4wd 1:5 onroad car based on stretched 1:8 truggy chassis

[Overdriven]

Very cool project. You're really getting your money's worth out of that Robitronic Truggy, this being it's second configuration!

[othello]

Video on a wide open space

After 6.5 minutes of top speed passes one of the rear tires was completely run down (and lost its insert). I charged around 4000mAh back which corresponds to an average current of 37A (With 22.2V average power: 820W). To get some decent runtime (10 minutes plus) with an even higher top speed i will need around 8000-10000mAh.

@all
Thanx guys. A truly versatile platform indeed.

[othello]

I have changed gearing to 1:7 and have mounted 1:5 GRP onroad tires which results in a calculated top speed of 110km/h (69mph).

short video from today

As the GRP 1:5 tires provide enough grip i will stay with them for now. I'm happy with the actual speed so gearing should also remain as such. Time to buy some new batteries to bump up run time to 10 minutes plus. 2x 6s 5000 wired in parallel should be the ticket for this target.

Track width is to wide but still works using the mercedes body

[_paralyzed_]

I love the looks of the car! I like the track width, I think the wheels look good sitting out a little.

Any chance of posting a video to youtube or something similar, I can't view the videos on a Mac.

[othello]

Thanx _paralized_ . You may install flip4mac on your mac in order to be able to watch WMV Video files. I have reencoded the last video as MP4 file. Quicktime should play it just fine.

Video as MP4 file.

[othello]

Update: i bought a new eagletree micrologger v4 and mounted it on this chassis. I'm now running 2 Turnigy 6s 5000 25C battery packs wired in parallel configuration.

Outside temperature has dropped and snow has already fallen. Nevertheless i have managed to make a few runs. But the data collected still has some flaws as setup of the logger is somewhat tricky.

I have put together a video of a speed run combined with the eagletree data.


From left to right:
- throttle input
- motor speed (rpm)
- motor current (amp)
- battery volatge (v)
- numerical values: Motor temperature (°Celsius) and consumed mAh

video link: WMV Video with eagletree data inserted
video link: MP4 Video with eagletree data inserted

The logger was set to measure 50 samples per seconds:
. Voltage: Add around 3V to the voltage and you should have the real battery voltage (one of the flaws i coped with on this run). Battery voltage should have been at 25.2V when i started this run but only 22V is displayed.
. current: When accelerating and pushing the throttle to the max, the logger measures between 170-180A (i bought the 150A version). I assume that amps are way higher. Current falls to around 80A when the car reaches top speed. The logger falsely shows a voltage of 19.5V at 80A. I assume voltage to be between 21.5-22.5V. Translasting to 1.7-1.8kw to maintain top speed. While braking you can see that amps are rising (the logger can't display negative amps = regenerative braking -> putting amps back to the battery). Average current depends on driving style and is somewhere between 35-60A (or 800-1400W).
. motor speed: You can see some erratic rpm spikes while accelerating and especialy while braking. i assume this comes from the way the ESC is handling the bruhless motor. When you ignore those peaks you will see that the motor tops out at 33000rpm when hitting top speed.
. motor temperature: Outside temperature was around 0°C (32°F). When making speed runs motor temperature only rises relatively slowly (in this case by 10°C within 2.5 minutes). I can safely discharge the batterys continouusly with this driving style (especialy at this outside temperature levels).
. Driving time: When driving as shown on this video a battery charge will last around 10 minutes plus (with 9000-9500mAh put back to the batterys while charged in parallel configuration).

At the end of the video i braked too late and did hit a snow mound (i have to do some small cosmetic work to the body ... aside from that nothing broke).