Teaching you everything I know about timekeeping (infodump #1 of many)
I’m making the assumption that you subscribe to this newsletter because you enjoy (at least sometimes, depending on whether your fave is doing well or not) watching circuit-based motorsport. I’m therefore also making the assumption that you know the really basic things about how pole position usually goes to whoever sets the fastest lap time in qualifying, and that the race winner is the person who gets to the chequered flag first. You might be nerdier than the casual fan, you might not be, but you at least know enough to tell whether your fave is having a good day.
But what I want to do today is dig into the stuff you see on telly and on live timing websites that might not be so obvious. My hope is that I hit that good combination of information and entertainment.
First of all, let’s talk about how the timing actually works. The difference between karting and F1 is budgetary, but the concepts are exactly the same. Each vehicle has a device on it called a ‘transponder’, which broadcasts an RFID signal of that transponder’s ID number. Think, something like a 6-7 digit number. The transponder will broadcast something like ‘8971235’. Each transponder broadcasts a different number, and that’s how we tell the vehicles apart. As a timekeeper, I see a race as a bunch of transponders moving around the track. What they’re attached to is less relevant. Could be a truck, could be a le mans prototype, could be a six-year-old in their first ever go-kart race. As long as their transponder is broadcasting a signal, we’re good to go.
Once we’ve got some transponders broadcasting signals, we need something to collect the data. This takes the form of a ‘loop’ of cable that sits in the surface of the track. It starts on one side of the track, goes across the full width of the track, and then comes back.
In this photo, you can see the loop. It’s the thin black line that’s been filled in with black silicon. White squares have been painted between the two sides of the loop.
Here’s another example, this time with more paint. Do you see the thin black silicon lines? That’s the loop.
There’s a loop at the finish line on every circuit. You might here this line also called the timing line or the control line. They’re all different names for the same thing.
Side note (pet peeve): when you hear people call it the ‘start/finish line’, they’re usually wrong to call it this, unless they’re talking about Albert Park, Circuit Gilles Villeneuve, or Monaco (there are more exceptions). At most F1 circuits, the start line and the finish line are in different places on the track.
If you’re running a small track on a small budget, you’ll have one loop. If you’re running a large track on a large budget, you’ll have lots of loops. Once you’ve got a finish line loop, you’ll have loops for Sector 1 and Sector 2. You might have a loop for a Speed Trap. You might have a loop at pit entry and at pit exit. In F1 you’ll also want two Safety Car Line loops, and indeed a loop every 200 metres around the track to help with positioning, and a dozen or so loops in the pit lane to track pit lane speeding.
The loop cable is attached to a piece of equipment called a ‘decoder’. Every loop has their own decoder. Modern ones look like this, and are a square that’s bigger than an iPad but smaller than a laptop.
What a decoder does is collate information. It knows the time of day, it tracks when a transponder crosses its loop (this is called a ‘passing’), and it registers the transponder’s ID. It passes this information (loop ID, time of day of the passing, and transponder ID) to any computer that’s connected to it. It also handles some other stuff like signal strength but getting into all that extra stuff takes the entertainment~ out of this newsletter.
That’s all the hardware you need, apart from cabling. If you run a small track, your loop cable will run straight into your timing room and into your decoder, and your decoder will plug directly into your laptop using an ethernet cable. If you run a large track with lots of loops and lots of decoders, you’ll need networking but eventually there will be a cable for you to plug your computer into.
And then, all the magic of timing happens in software on your computer. This is where you’ll have your entry list (a list of drivers, along with their transponder IDs), and details of your decoder(s). The rest is… maths.
If a driver crosses the timing line at exactly 2pm, and then crosses it again at 2:01, their laptime is 60 seconds. The reason that IndyCar can do times to four decimal places, and your local indoor rental karting track can do them to only one decimal place, is budget. Cheaper equipment simply isn’t as accurate. The technology is also slightly different depending on the anticipated speeds of the vehicles. An F1 car doing 300km/h is not going to be on top of the loop cable for a long time, so that doesn’t give the loop much time to even register that the car has passed over it. With karting, there’s a bit more time for this to happen.
So far we’ve talked about measuring time, but what about measuring speed? That’s all covered by the equation ‘speed = distance / time’. In F1 you’ll see people given penalties for speeding in the pit lane. You’ll also be shown data about the driver’s speeds over each sector. Here’s what one of those reports look like.
This data comes from multiple loops, all carefully measured in their distance. At the speed trap, the finish line, and the two intermediate points, there’s a second loop 30 metres before the line. Since we know the time of day that the drivers pass these two loops, and we know the distance between them, we (I say ‘we’, but what I mean is ‘the software’) can put those numbers into the equation to get the speed. It’s the same concept in the pit lane - log the time the driver passes the first loop, log the time they pass the second loop, calculate the difference between those two times, and combine that with the distance between the two loops. If the speed is too high, ban fine them!
So that’s how all of timing works… on a good day. What you may or may not have picked up on are questions like ‘but what happens if someone’s transponder stops working?’ or ‘why do commentators talk about someone Breaking The Beam?’ or ‘don’t people talk about a camera being used for timing?’ or ‘don’t all these modern F1 electronics sometimes turn the car into a faraday cage and block all the transponder signals?’ or ‘can you still get a transponder signal from a 7yo’s go-kart if they’re covered in lead?!’
And the answer to those questions is as follows:
What happens if someone’s transponder stops working?
A timekeeper’s nightmare! Maybe the battery runs flat (which happens on transponders that aren’t plugged into the car’s power), or it falls off because it was attached to the car with the world’s weakest cable ties, or it was never on the car in the first place because it’s still on charge in the garage.
In that scenario, we try to use the photocells as a backup. A photocell (sometimes called a light beam, or just a ‘cell’) is another way of generating a passing for a competitor. They’re the primary method of timing in things like rallies where it’s hard to set up a loop. In circuit racing, they’re used as a backup (because transponders are nice and convenient), primarily because whilst a photocell can always generate a passing time, what it can’t do is tell you who the competitor was.
The way it works is that there are two boxes which broadcast an infrared light between them. When something blocks that light, it’s said to ‘break the beam’. A passing is generated (the photocells are connected to the decoder, which means they can send a passing with the time of day to the software), and someone (a user of the software) will have to manually tell the software who that photocell time was (which vehicle it was that passed at that time).
If you’ve ever watched a race and seen someone cross the line and visually they’re first, but they tumble down the order on the graphics, but then a few seconds later they’re in first again, what’s happening there is that they cross the line but their transponder isn’t picked up, a photocell passing is recorded instead, and then a frantic timekeeper is madly clicking around their software to tell it to use that photocell passing instead. Once they’ve done that, the part of the software which does all the calculations uses that information and now the driver is where they should be in the classification.
Now, if a decoder breaks, you’re in big trouble. It’s a very rare thing that happens, and in Big Professional Motorsport what you would do is switch to your ‘backup’ decoder, which has been sitting there collecting data this whole time, and nobody will ever notice the panic you’ve just gone through (loops can connect to more than one decoder at a time). If you’re doing budget motorsport and you don’t have a backup decoder, you’re… fucked, basically. If you can’t record the data, you can’t use the data for your calculations.
Don’t people talk about a camera being used for timing?
A camera can absolutely be useful for timing, but it’s never used as the primary timing device. You know by now that we need ‘passings’ for our calculations, and you can’t get a passing from an image, mostly because which bit of the image would you use?
Where a camera comes in useful is for close finishes. Finishes that are so close that you’ve got yourself questioning the accuracy of the transponder, or wanting to double-check because if you get it wrong then there’s trouble. Finishes that are so close they look like this:
F1 transponders are accurate to 0.001 of a second. When the cars are closer than that, you’ll use the camera pictures to verify that you’ve got the cars the right way around.
Think of the timing line as a very thin line across the track. In the first instance, you’ve got your loop cable running along the line to pick up the transponders. If the transponders don’t pick up, you’ve got the photocells as a backup. And then as an extra set of eyes you’ve got a camera looking at that very thin line. The way the camera works is that it will detect movement in its very narrow field of vision, and will record very narrow images, and then the camera software will stitch them together. That’s why you’ve got all the horizontal lines in the photo above and why the track looks white. The whole track isn’t white, but that narrow white line that’s painted on the surface is, and that’s all that’s being captured. That image is actually several hundred very narrow images, all stuck together.
It’s the same concept in athletics, where the finish line camera takes photos like this:
(And to get really nerdy for a second, those omega logos and olympic rings actually come from an extremely narrow screen on the finish line, which displays images at the same frame rate that the camera can take pictures, isn’t that cool?)
Don’t all these modern F1 electronics sometimes turn the car into a faraday cage and block all the transponder signals?
Yes. There’s nothing you can really do about that apart from say to the team ‘hello please can you build your car differently?’ which isn’t a conversation that will go well.
Can you still get a transponder signal from a 7yo’s go-kart if they’re covered in lead?!
No. And there’s nothing you can really do about that either except hope that one day the driver will gain some ‘internal ballast’ and not need so much lead on their seat.
That’s enough for now, I think! Hopefully you’ve learned:
if you see your favourite driver go tumbling down the order, it’s not necessarily because they’ve crashed
the start line and the finish line are often not in the same place
what a finish line camera is useful for
how much equipment there is at the finish line
to make sure that if you ever race, you ensure that your transponder is charged fully and not surrounded by material which could block the signal
Next time we’re going to get back into reading books. Stay hydrated <3