Articles

Tacho Tactics
by Simon McBeath
Excerpted from Racecar Engineering Vol 7 No 6
September 1997

The acquisition of data appears to have become complex and expensive. But a surprising diversity of information can be obtained from the simplest of all data-loggers - the recording techometer - at a cost within the reach of most amateur motorsports competitors.

The least expensive form of data-acquisition system, of course, is the notebook and pen. Being dependent on the driver's memory, however, the information is not always complete or reliable ... With the advent of the electronic storage of analog or digital signals, from sensors measuring a variety of engine and chassis parameters, a huge amount of data can be collected from multiple channels for analysis - but usually at considerable cost.

A useful compromise between these extremes is the recording tachometer (also known as the "intelligent rev-counter"), which has been available for over a decade. This device is able to record, play back and, with the appropriate software, display on a computer screen the last few minutes of engine RPM against a time base.

The market in recording tachometers is shared by two well-known motorsports suppliers, namely Stack and Tach-Mate UK. The UK company, Stack, claims to have been first in this market, about 11 years ago. The current ST400-series recording tachometers are based on Stack's excellent no-waver stepper motor movement tachometer, with memory options of 12.5min (at 20 samples per second) or 25min (at 10 samples per second). An on-dial replay facility is provided, with a choice of playback speeds, and a shift light is standard. Remote shift light options, including a helmet-mounted version, are available at extra cost.

Analysis and storage of RPM traces becomes possible with the PC download lead and software (DOS-based). Lap and segment markers can either be added manually, or automatically using the infra-red track marker system. Lap and segment times can be shown alongside the graphical information on the PC screen. The software includes a unique 'lap overlay' feature called % LAP PROP (lap proportion) which scales the timebase of overlaid runs to fit them both to full screen, simplifying speed comparisons.

At the time of writing, the recording-tachos started at £299, with the PC Download package a further £125.

'Tach-Mate' is produced in the USA by Czech-Mate Enterprises, and marketed in the UK by Tach-Mate Ltd. This system connects to virtually any electronic tachometer, recording output at 30Hz and providing 8min standard memory, upgradeable to 30min . Also endowed with an on-dial replay facility, normal-, half- or double-speed replays can be selected. A 'rewind' function allows the user to replay any interesting part of the output repeatedly for closer inspection.

The 'PC UPLOAD' analysis software is WindowsTM based, offering multiple-run viewing. Other add-on options include an axle sensor and speed recorder kit, and a remote shift light option. At press-time, the basic unit cost £185, PC UPLOAD adding an extra £145.


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