Another M3 Halftrack (Chasis and drive train) 1/20 scale

M3 halftrack chasis and drive train model. 

Also added short frame version of STLs.  They were the only part that needed a plus size printer.  They can be printed and joined if printing on normal size bed.

If you get this built the body is now uploaded. 

Instructions:

PLA+ for all except tires and track which are TPU.

1 Glue the front, back and side frame pieces along with the crossmember together.  If you are using the short version of the side pieces then they would need to bonded first.

2 Glue roller arms onto frame

3 Glue transfer case to frame

4 Clean up front differential and slide over front axle ensuring it is the correct orientation,  Clean up rear differential and slide over Drive Axle. Glue both axles to frame using guide to align to a leaf spring.  Make sure to align and put drive shafts from transfer case into rear and front differentials.

5 Install/glue hubs on front axle. First place inner hub in outer.  Secure with 2 short 4mm pins, glue only outer edge of pin.  Then slide inner hub onto front axle secure with glue.  Align tab to back and pins vertically so that outer hub swings freely back and forth and the tie rod can secure them to turn together.

6 Stretch TPU tire around front wheels.  Press bearing into wheels. (free up bearings after print, they are tight and frozen after print, add some lithium grease to bearings to help them roll smooth.  I used a tiny screw driver to break the balls free.)  Glue outer bearing hub into outer hub on axle.  

7 Glue roller tires on rollers.  Assemble in pairs with the roller brackets and 3mm pins.  Secure pins with a touch of glue on back.  

8 Install roller arm bracket on roller arm secure with 4mm pin and glue back of pin to secure.

9 Install 2 pairs of rollers into the roller arm bracket with 4mm pins and secure with a touch of glue on back.  Brackets and wheels should turn freely.

10 Install return roller on top of roller arm bracket with 4mm pin.  Trim pin length and secure with glue.

11  Install engine in frame connecting to transmission/transfer case.  Install radiator into frame and connect to engine.  Secure with a touch of glue.

12 Attach rear axle arm for the idler wheel (do not glue).  The tread tightener nut and bolts are used to position and tension the tread.  They can be placed but only glued after tread is tensioned or not glued at all as the tension should hold it in place.  one of the bolts on the tread tightener is normal thread the other reverse.  Take care threading them in initially.  Once in place the nut can be adjusted by turning and the bolts will move in and out together.  They are very limited if glued as it will stress the bolts due to the arc of the arm.

13 Assemble drive wheel and idler wheels.  Glue together the drive wheel with teeth offset on inner and outer wheel.  Attach to axles with 5mm pins after cleaning up and verifying they spin freely.  The wheels should align with road wheel rollers.  The drive wheel should use 2 1mm spacers between axle and wheel.  The Idler used 3 1mm spacers to align properly.

14 Glue two long track strips together with short track slices.  Alignment for cog holes and straightness counts.  I used some super glue for rubber that worked surprisingly well from LOOCTOT.  Stretch around wheels and use tightener to get desired tension. Guessing softer TPU would work best for tracks, i have some stiffer high speed TPU and it produced tracks that were too stiff.

15 install exhaust, glue to exhaust manifold and a touch of glue on the rear axle to secure it.  I don't know why my fake engine needs a fake exhaust, but why not...

16 attach unditching roller and brackets to the front frame and bumper.

Part List:

1 Frame 1
1 Frame 2
1 Frame Front
1 Frame Rear
1 CrossMember
2 Roller Arm
1 Transfer Case
1 Front Axle
1 Front Differential
1 Drive Axle 
1 Drive Differential
2 Front Hub001
2 Front Hub002
1 Tie Rod
2 Front Wheel Bearing
2 Front Wheel
2 Front Wheel Tire
2 Roller Arm Bracket
8 Roller Bracket
8 Roller
8 Roller Tire
8 4mm pin
8 3mm pin
4 4mm pin short
4 5mm pin
4 Idler wheel
4 Drive wheel
4 wheel Space
2 Return Roller
1 Engine
1 Radiator
1 Exhaust
1 Rear Drive Axle Arm
1 Read Drive Axle Arm (Mirror)
2 Tread Tightener Nut
2 Tread Tightener Normal
2 Tread Tightener Reverse
4 Track001 (tpu)
4 Track002 (tpu)
1 exhaust
1 Unditching roller
1 unditch bracket
1 unditch bracket mirror