There is no question in my mind about the fidelity of Kato HO locomotive shells. The tooling is superb and continues to improve. The downside is the shells are solid so there is little choice in installing a speaker for DCC sound. And on the recent units I modified, the frames were pretty much a road bock to sound routed through the bottom. Even the models with the speaker mounting in the fuel tank are at best mediocre, in my opinion.  The option, for me, is to open up the shell’s roof fan openings in a series of steps.

The first is to use a drill bit to create a hole in the center of the fan. (I am only doing the radiator fans and not the dynamic brake fans as there is generally no room beneath them for a speaker.)

There are several options for the next step which is enlarging the pilot hole to accept the replacement fan. Note, there are differences in the plastic and how it “reacts” to the drill bit. I start small and work up if needed. Care is needed so the surrounding area is not scared.

Another approach is using a fine bladed hobby saw such as Zona. Depending on the surrounding area, it is possible to simultaneously trim all three fans. It is a slow process using light force to allow the blade’s teeth to do the cutting.

The next step is to increase the diameter of the hole to accommodate the replacement part.  I have used round files by hand, very time consuming, and the much faster Dremel. Within the Dremel arsenal are multiple choices. My preference is the tapered steel cutting tip. Is use about 5,000 rpm and light pressure to accurately remove any needed plastic. Any touch up is left to a small diameter hand held round file.

My choice of fans is the $*-inch diameter (plastic) versions from Precision Scale Co, part 3931. I use Formula 560 cement to secure them to the openings after painting them to the appropriate color for the locomotive. In this SD40-2 example, the roof needed a bit of freshening up with the airbrush so I just painted the inside of the fan before mounting.

The GEs were a bit more labor intensive. While the “bat Wings” can be removed for modification, there is still a second top wall to be removed on the shell. Same process though; pilot hole and then enlarging.

Top view of modified  GE fan grill. I used the Detail Associates part2724 for the Atheran GE C-44-9W.

Underside view of GE fan grill.

Needless to say, the difference in fidelity and volume is tremendous with appropriately sized Scale Sound Systems U-Fit speakers positioned to fire the sound upwards.  A final benefit is your wife knows where to find you on rainy days.