Sunday, 26 August 2007

Heath End - Level Crossing

Wills® level crossing gates were used, and the posts supplied used for the stop posts; the hinge posts were made from 1/8" square brass tube, with a length of 3/32" brass rod [the size below] soldered inside, to inset into round brass tube set into the baseboard. A length of thick brass wire was soldered into two loops of thinner brass wire, which were inserted and glued into the gate at the level of the moulded hinges; this thick wire is then slotted into two loops of the thinner wire, which were then soldered into holes drilled through the post. As can be seen the thick wire extends below the baseboard, and has kinks in it, the purpose of which will be explained below. Finally, thin brass wire is fashioned into the bracing cable, which is also hinged from a loop soldered high up on the post. [click on photo above and you can see more detail].

Two lengths of the 1/8" tube were soldered side by side and were glued into two 1/8"hole drilled next to each other in a length of softwood, along the centre-line of the wood; the same is repeated at the other end. The tubes in the photo were inserted for the photo and are back to front: the longer tube is on the inside [see photo below]; the outer tube takes the post peg, the inner tube takes the operating shaft: this comprises 3/32" tube with 1/16" tube soldered inside, with a pulley attached at one end. This protrudes up through the inner fixed tube, and the thick wire attached to the gate slots into this, and the kinks act as a slip-clutch.

The tubes extend beyond the softwood by 15mm, the thickness of the baseboard + cork underlay + track height; once the assembly shown above is attached to the baseboard, the gates simply slot into both tubes simultaneously, and so can be removed to prevent damage in transit, but are immediately located AND connected to the operating mechanism when inserted. Since the road crosses the railway at quite an angle, the single gates do not actually touch as they open and close, so can be operated together: in the prototype from the signal box by wheel and rodding; in the model by elastic bands around pulleys!
The photo below, which also illustrates what I said [below] about baseboard construction, shows the simplicity of the completed mechanism: a third [double] pulley, of similar construction, turning in brass tube inserted into another piece of softwood is fixed so that it forms, with the two gate pulleys, a right-angled triangle. One pulley is connected by rubber band to the gate pulleys, the other to a fourth pulley set in line with the baseboard edge; this is operated by a simple crank handle made from brass rod and tube, which is located onto the pulley shaft by a slot in the handle tube locating over a wire soldered through a hole in the pulley shaft, much like a universal joint. When the crank is turned the gates move; the stop posts limit the arc of movement, and the slip-clutches mean it is unimportant which way you begin to turn! Nor does it matter if both gates do not move through their arcs simultaneously; the first to reach its stop post stops allowing the other to finish.
Here the gates are in position at an early stage, with notice board pins acting as stop posts. The plain office rubber bands are TOO elastic for smooth movement; the gates tend to judder a bit if you try to turn too slowly! I am hoping to locate some cassette tape deck drive belts of suitable length for the task.
The road surface and check rails in the 'four-foot' were made from the vinyl mounting board I referred to earlier [this is by no means the last you will hear of this material!], in fact a trimmed down length of the track-setter. The check rails are in fact simply scribed onto the upper surface at each edge, and then a small piece removed at each end to allow for the 'rail ends' to be bent appropriately. The road surface was then applied using professional filler + PVA, applied to the previously PVA-sealed plywood, and smoothed off to a reasonable likeness of a cambered road surface [see below for more detail]. By now I had added rectangles of the mounting board around the protruding tubes to represent the prototype footings of the post.
The gate-posts were painted white, after a capping piece cut from plastic sprue was glued on top. The ironwork on gates and posts was picked out in black. The wire mesh was cut from some wedding dress material, stretched out and painted white, and super-glued in position. The Red circular targets were produced on PC by printing an area all red on one side, and printing two circles in red with a white border on the reverse [a good graphics programme enables reasonably accurate placement - I use Serif Drawplus] and the circles were cut out and glued over the centre of the gate, on top of the mesh, so the red on the reverse shows through the mesh on the inside of the gate, as per prototype. This much better represents the thin metal plate than the thick circle of plastic supplied by Wills. The picture below shows the finished article [less lamps and a few odd details still to be added], also see the previous photo entry. Any questions to clarify anything, just leave a comment and I'll try to respond.

No comments: