Brushless Radio Controlled Cars
News, reviews, tuning and hop-ups
RC Glossary - The A to Z of Radio Control
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Damping -- Damping is a highly variable part of car tuning. It's affected by the
strength of the shock spring (length and thickness of the wire, plus the number of
coils), the size and number of holes in the shock piston, and the viscosity, or weight,
of the oil in the shocks. The spring controls how hard the shock compresses, and
both the piston and the oil control how quickly the spring pushes the shock to its
full length (which can be limited by shock spacers), and so affect the quickness
of the shock's return. Stiffer springs need heavier oil and/or smaller-hole pistons
to control the speed of the rebound, and bumpy tracks need lighter oil so the shocks,
or dampers, can compress and rebound quickly. Softer damping gives more 'stick' on
a particular wheel, but makes the car less responsive because the chassis takes longer
to reset after a turn, and is also more forgiving to drive. Softer damping also reduces
weight transfer at that wheel. Stiffer damping makes handling more responsive, but
reduces traction to a particular wheel which can make the car slippery as the chassis
snaps back into place after a turn. Stiffer damping also increases weight transfer
at that wheel.
Differential-- A system that transfers power equally from a shaft input
to shaft outputs. A differential (or diff) allows the outside wheel of a car going
through a corner to travel farther than the inside wheel, preserving corner speed
and efficiency. There are two main types used in radio control cars:
Ball Differentials
or Gear Differentials. Ball differentials should be initially set to the kit specifications:
the diff should be set so that the pulley is not be able to be turned with two flat
head screwdrivers or Allen wrenches slid through the outdrive. A different type of
differential is the One-Way Diff, which uses expensive one-way bearings to control
wheelspin.
Ball Differential(Ball Diff) -- A differential that uses a series of steel
or carbide-steel ball bearings in a circle, pressed between two metal rings, to provide
the differential action, allowing one wheel to rotate more than another in a turn.
Ball diffs are easier to adjust than gear diffs but are harder to maintain, as they
need checking every day of running and are not recommended for Nitro racers. Normally
a screw on one side controls the tension between the metal rings, which controls
how much the outside wheel in a corner can turn. The looser (to a point) a diff is,
the more traction there is at that end of the car. To start tuning your car, set
the ball diffs to the same tension at each end, and use the diffs only to fine-tune
the car. Do not change the settings of your diffs first.
Gear Differential (Gear Diff) -- A differential that uses a series of gears to provide
the differential action, allowing one wheel to rotate more than another in a turn.
Gear diffs are harder to adjust than gear diffs but are much easier to maintain,
because they must be sealed to keep the grease inside from coming off the gears.
Tuning a gear diff can only be accomplished by changing the weight (viscosity) of
the grease inside the gear diff case. The looser (to a point) a diff is, the more
traction there is at that end of the car. To start tuning your car, set the ball
diffs to the same tension at each end, and use the diffs only to fine-tune the car.
Do not change the settings of your diffs first.
Dogbone -- A part of the drivetrain
that connects the outdrive to the axle. This allows the differential to get its power
to the axle and tires of the car.
Double Wishbone -- A type of suspension design that
uses two wishbone arms (parallel to the ground and each other - one for the main
suspension arm and one for the upper arm) to help maintain a constant tire camber
as the suspension is compressed. Most Rc cars have this type of suspension design,
because, although it is expensive to have on a full-size car because of cost and
space issues, on a miniature car where there is no concern over the space needed
for a driver, it is much easier to make. Older Rc cars used different suspension
technologies that are no longer in use today (at least in Rc) including swing-arm
and trailing arm suspensions.
Downforce -- The effect of air contacting the car body's
sloped surfaces. Downforce is created by the air dam, hood, windshield, roof, spoiler(s)
and wing(s) of the car. More downforce increases drag and slows the car, but raises
the tire temperature, making the car easier to drive. Less downforce raises the top
speed by reducing drag. The car should be set up so that it can drive with minimal
downforce.
Drag -- In car design, drag is the force of air that slows down the car. The lower
the drag of the car (in other words, the more aerodynamically efficient it is), the
faster the car can go while using the same amount of power.
Drag Link-- Another term
for Ackerman link
Draft -- In racing terms, draft is the area directly behind a car
where the air is disturbed and there is very little wind. A real-world example would
be putting your hand outside the window of your car, and moving it behind the side
mirror, then out from behind the mirror. Behind the mirror is the draft.
Drafting
-- In racing terms, this is the act of following the car in front of you close enough
that your car does not have to fight drag. This lessens the load on your engine or
motor, and on a long straight section of the track your car and the car in front
of you can go faster than another car on its own. In R/C racing, this is very rarely
able to be used because of the size of the cars and the maneuverability of the cars,
even on an oval track.
Droop -- The measure of shock droop is the amount of uptravel
the chassis will have if you weigh the car with its full running gear (servo, batteries,
motor, etc.), settle the chassis (press down and release on the chassis), then lift
each end until the tires lift off the ground. The total upward movement of the chassis
at each end is measured as droop.
Dyno -- An expensive piece of computerized equipment
that measures the efficiency of a motor. Can be used to select the right gearing,
but the dyno in this function is normally only used by pan car or oval racers.
