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Thread: Speedometer

  1. #1
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    Question Speedometer

    Is the installed speedometer accurate at all? It's not the GPS one it goes by rpm at the flywheel but it doesn't know what gear it's in so it says I'm doing 40mph in first gear at 35000 rpm and when it shifts to second the speedometer reading drops with the tachometer reading, so I'm guessing the speedo is calibrated to be accurate in second gear only? Does anyone have the GPS one and would you recommend it, does it add a lot of weight? And what is the voltage meter on the app there are bars for the transmitter and the receiver so what is volts measuring?

  2. #2
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    no. not even close lol or my stock 3.3 has hit over 80mph.

  3. #3
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    Wow that's interesting! Mine just read 276mph so that's obviously not accurate

  4. #4
    RC Champion olds97_lss's Avatar
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    I'm not sure how traxxas's works, but when I was fussing with telemetry on my rig at the time with a spektrum device, I'm pretty sure I had to put a magnet or something on the center shaft and the sensor would install by that. Then the instructions had something in it like how many revolutions it did for a 12" movement of the truck. Then regardless of the gear the truck was in, it was always using the center shaft which doesn't change ratio. There was another sensor/magnet or shiny thing for the flywheel for RPM's.
    Expert rigging at it's best!

  5. #5
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    Traxxas telemetry for speed is supposed to be gps based.
    Man i need more than 50 characters.

  6. #6
    Marshal ksb51rl's Avatar
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    Quote Originally Posted by Apexracing View Post
    Traxxas telemetry for speed is supposed to be gps based.
    Half correct.
    There is also an RPM sensor by which speed can be calculated.
    RPM stands for Revolutions Per Minute. To collect this critical data, a "trigger magnet" is installed in the spur gear of electric models, or the flywheel of nitro vehicles. To offset the weight of the magnet, additional material is molded or cast into the opposite side of the spur gear or flywheel. To read the magnet, a hall effect sensor is installed in the gear cover (electric models) or installed on a support arm (nitro models). Each time the trigger magnet passes the RPM sensor, a revolution is counted. Revolutions per minute are displayed on the tachometer of the Traxxas Link dashboard. RPM is also the key to determining your model's speed. When you select your model in the Traxxas Link application, the app uses your model's transmission ratio and tire circumference to calculate its speed based on RPM. Speed is displayed on the Traxxas Link App's dashboard speedometer.
    Alt-248 on the number pad =

  7. #7
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    Thank you sir. That is cool, saves me the money of purchasing the gps sensor. I'm not worried about land speed records. But having all of the data on the dash board screen working would be cool.
    Man i need more than 50 characters.

  8. #8
    Marshal ksb51rl's Avatar
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    Just so long as you realize that the accuracy will be severely affected by wheel spin, tire ballooning, and the inability to enter custom tire diameters (unless that has changed recently). GPS should be simpler since it removes many of the variables, but it is more expensive.
    Alt-248 on the number pad =

  9. #9
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    Oh i know and thats fine with me. They do allow you to select several traxxas tire combos from the app. But nothing custom.
    Man i need more than 50 characters.

  10. #10
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    Yeah it seems to be accurate as long as your not spinning your wheels or in the air, but mine is only accurate in second gear, does anyone know if it's supposed to be like that r should it k own what gear your in?
    Last edited by Double G; 11-08-2016 at 09:57 AM. Reason: duplicate

  11. #11
    Marshal Double G's Avatar
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    Again, the speed is a mathmatical calculation based upon RPMs of the engine so the telemetry does not know if it is in first or second gear or even sitting at idle. Now if there was a sensor on the output shaft it would be much easier to dial in the actual speed.
    The Super Derecho

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