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RC Glossary


New to the RC Hobbies? What does buggy, bulkhead, nitro mean in radio control car hobbies? Check out the glossary for remote control cars below.


  • A Arm --
  • This generally refers to the lower suspension arm of the car, although it can refer to the upper arm also. It is a suspension arm that resembles the letter 'A', being widest at the mounting location on the chassis and narrowest where the hub is mounted. An A arm is usually used on models that use pillow ball hub carriers (knuckles), requiring an upper and lower arm. This may also be referred to as a ""double wishbone suspension"". If your 'A' arm resembles a 'Z', it may be time to replace it.

  • A MAIN --
  • The final race in any given class, consisting of the best of the best as determined by previous mains or qualifiers. Winning the A Main puts you on the podium.

  • ABC --
  • Abbreviation - See ALUMINUM BRASS CHROME

  • ABDC --
  • Abbreviation - See AFTER BOTTOM DEAD CENTER

  • ABN --
  • Abbreviation - See ALUMINUM BRASS NICKEL

  • ABS --
  • A form of plastic that is easy to form but is not crash-resistant. HPI Racing does not use this type of plastic for any kit parts, however some of our 24mm white wheels are made from ABS, which is slightly lighter than the high-impact nylon used in our other wheels.

  • Acceleration --
  • A measure of how quickly a car can accelerate. Affected by items like the weight of the car and its rotating mass.

  • Ackerman --
  • Rudolf Ackerman is a man who worked out a steering system for horse-drawn carts, and we use his name today to describe the angle of the inside tire in relation to the outside tire when the wheels are turned to full ""lock""--the farthest the wheels go to the left or right. Normally, when the front wheels are turned all the way left or right, the inside wheel is at a sharper angle than the outside wheel. If you extend the center line of each front tire to a point where the intersect and measure that angle, that is the Ackerman angle. Ideally, for perfect steering, the Ackerman angle will cross at the center line of the rear axle.
    In a wide turn, the front tires are not turned very far to the right or left, the inside wheel is not steering at a sharper angle than the outside wheel, and the Ackerman angle is not very wide. In a tight turn, the inside wheel is steering at a steeper angle than the outside wheel, and this is what is called the ""Ackerman effect"". A bellcrank steering system approximates a way to copy the Ackerman effect, and is adequate for RC cars because of tire slip, tire sidewall folding and other factors.
    Adjusting the Ackerman angle can be done by changing the length of the center link, also called the Ackerman link that connects the bellcrank steering arms, or changing the mounting location on the steering arms without changing the link length. Most racers won't need to change the Ackerman angle, and actually it is best left to experienced racers who wish to try something new.
    If you wish to learn what changing the Ackerman angle will do, see below:
    The Nitro Racer 2, Pro 2 and Pro 3 use bellcrank steering arms that have two sets of mounting holes (inner and outer) for the Ackerman link. The Pro 2 and Nitro Racer 2 kits use the outer holes, while the Pro 3 uses the inner holes on its new bellcranks. Mounting the Ackerman link to the outer holes will result in a small Ackerman angle. Using the inner holes will increase the Ackerman angle.
    A smaller Ackerman angle (done by lengthening the Ackerman link or using the outer link holes) will give you more aggressive steering into a corner with a possibility of oversteer at the middle of turn, when the most weight is on the outside tires. The RS4 Pro 2 and Nitro RS4 Racer 2 kits use the outer Ackerman link holes in stock form, so they has more aggressive steering than other cars, everything else (damping, tires, suspension) being equal.
    A larger Ackerman angle (achieved by shortening the Ackerman link or using the inner link holes) will give the car more predictable and smoother steering. The new RS4 Pro 3 uses the inner Ackerman link holes, so its steering will be more predictable than the Pro 2.

  • Ackerman Link --
  • The center link of the bellcrank steering system that connects the two steering arms.

  • After Bottom Dead Center --
  • (ABDC) An engine timing term commonly used to pinpoint the timing marks where a port opens or closes, expressed in degrees of crankshaft rotation from the point where the piston is at bottom dead center.

  • Air Dam --
  • An extension of the front bumper that blocks, or dams, too much air from getting under the car and producing lift. Most RC bodies for Touring Cars have air dams built in.

  • Air Leak --
  • This is a major enemy of nitro engines. Air leaks can cause a very inconsistent tune and excessive leaning of the air/fuel mixture (especially at high RPM). If you suddenly discover that the rc engine isn't holding a tune, an air leak is most likely the problem. The usual causes of an air leak are:

    ( 1 ) A poorly fitting fuel tank lid - The seal on most tanks can be adjusted by tightening a screw that applies pressure to the O ring seal. Make sure your lid snaps shut and creates a good seal.
    ( 2 ) Holes or cracks in the fuel tank - This can be tested by emptying and removing the tank, plugging the fuel line, then submerging the tank in water and blowing into the pressure line. If you see bubbles, you have found a leak. Leaks usually develop in fuel tanks at the mounting points (where stress is created) and at the seam where the two halves were joined. Fuel tank leaks may be quickly patched at the track with silicone, JB Weld, or even duct tape, but this is only temporary. In some cases, you may be able to carefully melt the crack closed with a hot soldering iron (make sure you empty and air out the tank first - nitro fuel is flammable). Still, pony up the $10 for a new tank ASAP, just to be safe.
    ( 3 ) Pinholes or tears in the fuel tubing - Fuel tubing is cheap, so if you even suspect that this is the culprit for an air leak, install some new stuff and eliminate any doubt. Also make sure the tubing is securely attached to the pressure fittings.
    ( 4 ) Rotted or cracked O rings in the fuel filter - Inspect the fuel filter O rings and replace them if there are any signs of cracks or damage. While you're there, don't forget to clean the filter, since this is often overlooked.
    ( 5 ) The carb or backplate isn't properly sealed against the block - Check to make sure the carb and backplate are properly sealed, and replace any cracked or damaged O rings and gaskets. Many people use sensor safe RTV silicone instead of gaskets, and it does not hurt to use it with O rings, either.

  • Alligator Clips --
  • You will most likely find these narrow toothed 'pincers' on the end of the power wires on your charger (used to hook the charger up to a power supply or battery), but some chargers may have alligator clips on the battery side as well (great for charging custom built packs, but if you are still sticking these clips into your battery plug, it may be time to invest in some connectors). You may also find alligator clips on your 3rd hand tool, commonly used to securely hold wires while soldering.

  • Aluminum --
  • In general terms, aluminum is a metal that is lighter than steel, but not as strong. It can be machined (cut on a machine) to replace many plastic parts of an RC car, but is not recommended for replacing suspension arms.

  • Aluminum Brass Chrome (ABC) --
  • This is the current standard for 2 stroke RC nitro engines. ABC refers to the materials used in the construction of the piston and sleeve - Aluminum piston and a Brass sleeve plated in Chrome. The aluminum and brass allow the parts to expand and contract as the engine heats up and cools down, while the chrome plating provides a hard, smooth surface on the inner walls of the sleeve, which prevents wear and tear from the piston.

  • Aluminum Brass Nickel (ABN) --
  • Refers to the construction method used for some high end 2 stroke nitro engines. ABN refers to the materials used in the construction of the piston and sleeve - Aluminum piston and a Brass sleeve plated in Nickel. The aluminum and brass allow the parts to expand and contract as the engine heats up and cools down, while the nickel plating provides a hard, smooth surface on the inner walls of the sleeve, which prevents wear and tear from the piston. Nickel tends to be harder than the more traditional chrome plating, which results in parts lasting longer and running smoother.

  • Amplitude Modulation (AM) --
  • Short for, an AM radio in RC is considered a ""budget"" radio, what most newcomers to RC will start out with. Most hobbyists will be fine with an AM radio, but some racers can benefit from FM or PCM radios. An AM radio will have more glitching than these other, more expensive, radios.

  • Angle of Attack (AOA) --
  • Refers to the angle that a surface contacts the air, usually mentioned when talking about spoilers and wings. A higher AOA helps solve oversteer but increases drag and decreases top speed. A lower AOA is used to alleviate understeer and increase top speed.

  • Antenna - (2) Transmitter - TX --
  • This is what sends (transmits) the signal from the radio to the receiver in the model. If a transmitter uses any other modulation than 2.4 GHz, the antenna will be the collapsible metal type, which is replaceable and screws into the radio case. 2.4 GHz antennas are encased (similar to cell phone antennas). The transmitter antenna radiates signals from the side, so pointing the top of the antenna at the model actually reduces reception. Always extend or raise your radio antenna before powering up your model to ensure reception.

  • Antenna íV (1) Receiver - RX --
  • The flexible wire on the receiver that 'captures' signals broadcast by the transmitter. The length of AM and FM antennas is calibrated to the frequency and channel of the radio system, so don't cut or shorten it. Always route the RX antenna as far away from other electronics or batteries as possible to prevent glitching (also try to avoid direct contact with graphite or carbon fiber parts), avoid moving parts that can damage the antenna (such as linkages and gears), and mount the end as high as possible to increase reception. Also, try not to bundle or cross the antenna over itself, as this can also reduce reception. The RX antenna on 2.4 GHz systems is usually stiffer than other systems - this is also known as a 'coaxial antenna'. Always follow the manufacturer's instructions, but coaxial antenna can usually be shortened to within 3 or 4 inches of the receiver.

  • Anti-squat --
  • Refers to the angle of caster on the rear wheels. However, that angle prevents the squatting of the rear suspension, so 'anti-squat' it is. Anti-squat is most effective on acceleration from a stop, when much of the car's weight is forced onto the rear suspension. Lifting the front of the hingepin of the rear arms gives a caster (anti-squat) angle, and helps to transfer the power that makes the car want to do a wheelie into forward motion.

  • Arm Brace --
  • A suspension mount (pivot block) that utilizes captured hingepins.

  • Armature - ARM --
  • The backbone of a brushed electric motor - the coils (wire) are wrapped around the armature, and it spins in the center of the motor can. Armatures consist of the stack (laminations), motor shaft, commutator, and coils (wires). Armatures are commonly created by laminating thin slices of iron together as they are slid onto the motor shaft. Some armatures may be skewed (the 'slices' are rotated slightly as each one is stacked on the shaft) to help reduce cogging, or some armatures may have gaps (missing 'slices') to alter a motor's magnetic field or RPMs. Armatures are commonly balanced for smooth operation, usually with epoxy or by drilling.

  • Axle --
  • Refers to the shaft that transfers power from the diff to the tires, or to the shaft that the tires rotate on (such as a stub axle). A driveshaft (which transfers power from the tranny to the diff) is also commonly referred to as an axle. In many cases, the axle may only refer to the portion of a universal or CV shaft that is supported by the hub (the end that the rim bolts to). The term ""drive axle"" is used to denote an axle that actually transfers power to the tires - such as the rear axle on a pan car. Solid axle models (such as rock crawlers) use an integrated axle and diff housing.

  • Axle Pin - Drive Pin - HEX PIN --
  • A small metal pin that is inserted into a hole in a drive axle just outside of the hub carrier. This holds the axle in the hub and provides a mounting key for the rims. Depending on the model, the rim may be keyed directly to the axle pin, or a wheel hex may be keyed to the pin with the rim keyed to the hex. Either way, the pin allows the rim to be secured to the axle and rotate with it. Keep an eye on your axle pins, they tend to wander off once your rims are removed.

  • Axle Stall --
  • This is a concern for electric, dual motor rock crawlers. Axle stall occurs when the model is attempting a steep climb and the weight of the model exceeds the power of the motor on an axle - causing the axle to 'stall'. Increasing battery voltage or wiring the motors in a series can help eliminate axle stall, as well as installing a smaller pinion or larger spur gear (gearing down).

  • Axle Wobble --
  • Refers to a wobble or shaking of a solid axle (such as those on pan cars). This may be caused by an axle that is mounted at an angle or has worn bushings, bearings, or cam style inserts. However, the most common cause is a bent axle or axles that aren't ground true (such as graphite or carbon fiber axles).

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