I recently retired a 16t DA cog after significantly wearing the teeth and remembered this photo, so thought I’d repost it with a question.
Nath, how’s the cog holding up after 2 years of use?
Heh, you can see me in the tip of the lower teeth.
that was (and still is) the coolest get well present i’ve ever seen!
nice to dig it up for all to see again!
i still have a cog from you on my bike back home - but it hasn’t been ridden for two years. when i get back though, i hope to put at least two years of riding on it in two weeks.
n
18 months of regular riding with only slight wear on the teeth. Plenty of kms left in it yet 
Nick: Lynn from CTA was the generous donor/manufacturer of this cog, not I. Lats did the vector artwork. All I did was collect some money and organise the laser etching.
It’s still looking damn good, the etching is holding up really well, especially considering it was so hard to do (cog surface hardness is 60 Rockwell C IIRC)
Is that super-nerd for ‘really damn hard’?
Is that super-nerd for ‘really damn hard’?
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6061-T6 aluminium has a Vickers hardness (HV) of ~107, 60Rc ~= 460HV.
4130 Cr-Mo steel can be hardened to ~45Rc and Tungsten Carbide is >80Rc.
So, yeah, pretty damn hard.
:? I think I’ll stick to learning about Rickets disease, OTC and Refractory Epilepsy and such!