Back in 1993 Bill Johann put out an “extra issue” of The OO Road that was devoted to modern diesels. More than half the issue is OO scale drawings of modern diesels (reprinted with permission from RMC) but the issue opens with four pages of text related to converting HO diesels to OO. As he notes,

due to the dearth of available power–both steam and diesel in OO–I think that it is high time that movement be made in the direction of getting some locomotives that are relatively easy to construct, not expensive and from a reputable manufacturer. We have lots of cars between us and they are not hard to scratchbuild if needed. You can also use large HO cars; they really don’t look too bad.

… Scale Craft, Lionel, and all the rest are gone by now, so we are left to buy, sell, and trade locos between ourselves. Generally, they barely run, are noisy, poorly painted and lettered and reek of technology of the 1930’s and 1940’s. If you have ever compared the running qualities of a OO loco (both steam and diesel) with the same of the 1990s by Atlas, Kato, Athearn or Overland, you will quickly see what I mean.

Skipping forward a bit, as an operator Johann hit on the idea of converting HO diesels to OO.

At this point I decided to research Athearn’s products with a view toward chopping, cutting, piecing, and scratchbuilding Irv’s hood locos, which had perfect OO hood width (6’ [these are overscale for HO in width]), so as to make close to scale OO locos–the “good enough” philosophy. The trucks would be widened to match the OO track gauge.

Johann went all out on his conversions to bring the bodies as close to OO as practical, but his longtime friend David Sacks (who had by the writing of this article had passed on) had another approach.

Dave, on the other hand, decided to just change the trucks and reassemble the chassis and carbody. They were Athearn’s SD45’s. They ran fine–the steam boys didn’t know the difference and the diesel boys were too polite to point the discrepancies out–mainly that Dave’s SD45’s looked like miniatures. Whereas my conversions took 3 months to do; Dave could do his in a weekend!

In the residual from the Sacks estate I found four of these Athearn conversions–two SD45’s, a big GE, and a FM. All are inoperable at this time and won’t be for a long while, if ever, as they need very heavy work and the FM and GE border on parts value only. For sure he ran those SD-45s hard! I am going to try to get the two SD45’s to run again in some form, the bodies are in decent shape (he mounted them all so that they were higher on the frame and close to correct height for OO), but the drives are shot. The first photo shows one of the SD45s and the second photo shows the bigger picture of what is left of these engines; time was hard on them.

Sacks changed all the wheelsets to larger diameter wheels than the stock Athearn wheelses. On the SD45’s they are a mixture of a couple different types of brass wheelsets, including for sure some SC passenger wheelsets, and he turned the middle axles into blind/flangeless wheelsets (he must have had tight curves). The other engines have steel wheelsets of uncertain origin (some are spoked!) but all of those have rusted badly along with other steel parts in the models. The “weathering” easily visible in the first photo is actually water damage.

Looking at them next to a Kemtron GP-7 for sure they look like miniature engines in OO, as does a simple conversion of the FM Trainmaster also noted by Johann. Johann explains though in the following that actually they are close to OO in several dimensions and particularly in overall length and hood width the models convert out to close to OO.

The following are HO to OO conversions that can be done by modifying the trucks only: FM H16-66–Buy an Athearn FM H24-66; EMD SD40 PROTOTYPE #434A thru F–buy an Athearn SD45; GE U23C–now this is a lot of “rebuilding”–buy an Athearn U30C or U33C and treat the unit as a rebuilt U23B modified with 6 wheel trucks. Hey, “This is my great RR”–a quote from Hal Carstens.

He has more tips in the article how to rebuild the drives and the bodies for less compromised models than those done by David Sacks. At the time of the article Johann had converted 14 locomotives to OO for his Watchung Valley, all of which surely today are in better shape than these Sacks Green Brook conversions. If you are itching to operate though and want something that runs a lot better than the drives available in the 1940s or 50s for sure check out Athearn drives, they do work well in OO.