Continental/American
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TT Gauge Standards Continental/American |
| SCALE/GAUGE NAME | TT Gauge | Prototype |
|---|---|---|
| SCALE | 1:120 | 1:1 |
| TRACK | ||
| Standard track gauge | 12mm | 1435mm |
| Rail profile | Code 75 | Grooved girder |
| Groove width, straight track | 1.25mm | 32mm |
| Groove width, curved track | 1.5mm | 38mm |
| Minimum radius curve, older trams | 105mm | 15 metres |
| Minimum radius curve, modern trams and large bogie cars | 135mm | 20 metres |
| Double track distance apart (track centre lines) | 35mm | 4 metres |
| WHEELS | ||
| Recommended to "OO" gauge BRMSB standards (ie Jackson, Romford or Tenshodo). | BRMSB | ------ |
| Back to back | 10mm | ------ |
| Axle diameter | 2mm | ------ |
| OVERHEAD | ||
| Minimum height above road | 50mm | 5.8 Metres |
| Wire type and diameter | Nickel silver 0.3mm | Copper 8mm |
| Length of traction pole above ground | 70mm | 7.62 metres |
| Distance apart of traction poles on straight track | 120mm average | 36 metres (maximum) |
| Distance apart of traction poles on curved track | As required | As required |
| Position of overhead wire relative to track, trolley poles. Straight track | Over centre | Over centre |
| Position of overhead wire relative to track, trolley poles and pantographs centrally mounted on long bogie cars (like Blackpool). Curved track. | Over inner rail | To a complex formula |
| Position of overhead wire relative to track, bows and pantographs over bogie pivots. All track. | Over centre | Over centre |
| Ear, frogs and crossings, commercially available from Mark Hughes. | Use Commercial items. | Various |
| Trolley pole commercially available from KW Trams. | Use Commercial items. | Various |
| Trolley wheel (actually fitted as non rotating, operating as a skid) commercially available from KW Trams. | Use Commercial items. | Various |
| Trolley skid | Use Commercial items. | Various |
NOTES
TRACK
The recommended track is either Code 75 solid nickel silver, flat bottomed. Flexible track, points and crossings of both these types are produced by Peco (called 'HOm') and are recommended.
WHEELS
The width of tramcar wheels are much less than railway wheels, with a smaller flange and flange depth. However, in 'TT' gauge to use exact scale wheels would require very precise track construction and wheel setting. To get reliable running, most modellers use normal 12mm gauge commercially available wheels and track, that is to the rather coarse scale railway standards. Although the wheels and groove are much wider, visually it is acceptable. In 'TT' gauge it is usual for modellers to use the most suitable motorised chassis available. For example the Halling 'HOm' motorised chassis for bogie and four wheel cars.
OVERHEAD
There are no ready made traction poles available commercially. So make your own from 3mm diameter brass or steel rod. The poles should allow an extra 15mm at the base for fixing to the baseboard. Holes should be drilled in the baseboard to give a push fit for the poles. In "Distance apart of traction poles on straight track" we recommend that the poles are closer than prototype, as this increases the apparent length of small layouts and makes them look more realistic and interesting.
Overhead ears and frogs in 'OO' gauge are made by Mark Hughes. Though slightly too large they are visually acceptable for 'TT' gauge.
Working trolley poles will need to be scratchbuilt, though parts from commercially available 'OO' gauge poles can help. These are made by KW Trams. Many 'TT' gauge tramway layouts have overhead wiring but dummy trolley poles.
Pantographs used by tramway modellers are always commercially available items from the model railway field. It is not worthwhile trying to scratch build this item.
POWER SUPPLY
The standard power supply is 12 volts DC, using model railway controllers. The recommended controller is the electronic feedback type and the handheld (HH) from Gaugemaster has been used with great success. It requires a separate 16 volt AC supply from a transformer (also available from Gaugemaster). The controller is very small and can be carried around the layout with ease.
There are two main styles of operating trams in "OO" scale. Using two rail supply, just like the model railways, or, more properly, using a live overhead system. Here the power is fed through the overhead and returns via the rails, just like the prototype. However, there is one major difference between model and the real thing. In the model the overhead is one continuous electrical supply. All sectioning is done through the track. This makes modelling much easier and prevents stalling on overhead dead spots.
LINKS FOR WHERE TO GET EVERYTHING
List of TLRS standards for other scales.
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