I've talked about RC rock crawlers before, and I've also taken a look at small-scale indoor cars. This time around, I'll combine the two and also toss in a dash of FPV. Rock crawlers are especially good for indoor driving because you do not need a lot of space, nor do you have to worry about having a smooth, spotless floor. In fact, as driving surfaces go, the rougher, the better.
The vehicle I chose is the Temper ($80), a ready-to-run model from ECX. This model is available in either 1/24 or 1/18 scale. I chose the 1/24-scale version, which is the same scale as most plastic car models. It is about 6.75" (171mm) long and 4" (102mm) wide.
In many respects, this downsized crawler is just like my larger 1/10-scale machine (which is a lot like full-scale crawlers). It has full-time 4-wheel-drive, locked differentials, 4-link suspension, super-soft tires…all the stuff you would expect on a rock crawler. The only obvious difference is that the Temper uses friction dampers rather than oil-filled shocks.
A 2.4GHz radio system is included. The transmitter looks smaller than most others, but it is a comfortable fit in my hand. It has servo reversing and adjustable control rates. It's a neat, compact piece. The receiver and ESC are combined into one unit aboard the car. Steering is handled by a tiny analog servo.
Power comes from a 4-cell 150mAh NiMH battery. The battery is removable, so you can buy a few spares ($14) and not have to worry about down time. The included charger is a simple USB-powered device. To be honest, I haven't had much luck with it. I've tried powering the charger from a few different USB sources and it never seems to give the battery a full charge. I've reverted to using my Hitec X4-Eighty charger (huge overkill) with good success.
There is almost no prep work necessary to get the Temper going. I only had to install the included AA-sized dry cells into the transmitter. The pre-painted polycarbonate body is attached with four horizontal posts and hitch pins. With the body removed, it is a simple matter to snap the onboard battery into place, plug it in, and turn on the power.
I quickly found that driving a crawler indoors is just like driving one outdoors. The Temper is not very fast…okay, it's not fast at all. So don't expect to be doing donuts in the living room or wheelies on the kitchen table. The fun and challenge here comes from driving over seemingly impassible obstacles. An advantage of indoor crawling is that you don't have to go searching for those obstacles. You can just make them.
Boxes and books are obvious choices for creating a challenging crawler venue. Stack them, stagger them, or pile them. Just about anything will do. Plus, it's easy to make changes as you go. I also found that Legos work really well. They are obviously very versatile and the textured surface provides great traction.
I am often amazed at what this little machine can climb over. Clearing an obstacle has as much to do with driving style as the Temper's performance. Sometimes charging head-on is the best tactic. At other times, a more subtle and nuanced approach yields better results.
The Temper is one of those RC toys that you don't mind sharing with anyone. It is sufficiently slow and tough that there is very little risk. While a rookie might not get the most performance from this crawler, they are not likely to break anything either.
Driving flat-out on level ground, I can get more than 10 minutes of constant running with the stock battery. That example, however, does not really reflect how most people would actually drive a crawler. I suspect that most of us will get much more time as we stop, go, climb and maneuver.
I thought it would be fun to try negotiating my indoor crawling obstacles via FPV. The new breed of micro FPV cameras and integrated video transmitters (VTX) make it possible to add FPV to just about any RC vehicle…even a tiny one like this. The system I chose is the Spektrum VA2510 ($100). Not only is it a combo camera and 5.8GHz 25mW VTX, but the whole thing is wrapped in a tough outer shell. FYI – as with most FPV systems, you need an FCC Amateur Radio license to operate this system.
Pretty much any 5.8GHz receiver capable of capturing Fat Shark or Race Band frequencies can be used with the VA2510. I recently picked up a set of Spektrum Focal V2 goggles ($400) so, that's what I used with the Temper. Sure, the Focals are overkill for this application. But they come equipped with a large mask area (like my other goggles that I've modified) that makes them very comfortable to use. So, why not?
I made a mount for the camera unit by folding a small piece of scrap plastic sheet (taken from the Temper's packaging) into a wedge shape. I used double-sided tape to attach the mount to the top of the ESC/RX and the camera unit to the mount. This arrangement allows me to see whatever is just ahead of the front wheels. It's a pretty good perspective.
The VA2510 requires a 3.9-6.0-volt power source. I initially tried tapping into the power output from the receiver by putting a splitter on the servo leads. This caused the video signal to drop out every time I turned the steering wheel or advanced the throttle…no good.
After my initial failure, I spliced into the battery leads of the ESC/RX and installed a 5-volt step-up regulator that feeds the camera directly. Even when the battery fades, the camera will still get a constant 5 volts. This set-up has been working very well.
I have several 1-cell 350mAhLiPo batteries with the same connector used on the Temper. The voltage is a little lower than the NiMH battery, but the LiPo cells work well. They do not quite fit in the stock battery location, so I keep them in place with small strips of Velcro. It is worth noting that the connectors on my LiPo batteries were wired with the opposite polarity of the Temper. It was a simple matter to swap the pins to get everything homogeneous, but it could have fried the ESC/RX if I had not noticed beforehand.
I was initially hesitant to use LiPo batteries because the Temper does not have a cut-off feature to prevent excessive discharge. However, I have had good success by simply removing the battery as soon as I notice a drop in motor speed or sluggishness in steering.
Using FPV certainly adds a unique twist to driving the Temper. Going over obstacles is much more challenging with the limited situational awareness that the goggles afford. Plus everything looks different from the car's perspective. It's a lot of fun. If you thought FPV was just for flying machines, think again.
I wasn't sure what to expect from such a small rock climber, but I've been very impressed with the performance of the Temper. In spite of its small size, it has hobby-quality parts and all of the necessary ingredients for crawling. It lets you turn any room of your house into a challenging obstacle course. The option of adding FPV only sweetens the deal.
Terry is a freelance writer living in Lubbock, Texas. Visit his website at TerryDunn.org and follow him on Twitter and Facebook. You can also hear Terry talk about RC hobbies as one of the hosts of the RC Roundtable podcast.