I recently added a new piece of rally navigation equipment to my toolbox of equipment that might be needed in a car rally – a Timewise 825 speedometer. These calibratable speedometers are required for good scores in time-speed rallies. In a time-speed rally competitors are instructed to drive from one place to another at a given speed, but without the use of an odometer of any kind, cars are timed to the second, and all controls are hidden. So you have to be on time, all the time. So if you instructed to drive 42 miles per hour, then you must drive 42 miles per hour – not 42.5 miles per hour. Standard automotive speedometers are generally not accurate or precise enough to post scores near the front of the field.
Timewise 825 Speedometer
The Timewise 825 speedometer dial diameter is four inches. The unit uses all 360 degrees of the dial for the speed scale. This results in a space of approximately 0.25 inches (6 mm) between each single mile per hour indicator mark. This size makes it relatively easy to follow a given speed. While I keep mentioning miles per hour, the speedometer can also be calibrated to kilometers per hour.
The maximum value on the Timewise 825 dial is 50 miles per hour, but there is no limit to the rotation of the dial. The Timewise 825 will continue to rotate past 50 miles per hour and the unit is accurate up to 150 miles per hour. Of course this will require that the driver and/or the navigator visually knows by their seat-of-the-pants the difference between 35 mph, 85 mph, and 135 mph, for example.
The major time-speed rally in the USA is the Great Race, which is restricted to cars built no later than 1972. This year the Great Race will start Ogunquit, Maine on June 21 and end some 2,100 miles and 9 days later in The Villages in Florida. I won’t be competing, but I plan on going up for the start and probably check in again at the end of the first day in Lowell, Massachusetts – not too far from my house in Franklin, Massachusetts.
The Timewise 825 Is A Substantial Piece Of Equipment
The speedometer comes in a metal enclosure and it weighs a little more than I anticipated. This suggests that the unit uses robust materials of construction. The depth of the unit is 3 1/2 inches.
View Of The Back Of The Timewise 825
The picture above shows the back of the Timewise 825. The red and black wires are the power supply wires. The female jack end is for the connection from wheel sensor to the Timewise 825. The white tag with the number “480” is the serial number for this unit and would be used by Timewise as a reference if the unit was to require repairs in the future. The four openings across the bottom of the back of the Timewise 825 are the dials that are used to input the four-digit speedometer calibration factor.
Calibration Number Dials
The four-digit calibration factor is the distance, in inches, traveled over 10 pulses from the transducer. The calibration factor has a resolution to 1/10 of an inch. For example, if the car travels 531.4 inches over 10 pulses from the wheel sensor then the calibration factor is 5314.
If you look carefully into the four holes on the back of the Timewise 825, you will see small digits 0 – 9 on each one. Within the circle of the digits, there is a small indicator arrow that can be rotated with a small flat-blade screw driver to the desired digit value.
Timewise 825 User’s Manual
The Timewise 825 comes with a good User’s Manual which provides a great deal of informtion on how to install and use the unit.
My Timewise 825 was provided with a calibration label which shows the test results from the testing that Timewise did on my unit before it was shipped to me. This calibration label is shown below. The label shows that if the speedometer speeds are followed perfectly, then the average error would only be 0.024 seconds per hour!
Timewise 825 Accuracy Test
I bought this new Timewise 825 because it is very difficult to locate a used unit that is for sale. I wanted to have the Timewise 825 in my rally navigation tool box in case an opportunity should arise where a driver is interested in entering his car in a time-speed rally, such as the Great Race, and is looking for a rally navigator who also can help set the car up to be competitive.
For more information on the Great Race check out their website at www.greatrace.com
Also, I will be roaming around Ogunquit, ME and Lowell, MA on June 21, 2014 looking at the competitors’ cars at the Great Race. If you happen to see me, please introduce yourself, I always like to talk to car people.