Adapting chainrings to Ekar

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NickJHP
Posts: 462
Joined: Wed Feb 14, 2018 2:22 am
Location: Canberra, Australia

by NickJHP

I bought a set of Ekar components, less the crankset as I already had several spare cranks. Measuring the Ekar chain gave me 1.9mm for the internal spacing between two inner links and 3.4mm for the spacing between two outer links. I had a couple of Hope NW chainrings that measured 2.0mm width for the narrow teeth and 3.6mm for the wide, so the teeth were too wide for the chain to fit.

However, I got some NaOH-based drain cleaner in powder form from the supermarket, dumped a few tablespoons of the cleaner and enough cold water into a round plastic bowl to cover the chainring, and used a spare stainless spoke to submerge the chainring. After a minute I used the spoke to turn it over so that both side got equal exposure, and after another minute pulled it out, rinsed with water, and checked the tooth thickness. It needed a further minute on both sides before the tooth thickness had been reduced to where the chain fitted. After rinsing off the NaOH from the chainring, drying it, and scrubbing it with 0000 steel wool, there was still a slightly black sooty deposit from the alloying elements in the 7075 aluminium, but 15-20 minutes of simmering in a saucepan containing some cream of tartar and white vinegar in water loosened that sufficiently for the steel wool to get the chainring almost perfectly clean. A secondary advantage is that the de-anodised chainring is an almost exact match for the aluminium crank I installed. The treated chainring on the left originally looked identical to the one on the right.
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p.s. Do this procedure outside, as it gives off some unpleasant fumes while the chainring is in the solution. And the time needed will vary depending on the strength of your drain cleaner (the stuff I bought claimed it was 54% NaOH), how much of it you use, how much water you dissolve it in, and how much thickness needs to be removed from the teeth.

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