In last week’s post, which you can find here, I shared with you the first images of the new HO Scale Baldwin DT6-6-2000. I’ve now had some time to test it out and this week I’ll share with you some of the results.
As you may remember the new 3D printed shell fits on top of a Bowser chassis taken from an Alco C-630, as shown below. The chassis is fairly standard and has two mounting holes at each end. The shell fitted perfectly over the chassis once I’d poked the wires up inside, with the exception of the lugs at each end. They were about 1/2 mm longer than expected, or rather the shell was 1/2 mm shorter than drawn. This can happen and is called ‘shrinkage’. When a 3D print, at least one printed in this material, comes out of the printer it’s heated to make all the support material liquefy and run off, then it’s left to cool. This is a very precise system and shrinkage can occur if the timing of the heating and cooling is not spot on. All the prints do it but the difference is normally negligible. But, given the size of the print, 1/2mm shrinkage over the whole length is very acceptable, and I’ve adjusted the 3D model to allow for this.
The most disappointing thing was the locating hole for the connecting bolt. If you remember I designed the shell to have a hexagonal hole to receive a nut that could be glued in place, as shown in the image below. Sadly I didn’t allow enough tolerance; it’s too tight a fit for the nut. For this particular shell I can file down the nut to make it fit, but for the actual shell that will be for sale I’ve made the hexagonal hole bigger.
The other hole close by is the off-center mount for the tiny motor that will power the Kadee uncoupler. This was a tight fit but went in exactly as planned, although I’ve now added a little more tolerance. I think the reason for the tight fit here was 3D print residue inside the hole, but it’s nearly impossible to get into the hole from inside the shell to clean it out so increasing the size was easier.
My cable loops also worked very well; using a pair of tweezers I was able to thread the wires through the loops which will keep them clear of the drive shafts. I also fitted an LED which will be for the headlight; I used a yellow one just so it shows up in the photo. The final one will be clear and emit a warm white light.
From the front the LED pokes though the 3D printed hole in the headlight and allows a lens to be placed in front if required.
The coupling didn’t fit perfectly the first time as I managed to get the hole for the Kadee in the wrong place; possibly I originally measured the wrong coupling? However, I was able to trim the coupling so it slid back a little further, and secured it with a screw. It works well and is the right height. I haven’t tried it yet with the motor to make it powered.
The cab interiors and horns were easily snipped off their sprew. The tail on the bottom of the cab interiors allows them to be held with tweezers when fitting inside the shell.
The horns fitted right in, but having them loose allows for different horns to be fitted. I’ll probably add different horns to the sprew, giving a choice
The cabs fitted perfectly as well; below you can see one cab fitted. The recess for the cab light is just about visible where the other cab goes. I haven’t tested these but as they’re so small I have no doubt they will fit.
With both cabs fitted you can see the backs of the cabs form the same width as the channel in the shell, allowing the chassis to fit in.
The crew are now visible through the window. The N Scale version also has this, but in HO it will be much more visible.
Of course, test fitting is great, and I’m pleased I did it so I could fix the few issues that arose, but the real test is how does it run? Last week I took the locomotive down to the workshop and ran it on a HO layout we’re currently building for a customer and it ran perfectly. I managed to get a few quick videos.
For the test I simply fitted a basic DCC decoder without any setup and ran it. This also has the 3D printed truck centers and gears so the trucks are rotated the right way for a DT6-6-2000.
The next stage now is for the brass to be drawn and etched and to test fit that, but with the 3D print issues resolved and the shrinkage accounted for on this scale, I think you’ll agree that this locomotive is very nearly ready to be made available.