SP Krauss-Maffei Diesel Hydraulics

I've occasionally added brass models to my collection, but I'm happy at this point that there haven't been that many. In general, while it's possible to convert them to DCC, the combination of one-side pickup for steam locos and tenders, or one-side-only pickup for diesel trucks, makes them less suitable for reliable current pickup, and the quality of their mechanisms varies widely among manufacturers. On top of that, we're used to very smooth and quiet operation from later-generation plastic and hybrid models made in Korea, Japan, and China, something brass models have seldom ever achieved.

I have at least one model in my collection that's made me go "hmm", an Overland model of the second, road-switcher style SP Krauss-Maffei diesel hydraulics. I may have gotten this because I thought I remembered seeing these in the San Joaquin Valley, but after studying them further, this was a false memory: according to this site, they were

an order for 15 identical units. They were an experiment in high horsepower diesel hydraulic locomotives that had rather short careers on the SP, being retired by November, 1968.

However, the trip down the San Joaquin Valley where I might have seen them took place in June 1969, so I was a little too late. I probably confused seeing SD45s. Here's a photo of my model, which I believe is one of Overland's last run of their K-M:

So far, it's spent its life in a display cabinet. I took it out for the first time not long ago and tested it on DC. Although earlier Overland K-Ms had the older style zamac gearboxes, this has their later style drive with individual worm and gear drives to individual axles, but even so, it's pretty noisy, much noisier than an equivalent Chinese or Japanese plastic and metal diesel. It also has the disadvantage of right rail pickup from the front truck and left rail pickup from the rear, which means it will be less reliable for contemporary layout running than a mass produced Chinese or Japanese loco.

Most brass models were never made with window glass. This model at least has glass, but while there are headlight lenses in the nose, there's no provision for lighting them. So it looks like beyond adding a decoder, I'd have to add a capacitor plus figure out a way to light the headlights and SP warning lights that wouldn't be a wiring nightmare.

The SP 9010 restoration site also makes additional points about the Overland K-M models: in their short lives of a little over four years, the units underwent a great deal of modification. It looks like they were never quite right, but SP persisted as long as they could to make them run before they gave up. The version in this Overland model is basically the appearance of four final units following a last full shopping they received in 1966-67. These units were 9107, 9113, 9116, and 9120.

The most visible change after this shopping was square shoulders on the radiators that were added to extend the capacity of the cooling system. You can see these on the roof of the model at the mid-point and rear of the long hood. Only 9107, 9113, 9116, and 9120 had these, so Overland's number 9117 on the model is incorrect (as far as I can tell, Overland gave these models random numbers in the K-M renumber series when they were painted at the factory).

However, there were numerous other variations on every unit for features like cab windows, sun visor, horns, lettering, and so forth, so that no two were alike, and no Overland model was ever quite correct for any individual prototype unit. So I'm just on the fence over converting this loco to DCC, especially since if I were to operate it on the layout, it would be subject to general wear and tear, and the model itself is just a little too nice to let that happen. So for now, I think it goes back in the display case.

On the other hand, Piko has announced an HO version of the original, cab-unit style SP K-M diesel hydraulics. I may well go for this, as it eliminates all the problems to trying to convert a brass model for DCC, with sound to boot.