Thursday, October 24, 2013

Limiting the top speed of model trains

Richard asks: My 6 year old nephew, has a model railway we've all conspired to build for him. It's the usual roundy-roundy double oval with a couple of sidings, and he usually has the Hornby Flying Scotsman belting round at top speed. Which is the problem - top speed is a scale 150 mph or so, and we have regular derailments on the small radius points and (lack of) curve transitions. Being as he is, he loves watching the trains go by but doesn't have a real grasp of cause and effect on the crashes (and rather enjoys them, but we don't...)

Which brings me to my question. Do you have any ideas for slowing things down? I've suggested an appropriately beefy power-rated resistor in series with the DC controller (an ancient Gaugemaster), and we've also had suggested making a mechanical stop to restrict the knob on the controller from getting to higher speeds. Has this wheel been invented before?


The photo, scanned from a 20 year old print, shows the Leamington & Warwick MRS Thomas the Tank Engine layout. Dating from the days when Hornby only produced a couple of the engines, we had a full set (Full book set, this was before they started inventing new characters for the telly) mostly made by some of the top finescale modellers in the country.

Anyway, these ran on a layout operated by kids so we anticipated the same problem as Richard and many other parents is experiencing. Our solution was subtle - the front controllers were conventional mains-powered units. Their output was fed into some old H&M units and then on the track.

The back stage H&M controllers were designed to be fed with 16V AC but since they were essentially variable resistances, this just meant that they limited the top speed of each loco. I suspect any controller designed to be fed with a 16V AC output would work although older non-electronic models are probably a better bet.

The advantage of this method was that it allowed the controller hidden around the back of the layout to set top speeds for whichever loco was in use at the time. Since they all had different characteristics, this made life a lot easier for us all.

Hope this helps - good luck and happy modelling!

1 comment:

James Finister said...

There is also the DCC route, where a top speed can be programmed in for each loco.

Another good tip is to fit a diode across a gap in a loco's length before the end of a siding so the loco stops but can still be driven out in the opposite direction.

I learned this tip after building a bookcase layout on a top shelf....