Subject:
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re: Variations on the "ADDER SUBTRACTOR" ("differtrans" ?)
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 27 Jan 1999 22:16:08 GMT
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Original-From:
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Duncan Stewart <dcstewart@!AvoidSpam!longviewgroup.com>
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Viewed:
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1050 times
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I am grateful to one and all creating these 'Variations on a theme' for the
differentials! I saw Leo's initial design,
ordered the extra differential from S&H (actually, it was a Christmas gift,
lucky me!), and assembled it. Nice function, but
much bigger than I had anticipated. This slimmed-down version is very clean
- - can't wait to implement it.
I do have one question, 'though - - - I see the two shafts extending from
the bottom of tan1.html, but I am not sure where
the motors attach as opposed to where the 'output' shafts will go. Once I
put it together, I'm sure it will make more sense, but if you
can spell it out, I think it would be very useful.
As for the previous comment re: the 'popup' boxes, it is a pain to add a
simple page (such as your excellent enlargements) and
then you go to view it and the popup appears. I just cut their 'buttonbar'
from the index page and paste it onto the bottom of
any subsequent pages; it takes a few extra minutes to activate it, but it
does lower the annoyance factor. I think your photos (and ingenuity!)
more than make up for the inconvenience.
Thanks again!
Duncan Stewart
Stewarts@stewarts.org <mailto:Stewarts@stewarts.org>
Hi, fello legoroboticists.
My son Michael has a web page via Geocities, where we decided to
begin to
assemble various lego oddities to share with other enthusiasts.
Much interest has centered around the "adder/subtractor"
transmission, a
design that I first saw on Leo's lego page
http://carol.wins.uva.nl/~leo/lego/diff.html
<http://carol.wins.uva.nl/~leo/lego/diff.html> . Later, another two
variations appeared at Alex Wetmore's site
http://www.phred.org/~alex/lego/ <http://www.phred.org/~alex/lego/>
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The common issue with two of these designs is the use of an "offset"
intermediate gear on one side to tie the two differential shafts
together
out of phase. This gear is mounted at a different level from the
common
centerline of the differentials. In this way, stress forces these
gears
apart, concentrated where legos are the weakest (the interface
between
bricks). Alex's design (the first one on his page) seems to have not
only
overcome this, but has the diffs closer together. This is cool, but
there is
a disadvantage. It is not possible to mount the motors directly over
the
diffs at that close spacing.
The "tandem" design as we have termed it, is arranged such that the
motors
can drive the differentials directly using proper gearing, and they
can
mount above the diffs for a very compact drive system.
Anyway -
The variations found here
http://www.geocities.com/SouthBeach/Surf/6112/
<http://www.geocities.com/SouthBeach/Surf/6112/> are
optimised to eliminate the offset-gear stress point. Two variations
were
created, one which minimizes the distance beteen the differential
mainshafts
(this I called the "adjacent" variant), and one that minimizes the
width of
the overall transmission (this I called the "tandem" variant) and
makes for
compact motor/transmission integration.
The original photos are quite large, so we reduced them various ways
to help
minimize bandwidth for the casual observer. The "freakin' HUGE"
versions are
also there, for the serious gearhead who wants to see just how dusty
my lego
pieces have become over time. :-) :-)
I must say I had a lot of fun doing this, but I hate the term
"adder-subtractor" (no offense to Leo). We should coin a shorter
term for
referral to this design and it's variations.
Differtrans ? Difftrans ? any other ideas ?
--
SeeYa !
------------
Jim
----------------------------------------------------------------------------
Hello... Is this thing on ?
--
Did you check the web site first?:
http://www.crynwr.com/lego-robotics <http://www.crynwr.com/lego-robotics>
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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