Low-Cost Data Acquisition

So you’re an up-and-coming FSAE team, and it’s time to expand your data acquisition capabilities. But you’re on a limited budget, so where do you start?

When the term “data acquisition” is mentioned in the FSAE context, it's typically in relation to an on-vehicle data system with sensors and data loggers, sometimes telemetry. This equipment can be really expensive, but isn’t always needed to take valuable measurements. In this post I’ll outline options and strategies for low-cost data collection that you and your team can use at any test session. This will be focused on vehicle-level data, so for a higher-level overview on ways to collect and use data, please refer to Esther Unti’s article: Four Ways To Use Data

Start with a stopwatch, but strive for timing gates

Lap time is the most valuable data to collect if you’re trying to make the car faster because it literally tells you if you’re making the car faster. For short, repeatable tests, like skid-pads of various sizes or acceleration timing, using a stopwatch is a great start, but a timing gate system would be better. You can purchase a timing gate system for a few hundred dollars, or build one from scratch using photoelectric beam sensors like the ones used for automatic gates or garage doors connected to a timer with an external trigger. Lap time data is the answer to the question, “but did it make the car faster?”

Low-cost digital thermometers are available

Some thermometers have external probes that can be used to measure fluid temperatures.

We don’t want our racecars to overheat so it’s important to know the temperatures of the fluids. Thankfully there are inexpensive digital thermometers available, many of them designed for high temperature cooking applications. Yes, I’m talking about meat thermometers. Temperature data collected with a meat thermometer is better than no temperature data at all, and you’ll want the one with the external probes for easier mounting. By aiming an action camera at the readout you can plot rise-time and steady-state temperatures of your fluids. 

Aim cameras at sensor readouts

Aiming an action camera at a sensor readout or the screen of an imaging tool can help quantify vehicle attributes during a test run.
If you decide to do this, make sure the imager is securely mounted!

This “aim the camera at the sensor readout” concept can be applied in other ways too. I know of a team that pointed an action camera at the screen of a thermal imager clamped to their roll hoop. Watching the video after the test session, they were able to extract their tire warm-up time, temperature gradient, and peak temperature, which helped them tune their set-up. 

Chalk the tires

Chalking the tires can indicate tire flex by looking at where the chalk is scrubbed off by the ground.

An old autocrossing trick that costs no money at all is to put chalk on the outer sidewall of the tires before a test drive. During the drive, the tires will flex and the areas that contact the ground will scrub off the chalk. The result is a measurement of sidewall deflection that can be used alongside tire temperature to inform tire pressure and camber adjustments.

Zip-tie suspension travel indicators

A zip-tie around all four dampers shaft can indicate a variety of attributes related to suspension motion.

Another zero-cost trick is to put a zip-tie around the shaft of each damper. By sliding the zip-tie up against the damper body before a run, the resulting suspension motion will give you a measurement of your maximum suspension usage. This information is useful to see if you’re bottoming or if there’s left/right asymmetry in the suspension, or if your anti squat/ anti-dive adjustments are doing anything.

Airflow

Tuft testing can help visualize flow at various vehicle speeds.

Visualizing aerodynamic flow characteristics can be done with a “tuft test” by taping short lengths of yarn all over the place. Instead of yarn, try using short lengths of ripstop nylon, which is a lighter material and lays flatter than yarn. Tuft testing is valuable for visualizing areas of attached and detached flow, and using a camera pointing at areas of interest can provide even more detail (as long as the camera isn’t blocking the airflow). Another method uses “flow-vis” or a liquid mixture of oil-miscible dye (trans leak tracer, dry tempera paint, etc.) mixed with mineral oil. Brush, dot, or spray the fluid on, depending on the viscosity. Wrapping wings in white vinyl can provide good color contrast while facilitating cleanup.

A lot can be gleaned from photography

What does this photo tell you about the driver’s actions and the car’s trajectory?
Photo courtesy of Harry Quackenboss

Video and audio recordings of your test sessions can also provide valuable insights. Use single-frame snaps from videos to analyze things like camber angle, tire distortion, roll and pitch angles. Audio recordings can help identify vehicle behavior like traction control activation, tire squeal, engine starvation, squeaks and rattles. If the microphone is mounted on the car, wind noise in the audio can be mitigated with mic coverings and strategic placement. Having the driver wear white or neon-colored gloves can help improve the visual contrast to track driver inputs in recorded video, and watching the lag between where the driver is looking and where the car is pointing can indicate driver training opportunities.

Smartphones

Use an old smartphone as a cheap data logger. These things have so many sensors in them, and chances are you have an old one gathering dust in a drawer somewhere. Numerous apps exist for Android and Apple products that allow sensor logging and data export, and are usually free. Rigidly mount an old smartphone near the center of mass of your car and collect 3-axis acceleration and yaw rate data, or stick one to the steering wheel to get steering angle. 

If you’re looking to use more than one system to record data, synchronizing multiple data streams can be tricky, but it’s possible. For decades Hollywood used a “clapperboard” to synchronize video and audio recordings, so it shouldn’t be too challenging to create an equivalent event or “flag” in all the data streams that can be used as reference. A sharp stab on the brakes or a distinct steering maneuver, anything that appears in both data systems can be used to help sync them during the analysis process.

process and Analyze the data

So let’s say you’ve taken this advice, and you’ve now got plenty of zip-tie measurements, endless hours of video and some .csv files uploaded from an old cell phone, and now someone’s asked you, “show me the data” and you’ve got to provide the goods. Part of what separates expensive data systems from low-cost methods is that the expensive systems typically do some filtering, post processing, and provide a fancy user interface with plenty of options to streamline the visualization process. In the case of the low-cost methods listed above, there are additional steps required to consolidate, review, and analyze the video, photos, and notes into meaningful spreadsheets and charts. These additional steps should not scare away any team that’s ever listed “documentation” or “knowledge transfer” as one of their goals. 

If you want a historical perspective on some of the clever methods used to record data on race cars of the past, check out Chapter 13 in “Race Car Vehicle Dynamics”. I was surprised by a few of the relatively low-tech, but effective methods described, and it underscored for me how fortunate we are today to have modern technology at our fingertips.

Data collection always takes some effort, but it doesn’t have to cost a lot of money. Next time you plan a test session, I encourage you to think about simple, low cost ways to extract meaningful data from the session to make the most of your precious test time.