#077 IJN/Mitsubishi A5M2b

Building the Wingsy Kits A5M2b in-flight for the 2023 Model Officers Mess birthday bash raising money and awareness for the Models for Heroes charity.

Build

Here’s a quick demo..

Notes

Model length: 157.6 mm Wingspan: 229.2 mm

Kit contents:

Plastic parts: 90
- 6 plastic runners
- 1 clear runner
Photoetched parts: 48
Film
Decal sheet, 4 options:
- IJN Type 96 carrier-based fighter II 12 Kokutai, China 1938, (155)
- IJN Type 96 carrier-based fighter II 12 Kokutai, China 1938, (154)
- IJN Type 96 carrier-based fighter II 12 Kokutai, China 1938, (165)
- IJN Type 96 carrier-based fighter II Hyakurihara Kokutai, Ibaraki, 1940-1941 (113)

Scheme 4

IJN Type 96 carrier-based fighter II Hyakurihara Kokutai, Ibaraki, 1940-1941 (113)

Feature	Color	Recommended	Paint Used
instrument detail	black	C2/H2	H2
Tail	red	C3/H3	H3
Fuselage	silver	C8/H8	H8
Prop front, engine	steel	C28/H18	H18
Cowling	Cowling color	C125	H2
Cockpit interior	Cockpit color (Mitsubishi)	C126	H60 + H31
Prop rear, antenna mast	Red Brown	C131	H47 (darkened a little?)
exhaust	Burnt Iron	C61/H76	H76
	Tire Black	C137
	IJN Gray	C35/H61	H61

Circuit Design

The controller is implemented in code on an ATtiny85. Some circuit notes:

the PWM outputs are used to control low-side n-channel FETs rather than directly drive the outputs. This ensures that current load on the ATtiny85 does not exceed limits (10mA per pin, 60mA total).
the LEDs and accompanying current-limiting resistors are just for demonstration purposes - these can be changed as required for a particular application.
the duty cycle of the motor control is set based on reading a variable resistor.
a fly-back diode is placed across the motor to drain any voltage spike as the motor load is switched
I initially built this to be run from 5V USB but got stumped trying to hide a suitable power supply in the picture frame. Luckily, the circuit also works just fin on 3V (2xAAA) - though I don’t know how long the batteries will last.

schematic

Testing the circuits on a breadboard:

bb_build

Note: with this motor and propeller, I needed the motor connected in “reverse” for correct prop rotation.

Code Organisation

The main script MitsubishiA5M2b.ino runs the main loop. It uses two support classes to orchestrate the effects:

pwm_motor.h/pwm_motor.cpp encapsulates the PWM motor drive, using variable resistor input to set the duty cycle.
flame.h/flame.cpp implements the flickering algorithm for a the flames.
- on each update it adjusts the flames brightness
- the maximum change per update is set by the brightness input
- the actual change in brightness is determined by the mix value for each flame. This sets the percentage of the new value that is mixed with the old value. Lower values will mean more slowly changing updates

See the GitHub repo for sources.

The ATtiny85 is programmed using an Arduino Uno as the in-circuit programmer

programming_the_attiny

Build Log

This is how I started - just past 7:30pm Singapore UTC+8. I’ve got the Wingsy Kits A5M2b “Claude” (early version) a micro motor, a pilot stolen from anther kit and a frame I’m planning to use for mounting.

fri-night-start

build01a build01b build01c build01d

we have ignition! motorising was a stretch goal, but the way Wingsy have designed the engine makes it quite easy to mount a micro motor .. controlled by a microprocessor .. it’s a micro machine;-)

build01e

engine detail coming together!

build01f

Saying goodnight from UTC+8 for now and see you all in the morning. Great time so far - caught the live streams starting with Oz and it got me moving. Got most of the subassemblies ready: have ignition; got air! Hopefully it’ll all just fall together tomorrow. As I write, the fund-raiser is already 15% to the goal .. and the event hasn’t even “started” yet. That is pretty amazing!

a bit of head-scratching later and I figured out how all the engine parts fit together!

build01g

build02a build02b build02c build02d build02e build02f build02g build02h build02i

a pity it’s all going to be hidden away, but I blew my morning time budget on the cockpit. the kit makes it pretty irresistible!

build02j

build03a build03b build03c

finally closed up the fuselage

build03d

Since the plane is in-flight, I need a pilot! I stole this from the Tamiya Ki-61 Hien kit and did a rapid paint job. I have a feeling the flying kit is a little too advanced for the Claude but, hey..

build04b build04c

build05a build05b build05c

not enough time to paint my own background, so I tropical storm picture from a calendar (shot in Darwin actually)

build05d

put the electronics on protoboard and installed in the rear of the frame

build05f

stuck on the wall (to give it time to cure before I add the load of the plane)

build05g

a few coats of H8 later and I’m ready to call it a night (Sat). Just got final paint, decals weathering and installation for Sunday. Pretty confident of finishing this in 48 now!

painting the tail

build06a build06b build06c build06d

build07a

canopy closed up and now starting to wrangle the wiring

build07b

mounted and wiring up..

build07c

smoke trails..

build07d

I was impressed by the kit decals: good strong white over red, and they settled down major rudder parts with nothing more than Mr Mark Setter and time.

build07e