A quick lunchtime project today. I bought a few USAT tank cars a while back, and two of them had damage where the truck mounts to the body, making them pretty wobbly. I filed the area clean, and printed a new mount point. Works great.
Original:
Replacement:
Eric: You may get some requests for your little fix. Paul
Eric, the bolster was wider side to side and thinner fore and aft for a reason… you have changed it to a flat platform. I wonder your reasoning on this.
Greg
I didn’t give that much thought. The Kadee truck that I’m using flexes on its mount point, so I think it will work. I could easily curve the top of the mount, though. My motivation was primarily surface area for strength.
Thinking more about this, I see how the original design interacts with the stock truck. The truck is loose on the mount when the screw is tightened so the shape of the mount determines its freedom in each axis. The Kadee truck comes with its own center pin that clamps tightly to the original mount, defeating this functionality, and the truck itself is designed to flex on its own mount instead. This is all I was thinking about when I drew this up, but you’re right that it wouldn’t work well for a stock truck.
Eric, Are you using the factory USAT plastic Bettendorf truck with projecting ribs on its bolster - like the one shown in the middle of the below illustration? (The small contact area of the ribs would serve to reduce friction when the truck pivots, particularly if rubbing against a rounded, thinner fore-aft area type car bolster)
-Ted
Ted, he said he was using KaDee trucks.
I think there may still be an issue with friction as it rotates. Maybe I’ll try this instead.
David Maynard said:
Ted, he said he was using KaDee trucks.
David, you are correct - I missed that.
As to using a Kadee Truck,
For the cars I mount Kadee trucks on, I chose not to the use of the adaptor kit base plate intended by Kadee because I want keep a car’s height from the railhead to a minimum for more prototypical appearance since cars tend to be too high from the railhead. This also reduces the height of the coupler box spacer when body mounting Kadees centerset couplers.
Many USA Trains and AML cars have a rounded floor bolster from which a truck pivots against (thereby minimizing rubbing area) so when the Kadee truck’s side frames twist by design for equalization (while truck pivots on twisted track) there should less friction and minimal affect on operational dynamics.
-Ted
I went with the new, rounded design, and used the USAT bushing without the accompanying shim. The car seems to have an appropriate amount of motion in each axis relative to the truck, with little friction. Each coupler required a single 1/16" shim, which is less that they required with the original trucks. I’m happy.
I updated the file on the thingiverse link.
Thanks for the suggestions.
Eric…
With what I have seen from your posts I think you should take you hand at scratching up some cars instead of modding what is available unless you have other intentions
I’d like to try that! I bought these tank cars on eBay, and they were damaged when they arrived. I got my money back, but the seller didn’t want them returned. So I’m just trying to get them rolling. I do have some ideas for whole cars.