Base Unit - is basically the body of the scooter. Generally it consists of a steel, aluminum, or composite frame with a fiberglass or composite floor to support the feet and batteries. Some scooter bases also include a shroud over the front wheel and drive head, creating a dashboard for the unit. The base also includes the wheels and the drive train. In some scooters, the seat post is also part of the base. The base unit is the primary determinant of whether the scooter is designed for indoor or outdoor use, the vehicle's maneuverability, the size of its wheelbase, its ground clearance, its turning radius, and its overall dimensions.
A scooter should not tip easily during sharp turns or on inclines such as curb cuts (if the scooter is designed for outdoor use). Anti-tip wheels should be included as part of the frame to help support and stabilize the scooter. On front-wheel drive units, anti-tips are often located laterally just behind the front wheels because they generally lack the power for steep inclines. Because most rear-wheel drive scooters are intended to negotiate more rugged terrain, they are usually equipped with rear anti-tips to support the scooter on hills. Side anti-tip wheels are sometimes offered as options. It should be noted that lateral anti-tippers may cause difficulties on curb cuts and ramps.
On some scooters, the base unit may be comprised of modular units or may otherwise be disassembled for transport and storage. These same features may also allow the scooter to be converted from three- to four-wheeled models and/or from indoor to outdoor use.
Drive Train, Brakes, and Power System - The drive train is an integral part of the base unit and provides either front- or rear- wheel drive for the scooter. Front-wheel drive is usually found on smaller scooters designed primarily to be used indoors or outdoors on flat, paved surfaces. The motor of the front-wheel drive scooter is located over the front wheel and drives only that wheel. Because of the motor and wheel configuration, front-wheel drive scooters are usually direct-drive units, eliminating chains and belts. However, this also means that the front wheel pulls the weight of the unit and the rider. Consequently, these types of scooters have a lesser capacity to move their load than do rear-wheel drive models, and are therefore less capable of handling hills, curb cuts, and other outdoor terrain. This is compounded by the fact that front-wheel drive models generally have smaller motors, causing them to have a shorter range, less speed and power, and a smaller rider weight capacity.
Rear-wheel drive scooters are powered by motors connected to the rear axle, either via a chain, a belt, a transaxle unit, or some combination. Because the scooter is driven by the rear wheels, they push the combined weight of the unit and the rider, rather than pull it. The combined weight of the rider, the motor, and the batteries over the rear wheels, generally create better traction than that usually provided by front-wheel drive models. The increased traction combined with the more powerful motors used on rear-wheel drive scooters results in better climbing ability. The units also have a greater maximum speed, a longer travelling range between battery charges, and a larger rider weight capacity. These scooters have a wider wheel base and a greater overall length, making them less maneuverable and rendering some models unsuitable for indoor use. They may also be too large for van or bus lifts.
Brakes - most rear-wheel drive scooters utilize an electronic or electro-mechanical dynamic, regenerative braking system. This type of braking system works in tandem with the motor, first to slow and then stop the vehicle when the pressure is released on the thumb levers or the controls are otherwise disengaged. When the scooter is not being powered forward or in reverse, the brakes are engaged, thus preventing the scooter from moving. During the application of the brakes, excess power from the motor is channeled to the batteries, providing recharging. Because the brakes are engaged when the scooter is being actively powered, most scooters with this braking system are equipped with a clutch on the motor or another release lever to manually disengage the brakes to allow the scooter to be pushed in case of emergency.
Some scooters also use disc brakes or disc brakes in combination with the braking system discussed above. Some scooters--usually front-wheel drive models--are not equipped with electronic or electro-mechanical brakes. In the absence of a brake system, a manual parking brake applied by lever to a rear wheel is provided. Manual parking brakes may also be offered either as optional or standard features on other scooters to provide extra braking on hills and inclines.
Batteries - most scooters utilize 12- or 24-volt motors and electrical systems generally with one or two 12-volt batteries to power the drive train and controls. Twelve-volt systems are most frequently found on front-wheel drive scooters, and usually require one 12-volt battery, although two six-volt batteries are sometime used. Some manufacturers offer add-on units for 12-volt systems which allow them to utilize two batteries to extend the scooter's range between charges, although speed and power are not affected. Rear-wheel drive systems generally require two twelve-volt batteries to power 24-volt systems.
These batteries are "deep cycle" batteries intended for wheelchairs and scooters and generally last between 12 and 18 months, although with conservation and regular charging, longer life may be achieved. Deep cycle batteries are designed to provide a steady supply of power and be discharged and recharged on a regular basis. Automotive and marine batteries, on the other hand, are designed to be starter batteries, providing short bursts of power only. Consequently, marine and automotive batteries should never be substituted for deep cycle batteries.
There are three basic types available for use with scooters: Lead acid (or wet cell) batteries, sealed lead-acid batteries, and gel cell batteries. Lead acid batteries are the least expensive of the three types, but they also require the most maintenance. In addition to regular charging, electrolyte and water levels must be checked regularly, with water added frequently to maintain appropriate levels. Because these batteries are not sealed, there is danger of acid spillage and explosion if the batteries are not handled properly. Despite these potential problems, lead-acid batteries provide the benefits of a two- to six-month longer battery life and up to a ten percent greater running time than other battery types. Sealed lead acid batteries are maintenance-free versions of these batteries. Because they are sealed in cases, it is unnecessary to add water and the danger of acid spillage is reduced or eliminated. The cases are vented to prevent gas build-up that can lead to an explosion. Finally, gel cell batteries are the most commonly used battery type on scooters. They are sealed in their cases and require no maintenance other than regular charging. Gel cells are the safest of the battery types, with no danger of spillage and limited risk of explosion. However, gel cells are more expensive, and may have a somewhat shorter life than other battery types.
Wheels and Tires - The size of the wheels and tires on a scooter have a direct effect on the scooter's ability to surmount obstacles and its stability. Scooters are generally equipped with six-, eight-, or ten-inch wheels, although other sizes may also be used. Some models use the same size wheels both front and rear, while others may have smaller wheels in front and larger rear wheels. Smaller wheels are generally found on front-wheel drive scooters intended for indoor use. As a rule, the intended use of the scooter should dictate the size of the wheels and tires. The larger the wheels, the more stable the unit. Similarly the larger and wider the tires, the greater the unit's traction and capacity to manage such obstacles as curb cuts and uneven outdoor terrain.
Several types of tires are available for scooters. Manufacturers generally offer a specific tire as standard equipment, with others available as extra-cost options. Pneumatic tires include air-filled tubes and are similar to those found on automobiles. Air pressure should be checked regularly to maintain proper levels, and tires may need to be replaced if punctured. The addition of an anti-flat compound before inflation reduces the risk of tires going flat. They provide good shock absorption when properly inflated. Foam filled tires are similar to pneumatic tires, but include foam inserts rather than air-filled tubes. These tires cannot be deflated and, therefore, require less maintenance. They may be more expensive than pneumatic tires and may not offer a consistently comfortable ride. The least expensive tire option is the solid rubber tire. These tires require the least maintenance, but provide minimal shock absorption and are intended primarily for indoor use.
Seating - The most common seat found on scooters is a chair-style seat similar to those found on boats. The basic seat is molded hard plastic or fiberglass, but most manufacturers offer a padded-seat option, usually with a choice of vinyl or fabric upholstery. Vinyl upholstery is frequently less expensive, but because it is a slipperier surface, it may not be the best choice for those whose disability makes it difficult to maintain position or balance.
Armrests - are another consideration in seating. Some scooters offer armrests only as an option; others offer fixed armrests as standard with flip-up armrests available.
Tiller - The control and steering mechanism for the scooter, usually containing the controls to drive the scooter forward or in reverse, as well as steering the front wheel or wheels. Most scooters offer one type of standard tiller with other controllers available as options. Possibilities include thumb levers, loop handles, joysticks, and others. Thumb levers are the most common controls, allowing the user to keep both hands on the handle bars while using the left thumb to power the scooter in reverse and the right to power the scooter forward. The amount of pressure applied to the lever will determine the speed of the vehicle (unless it is equipped with a proportional speed control). Consequently, a fair amount of hand control is necessary for safe operation. Finger control levers or a joystick may be alternatives. Some manufacturers may also be able to adapt controls to user requirements at extra cost.
The tiller itself is often an upright post attached to the front wheel. However, it is also becoming common to find flexible, accordion-style tillers which can be adjusted for height and/or position. This not only enables the user to place the tiller in the most comfortable position while driving, but also allows it to be moved up and out of the way during transfers. In the absence of a dashboard or shroud over the front wheel, a control box with the key lock, battery level indicator, speed controller, and other features may be affixed to the tiller handlebars.
Since a joystick controls both speed and direction, scooters equipped with them generally do not have the post-and-handlebar tiller; the joystick is usually attached to an armrest or to an armrest extension, with a choice of right or left mounting. While this frees the space in front of the user and may accommodate easier transitions for some, the lack of handlebars may make transfers more difficult for others.
Other Accessories - In addition to the standard features common to all scooters discussed above, manufacturers offer a variety of standard features and optional accessories. Most scooters are equipped with a key lock for turning the scooter on and off, thus conserving battery life and preventing unauthorized use; a battery-level indicator and a proportional speed controller to limit maximum speed.
A wide range of accessories also are offered on most scooters, such as crutch and cane holders, oxygen carriers, front and rear baskets, trailers, headlights, tail lights, horns, canopies, and others. Some manufacturers even offer sidecars to allow an additional passenger. As when purchasing a car, options and additional features increase the base cost of the unit, but accessories should be evaluated in light of their capacity to create a mobility aid which provides maximum user independence. At the same time, it should be kept in mind that some options may decrease battery life, maneuverability, and/or travel range.