Modern sand and gravel machinery are just big ugly looking pieces of equipment, and this is what I wanted for the look at my Sun Valley sand and gravel pit. The operating bunker is used to load the Tyco operating hopper cars to dump HO gravel at other places on the layout.
This article is a general overview of how I built the loader to operate and noted important features I needed to include in the design. Your model gravel or coal bunker can be made of wooden timbers or some metal design, but the Bunker should to hold enough material to fill four Tyco hopper cars at a time and the electric gate lifting solenoid has to be simple to work all the time. That's really about it.
Building the bunker was another mater, the gravel hopper side of the model went along fine, it was a mechanism that I was worrying over. The opening and closing device that allows the flow of material. Everything has some sort of physics to understand how things work and so does modeling a device to open and close a chute that sand flows through. I looked at prototypes methods. but most just don't scale down for modeling.
I knew the best way to make the loading chute operate was to use small electric solenoid, but it had to fit someplace on the model itself. Checking my collection of parts from dissembling old printers and FAX machines and found a suitable solenoid for the project. The solenoid was to set on the top of the bunker and enclosed within Evergreen Co. styrene, corrugated sheeting.
I decided to mount the solenoid at the top with the pull-pin operating downward into the hopper. At the bottom of the bunker is a 1/4" hole where a 3/8" Dia. glass bead drops down and closes the filling hole from inside the bunker. (Note: Glass beads with a hole through them can be purchased at craft stores) A .030 wire goes through and is glued to the glass bead to lift it from the hole thus allowing the gravel to flow through and into the hopper car. Lead fishing weights were added on to the steel rod as needed. This is really simple method and works very well.
These are all the parts made up for the operating bunker: 1. The gravel hopper. 2. The solenoid and top assembly. Note how the wires go in to the coil. 3. The close-off assembly. 4 Two screened grates that slide into the top assembly (H) beams. Do not glue these in place, this way a screen can be slid off to the side so fresh gravel added into the bunker.
Here is how the bunker looks assembled, I still need to model build a (non operating) conveyer for loading material from the ground into the top of the hopper. The Gravel Bunker will share space with the Scrap Company that has been removing older mchinery at the plant.
The clicking sound in the movie is the solenoid operating the dump gate, sort of sound like a miniature rock crusher. Now the question is what type of electrical device is used to drive the solenoid?
Okay, its an old time telephone magneto that can be easily found on ebay for a few dollars. Just directly wire the magneto up to the solenoid and turn the magneto's hand crank slowly, causing the small solenoid rod to reverse direction each time the field is charged. Other things I want to make using a reversing solonoid is a model an operating rock crusher. That goes with the conveyers and all the other stuff gravel and sand pits industries have.