THE WORKING ‘N’ GAUGE LOADING PLANT
All pictures & text are copyright of Maurice Houghton
My main hobby is building and running ‘N’ gauge model railways.
Running passenger trains always looks so sleek and smooth especially when it is a rake of matched coaches snaking through the countryside.
What I find most interesting are freight trains and the varied array of stock. For years manufacturers have fitted fixed loads in ‘open wagon’ stock and for years I’ve spent taking the fixed loads out so that I could add my own loose loads.
I also have a great interest in quarrying and their workings so with a quarry modelled on my layout it wasn’t long before the need arose to load loose ‘stone’ into hopper trains without spilling more than was being loaded. Spillage is a big problem with loose loads of ‘stone’ both when being loaded and when travelling. Spillage in the loading area can build up under the wheels of stock causing a derailment at the loading point. The loads also need to look as full as real life loads. Therefore, accurately loaded hoppers are essential so that running trains don’t shed any ‘stone’ especially into the blades of points causing derailments or bad contacts of the blades. Derailments of model trains carrying loose loads are almost as difficult to clear up as the real thing.
Many hours were spent designing different mechanisms for metering the load so the stone stopped flowing when a ‘full’ load was reached. Another problem with loose ‘stone’ is the mechanism can be prone to jamming when ‘stone’ cannot easily flow through the metering mechanism. An Archimedean screw system has too much friction with loose ‘stone’ so the idea was dropped from the list.
The sliding drawer system does not give a realistic loading rate dropping a measured amount in one drop with little control over the ‘full’ load or load shape for different wagons sizes.
I hit on an idea one day about six or seven years ago whilst thinking of how ink is delivered from a ball-point pen. The ink only flows when the ball-point is rolling and stops when the ball stops.
A few design sketches later the design was chosen and build started. A roller and shaft were produced and made to rotate in bearings normally bought for use with wagon axles to provide very low friction. A spur gear fitted near to one end of the roller shaft engaged with a worm gear on a vertically mounted DC motor running from around a 6V DC supply. A close-up photograph is shown below. Gears are from the range supplied by ‘Squires’.
The end of the hopper chute lies behind the centre-line of the roller so that the ‘stone’ lies against the upward curve on the rear of the roller. When the roller stops the ‘stone’ cannot fall up-hill and therefore stops flowing. A regulation plate, slotted for adjustment, is required to meter the amount of ‘stone’ and to stop the uncontrolled free-flow over the roller. The plate is held on two brass screws soldered to the hopper body. Two nuts and washers can be used to adjust the plate to suit different loads such as sand, coal, stone etc. The plate may also be adjusted to be lower at one end than the other to provide a narrower delivery of the load again to obtain the desired full load shape. The centre-line of the delivery chute is not directly below the centre-line of the roller but slightly forward as seen on the next photograph. The delivery aperture of the chute is almost below the radius of the roller. This helps prevent the ‘stone’ coming off the roller from ‘bouncing-off’ one side of the chute and therefore not dropping vertically through the chute opening and into the hopper wagons below producing either an offset load or spillage over one side of the wagon.
The power supply is controlled by a non-latching push button which can be pressed and released to obtain the load level required.
The above picture shows how the ‘stone’ sits on the stationary roller until rotation starts again.
This picture shows the tapered chute with its narrow delivery opening relative to the roller radius.
The roller and motor are both supported by an ‘L’ shaped bracket to maintain the gear meshing relationship and the assembly fixed to the main storage hopper by brass screws, nuts and washers again on slots. This allows the arrangement to be moved up or down to adjust the ‘roller to chute edge’ distance. This adjustment and that of the regulation plate are both crucial for the correct flow control of the‘stone’.
The shape of the main storage hopper can be varied according to the size of the batching plant required. The inclination angle of the different sides of the storage hopper also needs to provide slopes that the load material will run down un-aided as the lower material is removed by the roller from below. If the angles are wrong the flow of the load will ‘dry-up’ and stop. A ‘stuck-load’ can also be caused by having the storage hopper too deep with too much weight pressing the load material against the roller.
Trials were held with the brass sheet to be used for the hopper and the material to be loaded. Before construction started brass sheet was positioned at different angles to ascertain the maximum and minimum angles that would affect the flow of the load material. The hopper shape was then designed using angles within the range.
The ‘stone’ used in my quarry is from the ‘Greenscene’ range No GS408 which I believe to be ground almond shell. This material is very light and flows well over the roller. Granite chippings do not flow well because of their irregular shape and weight. This also applies to other quarrying machinery where regular flow-rates are essential for realism, i.e. conveyors, dragline excavators, etc. With granite chippings fully loaded trains are very heavy and can cause locomotive wheel-slip.
Below are pictures of how the hopper shape and layout of the motor and roller assembly are packaged, mounting of the motor and roller assembly, a view inside the hopper, the batching plant in position on my ‘Hoghton Road’ layout, loaded hoppers showing the full-load shape as it landed and the sleeper-less track under the load area for spillage collection. Other pictures of ‘Hoghton Road’ are shown under ‘Members Layouts’ section on the club website www.leylandmrc.com
Below where the wagon to be loaded stands the rails are without sleepers and soldered to brass channels to allow any spillage to fall through the track into a removable collection box. This can then be periodically emptied back into the quarry or hopper as desired.
I have deliberately not provided dimensions for any of the above designs because loading plants will vary for each layout requirement and will all will need to be scaled at ‘N’ scale.
I hope this article is of help to modellers who like to see working trackside features as I do. If this article is found to be helpful more articles may follow at a later date.
Leyland Model Railway Club