John Cockcroft
Pictures by the author

MANY OF US HAVE GRADIENTS on our layouts, usually for getting trains above another track or storage yard. In my case the layout of the loft made it essential to lower a reverse loop, in order for it to be a wider radius under the roof pitch. So the main line into the station is at about 1 in 50. For reasons of simplicity, I made the goods approach as a third track next to the main lines and therefore it too is at a gradient. Operationally, the approach is part of the goods yard and when I considered how I would shunt the yard and assemble departing trains etc., I realised that the graded approach line would much more useful if I could leave wagons on there while the shunter messed about in the sidings. But while on the real railway the wagon brakes could be pinned down to prevent a run-away, there was no such luxury on a model and off they would roll onto the main line loop – not good! How could I put the brakes on?

Obviously the way to stop a train of model wagons from running away is to put a barrier across the tracks and I considered making a sort of level crossing gate that swung over the line where it disappeared off scene. But that was crude and complicated and in the end I devised the solution described here. The basic idea is to have a pin or rod between the rails that can be raised to catch the axle of the wagon, preventing the vehicle from rolling away. When the wagon needed to be moved the pin could be lowered and would also be invisible when the track was unoccupied. The pin could be operated by any convenient method such as levers and rods or a point motor, preferably slow acting. I happen to use the MegaPoint electronic servo system to operate remote points and signals in the approach tracks and loop, so that is the system I adopted.

The first thing to do was get all the dimensions planned out. First I measured the height of the normal O gauge wagon axle and concluded that my rod or pin should extend around 20mm above the sleeper top. I used the sleeper top as a base because the rod will have to sink into the ballast and that is the same height as the sleeper top. So the movement will have to be around 20mm which is a critical dimension for the operating mechanism. The other dimension that is important is the thickness of the baseboard including underlay and ballast, which is of course dependent on your method of baseboard construction and how much underlay you have. In my case the thickness was 18mm.

Next I had to consider the mechanism to move the brake pin from the level of the ballast to 20mm above it. In fact it could start below the ballast but much higher above would lift the wagon off the rails. I considered the position of the servo motor and how the crank on it would be positioned. At my age I find delving about under baseboards a neck- and back-twisting trial, so I made a rough test bed from a bit of board and a length of rubbish track and these can be seen in some of the photos. I still found that I had to do, what to me are India Rubber man contortions (in fact bending or twisting of any sort), to actually fit the thing on the layout – but Hay! Ho! “Darling I’m stuck! Could you give my leg a pull please?”

I decided that the best method of flexibly moving a rod up and down would be to use a wire extension to the bell crank on the servo and link the two, so that the arc described by the crank would be eliminated by a sliding bearing, and the bottom of the brake rod would pivot on that bearing. Gosh, that sounds clever! But what it means is that the brake rod is bent at right angles above the crank rod and the two are passed through a couple of brass tubes soldered together in a cruciform relationship.

So the crank rod goes through the lower tube and the right-angled end of the brake rod goes through the upper tube. In this way the crank rod slides along its tube and the brake rod pivots within its’ tube. The throw of the crank rod can be roughly calculated but with a Megapoint servo the throw is adjusted by the electronics and is easy to manage. In the case of manual operation using rods and levers you have to be a bit more calculating.

The first part I made was a tube that acts as a bearing for the rod as it passes through the baseboard. I made a rectangular plate from brass and soldered the tube into a hole in its middle. I drilled a couple of holes in the corners of the plate and used them to screw the plate under the baseboard. I think the brake rod was 1mm diameter brass rod and the tube needs only to be a free but not sloppy fit over the rod. I drilled a suitable hole through the board and cut the tube to be just below the ballast top and fitted the plate under the board, the tube can project below the plate which makes soldering easier and more secure.

I worked out where the servo motor should be positioned so that the crank moves up and down. I made an L-shaped brass bracket to position the servo in the correct location, which is near where the brake pin comes through the baseboard. Alternatively, you could make a brass bracket to hold a simple bell crank that was worked by manual rodding. Either way, the crank moves up and down from its pivot and the reach is extended by a 1mm diameter wire that I passed through two of the holes in the bell crank arm and bent so they form a rigid extension to the crank. At this stage the brake pin can be cut overly long so that it projects well above the desired 20mm over the track. The bottom end is bent at a right angle so that it can rest on the extended crank wire below. I then cut two lengths of brass tube that are a sliding fit on the wire crank extension and the bottom of the brake pin and soldered them into a right angle in a cruciform shape.

Fitting the tubular bearing to both the brake pin and the crank arm requires that the servo motor bracket is loosened so that the bearing can be fiddled onto both pin and arm. Obviously if the bearing unit can be manipulated to get the bearings on both rods they would fall off again, so you have to loosen the servo bracket but then retighten it, which secures the bearing. I made the first bearing tube too short and it kept falling off the end of the crank arm so I replaced it with longer tube. I tested and adjusted it so that when the servo arm is at its lowest the brake pin is flush with the ballast and the throw of the arm raises the pin by around 20mm. I cut the pin to height and, with MegaPoint control, you can adjust the throw with ease. A simple single pole switch on the control panel raises and lowers the pin.

Because my layout is still (actually permanently) unfinished, I haven’t used the brake in anger – just tested it – and it works a treat. Many of you will spot the danger! If you forget the pin is raised, all hell will brake loose if you try to move the wagons – or accidentally run a loco at the pin. So, a warning light is a good idea and could be simply arranged with a micro switch on the servo arm connected to a small bulb on the control panel or somewhere obvious near the edge of the baseboard. I haven’t got round to doing that but will probably only do it once I have had a few disasters! In the meantime, I thought you might like to hear about the device and maybe find it useful on your layout. As a final thought, I suppose the cross bearings would be good for anything else that requires up and down motion on the layout.