Data Recorder

Circuit Board

Board w/Sensors

Software Details

Torque Test Graph

RPM Sensor Mounting

RPM Sensor Mounting

 

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Eagle Tree Systems

For years the only active tuning tool available for RC car racers were motor dynos and battery matchers. For the most part they have served us well when we try to find the best equipment available and make the right tuning choices. The main drawback has always been that they did their testing in a static environment and we know from experience that on-track performance can be different then what the "numbers" show.

Eagle Tree Systems has come up with a way to get real on-track performance figures to backup what is found using dynos and matchers. Their Car Data Recorder mounts in your car or truck and records different parameters of your car while it is racing that you can then download to a computer via the supplied USB cable allowing you to examine exactly what happened under race conditions.

The best part is, this is not some new fangled equipment but a modification to unit that they developed for RC aircraft over a year ago! Not only did they modify the electronics for car/truck use, they made it smaller and lighter too. The RC Car Recorder is about the size of a common servo and weights in at 1.5 oz.

Packed in this small package is the ability to record and store the positions of your steering and ESC (or throttle servo), RPM, receiver voltage, voltage of your main battery pack, amp draw and 2 different temperatures. In the works are accessories to monitor and record X and Y G-Force plus exhaust gas temperature. Ever have glitching problems? The unit even records electrical glitches!

Each item you want to monitor requires a sensor to be mounted and wired to the base unit. In the case of the servos and ESC, you use a simple Y cable. The base unit includes two servo Y cords and an RPM sensor with the other sensors being options. Let's run through the different sensors so you can see what is required to wire them into the system.

Servos/ESC: Included with the base unit. All you need to do here is plug your servo(s) or ESC into the Y cord, plug one end of the Y cord into your receiver and the other end into the Recorder. Pretty simple.

RPM: Included with the base unit. You will need to glue two magnets and mount a sensor very close to the magnets. I have found that mounting the magnets on the spur gear is, in most cases, the easiest way to go. But each car/truck can be different so you will have to use a little ingenuity when it comes to this. No matter if you mount them to the pinion gear, the spur gear or the outdrives/axles, the included software will allow you to compensate for this. You do this by telling the software where you mount the sensor, enter in your pinion and spur gear sizes, your gearbox ratio (if so equipped) and your tire size. The software will then show the corrected motor RPM and vehicle speed.

Temperature: The temperature loop can measure up to 425 deg and can be used to monitor motor/engine and battery temperature. The sensor uses a real thermocouple so the wire is stiff and it can take some care to get it in the right position and tightly wrapped on the item you want to measure. The thermocouple needs to be tight against the item you want to measure to get accurate readings. If the thermocouple wire is too short to reach the Data Recorder, you can use a common servo extender.

Battery Pack Voltage and Amp Draw: Amps are measured using a hall-effects sensor. This means you do not have to cut any wires or put a shunt into any of your battery or motor wires. You just slip the sensor over your wire and you are set to go. Voltage is measured through a single wire that you can connect to the positive side of your main battery pack.

Receiver Voltage: No sensor is needed. The Recorder measures the receiver voltage through the servo connections.

G-Force & EGT: Unknown. I have not seen either of these units so I can not report how they mount or work.

One thing to remember when hooking all of these sensors up, there is a limited amount of memory in the Recorder. The more items you record, they less amount of time that will be able to be stored. The unit can be programmed to either stop recording when the memory is full or to overwrite the old data when it becomes full. I have found that you can easily get a full 5 minute run stored without filling up the memory.

The other item that effects how much time you can store is how fast the unit samples and stores data. You can program it from 1 to 10 cycles per second. I have found that when recording at 10 cycles, RPM, pack and receiver voltage, amps, one temperature, one servo position and glitches that I can store 5+ minutes of data. This can very wildly depending not only on the amount and frequency of data recorded, but the type of racing you do and the track you race on. The unit uses a memory saving system where only required data is stored, so if you are just sitting on the line not moving, very little memory is being used.

Once you are done running you just hook the unit up to your computer via the supplied USB cable. Fire up the included software and hit the download button. Once the data is downloaded into your computer, you can then save the data. The data is saved in a space delimited format which allows you to load it into a spreadsheet program such as Excel for closer examination.

The included software, at this time, allows you to "play back" the stored data just like it was in real time. The graphical and digital indicators change with the data as it is played back. You can pause the playback, play it in slow-mo, fast forward and step one data point at a time. Before you start playback, the indicators will display things such as the highest RPM of the run, highest amp draw, lowest pack voltage, etc. You can also load saved data sets for playback which would allow you to share or email data to other Data Recorder owners so they can see your run.

Features that are being worked on for future software releases is a graphing feature that will graph the data for easy examination eliminating the need for Excel for graphing. There are also plans for a free "player" so that anyone can download, playback and display data even if they don't own the Data Recorder. All software updates will be available as a free download from the Eagle Tree Systems web site.

Software installation: Computer requirements are basically Win98SE or higher and a computer with a USB port. I have run the software on a laptop with a 233Mhz PII with Windows ME all the way up to a 2.4Ghz desktop running W2K and XP. The software ran without a problem on all of them. Before you can install the software you will need to install the Data Recorder in your car and hook up at least the two servos. When the software first installs it checks for proper communications between the computer and the Data Recorder and runs the New Car Wizard so you have at least one car profile setup when it first runs. Overall, the installation was uneventful. Just follow the instructions and you'll be set to go.

Conclusions: All this talk about what it can do is all good and well. The big question is... does it work?

I was able to test the unit with 4 different cars. An electric off-road truck, a nitro off-road truck, an electric touring car and a 4 cell pan car. Other then constructing  unique mounts for the RPM sensor on each car, the rest of the Data Recorder installation was pretty straight forward. In a couple cases the temperature sensor wasn't long enough to reach from the motor to the Data Recorder. I just used a standard 6" servo extension cord that allowed it to reach.

It will take a few uses to figure out exactly what items you really want to record. Remember, the fewer things you record the longer you can record. My normal setup is 10 samples per second recording RPM, pack voltage, receiver voltage, amps, motor temperature (temp #1), throttle servo/ESC and steering servo. This should give a full 5 minutes of recording and give you a well rounded data set to look at. If you are having glitching problems you can turn on glitch recording but I normally leave it off.

The playback system has a real "cool" factor as you see all the dials and digital readouts change as the data from your car is fed through it. The single step system let you really zero in on different data points to examine things like how your amp draw goes up and your pack voltage drops when you pull the trigger. The "live mode" is cool too because you can see real time what is happening as the car sits at your pit table.

I found the data most interesting when graphed out in Excel (a feature that will be available if future versions of the software). I was actually able to see the effects of the ESC's "torque control" on the amp draw and RPM. Needless to say, it wasn't what I would have expected by reading the instruction manual included with the ESC.

I was running a GM V12 in some of the tests and according to the instructions the current is limited for a set amount of time and then it gradually goes to no torque control with full throttle. I had this torque control set for 1 second. What I really found was the torque control was so limited during that second, my RPM actually flattened out and then spiked up to full speed once the second was done (see graph at left). This could easily explain why my truck seems to just break loose at different times when running it.

I was also able to see where the tires on my off-road truck would break loose and then gradually gain traction. The graph showed that the RPM would quickly peak, then slowly drop a bit while the throttle position never changed.

The Data Recorder does what it says it will do and the information provided is something that has never been commercially available before. It won't completely replace your motor dyno or your battery matcher but could be just as valuable when you want real world performance figures.

While there are a few things I would like to see added I understand that some compromises were needed to keep the Data Recorder affordable. I'd like to see an additional memory for more data, faster sample rates, an extra RPM sensor or two, a way to monitor motor voltage, a place for a for/aft and side-to-side angle (pitch) sensor and maybe a couple of sensors to monitor suspension movement. But having all of this available in one unit would most likely drive the price much higher and make it unaffordable to many.

Eagle Tree Systems has packed a lot of features in this unit for only 150 bucks and they are features that the vast majority of RC racers can use. We can only hope that once this unit is successful that they consider making more dedicated versions for motor/battery performance and another just for chassis tuning.

If you are looking for a fun and useful tuning tool then you have to get the Eagle Tree Systems Car Data Recorder. If you don't and your competition does, you'll be sorry. It just might make the difference between winning and being an also-ran.

Available soon at HobbyShopper.