for scale model doors opening and closing for a potential future project. The first thing I did was build a base upon which this experimental prototype was to be constructed. Three pieces of left-over MDF board were glued together to make the stand. A strip of flex track was glued to the top.
Experimental Doors
The objective is to hide from view the mechanism by which the doors are moved. After various ideas, a simple thought occurred to me one day. I could simply glue the door to a fairly stiff metal rod. The method for turning the doors can then be hidden below the layout, while only a small hole needs to be drilled in the layout. This photo shows the two "doors" (two pieces of styrene), the two rods that provide the pivot points, and a frame "board" to hold the doors at the correct distance from each other. In the photo the doors are already glued to the rods using 5-minute epoxy. The two small square pieces of styrene will be glued to the top of the rods to hold the doors in position vertically.
Experimental Doors
This photo shows the two stops glued to the top of the rods. I drilled holes to match the rod, which in this case required a #63 drill bit. In retrospect I should have glued those stops closer to the frame board. Something to keep in mind when I build the real thing.
Experimental Doors
The next step was to install the vertical pillars that hold the door to the base stand. I used some H-columns and Testors glue to connect the parts.
Experimental Doors
Here is the entire "above-ground" structure. From a previous attempt I learned to give myself a little bit of space between the moving parts, but I went a bit overboard on this one. The doors look more like saloon doors than engine house doors, but... it is just an experiment.
Experimental Doors
The next step was to focus on the mechanics "under ground". I decided to show this photo of how I set up the drying of the two pieces of styrene I glued to the bottoms of the rods. I used 5-minute epoxy again. It gave me time to adjust the weights that hold the pieces in the right spot. The two pieces of styrene have a series of holes drilled in them so that I could experiment with the linkage rods later on.
Experimental Doors
The means of movement is provided by a Circuitron Tortoise, a 3V wall-wart power supply, and a DPDT toggle switch. The switch flips the direction of the Tortoise. I like using 3V wall-warts for Tortoises because it moves them very, very slowly, and keeps the Tortoise quiet. This could, of course, be replaced by a stationary decoder, if so desired.
Experimental Doors
The last photo below shows the complete mechanics. The Tortoise's actuator rod (usually connected to points of a turnout) now pulls and pushes on two thin linkage rods. These linkage rods are connected to the two pieces of styrene that were glued to the bottom of the door rods. The various holes drilled in those styrene pieces allowed me to experiment with the right position for the linkage rods. Also with some bending and twisting, and a lot of trial-and-error, the linkage rods finally opened and closed the doors to the correct positions. The animated image on the right shows the model in action. The concept works, and with some careful construction, it could look like the real thing. For the final model I will most likely glue a piece of styrene to the actuator rod of the Tortoise. This will then allow me to put two linkage rods between that piece and the two pieces glued to the bottom of the door rods. It will make for a cleaner installation, easier adjustment, and longer life of the mechanism.
Experimental Doors
This is a crude animation using composites of several still photos.