Mars Rover 6WD

I started this design to become more acquainted with industrial design using Shapr3D on iPad with an Apple pencil, close up DSLR photography, fine tuning Bibo 2 printer configuration, Arduino boards, Arduino CC and C code. There will be a supplied Shapr3D file posted. Shapr3D is free for various platforms. This is a variation of RC Rocker-bogie chassis (Mini martian rover) by Tadziurski posted April 20, 2019 on Thingiverse.com.

1) 1 X Taranis X9D

2) 1X FrSky X8R

3) 1 X Arduino Mega 2560

4) 2 X BTS7960B Motor Drivers

5) 1 X Lip-Po Battery 1300mah 2S1P

6) 1X Li-Po Battery 400mah 2S1P

7) 6 X TT Geared Motor w/ Wheels

8) Wire Ribbon Cable

9) Power Wire-20 Gauge

10) Super Flexible 12 AWG Wire Red/Black

11) 2 X 10-12 AWG Crimp Connectors

12) 1 X Male Header Pin Strip

13) 4 X RC Tie Rod Ends

14) 1 X XT60 Male Power Connector

15) 2 X M5x25mm Flathead Bolts

16) 2 X M5 Nuts

17) 1 X M4x25mm Flathead Bolt

18) 1 X M4 Nut

19) 1 X M4 Nylon Locking Nut

20) 8 X M3x50mm Button Head Bolts

21) 8 X M3x40mm Socket Head Bolts

22) 4 X M3x35mm Button Head Bolts

23) 8 X M3x30mm Button Head Bolts

24) 2 X M3x20mm Flathead Bolts

25) 4 X M3x20mm Socket Head Bolts

26) 2 X M3x14mm Button Head Bolts

27) 2 X M3x12mm Socket Head Bolts

28) 2 X M3 Nuts

29) 34 X M3 Nylon Locking Nuts

30) 5 X M2.5x14mm Socket Cap Bolts

31) 5 X M2.5 Locking Nylon Nuts

32) RC LED Light Strip (optional)

33) CA Glue

34) Isopropyl Alcohol

35) Acetone (optional)

36) Liquid Flux

37) Red Thread Locker

38) Cotton Swabs

39) Zip Ties

40) Rosin Cored Wire Solder

Parts to be printed can be found here on www.thingiverse.com.

Print out rover stand, main deck, deck 2, top cover (will require support), 2 x Rockers (one mirrored, use slicing program), 2 x bogies, battery holder-large, battery holder-small, antenna mast, suspension cross bar and light bar mount.

Clean up bolt holes using corresponding drill bit size and precision hand drill for easier assembly. I don’t recommend using a drill or power driver as the speed of bit tends to melt the plastic instead of cutting away the material.

Lightly brush printed parts with acetone to achieve glossy appearance (optional).

Install left and right rocker axles to Main Deck using 2 X M5x25mm Flathead Bolts and 2 X M5 nuts using thread-locker to secure nut.

Install Suspension Cross Bar Axle to front of MainDeck using 1 X M4x25mm Flathead Bolt, 1 X M4 Nut and thread-locker.

Mount Arduino Mega 2560 to main deck using 5 X M2.5x14mm Socket Cap Bolts and 5 X M2.5 locking nylon nuts. Skip the bottom left hole in photo. It’s slightly out of line.

Assemble large and small battery holders by by using CA Glue to fasten top plates. Glue battery holders in place using CA Glue as shown in photo. Use spring clamps to hold till glue sets for secure hold.

Mount suspension cross bar to front of main deck using 1 X M4 nylon locking nut as shown in photo.

This step requires building a data wiring ribbons to:

1) Connect 2 X 4-wire ribbons from Arduino Board to control the left and right motor drivers (BTS7960)s.

2) Connect the Arduino to the FrSky RC receiver.

I don’t recommend using breadboard jumper cables “as is” for these connections as there is some wiggle factor between the male jumper pin and the Arduino female header row. This can cause erratic motor control and function. The female end of jumper wire connector, however, does fit snugly on the BTS7960 header pins.

Steps for soldering ribbon to header pins:

1) Take header strip and cut into 2 x 2-pin, 1 x 6-pin & 1 x 8-pin strips. Clean pins with alcohol and cotton swab.

2) Mount strips onto electronics breadboard to steady, by inserting long pins into board. Clean the short pins with alcohol.

3) Snip male end(s) off ribbon wire and strip off 1/4” of insulation and twist striped wire.

4) Place micro drop of flux onto header pin(s) and wire(s).

5) Melt small amount of solder on soldering iron tip and tin each wire(s) and header pin(s).

6) Cut each piece of 2 X 45mm x 2.5mm(O.D.) heat shrink tubing into four equal pieces. Slide a piece of heat shrink tubing onto first wire to soldered. Make sure there is approx. 1” between stripped end of wire and start of shrink tubing, or the tubing will shrink before have a chance to slide over header pin.

7) Solder tinned wire end to header pin and let cool.

8) Slide heat shrink tubing over header pin/wire connection and contract shrink tubing with hot gun, or gently use lighter.

9) Repeat for remaining connections to create wiring harness as shown in photo.

10) Clean flux residue off of header pins and wires with alcohol and toothbrush.

11) Soldering Header Pins Video.

Connect wiring harness to Arduino board as shown in photo. PIN numbers are shown in step 6 for further clarity.

Mount 2 X motor drivers on Deck 2 as shown in photo using 8 X M3 x 40mm Socket Cap Bolts & 8 X M3 Nylon Lock Nuts. If slightly out of alignment and prevents install of all bolts, re-drill support posts with 3.2mm drill bit.

This step will split power from the 1300mah Li-Po battery to both motor drivers. Cut 12AWG wire into 2 X 10” pieces and strip 1/2” off of each end. Using a set of crimpers and 2 X 10-12 AWG yellow crimp connector assemble the power harness as shown in photo.

Mount XT60 power connector to bottom of deck 2 using 2 zip ties as shown in photo.

Feed wired from Arduino board up through center slot of Deck 2 and then mount Deck 2 to Main Deck using 4 X M3x50mm button-head bolts and 4 X M3 locking nylon nuts as shown in photo.

Connect Arduino control wires to motor drivers using the photo from Step 6 for connections reference. Pin assignments are also in the .ino file.

Trim and strip power wires to fit and connect to motor drivers as show in photos. Make sure there is no exposed copper and wire insulation fits snugly against light green power connector on motor driver. Secure wires together with large pieces of shrink tubing. Zip tie cables to Deck 2 to prevent wires wiggling and coming loose at battery power connector on motor driver. See photos.

Assemble rocker-bogie arms as shown in photos using 2 X M3x20mm Flathead Bolts, 2 X M3 Nuts & 2 X M3 Nylon Locking Nuts. Remember to use thread-locker on axle nuts as in Step 2. Tighten M3 Nylon Nuts so Bogie Arm doesn’t wobble on Rocker Arm, but loose enough to move freely on axle.

In this step you will need to solder 6-pairs of 20AWG 10” power leads to the motor terminals on all six TT geared motors. When mounted on the rocker-bogie assemblies the terminals should be facing out, away from the rover. Latticing indentations should be facing out as well with the bogie arms at rear of rover. Since the polarity of the terminals are not consistent you will need to determine the + and - terminals. Looking at the motor with the terminals facing you will need to determine the proper polarity of connections so that you have three motors that rotate CCW, left side of rover, and three that rotate CW for the right side of rover. Use the small 400mah LiPo battery and the male JST pigtail to determine motor direction. Using the same soldering technique in Step 6 video solder 10” power leads to each motor.

Mount motors to rocker-bogie assemblies using 4 X M3x35mm button-head bolts, 8 X M3x30mm button head bolts and 12 X M3 nylon locking nuts as shown in photo. Strip 1/4” of insulation off the end of each wire and then join like positive and negative leads together using heat shrink tubing or electric tape. Twist the striped copper wires together for future connection to the the BTS7960 motor drivers.

Using CA glue mount antenna mast to rear of top cover. Using the bolts that came with light bar, mount light bar to light bar mount. Feed light bar wire through slotted hole at front of top cover and the up through hole at rear of top cover. Feed wires from Arduino pins 7, 8 & GND through rear hole on top cover. Photo shows an additional 3-wire servo connector for optional RGD LED strip. Mount light bar mount and top cover to deck deck 2 using 4 X M3x50mm button-head bolts and 4 X M3 nylon locking nuts.

Mount RC receiver to rear of top cover using 1 X 1x1-1/2” piece of hook & loop adhesive tape. Mount antennas to each side of antenna mast using two small drops of hot glue for each antenna. Connect the following Arduino pin wires: GND, 7 & 8 to RC receiver. Connect light bar to channel 5. Connect RGB LED light strip to channel 6 (optional). Mount optional RGB LED strip to underside of main deck using hot glue as shown in photo.

Using soldering and heat shrink tubing techniques, solder all positive leads and all the negative leads together using 1 X JST male power connector, 1 X JST female power connector & 1 X 5.5mm female barrel connector. The harness in photo shows one extra pair of JST connectors between the shrink tubing and barrel connector. This connection is not necessary for this project.

Place rover on stand And mount rocker-bogie assemblies to main deck using 2 X M5 nylon locking nuts. Tighten bolts tight enough to remove wobble, but loose enough to move freely on axle.

Using a pair of vice grips, a rotary tool with cutting disk and eye protection cut the socket heads off of 2 X M3 x 12mm socket head bolts. Cut enough off of the ends of tie Rod connectors so that when put end to end they measure 36mm as shown in photo. Connect tie rod connectors end to end by screwing newly created threaded Rod into center of tie Rod end. Flat surface of brass link rod ball joints must be rotated 90 degrees away from each other.

Bolt a suspension tie rod assembly to each end of suspension cross bar using 2 X M3x14mm button-head bolt and 2 X M3 nylon locking nut. Bolt the other ends of tie rod assemblies to front of rocker arms using 2 X M3x20mm socket cap bolts and 2 X M3 nylon locking nuts.

1) Download Mars_Rover_Mega_Working.ino

2) Install Arduino Create Agent.

3) Go to https://www.arduino.cc/ and create account.

4) Login and open Web Editor by selecting the 3x3 dots button in upper right hand corner of screen.

5) Select New Sketch button.

6) Rename new sketch to "Mars Rover Mega Working" by selecting triangle on sketch name.

7) Select triangle again and select Import File Into Sketch.

8) Navigate to the Mars Rover Mega Working.ino you downloaded earlier and select Open.

9) Verify and Save new sketch by selecting the "check mark" button.

10) Use the select Board and Port drop down menu to select Arduino Mega 2560 with proper com port (port number varies from computer to computer depending on computer config).

11) Upload and Save by selecting the "right arrow" button.

12) Unplug USB when complete.

Mars_Rover_Mega_Radio_Test.ino can be loaded with USB cable to load only enough of the code to test/verify radio communication by o showing results on the serial monitor within Arduino Web Editor. It will not allow motor function.

Insert small 400mah battery into small battery holder and power up receiver by connecting small battery to receiver using power wire harness. Connect battery to receiver pins as shown in photo of step 18. Bind Taranis radio and receiver as outlined in X8R manual. If not using Taranis Tx/Rx pair, refer to your equipment manufacturer for binding instructions.

Place rover on stand. Connect small battery to receiver using JST connector. Connect the Arduino board using the barrel connector on harness. Power up transmitter and place left joystick in middle position. The left joystick controls the forward and backward movement. The right joystick will rotate the rover CW or CCW. Note: Left joystick must be in center position before you can rotate the river with right joystick. Insert large battery into battery holder. Connect large battery to motor drivers using XT60 connector. Verify correct motor operation and direction on stand before placing on open surface. Have fun!