Monday, June 29, 2009

Photo quality is back

... After just one more pic, I swear! I mean, this pic wouldn't be possible with anything other than my cell cam. It'll be obvious, don't worry.

Before, this blog has had a maximum of 2 confirmed (by comments) readers at any given time, with previous picture quality. There hasn't been a comment since the poor picture quality began. Anyone remember this failed attempt at fixing my good ol' Konica Minolta X50? Tried to charge using the external DC jack, but then realized it doesn't charge from that jack, then tried to power from that jack ~5 volts from USB. Then I found out the USB supply current was too low for the camera to actually operate on.

Now, I had this idea a few months ago, but then forgot about it until now. It's so simple.

Yep. Just 4 AA's, NiMH, rated at a total of 4.8 volts, while the dc jack on the camera is asking for 4.7 volts. Close enough, even alkalines worked, which provided nearly 6 volts. I measured current draw, and it was only a little over the USB 100 mA at 340 mA. Okay, it's more than three times as much, but its still very low.
I'll probably re-do it with a longer cable, as this will get cumbersome when I try to use a tripod, but it worked. Also, yes that is the 4-AA holder that I also used as a receiver pack on the last post.

10 Cells

On Saturday, after the old Ni-Cads had been cycled a few times with my discharger, I headed out to a nice little spot (in fact the only spot with flat dirt here in Berkeley) west of here to finally see what 10 cells could do-at least with my 20 turn Stinger/Flash hybrid.

It just so happened there were a bunch of guys running nitro RCs! As I was setting up for some fun and getting ready to challenge their Losi XXX-NT (I think) to a drag race, since I was feeling confident with the 10-cell setup, I pulled the trigger (throttle) ever so slightly, it moved a little and--death. It died right there. The ESC had died. It had run on 10 cells before.

I inspected it later that night, nothing seemed wrong, and it was rated for up to 10 cells. I went back on Sunday with the very old and weak (but dependable) Elektra, rated at 6 cells and only handling down to 20-turn motors.

It was still fun, but I felt it could have been a lot more fun. I still went and got it a bit dirty though :D Enjoy

That little red thing in the back is a ghetto (but effective) air intake to cool the motor.

Where the intake leads to

And another shot

My favorite shot

The Elektra, the purple heatsinks match the rear purple shocks lol.

The failed ESC - Duratrax Streak.
I don't know if you can blame it, I was pretty bad at soldering when I replaced the 14 gauge with 12 gauge. But it was working fine this entire time. Also, why on EARTH would you release an ESC rated up to 10 cells and down to 12 turns with 14 gauge wire, a tamiya plug and bullet connectors? Where are the solder posts? It was very cheap though, so I'm not too sad.

I kind of messed up that motor mount that I described a few posts ago, so it'll be a while before I get the time and money to work on it again, but I figured by then I might as well go brushless :D

Also, for when I get back into this, I picked up a disposable camera that can be used as a battery zapper, for the next time I decide to bring out the old NiCads. I think I'll document it and everything, recording down charge cycle statistics before and after the treatment, and I'll try on the entire pack, and per cell as well. Hopefully there will be graphs.

Funny story about how I got this also. So, all i really went to Walgreens for was a bag of chips, I had a 6" sub for lunch and was feeling a bit hungry again, and then I passed by the disposable cameras and remembered the whole zapping thing, although I had intended to focus more on school and not RC again for a while. Anyway, I ask the clerk if I can have one of their old disposables, she asks the manager, and I'm denied. Then, as a stroke of luck, some girl happened to be there, ready to develop, and offered me hers. This was all in front of the clerks and manager too. Okay, I'm sorry, that wasn't funny at all.

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...

Friday, June 19, 2009


While browsing Goodwill last week, I came upon a ridiculously cheap "New Bright" Hummer H3 rc truck, the kind you find in Wal-Mart. There was no controller, so it was marked at $2, $6 if it had the controller. It had a 9.6V battery inside, and seemed to be in order. I figured maybe I could have some fun with it, use the body for future vehicles, since I've been looking into a crawler, what with their immense rise in popularity in recent years, and my thirst for the scale looks (of some) and the solid axles. My Rustler and 18R both have independent suspension, which is good, but I wanted something new.

Upon closer inspection, there were some cool things I noticed. My experiences with cheap RC cars as a kid led me to think that they used irreversible assembly techniques, so I couldn't tamper with anything as I usually loved doing. This little truck was held together with mostly philips screws, and some parts that snapped together. The entire battery/electronics compartment had a nifty locking mechanism and came clear out (after unplugging the steering motor and drive motor) with two screws.

However, the overall impression was still typical. There was no front suspension, at all. The front steering knuckles were mounted on stationary arms. Interestingly enough, they had shocks! same as the rear, except they just didn't do anything but look pretty.

The rear end had about a micron of suspension travel (laugh here). See if you can tell which picture is compressed and which is relaxed!

There was about an Angstrom of available articulation.

I thought about some chassis/suspension modification. Installing my own electronics would be very easy. However, any modifications would be difficult and I would have to custom-fabricate parts with materials that would have been costly.

It occurred to me then, what I could do. I had all I needed for a hybrid RC K'nex/New Bright monster truck!!!!! I had been wanting to do this for a year (here's the post to prove it! That was a working rolling chassis), but with all genuine K'nex parts (wheels, gears, etc etc). However, as I had been tossing around the thought for a year, every part of it just seemed very hard to do properly, and wouldn't perform well or be strong at all. The gearbox would have very many gears for a good reduction ratio, or I would have to use the weak supplied K'nex 130-motor-driven gearbox. The suspension system would be very weak and prone to breakage, as well as the steering system. The large K'nex tires are very narrow, and would have to be stacked, but I didn't even have any. The only working universal joint design I could find was HUGE and couldn't be trusted without tape.

On the other hand, the New Bright rear axle was a complete solid-axle drive unit, with its own motor inside. I could easily detach it and use it separately without any complicated mechanical connection.

I quickly set to work on a prototype.

The front axle is missing because at this point all I had was a chassis and a rear axle, which was a given.

Even though the axle link system I used involved only two links, which were hard-fastened to the axle, the knex rods were flexible enough to allow some articulation. The rods conveniently stuck into holes right under the shocks (which were very stiff, there would have been still more articulation had the springs been softer. However, the goal of this project was to be as cheap as possible).
There was more overall suspension travel:

When it came to the front end, I tried making an "axle" out of knex. It turns out that the difference in size of the knuckle pins and knex rods were too great, there was a lot of slop and the toe-in varied by as much as ~40°. So, I ended up cutting the "axle" from the chassis itself.

A knex rod zip-tied to it aided mounting. This project has taught me the value of zip-ties.
At this point, I had a rolling chassis+transmission.

Silly truck, that isn't your body!
That round part in the front turned out to be the only thing preventing optimum servo mounting, so away it went. I used the stock steering link to link the two knuckles together, but can you guess what I used to link the servo to the knuckles?

Custom blue plastic tubing?

That's right, it's a ball-point pen. Fit the bill perfectly, and was free since I had one laying around. (I just remembered, the cap from this pen went towards a headphone recable I did in 2007).
I installed all the electronics, and it was, well, slow.
Here are some more shots.

I've since made it waterproof (all I had to do was bag the receiver and esc), installed the motor from my car (which was way too fast, kept spinning inside the pinion gear), and rewound the original motor. It was loads of fun with the 18R motor, but I wanted to drive my 18R again (also the 18R motor melted the plastic gearbox housing a little bit and it upset the gear mesh :/)

I've been drifting the 18R, all I had to do was tape the tires. It's loads of fun and makes me want to keep it again. I'll post a crappy vid soon.

As for the rewound motor, it went from 30 gauge (or maybe even thinner) and NINETY-FIVE turns to this cool green-enamel-coated 26 gauge I got from radioshack and twenty-nine turns. I think it's safe to say I have a nice hand-wound modified motor lol. Maybe not nice since it's now my number-one source of problems, but it's a good in-between the performance of its stock form and the 18R motor.

As for "crawling" ability, it sucks. It's not 4wd and the gear on the axle is so big! It gets in the way very often. Also the tires aren't the best for the task (hard compound with chevron+spikes). I wonder if I cut off the spikes will it be better? Boil the tires? hmmmm

Still it's fun to try.

All that water isn't good for the axle, but some WD-40 fixed the problem and prevented new ones

Shot of the motor armature before and after winding. Sorry for crappy image quality, still using the phone.
That green wire looks so cool, the picture doesn't do it justice.

FINALLY, that's it for now. Actually there's more to post but I feel I need to start a new one. Tomorrow.