Today we’re going to look at the electronics we chose for Project Scorpion. Like we stated in Part 1 the main purpose of this build was to evaluate what a very low budget Axial AX10 Scorpion could do. With that in mind I can guarantee that you won’t be seeing any high dollar brushless motors or Spektrum radio systems here. Instead we chose to go with a simple 2 channel AM radio system, and Integy lathe motor, and an LRP electronic speed control. After the jump you can read all the info on each one.
Part 2: Electronics
It’s funny how such a simple thing can make a big difference. Years ago when people needed a motor with torque for their r/c truck they had two choices, either a 27t stock motor, or a big buck pulling motor. The 27t motors were cheap but they just didn’t have enough torque for rock crawling. The pulling motors (ie. Astroflight Pullmaster) had a ton of power but were expensive and required an expensive ESC. Finally one day somebody had the bright idea to throw motor intended for a motor lathe in their truck and the rest is history. The lathe motor has truly changed the face of the r/c rock crawling world. Considering how cheap these things are we knew it was the perfect choice for Project Scorpion. Currently these motors are available from 35t all of the way up to 85t. We originally chose to go with the tried and true 55t but because they were on backorder we decided on the Integy 45t Pro Lathe Motor. ($19) This motor has really good torque and with the gearing in the Axial it’s pretty much unstoppable. I can’t even imagine what the 85t would be like.
For the ESC we were again looking for something to meet a very low budget. During our search we found a few models that seemed to fit our purposes but then a search on a rock crawling forum pointed me to this one. What caught my eye with the LRP Runner Series ESCs is that they are totally waterproof! In the past I was forced to wrap my ESC in a ballon to keep moisture out but in doing so I took the chance that it may overheat due to a lack of airflow. With this ESC that is no longer a problem. Hopefully other ESC manufacturers will follow in LRP’s footsteps, we need more waterproof ESCs. The exact model we chose was the LRP Quantum Runner Reverse. ($40) It is only rated for 18+ turn motors but considering that this thing will only be used in a rock crawler I don’t see that ever being a problem. There are two drawbacks to this ESC however. First off the reverse delay. For fooling around on the rocks in my backyard it doesn’t bother me all that much, but to some it may be annoying at the least. Secondly the automatic setup. This ESC has a completely automatic setup. Just plug the battery in and go. The problem is that the ESC has the knack of sometimes reversing the throttle. This little annoyance is a known flaw with this ESC and really isn’t a big deal. If it does reverse your throttle all that is required to fix the problem is to disconnect the battery for a second.
Here is a size comparison of the Quantum Runner Reverse. I had no idea this thing was so small.
A close up picture of the ESC
Here is what comes with the Quantum Runner Reverse. A bunch of decals, capacitors, and of course an owners manual. (not pictured) It is highly recommended you install the capacitors to your motor to reduce glitching.
Here is the ESC after we installed a set of Deans connectors.
The Quantum Runner Reverse includes a heatsink to fit over the FETs. However it is imperative that when you install the heatsink you use the tiny rubber grommet which is included. (arrow) Not only does this grommet keep the heatsink secured to the ESC but it also stops the heatsink from touching the FETs. If the heatsink or any other metal object were to touch any two FETs at one time it would result in the shorting out of the ESC.
For the radio we chose a simple Futaba PH2 AM radio system. ($42) I’ve been using these things on R/C cars and trucks for years without a hiccup. It includes one servo.
Here is a size comparison showing how tiny the Futaba receiver is. I remember when these things were humongous!
Stay tuned for part three which includes the build of Project Scorpion!