Following on from Wagonbashers post above here's some information about the coal hoppers on New Haden Collery, being that this is built for 4mm/ft you will need to increase it's size to handle material ( coal ) for your scale
It uses a rotating disc at the mouth of the hopper with this you can
Stop and start the flow by stopping and starting the disc
Control the amount of flow by controlling the speed of the disc
Control the volume by controlling the amount of time the disc is running
How does it work?
With the disc stationary and the hopper filled, the material will sit on top of the disc, with a small proportion going towards the edge; providing the disc is wide enough it is unable to get to the edge of the disc so nothing flows from the hopper, rotate the disc and centrifugal force will cause the material to be flung sideways from the disc allowing more material to flow from the hopper. The lower hopper catches the material flung from the disc and then directs it through two outlets so that it forms two cone shaped piles in the mineral wagon sitting below
The power source is a combined motor gearbox initially designed to run from 16 volts but for this application is being run at 12 volts giving an output shaft speed of approximately 260/270 rpm, this then drives the disc using plastic V pulleys and rubber belt, the v pulleys and belt considered to being a better option than a drive shaft and gears, due to the grit content of the material possible getting inside the gears and causing the drive to stall. The drive motors are being controlled by a relay and 555-timer chip, the chip is wired in a monostable mode, with the start button initiating the motor and the motor then running for a predetermined time set by the 555 timer. The timer when activated runs for about 8 seconds,
There are six filling roads on the layout, three underneath each building. The buildings contain one large hopper, which feeds the three roads;
Couple of pdf files showing side and front view of the hoppers
NHC Bunker front view with text.pdf
NHC Bunker side view with text.pdf
Main Hopper with two of the drive belts removed
Hopper underside
Underside of hopper without chutes
The individual chutes
Geoff