In last week’s post, I shared with you the first steps in the HO Baldwin DT6-6-2000 project and I ended with the image below showing my 3D model of the truck centers which hold the gears in place. You can find the post here. The reason for modeling the truck centers was to allow me to work out how to reposition the gears to allow the axels to be positioned differently. The trucks are asymmetric and I need them the other way around.
In this week’s post, I’ll share with you my solution to solve the issue.
Inside the truck centers, in the original configuration, are 5 gears, as shown below. The green gear at the top connects to the worm gear at the end of the drive shaft. This drives the large blue gear which turns the center and right axels, shown in black. The center axel then transfers the rotation through the three red smaller gears to the left axel.
Because I need to move the center axel to the left, the gearing will need to be rearranged and ideally, reusing the same gears would make sense, but that wasn’t possible as you can see below. By swapping the red and blue gears over, all the axels are connected but there’s a big gap between the green gear and the red, so another gear needs to be added in. The purple gear is the same size as the red. But this configuration has another issue in that the blue gear is too big for space. Looking at the outline of the truck center you can see the shape was tapered above the blue gear’s original position and that would not be possible in the new location. The part would either become too thin and weak or project up and hit the chassis.
So, as an extra gear was unavoidable, I decided to make four extra gears, as shown below, and remove the blue gear completely. The four new purple gears are all the same as the red ones. To allow space for the new configuration of the red gears, the top of the truck center will also need to be extended, but that’s okay as there’s room between the truck center and the chassis.
Both sides of the truck chassis can now be properly drawn with the new gear holes set out.
The four new gears have been modeled inside a cage to make them one printed part, even though they don’t actually touch the cage. This reduces the cost of the 3D print. These parts will be test printed in Shapeways Smooth Fine Detail Plastic material for accuracy.
As well as the trucks I also had to model the Bowser chassis to see if it needed to be modified in any way to fit inside the shell. The green section is the existing circuit board, with an 8 pin DCC socket. The black section is the motor with its two brass flywheels. Everything else is metal.
The shell, taken directly from my N Scale version looks like this. I’ll be refining some of the details as they don’t need to be so big for HO, and replacing some with brass parts, such as the grab irons. I’ll also be making the grills at the bottom of each nose section from a fine brass mesh.
With the shell split in half you can see the chassis inside and it’s a good fit, with nothing requiring modification on the chassis. As the DT6-6-2000 is longer than the original body shell for this chassis I can update the new shell to utilize the original shell and fixing points.
Next week I’ll have some progress on the shell to update you with and once the test truck arrives I’ll share that as well.