This is a spherical robot design that I am working on. I intend to use this to create a replica of BB-8 (lots more work to do!). It is about 18" in diameter and very intuitive to control. I have spent about $400 for everything in this instructable. The internal structure and drive system is made from primarily Actobotics parts available through Servo City.
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Step 1: Assemble the Drive System
The next few steps will describe how to assemble the drive system. The drive system uses entirely Actobotics parts (listed later). This motor and gear ratio results in a nice balance of power and speed in the final robot.
Step 2: Prepare the Motors and Connections.
Before mounting the motors, I soldered on a motor backing that allows me to easily connect a male 20 JST connector. I find this useful for using motors in other projects later and making robot modifications and maintenance much easier. I will connect my motor to the ESC (electronic speed control) later using an XT60 connector (many other connectors would work fine), so I soldered the male JST connector to a male XT60 connector.
Pay attention to positive and negative! The Actobotics motors have a white dot on the positive terminal but they can also be wired the opposite way. For this robot, make positive and negative the same for each motor.
You could solder wires directly to the motor and ESC, but connectors really make everything easier for the future.
2x - (JST20M) 20 awg Male JST Connector
2x - (605120) Gearmotor Board D (for 32mm Planetary Gearmotors)
2x - Male XT60 connectors
Step 3: Assemble the Drive System (2X)
The following steps will describe how to make one of the wheel assemblies. You must make 2 of these wheel assemblies. Each is identical.
Parts for ONE wheel assembly
(638284) 612 RPM Heavy Duty Precision Planetary Gearmotor
3x - (535198) .250 inch ID x .500 inch OD Flanged Ball Bearing (Stainless Steel) (These come in 2 packs, you need 3 for each wheel assembly, 6 total)
At least 64x - (632106) .250 in L x 6-32 Zinc-Plated Alloy Steel Socket Head Cap Screws
(585442) 3.00 inch Aluminum Channel
3x - (545360) 90 Degree Quad Hub Mount C
(633104) 1/4 inch Shafting & Tubing Spacers (12 pk)
(634064) 1/4 inch x 1.50 inch D-Shaft
(595630) Drive Wheel Adaptor A
(615242) 16 Tooth, 32 Pitch, 1/4 inch Bore Pinion Gear
(615206) 80T, 32P, 1/2 inch Bore Aluminum Gear
(545548) 1/4 inch Bore Set Screw Hub (0.770 inch)
(6432K12) 1/4 inch Collar
(634078) 1/4 inch x 3.00 inch D-Shaft
(595624) 4.90 inch Robot Wheel (Blue)
(625106) 1/4 inch to 6mm Set Screw Shaft Coupler
Step 4: Mount Gear
Place bore set screw hub into aluminum gear (gear flange side down). Screw the drive wheel adaptor into the gear and hub as pictured using 4 zinc plated screws.
Step 5: Check the Wheel Orientation
The wheels are not symmetrical but can be mounted 2 ways. One side has ridges and a more shallow taper. I put my wheels on with the ridges facing outwards.
Step 6: Mount Wheel
Place the mounted gear into the wheel, then the other part of the wheel adapter into the wheel, and then screw everything together firmly.
Step 7: Attach Motor Mount to Motor
Attach planetary motor mount B to motor. Be sure the mount is oriented such that the screws sink into the mount when tightened.
Step 8: Attached Drive Shaft
Mount the 1.5" long D-shaft onto the motor using the coupling. Be sure the coupling is as far down onto the motor as possible and the D-shaft is pushed in as far as possible (this will result in the correct length later). Obviously be sure to tighten the couplings such that the hex screws screw onto the flat side of the D-shaft. Make sure the hex screws are tight, mine have comes loose. Use locktite if necessary.
Step 9: Mount Motor
Screw the motor onto a 3" piece of aluminum channel as pictured. I used longer screws (1/2") but this is not necessary.
Step 10: Attach Bearing and Joint
Place bearing into the upper hole of the motor assembly with the flange on the outside of the channel. Place the joint against the bearing as pictured and screw onto the channel with 4 screws. This sandwiches the bearing between the channel and the joint holding it in place.
When attaching the joint, screw each screw in loosely first, then tighten each slowly and evenly so the joint is flush with the channel.
Step 11: Attache 2 Joints
Screw in two quad hub mounts with 8 screws as pictured. When attaching these joints, screw each screw in loosely first, then tighten each slowly and evenly. It's much easier to put the screws in this way.
Step 12: Place Bearings in Joints
Slide 2 bearings into place with flange facing outward.
Attach 1/4 in collar to the 3" D shaft leaving exactly a quarter inch sticking out. Add 2 spacers. Slide the shaft through the bearings mounted above the motor.
Step 14: Pinion Gear
Add one spacer to each shaft. Attach pinion gear. Make sure everything is pushed together tightly on the shaft but not tight enough to create friction.
Step 15: Wheel Mounting
Put the wheel assembly on the top shaft. make sure the set screws screw into the flat side of the D shafts
Step 16: Attach to Main Body
Attach whole assembly to end of a 9" piece of channel
Step 17: Set Up Power Distribution
I use a Turnigy 2200mAh 3S 20C Lipo Pack with XT60 connector. I soldered a female XT60 to some standard RC connectors to be attached to the ESCs later. Looks a little sloppy but it works. PAY ATTENTION to positive and negative obviously. You can easily ruin your ESCs or battery by creating a short circuit or connecting things backwards.
Step 18: Attach ESCs
I used a HobbyWing QUICRUN 1060 Brushed ESC (1/10) (one for each motor). Red and black wires connect to positive and negative of battery. Yellow is motor positive, blue motor negative. The signal wires will go to the drive computer later. These come with a switch. I keep the ESC off until everything is hooked up properly. Jumppers should be set to LIPO and F/R. Instructions that come with the ESCs explain how to do this. I stuck my ESCs to the robot with double sided tape (included with ESC) right above the motors.
I used a jig saw to cut a small hole in the channel to fit my XT60 connectors through when attaching the motors.,
Step 19: Reciever, Mixer, and Capacitor
My receiver is a Neewer® Fs-r9b 2.4g 8ch Receiver Rx-9x8c For Turnigy 9x Fs-th9b 9ch Transmitter. Obviously get a receiver compatible with your transmitter. To make all of the controls super easy, I use an IMX-1 invertible RC tank mixer drive computer. Information and user guide HERE. Be sure to do the recommended calibration. I put the drive input in channel 3, steering input in channel 1, and invert in channel 5 (this comes in handy but is not required). This set up allows for intuitive control of the whole robot on the right stick of the transmitter. Channels may vary between RC systems.
Plug the ESC signal wires into the front of the IMX-1 mixer. The white wires (signal) should be facing the inside of the board.
Also pictured is a Novak 5626 Glitch Buster Capacitor. This can plug into any channel and prevent radio glitchs caused by high amp motors being near the receiver. I was having a few glitches here and there. This capacitor makes everything smooth and glitch free.
Step 20: Center Piece
The center of the robot is a 3" piece of aluminum channel attached with (545532) Channel Connector Plate A and four screws. I cut a small corner of the channel out with a jig saw to make room for wires coming out of the battery.
Step 21: Attaching Ballast
The bottom piece of 6" channel is also connected with (545532) Channel Connector Plate A and four screws.
Step 22: The Ballast
I made my ballast using lead wheel weights for balancing car wheels. These conveniently have double sided tape already on them. I used about 1.5-2 lbs of weight to fill up a piece of 6" aluminum channel. Be sure to leave space in the middle for the battery to sit. Be sure to not add too much weight to the sides or bottom or it will hit the sphere after final assembly. I also attached craft foam (like egg carton foam) to the bottom using zip ties. This is optional but helps eliminate wobble from the robot.
Step 23: Careful!
I used 2x - 18 in. Clear Acrylic Globes - with 8 in. Neckless Opening - American 3202-18020-017. These are quit fragile. I used a dremel and cut off wheel most successfully to cut mine but still melted a bit of plastic. These will shatter so be careful.
Step 24: Prep Sphere, Cut Circle, Glue Tabs
You will need 2x - 18 in. Clear Acrylic Globes - with 8 in. Neckless Opening - American 3202-18020-017. Use the opening of one sphere as a stencil to cut a circle out of the other sphere (8"). I used a dremel sanding tool to score the inside of the opening so epoxy will stick better. Cut 8 rectangles out of 1/16" thick balsa wood (can use box cutter/knife). The rectangles are 1" x 1-3/4" each. Using 5 min epoxy, glue the rectangles to the inside of the sphere as shown. the placement of the wood "tabs" allow for the robot to slide in and out of the sphere. I beveled the edges of the tabs so later the wheels can ruin over them more easily.
Step 25: You're Done!
The robot is now complete. See my video for a demo. Be careful taking it in and out of the sphere so you don't break the wooden tabs. I close the "door" of the sphere using duct tape at the moment but I'm working on a latching mechanism.