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Todd, thanks for the pointer to McMaster-Carr. The chuck on my PhlatPrinter 3 (which uses a Chicago Tools flexible shaft router) is small - 3/16" is the maximum shank size. And they do have a couple 4" long bits, their cutting flutes are just 1 3/8" long. This would not have worked because I need to be able to cut through the 2" in one pass - there is no digital feedback correction and any small error over say 40-50 lineal feet of cutting would cause melting on the smooth shank on the second pass.
I learned this the hard way. I even asked for a quote on custom bits from a local tool maker and they could not find a source for blanks of the needed dimensions.
One detail that will improve the rollover strength that is not obvious, is the driver's seat will be mounted on a vertical strut from the floor to the roof. And the sides are monolithic box beams continuously joined to the floor structure. There are no side doors, and there are 4 pairs of roof pillars - and the hatch door will have at least 5 and maybe 7 points of attachment (2 hinges plus 3 or 5 latches) so it should be pretty well locked in place; which will greatly strengthen the whole car.
I don't know for sure how this first prototype will do in a crash - it is a proof of concept on the aerodynamics and seating and entry door and whether or not an EV can have a 300-400 mile range and still weigh a ton or less. After I build a second one and make improvements, and build others for other people, etc. - then we will have to be concerned with official crash worthiness.
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