A few months ago I was asked by a fellow modeller, through one of the model railroad forums, if I could draw and design a 3D printed shell for a Baldwin DT6-6-2000 Center Cab. So in this post I will show you what this locomotive is and how the design is coming along.
In 1946 the Baldwin Locomotive Works, who were already manufacturing small switching diesel locomotives, set about designing a locomotive with more power to be used as a transfer locomotive. Its primary function would be to transfer rolling stock from one freight yard to another locally so it needed the power of a road locomotive but not the speed. It also needed to maintain the visibility and benefits of the smaller switching locomotives. Baldwin’s answer was the DT6-6-2000 Center Cab.
Baldwin’s naming convention, DT6-6-2000, refers to several things: DT stands for “Diesel Transfer”, the first 6 refers to the number of axles, the second 6 refers to the number of axles powered by traction motors and the 2000 refers to the locomotives horsepower rating.
The locomotive, as the name suggests, has a centrally located cab allowing the engineer to see both ends which makes it easy to couple to rolling stock at either end. Road locomotives normally had a cab at one end with windows only facing forwards, they would either need to be turned at the end of the line or run in pairs with another road locomotive facing the other way.
The DT-6-6-2000 is powered by two diesel engines, one for each three axle truck. The design was effectively two switching locomotives back to back sharing one cab. The original prototype had a pair of 8 cylinder normally aspirated diesel engines (Type 608NA) but all the other production locomotives had a pair of 6 cylinder turbocharged diesel engines (Type 606SC).
Several railroads tried the locomotives and a total of 46 were made between 1946 and 1950, each with slight differences as the design improved. There is only one left now and it is preserved at the Illinois Railway Museum in Union, Illinois. The Elgin, Joliet and Eastern Railway purchased the most ordering 27 in total but for me I like the 6 ordered by the Atchison, Topeka and Santa Fe Railway mainly because of the fantastic black and white striped paint job, so for this model I am going to base it on AT&SF No.2601.
(The three links above are from http://www.snowcrest.net/photobob/ where you can buy prints of the photos)
As this is a locomotive that has never been mass produced in N scale before, not even in brass, there was no easy place to start. The shell will be completely 3D printed so that is not a problem, but as to what power chassis to use we had to do some digging around. The biggest problem with the power chassis is the trucks, unlike most other diesel locomotives the axles in the trucks are not evenly spaced. The DT6-6-2000’s first axle is spaced further apart than the other two as you can see in the photo links above. The answer came in the form of an Atlas model of an Alco C-628 as pictured below. ( The C-630 will also work as they have the same chassis).
The Atlas C-628 is a very good running model but the reason why this locomotive is perfect is because of the trucks as shown below.
On the C-628 they are the same as the DT-6-6-2000 in that they are not evenly spaced however they are facing the wrong way and the truck side frames are completely wrong for the DT-6-6-2000. This is not an issue because the side frames are only cosmetic and pop off as shown below.
Also because of the way the trucks have been designed they can also be removed and re-installed backwards as shown below.
The chassis is now ready to be used for a DT-6-6-2000. As the chassis is a bit shorter than the DT6-6-2000 I have designed the shell to fit onto it without any modifications, except for turning the trucks around. The Atlas shell also has several areas designed to receive the lugs on the chassis so that it simply clips on and the DT6-6-2000 shell will be the same. The couplings will be body mounted Micro-Trains.
The 3D model for the shell is almost finished and below is a screen shot showing the progress.
The interior of the cab and trucks still require modelling and there are some small details to be added around the shell. The hand rails look very chunky because they are modelled at the smallest diameter that can currently be 3D printed however they will be printed as a separate part so wire rails can be hand made if required.
Hopefully I will get the model finished over the next few weeks and get a test print ordered. In a later post we will look at fitting the shell to the chassis and finishing up the model.