Workshop – EMD SD20 (rebuilt SD7/SD24)


Noah Hofrichter, CC BY 2.5, via Wikimedia Commons

About the Prototype

The SD20 is the product of a rebuilding program by the Illinois Central Gulf’s Paducah Shops as a conversion from the EMD SD7, EMD SD24, SD24B (cabless), and EMD SD35 locomotives. The program involved rebuilding the 567 engine to 645E with 2000 horsepower rating, eliminating the turbocharger if equipped with one, upgrading the electronics to Dash 2 technology, and adding cabs to the B units. A total of 42 units were rebuilt. Original heritage of the rebuilt units was 3 Union Pacific SD7s, 4 Union Pacific SD24s, 10 Union Pacific SD24Bs, 21 Southern SD24s, and 4 Baltimore and Ohio SD35s. Many of the units to be rebuilt were purchased from Precision National. Three of the ex-Southern SD24s wore Precision reporting marks. The locomotives were rebuilt between August 1979 and December 1982. Road Numbers assigned were 2000–2041. Unit 2041 was the last Paducah rebuild.

(Source: Wikipedia:

The Model

I started this build by blocking out a basic model using the illustrations from Michael Eby (Trainiax) as a reference, in addition to taking measures from an Atlas SD24 high hood and a Proto2000 SD7 High Hood unit. Those two engines will be my donor engines.

Blocked Out Shell, with first details added (steps, Anticlimber, brake lever)

So far the model is still missing detail. The side sill hasn’t been worked on, low hood detail is missing, the cab obviously isn’t there either yet, but I started adding the long hood detail, new fans and stacks.

Now there is a cab. I still havn’t worked on the side sill and the low hood. Further details may include an A/C unit on the cab roof, a K5 horn, removal of the low headlight, added ditch lights and possibly rock lights instead, a snow plow and more.

As this is a very custom unit, I will also add snow shields over the air intake behind the cab and possibly a winterisation hatch above the first radiator fan.

BC Northern Rail – EMD SD 20 – 3D printable shell

The model now has snow deflectors, ditch lights and preliminary rock lights (BC Rail style), as well as a snow plow and sun-shades. I added a sand-filler-hatch and high headlights. No handrails yet, as these will not be 3D-printed but wire-bent.

The SD20 shell is nearing completion. I’ll try to mock up some trucks for a better render.
Same Model as above but with some very simple trucks (I need to cut out the area behind the pilot)

Offering 3D printed shells or the STL files for purchase

This model prints okay on an FDM printer at the moment, except for a very few optimizations I have yet to implement. The Long Hood wall thinckness could use another .4 mm for stability.

The long radiator frame at the rear has three posts, but the smaller 1st and 3rd post won’t print. Maybe, that part would be a great separate detail along with the griles mesh structure.

The cab is now a separate part.

I found this type of model on etsy for a lot of money, as apparently it is the only one available for model rail roaders at this time. So I’m thinking about offering either the file or a printed model via shapeways or another fulfilment service if there is some interest.