Pete Hall has been busy working on HO scale steam locomotive models. He sent photos and details on how he adds a speaker and extra weight to the boiler. Here’s Pete with more.

This began with a task to install sound in a CB&Q Mikado. The tender cavity is small because of the deep coal bunker, so the electronics fills that space and precludes installing my standard 27mm speaker. I decided to install a 691-1291 Bowser twin-sugar-cube speaker in the boiler.