1987 Boy's Life Robot rebuild.

Was helping clean out my parent's attic today when I stumbled upon this:

These are the unfinished parts from a "robot" project found in the February 1987 issue of Boy's Life:

Hmmmm..... let's see what I can do with this....


I'm amazed! I always wondered if anybody else tried to build it.

I got that Boy's Life issue as a young boy, but I wasn't able to build it because I didn't have the gear motor used...

...unless I wanted to cannibalize my working Milton Bradley Big Trak!

That particular "robot" used the gearbox out of that toy; the gearbox was available from a few different surplus dealers back then, IIRC. It's long since been impossible to find one - not that it matters (unless you need a new one for your Big Trak!).

I still have my Big Trak (plus Transport) - still with the boxes, and both still work. I'm glad I didn't tear it apart (like I did with a lot of other toys) for such a project.

PS: A few notes about that gearbox:

The green circuitboard was for a custom "slot-sensor" (made with an IR LED and phototransistor) - through which one of the gears in the gearbox passed; the gear had a series of holes. This so the Big Trak could measure how far it moved and how far it had turned.

Now - you can see that it actually had two wheels driven in a "differential steering" arrangement, right? But only a single sensor for both...how?

Well - inside the gearbox the two axles were links with a "magnetic clutch" - this served two purposes:

  1. First - to link both drivetrains to the single slot-encoder output gear, and...

  2. To keep both wheels moving at approximately the same rate when moving forward or in reverse.

This was actually a fairly ingenious mechanism for the toy; it was also a near requirement due to the interesting way the engineers decided to control the direction of the motors. Instead of using an h-bridge per each motor (which was expensive back then), they instead used one half-bridge per motor, and a dual-ended power supply - compose of 4 D-Cells in a series arrangement (6 volts DC) with a center-ground tap, yield a +/- 3 volt DC supply. The half-bridges were made with simple low-cost transistors, but due to the funky supply, the batteries could run down unevenly (depending on if you made more right turns or more left turns) - so the magnetic clutch helped to prevent this.

The "microcontroller" used in the toy was a simple programmed "stepped" controller, where each "step" could be input and last for so many "ticks" (with feedback from the slot encoder) - it only had room for a very limited number of "instructions", which were structured in a similar manner to the LOGO programming language. This controller was powered by a separate 9 volt (PP3) battery.

Hi All,
I remember buying one of those motor/gearbox units, as said it was from the BIT TRACK toy, which you could program by pressing keys on a keypad. One one good point was that the motors are magneticly linked together, so when the motors are going in the same direction, then both ran at the same speed, something that I find does'nt seem to work now, it must have been one of the first bots I maded!!

Good old days!!.



Hey all, I built one of these for my daughter just last year. It was fun to reimagine what it could look like as an adult as opposed to my 10 year old self.

I also created an archive of various Boy Scout Robots submitted to Boy's Life Magazine:

Next up is a remote controlled version.

Wow !! Thanks for the link.
I've been a scout master several years and have used parallax BoeBots for our
robotics merit badge.

I never knew BSA had robots back in the 80s.
Will have to find one of those old magazines to show the scouts.