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Subject: 
Re: Variations on the "ADDER SUBTRACTOR" ("differtrans" ?)
Newsgroups: 
lugnet.robotics
Date: 
Wed, 27 Jan 1999 21:41:19 GMT
Original-From: 
alex wetmore <ALEX@spamlessPHRED.ORG>
Viewed: 
1079 times
  
On Wed, 27 Jan 1999, Cyberia wrote:
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.

Note that my fathers design (the 2nd one on the page) also allows you to
get rid of having the offset gear on a 2nd level, but you would have to
use two 16t gears and a 8t pinion.  We were trying to reduce the usage
of the pinion gears because they seem to be very inefficient compared to
other lego gears.

One thing that I really like about your layout is that you don't use
any of the fairly rare 1x1 pieces with a hole in them (wonder what the
technical term is for this piece).  Building a strong design around these
can be tricky.

I really enjoy this list and getting to see how many people have
tackled the adder/subtractor design.  It really makes it possible
to get technically interesting designs done quickly, by having mass
brainstorming at this level.

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.

This is also how the design that my father did drives the differentials.
Your first layout on your page is a bit more compact, but very similar.
I have a robot based on my dad's design that I need to take a part and
do a better job of photographing so that people can really see how its
put together.

Glad to see your pictures, and I plan on adding a link to your site from
mine when I get a chance.

alex

--
Did you check the web site first?: http://www.crynwr.com/lego-robotics



Message is in Reply To:
  Variations on the "ADDER SUBTRACTOR" ("differtrans" ?)
 
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 (...) (26 years ago, 27-Jan-99, to lugnet.robotics)

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