SPV1 – Preparing the Stock Chassis

I really like the idea of two or more of these cars chasing each other around a track, so that’s now the first objective. And I think this also suggests a name for these vehicles – Serial Pursuit Vehicles, or SPV1 and SPV2. I’ll need to decide on the colour at some stage, too ;-).

I have not raced RC cars since I was 15, so I’m no expert on modern RC cars. In those days everything was simpler; we used to charge our NiMH cells from a car battery through a single, fat 1 Ohm resistor. And speed controllers got so hot they would do much more than fry an egg if you got near them (that’s linear regulators for you). But I am quite impressed with the Quanum Vandal kit from what I can see so far. It certainly looks sturdy enough for my planned use, which will be on smooth-ish concrete and has a decent amount of adjustment for the steering and suspension.

For the build, there are unused holes in the chassis tray that can be used to mount a platform for more components. It also looks as though the driveshaft could be used for an optical odometer when the time comes.

The battery area can also be used for other components as we will mount the batteries themselves elsewhere.

On that note, we will be adding a certain amount of weight, so it seems sensible to adjust the mounting points on the suspension to the stiffest position, front and back.

One potential issue is the orientation of the ESC, which has the signal wiring coming out immediately adjacent to the drive shaft. This might create a wear-risk over time, so all I have done is reverse the ESC. The motor wires now come out by the drive shaft, but they exit vertically and so there is no chance of them interfering.

Lastly I am removing the small, bash plate at the front. This takes up space that will be required for other components and is not needed anyway as the car will not be crashing ;-). It also gives two more screw holes at the front that might prove useful for mounting more stuff.

Apart from that, we are done with the basic chassis adjustments. In the next post we will add extra capacity for components with some flat plates.


Line Following Model Car

This is something I have wanted to do for some while for fun. Note that it has nothing to do with my work at Manna, so don’t make any assumptions about the technologies being used! I also don’t get much spare time, so updates are likely to be irregular.

This is experimenting for fun, so may go in a number of different directions. However, I do want to see how close I can get to a car that accurately stays over a line, steered using Ackerman steering rather than a differential drive. This sounds simple but most examples I see seem to be too ‘approximate’, too slow or not very smooth.

Software / Hardware Approach
I’ll predominantly be using Python and open source libraries such as OpenCV and ROS. Probably ROS2, in fact. Where we need speed, we’ll use C++.

The usual suspects will be present, such a Raspberry Pi and Jetson. I’m also interested in the OpenMV unit, stereo and depth vision, RFID, mesh networking and others as things progress. For example, maybe having two cars maintaining distancing on the same circuit.

Chassis Selection
There are a vast number of notable car projects based on different chassis. and with different levels of aspiration from simple line following through to full autonomy. Many examples of the great Donkey Car project are based on the Exceed 1/16 scale truck. At the other end of the spectrum is the MIT RaceCar project and derivations of that such as Racecar/j. This also has some great support material available from others, such as Jim at JetsonHacks.

I want something a little larger than 1/16th, so have picked a 1/110 scale car from Hobbyking. The Quanum Vandal 1/10 buggy is particularly affordable and comes as a kit or assembled with ESC and motor. I picked the latter for simplicity. With a 2S battery pack, it should hopefully not be too fast for my purposes.

From the images on the website, it looks as though it should be simple to build on a couple of platforms for components – there are some unused holes in the baseplate. I’ll probably also want to set up odometry of some sort, and there look to be some options for that, too, maybe from the driveshaft, wheels or electronically.

In the next post, I’ll go over prepping the kit before making the first modifications.