A Cup of Coffee with Rob Tsunehiro.

The other day, when I was returning from the Chris King tour with Andy Newlands and other members of the OBCA, I overheard Rob Tsunehiro, owner of Tsunehiro Cycles talking about a pair of rear disc brake dropouts that he had designed himself and had cnc milled.  This subject was interesting to me because I had also thought about getting some dropouts made to my own designs.  I decided to call Rob a couple of days later and persuade him to meet me to talk about how he went about it.

Rob got the coffees in, and then showed me the goods, which looked very impressive:

Rob's dropout

Designed with the help of CAD software, Rob saw this project through from beginning to end, helped in no small part by the fact that he’s a qualified mechanical engineer, with lots of experience that he’s taken from working for Boeing on their super long-range airliners.

Rob talked to me about how as a youngster he would take his mountain bike suspension forks apart to try to work out how to improve them when their travel would start to stick.

From a sketch..to a CAD file, to a real, tangible object.

Rob explained how it was more fulfilling to produce something where he had total control at every stage, and could feel much more involved with the creation of a tangible product, than when he had to produce a 130-page structural analysis on a single component for an airliner, having to work with several different departments.

Rob gave me some advice:

– When you are designing your piece, wherever possible, try to enable the machinist to use easily accessible machine bit sizes. In the US, the Enco catalog can be useful here.

– Keep material thicknesses to a minimum to keep machining times and therefore costs down.

– Designing a piece that only requires a 3-axis milling machine will make it cheaper and easier to find a machinist who can undertake the work.

– Get blanks laser-cut to just larger than your piece’s ultimate dimensions to minimise machine-time:

These laser-cut blanks have extended lugs to anchor the piece to an aluminium base, and the holes are drilled & tapped. These also work as reference points for the milling operation. I think. If I remember correctly (I never worked for Boeing..).

– Often, it is likely that all is needed is 2D CAD software, and the 3D aspect can be “extruded” from this data.

– A .dxf file might be ok to send to a cnc machining company.

Rob also talked to me about his adventures in the Oregon Manifest Constructor’s Design Challenge, and the perils and excitement of long races over gravel roads carrying a 6-pack of beer on a rack through the Oregon hills..

A Tsunehiro bike took pride of place upon the wall in the cafe at Legare’s Community Resource Center:

..Complete with cnc'd aluminium front rack.

You should go there, they can teach you how to weld or bend motorcycle exhausts.  They serve coffee and bake nice stuff, too.

Thanks Rob, you answered a lot of my questions and filled in a lot of gaps in my knowledge.

Next stop, a tour of UBI frame building school, Portland Oregon.

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