Nuclear Kitten 5.1: Start to Finish

Friday, August 27th, 2010 @ 10:05 | Bots, Nuclear Kitten 5, Project Build Reports

Something that very few people (myself included) have seen is the inside of NK’s weapon motor. About the time I built it in 2008, my camera decided to consume itself. So all I had from that time were grainy cell phone pictures because I’m compulsed to post build reports, but those pictures didn’t really show anything worthwhile.

NK’s motor was the third hub motor that I’ve ever built, period (after the original RazEr motor and the second iteration). It is also hands-down the most cleanest wound and carefully terminated motor I’ve built. This was back when I actually had patience for making motors. All the winding layers are clean and the termination is perfectly symmetric like a LRK should be.

After this, it all went to hell because I just stopped caring about how neat my motors looked… or even how concentric and wobble-free the cases were because it was fine as long as it could MOVE, dammit.

In International Crazy R/C Airplane Guy Notation, this motor is a 5205-14D. 52mm diamter stator, 5mm stack, and wound 14 turns per tooth in Delta termination.

I bought replacement magnets from Superdupermagnetgeorge to fill back in the 25% or so of the rotor that had become detached. The original magnets appeared to have been retained solely by superglue.

That’s kind of not legit at all.

In recent days, MITERS was given several large jugs of epoxy and hardener. While cleaning out a back shelf for the new EPOXY section, I found alot more adhesive accessories from years ago. Of most immediate interest was several cans of epoxy filler in different flavors in types. There was a can of West System 403 fiberglass-based filler, a bucket of phenolic microspheres, and wood flour.

I decided to do something that every other custom motor builder seems to do – fill in all the gaps and seams in the magnet ring with some hybrid epoxy. Adding filler gives the glue volume and more bonding area to the magnets. The fiberglass-based filler came out rough and lumpy, so I tried mixing up a cup of phenolic microballoon epoxy. It came out looking sort of like epoxy-flavored Nutella.

Now those magnets shouldn’t be going ANYWHERE.

weapon pod pivot

One of the gimpiest parts of NK5 is the weapon pod’s rear pivot. The disc is mounted on an assembly that can swing up and down, letting the bot drive inverted if necessary. The issue is that I made the last pivot in like 5 minutes. It was just a piece of sandpaper-cleaned Home Depot aluminum tubing and some roughly cut spacers. It flexed all over the place, and by the time D*C2008 was over, the tubing had crumpled from the impacts.

This was inexcusable. And so, in the middle of the night, I hopped on the lathe and just started making something. Above is the first 100% designed on the fly part I’ve made in a very long time. On one end, a snap ring groove. And on the other side, a 1/2″-28 thread machined so a thin panel nut can thread onto it. It basically functions as a very complicated but specialized bolt, holding the two halves of the bot together with some preload.

Originally I had intended to pick a random snap ring from the hardware bin, but a bit of digging around located me these weird e-clip-like things. A bit of research on McMaster showed me that they’re called “poodle rings”, presumably because of the big ears.

They had a much large diameter and thus potential contact area, so I remachined the groove slightly to fit them.

I also recut the UHMW spacers (using the same stick of UHMW) so they fit better and were also much large in diameter. The larger in diameter they are, the better they can resist side forces.

The old disc was warped from NK faceplanting into the steel arena bumper at full throttle. As a result, I dug out the spare disc I cut in 2008 and gave it the heat-to-orange-and-dump-in-oil treatment. It’s a crude method of heat treating, but it gives decent hardness for 4130 in bulk (don’t try this with a tube frame…) Afterwards, I reassembled the weapon motor and gave the teeth a touch up on the grinder.

With the important part of the robot done again, I begin refilling the internals. Pictured is the 1.3Ah Li battery I bought as a replacement for the old 2008 battery, now featuring a very dead cell. I actually got two because they’re too cheap for their own good.

And here’s the beauty shot:

While I had the lid open, I added a green LED next to the blue. Because funky colors are totally a priority.

NK handles just as well as I remember it from 2008. The right side drive motor is making some weird noises, but it doesn’t skip or feel crunchy. Regardless, I should probably get some replacement motors and have them dropped in Atlanta for next week.

Total robots finished: 2.999999999996842178 / 3

 

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    2 Responses to “Nuclear Kitten 5.1: Start to Finish”

    1. Mike L Says:

      DELTA, waaaaaaaat, doesn’t like, 1/3 the power get wasted!!!inefficient much

    2. Mike L Says:

      sorry that this is so late, but, what did u use to holdthe duct in place in the last(and most destructive)version of fancart, it looks like sparkly straps