4wd Baja 5e based on stretched truggy chassis

...the look reminds me of the Tamiya Dark Impact..looks good though...would look great with some bigger knobblier tires too..

[othello]

Yep, with body those tires look somewhat to small. Although handling with truggy tires was perfect. Won't be easy to find good performing light wheight tires with bigger diameter fitting a wheel with the right hex.

[othello]

I shot 2 new videos this evening (filming while driving). Still running on truggy tires as they give good performance.

video on a small forest track
video on grass

I even managed to drift it on asphalt but the flash card was already full.

[othello]

Got some drifting action on video today while running on grass with 10s1p A123, overall gear ratio of 1:13,8 and AKA City Block truggy tires.

Still picture


baja video while drifting on grass

Runtime around 5 minutes with 2060mAh charged back. Motor temp reached 60-70°C (140-158°F) depending on where i measured. Outside temperature around 24°C (75°F).

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.