Friday, April 27, 2007

How-To: Nitro-to-Brushless Conversion: Part 2

Part 1 can be found here.

The second part of my brushless buggy project was assembly of the non-nitro-specific portion of the Losi 8IGHT kit. First, I assembled all of the mechanical components that required no modification. Doing so entailed putting about 200 parts (plus screws) together, which wasn't so bad, since the manual is quite clear. The hardest parts were filling the diffs and especially the shocks with silicone oil of the appropriate viscosities; getting all the air bubbles out can be challenging. Here's a photo showing the car at this point in the construction; it also illustrates just how off-center the center diff is.

Next, I modified the electronics box by cutting off the portions designed to house the receiver pack and brake servo. I'll be powering the Rx and the servos using a voltage regulator---called a battery-eliminator circuit in the RC world---running off the main battery. Additionally, I'll be using the motor to provide braking, which will eliminate the ability to adjust front/rear brake bias, but also save a lot of weight, room, and complexity. Here's a photo of the car with the modified electronics box, Rx, and steering servo installed:

Note that I have only a very short length of antenna oriented vertically and potentially projecting out of the body. (The antenna is housed inside the orange antenna tube at the right front of the car.) I can do this because my radio system, the Nomadio Sensor, uses the same 2.4-GHz band that cellular phones employ. Between this high frequency and the spread spectrum1 modulation that Nomadio radios use, the transmitter-receiver link should be very resist to noise. (Come to think of it, noise is another reason to go electric; all those moving metal-on-metal interfaces in a nitro engine put out a lot of radio static.) I should also mention that the link is bidirectional; the receiver---really a transceiver---cames with temperature, voltage, and speed sensors, and it can send telemetry back to the transmitter---also really a transmitter. I'll try to post photos of the transmitter later.

By the way, in the above the photo, you can see the body I painted for the 8IGHT. That will be the subject of my next post on this project.

Part 3 can be found here.

1 Frequency-hopping spread spectrum,2 if you must know. Nomadio claims this is superior to direct-sequence spread spectrum, but I would think the opposite would be true.
2 I should point out that actress Hedy Lamarr contributed significantly to the development of spread spectrum.

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