Fitting Radio Control to a Lima 4F

R Chadworth

The Plastikard modified Lima 4F as a 3F, fitted with radio control and large coal load.

I have been considering improving control on my out-door, stud-contact layout. It has developed over sixty years, and I have old Basset-Lowke, Leeds Model Company, Lima and modern can motors.

The newer motors need much higher control resistance so I designed a controller using commercial wire-wound resistors between pins set in an arc on 10mm plywood. With a spring contact on a radial arm and a reversing switch set in the aluminium cover on a long roving lead, four of these feed into my ‘cab-control’ switchboard and work well except when shunting.

I considered DCC and radio control, both having track continually at full volts. DCC initially looked good, but I was advised that with stud pick-up and dirt spots on outdoor track for example bird’s droppings or leaves, I might not get a consistent signal through the track. Radio control would therefore be a better proposition, though dirt could still result in poor slow-speed running & starting, as wheel to rail contact is still vital.

Photo 1. Underside of tender showing control chip on green PCB; edge connector to left; battery connector on right; slide switch to cut receiver power below top buffer; yellow recharging leads; aerial below nearside wheels.

I had converted Lima 4Fs and a diesel to run on batteries housed in the tenders modified to take five C-type batteries installed crossways. To give a measure of control, I can switch out the fifth battery. Incidentally I do not use rechargeable batteries as they only give 1.2 volts and nonrechargeable battery life is at least a year.

Then a year ago I read an article in Model Railway Journal issue no. 218 entitled ‘The Way Ahead’ describing a radio-controlled, battery powered loco for OO gauge. This A1 Results Ltd (Micromotive) design looked an attractive proposition. I contacted Steve Leyland at A1 Results and he loaned me a Lima Bo-Bo fitted with the Red Arrow system, and powered with rechargeable batteries, to try out.

I was very impressed, particularly with slow-speed control. It was responsive over the entire length of my garden track, even in the metal lined tunnel. My first idea was to use the Lima motor and gears. Steve said that the receiver/drive unit could be set for the required voltage, but that I should allow for a 1.5v drop across the transistors, therefore a supply of 9volts was needed. In the end I decided to remotor, and that meant making new frames to accommodate the gearbox and Maxon motor combination.

The receiver/ drive unit was fitted in the tender. It is screwed to a heat sink and projects through the cut-away floor, just clearing the centre axle. The batteries were then fitted as before, the extra one at present being laid on top with a large load of polystyrene ‘coal’ to hide it. The aerial lies along the underside of the floor.

Photo 2. The tender with batteries mounted

As this was experimental, several things need to be modified.

  1. The extra battery is intended to be fitted into the boiler, but this would need a second double connection to the loco, the one to the motor being only temporary, made from a twin contact length of edge connector.
  2. The slide switch that can be seen below a tender buffer replaces the recommended reed switch operated by magnet. This cuts out the power to the radio receiver when not in use.
  3. The receiver/ drive unit is designed to be connected to a battery charger. I have left these yellow leads long enough for future use.

I have run this engine throughout the summer and have been very pleased with it on the local goods duty that involves shunting Derby & Ambergate yards. This it does very realistically with the added advantages that goods-yard track can be naturally weathered & not cleaned because there is no pickup. It can also be run in any weather.

The hand-held transmitter is powered by a PP3 battery. It can operate up to 99 locos each having a different 2 digit code. The relevant code is selected using remote control style buttons. That number is then displayed. Direction is then selected using F or R buttons, and the speed is controlled with + or- buttons. Acceleration/ braking rates are set realistically if either is pressed continuously, movement continuing at the same speed when the button is released. An intermittent touch gives very fine control.

Braking takes unexpectedly long so beware, but the button marked S stops the loco. This button also needs to be pressed when stopped before reversing. A ! Button stops all locos that are running. This may be particularly useful on a continuous track. I’m hoping to fit a similar receiver to my Jinty for Derby shunting work, but it would need to be timetabled not to coincide with the local goods as I don’t want to buy another transmitter.

Photo 3. Loco body and new frames, motor and gearbox. The original wheels have been cut out between spokes and fitted with new connecting rods