Friday, September 6, 2013

A box from the Barbie Jeep Graveyard

As sporadic visitors to this site well know, I have been running an an after school class at the local middle school for 14 years.  I have the little imps build small combat robots with the general excuse being that they actually learn a fair amount in the process.

But it is a challenge to keep the class interesting.  I mean interesting to me, the capacity of pre-adolescent (mostly) boys to be engaged by mechanized carnage appears to have few limits.

So this year I decided to make a small change.  Instead of 1 and 3 pound weight classes we would just go to the 3 pounders.  This should make for more streamlined tournament brackets and allow for a little more reckless kinetic abandon.

It has been difficult to find motor/gearbox components suitable for making robust yet lightweight weapon systems.  So with the anticipated increased need I did some shopping around and found a guy who in effect runs a Barbie Jeep graveyard.  He was able to toss together a box of odds and ends for me.

These have been unpacked.  They of course arrived nicely padded and wrapped.

When proposing to use a motor/gearbox combo to power a weapon you need to watch the weight.  A three pound robot still needs batteries, radio gear, wheels.  Oh, maybe a bit of armor would be useful. So it would be helpful if the weapon driver could be no more than say, 1.5 pounds.  It is also nice when the gearbox is sturdy enough to comprise most of the framework of the machine.

Many of these units were in ones and twos, but a single type came in a batch of five (with lots more available).  Lets just toss one on the old scale...

One pound 14.4 ounces.  This is not going to work out.  The problem is that these gearboxes are from an older version of kiddie car, and were ridiculously over engineered.  Everything you see above that is black is actually steel!  To determine their utility for Machines Behaving Badly I had to do a bit of robotic surgery.  And not the kind they do on us...

Top view.  The grey part on the motor is some sort of heat sink.  No doubt it prolongs motor life over the long term.  But in robotic combat there is no long term!  Off it comes, along with the black metal bracket supporting the motor.  I had hopes of removing the black top plate, but it supports two of the pins holding gears in place, so it stays.  I do think you could gain another ounce or so by taking a dremel tool to it and cutting off the lateral portions.

Bottom view.  The metal plate can be pried off.  The grey collar marked with an X is optional equipment.  The white hub with a ? mark on it could also be discarded, or.....

Final slim-n-trim version.  I kept the hub, and once the collar is removed and a bit of plastic rim is dremelled off you can just drive a few screws into the marked areas to fix a hub in place.  I am pretty sure that even middle school level engineers can figure out some nasty bars, blades and flails that could be attached with ease to the above.  Final post operative weight...

One pound six ounces.  And in a pinch you could lose another ounce or two by chopping up the remaining metal plate on the top, by trimming off part of the white plastic hub, or by adopting the traditional desperation measure of getting a drill and "Swiss Cheesing" the gear box and the gears inside it!

Class starts in a couple of weeks.  Episodic updates by and by.

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