Who frequently drives on a race track one fine day wants to know his laptimes. Therefore he can either give his mechanic the stopwatch and a pen in the hand or can take a look at the expression of the official timekeeping. At some point this will not be satisfying anymore, because after 10 laps the driver can not remember why he was so fast in the fifth lap. Therefore a Laptimer is needed, because it shows him at the end of each lap the laptime, and he can directly assess what the “other” line has brought. In the mode "Running lap time" you can focus on certain points of the track in order to evaluate whether he has become faster.
The Laptimer among all Laptimers is the MyChron Light from AIM. Actually everybody has it. It is available since 10 years in the version of MCL and 4 years ago his “big” brother TG came to the dealers. Both record the lap times very accurately with infrared and 2009 a TG with GPS will come. This GPS does not measure with a tolerance of +/- 1/4 seconds as its competitors do, but only with a tolerance of a few hundredths.
The motorcycle track days participants as well as any other circuit driver is a typical customer of Ulli Mesch, the head of memotec GmbH, since 1995 the exclusive importer of the products of the worlds leader AIM (laptimers, data recording and racing instruments) in the German-speaking markets. Memotec Messtechnik is market leader in its distribution area as well and quite well known for its acknowledge and perfect service.
"Good service does require even better knowledge about the products and their technical background, context, and weakness," says Ulli Mesch, "and it is not enough for a distributor to only know the key figures of his product (displacement, power, weight and price) and then at the test drive he does not know which button to press to start the engine, and even worse which button to press to turn it off again. And like any other product the Laptimer has physical limits which decide on whether the lap times are displayed accurately or not. "Exclusively for the Circuit Magazine Ulli Mesch explains the readers the secrets of lap timing, what should be noted and how to optimize the reliability and precision of measurement.
AIM MyChron 1
"We are selling Laptimers for 13 years now and the first Laptimer ever sold was bought by Norbert Vettel on the 18th of December 1995 for the kart of his son Sebastian. This was a MyChron 1 with inductive tachometer. That Laptimer still had an IR transmitter in a black ABS housing with 16-way -coding options, so that each MyChron user was able to set his own "signal set" without disturbing others or being disturbed by them. Yet soon we had to recognize that 16 settings are not enough, we would have needed hundreds or even thousands of them. So a standard AIM signal without adjustability was introduced. But obviously we had reckoned without the host as no one, neither at memotec, nor at AIM would have thought that people who buy a Laptimer do not read their manuals. Luckily, we are present at many race tracks and see what people are doing.
After I (Lower Saxony) am living in the political territory of the Swabians for more than 30 years now I know the philosophy of the value added to the last detail and here is the following explanation of what our customers do and why this report is available here: the customer buys a lap timer and immediately calls the buddy who recommended it to him: "Hello Karle, the thing has arrived now. What must I do? If Karle would have an ass in the pants, he would say: "Take a look at the manual. Everything is explained in there.” He does not do this however and says instead: "Don’t be so stupid just try it out and somehow it will work."
At this point, our manual has lost. It was not recommended but ignored, and even vilified. Although everything is written down in the manual that one needs to know about the Laptimer to get everything out of it the manual is being ignored.
But what has this to do with this magazine? It's simple: the manual was attached to the Laptimer (for free) – no extra charge and is therefore worthless. But for this magazine was paid and a half read newspaper will not be discarded. It remains at its place till it has been fully read, because one has paid money for it.
Don’t worry, no boring instruction manual is going to follow, but we will tell you what you should not do in order to not influence the correct function of the logger and why some things are different than people think.
Function principle lap time keeping
The Laptimer needs a fixed point on the track where he can trigger accurately and reliable lap by lap. There are currently four popular methods:
Manual timing
The driver presses a push button when passing a certain point of the track, e.g. at the finish line. This is not very accurate and is often forgotten in the heat of the moment..
Laptiming using an infrared beacon
This is the most common method because it is inexpensive, accurate, reliable and widely applicable. At the edge of the track is
ONE only IR transmitter which sends a coded infrared light signal. “Coded” means that the light-on and light-off phases, pulse times and intervals are precisely defined and are adhered to. In order not to be disturbed by Transmitters from other manufacturers or to disturb Transmitters from other manufacturers every manufacturer has its own frequencies.
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| Infrared transmitter |
Infrared receiver |
The error of measurement in IR lies, when it is correctly installed and used, at the third decimal place, i.e. in the range of milliseconds (1ms = 1 / 1000 s). But it is somewhat inconvenient to handle the transmitter, because if you forget it on the pit wall it’s gone as everybody can use it. It also requires electricity - i.e. maintenance.
Lap time recording via magnetic strip
AIM magnetic field sensor
In this process there is one or more (for split times) permanent magnetic strips route across the track as trigger and a magnetic field sensor passes over. Almost all go-kart tracks in Europe are equipped with magnetic loops, but nearly all automotive and motorcycle racing tracks (except of Hockenheim and some tracks in France and Spain) are not equipped with it.
Laptiming by a magnetic strip is extremely accurate, reliable, convenient and cheap, but for motorcycles it is not very practical (as opposed to racing cars and karts) because of the large ground clearance and related mounting deficits.
Lap time tracking via GPS
The latest thing is currently lap timer, which are triggered via GPS coordinates. This very convenient, because no transmitter is needed and no maintenance is necessary. You go with the lap timer to the finish line and "set" the measure point. The manufactures of modern devices provide their customers the software, with which you can set these measuring points over the coordinates, which you can find in Google Earth.
The problem of the cheap GPS lap timer is the low sampling rate. There are devices that only detect the position of the device on earth once a second. And because each measurement has a tolerance of less than + / - one measurement cycle, these lap timers are only good for hikers with orientation problems.
The slightly better ones with a sampling rate of 4 Hz, still have + 1 / 4 second measurement inaccuracy. With lap times at 8 minutes on Nordschleife it is ok but if I would go to the karting track, I would have a serious problem in being taken seriously. Here are 10 Hz or more announced. 50 Hz or 100 Hz would be a bit exaggerated, because prices rise exponentially to the sampling rate and because of a few hundredths tolerance only factory teams in Moto GP spend € 5,000 more than others do. The use of these devices only makes sense if a visible reference point on the route of each station is available.
AIM MyTach
Absolutely trendy for beginners and freaks is MyTach from AIM. MyTach is such a GPS-device and can be installed in the cockpit, shows the lap times, speed, above sea level, etc., stores the data and transmits them to the PC. As distinct from the most others wristlet-trainers the MyTach has an adjustable sampling rate (1-10 Hz) and is therefore also suitable for the semiprofessional motor sport. And when one goes for jogging, mountain biking or skydiving you connect the MyTach to your wrist and you are able to see how long you have been running, how many meters you have done or how fast you fly during free fall.
Lap time recording via transponder
Furthermore lap times lap times, sector times and driving times from A to B also with wireless transponders, infrared-transponders and light barriers are recorded.
The most known wireless transponder comes from AMB in Netherlands, whose transponder is used at nearly every race event. Here coaxial-antennas have to placed, over or next to passing by vehicles (or horses, bikers, runners, skiers etc.), which identify the transponder and record the time. However the necessity restricts the flexibility of the AMB-systems. The measurement accuracy is extremely high.
With infrared-transponders this problem doesn’t exist, because this principle is independent from antennas or other equipment along the track and can be used everywhere without any preparation. We have developed such a system together with the firm Schildknecht and offer it under its brand name Laptrix. For the measurement accuracy the before regarding to the IR-lap timers told counts.
Since light barrier measuring in circuit racing for lap time recording are not (anymore) used, we don’t want to go further into it.
Advantage and disadvantage of the function principles
Each of these measurement methods has its advantages and disadvantages and requires special procedures, to ensure the reliable function of the system. The magnetic field sensor is absolutely foolproof, but with manual triggers it is possible to forget to press. But the most can be done wrong with the infrared measurement.
The signal of the IR-transmitter is clocked infrared light, so e.g. ON – OFF – ON – OFF – ON – OFF – PAUSE – ON – OFF – ON – OFF – ON – OFF - Pause, and so on. The times of these cycles are defined by each manufacturer.
It is permanently send in form of a light beam with 18° spreading by the Emitter-diodes, and as soon it is seen by the IR-receiver, the lap time appears in the display.
This means the further the transmitter is distant, the bigger is the area, in which the signal can be captured. This also means, the further distant you drive by the transmitter, the less important is the installation height of the receiver. And this also means, the further you drive by the transmitter, the sooner you drive into the light beam. To enable this, the transmitter on the pit wall can be turned 9° into driving direction and one then always drives into the beam at the same place, independent from the distance to the transmitter. Referring to the image above the driving direction would be in this document from the bottom up.
User advice on an IR-transmitter
The narrower you drive by the transmitter, the shorter is inevitably the time, which the receiver has, to recognize the signal. At a distance from 10 m and ideal height this are 3.17 m. With 252 km/h you travel 70 m per second, with 252 km/h you drive through the 3.17 m big beam in 0.022 seconds. Not only because of this, the receiver needs a free sight to the transmitter.
Bright minds have already meant, that the more transmitters are set up, the stronger the signal is and the more reliable the system works. Such as with singing, where a complete choir sings louder than a soloist. Far from it! Because the lap timer only responds to the coded light. That’s the reason for the warning on the transmitter.
If two transmitters send, perhaps even from different manufacturers, it could look like this:
The receiver now ignores what he sees there, because that's not his signal. This effect is independent of from which manufacturers the transmitters are coming from, because each manufacturer has a different signal code. And also not with transmitters of one manufacturer, because they are not synchronized.
As can be seen from Figure 2, the cone has at 20 m distance (width of the start / finish straight on many tracks such as Hockenheim, Nurburgring and Monza) a diameter of 6.23 m, which means that In this case, the distance from one to the other transmitters must be at least 6.23 m to ensure the reliability of operation. For "security" reasons 10m should be adhered as there are transmitters with larger viewing angle.
What we learn from this: who can make party together at night should also be able to clarify in the morning who draws up the transmitter to avoid the confusion.
An occasionally occurring phenomenon is the picket fence effect: when the sun is low and you drive past a fence or trees and the solar radiation interrupts the corresponding frequency in the IR receiver a lap time might be triggered.
What you have to do
Quite stupid was the idea of a mechanic who acquired the driver's lap times via a lap timer a few years ago. For this he had the transmitter mounted on the motorcycle and he was standing with his MyChron in the hand at the pit wall. So many supposedly broken lap timers it had not given so far, and the good mechanic never had so many new “friends” in his life.
The powering of the transmitter can be done via 8 AA batteries at 1.5 V in normal mode (range with fresh batteries approx 15m). We recommend at distances of more than 10 m to change to high power mode (range 30 m). In this state an external 12V battery is obligatory.
The Lap timers are powered by a 3V button cell CR 2430 battery. To prevent that batteries "stand out" because of vibrations and crushes and the lap timer therefore turns off you should (when having this problem) put foam rubber in the cavity.
Specific problems with the by AIM offered GPS devices are not yet known. There are two or three things that need to be considered when installing the antenna. Furthermore one need to consider the cold start procedure during which the device searches 1-2 minutes for satellite signal while the car is standing still. The GPS module stores the distance data (measuring points for laps and split times), and recognizes on the basis of the coordinates stored in the Lap timer on which track you are. Tutto bene. However, the ordinary AIM customer uses the GPS not as a Lap timer, but for data analysis (over ground speed, gyro, inclination angle, curve radii, trajerctory, etc.). For the evening beer discussion in the paddock (measured by GPS slope) now you also can document how many meters long your wheely has been - and who will pay the next round of drinks.