It has been a bit since the last project update since I have been printing all the parts for the first car.
I think that the current design works really well, but the length of the car could maybe be shortened a little bit so that the rotational limits are a bit tighter. I had some issues while assembling the design which led me to make a few changes that I will go over individually.
Zero Car:
I printed the zero car and found that the part that allows for roll rotation (which is hidden from view in the photo) would not print properly because its shape was too rounded and would not have enough surface area on the printer's build plate. To fix this I made the part slightly larger and flattened the top and bottom of the part to give the printer a flat surface to start from. I also found that when mounting the zero car, the front was sitting slightly lower than the rear, so I had to adjust the semicircular part to have a lower mounting point for the bogies. This allowed the front of the car to sit slightly higher and is now level with the rear.
Chassis Spine:
I found that for the zero car to be mounted to the front of the car, the best way would be to mount it to the spine in some way. I came up with the idea to house a bearing inside the front of the spine in a way that still allows a bolt to go through it to secure the car in front. I initially came up with a four-pronged design that pinches the bearing from the corners of the spine, but that did not print and I couldn't find a way that it would be feasible. I decided to scrap that design and instead pinch the bearing between the spine and the panel for the floor. This reduced the geometry to 2 curves cut into the spine and floor panel that wrap around the bearing from either side with enough force to keep it in place. I wanted to use superglue to hold the 2 parts together, but realized that if I changed anything it would mean I have to reprint the parts and lose a bearing in the process since it would be hard to remove. To fix that I decided to use a bolt which you can see in the center of the floor panel in the photo.
Seats:
The seats were difficult to figure out, not in terms of printing, but in terms of assembly. I wanted to hide as many bolts as possible, so the geometry of the part they are mounted to is designed mostly for that purpose rather than function. For the rear block, the bolt sits between the two seats and goes through the chassis holding the yaw axle in place as well. This reduces the hardware for the entire rear of the train to a single bolt, which means lower cost for each car. The front seats sit slightly closer to the center, so a bolt would not be able to fit between them. Because of this I tried to hide the bolts beneath the seats themselves. This presented a challenge in assembly because once the seats were mounted to the block, the bolts that mount the block to the chassis were unreachable. I fixed this by moving those bolts to the underside of the floor panel and having them screw into the block from below. This is also beneficial since I believe I may have to put some control surfaces on the bottom of the train to interact with brakes on the track, so those bolts can be used to mount those surfaces to the bottom of the chassis
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