Crankshaft Teststand

A simple test stand for a 1960`s motorcycle crankshaft.

Heinz-Peter Liechtenecker

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Description

While restaurating an Austrian classic, a PUCH 175SV motorcycle, introduced to the market after WW2, the repair-manual introduced my to the topic of crankshaft measuring. So, I am more the electronics guy with some basic mechanical skills due to my studies, so there where a lot of new information for me to cope with.

However, when asking local mechanics to help me out with ensuring that the crankshaft of my motor Is still useable, they often told me that it will "just fit" - or any mechanical missfit will go away by time, grinding itself in - something not acceptable for me.

When looking around for a cheap, but precise enough test stand to do the tests, there was not a lot of information available online. So I decided to create a simple test stand with 3D-Printed parts and two dial gauges.

I know - true professionals are gonna hate - but for my purpose it is accurate enough and way better than doing no measurement at all.

Details

There are many videos available on YouTube telling you how to check such an old and simple crankshaft, to sum up you have to ensure:

that all bearings are still okay
that the crankshaft stays within tolerances when turning around

I checked the bearings by the "noise" check - ensuring that there is no metal-like noise when hitting the crankshaft. This noise would indicate a lot of tolerance in the bearings itself, something to avoid. Next test: Make sure that the crankshaft stays within limits to ensure roundness. And for this test, you normally need a specialised crankshaft test stand.

The crankshaft sits on four bearings, allowing free rotation to test it with the measurement gauges.

As these are quite expensive, I decided to give 3D-Printing an option here - and the results are promising. I will use my double checked crankshaft to restore the engine.