This is a 1/32 scale "12 ton coal wagon" for G scale (45mm) garden railways.
It is a remix of the open freight car 1:32 scale gauge 1 by UTJTrain, but because I work in 123D, I had to re-draw some of the parts.
The body prints well if you use PLA, but attempts to print in ABS so far have resulted in bad warping.
Before assembling, make sure that all clearance holes are the correct size, and drill out if necessary to get smooth movement.
The wheels can be either Spoked or Solid, and are set on 3mm stainless axles, 68mm long. You can fit longer 76 axles and fit directly to the side hubs, but then the "brakes" on the swinging arms will bind unless the swinging axles are fixed. The wheels are also the same size as those on LGB / PICO /Nuquida carriages so you can use their wheels if you prefer.
I have a separate thingyverse entry for the wheel design, which includes an assembly / alignment tool, but have included the wheels here.
The swinging axle takes standard LGB couplings, but I have also designed some magnetic sprung versions that you can print. Use three 2mm long by 2mm dia magnets in the loop, and one 2mm ling by 3mm diameter magnet in the hook. Adjust their distance apart so that the "tension" is not too strong and check that the hook can displace downwards easily when coupling. Some filing of the slotted hole helps. The couplings use 13mm long #4 pan head screws, (as do the swinging axle bosses.).
The buffer bar is screwed to the body and side axles with 10mm long 1.7mm pan head screws.
The side hubs were supposed to be symmetric, but the end holes to fit the buffer beams are not quite the same at each end, so it is better to print all four rather than try to duplicate the ones that look the same. When fitting, look closely at the buffer beam and you should see which part fits where. You can also add some more 1.7mm screws to hold these hubs in place, but I found the tabs were sufficiently tight that extra screws were unnecessary.
The photo shows two PLA printed wagons, with an early, and much less successful, ABS version in the background
use supports to make sure that the overhanging swinging axle coupling part is supported, Also the side hubs have a small cut away and print better with supports.
PLA seems to be essential for the body, or else you will get warping.
I used 123D to design this. Some parts translated to solids easily, but I found it easier to redraw things like the swinging axles.