Producing a turntable for Waimes
According to the drawings Waimes was equipped with a 16.5 m turntable in the vicinity of the signalbox. Until now I have not found any photographic evidence on how it looked. The most likely assumption is that it was of general Preussian design dating from the opening of the line with some later NMBS additions.
Turntable
Having no photos of the real thing the main input of how it could have looked were 2 photos of the turntable in Malmedy, the next village. As this one has the same origin and dates from the same period it was most likely of identical construction. Basically this shows an undeep well with a turntable of which the most prominent feature are the four wheels that are partly visible above the deck. The photos don't show a railing on the table but as these photos date from the interbellum this was a most likely addition as other turntables all show to have a railing.
The turntable was produced in several stages. The first step existed of producing the well.
The well was constructed from 2 sheets of 6 mm Trespa outdoor wall cladding material. This can be compared to Tufnol, a sort of resin drenched mdf. It mills very well and you can easily cut threads into it. The sheets were screwed together with some M4's for permanent fixing. A 10 mm hole was drilled in the centre of the sheets and the whole lot was fixed on a rotation table. The well was then milled, the angle in the well reached by tilting the table. The table has a nice 1mm groove around the lower circumference which originally was meant to mount some FB rail in it. After that the lot was fixed into the module and left like that for a considerable period.
The well milled from Trespa with the new bridge construction mounted
The second stage consisted of constructing the motorisation. From the selection of geared motors that I have collected over the years I found a 16 mm Maxon motor with 1:1625 gearbox to be most suitable. Together with a set of bevel gears a very easy transmission was possible. The bevel gears were just waiting some 10 years for their use on something like this. They were obtained from Branchlines at some UK show. The gears have a 3 mm hole which directly fitted the axle of the gearbox. Fixing the motor was easy using 2 further off-cuts of Trespa and a clamping fixture for tubing. This comes with a long hole in the base to suit the height adjustment and the motor can slide lenghtwise.
The whole drive train in view
The vertical spindle was a bit more work needing some turnings. The 10 mm hole in the well was made smaller by inserting a brass cylinder that is used as bearing. The forces are transferred by a turning produced from some 15 mm pvc. The end sticking through is 3 mm for the bevel gear. The top has two flats milled to it that will fit the bridge. Power is transferred via a brass tube and a wire with 2 brass pick-up cylinders as rest for some PB wire contact fingers. The vertical axle has a bit of play that is taken up by adding some washers and a 0.7 mm spring wound from PB wire in between. If the bridge now is forcibly stopped the available play is just enough to enable the motor to lift the gears and go on moving without damage to the teeth of the bevel gears. The motor is that strong that you cannot hold it and without a sort of relief things are likely to break down when such high forces are allowed to built up.
Close-up of the spindle showing the tube and wire and copper contact sheets.
Instead of fixing the bridge to the spindle top I thought it would come useful if I could take it off. Thus the bridge is just hold by its clamping forces. The power to the track is transferred via some self adhesive copper shim on both sides as contacts.
photo showing copper shim contacts
The last thing to produce was the bridge itself. This is a straightforward construction of 0.8 mm PS plastic sheet. The width of the carrying construction being that of the track, 9 mm inner width. On top is a deck suitably engraved to represent planking. I decided to avoid making a tool for producing a ring of FB rail to a precise diameter that would then nicely fit in some 10 cm ring but use the milled inner edge of the Trespa as gliding ring instead. This way there was no need to make the four wheels rotating, thus these are now just four turnings stuck through the planking. The whole lot slides around on the end faces of the bridge which have some smoother material glued on the bottom. The rail on top was glued using superglue. The railings are a construction from 0.2 mm PB wire and 1 mm brass L angle. These were soldered together with help of a printed template and some double sided tape. It may turn out a bit fragile in working the table but we will see how it will hold.
The bridge may profit from some rivet detail at the lower section but unfortunately, together with the 0.12 mm PS to use it on, my rivet tool has been hiding in some yet unknown box. But because the bridge can be taken off easily this sort of detail can be added later, together with a builders plate and some missing support triangles. If more information on the thing becomes available the bridge can be replaced by a model. The turntable was hand finished using water based acrylics after giving the well an initial base coat in some cement plaster colour. The well might well have been mud with nettles, but who knows?
see and hear, the local birds are louder than the table.
The whole lot was tested with a G8, the largest loco that will fit the table. A whole turn takes just under 2 minutes using a 1.5 V battery as power source. A small movie shows the whole lot. That leaves the laying of the only track connecting it to the rest of the world but this has to wait on the construction of the neighbouring module because that will carry the connecting point.
date:26 april 2009
