1:8 Robitronic BR 50 Trophy Truck - Brushless

[othello]

A new project i was working on the last few days. (Video can be found in my second post)

I bought this car off of ebay as a roller


A comparison shot beside my Robitronic Mantis truggy. Same wheelbase but smaller trackwidth


This is how the chassis looked like before i replaced it


As the BR50 uses the same chassis plate as the Mantis truggy which i already have converted to brushless i onky had to remove the front and rear axles.


I then removed the truggy axles from the truggy chassis plate and replaced them with the BR50 axles. I'm still using a Neu 1515/2Y (1100kv) motor, Kontronik Jazz 55 ESC and 9s1p A123 batteries to power my 1:8 conversions.


5s1p pack at the rear, receiver and BEC box beside the centerdiff and servo with Eagletree logger on top of it at the front of the car


The other side shows the front mounted Neu 1515 motor and the other A123 pack in 4s1p configuration at the rear. The ESc is ziptied between motor and servo on a separate plate which is mounted between front axle and center diff


Switching back to my truggy configuration is easely done. It's just a matter of switching axles and using a smaller pinion. And using another body of course.


As the BR50 trophy truck uses smaller Buggy tires gearing had to be adapted to get similar speed compared to the Mantis truggy. The BR50 axles use the same bevel and ring gears (10:42) when compared to the truggy axles. I use a 46t kyosho plastic spur. I used to run my truggy with a 14 or 15t pinion. I chose a 18t pinion. Overall reduction: 1:10,73. With 9s A123 cells the 1100kv motor should rev around 30000rpm max under load (9s x 3V x 1100kv). Which leads to a calculated top speed of 37-38mph (around 60km/h). A good starting point for this car as i never had temperature issues at this speed level when i run my truggy (heavier wheels) and the nitro version was clocked at 32mph or 35mph depending which reviews you read: rccaraction or rccardriver.

Ready to roll the BR50 wheighs 10.1lbs / 4.6Kg. The body alone wheighs 1.1lbs / 500gr. Batteries wheigh 1.5lbs / 706gr.

On its first maiden a few gas stabs on asphalt showed that top speed was right were i expected it to be. No need for a smaller or bigger pinion from a speed point of view. Eventhough my typical RC spot was completely soaked, wet and muddy (snow had almost melted) i chose to give it a run. Everything went fine aside from 2 tires which came partly unglued.

Well this how the BR50 looked like after its first run


Well atleast the pinion remained uncovered with mud ;-)

[othello]

I obviously had to do something against all the mud and stuff getting inside. Well, after some few hours tooling around with my dremel and parts i had laying around the car was ready for its second maiden. But by then a fairly huge amount of snow had fallen, so i had to run the BR50 on asphalt still very wet and partly covered with snow.

Here you go: Part 1 of the video and part 2 of the video

Not a lot of grip but nice power slides and roosters behind the car.

This time the car was covered with wet snow and wheighed a "ton" when lifted from the ground.


Showing with what i came up to protect the electric components from the elements


It worked out alright, but still some snow had protuded the front as i only had glued some lexan parts to the chassis. Lesson learned. Has to be screwed to the chassis. No wonder there ... i made some shortcuts to get her to run on that day.


Here is the eagleetree Graph of 1 minute of this run (basicly the first part of the video)

. The temperature readings can be ignored. After the run the motor was cold. But it took me atleast 2 minutes to get the body and protection off the car.
. On average 16,5A (412 Watt)
. Peak amps are hovering between 40-55A while accelerating. Power peak at 1331 Watt. Those number will rise with grip.
. Max 26500rpm as i really couldn't hold full speed for a long time. Place is too small and it was too wet.
. The car needed 276mAh for 1 minute. Runtime calculates to a little over 7 minutes with 2000mAh.

And for those of you who are wondering if the SC8 body and tires might fit. I found those pics (Robitronic USA profile at myspace)

[Hardstyle]

Boy thats dirty. Nice videos. Where did the car vanish at the 2nd video
Suprising that you didn't have any temp issues with that kind of protection..

[othello]

Looks funny, doesn't it. Especially since nothing else has moved ;-) The driver of this car took quite some time to find a parking spot. I edited this part out of the video.

While running my truggy with the same components ... motor temps hovered between 30-40°C (86-104°F) with outside temps around 0°C (32°F). Protection was not that good but still not a lot of airflow around the motor. Therefore i did not worry about temps even with this kind of protection. Temperatures will rise when running on a high grip surface ... i usually run 2 fans above the motor. i might mount them again when outside temps will start to rise. The Neu 1515 is somewhat too much motor for those small buggy tires. Temperature should not be too much of a concern.

[othello]

Snow got pretty abundant here over the last few days. Further testdrives had again to cope with this circumstance. This time the snow consistency was all but ideal nevertheless i had to test how the truck would perform on thick snow.

I cut a small video of the last few runs: http://194.158.136.73/ds/rc/br50_run9_11_snow.wmv

Conditions were perfect for paddle tires.

[othello]

I was finally able to test the truck on a surface with more grip. Here is a short video of this run.

Peak Amp draw hovered between 50-65A (around 1250-1500 Watt) while accelerating with a short burst at 85A (1760 Watt).

I'm now facing a new challenge. The body gets very heavy while driving on wet grass.

[suicideneil]

Sweet vid, that thing handles very very well, and so quiet too.

On the mud front, seems like you need some form of mudguards over the tires (but inside the shell) to deflect all the dirt that is kicked up. Shouldnt be to difficult to make something suitable using some thin lexan off cuts and shoe-goo...

[othello]

Thanks. I'm happy with its handling. I'm using a kyosho plastic spur ... much quiter operation when compared to the original metal spur.

I saw a nice "upgrade" to protect the chassis from mud mounted on a slash. I think i will try something along those lines. Pictures posted by "silex" on our austrian RC forum.

http://img.webme.com/pic/s/silex-ts/radlaestenkaro.jpg
http://img.webme.com/pic/s/silex-ts/radkaestenrear.jpg
http://img.webme.com/pic/s/silex-ts/radkaestenfront.jpg

[suicideneil]

Cool, thats pretty much what I had in mind- the rubber mudflaps are a nice scale touch

[othello]

I wasn't too happy with the appearance of this truck with those small buggy tires. I therefore fitted truggy tires to the BR50 Chassis. Crimefighters LPR with half offset seemed to be the most pleasing choice.

I made some preliminary test runs without body (Body had to be trimmed somewhat)
. video on snow
. video on asphalt

Eventhough those runs did not show how the chassis would perform with grip i decided to trim the body to fit the bigger truggy wheels.



I had to wait a week to run the modified BR50 on gras (without snow). Well as good as it looks, the track width is still to narrow to make it corner properly without tipping over.
. video on grass

I therefore decided to mount the BR50 body on the Robitronic Mantis truggy Chassis (with truggy arms).



First off i mounted crimefighter tires with standard offset and made a similar test run.
. video on grass with truggy chassis and standard offset truggy tires

Those tires had less grip due to their harder XTR compound. No tipping over due to lesser grip and a wider track width.

To get even more track width i mounted my half offset crimefighter tires


. video on grass with truggy chassis and half offset tires

To complete this test series. I made a short run with the BR50 chassis and buggy pin tires.
. video on grass with buggy tires

With buggy tires the car felt more agressive and accelerated better without wheelie tendencies (tires had better grip level). I used a 15t pinion with truggy tires and an 18t pinion with the buggy tires to compensate tire diameter. The narrow track width of the original BR50 chassis is tricky at good grip level and the car might tip over when cornering: less agressive tires should be a better fit. When it comes to its appearence i prefer the look with bigger truggy tires. But even with half offset truggy tires the BR50 chassis is to narrow to get good cornering without tipping over. It's then more suited for fun driving. Truggy tires seem only to work when combined with the wider truggy chassis (with truggy arms).

I will extend my tests when snow has melted completly around my place. My eagletree logger measured power peaks around 1900 Watt (80 Amps) with truggy tires and around 1500 Watt (63 Amps) with buggy tires. Average Watts (450W as oposed to 360W) were higher with truggy tires.

[suicideneil]

I started a thread a while back about using an MT with a Corr type shell- glad to see it works/ looks quite good when put into practice. Handling/cornering has always been the issue with those trucks though, just too long and narrow to work too well without being some insanely good driver...

Originally Posted by suicideneil

I started a thread a while back about using an MT with a Corr type shell- glad to see it works/ looks quite good when put into practice. Handling/cornering has always been the issue with those trucks though, just too long and narrow to work too well without being some insanely good driver...

I run a 1/10 brushless MT with CORR/Short Course shell and 1/8 buggy wheels/tires. Arms are a little wider than what you would see on a Slash/Slayer so stability is pretty reasonable. MT suspension gives it loads of travel so I like to call it a Trophy Truck.

I love the brushless conversion Othello's done to his BR 50 ... I'm glad AE is finally coming out with a reasonably priced SC8E kit.

[othello]

@suicideneil
The only thing that bothered me (aside from appearence) while driving the BR50 with buggy tires was its tendency to tip over when cornernering too fast. After another test with my buggy and the same pin tires i can safely say it was primarely due to the agressive tipe of tire thread as my buggy also had tendencys to tip over while cornering: buggy video. There is no tip over on this vid but before i shot this video i managed to tip over the protos buggy too.

br50 chassis with old Mugen pin tires mounted (very agressive tire thread)


This is my buggy tire selection


Sometimes less grip is just easier to drive. That is why i now run my buggy with axial cubes tires. Tire on the right side. They are the smallest one and do look awefull on the br50 chassis with body mounted. But they give good performance.

@DARKWAV
Thanks. i love to play around with my Robitronic 1:8 chassis. I'm glad that Robitronic sells a more scale like car. My quest for good fitting tires with good performance will go on. I hope we will see more scale like bodys for 1:8 cars in the near future. I envy 1:10 car drivers. They have such a huge selection of superbly scale looking bodys. The SC8E kit looks promising.

[shitoba]

Hey there othello, im new here in the forums but i was wondering what type of motor mount you have for your brushless motor. i have a br50 as well and was interested in turning it into a brushless system. Was it custom made or did you purchase it somewhere? Any information would be highly appreciated. thank you. great looking conversions you have though.

[othello]

There is nothing fancy about my motor mount which i made with my dremel tool. It is based on an emaxx motor mount which i cut and drilled to fit in front of the centerdiff. It is screwed onto the centerdiff right where the brake calipers would normally be mounted. It is reinforced with an aluminium angle which is screwed to the chassis plate and the motor mount.

Looks awefull but does its job so far. (mounted onto the protos buggy chassis ... works on the br50 and mantis chassis too)