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  1. #1
    RC Racer
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    Traxxas GPS specs inspected

    Before I purchased the GPS module for my Bandit I called Traxxas and asked for specs. The person I spoke with advised those specs aren't published to his knowledge, & he didn't know what they were.

    To make a long story short the Traxxas app lets you record the sensors so that's what I did. The Traxxas link app displays mph to the precision of 1mph, however, looking at the log it would appear the GPS operates natively in kph and converts to mph. It also seems the MPH reading gets rounded up. At what point the rounding happens I've not discovered yet.

    I was curious what the update rate was but the guy I spoke with didn't know. Looking at the log the GPS can sample as quickly as 10Hz, or 10 times per second, which is the same rate as the other GPS I have, so that's good. And the speed matches between the two GPS devices other than the Traxxas GPS rounding up the MPH. So when the Traxxas app said 53mph the other day my other GPS read 52mph, the difference is likely rounding, so I'm happy with the accuracy.

    Excerpt from the log.



    Riddle solved.
    Last edited by danner; 05-23-2019 at 06:10 PM.

  2. #2
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    Just ran the car out front and crashed into a puddle. The front bumper made a giant splash of water, LOL. Now my tires have to dry out.

    Anyway, before I crashed into the puddle, as I was slowing down, the Traxxas GPS logged 85kph, or 52.817mph, which was rounded up to 53mph on the Traxxas app speedo. My other GPS logged 52mph.

  3. #3
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    This little car still boogies pretty good with the 76/38 gears. I couldn't find a place to log the distance traveled on the Traxxas app. Check out the voltage drop in the mid-range where the acceleration is quickest. Neat!



  4. #4
    RC Racer
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    Good stuff. I am planning to grab the telem pack soon for at least one of my cars.

    That type of sag on pulse/acceleration is to be expected but I came back to the RC world from the nicotine vape hobby world pushing 100+ watts thru a 0.1 - 0.2 ohm coll with 2 or 3 li-ion 18650/21700 for 5 to 10 seconds.

  5. #5
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    Have had the telemetry for a while, temp, volt, & rpm, just didn't have the GPS because they weren't selling them when I purchased my Bandit. I like it now because I know instantly whether I achieved the attempted speed.

    Discovered the left rear suspension inner bolt backed itself out again. Wonder if that caused it to pull? Can't wait for the pin kit to arrive.

    Don't smoke, so not familiar with vape stuff, but I do do LED flashlights, so I'm familiar with the 18650.

  6. #6
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    Got bored. Ran some numbers through a spreadsheet. 0mph to 52.817mph and back to 0mph in 9.8 seconds calculates to a total distance traveled of 688ft, 0.35G peak acceleration and 1.2G peak stopping force. I did quickly come to a stop in a puddle on the side of the road.

    Required 522watts to accelerate 5lbs to 52.817mph in 6.9sec, which works out to a peak of 0.7HP, & 68.8amps, which is close to the claimed 65A continuous rating of the ESC.



    I assume the math is correct, it's the first time doing it in a spreadsheet since I didn't previously have access to accurate mph data, so it could be off.

  7. #7
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    Can you estimate your scale 1/4 mile time? I was at the shop yesterday and the guy that helps me there told me his 4x4 slash drag build he has running on 6s got up to 75mph in 240ft the other day. Not sure what type of system he uses for tracking that info.

  8. #8
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    I believe it. Some of those speed run videos on youtube have onboard GPS and it displays the g-force under acceleration, & they accelerate really quickly.

    As for the scale 1/4mi time to 132ft, I rolled into the throttle for about 30ft before beginning to accelerate to full throttle, so not that quick. If I did the math correctly, 132ft was reached between 3.7-3.8sec.

    0-75mph in 240ft equals acceleration of 1.6G & should take ~2.2sec, assuming my math is correct. That's hauling the mail by any standard.
    Last edited by danner; 05-24-2019 at 11:12 AM.

  9. #9
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    Yeah, top speed run throttling technique is way different than the guys with their drag builds meant for quick acceleration runs so that obv isn't a good indicator if what your car is capable of in a scale 1/4 if tuned (clutch, gearing, etc) for a hard launch off the line. I have come to know my rustler vxl clutch very well since getting it a month or two ago. I lost count of many times I had to adjust/replace it before I finally found a happy setting I can live with for both street and dirt. Knock on wood, I haven't had to adjust or replace it in a solid week or two now LOL.

  10. #10
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    I tightened my slipper down to between 1/2-3/4 turn out. I believe it's at 3/4 turn right now, was experimenting with tightening it more from one full turn out.

  11. #11
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    I burnt up my stock one and did some research and saw someone that suggested 1/4 turn back, that was a mistake. I have mine set right about 1/2 turn back and it seems to work well for me on dirt or grass with my trenchers and on road with the road rage or banditos. Depending on the surface and tire I can still play with wheelies if the bar is up and with the bar down and proper throttle control it seems to slip or spin the tires if needed just the right amount so far. No idea how long a clutch is supposed to last, or how long this one will last, but I bought 3 spares to be safe...

  12. #12
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    Well, I got my 70mph, but for whatever reason the Traxxas GPS wasn't receiving the sats. My other GPS did capture the speed though.

    Only had the small 3s 4500mAh, because it has been raining and there are puddles everywhere, and I didn't want to get my other set of tires waterlogged in case I drove into a big puddle again. 3s is harder to control than the 2s, but that goes without saying.

    Once the tires hook up it goes pretty straight. I need to get used to the tires losing traction with 3s, things happen really quickly. Was not a full pull either so there is some left in there. Ran out of room in front of my house real fast at that speed. Glad it's out of the way finally.

    Did two pulls trying to get the feel of when the tires would break traction & got 70mph a second time, Traxxas GPS still refused to get a lock. I rebooted everything & the GPS started working again, but by then the voltage had dropped to ~12.0VDC, so I stopped for now, & managed not to drive through a puddle this time.


  13. #13
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    I believe I may have pulled the wire out slightly to the expander module. The voltage display started telling me the batt was 0v then 12.1v & when I opened the expander box the wire that goes from there to the ESC was barely plugged in. That was likely it.

  14. #14
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    After upgrading to the 2.0 telemetry expander I was having intermittent communications with the GPS and sensors. Traxxas support advised I replace the cable from the telemetry expander to the radio. I just did that and everything appears to be normal so far on this first battery running the car up and down the street. Hopefully that fixes it.
    Last edited by danner; 06-06-2019 at 03:34 PM.

  15. #15
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    Quote Originally Posted by fozzy71 View Post
    Can you estimate your scale 1/4 mile time? I was at the shop yesterday and the guy that helps me there told me his 4x4 slash drag build he has running on 6s got up to 75mph in 240ft the other day. Not sure what type of system he uses for tracking that info.
    I just finished installing Mod1 gears 36/18, and was testing out the slipper clutch tightness. After running up and down the street a few times to get some temperature in to the slicks, which worked great BTW, I thought about your inquiry about scale 1/4mi times. After the slicks were warm, with 2s at least, I gave it full throttle from a standing start, could hear the slipper give a little, and I got this result. Quite happy it launched perfectly straight on the blacktop in my driveway. Probably would just spin out on 3s if I tried that.

    Anyway, some acceleration stats for you. Didn't quite run the entire 132ft, my driveway isn't quite that long before I have to come to a screeching halt. Everybody is getting out of work so the street is too busy to test on at the moment.

    0-34.797mph in 2.2 seconds took approx 112.3ft. Would be curious to see what it would do in 132ft.





    Last edited by danner; 06-06-2019 at 04:06 PM. Reason: legibility

  16. #16
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    Most of my time lately, has been devoted to dialing in the suspension, and only recently had time to address the intermittent communications with the telemetry expander.

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