Class 10 diesel electric locomotive

This is my 5" gauge model of the class 10 loco recently finished (November 2005). It is based on a prototype that I think is still based at Loughborough, loco 4067. The model loco is a 24V electric powered and uses three drive motors, one for each axle. It has dummy sanders and vacuum brake pipes. It is fitted with whistle, diesel sound in synch with speed, working head code lamps and exhaust smoke generator.

There are some differences to the full scale due to the design of the commercial fibreglass body available, but as it is not intended to be a scale replica perhaps this can be overlooked by the true scale buffs.

Electric schematic

 

Two 12V lead acid batteries power the drive motors and the 4QD 40 Amp control unit. The whistle and sound unit are powered from one 12V battery and the servo driver from a separate NiCad 4.8 source.

The sound unit takes a connection from the 4QD control unit (green line) to drive the sound in sympathy with the speed of the the loco. The whistle unit has an operation button on the hand controller.

The exhaust smoke generator consists of three timer units, a three way servo operated valve to control the smoke fluid, a fan fitted in the loco chimney and the smoke generator heater also fitted in the chimney. The smoke fluid is gravity feed from a reservoir.

With the loco ignition "dead mans button" on the hand controller pressed L1 and L2 energise from the 24 volt 4QD ignition (black line from the DIN connector) signal. The relays are 12V using the resistors to drop the operating voltage. The purpose of L2 is purely to supply a start pulse to the relay timer L3. The pulse is obtained from the capacitor which when fully charged in time 't' dependent on the time constant of the RC circuit will cause the relay to de-energise.

L1 puts power onto the smoke generator and fan. L1 and L3 together cause the servo driver to open the three way valve to full open from the closed position. When L3 times out and its contact L3/1 opens, the servo driver puts the valve into the throttled position restricting the fuel flow to the smoke generator and thus reducing the smoke output.

So at this point the loco will generate dense exhaust when moving away from rest and then after about 15 secs the exhaust smoke reduces to a running level.

When stopping the loco at rest the ignition signal is removed by letting go of the "dead mans button" on the hand controller. L1 will drop out after time 't' (determined by its RC time constant and back emf decay) switching off the fan and heater, followed by the relay L2 and the relay timer L3 so the fuel valve goes fully closed.

For anyone wishing to make a smoke generator my solution uses a commercial smoke generator "Super-Dampf- Erzeuger" by Seuthe, a home made resevoir and three way valve, a miniature 40 mm x 40 mm PC fan from Maplin, a Futaba servo 16M (an old one I had), the servo driver is a kit from Mircon Radio Control (but the resistors to get the right valve movement were added in place of the kit variable potentiometer), the relay timer is a kit from Maplin and the other componants relays, resistors and capacitors also from Maplin.