4wd Baja 5e based on stretched truggy chassis
 

After having red this thread and this one i always had this idea spinning in my head as i really like the look of the baja 5. Converting a true Baja 5 was no option as it would remain 2wd and would require a new ESC + motor. Powering 20lbs+ with authority would consume a lot of energy and quickly recharging would become problematic. So i decided to go another route with parts i had laying around.

After studying the manual of a baja 5 i ordered the needed parts to reproduce its look: front bumper, main roll cage, center roll cage, roof and clear body. I took 2 1:8 truggy chassis (Robitronic Mantis), overlayed them to get the wheelbase of a Baja and testfitted the roll cage, body and front bumper. I mounted wheel extenders and used proline lpr half offset wheels to extend track width.

I then cut the two chassis plates and fitted basic mounts for the roll cage. I mounted the centerdiff including a Neu 1515/2Y (1100kv) motor. I cut the rear center CVD and used an aluminium tube to extend its length.

There is plenty of room for batteries behind the center diff. I did not want to reconfigure my battery packs (5s1p and 4s1p A123 for my truggy, buggy and truck) so i placed them on the chassis to get a 50/50 front/rear balance. I'm still using a Kontronik Jazz 55/10/32 (55A cont and 10s lipo max) with car mode (forward, brake, backward) to power this car as it has proven to be very reliable in all my 1:8 cars. For peace of mind 2 40x40mm fans were mounted over the motor. 2 single A123 cells were added and gearing was adjusted to 1:14,86 (46t kyosho plastic spur with a 13t pinion). With 11s1p A123 (around 33V under light load) the 1100kv motor should rev up to 36000rpm calculating to a speed of 40mph (65km/h).

This is a pic of how i run the baja. It wheighs 5.5Kg (12.12lbs) with 11s1p A123. The painted body will add around 3.53oz (100gr).
http://www.rc-monster.com/forum/atta...1&d=1242610510

http://www.rc-monster.com/forum/atta...1&d=1242610510

Here is a video of its third test run.

Body is not painted yet, so i run it without it. No shock adjustments were made. I run it with my truggy setup without anti-roll bar -> offroad setup. Acceleration was good (still quite some unloading to the front tires) and ESC braking was amazing. Turning circle was impressive for such a large car ... Crimefighter tires provided huge amount of grip resulting in 3-4 tip overs.

I run the car for 6 minutes. Motor, ESC and Batteries were warm but not hot (outside temperature was 62°F (17°C). I could keep my finger on the motor as long as i wanted. Batteries took 1470mAh back while recharging. With 2000mAh utilisable, runtime would have been around 8 minutes with this driving style. This translates to an average Amp draw of 15A. With 33V (11s x 3V) average power calculates to 500W. Motor temp will climb and runtime will fall depending on how hard i drive.

There is more then enough room for improvements. Especially shock and anti-roll bar setup. This car is meant for offroad and not for onroad. It was sort of a proof of concept run and to get an idea if my lengthened CVD is up to the job (it vibrates too much but remained in one piece: a steel tube would be more apropriate).

What do you guys think?

upps ... there are few pics missing in my previous post which where shown in preview mode when i edited the entry.

http://www.rc-monster.com/forum/atta...1&d=1242636695

http://www.rc-monster.com/forum/atta...1&d=1242636695

Looks good, but those are some LONG center shafts.

Try to get some 24mm hexes and Baja wheels/tires for it to complete the look. Pro-Line Desperado wheels with some Hostile A/T tires would work nicely.

Looks great. It is a pity that proline does not have more choice in the 40 series line. You could run 40 series on the back and mt tires on the front for the staggered tire look.

It looks faster then a Baja. Very nice build othello.

Thanks guys.

Truely, tire choice is a pity. Wider Rear tire: i think Muggy tires should fit the bill but i don't think having a heavier rotating mass on the rear is a good choice with 4wd as it would make the center diff unload even more to the front tires = less acceleration. I really don't want to add too much wheight (especially rotating mass) as it is "only" powered by a Neu 1515. The original Baja tires would look good but the front tires were never designed for 4wd and due to its beadlock design should be relative heavy compared to truggy lpr race tires. Wow, those hostile tires look mean (would be perfect for grass i guess, but not a good choice for a dry track). I think i will just stick with truggy tires as handling seems already to be where i want it to be. Good handling is an important objective. Of course riding height will never reach Baja level with this smaller tire choice. Maybe i change my mind in the future ;-) I look forward to your 1:5 conversion, Lincpimp.

I made a run on my prefered bashing spot. Here is a small video showing its handling on a small wood track. I did not push the car as the electric components were still unprotected without body and i haven't made any improvements yet to stop the long center shaft from swinging. I never hit full speed and never braked, just rolled into the curves. I was amazed by its handling. I could swing the rear axle around in a very controlled way, making even the hairpin curve very easy to drive. The car simply drifted over all 4 wheels: i guess i will maintain this slightly front biased wheight distribution.

Othello,

Dude this is great work! For such a long chassis, the 4wd really seems to keep things tame. I can't imagine why companies don't dig through their existing parts bins and make one. A longer chasis made of durable plastic and perhaps a thick Thunder Tiger SB4-style center tunnel to house the diff and protect the drive shaft. Can't see where extra cost would even factor in, maybe for wheels and tires perhaps.

that looks sick in the video you gotta get your litte bugs worked out with the swiing shaft and get that body on and painted this looks like itd be WAY nicer to have over a regular converted baja....

When I started one of the threads you looked at, this is what I had in mind. Nice job

Nice job, i bet the long chassis should make it more stable.

...yup thats pretty much what i am looking at too but slightly shioorter...looks good though Othello...great work...more pictures (and slightly different ideas) for us to R&D...Good job...

...sorry...watched the video after i posted...was just going on the still shots...HELL nice ride to it mate...smooth and flowing...I think the length of it hides the shock action as opposed to a 'bouncy' truck...Corners really well with just the right slide...nice...

...i just mentioned in on oe the other conversion threads about the baja rim adaptors coming from HPI for the Savage 5T soon...I reckon that a FULL set of baja fronts will do the truck justice for sure...The rears i reckon would be just too heavy, as you suggested...

Third video while running on grass.

This was its first run on this type of surface. Still not pushing the car to its limit due to running it without body. You can actually hear the long centershaft rubbing against metal especially when i release throttle to neutral. The aluminium tube copes well with torque as it doesn't twist, but is to thin and starts to swing. i can actually bend it with my fingers. Using a thicker aluminum tube or even better a steel tube should cure this problem.

Since i made this video i have already performed 7 further test runs. Even with 9s1p A123 i had a lot of fun while running on grass: motor temperature remains absolutely uncritical even when pushing the car on higher grass. With 9s1p runtime dropped to 7 minute plus while pushing the car hardly on my wood track. 10s1p A123 seems to be more then enough power and top speed is perfect for a smaller track: Motor temperature is higher though as i did not adjust the pinion. With 11s1p A123 i have all the power i need to goof around. Motor temperature will reach higher levels as with 9s1p or 10s1p A123 as more power is generated with higher voltage (witout changing pinion).

@killajb
I think every company featuring a 1:8 truggy could easely acomplish something similar with a more factory build finish ;-)

@rootar
Hard to say. I really would like to drive a real Baja. 2wd is fun to drive at times. I'm glad that hpi has built a baja as it is superbly looking when compared to other big rc-cars.

@magman:
Your question was the initial spark to get this project rolling.

@D8Driver
It is definitively more stable than my 1:8 truggy, Buggy or truck. Very easy and predictable to drive. With a 1:8 Buggy you have a lot more to do behind your transmitter.

@BitHed
Chassis length does help. Still needs more shock travel on the rear axle as tires are smaller than the original Baja ones. I think you can see on the video that the chassis is sometimes bottoming out on the rear axle.

Great project! I am jealous ;)

Where have you found those CVD's?

Are there any 24mm hex adapters avalible?

...i havent seen the HPI ones for the Savage 5T yet but they should be out soon...just wondering what time lag HPI will put on them...Shouldnt be TOO long because I reckon they are aiming for the XL to 5T crowd...Keep y'all posted...

Body is now painted and stickers are applied. I'm not 100% convinced with the result. I might change sticker positions.

http://www.rc-monster.com/forum/atta...1&d=1242870364

http://www.rc-monster.com/forum/atta...1&d=1242870364

@Maciolus
I lenghtened an original center CVD by cutting it in two halves. Added length with an aluminium tube which is glued onto the two cvd halves. A steel tube would have been a better choice since my aluminum tube is to thin and starts to swing under load.

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

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.

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.

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
http://bt2007.braintrust.at/ds/rc/ba...o_stillpic.jpg

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.

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

http://www.rc-monster.com/forum/atta...1&d=1247349317

Video: Baja running on asphalt with eagletree data

Eagletree data of this run
http://www.rc-monster.com/forum/atta...1&d=1247349468

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

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
http://www.rc-monster.com/forum/atta...1&d=1247390913
.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
http://www.rc-monster.com/forum/atta...1&d=1247390913
. 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.

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)
http://www.rc-monster.com/forum/atta...1&d=1272318774

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
http://www.rc-monster.com/forum/atta...1&d=1272318774

Fitted with body and 5s2p 8000mAh lipos
http://www.rc-monster.com/forum/atta...1&d=1272318774

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 ...

A detailed view of the motor mount and the extended center CVD
http://www.rc-monster.com/forum/atta...1&d=1272319989

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

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

@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.

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

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
http://www.rc-monster.com/forum/atta...1&d=1275062812

test run on asphalt

Test run on forest soil

Short test run on gravel

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.

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.

I tried my second browser and they all work :great:

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".

http://www.rc-monster.com/forum/atta...1&d=1293054654

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.

http://www.rc-monster.com/forum/atta...1&d=1293055157

The cut out parts can still be attached to the body (with velcro).
http://www.rc-monster.com/forum/atta...1&d=1293055336

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 ;-))
http://www.rc-monster.com/forum/atta...1&d=1293056259

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 ...

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

http://www.rc-monster.com/forum/atta...1&d=1293057122

http://www.rc-monster.com/forum/atta...1&d=1293057122

http://www.rc-monster.com/forum/atta...1&d=1293057122

http://www.rc-monster.com/forum/atta...1&d=1293057194

Thats pretty epic, you can really see the suspension and steering working in that video. Great photos too. :yes:

wow, really cool to see a oversteering electric baja :) especially in such good video quality

Again, having some fun driving on snow ... Driving and filming (so no zoom in). Videos unedited und uncut.

video part 1
video part 2

awesome power.... you will kill the gas bajas :whip::yes:

Finaly spring is here and grip level is right where it should be. I shot a video this morning while driving at my favorite bash spot. The video is almost uncut and represents the complete run till the batteries were depleted.

Here is the video for download
alternative: Same video from a streaming server (does not require a complete download)

The batteries (2x 6s Turnigy 3600mah 30C wired in paralel) were depleted in about 11 minutes. I am usually putting back 3500mAh per batterie (meaning i`m using around 7000mAh). Average values: 636mAh per minutes, 38A or 850W.

As my chassis is almost completly closed and outside temperatures are slowly rising (16°C / 61°F) the Castle 1717 begins to warm up noticeably(around 65°C / 150°F). There is already some heat transfer from the motor to the chassis plate (due to the motor mount and the motor lying on the chassis plate). But, there is still potential to optimise heat transfer and cool this motor further (which i think will be needed when summer hits).

I had overlooked this thread previously, but I have to admit the vehicle looks very capable and also fun to drive. How about some jumping videos? Nothing too drastic. Just a little sort of track action that can show how it would handle in a more competitive envronment. Nice build and love the personal custom work as well. Good creative outlook to overcome the 2wd aspect of the 5b. I can not believe that HPI has not gotten the hint and come up with its own 4X4 version of this 1/5th scale buggy. They are missing out on a pretty good size market by avoiding the shift to 4WD.