I got something of a shock when I saw the current price of Broad Gauge wheel-sets so that started me thinking about 3D-printed wheels. I realised that I wouldn’t be able to make metal rims but it could be a way of making basic wagon wheels in bulk.

 

Many early GWR wagons used the form of wheel ascribed to Losh and Bell, in which wrought iron spokes were cast into the hub and wrapped around the inside of the wheel rim, to give the characteristic appearance shown in the following illustration from D.K.Clark’s ‘Railway Machinery’(1855)

 

 

Losh Wheel Drawing

 

I scaled the drawing for a model of a 4’ diameter wheel and then traced the outlines, to create a DXF format drawing.  I extruded the spokes and rim to a depth of 2 mm and the flange to 0.5 mm, using ‘Fusion 360’, and printed the result with my E 180 printer.

 

 

3D-Printed Wheel on Printer Bed

 

As usual, there were lessons to be learned.

 

My first printed wheel had a gap in the side of one of the spokes, which turned out to be due to slight misalignment of one of the oval cut-outs within the spokes, by around 0.1 mm. This was sufficient to make that part of the spoke too narrow to be rendered by the ‘Cura’ software.  Adjusting the positions of the relevant surfaces in ‘Fusion 360’ corrected this problem.

 

Afterwards, I realised that this error could be observed on the ‘Layers preview’ screen within the ‘Cura’ software. A lesson to check the preview carefully before committing a model to print!

 

 

Layer Preview showing Printing Error

 

Once the spokes all appeared correct on the single print, I made an array from the drawing and printed a group all together. As each wheel took only about 4 minutes to print, I had a batch of nine in around half an hour, with no further input needed on my part.

 

 

Array of Wheels on Printer Bed

 

I was surprised to find that there was still a stray chord of filament between one pairs of spokes in every wheel that was printed – all in the same place – even though I had checked the ‘print preview’ on the ‘Cura’ screen.

 

The ‘penny dropped’ when I selected to show the paths traced by the printer, when moving from one part of the print to another. It was clear that there was a cluster of ‘paths’ causing stray filament deposition at the offending place. It was fairly easy to remove with a scalpel blade although the PLA thread is remarkable tough, even when in fine strands! Another lesson in checking before printing.

 

 

Printer Travels in 'Cura' Layer View

 

I found that this effect could be reduced or eliminated by moving individual items on the printer bed and checking the preview before printing.

 

Now I have a handful of wheels that just need fitting onto axles. I am pleasantly surprised by the robustness of the finished wheels and by their smooth surface finish, especially considering that mine is a relatively low-cost machine.

 

3D-printed Wheels

 

EDIT:  As I mentioned in comments below "I could also try making a pair linked by a hollow shaft, which could rotate around a fixed axle.".  I have now tried this approach, with a clearance hole along the shaft, which I made half the back to back length.  I gently tapped the axle through the shaft to fix the first wheel and then tapped the remaining exposed axle into the second wheel until the halves met - instant alignment!

 

 

Mike