THE ARRMA LIMITLESS ROLLER
Review by Evo RC
There has always been a gap in the RC market to satisfy the needs of those who want to go not just fast but really really fast. Traxxas tried to fill the gap with the X01 a few years back. Although the X01 is a speed demon in itself, there are limited ways of customising it. Then Arrma, known for their durable machines, had introduced a sort of new concept, the Limitless speed basher roller. The 7 scale roller that allows you to customise the electronics and squeeze out as much speed as you like. The Limitless Street Basher is a bit of a direction change for ARRMA, this was the first time that they’ve released a rolling chassis.
The concept was taken extremely well by RC fanatics and soon after the launch, forums were filled with custom builds as well as ludicrous builds. From MAX6 to Castle combos, 6S to 12S, single dual and quad motors and so on. Basically the Limitless is a blank canvas at a lower price. The roller concept has not always paid off for Arrma, we have see this in the recent discontinued rollers. The Kraton, Outcast 5 scale and the Mojave 7 scale recently got discontinued. Could be due to low sales or stock space vs profit for hobby shops, we don’t really know why yet. The Limitless roller kept being a hit and recently they released the V2 limitless. Comes with a clear body, more 8S ready and a few other changes.
The Limitless V1 has an aluminium main chassis plate, designed to deliver durability and performance. You simply install your own combo, radio system and battery and you’re ready to run, well race in this case. On the surface, the Limitless carries an aerodynamic design that’s meant for top end speed. It’s a blend of an F1 car, an indy car and a modern supercar. Focusing on low drag and high stability with the front and rear wings that can be adjusted to fine tune the performance of your speed run and help you gain more speed with each pass.
For me, it all started with a spare ESC and motor I had. I thought, ok, I might as well get a roller then and I’ve got another thing to play around with. Well I did that but it was a disaster, the ESC blew up and the motor overheated like crazy. It all has to do with gearing and here starts the math calculations. Before we get into this, I want to make one thing clear, I consider myself a hobbyist, I’m not an expert, so other people may have different recommendations.
For a Limitless build you have to do the math before not after. The gearing depends on what you want to do, you want to just purely do speed runs, or you want to bash and drift as well? I quickly learnt that at this stage you’re at a junction, you either choose left and go for just speed runs or you go right and go for bashing. It is simply like that, you cant drift on a speed run setup and you cant do high end speed runs with a bashing setup. Well I tried both.
The speed run setup is the most common choice. Before you start building and ordering parts, you have to do the math. The best gearing calculator I recommend is the Radio Control Info Calculator. The Limitless comes with a 34T fixed centre spool or spur. The smallest pinion you can fit is 27T. The rear and front differentials are 13T input pinion and 43T diff spur. Let’s enter this data in the calculator just as an example below. I’m considering a 6S setup with the standard 2050KV motor:
The result is 192KMPH or 119MPH. This is a theoretical speed meaning it’s not considering friction and the elements. This includes bearing drag, wind drag, terrain drag, energy lost due to shaft vibration and losses due to heat and its dissipation. In reality, you’ll achieve a lower speed but having said that it’s quite close. One has to note that the faster you go the more these elements play a role. I am saying that one has to do the math first because it will be a deciding factor in mainly what parts you need especially combos and batteries which are major costs to your build.
Getting straight to the point, you can go with either a Hobbywing system or a Castle system. This depends on your budget. A Hobbywing system will cost less than 400 euro but will max out at an average real speed of 180 kmph or 112 mph. That’s average, some will get less and some will manage to get better results. It all depends on the setup. This is considered a cheaper solution. In this case you can go for a Hobbywing MAX6 with either a 6S setup 1650KV motor or an 8S 1100KV or 800KV motor. Pinions range from 27T till 34T. You can key this info in the calculator and check out the results. If you’re looking at faster accelerations and higher speeds then you need to switch to a Castle ESC. The Monster X or the Mamba XLX2 combos.
Motors you can get a combo or you can change the motor to say a TP motor. The top speeds here are jaw dropping. Tires that are widely used for speedruns are the GRP branded ones, they have various compounds but the most common are the S3 and the S5, soft and medium.
For high speed runs I don’t recommend cutting air inlets in the body and speed running will heat up the inside in general, so a couple of passes and let it cool for a few minutes. You can trim the front and read spoilers to minimize air drag. To give you an edge, you could research ceramic bearings, bearing lubrication, tire balancing and suspension setups. Best also to keep a heat gun to check those temps. I cannot go through every setup and the complexities of each setup here as there is so much to cover. What I recommend is to do some research and watch some builds on YouTube to have an idea.
I love building an RC that puts a smile on my face rather than spending hundreds on a build then I’m constantly on the edge of my toes driving it and worrying on damaging somthing. If speed does interest you but you’re not after any records, wish to have a fast setup but one which you can bash and drift, then there is another way you can setup your Limitless. I recommend setting up the Hobbywing MAX6 and the Hobbywing 1650KV combo. It’s money well spent. The MAX6 is 8S rated whilst the 1650KV motor is 6S rated. This means that you can bash and drift safely on 6S and maybe do the occasional speed run on 8S. The motor is not meant for constant 8S runs or bashes, so you would be taking on the responsibility of it burning out.
I recommend a 20KG servo, doesn’t have to be high end, a Power HD or Spektrum will do. Just be careful on servo speeds and make sure to have a standard servo horn. For the remote and receiver, I recommend the Radio link RC4GS or the RC6GS combo, preferably with the R6FG receiver. These combos are long range, over 500 and 600 metres in open spaces and come with an integrated gyro, a sort of traction control system.
I also suggest replacing the MAX6 ESC plastic standard fan with a Rocket 35/36mm brushless fan. Standard fans rev around 5K revs, Rockets rev around 15K which will decrease temps by around 15 degrees celsius, a much needed advantage. Two other fans over the motor to keep it cool. The Limitless has one advantage which is also a disadvantage. The body shell wraps tightly around the car which helps its aerodynamics but this means that all your electronics have no fresh air going through. Opening a sort of hood scoop is a bad idea as at high speeds the body shell would create a parachute effect and the Limitless will take flight. Some carefully placed openings will help getting air in but just be careful, best place these openings in a horizontal position, where air can go over the opening and is not forced in.
Batteries is difficult to recommend as there are so many brands out there. Generally a good brand with a high reliable C rating would be ideal. Some good batteries available locally are the Gens Ace Bash Series (yellow connectors) and the CNHL Racing Series. For better handling and lower gearing you would need to replace the fixed centre 34T spool / spur with a complete Infraction / Felony centre diff, part number ARA7615V2. With this mod, you can switch to gearing lower than 27T. I recommend between 21T and 25T. Tires I recommend the GRP S1, S3 or S5. Wear and slip, S1 is extra soft, more grip more wear, S3 is soft, medium grip medium wear, S5 is medium, less grip less wear. GRP S5 will last more than the Hoons. If you prefer the black Hoons look, keep in mind Hoons colours. White Hoons are soft and will grip and wear quickly, Hoons silver are medium and will slip more and wear slowly. I alternated through both the Hoons and GRPs multiple times and I prefer GRP overall.
The Limitless, Infraction, Felony series is quite literally a blast so if you’re into that sort of thing, go for it, you will not regret it. Just research and ask before buying stuff as it can get rather costly to setup. At the end of the day, there is nothing like it and you will have people jaw dropping on you which is sort of funny in a way.
A word of caution to everyone out there reading this. Keep in mind where you’re going to run your setup, in Malta there isn’t much space for such speed runs in isolation. Be aware that these RCs can weigh around 15KG and run at around 160KMPH, if you hit anyone it will not be a minor injury, you can literally kill someone. If you hit a parked car, you can cause serious damages. Keep in mind that at any point, something can go wrong and you may lose control. I recommend keeping a small fire extinguisher handy as well, I had 2 builds go up in flames and nothing to extinguish the fire with. For all the money you spend, a small fire extinguisher can cost something like 15 euro from the supermarket or a fire extinguisher retailer.