onroad buggy with 11s1p A123 (pics, ET, vid)

[othello]

Here is my new project (video at the bottom of this thread ;-)). It is based on the robitronic Protos buggy chassis fitted with up to 11s1p A123 cells (36,3V), Kontronik Jazz 55-10-32 Esc and a Neu 1515/2Y (1100kv) smooth can. I had an onroad body (McLaren F1 GTR) laying aroung from my nitro days when it was popular to run buggys with onroad bodys (Rally Game series). 2 simple body mounts and a front bumper were added as well as onroad tires.

Final result


Some shots without body (with 5s1p + 4s1p A123 onboard)


Right side with electronics (Servo, receiver, BEC, eagletree recorder)


Left side with motor and top mounted ESC


With 11s1p A123 it wheighs 9.5lbs (4.3Kg) ready to roll. After some test runs with a 14 tooth pinion and 9s1p A123 it was time to gear up and add some cells to get more wheel RPMs. On my last run i used an 18 tooth pinion (overall gearing: 1:8,94) and 11s1p A123 which brought the speed up to 50mph.

Eagletree graph of 2 top speed passes (first one was against the wind, thus more power is needed ;-))

When looking at the second speed pass:
. After an Amp peak of 46A (1312W), current drops to 18.1A and the motor tops out at around 34800rpm which translates to a calculated top speed of 50mph (80km/h).
. Voltage at top speed is at 32V times 18.1A = 580 Watt to hold this speed level.

Here is the video of this run

Runtime hovers between 7-8 minutes (Average amp draw around 18A = 570 Watt). Peak Power: 1750 Watt. Normally around 1300-1400 Watt while accelerating. At higher levels the tires will loose grip (i need better tires suited for those low temp levels). Motor temperature at the end of this run: 95°F (35°C) ... outside temperature: 43°F (6°C). So there is still some room to gear it up.

As you might have seen it on the video, i am still using full shock travel way (buggy setup). The car still feels very stable at full speed and remains precisely steerable. Nevertheless, I think it's time to lower the chassis and to reduce upward travel to reduce body roll.

[BrianG]

Cool! Not bad runtime for 1p A123's, although I would have thought it would exceed 10 minutes considering the voltage...

Lift-off shouldn't be a concern at those speeds, but it does look funny to have that rear-end squat on an on-road car. Yeah, it's time for a little stiffer springs in the rear at the least...

[snellemin]

Looks like you are having lots of fun man.

[othello]

@BrianG
It definitely looks funny. Especially while accelerating.

Runtime was 10 minutes plus with a 15 tooth pinion and 11s1p A123 ... average Amp draw around 12.5A (420 Watt), max rpm: 38000 -> 45mph (72km/h)

Runtime dropped below 10 minutes with a 17 tooth pinion and 11s1p A123 ... average Amp draw around 15A (475 Watt), max rpm: 36000 -> 48mph (77km/h)

@snellemin
Yep. I never thought it would make this much fun to drive up and down a straight line. But i think its temporarely and at some point i will switch back to offroading again.