Friday, January 25, 2013

The Robot Dragster Project - Chapter Six

These "build report" posts are not the most widely read items on my blog.  No, those all seem to involve small cute dogs or jumping carp.

But I feel a need to chronicle things of this nature because I do know that they are occasionally sought out by people contemplating student robotics projects.

My last posting may have sounded a little down beat.  A crucial component got botched and one wheel hub was fritzed up beyond repair.  On a more aggravating level, it was an avoidable error.  When you are working with no shop access, just hand tools; and when you have a less than optimal grownups to monkeys ratio, things will go wrong.  Parts that get messed up are really have to devote all extra attention to basic safety issues.

So I did something I prefer not to do.  I took the project home and fixed a couple of things for the kids.

Hey, I have a drill press, a band saw, a lathe....I can in short order make sloppy, soon to fail parts of the project into less sloppy, runs a bit longer stuff.  In order of work:

1. fixed the wheel hub.  It was a press mount that had to be fairly precise.  Fortunately I had just the right thing in aluminium, easier to finesse than the original steel part.

2. At this point curiosity took over.  I hooked the motor up to 24 volt power and stood back.

Nothing happened.

It seems the RPMs were too high and the torque too low with the existing pulley sizes. The belts just spun, the wheels stood still.  Well, nothing for it but to swap in a larger pulley.  This required cutting a slot in the deck, but has the additional advantage of raising the back of the machine so that the steering gear won't prop the front of the project up too high.

I think this was a good move.  It looks better, that's good.  It moves when powered up at 24 volts.  That's very good.  And the kids can spend more time learning new stuff rather than repetitive grinding and pounding recalcitrant metal.  Also very good.
And things moved right along.  I just assigned tasks.  "You, finish and test the wiring on this speed controller, here's the schematics.  You and you, finish the mounting block for the steering.  You guys are working with me."

Motor mounted, battery box in place.  Note the bigger pulley on the axle.  And both wheels on securely.

The steering mechanism is on the bottom of the machine.  I am a little worried about damage.  We ran out of time just before securing the actuator into place.

Decorative touches.  Note the Axman surplus sticker on the left.  And here the kids are mounting a hood ornament.  It is called "Jerry" after some kind of video game character.

Hey, I don't have much of a budget.  My help is game but intermittent.  My work force is under age and over stimulated.  But by gosh I do have an official pit area.  Storage of the things you really can't do without.

I think the dragster project is back on track, and looks as if it will work.  But I guess the second unit is not likely to happen.  We keep running into little glitches that need fixing on the main unit.  That week we lost to a snow day really hurt.

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