Fun with Mad Truck

[Janezki]

Had this cheapo chinese Heng Long Mad Truck lying at the closet (in pieces) for almost a year, until I remembered it's existence.
I bought it as a roller, installed a brushless setup and bashed couple of times until it broke some critical parts (including steering servo, front shock tower, rear diff, center driveshaft, spur gear) and then forgot the whole car...

So, I decided to see how it would run with a setup that moved my XL Savage without any problems...
At first I tried it with rear wheel drive only, but that setup was so undriveable (even with gyro) I had to order new differentials and center driveshaft to get the 4WD working.
With 4 wheel drive and lots of power it was actually quite nice to drive and handled well on tarmac. Unfortunaltely the driveline doesn't hold up under the power and the rear diff broke in under two minutes, even though I was careful with the throttle at the beginning...





Here are the specs:

motor: KD36-74-15XL 1100kv
gearing: mod1 20t pinion/40t spur
diffs: stock 11/34
esc: MGM ComPro 12018-3 car expert
battery: 22.2V 4000mAh Zippy LiPo

Brian's calculator gave me this data with the above setup:

Differential Ratio: 3.091
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 40
Pinion Tooth Count: 20
Total Voltage: 22.2
Motor KV: 1100
Tire Diameter (inches): 3.93
Tire Ballooning (inches): 0.5
Motor Current Draw: 45
Motor coil Ω: 0
Spur/Pinion Ratio: 2 : 1
Total Ratio: 6.182 : 1
Tire Circumference (inches): 15.49 inches (393.4 mm)
Total Motor Speed: 24420 RPM
Vehicle Speed: 57.94 mph (93.07 km/h)
Effective KV Value: 1100
KT constant: 1.23 oz-in/A
Motor Torque: 0.29 ft-lbs
Final Torque: 1.78 ft-lbs
Final Power: 999 watts (1.3 HP)

Check out the video from the test drive by clicking the picture below:
HD version available - sorry about the wind noise, it was nearly storming...



And finally here's Eagle Tree chart from the testing session:



Now if I could only find driveline parts strong enough...