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RC Car
Q) How to
choose the right tires?
A) Choosing
the right tire for the track conditions: Slicks should only be used on a Swept
and Prepared track [sprayed with sugar water or another traction additive].
X-pattern Radials are an intermediate type of a tire. They work just about
everywhere. They work on carpet [the groves throw out foam tire dust and Carpet
threads that will polish a slick tire]. They work on sandy or dusty Swept and
Prepared tracks. V-Grove Radials and Super Radials are good for rough or
un-swept tracks. Go for a more aggressive tread pattern when the track
conditions are at their worst.
Q) What is
belted and unbelted tires?
A) Belted
tires VS. Non Belted: This is a personal choice. Belted tires are slightly
harder than non belted due to the stability of the reinforcing belt. They will
last slightly longer and track straight and true. Non Belted tires are slightly
softer and can offer more grip, but they will wear faster than Belted tires. Due
to their slightly softer action Non Belted tires will "Squirm" on the
straights.
Q) What is this
Caster stuff?
A) First
understanding what a Caster is :-
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There are very few adjustments on a model racecar that create so much
confusion as caster. Depending on where you get your information, it
seems that there are very different opinions on the effects of caster
adjustment. For the purpose of this article, I have borrowed
explanations from a variety of sources, and I will try to paint a clear
picture of how caster works.
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What is caster?
Caster is the angle at which the front steering pivots. The primary
purpose of having caster is to have a self-centering steering system.
The caster angle affects on- and off-power steering, since it tilts the
chassis more or less depending on how much caster angle there is.
For the purpose of model racecars, it is generally recommended that you
use a steeper caster angle (more
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vertical) on slippery,
inconsistent and rough surfaces, and use a shallower caster angle (more
laid-back) on smooth, high-grip surfaces.
Camber vs. caster
Camber is all about contact patch – keeping as much tire on the ground
as possible. Camber and caster are related in that caster can afford an
amount of EFFECTIVE CAMBER change when the front wheels are turned in a
corner.
Caster has the effect of progressively leaning the front tires into the
direction of the corner. The more the caster angle is laid-back, the
greater the effective camber change when the wheels are turned. This
happens because the tops of the wheels BOTH TILT towards the inside of
the corner; the wheels “dig in” more, counteracting the centrifugal
forces pushing the car to the outside.
Compare that to the static camber of the wheels, which is adjusted with
the car sitting on a level surface and the wheels pointed straight
ahead. Static camber adjustments primarily affect the outside wheels,
since these are the wheels that bear the majority of the load during
cornering.
Hence, the amount of front camber required to maintain maximum tire
contact largely depends on the amount of caster. A steeper caster angle
requires more camber, while a shallower caster angle requires less
camber.
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It all depends on
your point-of-view…
“More caster increases off-power steering” or, “less caster
increases off-power steering.” Why is there such a difference of
opinion? Is one right and the other wrong? No, they are both right… it
just depends on your point-of-view.
The first statement refers to the steepness of the caster angle;
therefore MORE caster means a more vertical angle. The second statement
refers to the difference between the caster angle and true vertical (see
the figure above); therefore LESS caster also means a more vertical
angle. The same thing said in completely different ways, but both
correct. So the next time your racing buddies are talking about caster,
ask them what they mean by “more” or “less”. Maybe referring to
caster as “steeper” or “shallower” would make more sense.
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Steeper caster (more
vertical)
Increased OFF-power steering INTO a corner.
Why? Imagine that the caster angle is vertical. Now imagine that you
turn the steering; the wheels turn to the side. The steeper the caster
angle, the more that the wheels deflect to the side, giving you more
turn-in into a corner.
Increased suspension efficiency.
Why? The inboard suspension pins are, for the sake of discussion,
parallel the chassis (horizontal) which means that the suspension arms
move up and down vertically. Now, imagine that the caster angle is
vertical, meaning that the top and bottom of the steering “kingpin”
is directly aligned with the motion of the suspension arms. And finally,
acknowledge that shock absorbers are pretty much horizontally aligned
(the top is no further ahead of or behind the bottom), running
perpendicular to the long axis of the car. Since bumps in the racing
surface cause vertical deflections of the wheel, the more vertically
oriented the steering block is, the better the front suspension can
soak-up bumps without binding.
Decreased ON-power steering OUT of a corner.
Why? When you increase the power coming out of a corner, the weight bias
shifts from the front wheels to the rear wheels. The more vertical the
caster angle, the less the effective camber change of the wheels, so
that ONLY the static camber of the outside wheel is affecting how much
the wheels “dig in”. Since the wheels cannot “dig in”
effectively, the reduced weight on the front wheels will cause the front
to lose traction more easily, causing the car to understeer.
Decreased wheel-centering.
Why? Imagine that the caster angle is vertical. Now imagine that you
take hold of the forward edge of a front tire and move it from
side-to-side. The wheel deflects an amount proportional to how much you
move it with your hand. Vertical caster is highly unstable because there
is little in the way of forces to want to keep the wheels pointing
straight ahead.
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Shallower caster
(more laid-back)
Decreased OFF-power steering INTO a corner.
Why? Imagine that the caster angle is so laid-back that it is horizontal
(though this would be impossible). Now imagine that you turn the
steering; the wheels would not turn to the side anymore, but rather the
tops of the wheels would now tilt to the side. The shallower the caster
angle, the less the wheels deflect to the side, giving you less turn-in
into a corner.
Increased ON-power steering OUT of a corner.
Why? The more laid-back the caster angle, the more effective camber you
get when you turn the front wheels. When you increase the power coming
out of a corner, the weight bias shifts from the front of the car to the
rear. Normally this would cause front to lose traction and understeer.
However, since there is more effective camber at more laid-back caster
angles, the “tilted” front wheels are more able to “dig” into
the corner, allowing the car to resist centrifugal force and giving it a
greater amount of control when exiting a corner.
Increased wheel-centering, but decreased straight-line stability.
Why? Imagine that the front wheels of a shopping cart (which have
extremely shallow caster). Push the cart forward, and the front wheels
will always try to center themselves. The shallower the caster angle,
the more the steering is always fighting to get back to center. However
(you knew this was coming, right?), the shallower you make the caster
angle, the greater the amount of force trying to center the wheels.
Eventually the forces become so great that the wheels will start to
shimmy, decreasing straight-line stability.
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Q) Why
won't I get my wheels center no matter how much steering
trim I use?
A) The
steering servo was not centered before the steering
arm as attached. To fix this, remove the steering arm.
Turn on radio and receiver. Set your steering trim to zero
by centering the adjusting knob. You will hear the action
of the servo when you make this adjustment. Turn off
receiver and radio. Reattach the steering arm. Recheck the
toe adjustment of the tires. Your set to run without any
problem.
Q) How
do I know if my Nitro engine is running at the right
temperature?
A) Use
the spit test. Heat is the number one enemy of all
Nitro Vehicles. It is important to keep your Nitro plant
running cool. Two sounds to listen for are a high pitched
whine(too lean)or a gurgling (too rich). Rich means that
there is more gas than air and lean means there is more
air than gas. The spit test consists of running the car
for about two minutes for the engine to get warm. Place a
drop of water on the top of the head. The drop should
evaporate in three to five seconds. If the drop sizzles
when it hits the head your motor is too hot(too lean), run
the motor richer. If the drop does nothing, run the car
for a couple more minutes and try the test again.
Q)
What are After Run Drops?
A)
Regular use of After Run Drops will help protect your
engine. After a day of use, you must put some after
run drops through the motor to prevent the build up of
corrosion, oxidation and fuel residue. To use, pour a few
drops in the carb inlet. A few pulls on the starter will
lubricate the engine's internals. There are few brands
available, so use a name you like. Remember, any brand is
better than no drops at all.
Q.
Hi! I have a Kyosho V One S car and damaged my
chasse and now the car does not drive straight at
all. What shall I do.
A.
It seems that your chasse has been bent hard. If
yes, then better get a new one. If not, then try
to remove the chasse and straighten it and run
again with new setup.
Q.
Hello. What maximum percentage of Nitro should I
use in my .15 RC car to run it faster, but I don't
want to ruin my new engine.
A.
Simple rule of the thumb. More nitro in your fuel
= More faster in speed = More stress on your
engine. So we will recommend you 10-15% nitro for
your new engine, not exceeding 20%. Try to buy
fuel with high oil content (18-25%) which has more
nitro percentage. In this way, you can compensate
not to ruin your engine with more speed.
Q.
The nut holding on my tire is all the way tightened but
the tire still wobbles if I pick up the rear and gas it.
Is it from jumping too high?
A.
Jumping shouldn't cause your wheel to wobble, but it can
cause more wear and tear on other parts that may become
loose. Check your A-Arm mounts and bearings to see if they
are loose or if there is excessive wear on them. They may
need to be tightened or replaced.
Q. My wheels turn sharply, but my car doesn't turn well
at all. Someone told me that I need to adjust my camber.
Can you please explain what camber is and how it works?
A. What your car is doing is called "pushing."
Your wheels are turning like they should, but aren't
getting traction to make thee car turn also. The first
thing you want to do is look from a straight on view at
your front tires. They probably look like this: |
| or like this: \ /
What you want to do is adjust your tie-rods, so the front
wheels look like this from straight on: / \
That is a little exadurated, they shouldn't be quite that
far in, but it makes the point. You can buy a gauge from
RPM that will measure the amount of camber you have. It
should be somewhere between negative .5 and negative 3.5
degrees on each wheel for almost all types of racing and
tracks.
If you would like to see the effects of how camber works,
you can do this little test. Put all electronics, motor,
and battery in your car; as if you were going to drive it.
Look straight on at the front of the car. Turn the wheels
left. Now push down the RIGHT side of the car, as if it
was leaning into a corner. Take notice of how the front
right tire is now flat with the ground. If it isn't, keep
adjusting the tie-rods until it is. This provides maximum
contact area with the ground, which makes more traction.
You will of course, need to slightly adjust the camber
after that, depending how much bite the track has and how
much your car is leaning into the corners.
Q. When I am driving my car, it will shudder on
straight a ways when I get it up to full speed. What is
causing this?
A.
This is a fairly common problem in R/C Racing, and there
are a number of other things that it could be. Try the
things listed below, and see if that fixes the problem.
1st: Check the brushes in your motor. Sometimes
they can get hung up and won't get full contact with the
comm, therefore causing low speeds and/or glitching. If
the brushes look worn out or damaged, replace them.
2nd: Try a friends Speed Control. This is a common
cause of high speed glitches.
3rd: Try a different set of crystals. If yours are
damaged, glitching can occur.
4th: Try a friends receiver and controller. If
something is wrong with these, it could be getting a bad
signal.
Also make sure that the batteries in your controller are
good also! This is often the cause of many problems, and
can easily be overlooked.
If it turns out that your electronics are bad, you can
send them into the company that made it and they will
repair it at a fairly low cost.
Q. Whenever I go to drive my car, the back
wheels are really unbalanced for the first minute of
driving or so. What is causing this and why does it go
away.
A.
My guess would be that you put your car on the shelf (or
table) whenever you aren't driving it. The tires will form
sort of a flat spot on the bottom when they have weight on
them for a long period of time. This is what is causing
the wobbling. After a minute of driving on them, the
wheels go back to normal, and this flat spot will go away.
To prevent this from happening, simply place your car on a
stand so the wheels are elevated when you aren't driving
it.
RC
Airplane
Q.
Hi! Guys. I have a big problem. My airplane does not fly
in level at all. I have checked everything including the
C.G. settings.
A.
Relax, the best way is to remove again, all your servos, receiver, battery pack
and re-fix it again and by doing this, you might discover
things which you might have misplaced it earlier. Also refer properly to your airplane
manual for proper C.G. setting. If still you have a
problem, add a little bit of led weight to the side it
lefts up and still not sorted out, take it to your local
hobby shop to check for any hidden cracks.
Q.
Hi. My name is Anil and can you suggest me a good RC
software to practice my flying lessons at home.Thanks.
A.
Hi Anil. So many RC software are available now days , but
the best so far is Realflight G2 from Great planes. It
comes with a transmitter from Futaba or you can fly with
your own radio by just buying the interface and works with
all radio types of FM, PCM. It also has two excellent
volumes with Jets, electric and sail planes. This will be
your best investment made in RC software if you are buying
one. Also please read the review in our review section.
Software
available in Dubai at Hobby Centre for Dhs 1000 with
futaba transmitter. Volume 1 & 2 is Dhs 200
each.
RC Radio
Q) Why the range test is an
important indicator with PCM?
A) These days, top-level
modellers use PCM. Frankly, I can't think of one who doesn't. The reason is
simple - PCM provides superior control for our sophisticated models. FM is fine
for sport models, but as sophistication grows, so does the need for PCM. While
some mature modellers are still leery of PCM- due to lock-out experiences with
other brands 15-20 years ago - today's PCM equipment can't be beat for keeping
your model under control. That having been said, it's also true that PCM can,
and will, go into "hold" (or fail-safe- a preset user programmed
position) if it does not receive the correct coded signal for a given period of
time. Symbolically, one could think of going into hold as the same thing as
"going over a waterfall". The purpose of the range test is to give us
an indication of "how close we are to going over the waterfall". Good
ground range indicates that the system is strong - it will take considerable
interference from outside sources to cause the model to go into hold. Poor
ground range does not mean the model will crash, only that it is more
susceptible to outside interference - the smallest interference might cause the
system to go into hold. Because models are so tough to come by, personally I
prefer robust ground range!
The System.
Normal technique for range
testing calls for the operator to wiggle the stick, and a helper to determine
whether the system is working or not. Problem is, they aren't connected. The
helper doesn't know what inputs are being provided, so determining when the
signal is lost is murky. To address this issue, the method suggested here uses
the fail safe part of your radio to determine the exact point where the radio
loses range. By programming the elevator to kick "up" when the signal
is lost, it becomes perfectly clear where the exact point is - allowing us to
quantify the results. In a sense, this is a parallel to choosing a .9 volt/cell
cutoff point for battery conditioning.
e-mail
your RC related problems, tips, individual
reviews, comments to
help@dubairchobbies.com
All
e-mails will be responded directly to your e-mail
within 2-3 days time. Only selected articles will
be published here.
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