John's Crawler Drone Build Thread

Welcome to my build thread.  This is my first attempt at building a ardurover based on APM 2.5.  The RC platform I am building on is an Axial SCX10 rc crawler (2012 Jeep Rubicon).  The end goal I am aiming for is large obstacle avoidance.  Where this drone can determine if it’s possible to crawl over an object, or have to move around (such as when it cannot get enough traction to climb over an object).  I am to understand that for advanced obstacle avoidance and drone orientation to determine if a change of route is required will require the use of something like Raspberry Pi.  I own a new Raspberry Pi which I am not using, but would be glad to try in the future.  The other thing I am trying to accomplish is keeping everything under the body.  This requirement may push me to bump up to quarter scale vehicle.  Keeping everything under the body will provide a larger possibility of keeping things protected in case of rollover.


Parts List
Axial SCX10 Jeep Rubicon
Pro-Line Cherokee Body
Spectrum DX5e 5 ch w/momentary switch
Spectrum 6 ch receiver
APM 2.5 w/Telemetry (915Mhz) & Power Module
5.8g 200mw FPV Wireless AV Tx & Rx
1/3-inch SONY CCD Video Camera (NTSC)
NiCad 3000 mAh battery
Li-Ion 1100 mAh battery


I have made use of the crawler as it is for the last month, and see that some things need to be modified.  I am strongly considering some changes to the suspension and drive train to improve the crawler’s ability to climb obstacle.  This includes wider axles from an Axial Wrath.  Longer suspension links to stretch the wheel base.  Longer shocks to lift the crawler.  Slightly larger tires to lift the axles further off the ground.  And rotating the axles to lift the pinion to point more towards the t-case to minimize drive shaft joint angles.


Currently, the motor and battery system I have now allows for a bit over 2 hrs of run time.  On this note, the final thing which needs to be looked at is adding a second motor and a better battery solution to ensure the added weight doesn’t impact performance an drive time in a negative manor.


Thanks for reading,

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  • Interesting, I tested the ability to accurately locate the HOME WP.  This morning I could not get a small white ring around the HOME WP.  The white ring is currently taking up my whole yard.  I am wandering when the Sat's will be over the sky in my region.  Is there a way to find that information?  I will be checking again this afternoon to see if I can get a smaller ring like I did yesterday.



  • 3692723753?profile=original

    Which is front an back?  I am assuming the bottom of this ICON is the back.  Can anyone confirm?



  • So I found something interesting yesterday afternoon.  I tested outside an noticed that the HOME WP was in my neighbor's yard, but had a small white ring around it.  Watching it, I noticed the rover moving around.  I am guessing trying to align the HOME WP with the current position.  I then moved the HOME WP to the current location an wrote that to the APM an within 1 min, the rover migrated to the HOME WP an stayed put.


    I am going to try this a few times an see how it improves accuracy.



  • I have taken a screen shot of Mission Planner to show the issue.


    Note the Green WP icon for HOME.  Also take note of the Purple DOT I have added to show where I turned on my APM, which is inside my house.


    Take note of the 3 Teal dots I added.  That is how far Mission Planner showed my rover moving around while it was only powered by the USB cable in my room at the Purple DOT.  That trip took 20 min of being plugged in to my computer via USB sitting in my room.


    If that flat edge of the Rover ICON is the rear of the rover, then my rover front is facing along the same direction of the road to the left of the picture with the front facing down.  If the flat edge is the front, then its off, but not as bad.




  • @TC,

    Yeah, I have the MediaTek GPS unit.  I will be taking a couple of pictures in a min to show my setup further.  I do have the Aluminum plate between my ESC, Motor, Battery, an the rest of the electronics including the APM.  When talking about a ground plane, are you suggesting I ground my aluminum plate to the NEG of my electronics battery?


    I am also looking at moving things around to see how I can change the behavior.


    What's really messed up is, with the rover in my Room at the far corner of my house, the HOME WP is located at my neighbors yard.  Then with the rover sitting still, Mission Planner shows it moving around across 3 neighbors yards.  Each of which are 1/2 an acre


    If this is due to the GPS, then the MediaTek is not even worth buying.  When the HOME WP is in the middle of my house, the white ring which shows its perimeter (I assume) takes up my entire yard.  In my opinion this is not very accurate.  Not when were suppose to be 1 meter (3.2ft).


    Pictures to come soon.



  • @Mike & @TC,

    Does the GPS chip have an orientation which it needs to be installed by?  In short, is it like the APM which has a front?



  • @Mike an @TC,

    I checked my APM via usb cable with Mission Planner an got the following information...

    GPS: 3D Fix

    HDOP 2.2

    Sats 6

    According to the map, my Rover is located in the back far corner of the house when its located at the front on the opposite end.  Further more, the track shows it to be moving all over the house which is a 1600 sqft area.


    At this time, there is nothing further I can do about the GPS an compass.  I will try moving things around a bit more, but until I am employed again this part of the project will receive no further attention.  What I am going to focus an push on is the ability to set the mode via mission planner.  I looks like I bought the wrong GPS unit trying to save $50.



  • So I have had no luck with GPS accuracy.  An I am seeing as much as a 40 yrd deviation.  Went to a friends house an turned on the power an Mission Planner showed my home/launch site as down at the end of the street.  Meanwhile, I appear to be having issues with my electronics battery longevity.  My lack of knowing when its below threshold seems to be the cause of its short life.


    The above combined with the need for higher voltage to my FPV transmitter has pushed me to consider a 3S li-po for the electronics.  Meanwhile, I will leave the 7.2v Ni-Cad (3000mah) in place for the drive an servo use.  That seems to be working great.


    Need less to say, next on my list of things to do is upgrade the electronics battery an purchase a charger.


    The other thing I need to see is the successful ability to set the APM's mode via Mission Planner.  Currently I just change the 2 position toggle from Manual/Leaning to Manual/Auto.  I have tried setting it to Manual/Manual an just using Mission Planner to set Learning an Auto, but that has not been successful.


    John Moore

  • @Bot_Thoughts,

    Thanks for the reference material.  If I read your page correctly, it look as if mag interference from a 27T 540 Brushed motor is minimal.  I don't have the ability to test, but I would be curious if a copper mesh material such as that used on a Faraday Cage adhered to the bottom of the aluminum base an grounded to the neg of the main battery would help any.


    Would I have less interference from a Brushless motor?  Apparently, the stock ESC is a Li-Po ready unit.  Upgrading to Li-Po an brushless may cost less than originally thought.



  • If a near-by motor drawing up to 20A has very little or no affect on a compass, then why does re-bar underground and electrical wiring have an affect?  (or so I'm told).

    Alan KM6VV

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