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News - January 14, 2018 - Simple Rally Computer 1.35 released and documentation updated.  In this release, a bug has been corrected.  Mileage is no longer lost when the app is not on the main screen, such as during a pause.

News - Mary 10, 2017 - Simple Rally Computer 1.30 released and documentation (1.30-1) updated.  

News - February 26, 2017 - Simple Rally Computer documentation updated (Documentation page, this web site).

News - January 6, 2017 - A simple rally computer is available in the Google Play store at just $6.00 USD.  Documentation is available on the Download page of this web site. 

News - November 27, 2015 - A new product is under development and close to release, the Open Road Rally Computer.  This app is designed for crews entering events such as:

    Silver State Classic Challenge, Nevada

    Nevada Open Road Challenge, Nevada

    Big Bend Open Road Race - Texas

    Sand Hills Open Road Challenge, Nebraska

This app allows the crew to enter the target time and speed and calculates the target elapsed time.  When started the app displays a moving average speed, a speedometer and the amount of time and distance left in the leg.  The last 30 seconds are counted down for the navigator.  A set of graphic bars show the driver how far ahead or behind they are.  A separate driver's display with the moving average speed and ahead/behind graphics is planned.

News - December 21, 2013 - Need more accuracy in mileage measurement?  Check out external GPS receivers such as the Garmin GLO or Dual XGPS160.  They work fine with the Richta Rally Odometer and Rally Computer apps.

News - December 7, 2013 - Apple version with support for iOS 7 now available in the App Store.

News- January 25, 2013 - Draft version of Rally Computer documentation added to Documentation page.    

                                        - Checkpoint Clock Documentation updated.

                                        - Checkpoint Clock 2.11 released.  TOD Adjust beeps every second.  24 hour TOD option added.

News - December 28, 2012 - Checkpoint Clock (Android) Version 2.09 released in Google Play.  Adds several new functions:

    - Ability to annotate checkpoint log entry.

    - Ability to pre-enter car numbers and descriptions.

    - Ability to selection car number and description from a list while annotating log.

    - Ability to email checkpoint log file to scorer.

    - Speaks in time.

News - December 24, 2012 - Apple version 2.9 or Richta and Richta-Lite released in Apple Store - correct bug with iPhone5.

News - December 12, 2012 - Apple version 2.8 of Richta-Lite and Full were released in the Apple Store.  

Changes fixes  include:

    Support for iOS 6 and iPad Mini.

    Fixed lost cranking value and adjusting minutes in New Leg.

    Fixed rounding error in perfect time displas.

    Fixed current CAST lost after New Leg.

News - August 10, 2012 - Apple version of the Checkpoint Clock is now available for $0.99 from the Apple App store.  Demonstration movie available on this web site under Downloads.

News - July 23, 2012 - Rally Odometer Updated, Rally Odometer Evaluation Version Updated.  See documentation for details.

                                    Documentation for Rally Odometer and Checkpoint Clock released.  See Documentation and Contact Us page.

News - June 13, 2012 - Richta Rally Computer released today (Google Play).

News - June 13, 2012 - Rally Odometer / Clock released to Google Play today.  $10 for full product, free evaluation copy available, limited to 20 miles.

News - 4/16/2012 - Price of full version reduced to $10.

News 2/8/2012 - The Apple version released today now works on iOS 5. 

News 1/6/2012 - Richta Rally products are now available through the Amazon app market.

News:  7/8/2011 - An evaluation version of the full function Richta Rally Calculator is now available in the Android Market.

                            FREE.  Limited to 10 miles/kilometers on the trip odometer.

News:  7/6/2011 - An Android checkpoint clock was released to the Market today.


The Richta Rally Calculator is a software program which is intended to perform the calculations necessary for time-speed-distance road rallies, such as those sanctioned by the Sports Car Club of America (SCCA – www.scca.org).  It runs on a hand held personal digital assistant (PDA), smart phones or tablet hardware using the Palm OS operating system,  and Android, or Apple mobile devices (iPod, iPhone, iPad).

Richta History and Design Philosophy

Richta was designed and written by a TSD navigator with experience in competing in over 50 events.  The author previously used a Curta mechanical calculator to perform the rally calculations, but the limitations of that device spawned the realization that the functions performed by the Curta could be duplicated and the navigator’s job made easier through the use of current computer technology.

The operating principles and application of the Curta to TSD rally are well documented.  A good description of these techniques is available from Rally Racing News (http://www.rallyracingnews.com/manuals/curtaman.html).

Throughout the 2004 and early 2005 rally season several short comings of the Curta became apparent to the author.  First, speed changes on the Curta can not be executed rapidly.  Changing average speed on the Curta requires setting 6 small lugs on the side of the device to the minutes per mile factor (the amount of time it takes to traverse one mile at the desired average speed.  The factors are typically determined prior to the rally and copied to the route instruction before the event or during the odometer calibration run.  Entry and verification of these factors (small numbers entered while bouncing down the road) is time consuming and error prone.  It can be very difficult when several route instructions involving speed changes are to be executed in short order.  The navigators can find themselves concentrating on the route instructions (as they should) and entering a checkpoint without a precise calculation as to whether they are early or late.

A second issue arises after a calculation is performed and it must be determined whether the rally team is early or late.  Performing rally calculations with a Curta is very accurate.  Accuracy to within .01 minute or better is possible when using an accurate odometer that reports mileage to the .01 mile.  The Curta output, the calculated time of day at which the rally team should arrive at the indicated mileage, must be manually compared to the time of day clock.  The navigator must concentrate to determine whether the team is .01 minute early or .01 minute late and this operation can be mentally exhausting when performed five to ten times per mile over the course of a 150 mile event.

The Richta Rally Calculator was designed and written to overcome these shortcomings of the Curta calculator.

About the Name

The name Richta (pronounced rik’-ta) is a play on words, combining the designer/author’s first name (Rich) with name of the mechanical device the software replaces (the Curta calculator).  The original Curta calculators were designed by Curt Herzstark and manufactured from 1946 through about 1966.