Tuesday, December 18, 2012

How I constructed a loading hopper

The copper mine is an important feature of the railway as it was the supposed reason for the line's existence. I recently started construction of some low-relief mine buildings (See How I constructed some low relief buildings for the copper mine - pending) and had planned to scratchbuild a loading hopper, but I happened to come across a wooden kit by the German company of Holzmodellbausatz  on a well known internet auction site.

The kit contained all the pieces needed, most of them pre-cut, and an exploded diagram with some instructions in German.

Although the exploded diagram was well detailed, my lack of ability to read German meant I had no indication as to the order in which the pieces should be assembled. I decided that as the hopper looked to be the most substantial part of the model, I would start with that. The four pieces of ply were glued with exterior PVA and tacked together with copper panel pins.

The four pieces forming the upper part of the hopper were then assembled and glued to the lower section.

Next, the internal sloping pieces for the hopper were glued into place.

The main structure of the hopper was completed and so this was left overnight for the glue to harden. The next most obvious components to be tackled seemed to be the legs. These comprised four pieces of 8mm square stripwood, 336mm in length. There were tacked and glued to the sides of the hopper.

To these were glued the platforms on either side of the hopper, with lengths of stripwood glued and tacked on to keep them aligned with each other.

The side platforms were grooved to allow a door to slide beneath the hopper to control the flow of rocks etc.. I decided not to construct this as operational as the fairly basic mechanism looked to be more functional than realistic.

The struts for the legs were then glued into place - two per leg.

Although I have a fair amount of confidence in PVA as a wood glue, I was not too sure about the bond between the struts and the legs and the rest of the structure. Short pegs from cocktail sticks were inserted into suitably drilled holes ........

....... before the supports for the legs and struts were glued into place on the foundation blocks.
 Pegs were also used to keep some of the other timbers aligned and in place. These were trimmed and sanded smooth once the glue had set.

The main framework members around the hopper were then glued into place. Initially I concentrated on the more substantial 8mm square members.

The 8mm x 8mm cross members for the legs were then pegged and glued into place.

 I then focused on the 3mm x 8mm framework sections, which needed to be trimmed to size. I decided not to follow the exploded diagram and so placed the timbers where I thought they looked most at home. I also took the opportunity to use them to disguise the join between the sides and the ends of the hopper.

 The main structure for the hopper was now complete.

At this point I decided to treat the wood, using a spirit-based wood preservative (Cuprinol). The stripwood was clearly pine and I had no idea as to whether the plywood was exterior grade and so I decided to take no chances. I flooded the exposed woodwork with two generous coats of preservative and then touched-up any areas which had not absorbed the preservative (ie those already covered with PVA glue) with a muddy mix of  acryclic paint.

Whilst this was drying off, I cut the pieces needed for railings. In the kit, these were supposed to be made from various pieces of stripwood, but to my mind they looked too heavyweight. I decided solder together some metal railings from pieces of brass rod and 00 code 100 nickel silver rail. Firstly, four 6cm long pieces of 00 rail were cut and drilled to take the bars of the railings.

These were then slotted into place in suitably drilled holes and 1.2mm diameter brass rods were threaded through the holes and soldered into place.

The railings were then removed and given a couple of coats of grey primer and a coat of matt black paint.

The railings were then fixed back in place with some epoxy resin to hold the uprights firmly in the holes. A ladder left over from my construction of semaphore signals (see How I constructed semaphore signals - pending) was then cut to length. The legs of the safety hoop were inserted into suitably drilled holes in the side of the platform .........

.............. and a piece of stripwood was fixed to the base of one leg, to which the ladder was attached with a couple of loops fashioned from brass rod.

At this point I decided the main structure for the hopper was complete - though in the future I intend to construct a representation of some sort of operating mechanism for the doors.

I tried siting the hopper in its intended location at the copper mine but some additional foundation work will be needed to widen the raised timber trackbed on which it sits. In the meantime I temporarily positioned the hopper on the timber siding at Peckforton Station for a quick photoshoot.

I am considering weathering the hopper - blanching the timbers slightly and depositing layers of rock dust in the nooks and crannies. However, I am postponing this until I finish the mine buildings which are presently under construction (see Progress Report 43). Ultimately, the hopper will be connected to the mine buildings via some sort of conveyor to supposedly take the copper ore from the base of the crusher up to the hopper (see How I constructed some mine buildings - pending). The actual design of this will be dependent on the relative positions of the hopper and the building housing the crusher.

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