Arrma Limitless Project

The Arrma Limitless is a large scale, high speed vehicle similar in principle to the Losi 6iX I used to have but sold, with all the attendant strengths and weaknesses.  So why in the world would I buy one?  It wasn't my fault.

In August of 2020, Horizon Hobby acquired Pro-Line Racing.  Horizon owns lots of other brands like Arrma and Axial, so this meant that production and support of Pro-Line's ProMT chassis was soon halted to avoid competition with their other brands.  On one fateful day in 2021 I plowed my ProMT into the neighbor's stone mailbox post at 40mph.  It held up pretty well, all things considered, but the front bulkhead cracked.  ProMT parts, by this time, were sold out all over the world so I was faced with potentially retiring my favorite high speed truck.  The only possibility I could see of saving it was to try to find a parts donor vehicle, so I took a look on the ProMT Facebook group.  In a stunning coincidence, I found one for sale only a few miles from my house.  This was an almost perfect find except that it wasn't really a parts truck, it was a complete runner with a nice power system so it wasn't cheap.  Being me, I bought it anyway, completely tore it down, and pilfered the needed bulkhead from it.  My ProMT was now back in business and I had lots of other spare parts left over for when I might need them.  I also had a 6s Arrma power system with nothing in particular in which to install it.  You know what that power system would be a perfect fit for?  The Limitless.

By way of comparison (and because it is interesting to me), the Limitless motor is 40mm in diameter and 74mm long.  The motor in the Losi 6iX was 58mm in diameter and 88mm long, so it still absolutely dwarfs the Limitless in terms of obscenity.  That would probably help explain why the Limitless motor gets burning hot so quickly.

So that's how I got here.  The Limitless is sold as a roller with no electronics.  This is a 1/7 scale speed juggernaut.  The power system fit perfectly.  Just as expected it is insanely fast, and also just as expected I have nowhere to really drive it.  I would say that this experience has taught me something but I'm quite sure that it hasn't.  Just to add insult to injury, I also bought a bunch of telemetry sensors for it, also forgetting another previous lesson which is that you can't look down at telemetry when you are driving 80mph.  Live and learn.  Or not.

Update:  This model was destroyed in the 2022 fire.  It has not been replaced.

Here is the massive box in which the Limitless arrived.  Note that there was no internal packaging and the model was loose in the box indicating that it had been opened before and probably returned.  It shouldn't have been shipped this way.  I couldn't find any damage though.

With the body off you can see the substantial chassis which includes a thick aluminum base plate, an upper stiffening rod, and 4 wheel independent double wishbone suspension with massive aluminum bodied shocks.  There are a lot of aerodynamic aids on this chassis.  The front and rear wings are immediately apparent, but from below you can see the front splitter, the rear diffuser, and the flat bottomed, ducted chassis.

Here is the motor I pulled from the ProMT along with the steel Mod 1 pinion that came with the model.  This is a truly massive pinion as you can see on the right.  That red plate is the motor mount which can slide back and forth to adjust the gear mesh.

The electronics are removable in a module as shown.  I got this lovely Savox servo and Arrma ESC from the ProMT as well.  Inside the radio box is a Spektrum telemetry receiver.  On the right you can see the electronics module installed into the chassis.

I was able to repurpose the old pair of 3s Max Amps batteries that I still had from the Losi 6iX, so at least I didn't make any new purchases to make this run.  There is room for significantly larger batteries than this, and the chassis is even capable of 8s.  I can't imagine driving it on any more power though.  It already reaches thermal shutdown in about 5 minutes of speed runs up and down my street.