Expanded Halda Twinmaster and Tripmaster Calibration Table

Recently I acquired a Halda Tripmaster and a set of Halda calibration gears that can be added to the Halda Tripmaster to adjust the odometer reading to match the distance used by the rallymaster.  These Halda calibration gears are made up of two types of gears:

  • X-Gears
  • Z-Gears

These gears are shown in the photo below.  The X-Gears are the larger diameter gears with the three central holes, while the Z-Gears are the smaller gears along the bottom of the photo with the one central hole.

Halda gears

Typical Halda Calibration Gears

The same Halda calibration gears can be used in either a Halda Tripmaster or a Halda Twinmaster.

Over the years I have been the navigator in several rallies with Harald von Langsdorff.  Harald has two Halda Twinmasters, one currently in Canada and one in Europe.  By the way, I believe that Harald would sell one of his Twinmasters if anyone is looking for one.  Anyway, when I got my Halda Tripmaster with gears, we prepared a list of all of the calibration gears that we had between us, so if we were to enter a rally using a Halda odometer, then we would have a list of the calibration factors available to us.  This is also important because potentially the rally could conducted using either miles or kilometers.

When we assembled the list of gears that we had between us and then compared this list with the Halda calibration table, it became obvious that we had some X-Gears with fewer teeth than shown in the official Halda calibration factor listing table and in addition, Harald has the elusive 45-tooth Z-Gear that is not included in the Halda calibration factor listing table.  The X-Gear listing in the official Halda calibration table has a lower limit of a 118-tooth X-Gear, while we have an X-Gears as low as a 95-tooth gear. The problem then became how to determine the calibration factor for those gear combinations that were not shown in the available Halda tables.

In order to solve this problem, I used the data in the official Halda table to “reverse engineer” the needed information to expand the table.  I then prepared an Excel spreadsheet to calculate the expanded calibration factors.  There are some very minor differences which could be attributed to such things as computer accuracy and rounding/truncation issues.  Any differences are not significant with respect to gear selection.

This table of expanded calibration factors is presented below.

Expanded Halda Calibration Factors

Expanded Halda Calibration Factor Table

I also prepared a chart showing these available calibration factors.  This chart is not particularly useful for the calibration process itself, but it is useful to identify any calibration factor gaps that a rally crew might have.  This chart is shown below.  I am somewhat disappointed that the chart does not reproduce very well, despite looking great on my computer monitor.

Expanded Halda Calibration Chart

Halda Gear Selection Calibration Factor Chart

I plan to install my Halda Tripmaster in my Saab 99 this summer and this table should be useful in getting it calibrated.

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13 Responses to Expanded Halda Twinmaster and Tripmaster Calibration Table

  1. I have a 1960s metal-case twinmaster (Cortina GT/MG B) which I would be willing to sell.
    Jim Novotny mnovotny@gwi.net

  2. Terry walker says:

    Sorry Steve ,its a twinmaster i need ,metal case to be period correct

  3. Simon Hambly says:

    Hi Steve – Can I just check my understanding of ‘Calibration Factor’ on your excellent Halda Calibration Factor graph above. Is that the number of turns of the speedocable prior to the 8:1 for it to read 1.00 distance unit? Many thanks, Simon

    • jfnsr says:

      I still have a Twin Master. I was offered $1,000 and counter-offered $1,500. Considering the EBay and Euro e-market ads, my request is fair. I can send pictures to show it’s not a junkyard find.

      Jim Novotny Maine, USA


    • Hi Simon,
      I have just returned from some travelling and I am getting settled back into things. Your understanding is correct with the further clarification that the distance unit is one mile. In other words the base set-up for the Halda odometers was based on 1000 revolutions of the speedometer cable per mile.
      I would like to add that you have done great things with the development of the GaugePilot rally computer.
      Steve McKelvie

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