Friday, June 26, 2009


Well, the Knex truck has been put on hold for now. I got tired of not being able to go very... off-road.

The motor I rewound was FAST. When it worked. My crappy solder-joints kept coming off and ruining everything. So I bought a stock Losi Mini-T motor ($15, GASP!) and all is good.

I've been meaning to get the Rustler back in operational condition, and so I said, what the heck, I'll go straight for the 10-cell setup I've been wanting to try for so long. 6-cell is standard.

There are a total of 14 cells in this pic! Because 12 volts is too much for the receiver to receive power from the ESC, I needed a separate battery-pack to power it. Luckily I had a 4-AA holder left over from my electrical engineering course.
For the main battery pack, basically I just wired a cheap 6-cell 1500 stick pack with a 4-cell 1500 stick pack. The 4-cell is a chopped-up 6-cell, and that was the only soldering I had to do for the entire thing :D

I use Duratrax/Andersen Powerpole connectors, which have a low resistance compared to the typical "tamiya" connector, but they're very unpopular nowadays compared to deans and traxxas connectors. However, you can't do this with deans or traxxas:

I just turned two battery packs into one! And its reversible! This is made possible because the Powerpole plug is modular, and more importantly, has no gender (or is it hermaphroditic? who cares). I don't know about the current carrying characteristics (o.o alliteration) when comparing the three types of plugs, because the Traxxas one is relatively new and I've seen the contact plates, they're pretty big, but for my brushed-motor, NiCd application the 'poles are super. I'm glad I switched so many years ago.

How did it run? Extremely poorly D: My comm has breathed its last breath, as I had overworn it, and the NiCd's haven't been run in years, so it's understandable they were slower than my 6-cell-matched NiMH packs.
The badly worn comm. It's hard to see but much of the copper is missing.

For the battery packs, I read around about zapping them with a high voltage to revive them and loosen the internal crystals killing their performance, but a tip from a guy at my local electronics shop made me reconsider. He told me to beat the packs. It made sense! However, now, after a few charge/discharge cycles it doesn't seem to help that much. I haven't tried it in the truck yet, and because of the comm's condition, it looks like it will be quite a while before I get to see 10-cells and 13-turns come alive.

Speaking of batteries, I finally made a discharger so I could perform battery maintenance better. The local electronics shop had the standard automotive 1157 bulbs for $1 for two. I bought out their 6, and made a 6-bulb, 12-amp discharger. The closest automotive parts store wanted $2 each, so I didn't opt for the full, standard 10-bulb discharger. So the total cost was pretty much the $3.50 for the 6 bulbs, since I had some old 12-gauge laying around, and I have a bunch of the powerpole plugs.
The finished discharger.
The discharger in action (it got a LOT brighter with my 6-cell sidexside NiMHs, saying a lot about the performance of shotgun-style construction, which is shown in the picture).

The bulbs get blindingly-bright (with the NiMHs) and really hot. Each one draws 2 amps at 7 volts! This seems terribly inefficient, I've seen LEDs on lots of the newer cars (for everything but headlights) but why don't they put them on all cars now? I wonder if the prius and other hybrids use more efficient lamps.

Hmmm... What else was there? Oh yeah. I spotted a 9.6 volt battery charger and battery on clearance at Radioshack the other day for $4. Those batteries for crappy RC cars are pretty much 8 AA batteries, like my transmitter, and I already had 8 NiMH AAs for my transmitter, and a plug that would work with my 18R transmitter (it doesn't matter I can still take out the AAs and use them with my traxxas TQ), so now I have an easy solution for charging my transmitter batteries (previously I would have to charge 4 at a time).

As for the Rustler, I've had the 20-turn armature from my Stinger motor for quite a while now just sitting in my toolbox, with its comm in relatively good condition. I went out to my local park with my NiMH packs, and while it was impressive for what it was (A "frankenstinger", a stinger armature from the old traxxas electric vehicle standard in my Reedy Flash BB can with stiff brush springs and quad magnets) the enjoyment I had from the raw power of the 13-turn was gone. It sounded underpowered. It did go pretty fast though, and I managed to completely screw over my ESC D:

The Stinger. Apparently they gave it a makeover in recent years

Since traxxas electrics were (and are) extremely popular RC vehicles, I wonder if this could be like the standard "small block" that everyone has and is familiar with. Nah, that's probably where competition stock motors would lie.

So I think I'm going to put away the RC for a while. I really miss my old small town, living in the city, I couldn't RC just anywhere. I've gone far and wide just searching for places to have this kind of fun. Looks like I'll have to start getting into microcontrollers finally...

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