Gordon H

Rather than choosing according to 'Size', a better approach is to choose by 'Rating'. The type of insulation used on the wire also has a bearing on this, but for the most part we would be dealing with PVC insulation. 7/0.2 is equivalent to 24AWG, and is normally rated at 1.4A 16/0.2 is equivalent to 20AWG, and is normally rated at 3A Note that the current values shown at the Wikipedia link are Fusing Currents, i.e. the current at which the copper wire itself would get hot enough to melt and go open circuit . Not recommended for model railway use! The normal ratings are much lower because they take into account the limitations of the environments for which they are intended.

Did the kebab van arrive late today? Only I see there isn't any smoke coming out of it yet...

Just unearthed one of my Lima 87's fitted with a cross-arm pan for a few photos. Must be well over ten years since it last saw active service under a wire, so it's all a bit grubby at the moment having had no maintenance in that time. Unfortunately, the elastic springs have perished, but otherwise it would still be serviceable with a bit of attention. The only proprietary parts used were the head (Lima, came with the loco) and the insulators (Sommerfeldt). One of the most awkward aspects of the construction, which a kit version would also need to overcome, is that the lower arms feature a square tapered cross-section. Mine were hand-filed, having first drilled a 0.5mm hole at the 'thin' end for the upper arm pivot. I believe this was one of six pans assembled as a batch, once the necessary assembly jigs were constructed.

I don't have any close-ups to hand, but you can see some examples in use on another thread: http://www.rmweb.co.uk/community/index.php/topic/11355-25kv-overhead-wires/page__st__125 (about 1/3 of the way down the page)

My article on the subject appeared in 'Model Railways' in (I think) Feb 1984. However, I didn't have any proper drawings or dimensions to go from, everything was either estimated or extrapolated from the few pictures available. It was only on a later open day at Crewe Electric depot that I got the opportunity to take a few measurements - but I had moved on to Brecknell-Willis types by then. The basic principle of construction still holds good though.

It's more to do with high voltage than high frequency as the extra voltage the 'Relco' generates is supposed to break through whatever isolating medium is in the way. Excessively high voltages are what DCC decoders don't like.