A - Abbreviation - See AMP (AMPERE)
A ARM - 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
AC - Abbreviation - See ALTERNATE CURRENT
ACKERMAN - ACKERMAN ANGLE - Patented in the 1800's by wagon maker Rudolf Ackerman. Ackerman angle refers to the steering geometry that allows the inside front wheel to turn progressively sharper than the outside front wheel. This helps to eliminate the speed scrubbing effect of the outside wheel having to follow a larger turning radius than the inside wheel. Ackerman involves toe and steering block angle, and mostly affects steering response. If you draw an imaginary line from the steering hub pivot point through the point where the steering link attaches to the steering block, the point where the left and right side lines intersect determines the ackerman angle - this intersection is either in front of the rear axle or diff center (more ackerman), centered on the rear axle or diff center (true or zero ackerman), or behind the rear axle or diff center (less ackerman). Ackerman angle is adjusted by moving the steering link mounting position on the steering block in or out - if available. In effect, more ackerman = a more progressive steering response, while less ackerman = faster steering response. The following represents ackerman settings:
- TRUE ACKERMAN - With zero toe, the inside tire and outside tire follow the correct radius during turns. The toe setting remains unchanged throughout the range of motion of the steering tires.
- LESS ACKERMAN - This setting increases steering response, which may cause the model to feel 'twitchy'. Less ackerman is usually only used with on-road models or off-road models that run on high traction surfaces, such as blue groove tracks. With toe out, the outside tire will be toe out during turns. With toe in, the inside tire will be toe in during turns.
- MORE ACKERMAN - During turns, the inside tire will turn progressively sharper than the outside tire. This may cause the model to pull into the inside lane, but creates a smooth steering response that is good for tight and twisty tracks. With toe out, the inside tire will be toe out during turns. With toe in, the outside tire will be toe in during turns.
ACKERMAN LINK - DRAG BAR - DRAG LINK - STEERING PLATE - The plate connecting the bellcranks in a dual bellcrank steering assembly. This plate usually has a series of holes (mounting locations) available to alter the ackerman angle.
ADJACENT CHANNEL REJECTION - Refers to the ability of a receiver to "ignore" (reject) signals broadcast on a level above or below it's current channel of operation.
ADJUSTABLE TRAVEL VOLUME - See END POINT ADJUSTMENT
ADVANCE TIMING (ELECTRIC MOTOR) - See TIMING (MOTOR)
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.
AFTER RUN OIL - This is oil that is placed in the combustion chamber and carb of a nitro engine after the day's run. The oil is formulated to displace moisture, prevent corrosion, and help provide lubrication during the next initial start up. Many people use WD-40 in place of after run oil.
AFTER TOP DEAD CENTER - ATDC - 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 top dead center.
AIR FILTER - An element that is used to clean dirt and debris out of the air before it reaches the carb of a nitro engine. Filters are usually made of a foam or woven paper material, and may include a screen mesh pre filter. Air filters are connected directly to the carb with a filter neck. Most filters can be cleaned and re used, and foam filters require filter oil to work effectively. Always keep your filter clean - nothing robs an engine of power faster than a dirty filter.
AIR FILTER OIL - An oil that is applied to foam filter of a nitro engine to trap fine particles of dust and dirt that the filter can't. To properly 'oil' a filter, thoroughly clean it with soapy water or nitro fuel, let it dry, then knead the oil into it until it is fully saturated, but not wet (placing the filter and oil in a zip lock bag during this process helps). Note that paper element air filters and foam pre filters do not need oiled.
AIR / FUEL RATIO - Refers to the amount of air compared to the amount of fuel that enters a nitro engine. The air/fuel ratio is most commonly referred to as lean (more air) or rich (more fuel). The air/fuel ratio is adjusted using the high and low speed needle valves (as well as the mid range needle valve if available).
AIR INDUCTION HOLE - The opening in the crankcase of a nitro engine located directly below the carb. This passage allows the air/fuel mixture to be drawn from the carb into the crank's induction port.
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 your 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 doesn't hurt to use it with O rings, either.
AIRFOIL - See WING
AL - Abbreviation - See ALUMINUM
ALIGN CONNECTOR - See JST CONNECTOR
ALKALINE - The common, non rechargeable batteries you buy at your local retail store. Thomas Edison created the first alkaline battery in 1901 (it was used to power 'horseless carriages'). In 1949, Lew Urry (of Eveready) invented the alkaline 'can' battery we are familiar with today. AA batteries are most commonly used for RC - they provide 1.2 V per cell. Don't stick these batts on your charger for a refill, bad things may happen. Dispose of them properly, preferably by recycling.
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.
ALTERNATE CURRENT - AC - This is standard household current. AC constantly alternates (changes direction). AC chargers do not require a power supply to be run on household current.
ALUMINUM - AL - An exotic metal that is light yet strong. They make soda cans with the low grade stuff, but aircraft grade aluminum is commonly used in RC applications. The most common grades of aluminum used for RC are 6061 T6 and 7075 T6 - both of which are aircraft grade aluminum.
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.
AM (AMPLITUDE MODULATION) - Refers to the 'broadcast' style of a radio. AM radios change the amplitude (intensity) of the radio waves to transmit data. AM radios are the basic RTR fare - they usually exhibit less distance and a higher rate of glitching than other modulations.
AMP (AMPERE) - A - The definition of ampere is as follows; "The constant current which will produce an attractive force of 2x10 (to the negative seventh power) newton per meter of length between two straight, parallel conductors of infinite length and negligible circular cross section placed one meter apart in a vacuum". Yeah, I don't know what that freakin' means either. For RC, amps are similar to watts, and the more amps a motor or electrical component (such as a servo) draws, the more power it produces - and the quicker it sucks the juice from your batteries. 'Nuff said. Also see AMP DRAW (MOTOR)
AMP DRAW - CURRENT DRAW - (MOTOR) -This refers to the average amps an electric motor will draw from the battery (and through the ESC). This is useful for determining the runtime possible and the amps needed for any given battery pack, or the minimum ESC amp rating needed to safely run that motor. Note that this is not the same as a motor's amp rating, which determines how many amps the motor can draw without overheating. In general, lower turn motors tend to pull more amps than higher turn motors. Actual motor amp draw varies depending on many factors, including but not limited to: driving style, gearing, electrical resistance, the load placed on the motor, or the amount of traction available. The following examples will result in a higher amp draw: a harder driving style (speed runs or constant heavy acceleration), a lower gear ratio (4:1 gearing will draw more amps than 5:1 gearing), less electrical resistance, a higher load on the motor, or higher traction. Some manufacturers may list the max or average amp draw of their motors, but this may still vary between the same motor made by the same manufacturer, and is still affected by all of the above factors. There are many methods for determining the amp draw of a motor, but actually running it in the intended ride tends to yield the most accurate results :
( 1 ) Start with a fully charged (and balanced) battery pack. In this example, we'll use a 4200 mAh 10C pack. Run your ride as intended (driving as hard as you plan to drive, preferably on the same course you plan to run on) until the battery reaches it's cut off point (or dumps). Time the run from start to finish.
( 2 ) Convert the runtime from minutes to seconds. 9 minutes 35 seconds would be 575 seconds (9x60+35=575).
( 3 ) Find your battery pack's milliamp seconds (mAs). a 4200 mAh pack would have 15120 mAs (4.2x3600=15120).
( 4 ) Calculate the amp draw of the motor by dividing the mAs by the seconds - this motor has an amp draw of 26.29 amps (15120/575=26.295).
This all depends on a battery pack with an accurate mAh rating. Battery packs may not be accurately rated by the manufacturer, and will loose mAh according to the number of charge cycles. If you are unsure of the accurate mAh of your pack, just multiply the duration in seconds that it takes to discharge it by the discharge rate, then divide that by 3600 (the number of seconds in an hour). If you discharge a pack at 20 amps and it takes 575 seconds to cut off, the actual mAh is 3.194 (20x575/3600=3.194), which is about 3200 mAh capacity. Discharge the same pack at 26.295 amps (as in the runtime example above), and at 575 seconds to discharge, the actual mAh of the pack is 4.199 (4200 mAh). So . . . what can we do with this info?
- BATTERY - Now you can estimate the runtime of any battery used with that ride/gearing/motor combo. Simply divide the pack's mAs by the motor's amp draw. If you wanted to use a 5300 mAh pack instead of the 4200 mAh pack, you could expect a runtime of about 12 minutes (5.3x3600=19080/26.29=725.75/60=12.09). You can also determine if a battery pack is capable of safely running that ride/gearing/motor combo. For this, you need to know how many amps the battery can safely provide. The example 4200 mAh 10C pack can safely deliver 42 amps (4.2x10=42 amps), which easily covers the 26.29 amp draw of the motor. Even with a 20% difference, this is still at 33.6 amps. If you wanted to use a 2500 mAh 10C pack, your future looks bleak (2.5x10=25 amps).
- ESC AMPS - Once the amp draw of a motor is known, you also know the amp rating of the ESC needed to safely run that motor in that ride with the same gearing. With the above example, a 27 amp ESC would appear to be sufficient (for 26.29 amps) However, when it comes to ESC's (or even batteries), it is best to adjust the amps by 20% to help prevent a meltdown. So, a minimum of a 33 amp ESC would be best (26.29x.30=5.25+26.29=32.15 amps).
ANALOG SERVO - A servo that uses regular servo motor controllers. Once an analog servo reaches the desired position, it 'waits' for further input without applying power to hold the position. To see how an analog servo operates between inputs, simply turn any servo arm with the power off - you will note some resistance, but the servo will turn without holding it's position. Analog servos operate at about 50 'pulses' per second, while digital servos may operate at up to 300 'pulses' per second.
ANODIZED - ANODIZING - A process where parts are electronically coated with a colored metallic oxide similar to chrome. For RC, aluminum and titanium parts are commonly anodized. This helps to protect the part from scrapes, but more importantly, it adds valuable bling factor to your ride.
ANTENNA - ( 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.
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 CAP - The small, black cap that is placed on the end of an antenna tube to help protect the receiver antenna and to keep out dirt and debris.
ANTENNA CLAMP - A part designed to hold the antenna tube in place. It consists of a base that can be mounted nearly anywhere on the model and a threaded collar. The antenna tube is placed into the base and the collar is tightened over it, securing the tube.
ANTENNA TUBE - This may be the most notable visual feature of an RC model. The antenna tube is the long, flexible tube that sticks out of the model body. The receiver antenna is threaded into the tube to elevate it for better reception while helping to protect it. Antenna tubes are available in many colors - choose a color that matches your ride for valuable style points.
ANTI DIVE - See DIVE
ANTI ROLL BAR - See SWAYBAR
ANTI SQUAT - See SQUAT
ANTI SWAYBAR - See SWAYBAR
AR - AVERAGE INTERNAL RESISTANCE (BATTERY LABEL) - Refers to the average internal resistance of the cell during discharge. A lower AR means better efficiency and more current (punch).
ARC (BRUSH) - This happens when the brushes on an electric motor loose contact with the commutator during high RPMs (A.K.A. brush hop). This causes the electrical current to 'jump' from the brushes to the comm, resulting in a loss of power. Truing the comm, installing stiffer brush springs, or aligning the brush hoods may help eliminate arcing. Arcing can also be reduced by installing brushes with a smaller contact area, such as round or octagon brushes.
ARM - Abbreviation - See ARMATURE
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.
ARMATURE BLANK - Refers to a brushed motor's armature before the wire is wound on. This includes the commutator and laminates that make up the core.
ARTICULATION - Refers to the amount of vertical travel an axle or suspension arm has in relation to the chassis. In effect, the more articulation a model has, the bigger obstacles it can overcome without unsettling the chassis. On road models usually have very little articulation, while some rock crawlers may have enough articulation to allow the axles to pivot 90 degrees in relation to the chassis. However, 45* is usually a good starting point for crawlers, since too much articulation may cause the model to feel 'sloppy' and roll over easily while side hilling.
ARTR (ALMOST READY TO RUN) - RACE ROLLER - This is basically a kit that is built at the factory (RTR), except the engine / motor and electronics (including radio gear) are not included. It is also common for ARTRs to not include tires or a body. ARTRs are often 'team spec' rides.
ATDC - Abbreviation - See AFTER TOP DEAD CENTER
ATTITUDE - This refers to the angle of an off road model while in the air during a jump. There are 4 basic attitudes: nose up, level, nose down, and FUBAR. Level is best. If you're nose up, tap the brakes to level out. If you're nose down, get on the throttle to level out. If you're FUBAR, things are going to get ugly.
ATV - Abbreviation for ADJUSTABLE TRAVEL VOLUME - See END POINT ADJUSTMENT
AUTO CYCLE - An option available on some chargers that cycles (discharges, charges, discharges, charges, ect.) the cell or pack a preset or user defined number of times.
AV/V - AVERAGE VOLTAGE (BATTERY LABEL) - An average of the cell's voltage from the beginning of a discharge cycle to the cut off (the cut off is usually 0.90v). The AV/V rating is handy for estimating how the cell or pack will perform throughout it's entire use cycle (A.K.A a race). A higher average voltage is best. Note that a higher cutoff voltage raises the AV/V rating, while a higher discharge rate lowers it.
AWG (AMERICAN WIRING GAUGE) - See GAUGE
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 CARRIER - See HUB
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 motor on that 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 stall is not always a bad thing - it can actually be helpful for the rear axle to stall during a near vertical climbs, this helps prevent the rear wheels from pushing the rig over backwards.
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).