4wd Baja 5e based on stretched truggy chassis

Love the ductape.

[othello]

I run the baja with 9s2p A123, eagletree logger and locked center diff. I synched the recorded data to the video of this run.



Video: Baja running on asphalt with eagletree data

Eagletree data of this run


. Max Values: 132A, 3KW, 29500rpm
. On average: 820W, 32A, 27V
. 1127mAh used within slightly more than 2 minutes

[othello]

I disconnected one 9s pack to record the difference between 9s1p A123 and 9s2p A123.

Graph while accelerating from a stand still with 9s1p A123

.Max 107A, 2100W (233W per cell) and voltage drops to 19.62V (2.18V per cell). That's about the max one can expect from an A123 cell without heating them up (a better solder job would also lead to a higher voltage).

Graph while accelerating from a stand still with 9s2p A123

. Max 134A, 3145W (around 174W per cell) and voltage drops to 23.43V (2,6V per cell).

The higher power output with 2p A123 cells is noticeable while accelerating. Acceleration is more explosive ... RPM build up is faster.

[othello]

Time for an update. I made quite a few changes since i posted the last time.

Motor: Neu 1521/1y (1577kv)
ESC: Castle MMM (Punch control 100%, Start Power low, Brake 50%)
Batteries: 7s2p A123 (21V avg)
Gearing: 1:14,56

I'm now using 1:5 GRP Bulldog Baja tires. I mounted them using extended 23mm proline wheel hubs. I wrapped the 23mm hex with a thin aluminium layer to compensate the difference between the 24mm wheel hex and the 23mm hubs. I extended th long rear center cvd with an 8mm steel tube. Unfortunately, i was not able to center it well onto the original cvd pieces. This is why it still wobbles at higher rpms and leads to heavy vibrations.

Picture of the actual test setup (wheighing around 15.65Lbs / 7.1Kg with eagletree logger)


Video of its first test run

According to my eagletree logger i'm using around 29A avg at 21V (around 600W). Peak Amp draw is between 100-125A (up to 2.3KW with the A123 pack). I'm using around 500mAh per minute which translates to an 8 minute runtime with 4000mAh. At 31000rpm with a 1:14,56 gearing top speed should be around 70kph (43mph). Due to the vibrations of the center cvd top speed is somewhat less. The Neu Motor can dissipate it's heat to the main chassis and remains relatively cool. Highest temperature so far 120°F (49°C) with ambient temps around 50°F (10°C).

After it's 4th test run on wet forest soil


Fitted with body and 5s2p 8000mAh lipos


Run on wet gras with an almost locked rear diff: video clip 1 and video clip 2

i tested 2 5s SLS 4000mAh lipos from a friend of mine wired in parallel on this run. AVG voltage 18-20V depending the state of discharge. Compared to the 7s2p A123 pack punch felt slightly better but top speed was slightly slower. Power levels remained comparable to the A123 pack: 600W avg and up to 2.6KW peak. With 7000mAh discharged a runtime of up to 14 minute is possible. Shortly after this test i ordered 2 6s 3600mAh lipos which will be paralleled too.

There are still a few improvements to make. The heavy 1:5 tires and the extended wheel hubs are hard to the suspension components. The center cvd has to be redone properly. And so on ...

[othello]

A detailed view of the motor mount and the extended center CVD

[simplechamp]

Very impressive! I really liked watching the video sync'd up with the EagleTree data.

[brian015]

Looks nice. I bought some of this Al tubing to make an extended cvd for a similar project:

http://cgi.ebay.com/2-x-ALUMINIUM-ROUND-TUBE-8mm-OD-x-500mm-LONG-2mm-W-/250530711785?

How does its thickness compare to the Al tube you used originally? Mine won't need to be quite as long as yours so I'm hoping this will work.

-Brian

[othello]

@simplechamp
Thanks. I posted a few videos with eagletree insert which you may enjoy too in this thread.

@Brian015
I used an AL tube with the following dimensions:
. 5 mm Diameter Outside
. 4 mm Diameter Inside
. 0.5 mm Wall
It got twisted while shooting the last video with Eagletree inserts. The length of my extended CVD is about 330mm. I'd say you should be fine with your choice. I'm now using a steel tube with the same dimensions as your AL tube, but i did not manage to bring my cvd down from 4.5 to 4mm diameter evenly. I hope your cvd has already the proper diameter to fit inside the AL tube.

[brian015]

Originally Posted by othello

@Brian015
I used an AL tube with the following dimensions:
. 5 mm Diameter Outside
. 4 mm Diameter Inside
. 0.5 mm Wall
It got twisted while shooting the last video with Eagletree inserts. The length of my extended CVD is about 330mm. I'd say you should be fine with your choice. I'm now using a steel tube with the same dimensions as your AL tube, but i did not manage to bring my cvd down from 4.5 to 4mm diameter evenly. I hope your cvd has already the proper diameter to fit inside the AL tube.

thanks for the info, and yes, I have 4mm cvds I can use to insert into the Al tubing.

[othello]

For those of you who enjoy onboard videos. I made a few test runs with a gopro HD Hero action cam mounted with zip ties to my "baja".

Handycam pic


test run on asphalt

Test run on forest soil

Short test run on gravel

[redshift]

Othello only the first video works. They all download, but the 'forest' and 'gravel' videos won't open for me.

The first vid looks good tho.

[othello]

hmm ... strange. All videos are encoded the same way. I can open them with Windows Media Player, VLC, Media Player Classic ...

I updated all 3 Links. Maybe you have better luck now.

You may want to download VLC (Media Player) and try those videos again.

[redshift]

I tried my second browser and they all work

[othello]

Time for an update.

Here is a video we shot last weekend to capture some "action" driving on and trough snow.

A few details about the changes i have done by now to risk a drive through snow.

I have fitted a Castle 1717 motor instead of a Neu 1521 motor (bad carbon wrapping led to a broken rotor magnet on the Neu motor). Gearing has not changed since both motors have a similar kv (i'm still using a 15t pinion with a 52t spur). Due to the actual weather condition here (snow everywhere) i also tried to protect the electric components by fitting some lexan sheets around the chassis. ESC and receiver got an aditional treatment with a protective coating called "wet protect".



I had to cut the upper body to get better access to the batteries and to be able to remove the body without the need of removing the roll cage too.



The cut out parts can still be attached to the body (with velcro).


By now the gap between the body parts is also sealed.

After the first run on snow the chassis looked that way (best lipo pack cooling you can think of ;-))


Reason being i have not closed the opening of the rear side body panels. Since then i have learned my lesson and shortly after that run i made a second one through deep snow with the opening of the side body panels closed and almost no snow entered the rear chassis. The fun on snow can continue ...

[othello]

Some pictures i shot on the same day we shot the video