Case study
3D printed idler pulley: 2,000 km later
A discontinued bike part, reverse engineered from the broken original and still running after about 2,000 km.
By the Print a Part engineering team
A customer came to us with a broken idler pulley from a retro mountain bike. The original part was no longer in production, and finding a replacement meant digging through second-hand spares with no guarantee it would fit or last. We reverse engineered the damaged pulley, focusing on the details that matter: bearing fit, chain alignment, and overall geometry. The goal was to create a replacement that could be produced reliably using FDM 3D printing and hold up under real riding conditions. The new pulley was printed in nylon and fitted with sealed bearings for durability and wear resistance. What started as a simple repair has now become a long-term test. The printed pulley has covered approximately 2,000 kilometres and is still performing as intended, with no failures or unexpected wear. A practical reminder that 3D printing isn’t limited to prototypes. It can be an effective solution for discontinued parts and small-batch functional components. If you have a hard-to-source or obsolete part, we’re happy to review it.
At a glance
- The problem
- A customer brought us a broken idler pulley from a retro mountain bike. The original part is no longer made, and finding a replacement meant digging through second-hand spares with no guarantee they would fit or last.
- Approach
- We reverse engineered the damaged pulley, focusing on the details that matter: bearing fit, chain alignment and overall geometry, so that it could be produced reliably by FDM printing and hold up under real riding conditions.
- Material
- Nylon, fitted with sealed bearings for durability and wear resistance.
- Outcome
- The printed pulley has covered approximately 2,000 kilometres and is still performing as intended, with no failures or unexpected wear.
Replacement parts and reverse engineering
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