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

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
http://www.braintrust.at/2007/ds/rc/..._side_body.jpg

Some shots without body (with 5s1p + 4s1p A123 onboard)
http://www.braintrust.at/2007/ds/rc/...4_top_side.jpg

Right side with electronics (Servo, receiver, BEC, eagletree recorder)
http://www.braintrust.at/2007/ds/rc/...right_side.jpg

Left side with motor and top mounted ESC
http://www.braintrust.at/2007/ds/rc/..._left_side.jpg

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 ;-))
http://www.braintrust.at/2007/ds/rc/..._graph_11s.gif
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.

<b>Here is the video of this run</b>

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.

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. :smile: Yeah, it's time for a little stiffer springs in the rear at the least...

Looks like you are having lots of fun man.

@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.