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TdS Report #54: A Couple of Repairs for Sungo

I've been at each Tour de Sol since 1993 and am continually amazed at the way
the teams solve problems that I would expect would stop them right in their
tracks. Topher Waring told me to check out this pair of stories from Sungo,
which illustrate the point.

Sungo was first entered by New Hampshire Technical Institute in 1993, and while
there have been some major changes over the years, some things have remained
the same. For example, Sungo has always had separate motors and controllers
driving each of the rear wheels. A special circuit coordinates the controllers
so the motors act as if there was a limited-slip differential between them.

Eric Ives was driving when suddenly he noticed he didn't have regenerative
braking in one rear wheel. "That was actually how we figured out there was a
problem since unbalanced regen tried to twist us on the road. So we limped in
on one motor (actually passing cars on one motor)." The evidence implicated
the controller which is at least 5 years old and no longer manufactured. "So
we tore it all apart, and Kurt took out all the modules and circuit boards."
Nick, the electrical engineer on the team, was getting nowhere trying to
isolate the problem, so he went for a walk to try and clear his head. "I was
looking at it with one of the students' father. We found a broken pin. It
turns out it was a power-in/power-out for the Field Effect Transistors. The
FETs were not seeing a signal on one side so the controller was going crazy and
shut off on thermal overload. That actually saved it. Soldering on a new pin
made it all good."

So careful inspection, and a `that doesn't look quite right' observation,
identified a broken connection.

The next story involves a mechanical problem. Kurt Bastian said, "We have
loaded up our car about 600 pounds heavier this year. We noticed a camber
change in the right front wheel, but every thing was fine, it wasn't rubbing or
anything. But the day after the range event in Chesapeake City we noticed it
was worse. We had bent the bracket that holds the spindle to the wheel on. So
we pulled over a mile into that leg, took it off and found a crack in it. At a
gas station we called up a local welder, got it welded up, put it on and made
it in. But it was still bent. That night we heated it up, extremely hot, bent
it into place, and let it cool. It should be strong enough. The mode of
failure now that it has been cooled slowly like that is that the metal is a
little softer. Instead of cracking like it was it will just bend. That means
it is not as dangerous. We won't loose the wheel, but it might go cockeyed and
we'll see it coming."

- - - -
The complete set of Tour de Sol Reports for 2002 can be found at:
The complete set of past Tour de Sol Reports can be found at:
- - - -
The above is Copyright 2002 by Michael H. Bianchi.
Permission to copy is granted provided the entire article is presented
without modification and this notice remains attached.
For other arrangements, contact me at +1-973-822-2024 .
- - - -
For more on the NESEA Tour de Sol, see the web page at
- - - -
Official NESEA Tour de Sol information is available from the sponsor,
the Northeast Sustainable Energy Association (NESEA) at
413 774-6051 , and 50 Miles Street, Greenfield, MA 01301 , and
[email protected] . All media enquiries should be addressed to ...
Jack Groh
Groh Associates
[email protected] email
401 732-1551 telephone
401 732-0547 fax
401 952-0886 cell/pager
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