Arrma Limitless / Top speed

[Marek_MGM]

Hello everyone!

I have started a new project. I was looking for some challenging project which would be interesting for us as well as for you guys.

My colleague told me that we have an Arrma Limitless in the company, but in really bad condition. It was used for a few tests and for implementing a combo that would fit into the original motor mount – dummy proof. With that combo our top speed record was not that high so we have decided to push this limit a little bit higher with this car. That’s mainly because most of our customers are looking to break the records so we want to have more knowledge in this field and to be able to test our ESCs on the limit as well.

At first, when I saw this car, I thought that with this car will be impossible to reach a higher speed. I was worried about the free space. I wanted to keep using the default body which is extremely low. My 1/10 scale car has more free space than this car huh.

With higher speed is connected bigger motor (LMT 2280 with 1480Kv) and bigger ESC (400A, 15 cells) and more cells (12s) necessary for powering this beast up. The moment we put inside our small compact combo for limitless, there wasn´t any space. And now, I started planning to add more cells, a bigger ESC and a longer motor.

We spent a lot of time thinking about how we will place this huge ESC into this small car. We found only one place where we can put this ESC without doing any changes on the default parts. My main goal was to place everything without any changes on the main plate or adding holes for mounting.

 

I removed the factory battery holders and printed my own battery holder. I moved both batteries to one side because the length of the motor compel me to rotate the centre spur gear with motor mount to the opposite side. 

 

Unfortunately, I met with another small problem. Our big ESC doesn´t have BEC and I needed to found another place where I can place an additional battery for the receiver. I found some place next to the motor and add another battery holder.

 

And finally, the ESC. I thought that we will be able to place it behind the motor but there wasn´t enough space. Unfortunately, in front of the motor wasn´t enough space as well. So, I decided to place the ESC on the top of the center strut. I removed the fans from the ESC and decrease the height of the cooler and this fit here without any additional free millimeter.

 

Everything was successfully placed. There was a time to put the body on the chassis. Unfortunately, I missed a few millimetres on the back for mounting. I printed additional holders thanks to which I was able to safely mount the body.

 

Finally, we were able to go to give it a first test ride! Before our first test, I went out just for short tests if everything runs smoothly. I was shocked, this car is a beast! I didn´t go over 20 % of the input request. It was too fast and aggressive.

I had to increase the acceleration ramp because too fast acceleration was impossible to control. Immediately when I moved the throttle stick too fast, the car started sliding.

We moved to the airport where we were ready to hit our speed record. After few runs, we achieved a speed of 180 km/h on 10s. I read the history of the run on my computer and realized that I wasn´t on the maximal speed. That was the time to decrease acceleration time in order to reach the top speed. Unfortunately, at the moment when I accelerated too fast, the car started sliding and went immediately out of the track into the grass and the car made 2 or 3 flips... Batteries were damaged and flew out of the car. The crash caused light damage on the back wing and the left-back wheel broke. During the crash, the motor was released and I have got an idea that is necessary to create some support holder for the motor.

Right now, I am working on upgrading back wing and we will be ready to break the limit of 200 km/h.

 

 

Also, I would like to ask if someone has experience with high speeds and if I can do something for holding higher stability in the maximal speed. If you have any ideas on how to upgrade anything I will appreciate it if you will let me know below in the comments. I think that after we hit the 200 my colleagues will be not satisfied and they will need more. We will see how much we can push this limit.

 

Other than upgrades I mentioned, the car is still mainly with stock parts. I believe we can hit 200kmh before we start buying new parts.

 

[Redback]

1 hour ago, Marek_MGM said:

Also, I would like to ask if someone has experience with high speeds and if I can do something for holding higher stability in the maximal speed. If you have any ideas on how to upgrade anything I will appreciate it if you will let me know below in the comments.

Hello, welcome, awesome beast you have built should do 130mph+ with that setup if geared right etc. People are hitting the 200kph on 8s although they do use custom motor mounts.
I noted your shocks dont seem to be wound down, have you setup the rake correctly? back side in the air so when its running it squats a little but doesnt go lower than the front.
Eg heres mine 2-4mm clearance at front, the shocks have rubber tubing inside to prevent over compression. Im no speed expert i have yet to get 100mph from my limitless mainly as lack of places to fully open it up.

 

 

 

Hope this helps, are you based in the uk?, you say you have a runway to use lucky duck! Here's to 200kph club 🍻