Sgt. Howard wrote: ↑Fri Jul 17, 2020 12:09 am
AnotherFairportfan wrote: ↑Thu Jul 16, 2020 9:43 pm
I have always loved the fact that there exists a drill that makes square holes.
Essentially a hollow broach with an internal auger bit- it takes a specialized drill press to run it. Very handy to those who make spoked wooden wheels.
There's another type than can be used with a hand drill {with an attachment, apparently}, though i suspect it may be a tad difficult to control.
I ran across a mention - and a brief explanation of how it works - in an editorial by John W Campbell jr in
ANALOG about 1960; so, as soon as square drills came up here, i went looking for information
It's a Reuleaux triangle {the simplest constant-width figure other than a circle - the shape of a Wankel engine rotor) made concave in three places to allow for unobstructed corner-cutting {and discharge of swarf}. It actually makes slightly rounded corners, but that cn be cleaned up.
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The first time i came across a mention of the Reuleaux triangle, was also in
ANALOG in about 1960 - a story by Poul Anderson called "The Three-Cornered Wheel", in which stranded human space-travelers need to move a Very Heavy piece of machinery from a spaceport hundreds of miles away from their ship. They have no powered equipment capable of the feat, either at their ship or at the spaceport.
The natives, who have had very little contact with humans, are willing to supply any amount of muscle to move it - but dragging it along the ground just won't work
Okay, says the human captain, we'll just make rollers out of trees - shaped like this... And their native contact panics.
In their religion {it's a theocratic society} the circle is sacred, and only priests are even allowed to
seecircles.
{Yeah - i know - ridiculous, but Anderson manages to spout enough bafflegab to get the reader to suspend disbelief}
Well, of course, they make Reuleaux rollers, which will work just like round ones {for certain values of "just like"}, and the machinery gets to the ...
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In 1975 Anderson was Guest of Honor at the first RiverCon in Louisville. Sitting around in the convention Hospitality Suite, a bunch of fans, Anderson, his wife and Gordon R Dickson, who'd come along with them, engaged in a wide-ranging discussion of Stuff. Somebody mentioned "The Three-Cornered Wheel", and there was discussion.
Finally, i said, diffidently, "It wouldn't work, you know."
Karen Anderson said "Yes it would! He made one and it worked when he rolled it on his desk."
I allowed as how it would.
On the desk top.
Which was hard.
And the roller wasn't heavily loaded.
Now imagine using a bunch of them as rollers under a thing that weighs several tons.
On a world with no - zero, zip, nada - paved roads?
Moving a Very Heavy Object?
Round rollers would work; Reuleaux rollers wouldn't - because every time one turned to the point where one of the vertices was down, the weight on it would sink it into the ground.
Moment Of Silence
Anderson and Dickson looked at each other.
Gordy grinned.
Anderson said "Son of a bitch! Fifteen years since that story was published and this is the first time anybody's pointed that out!"
