Rally trip meter tips

Having got excited about classic car rallies, we decided to go the whole hog and fit a rally trip meter. This was of course an opportunity to spend many hours as a contortionist upside down under the dash.

The model selected was the Brantz International 2 Pro from Right Track Enterprises Ltd; probably the most popular device used by classic car rally enthusiasts. It is a highly accurate odometer with dual displays and is ideal for stage rallies. The odometers can be accurately calibrated in miles or kilometres to match a measured distance on the rally. The second trip meter can be zeroed at any stage and even run backwards (useful, for example, when a navigational error is made and one is retracting ones steps).  Importantly, this unit is allowed to be used in most regularity rallies, as it merely duplicates the car's odometer and doesn't calculate average speed directly.

Brantz International 2 Pro rally trip meter

Fitting the unit is quite straightforward, with direct connections to each side of the battery, so as to reduce interference from other circuits/devices. An in-line 2A fuse was fitted on the live wire. The only two difficulties are fitting some sort of impulse sending source and where exactly to fix the Brantz unit so it is clearly visible (without cutting chunks out of the dash board or looking too much like a lash up).

The unit requires a Brantz sensor. Several types are available. The neatest solution is a small sensor that screws in between the gearbox speedometer drive output and the speedometer cable. Unfortunately, although two sizes are available, both have metric threads (18mm x 1.5mm for Ford/GM and 20mm x 1.5mm for Japanese cars). I'm amazed that no one has made a UNF version for British classic cars – there must be sufficient MGs and Triumphs to justify this, surely? Other sensors include wheel sensors or prop shaft sensors, though both are quite exposed to the elements. Electronic sensors are also available for modern cars.

For the MG Midget, the solution is to fit a Brantz Universal Speedometer Cable Sensor. This is a plastic unit that fits on a straight section of speedometer cable. The outer sheath is cut, a 13mm section removed, the cable passed through the device which replaces the segment removed, then back into the speedometer. The unit is clamped securely to both remaining portions of outer sheath with small fuel line clips, which make a neater job than jubilee clips. I mounted the unit about four inches behind the speedometer on a nice straight portion of cable run.

Brantz Universal Speedometer Cable Sensor

Fitting schematic from Brantz instructions

Sensor as fitted, just behind speedometer

The rotor within the unit floats in air, so as to put no additional strain on the speedometer. The speedometer cable passes through and is gripped by the centre of unit. The MG cable was quite a tight fit, requiring the guide hole to be enlarged slightly. The rotor generates five pulses-per-revolution of the cable.

Sensor fitted, the next job was to mount the Brantz somewhere. The first effort was on the dashboard in front of the passenger. A stainless steel bracket was fabricated to avoid drilling holes in the dash. Although serviceable, the angle of the dash, sloping away, meant the face of the unit was slightly obscured – a vertical arrangement providing much clearer visibility. The final solution was to mount between the radio (fitted below the centre of the dash) and the transmission tunnel, just ahead of the gear lever. This offers excellent access to the controls for both driver and navigator. However, it did require removing the radio unit (twice in the end) and routing cables through the bulkhead. A new stainless steel bracket was fabricated and fitted to the underside of the radio console, leaving space behind to store the Brantz remote control unit. The final result is quite pleasing.

Brantz rally trip meter fitted to MG Midget "ABW"

Thanks to Esme and Peter for the kind gift of the trip meter and thanks to Peter for assistance with the fitting. Now all we have to do is justify all this effort with a good result at the next rally.