Model Forum / Radio Controlled / Land Models / December 2003

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.

Pictures available at http://www.hobbytalk.com/recorder/