Newsgroups: comp.robotics
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From: carice@netcom.com (Chuck Rice)
Subject: Re: please post information on homebrew robots...for all of us!!
Message-ID: <cariceCF8KAq.HvF@netcom.com>
Organization: NETCOM On-line Communication Services (408 241-9760 guest)
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References: <20OCT199316484415@rigel.tamu.edu>
Date: Thu, 21 Oct 1993 07:18:26 GMT
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BURNS, THOMAS EDWARD (teb0958@rigel.tamu.edu) wrote:

: thanks in advance.

This is something that I wrote a while back in response to a question
about LEGO bases. It was posted to the robot board, so if you saw it
there, you might want to skip this. I hope it is the kind of information 
you are looking for. -Chuck-

-----------------------------------------------------------------------

If you have access to a drill and hacksaw, you can build a very nice base
out of surplus motors and things that you can find at most any hardware 
store. 

I started by ordering 2 12volt motors from American Sicence and Surplus's
August issue, item #20290. They said that they had about 200 of them at the
time. Their phone number is (708)982-0870.

The motors cost $12.50 each, but they are a perfect starting point for a
base. They look something like:

        ##
        ##    
        ## MMMMMM         This is the side view. The M's are the motor, 
        ##MMMMMMM         The #'s are the gear box, and the A's are the
        ## MMMMMM         drive axle. They have 6 mounting holes in the 
        ##                gear box. The gear box is 2.5x3.5x9/16. You 
        ##                get 10 inch/pounds of torque at the drive axle
        ##AAAAA           with a 1 amp stall current and 50 RPM at 12 volts.
        ##                The drive axle is flattened and 5/16 in dia. by 
        ##                13/16" long. Starts spinning at 3 volts (7.5 RPM).




        ##############
        #O####MM####O#
        #####MMMM#####    This is the view above rotating the motor toward 
        ######MM*#####    you. The O's are the mounting holes.
        ##############
        #O##########O#
        ##############
        ######AA######
        #O####AA####O#
        ##############

I took two of these an bolted them together using threaded rod (the ='s) and
spacers that I got at the hardware store, using four of the mounting holes
(one in each corner). Then I extended (E's) the axles and added wheels
(W's).

                =##========##=    
                 ##        ##
          MMMMMM ##        ## MMMMMM
          MMMMMMM##        ##MMMMMMM
   WWW    MMMMMM ##        ## MMMMMM    WWW
   WWW           ##        ##           WWW
   WWW           ##        ##           WWW
   WWWEEEEEEAAAAA##        ##AAAAAEEEEEEWWW 
   WWW           ##        ##           WWW
   WWW          =##========##=          WWW
   WWW                                  WWW
  
Next I went to the hardware store and got two six foot pieces of 'Channel
MF'. The large one was 33/64 x 1/2 x 1/16 and the smaller one was just
 small enough to fit into the larger one. They are some kind of 
extruded aluminum.

        LLLLLLLL    This is an end view of how the channel fits together.
        Lssssssss   the fit was tight enough that if there was a piece of
        L       s   paper between them you would have to pound them together.
        L       s       
        Lssssssss
        LLLLLLLL

This effectively makes a tube, and you can buy ready made tubes out of the 
same material, but by using the overlaping channel, you can make good clean 
strong joints. These measurments are not exact, you can use whatever your
requirements demand, but the method should be the same. I started off by 
cutting two small-sized channel to 16 inch lengths. Then I cut two more 
from the larger channel but I cut these shorter by two times the depth of
the channel. When I put these together, I ended up with two tubes, with the 
small-channel sticking out of the ends of the longer channel by about 1/2
inch. They looked something like this:


            LLLLLHLLLLLLLLLLLHLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
        ssssLLLLLHLLLLLLLLLLLHLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLssss
        ssssLLLLLHLLLLLLLLLLLHLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLssss
        ssssLLLLLHLLLLLLLLLLLHLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLssss
        sssssssssHsssssssssssHssssssssssssssssssssssssssssssssssssss



                                 
 (Back of robot)               top view                   (front of robot)



        sssssssssHsssssssssssHssssssssssssssssssssssssssssssssssssss
        ssssLLLLLHLLLLLLLLLLLHLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLssss
        ssssLLLLLHLLLLLLLLLLLHLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLssss
        ssssLLLLLHLLLLLLLLLLLHLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLssss
            LLLLLHLLLLLLLLLLLHLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL


I then drilled a couple of holes thru the centers (shown here as H's,
as if you could see thru the metal to the holes). 

Please forgive the drawing. The scale of the front is wrong as it 
is much longer, but there is not enough room when I show the 
detail I need.

Next I bolted these two tubes to the motors using the two remaining
mounting holes. In his picture I rotate the motor around from the 
end (or back) view to the top view. 

                WWWWWWWWWWWWWWW
                WWWWWWWWWWWWWWW
                WWWWWWWWWWWWWWW
                      EEE
                      EEE
                 =   MMMMM   =
       LLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
   ssssLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLssss
   ssssLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLssss
   ssssLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLssss
   ssssssssssssss=sssssMsssss=ssssssssssssssssssssssssssssssssssssss
                #=###########=#
                #=###########=#
                 =           =
                 =           =
                 =           =
                #=###########=#
                #=###########=#
   ssssssssssssss=sssssMsssss=ssssssssssssssssssssssssssssssssssssss
   ssssLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLssss
   ssssLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLssss
   ssssLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLssss
       LLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
                 =   MMMMM   =
                      EEE
                      EEE
                WWWWWWWWWWWWWWW
                WWWWWWWWWWWWWWW
                WWWWWWWWWWWWWWW

Next I added a rear bumper made out of the large channel and a small 
connector to the front, also out of the large channel. These fit nicely
over the extending small channel and you can drill a hole thru both
to secure them together (O's). The result looks something like this:

  LLLLL
  LLLLL
  LLLLL        WWWWWWWWWWWWWWW
  LLLLL        WWWWWWWWWWWWWWW
  LLLLL        WWWWWWWWWWWWWWW
  LLLLL              EEE
  LLLLL              EEE
  LLLLL         =   MMMMM   =
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
  LLOLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLOLL
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
  LLLLLsssssssss=sssssMsssss=ssssssssssssssssssssssssssssssssssssssLLLLL
  LLLLL        #=###########=                                      LLLLL
  LLLLL        #=###########=#                                     LLLLL
  LLLLL         =           =                                      LLLLL
  LLLLL         =           =                                      LLLLL
  LLLLL         =           =                                      LLLLL
  LLLLL        #=###########=#                                     LLLLL
  LLLLL        #=###########=#                                     LLLLL
  LLLLLsssssssss=sssssMsssss=ssssssssssssssssssssssssssssssssssssssLLLLL
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
  LLOLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLOLL
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
  LLLLL         =   MMMMM   =
  LLLLL              EEE
  LLLLL              EEE
  LLLLL        WWWWWWWWWWWWWWW
  LLLLL        WWWWWWWWWWWWWWW
  LLLLL        WWWWWWWWWWWWWWW
  LLLLL
  LLLLL

There is another type of extruded aluminum called 'Flat Bar'. I got a 6 foot
length and just bent it like Superman bends iron bars into a parabola shape
and wrapped that around the front to give it a finished look. 

bbbbbbbbbbbbbbbbbbbbbbbbbbbbb
  LLLLL                       bbbbbbbbbbbbb
  LLLLL                                     bbbbbbbb
  LLLLL        WWWWWWWWWWWWWWW                      bbbbbbb
  LLLLL        WWWWWWWWWWWWWWW                             bbbbb
  LLLLL        WWWWWWWWWWWWWWW                                  bbb
  LLLLL              EEE                                            bb
  LLLLL              EEE                                              b
  LLLLL         =   MMMMM   =                                           b
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL b
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL b
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL b
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL  b
  LLLLLsssssssss=sssssMsssss=ssssssssssssssssssssssssssssssssssssssLLLLL  b
  LLLLL        #=###########=                                      LLLLL  b
  LLLLL        #=###########=#                                     LLLLL  b
  LLLLL         =           =                                      LLLLL  b
  LLLLL         =           =                                      LLLLL  b
  LLLLL         =           =                                      LLLLL  b
  LLLLL        #=###########=#                                     LLLLL  b
  LLLLL        #=###########=#                                     LLLLL  b
  LLLLLsssssssss=sssssMsssss=ssssssssssssssssssssssssssssssssssssssLLLLL  b
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL  b
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL b
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL b
  LLLLLLLLLLLLLL=LLLMMMMMLLL=LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL b
  LLLLL         =   MMMMM   =                                           b
  LLLLL              EEE                                               b
  LLLLL              EEE                                            bb
  LLLLL        WWWWWWWWWWWWWWW                                  bbb
  LLLLL        WWWWWWWWWWWWWWW                             bbbbb
  LLLLL        WWWWWWWWWWWWWWW                      bbbbbbb
  LLLLL                                     bbbbbbbb
  LLLLL                       bbbbbbbbbbbbb
bbbbbbbbbbbbbbbbbbbbbbbbbbbbb


The parabola is a bit truer and the front is longer, but you get the idea.
I added a caster in the front and cut a piece of plexiglass in the shape 
of the parabola for the floor. The frame and motors are strong enough to 
carry two 12 packs of coke (about 20 pounds I think) although I need better
wheels for that weight. 10 pounds is no problem. I used 3 inch RC car wheels
and with the motors runing at 50 RPM, is is a bit slow, but it has plenty 
of power for larger wheels. About 40 feet per minute, I think. 

$25    	for the Motors
$20-30 	for other parts (the plexiglass was expensive but you could use
	hardboard)

Tools: 
 Benchtop Drill Press (you can do it with a hand drill but I cannot drill
			straight)
 Hacksaw blade in a cheepo saber saw
 Screwdrivers and such

PLEASE NOTE THAT MUCH OF THIS IS FROM MEMORY. The details are probably not
exact. If you need more exact info I would be glad to post it, but I 
feel a bit funny posting this much. I never see much hardware info posted,
except about Legos. I hope that this was not a waste of bandwidth. Probably
pretty basic stuff which is why no one ever talks about it, but it was a
learning experience for me. Maybe it will help someone else. I would like
to know how others have solved the base problem. 

Now to start on the electronics. Still waiting for my 6.270 parts.  -Chuck-

-- 
------------------------------------------------------------------------------
Chuck Rice                                                   carice@netcom.com
