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New KR-1 Chain Guards (Parts 550201296) appear to have disappeared off of the face of the earth and nothing’s worse than trying to restore or maintain a bike and when you can’t find the parts you need.
These Chain Guards used to retail for about $40AUD and thinking about it that’s pretty reasonable considering the cost of the materials. High volume is certainly favourable in the manufacturing game.
After studying a couple of Original Equipment Manufacturer (OEM) samples it was clear that some improvements could be made to the original design. Both of the guards fitted less than perfectly. The width of both was 0.5mm too short on each side causing the edges to flare over time and at the round end not enough clearance for the swing arm welds that was clearly done by hand after seeing welding pattern irregularities across 4 different swing arms.
Looking at the material a fair guess would be that this part is made of Thermoplastic polyurethane. This stuff is pretty awesome and used widely in the automotive industry. Thermoplastic polyurethane has great properties and would make sense for this very purpose. It’s oil and grease resistant and that’s precisely what you need being near a chain that flicks out chain lube. The high resistance to abrasion would help it survive if/when the chain comes into contact with it and it has great elasticity and really strong.
Redesign took a number of weeks with a series of prototypes that were improved over and over again.
The attached images show the comparisons between the Original and reproduction part and also images of the fitted product.
Parts Worked On:
- Swing Arm