Losi 6iX Project
Page 2: Upgrades!
Since this car is so fast and I have never used surface telemetry
before, I decided to add some Spektrum Telemetry systems. The RTR
receiver does not have built-in telemetry so I added the TM1500
telemetry unit which comes with a temperature and voltage sensor.
The temperature sensor wraps around the motor and the voltage sensor
attaches to the battery leads. There is also a built-in receiver
voltage reading. The unit didn't fit inside the receiver box so I
put it on top with some servo tape. I also added a brushless RPM
sensor which just connects to two of the three motor wires.
If you want to read speed you need to take the motor RPM reading, divide
by the final drive ratio, and multiply by the circumference of the
tire. In theory this works fine but it has two problems. The
first problem is that when you are spinning the tires while drifting
you will read a false high speed. The second problem is that you
are not actually measuring motor RPM, you are measuring commanded motor
RPM. For example when you put on the brakes you get a huge RPM
reading even though the motor is actually slowing down. For this
reason I really wanted a real speed measurement which meant adding the
pricey GPS module which I connected atop the servo. Not only do
you get speed, you also get coordinates (latitude and longitude) and
elevation. This is really for aircraft, but it works fine
here.
The main disadvantage to telemetry is that you can't really look down at
your controller while your car is going 60 mph or you are going to
crash it. You can save the data to a file and look at it later
though.
When the stock tires wore out (one week into ownership) I needed a
replacement that would last longer, but no one makes anything that is a
direct fit. The left hand image shows the original 17mm hubs, and
the right hand image shows the replacement square drive hubs that will
allow me to use GRP tyres.
The new tires are the same diameter as the old, but as much wider.
They are also made from a significantly harder compound with reduced
traction but increased life.
Here is a comparison of the old and new tires. The new versions
protrude from the fender well about half an inch, but at least they
work.
©2018 Eric Albrecht
