Another Tiger Tank (RC rev)

Updated tiger model 

to add controls for turret, gun elevation and drive.  

Changes include mounts for motors, servo and electronics.  Changes for simpler stronger suspension and a little longer wheel spacing.  Beefed up idler wheels and sprockets and thinned tracks with bigger guides for needed clearances.  Some minor cosmetic tweaks...  Overall appearance looks the same though.  The hardest part was getting the tracks and sprockets to engage cleanly and reliably.  Overall, the model is somewhat true to the original tiger in that the 12v motors are very torquey and under FULL power pulling hard maneuvers on rough surfaces can self-destruct the drives.  They are capable of breaking the axle and/or snapping the glued motor mounts inside the tank.  (ask me how I know)  On slicker surfaces where it can't hang up no worries.  Turret rotation is not limited, however the servo for the gun is wired and depending on your wire management skills, mine are poor, it will destroy that connection.  

Electronics are a 30pin ESP32 and expansion board, 2 - L298 motor controllers, a LM2596 voltage regulator, 2 - 12v 20mm 100 rpm geared motors, an N20 motor, a SG90 servo, and battery box for 4 18650 batteries.  You could use an 8 pack AA battery holder and in theory eliminate the voltage regulator by taking 5v off of the motor controllers as it would be under 12v versus the 14.8v from the 18650 batteries.

Controls are offered up via a webserver hosted in the ESP32 processor in the tank.  The tank broadcasts a wifi network you connect to and then you can browse to its IP address of 192.168.1.1 or whatever you set it to in the program and then get a web page of buttons to control the tank.

This is a fairly large model with about 350 parts to print and will use more than a kilo of plastic to print. With the batteries and motors and electronics it weighs more than a few pounds.

Parts inventory

Sure I have forgotten something, but will update as needed.

Print

These are not absolutes as I am no print expert but hopefully a few hints to help print.  I printed most at .16mm layers and used supports where necessary in PLA+.  When using support, I set the support overhang angle to 75% which helped stop the slicer from putting support in any 6mm holes that would be hard to clean up and unnecessary.  It tended to put support where absolutely necessary with that setting.  Most parts need only touching build plate support but the turret and front bottom hull definitely need full support.  Using a support roof layer with a gap to print of .3mm helped keep the print clean and make support separation easier.  Print with thicker walls for a little extra strength.  Think the default is .8mm, I bumped to 1.2 mm.

Assembly Hull

I am not that great with glue and assembly and tend to make a mess, but less glue is usually better. Test fit everything to ensure prints are free from burrs and things that will make parts not mate cleanly.  All holes in parts are about 6mm and should be filed with a 1/4" round file to ensure a cleaned up axle will move smoothly.

1) Glue Front and Rear bottom hull segments

2) Clean up the driver port pieces and make sure it the view port slides OK.  Glue driver port into the Front Top hull segment.

3) Glue Front and Rear hull top segments to the Hull bottom.  I find a couple of adjustable clamps helpful and sometime rubber bands help keep things tight while the 5 min epoxy sets.  The driver Port must be installed ahead of this as it won't slip in later.

4) Glue in the top axle stops into the guides on the inside of the hull.

5) Insert right and left motors and glue in motor mounts to hold them in place.  Make sure you have soldered on leads first. 

6) Make up 16 road wheel sets from the 48 road wheels by glueing together 3 road wheels with a 12mm spacer.  I printed the rear axle and used it for alignment while glue set then recleaned up the hole with a 1/4 file.  Each wheel set should have two wheels back-to-back, a 12mm spacer, and the third wheel with the detail facing outward.  If you did tires in TPU they should just stretch around each wheel and hold in place without glue.

7) When cleaned up wheels can go on the axles alternating the double pair inward or outward.  For the inward pair wheel start with an 8 mm spacer, the wheel set, then secure with an Axle plug and a touch of glue.  For the outward pair start with a 1 mm spacer, the wheel set, then an 8 mm spacer, and secure with an axle plug and touch of glue.  See picture for the layout.  The first wheel set should have the wheel pair in an outward orientation and alternate from there.  When inserting the axles into the hull they should slide through an axle stop with the spring pocket to the back and facing upward.  I used a touch of glue in the axle stop, but might be easier to use an axle plug on the back to secure them

8) You should be able to slip springs into pockets and over the pin of the upper stop.  I used 5 mm x 25mm springs from a kit.  See picture.  This seemed to work well once the tank was loaded with batteries and such. Spring assortments of tiny springs are under $10 at your favorite online vendor.

9) Assemble the drive sprockets, each uses two sprockets and a sprocket spacer, align on a spare axle and clean up when set. I used some track wrapped around the sprocket to align the teeth of the sprocket. (important) Assemble the idler wheels, each uses two wheels and an idler spacer, same routine.

10) Insert a front axle through drive guard and glue drive guards on front hull slipping keyed axle over the shaft of the motor. A touch of glue inside the axle helps secure it to the motor. place a washer over the front axle and then glue the sprocket assembly to the front axle.  It is a tight fit to slide the sprocket teeth past the front wheel set but should be able to with a little force.

11) Slide rear axle through hull.  Glue a pair of spacer6plus spacers over axle and glue to hull, two on each side.  This strengthened the axle to reduce flex.  When set add a 1mm washer and slip the idler wheel over and secure with an axle plug.

12) Link together 70 track pieces one right one left with Track Pins and a tiny bit of glue to secure the pin head to the track.  (7 - 10-piece segments).  Install track around wheels, sprocket, and idler secure with final track pin.  Adjust number of cleats to be somewhat taught but lay as shown in picture.  You will likely need a few extra cleats. Track pin heads should face outward, the guides on track should fit outside the double wheel pairs and inside the outer single wheels.  Sprocket should engage the track cleanly.

13) Install side fenders.  You can print as one piece if you printer accommodates the size.  Used the guides on the side of the hull to ensure they are positioned correctly.

14) Install front, rear fenders and exhaust stacks.  Test fit to ensure alignment and glue in place.  If you want the front fenders to lift on the hinge you will need to cut under the tab that secures it to the outer piece of the fender.  

15) Install the hull base MG.  Glue it into upper hull and the ball and gun should snap in.

Assembly Turret and Deck

1) Join top deck pieces.  Deck can be printed as one piece if printer size accommodates it.

2) Insert turret through deck and glue Turret base to it.  Be careful to keep glue only to mating surface.

3) Slide N20 gear onto drive shaft of motor, slip motor into carrier on the turret base roller.  Make sure to have soldered leads to it ahead of time.

4) Glue turret base roller to bottom of deck around Turret base.  Make sure the N20 gear engages the teeth of the Turret base ring tightly while the glue sets.  When secure add 8mm spacers as rollers and secure with axle plugs. When turned upright the turret should ride on a lazy suzan but be locked in place by the meshed gear teeth.

5) screw an arm onto the SG90 shaft. (comes with the SG90) Glue the SG90 servo into the carrier in the turret with the shaft in the high position.  Glue the mantlet tether to the back side of the mantlet to the far side of the gun hole.

6) Secure Mantlet to Turret with Turret pins and secure with a touch of glue.  Wire the top and bottom holes of the mantlet tether to the servo arm.  I used some thin garden wire.  

7) Snap in deck hatch scopes to hatches then glue Deck hatches in.  Glue carefully and scopes should rotate after the glue is set.  Install grates to the back deck with a touch of glue.

8) The main gun just slides into mantlet.  

9) Connect hinge to Turret hatch with a piece of filament.  Glue hinge to turret.

10) Install the Commander hatch and clean up the Lid to close and attach with a piece of filament.

11) Attach the Turret Bin to back of turret between the two pistol ports.

12) Added smoke canisters, attach to turret if desired.

Electronics

1) mount control electronics to carrier boards.  Secure each with a couple caps glued to the pins.  Glue a 25 pin bread board to the carrier.  I used it for 5 and 12 volt power distribution and be eliminated if you solder everything.

2) Wire it up...  I used 25 pin bread board to manage power and ground connections.

esp32 connections

• D32 connected to L298N Driver ENA

• D33 connected to L298N Driver IN1

• D25 connected to L298N Driver IN2

• D26 connected to L298N Driver IN3

• D27 connected to L298N Driver IN4

• D14 connected to L298N Driver ENB

• D22 connected to L298N Driver ENA (second driver)

• D19 connected to L298N Driver IN4 (second driver)

• D18 connected to L298N Driver IN3 (second driver)

• D23 connected to SG90 pwm input, SG90 picks up 5v and ground off expansion board rails.

Jumper esp32 expansion board to 5v for power rail

jumper l298 to use external 5v as 14.8 input is too high for the internal regulator

wire 14.8 battery output to voltage regulator input and adjust vr output to 5v

run voltage regulator output 5v to ESP32 expansion board and 5v inputs to L298s 

run 14.8 to L298 motor input

connect all grounds back to battery pack

wire motors to output side of L298s

3) The carriers should slip in per picture and leave room for the N20 motor that drives the turret.

4 Load the program via a usb cable and the IDE with no batteries installed.  You should be able to test with just 5v coming from USB.  Guessing each motor has a 50/50 chance of having polarity right.  That can be correct by swapping wires at the controller, or changing the H-Bridge control in the program.  Once you have all working you can drop in batteries and go...  Drive speed has 4 levels and is controlled by repeat presses of the appropriate button.  Turret and gun servo have one speed and are set in the program.

Added sample Arduino application for ESP32 control program.

If you got this far added a few extra accessories here.