Losi five-T brushless with custom body panels (T-Rexx)

[othello]

After having driven a Carson Dirt attack XXL (same chassis as a Rampage XBE) for almost a year i decided to take the next (and likely the last) big step and bought a new Losi 5T roller (without body, tires). I almost pulled the trigger and bought a Losi Desert Buggy XL but given the fact there was no motor mount readily available and that a Losi 5T could simply be given the look of a buggy (i am more partial to buggys than trucks) with some easy to fab lexan body panels i decided against it ... luckily i have talked to a fellow rc buddy which convinced me at last to go for the 5T (his opinion: this is the only rc car which looks like the real deal while driving over bumps).

New out of the box (already fitted with Giant Grip tires). Even a 1:5 buggy looks rather small compared to the losi


Living in a big city ruled out a (loud) gasoline engine. After having watched some youtube videos i decided to go the (cheaper -> had already the esc and 2 4s 8000mah batteries) 8s route eventhough castle explicitely states that their XL2 combo (ESC+2028 motor) is not intended for such heavy 4wd car.

Test fitting of some bl components (trackstar 1:5 Motor only as a stand in)


As this worked out like planed, i ordered a Castle 2028 motor and an rcmonster motor mount. I suppose after having watched the last picture you can make out one big issue the original placement of the center diff poses. I was told that due to the rather extreme angle of the front center cvd the front outdrive of the center diff and the pin of the cvd wears out rather quick especialy when using a powerful brushless system.

[othello]

With the help of a buddy and some aluminium we relocated the center diff to a more ideal position


We could reuse the stock front chassis brace by shortening it somewhat

[othello]

Next i cut some pieces of paper and bolted some simple body panels to the roll cage.


With the help of the paper panels i cut lexan pieces. As my son is big dinosaur fan i chose some pics on the web, printed them and glued them (using xxxmain glue) to the body panels. After having used two cans of tamiya metallic blue color the body panels were ready to be bolted to the cage

This is the final result

[othello]

To finish the body my son put some additional dino stickers to the roof.


The ESC and external BEC were fitted on a simple lexan plate bolted to the Chassis. Battery trays were also fabed with some lexan pieces. The setup than looked liked this.


After a few runs the car looked more like an offroader

[othello]

The used zippy 8000 batterys were replaced by 2 new 4s SLS 10000mAh 25C packs. Thi resulted in a big jump in power output (from 5kW peak up to 7kW peak or 55A average to 90A).

For a short while i have used the castle blower but it was soon replaced by a custon cooling solution for the castle 2028 motor.

2 12v 80x80 fans wired in series and fed by the main batterys and a simple wind tunnel to optimise airflow somewhat.


This resulted in a way cooler motor.

To get an impression of the five-T i have uploaded a few videos:
Pushing the t-rex harder on a smaller grass field
A buddy of mine driving the car on the same grass field
More relaxed driving on my usual bash spot

To give you an idea of what kind of power is needed to drive a 16.6Kg (36.6lbs) like this.

When i'm pushing the car with lots of full throttle passes on grass like in the first video posted i'm getting th following read outs from the xl2 esc

- 91A (2.5kW) average
- 260A (7.1kW) peak
- 6500mAh used in 5 minutes (runtime would be around 7.5 minutes with a full charge
- ESC is already hitting 88.5°C (190°F) ... outside temp: 22°C (71°F)
- When pushing hard this setup is at it's limit

This is the read out of the third video posted

- 60A (1.7kW) average
- 206A (5,8kW) peak
- 5000mAh used in 5.5 minutes, Total runtime would be around 10-11 minutes.
- temps are all in check

[brian015]

Very Nice - I like the set-up and the body.

[phildogg]

Really liking the truck. Looks like a whole lot of fun..

[Arct1k]

Looks great. Very nicely done.

[jayjay283]

very nice, really looks like it could send you to the emergency room

[othello]

Thanks guys. It is a blast to drive. Despite the weight it is still a very sturdy platform. Not much to wrench since around 28 runs. Only the bearings in the rear wheel carrier can get stuck when i drive in the wet ... aside from that nothing.

I have now protected the bearings. Let's see if that helps.


I have made a small upgrade to my motor cooler


I have replaced the 0.8W and 1.2W fans with two 2.5W Sunon fans which has improved air flow significantly. Both fans are now better protected against stones and stuff. Since there is a lot of amps/power displaced by the castle 2028 motor (between 1.7 to 2.5kW average during a run) i'm trying to keep the motor in its comfort zone. I don't really know how efficient this motor is but let us assume it's averaging 85% then there is still a loss of 255-375W in heat which has to be removed.

This setup (with 8s) really is only for fun driving and i'm mostly driving with a short brake during a run (after 4-5 minutes) to check temperatures and giving the components the opportunity to cool off somewhat.

[Pdelcast]

Originally Posted by othello

Thanks guys. It is a blast to drive. Despite the weight it is still a very sturdy platform. Not much to wrench since around 28 runs. Only the bearings in the rear wheel carrier can get stuck when i drive in the wet ... aside from that nothing.


I have replaced the 0.8W and 1.2W fans with two 2.5W Sunon fans which has improved air flow significantly. Both fans are now better protected against stones and stuff. Since there is a lot of amps/power displaced by the castle 2028 motor (between 1.7 to 2.5kW average during a run) i'm trying to keep the motor in its comfort zone. I don't really know how efficient this motor is but let us assume it's averaging 85% then there is still a loss of 255-375W in heat which has to be removed.

This setup (with 8s) really is only for fun driving and i'm mostly driving with a short brake during a run (after 4-5 minutes) to check temperatures and giving the components the opportunity to cool off somewhat.

The 2028 at those power levels is around 88% efficient. (assuming that's the older 2028 -- the newer version of the motor is quite a bit more efficient.)

Thanks!

Patrick

[othello]

Thanks for clearing that up. Bought the motor feb 2014. How to differentiate between the old and new version?

Any thoughts about optimising cooling of the xl2? Is a higher voltage version of the xl2 still on your roadmap?

A bigger 2028er would also be an interesting option. Not much choice for big 4wd cars.

[othello]

I synced the xl2 log data (imported them into the eagletree software) with a new running video of the losi.

Preview picture


The data inserts are partially in german but i think everything is self-explanatory
-> Drossel = Throttle
-> Strom = current

Enjoy the additional inserts while watching the Losi (69mb mp4 video)

XL2 Log viewer graph of this run


Temperatures collected after this run (outside temperature: 32°C // 89°F)
- Motor: depending on the measured part of the motor: 62-74°C // 143-165°F
- SLS battery packs: hottest point 53°C // 127°F
- Turnigy uBEC: 52°C // 125°F
- Center Diff and outdrives: 52-60°C // 125-140°F

[RC-Monster Mike]

Almost 10HP peak output - snappy performance!

[othello]

The 5ive is still running ... but snow has taken over here in Vienna. While pulling the bob(sled) of my son up the hill i wondered if the Losi is able to take over this job. Last sunday i had to try it.

Video 1: first pull try
Video 2: Pulling the bob up the hill
Video 3: And now while my son is sitting in his bob

Never thought that the five is able to pull over 44lbs on snow.

For those who are wondering about the brushless components ... they are protected ;-))