Motorhome Basics | FMCA
An alphabetical list of terms related to general motorhoming, the coach electrical system, and motorhome construction. Boondocking, delamination, flat towing, gross combination weight rating, inverter, supplemental braking, 12-volt electrical system, wheelbase ...
12-volt DC: A motorhome’s primary electrical system, in which 12-volt direct current is supplied by onboard batteries to run the lights, stereo, radio, water pump, heater fan and other equipment. Helps to make the motorhome self-contained.
120-volt AC: 120-volt alternating current (same as in homes) supplied by a campground electric hookup or an onboard generator. Often referred to as shore power.
awning: A canvas extension over a window or patio area of an RV.
axle ratio: The number of driveline revolutions necessary to turn an axle one time. With a 4.63 to 1 ratio, the driveline turns 4.63 times for each axle revolution. Higher numbers indicate more torque and slower road speed for a given engine speed. For example, a 4.63 to 1 ratio generates more torque than a 3.90 to 1.
axle weight: The amount of weight carried by a single axle and the amount of weight transmitted to the highway by one axle.
back-up monitoring system: A video camera mounted on the rear of the motorhome and a display monitor in the driver’s compartment. Assists the driver in backing up the motorhome, in watching the traffic flow behind the coach, and in keeping an eye on a towed vehicle.
basement model: A motorhome that has large storage areas along its length, below the living quarters.
boondocking: Camping at a campgrounds or other locations without using modern conveniences of electric, water and sewer hookups. Relying instead on batteries, generator, solar power, stored water. Also known as primitive camping or dry camping.
box: The “house,” or living space, of a type A motorhome.
breakaway system: An emergency device designed to stop the towed vehicle if it were to dislodge from the motorhome. Some of these devices are integrated into the supplemental braking system, while some are sold as accessories.
British thermal unit (Btu): The quantity of heat needed to raise the temperature of one pound of water by one degree Fahrenheit. Air conditioners and furnaces are rated in Btus.
bus conversion: A motorhome built using a bus shell that is converted for recreation vehicle use with features and amenities of the owner's choosing, much like building a custom home. The shell can be new or a former commercially operated bus whose interior is remodeled for motorhome travel.
cab-over bed: A sleeping area that spans the driver’s and passenger’s seats in many type C motorhomes. Can be used for storage when not in use.
caps (front, end, roof): Refers to a family of molded body panels used on many of today’s motorhomes. Often they are constructed of fiberglass, but in some cases caps or other body panel may be composed of ABS, RTM, RIM, or SMC construction. Sometimes they are in upper and lower sections; hence the term "roof cap."
captain’s chairs: The driver’s and passenger’s seats at the front, or cockpit, of a motorhome. The chairs often swivel to face the living area.
chassis: The rectangular steel frame that holds the engine, running gear, and steering and suspension systems and on which the body section of the motorhome is mounted. In type C motorhomes, the chassis includes these components as well as a cab section.
chassis battery: The battery used for starting the motorhome and powering 12-volt DC automotive components of the drivetrain. Also called SLI (starting/lights/ignition) battery.
cockpit: The driver/passenger area in the front of the motorhome, where many of the motorhome's system and instrument controls are located.
cold cranking amperes (cca): The number of amps available to start an engine when the ambient temperature is cold. Used for rating SLI battery capacity.
converter/charger: When the motorhome is connected to an AC power outlet, this electronic device automatically converts 120 volts AC to 12 volts DC to run 12-volt equipment. At the same time, can recharge the 12-volt batteries.
crowned roof: A motorhome roof that is curved, rather than flat. A curved roof has the potential to be stronger and provide for better water runoff.
curb side: The side of the motorhome that is closer to the curb.
curb weight: The weight of the vehicle empty (without payload and driver) but including engine fuel, coolant, engine oil, tools, spare tire, and all other standard equipment. Curb weight is determined without water in the tanks or water heater and with empty LP-gas containers.
delamination: In coach construction, a failure of the adhesive bond line, or of one of the individual components, within a laminated assembly (sidewall, roof, floor, etc.). Modern construction adhesives have reduced this problem.
diesel engine: Powers many long and heavy type A motorhomes and bus conversions. More powerful and durable than gasoline engines. Built tough -- getting 250,000 miles from a diesel without any repairs is normal.
diesel puller: A front-engine diesel-powered motorhome.
diesel pusher: A rear-engine diesel-powered motorhome.
dry camping: Camping without the use of an external power source.
dump station: A facility where holding tanks can be emptied, for a fee or for free. Dump stations are operated at public sites (rest areas, service stations) and at campgrounds throughout the United States.
Filon: The trade name of fiberglass sheet often used in the lamination of RV panels. Manufactured by the Kemlite Company, Inc.
fit and finish: Generally refers to the level of quality in which a motorhome is constructed. A manufacturer who utilizes advanced manufacturing processes will be able to build components to smaller “tolerances”; the result is a higher level of fit and finish. The consumer will notice that everything fits well and has a quality level of finish -- upholstery, cabinets, driveability.
flat towing: Owing a vehicle four wheels down behind a motorhome, with the intent of unhooking the towed vehicle and using for sightseeing or local driving. Only certain vehicles are authorized by auto manufacturers for towing in this manner, and manufacturers' towing procedures must be followed.
FMCA: The Family Motor Coach Association, an international organization for families who own and enjoy the recreational use of motorhomes.
full hookups: A campsite that offers water, sewer, and electricity.
full-timer: A person who travels and lives in a motorhome for most of the year.
galley: The kitchen area of a motorhome.
generator: Supplies 120-volt AC electricity when the motorhome is not plugged in to an external outlet. Most motorhomes, if not already equipped with a generator, have a prewired compartment for one. Because of noise concerns, some campgrounds may prohibit or restrict the hours it may be run. Quieter generators with electric fuel injection are available. Generators are most efficient when used to power high-voltage items.
genset: Abbreviation for generator.
goose egg: The oval membership emblem that FMCA members display on their motorhome. This metal plate enables members to identify one another as they travel, simply by reading the number embossed on the plate and looking it up in FMCA's membership directory or in the "For Members Only" area of FMCA.com. The goose egg increases public awareness of FMCA and promotes friendship among motorhomers. FMCA has issued more than 300,000 membership numbers.
gross axle weight rating (GAWR): According to the chassis manufacturer, the maximum allowable weight of a single-axle assembly as measured where the tires meet the ground. The GAWR is established by considering each of its components (tires, wheels, springs, axle) and rating the axle on its weakest link. The GAWR assumes that the load is equal on each side.
gross combination weight rating (GCWR): The maximum allowable combined weight of the motorhome and attached towed vehicle and everything in and on them, as designated by the manufacturer.
gross vehicle weight rating (GVWR): The weight specified by the chassis manufacturer as the maximum loaded weight of the vehicle (including driver, passengers, liquids, and cargo). Usually posted on the inside wall near the driver's seat.
holding tanks: Tanks that collect black water (toilet waste) and gray water (sink, shower, lavatory). Also, the freshwater tank, which supplies the water used by the RV's occupants. Holding tank capacity is one of the factors in how long a motorhome can be used without hookups.
hookups: Facilities, such as those at a campground, for connecting the motorhome to 120-volt AC power and water and sewer service. Can include cable TV and telephone connections as well.
house battery(ies): The deep-cycle battery(ies) that powers the motorhome’s 12-volt DC electrical system, separate from the chassis. Powers the coach lights, water pump, furnace blower, vent fans, stereo, refrigerator (in 12-volt mode) and other house equipment. The number and rating of house batteries used depends on the motorhome's battery compartment size and the motorhomer's camping tendencies. Motorhomers who frequently use electric hookups in campgrounds may not need to carry as many house batteries.
inverter: A device that converts 12-volt direct current to 120-volt alternating current. Best when used to power smaller, short-duration loads.
laminate: In coach construction, an object (panel) constructed of various flat layers attached (usually bonded) together to act as one homogenous structure; a component in such an assembly. Used for motorhome’s wall, floor and roof assemblies. Laminated construction techniques are often used in higher-end motorhomes.
lauan: A thin plywood constructed of Asian hardwoods. In coach construction, lauan is a popular panel lamination component. It is smooth, strong and relatively stable.
leveling system: Portable or built-in fixtures and associated controls that level the motorhome while parked. Some motorhomes have a 12-volt automatic leveling system using jacks underneath the chassis; the system controls are near the driver’s seat. Owners of earlier models may simply insert wood or plastic blocks underneath the tires to elevate the vehicle. Leveling is one of the first tasks after settling in at a campsite, and can affect refrigerator performance, water drains, and the stability of various items.
liquid weights (pounds per gallon): Water: 8.3; gasoline: 5.6; diesel fuel: 6.8; LP-gas: 4.5
LP-gas: Liquefied petroleum gas, propane, that is used as fuel for the furnace, refrigerator (in 12-volt gas mode), galley range and water heater of a motorhome. Stored in cylinders that can hold up to 50 gallons for large motorhomes.
micro-mini: A small type C motorhome.
motorhome: A self-propelled, completely self-contained vehicle that contains all the conveniences of a home, including cooking, sleeping, and permanent sanitary facilities and in which the driver’s area is accessible in a walking position from the living quarters.
net carrying capacity (NCC), or payload: The maximum weight, including all personal belongings, food, fresh water, LP-gas, tools, dealer-installed accessories and occupants that can be added without exceeding the GVWR. Can be computed by subtracting the empty weight of the vehicle from the GVWR.
OEM: Abbreviation for original equipment manufacturer.
partial hookups: A campsite that offers water and electricity only.
pass-through storage: Exterior compartments that span the full width of the motorhome, accessible from either side.
pilot, co-pilot: The driver and passenger sitting up front.
polystyrene insulation: In coach construction, a material used commonly as a core layer within a laminated panel. It usually is supplied in one of two forms, expanded or extruded. The expanded form is often called “beadboard,”as its structure consists of expanded polystrene beads. It is manufactured using a molding process. Extruded polystrene is manufactured in a linear process, often yielding a product with a "skin" or "shell" surface.
pull-through site (as opposed to back-in site): A camping space that only requires the driver to drive through to access a camping spot, and to just pull forward again when exiting the spot. Back-in sites can be difficult to maneuver a large motorhome into, and they usually require unhitching of vehicles towed four wheels down.
RVIA: Recreation Vehicle Industry Association, a national association representing more than 500 RV manufacturers and component suppliers. An oval RVIA seal affixed to the motorhome indicates that the manufacturer self-certifies compliance with more than 500 safety specifications for electrical, plumbing, heating and fire and life safety established under the American National Standards Institute (ANSI) A119.2 Recreation Vehicle Standard.
shore power: Electricity supplied by an external power source, such as a campground outlet.
slideout: An addition to a type A or C motorhome that extends up to 3½ feet beyond the normal outside walls to expand the living, sleeping, dining or galley areas. Operated when the vehicle is stationary, usually at the touch of a button. Slideouts have become common featuers on many motorhomes. Motorhomes with dual or triple slideouts are widely available.
snowbird: Motorhomers in the northern climate who travel south in winter and return to the North in the spring. Of the 30 million RV enthusiasts in the United States, one in 10 is a snowbird, according to the RVIA. Popular winter destinations include Florida, Arizona, Texas and California.
treet side: The side of the motorhome that is closer to the street.
subfloor: The panels that generally comprise the floor of a motorhome's storage area. Basement floor.
supplemental braking system: A separate functioning brake system designed to control the brakes of the towed vehicle to help slow and/or stop the combination of coach and towed vehicle. A motorhome's braking system is rated for opeation at GVWR -- not GCWR. Therefore, some chassis manufacturers recommend that a separate functional brake system be used when towing a vehicle that exceeds a given weight, as low as 1,000 pounds.
tow bar: An apparatus that connects a car or other towed vehicle to the motorhome and enables that vehicle to be transported with all four wheels on the ground. The tow bar assembly usually consists of two elements: the tow bar (or wishbone portion) and the base plate, which is the part that attaches to the chassis of the car. The base plate is custom made for a particular vehicle and provides a safe point of attachment for the tow bar.
tow dolly: A short, two-wheel trailer coupled to the motorhome for transporting a car or other towed vehicle with two of the vehicle's wheels off the ground. The towed vehicle is driven up the dolly ramps so that two wheels rest on the dolly and the other two wheels arre on the ground. Tow dollies are not applicable for certain rear-wheel-drive vehicles.
towed vehicle: A car, pickup truck, or sport utility vehicle pulled behind the motorhome using a tow bar, tow dolly or trailer. This auxiliary vehicle often is more suitable to drive on backcountry roads or into town than a large motorhome. In addition, the motorhomer does not have to "break camp" to make short trips into town. Also referred to as a dinghy or toad.
trailer: A device that makes it possible to tow a vehicle with all four wheels totally off the ground. This eliminates concerns about transmissions, odometer mileage accumulation and backing into campsites, but loading and unloading can be cumbersome and time-consuming. The motorhome owner also must find a place to store the trailer upon arrival at a destination.
tubular steel roll bar: In coach construction, a steel cab component that can enhance the structural integrity of a cab assembly at the roof level.
type A motorhome: The largest motorized RV, loaded with amenities and equipment that make it ideal for short or long trips, even full-time living. A home on wheels. The living, or house structure is built on a bare, specially made chassis.
type B motorhome: A van conversion built on an automotive van chassis produced by auto manufacturers. The smallest self-contained motorhome, it is a panel-type truck customized to include sleeping, eating and bathroom facilities. Easiest to drive and maneuver. Dropped floors and raised roof are common to increase interior space. Most get better fuel mileage than larger motorhomes. Smaller holding tank and propane tank make dry camping for long periods a challenge.
type C motorhome: A mini-motorhome built on a specially made automotive manufactured van chassis. Offers full living quarters, sleeping, kitchen and bathroom facilities, and conveniences similar to type As but in a more compact unit. Some are built on pickup truck chassis. Many type Cs have a cab-over bunk sleeping area, which extends over the driving section and can be used for storage when not in use. Type Cs are typically easier to drive and park and are more maneuverable than type A motorhomes.
unloaded vehicle weight (UVW): The weight of the vehicle as built at the factory with full fuel, engine oil, and coolants. Does not include cargo, fresh water, LP-gas, occupants, or dealer-installed accessories.
vacuum-laminated: In coach construction, one of several methods of applying pressure to the adhesive system within a lamination, such as a motorhome's walls. Other methods include rotary presses (nip rollers) and flat presses.
walkaround: A short walking tour around the exterior of the motorhome to make sure it is safe and ready for travel.
welded tubular steel: In coach construction, steel that has been rolled into a shape (round, square or rectangular) with a projection welded seam. It is used as a subframe between the chassis and coach bodywork. Usually produced by steel mills and shipped in straight lengths of 20 to 24 feet.
wet weight: The weight of an empty motorhome with the fuel, fresh water, and LP-gas tanks full but with waste water holding tanks empty. For an indication of how much weight that can be added to the vehicle, including cargo and passengers, subtract the wet weight figure from the GVWR.
wheelbase: The distance between the centers of the front and rear wheels on a motorhome. If a motorhome has a tag axle, the wheelbase is measured from the front axle to the center point between the drive and tag axles.
wide-body: A motorhome that is wider than 8 feet.