Kit Details.

 This has been a personal project of mine for nearly 10 years. The desire to have a highly detailed, accurate and most importantly, perfect working turntable was desired. The kit is primarily based on the manually operated 75' turntable at Muswellbrook, what I hope to have as the feature of my HO home layout, however most of them followed the same design.

Unlike other turntables on the market, the pit itself includes all the details of the prototype like concrete part lines, correct profile and drainage details. 

The pit is made from an aluminum billet that was hand machined to the correct profile and to ensure absolute accuracy. It incorporates a stepped edge that accurately aligns the ring rail that comes pre rolled in the kit. A central hole houses a flanged bearing that accepts the main shaft ensuring that its perfectly centered in the pit. The pit has all the part line and drain grate details. The master pattern was used to reproduce cast Hydrocal (high quality casting plaster) pits that are cast directly onto marine grade 12mm plywood. The plaster allows easy staining or painting to better represent concrete. Scale timber is provided to replicate the timber blocks that support the ring rail along with the timber sleepers that formed part of the pit wall.

 

The bridge is constructed from a nickel silver etch. Again, it has all the necessary rivet and brace details as per the prototype. The four outriggers on the bridge incorporate small ball bearings that run around the ring rail which take the weight of any loco up to and including the 38 class, giving ultra-smooth operating characteristics. There are cast brass handrails along each side of the bridge along with 3D printed details for the lock pawl, at the ends of the bridge, and lock plates for the takeoff roads (8 supplied in the kit). The completed bridge locates over an accurately sized 3D printed block attached to the main shaft. This block has a two-pin female connector fitted inside it and the bridge itself has a small PCB with male plug to bring power to the bridge rails. The bridge can simply be located over the block and plugged in for electrical supply. It can also be removed for cleaning and servicing. 

On the underside, a simple wiper system is used for bringing track power to the bridge so your sound equipped locos can turn a full 360 degrees with no interruption to the sound. Everything is included in the kit less rail for the bridgethe indexing system and the usual paint, glue solder etc.

Our turntable has been designed for use with a number of commercially available indexing systems that use stepper motors for the drive.

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INDEXING - The most important part!

Included with the kit is an acrylic disk that is mounted on the underside of the turntable. This disk is laser cut to accept our three primary recommended motor drive options for turning and aligning the bridge to the roads.

These motor drives, primarily stepper motors, attach directly to the main shaft via the included rigid coupling eliminating any possible backlash from gears or the like ensuring ultimate accuracy for indexing alignment. 

My primary recommendation for indexing is the NYRS (New York Railway Systems) indexing system from the USA. This system features a keypad control, indexing of up to 99 tracks, Indexes both ends of the bridge, very fine 0.025 degree indexing resolution. Simple programming, select from 14,400 possible stopping locations, high torque stepper motor with internal gearing for quiet slow smooth operation.

 

Alternatively, a slightly cheaper option with similar features is the MERG (Model Electronics Railway Group) indexing kit from the UK. This is however a kit, and the electronics board would need to be assembled. Again, it uses a stepper motor with separate gearbox but has a much simpler control via rotary switch and toggles. It can only program a total of 32 tracks with a possibly upgrade to 64 track stopping positions. It has the momentum for bridge speed and seems to work OK.

We are in the process of having a PCB made for the MERG kit that eliminates the issues caused from bad connections to the hexadecimal rotary switch. This board along with an assembly service for the kits is being considered. Please contact us for more info.

 

The final option is for those who want just a single 180 degree turn system. We have been offered to use a simple 3D printed gearbox drive unit that allows an adjustable 180 degree turn of the bridge. This gearbox was designed by fellow modeller Stephen Buck.

The simplest variation uses cheap Ebay gearmotors and gears fitted inside the gearbox along with two micro switches, diodes and a toggle switch that starts and stops the bridge. There is also an option have the gearbox driven by a stepper motor that can be controlled via Audino. This is still under development but is looking very promising and initial testing shows it to be a good simple drive system.

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All three of the above systems are adaptable to our kit. Links to both the NYRS and MERG systems are below.

Video links are provided to show the three systems in use on our test setup.

You can of course source your own indexing system. There are many other systems available including those that use Arduino control. 

 

 

          

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