tanSky

So here she is... after many sleepless nights and greasy dirty days in the workshop, the tank base is beginning to take shape:

As you can see, the 32mm timing belt track is auto tensioned and sits on independent torsion-style suspension...  This is such a delicate and temperamental procedure to get this exactly right so as to not throw tracks.... (i'm not quite there yet!)

EMD motor

The motors are EMDwheelchair motors from the dark ages, found rusting away on the roof of a mates storage shed, lovingly coaxed back into life over the last week... they draw approx 3.5 amps unloaded at 12v (though they are 24v, they merely run at half speed @12v)... still well fast enough for my testing and exploration purposes.  For operation in the field, however, the power system will be upgraded to 24v to moderate the current requirements (in accordance with ohm's law)...

Checking current draw from motors...

H-Bridge is Robo Claw 2x10amp (underpowered for motors!)... This will be upgraded as finance permits to a 2x25 amp unit to provide ample headroom.  This is a very flexible unit, supporting a multitude of control options, liPo battery protection and high current / thermal cutout.  The added bonus of this unit over theSabretooth in the same price bracket is the Robo Claw supports 'dual channel quadrature decoding' - allowing for a closed-loop control system (accurate positional updates, movement control and feedback) when the vehicle goes autonomous... This will also allow the software to detect if the track is slipping or stalled and adjust power accordingly (reducing strain on the motors and power subsystem).  The ESC is currently set to RC mode, accepting standard servo pulses from 1000-2000 us (supplied by Arduino)...

Motor Controller and Microprocessor installed....

Currently control is via Wii Nunchuck (wired via i2c into Arduino).... with the very handy and very cheap breakout board from Solarbotics... the code library is taken almost directly fromwindmeadow labs

--------------------------000------------------------------>>

Full Code for the project so far can be found here...

                                     --000--

Parts List:

[chassis] - we-ef street light frame

[axles] - 1/2" steel thread bar

[road wheels] - 32mm trolley wheels (bearings to be upgraded later)

[suspension] - steel flat bar + bolts & washers (see diag..)

[drive wheel / idler] - 2x timing belt cogs - to be covered in rubber for friction drive..

[tracks] - 2x 32mm timing belt (can be upgraded to 2 on each side if necessary for more traction / surface area)

[motor] - 2x EMD 1/4 Hp 24vDC wheelchair motors (electro-magnetic brake removed due to ESC regen braking)

[power] - 12v battery (Sealed Lead Acid, 27AH) - will be upgraded to 24v system, LiPo as finance permits..

[microprocessor] - Arduino Uno, powered via BEC on Robo Claw

[H-Bridge] - Robo Claw 2x10a - NEEDS to be upgraded to 2x25 - includes regenerative decel / charge circuit

[control] - Wii Nunchuck + SolarBotics breakout board

[misc] - 10 gauge wiring / 22 gauge wiring / 20A fuse / fuse holder / bolts / washers /springs / nuts / angle bracket

-------------000-----------------------------------------000--------------------------------------------000-------------->>

Fritzing Diagram:

-------------------000-----------------------------------------000--------------------------------------------000------------------->>

Build Process Gallery:

---------000-----------------------------------------000--------------------------------------------000------------------------------>>

......... and lastly, the beast in action:

* Test Flight 001 * on VIMEO....

-&c