Gerry Dykstra has made the 3D parts for both engines available for anyone to buy in his online Shapeways shop— Gerry's Early rail Models. Click here to make a visit.

Al Mueller's books, The Mantua General Becomes the Lt. Gen'l Grant, and Building the Yonah: A 3D Printed HO Engine, are now available to buy on the print-on-demand publishing site. Click here for the Grant book and here for the Yonah book.

By making "open source" locomotive kits, the three of us have managed to create projects that an unlimited number of other modelers can take part in. We hope to inspire other specialty modelers to combine their own efforts, take advantage of the new technologies now available, and produce some good-looking model projects that can be shared with others.

This was truly an Internet-facilitated group effort; we all live in different states and carried out our business from home. CAD artist Gerry Dykstra did the heavy lifting in designing the 3D printed engine parts. Master HO engine modeler Al Mueller worked out all the improvements to the Mantua mechanism, test-fit the 3D parts, and literally wrote the book on how to put the project together. I had a small part in the process, researching the engines, making the decals, and getting the books ready for print.
Special interest modelers have new ways to get the models they want: custom 3D printing to get the parts, custom decal printing to produce the finish, and custom print-on-demand books to tell others how they did it. Three of us members of the Yahoo Civil War Railroads Group got together and went that route to produce accurate, colorful, HO models of Civil War engines. The best part is that the 3D parts are now available for anyone to buy, the decal art is available for anyone to reprint, and the how-to instructions can be bought in book form.
Start with the running gear from an existing model
(the Grant) or start from all-new parts (the Yonah)
Models and photos by Alan G. Mueller
The model of the Lt. Gen'l Grant starts with the frame and running gear of the old Mantua General, one of the most popular kit engines from the last fifty years. The Yonah is a wholly new model from the frame up, the modeler using commercial driving wheels from domestic or British sources. Neither engine has been offered from any source in HO before.
The 72-page instruction books include background information on the prototypes, a complete parts list with vendor contacts and prices, the care and handling of the 3D-printed parts, and— for the Grant— how to upgrade the Mantua mechanism to produce a modern, smooth-running model engine. Also included is the art for the decals, how to print them and apply them, along with painting instructions.
The books are complete how-to instruction guides for getting all the parts and building the models