I originally posted this guide a couple years ago on RCU. Having just recently entered the hobby at that time with no prior experience, I knew first hand how daunting it could be for a novice. There are a lot of terms and jargon that don't make much sense when you have no frame of reference, and I wanted to break them down so even a novice could understand them. This site seems much more accommodating of newcomers than RCU, so hopefully this will get a better reception here than it did there. I've made a few modifications and additions to keep it up-to-date with the current state of RC. If there is something you feel needs to be added or expanded upon, feel free to suggest it.
Types of Vehicles
Monster Trucks (MT)
: I think everybody knows what these are. Huge tires and lifted suspension. They usually aren't the fastest, which is actually good because they don't handle well at high speed. However, excellent ground clearance means they'll run over pretty much anything.
: Open wheeled with a narrow front, usually an exposed motor in back and a wing on top. Buggies have relatively low ground clearance compared to STs and are preferred for dirt-track racing rather than going through grass and brush.
Stadium Truck (ST)
: Basically a buggy with a modified truck body, a wider stance, and modified (usually higher) suspension. STs are sometimes referred to as "truggies", though there are technically a few distinctions between the two. A good "all-around" truck that will handle well on pavement, dirt and gravel, and can still get over grass without too much difficulty.
Short Course Truck (SCT)
: Sometimes called a CORR (Championship Off Road Racing) truck, these are usually a bit narrower than STs and the outer body is widened to cover the wheels. They usually have smaller wheels and a bit less suspension travel and ground clearance then STs. Good for pavement and dirt, but the lower body gives them some trouble with coarse gravel or high grass. The wide body has something of a "parachute effect" when taking jumps, which takes some getting used to.
A fairly new offshoot of the SC truck with an emphasis on proper proportions and cosmetic details. Many DT/DBs are narrower than other vehicles of their scale, sacrificing handling for realism. They usually include touches like spare tires, roll cages and drivers. Not particularly popular with racers, these are more of a "fun" vehicle.
: These are a specialized version of MT with highly
articulated suspension components. They go very slow, but they'll climb over obstacles that nothing else can handle.
: A newer subsection of crawlers focusing on scale realism. These vehicles are modeled as closely as possible on real truck chassis with ladder-frames, leaf spring suspension and realistic drivetrain layouts. This is the category where fastidious model building and RC engineering most closely mesh.
: There are probably several subtle sub-classes that I am unaware of, but in general, a touring car is low slung with very little ground clearance. They are designed to race on asphalt, concrete, or carpet, and cannot handle uneven terrain. Their suspension is stiff with little travel, but they'll drift around corners like nobody's business.
: Also called indy cars, these are road-only vehicles that are set up to look like full-scale race cars with wide, exposed wheels and spoilers.
: Just as with real cars, RC rally cars bridge the gap between on-road race cars and off-road trucks. These cars don't have the ground clearance for really rough terrain, but with the proper tires they'll do well on either paved or dirt tracks. Until recently, most rally cars were simply touring cars with a little more suspension travel. But some manufacturers are now making touring cars based on SC chassis which have much more robust off-road capability (at the expense of on-road prowess).
: Less common these days, pan cars were very simple carpet racing cars. They were stripped down to the bare minimum to keep weight down, and often used unrealistic wedge-shaped bodies for optimum aerodynamics. Foam wheels were also used for weight savings and grip. As the chassis sat barely a quarter of an inch off the ground, they are only really usable on carpet tracks or exceptionally flat and clean pavement.
2 Wheel Drive vs 4 Wheel Drive
: As you would expect, 2WD vehicles only have two powered wheels while 4WD vehicles send power to all four. 2WD cars have the benefit of being simpler and cheaper. Fewer parts means less to break and lower weight. Spinning all 4 wheels takes more effort than just two (not to mention all the extra drivetrain components that link the front and rear), so 2WD cars can get away with using a less powerful motor. 4WD is not without its benefits though. In exchange for the extra weight and cost, you get much better traction on all surfaces. Regardless of the conditions, 4WD will handle and steer better (especially in rough offroad situations).
4WD systems can either be shaft-driven or belt-driven
A metal or plastic shaft connects the spur to the front and rear differentials. This is stronger than a belt, but the torque can cause (minor) handling issues, especially in onroad cars.
Smoother than shaft drive and without the torque-twisting issues, but not as robust and easily fouled by debris. Rarely used for off-road vehicles as dirt on the pulleys will wear down the belt quickly. Belts can also stretch or crack over time and will need to be checked, adjusted, and occasionally replaced.
: In order to get around a turn, the wheels on the right and left sides will have to spin at different speeds. The device that allows this to happen is called a differential. There are a few different types, but to keep things simple, just be aware that all RC cars have one between each pair of powered wheels (so one at the front and one at the back for 4WD), and some also have one in the middle to allow the front wheels and back wheels to spin at different speeds. The tricky thing about differentials is that you don't want them to spin too
easily. If you've ever gotten your car stuck in the snow or mud, you've probably seen one wheel spinning away while the other doesn't move. in RC, we minimize this by using heavy oil or grease in the diffs to make it harder for the gears to spin. This allows the wheels to move at different speeds (needed for cornering) but no so different that all your power ends up going to just one wheel. Exactly how thick the oil/grease should be depends on a lot of factors that I won't get into here.
RC motors are available as either brushed or brushless (BL).
are cheap and get the job done, but they are not as fast as BL. Brushed motors are rated by the number of turns (t) they use. In general, lower turns means higher speed. Most stock motors are in the 17t-30t range, while high performance motors will be 5t-12t. Brushed motors have two power wires. Rebuildable brushed motors are made to easily be disassembled so that the brushes and springs can be replaced when worn out. Most cars come with non-rebuildable motors (often called "cans") which are sealed and must be replaced when they wear down.
are faster and more efficient, which means they'll run longer on a single battery charge. The trade-off used to be that they were more expensive than brushed motors, but now you can get inexpensive brushless kits that will shame all but the highest-end brushed setups. These days, the brushed motor is mostly resigned to cheap, entry-level vehicles. BL motors are rated by KV, with higher ratings equaling higher max RPM. Note that "faster" is not always better, since heavy vehicles actually do better with lower KV rated motors, which don't spin as fast, but have more torque. All BL motors have three power wires. Brushless motors are available as either sensored or sensorless. Sensored motors have additional wires (as shown above) which plug into the ESC. These wires connect to sensors inside the motor and allow the ESC to know exactly what the motor is doing for better control. Sensorless motors are cheaper, but they are not as smooth running as sensored, especially at low speeds. In most cases, you can run a sensored motor in sensorless mode if your ESC does not support sensored, and vice versa.
Electronic Speed Controls (ESC)
ESCs are the electronic devices that control how fast the motor runs - basically a digital throttle. Without getting into too much unnecessary detail, just be aware that a brushed motor requires a brushed ESC and a BL motor requires a BL ESC. Most BL ESCs have extra programmable features, like anti-lock breaking, low-voltage cutoff and signal loss protection. Brushed ESCs are rated by the number of turns (t) they support, while BL ESCs are rated by the amps (A) and voltage (or number of LiPo cells) then can handle.
When people talk about changing gears or gear ratios, they're usually talking about the pinion and spur gear. The pinion is the small gear mounted on the motor itself, and the spur is the big gear that meshes with it. Making the pinion gear bigger or the spur gear smaller will lower the gear ratio, while making the pinion smaller or the spur larger will raise it. A higher gear ratio will give more power, but a lower top speed. A lower ratio will do the opposite. Both gears are rated by the number of teeth they have (t) and the pitch (angle) of the teeth (p). If you want to learn all the specific math behind gearing, I highly recommend you read this post
Suspension tuning really deserves a lengthy post all to itself (in fact, many already exist), but the quick version is this: Shocks absorb up-and-down jolts to the car. The springs on the outside keep the car from slamming into the ground, and the pistons (usually filled with oil) inside the springs dampen the rebound and keep the car from bouncing off the track. Camber
is the vertical angle
of the tires, and toe
is whether they point in or out. Ackermann
is the difference in steering percentage between the front wheels. For a more detailed explanation of how these (and other) factors affect handling, see here
. For the ultimate lesson in every aspect of RC car handling, this site
Tires and Wheels
For all tire types, softer material will give better grip, but will wear out faster. All tires work better with foam inserts, which are included with most tires these days. Tires should be glued to the rims with cyanoacrylate (CA) glue. If you chose tires with an outer diameter that is much larger or smaller than your factory stock tires, you may need to change your gearing to maintain performance. Here are the main types of tires (stolen almost verbatim from this post
: Extremely high wear on hard surfaces, low traction on hard surfaces, gives even traction in all directions, traction greatly reduced on sand. Ideal for dirt or carpet. "Mini-spikes" are a version with fewer, thicker pins that work better on grass.
: Only used on the front wheels of 2-wheel-drive vehicles, good for most off-road conditions, excellent side-to-side traction.
: Medium-low wear on hard surfaces, high side-to-side traction, low traction on acceleration on sand.
: Can be made of rubber or foam, high traction on hard surfaces, gives even traction in all directions, virtually no traction off-road.
: High wear on hard surfaces (especially during acceleration), extremely good traction on sand, can drastically reduce steering on 2WD vehicles
: Similar to slicks, but provide improved traction in wet conditions during acceleration.
: Medium-high wear on hard surfaces, relatively low traction on hard surfaces, gives even traction in all directions, traction less effected by sand.
(not pictured): These are road tires that look like slicks, but are made of hard plastic. They intentionally have very low traction, which makes it easier to break the tires loose and slide around corners.
Different types of wheels (rims) are almost purely an aesthetic choice. As long as you chose a wheel that is sized correctly for your tires and has the proper hub for your car, it's up to you what "style" you want. The only exception is beadlock wheels, which are primarily used on crawlers. These wheels have a pair of rings which are screwed in to the inside and outside of the rim, holding the tire in place (instead of glue).
(Last edited by candre23 : 9.27.12 at 12:43 pm)