Yesterday I tried posting a few more pics of custom parts that went into building this engine. Then my browser crashed 
. I like experimenting and trying different solutions where applicable.
Using optical devices as chuff triggers has been discussed in the past but installing them in most steam engines is rarely easy or reliable. Usually little of the backside of the driver is visible due to the frame design or other components in the way.
This engine lent itself to that approach. The wheels are held on with screws so can come off and be modified and there was plenty of space on the frame to mount a detector.
Here are the drivers before and after. The back was blanked off using .005" styrene and Avery Label material was used as the reflector. The data sheet for the Optek OPB607A sensor actually specified Avery Labels in its examples. Works well and has not skipped a chuff yet. I may even use smaller dots to give better smoke puff definition.
Then I had to make a bracket to hold the optical sensor.
Here is a pic of the bracket installed with sensor (center left) along with the fan smoke bracket made last year. Circuitry to power the detector and drive the fan motor is below smoke unit.
Also I had to make a bracket for the program/run switch and smoke on/off switch. This is mounted to the back of the frame in the pic above.
Pete
