Percy shears a crank pin

With Percy’s continued resilience to poor alignment, my approach will be to continue to replicate the construction of #10 and #622 until I can make it fail in the same way.

This week, I turned some 3 mm axles, having no such stock material in my collection. It turns out to be harder than expected to maintain an accurate diameter over the course of 22 or 23 mm because the metal would rather deflect than submit to the cutter. It also turns out not to be 3 mm that Percy requires, but slightly less, and so I wound up discarding the first set.

As the axles were roughly 2.95 mm, I was a little surprised that the wheels split when forced onto the axles. I had expected them to be snug due to the thickening of prints on the Mars. However, I’d expected that to simply make up for the under-sized axles.

I mounted and quartered the wheels with my GW Models wheel press, and they ran fine from the start. I then ran Percy back and forth at full speed to see if I could break the friction fit on the axles and throw a wheel out of quarter.

Looking through the spokes, it doesn’t appear that I did. However, after several minutes of fast starts and stops, one of the crank pins did shear off. Does this mean that there was some force applied? I don’t know, but I will return to the lathe to find out.

2 thoughts on “Percy shears a crank pin

  1. If you’re playing, around try turning long slender parts from larger diameter in one pass with a very sharp tool. I use brazed carbide when I do this but freshly honed HSS will work on free-cutting materials. With practice you can get good diameters due to the much more rigid workpiece. I tend to turn N scale axles from 3/16″. You might be able to make it from 1/4″ with HSS but I’d probably do it in two passes to the half way length and then two further passes closer to the chuck.

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