[ExI] A Gedanken Bike Experiment

spike spike66 at att.net
Tue Oct 29 14:11:38 UTC 2013



From: extropy-chat-bounces at lists.extropy.org
[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of Anders Sandberg
Subject: Re: [ExI] A Gedanken Bike Experiment


On 2013-10-29 05:16, spike wrote:

Thanks for that Anders.  I sent them a number of ideas, but the one which
intrigues me the most is an idea I had about filling a tire with a type of
metal alloy which melts at a temperature slightly lower than that of boiling
water.  I may have posted something about that a couple months ago, don't
recall.  A eutectic alloy of tin, lead and bismuth makes a high density, low
melting point metal (about 97C) which you could use to fill a motorcycle
tire.  It would look perfectly normal but would weight over 200 kg for the
front and nearly 300 for the back.

>.I don't know much about bike dynamics, but I suspect the liquid metal
would be tricky to have in the tires. The most obvious reason is that it
would accumulate downwards, ballooning the tire. But if the tire rotates,
then the bulge would tend to be behind the lowest point, and exert a slowing

Dr Anders Sandberg
Ooops apologies, I didn't explain that very well.  The Bismuth Tin Lead
alloy melts at about 97C, which a vulcanized tire can tolerate.  So you melt
the stuff in a water bath, drill a small vent hole in the top of the tire,
pour in the liquid metal until it is up to the vent hole, let the tire cool
to room temperature, freezing the metal.  Now it is a very hard very heavy
tire.  What I want to know is how the bike would handle.  The gyro action of
the front wheel would be increased way more than the factor of 30, for the
radius of gyration would be increased.  So the moment of inertia of the
front wheel would be increased by a factor of over a 100.  That would
introduce weird handling.
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