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Links And Tips Page !!
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"Most of the problems with rechargeable batteries
can be traced to misuse"
HOW
CELLS ARE DAMAGED
Sustained high-current overcharge and cell polarity
reversal (during discharge) are the main killers of
NiCad and NiMH batteries: If a high charge rate is
used, it is essential to terminate charge when the cell
is full. If this is not done, the temperature and
pressure within the cell will rise quickly as the
charging current is dissipated as heat. Both NiCad and
NiMH cells have internal vents which will open to allow
gas to escape and prevent explosion of the cell. In the
case of NiCad, the gas released is oxygen, while a NiMH
cell will vent hydrogen. The gas that is lost can never
be replaced, which means that the lost cell capacity
which results from a severe overcharge is not
recoverable. It is never wise to rely on the cell's vent
as a failsafe, because they often corrode overtime and
can not be assumed to be absolutely reliable. Avoiding
abusive high-current overcharge can only be ensured with
a well-designed charging system that responds to the
signal the battery gives when fully charged. Cell
polarity reversal is a potential problem with any
series-connected string of cells: as the battery is
discharged, the cell that goes down to zero volts first
will continue to have current forced through it by the
other cells. When this occurs, the voltage across the
fully-discharged cell is reversed. A cell that has
current forced through it with a reverse voltage across
it will heat up very quickly and vent gas in a similar
mode to that described for the sustained overcharge,
with the same resultant damage.
LI-ION: HOW CELLS ARE DAMAGED
The biggest problem with the Li-Ion battery is the
ease with which it can be damaged during use: The Li-Ion
battery carries a very large amount of energy in a small
package. Combined with the fact that the internal
resistance is fairly high, you have the potential for a
very dangerous product: If the cell is accidentally
shorted, it could get hot enough to burn a user (and
possibly explode). The makers of Li-Ion cells handle the
explosion threat by designing the case of the cell so
that it will "die with honor", and not explode in
someone's pants pocket if the battery hits their car
keys. More important, the actual battery terminals are
simply never allowed to reach the outside world. The
only manufacturer presently shipping Li-Ion batteries
for consumer products does not sell single cells, only
battery packs. Contained within the pack is circuitry
that isolates the battery power leads from the outside
world if excessive current is sensed, pre-venting
battery damage and protecting the user. Another easy way
to destroy an Li-Ion battery is by discharging it too
far. The Li-Ion cell should never be allowed to drop
below about 2.4V, or an internal chemical reaction will
occur where one of the battery electrodes can oxidize
(corrode) through a process which can not be reversed by
recharging. If this occurs, battery capacity will be
lost (and the cell may be completely destroyed). A
similar process will occur if an Li-Ion cell is charged
to too high of a voltage. If current is continually
forced into a fully charged cell, internal corrosion can
take place which will reduce cell capacity (possibly
completely). For this reason, Li-Ion cells can not be
trickle charged for extended time periods without
cutting off the current when full charge is reached.
Sustained charge currents (even a few µA) can damage the
cell if allowed to run continuously.
AGE-RELATED
FAILURE MODES
NiCad: After a period of
time, the insulator within a NiCad battery often
develops holes which allow the cell to grow crystalline
"shorts" that provide a conduction path between the
positive and negative electrodes of the cell (which
basically shorts out the cell). If this happens, you may
have to blow open this short with a high current pulse
before the cell will again accept charge (a process
sometimes referred to as "zapping"). A leaky NiCad cell
will always have a high self-discharge rate and will
re-grow internal shorts if left on the shelf without
some kind of trickle charge. The annoyance factor of
batteries that go dead quickly often prompts users to
throw away leaky NiCad batteries, even though they may
still be able to give nearly full A-hr capacity during
discharge. NiMH : The NiMH cell (according to the
manufacturers) is not supposed to be prone to developing
internal shorts like a NiCad battery. User feedback (so
far) on NiMH has been good, with no major problems
reported. Li-Ion: The Li-Ion battery got off to a weak
start, as there were many failures in the first
batteries shipped. However, the addition of the internal
protection circuitry inside the battery (and increased
knowledge about the failure modes) has improved this. At
present, there are no known problems which appear
significant enough to prevent Li-Ion from successfully
penetrating the high-end consumer market |
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How to stop an engine??
There are five primary
methods of shutting an engine off. Other people may have slight variations on
these five methods, but the basic concept should be identical. A combustion
cycle in an engine takes place in the following sequence:
-
Crank shaft is turning
-
Vacuum action draws in air
-
Air is mixed with fuel in the
carburetor
-
a hot glow plug ignites mixture
-
exhaust exits the engine
So if we can stop any of these from
taking place, the engine will stop running. Lets take a closer look at what
each one does.
For an engine to continue running from one cycle to the next, its crank shaft
must remain turning. Everything else could be working just fine, but stopping
the crank shaft immediately stops the engine. However, stopping the crank
shaft of a running engine is easier said than done. If the engine is at a low
idle, the crank shaft can be stopped by jamming the tip of your shoe against
the flywheel. In most vehicles this is rather awkward because the only way you
can access the flywheel is to turn the vehicle upside down. Also, if you are
trying to stop a engine that is stuck running wide open, you can forget about
it; It is potentially developing too much power for the crank shaft to be
stopped. So while it is certainly possible to stop an engine this way, it is
mostly not recommended.
Since an engine needs air to run, we can stop the engine by blocking the
carburetor air intake with a finger. Doing so essentially suffocates the
engine, and most engines will stop within half a second or less. This method
is far safer to accomplish than trying to directly stop the crank shaft.
However, since the carburetor intake is covered by the air filter and the
vehicle's body, it is often difficult to pull this off in a hurry. So if you
want your engine stopped quickly, this may not be the ideal way to do it.
To make a combustible mixture, air is mixed with fuel inside the carburetor.
Pinching the fuel line right before it connects to the carburetor deprives the
engine of the needed fuel. And without fuel, the engine will not run. However,
there is usually some fuel that has pooled in the engine crank case and it is
enough to keep the engine going for a short period. As the left over fuel is
burned, the engine runs increasingly leaner. This results in an increase in
the engine RPM, which can be unnerving to someone who is trying to stop the
engine. But soon enough, the engine RPM will quickly drop and then stop
completely. It can take anywhere from 3 to 10 seconds to stop an engine this
way, and it is usually very difficult to access the fuel line in a hurry. So
this method is all but useless in trying to stop an engine in a hurry. What
this method is good for is to prepare the engine for storage. Fuel left over
in the engine after a day of running will attract water, which results in
corrosion. Burning off the excess fuel will reduce the chance of corrosion and
extend engine life.
RC model engines are called glow engines because they need a heat source in
the form of a glow plug to ignite the fuel for each combustion cycle. Removing
the glow plug, therefore, will stop the engine immediately. With that said,
you should block this permanently from your memory. No one ever does its, and
it is the least convenient way to stop an engine. It's simply too impractical.
As air and fuel is burned, the exhaust gas expands and rushes out of the
exhaust port of the engine. With a properly tuned exhaust pipe, the pressure
wave from the previous combustion cycle helps pull the exhaust gas out. When
the exhaust gas leaves the cylinder, it draws in fresh air and fuel to be
burnt for the next combustion cycle. So if we place a finger over the exhaust
tail pipe opening, the pressure inside the tuned pipe will build up,
preventing the exhaust gas from leaving the cylinder in the next combustion
cycle. And if exhaust gas doesn't leave, fresh fuel and air doesn't enter. And
without fresh fuel and air, there is no combustion, and the engine will stop.
This chain of events transpires almost immediately after you cover the tail
pipe opening. It takes at most one full second for every engine I've ran with
to be stopped this way. And since the exhaust tail pipe is easy to access,
this is the ideal method of stopping an engine in a hurry.
I am sure this is a bit more than you needed, but I think understanding the
reasons behind why things work the way they do will help you enjoy the hobby
more.
How To Take A
Corner
This is the perfect
type of corner on which you should practice, A hairpin teaches you throttle
control and steering control, once you have mastered this type of corner and
you can hit it the racing line every time, you can't be far off brilliant!
In order to do that,
when you go into the corner take it as wide as possible, this enables you to
carry more speed through the corner. Aim to cruise instead of breaking it
reduces the chance of rolling since the buggy can slow down at its own rate.
Only brake if you are going way to fast. The acceleration out of the corner is
another important factor that you must get right, to soon and you go wide, to
late and you loose to much speed. the picture above shows what you should be
aiming for. Also you may notice in the picture that the buggy clips the corner
after the apex, this helps the car accelerate away much better due to the
straighter line it has on exiting the corner. A good practice for this type of
corner is a figure of eight
Combined corners such
as S-bends are surprisingly easy to negotiate Depending on the sharpness of
them, the one pictured below is relatively fast, but the principles for taking
them are the same.
You should aim to keep
as tight a line as possible on the bend. Its quite easy for people to overtake
you if you go just a little wide. To do this, pull out to the edge of the
track meaning you have the shallowest possible possible corner to take, also
when you come into the corner don't brake as hard, in fact if its like the
bend above don't break at all just go to half or three quarter throttle. This
gives you plenty of speed through the corner. On the second corner accelerate
a little earlier than you normally would and use the whole width of the track
to get out of the corner.
Cheater
tanks
Looking to stay out
on the track for an extra lap while the rest of the field pits
Adding a couple of
extra-large fuel filters can help.
Fuel filters such as the large
Kyosho units seen here can store a lot of extra fuel.
Be careful, though, if your track
checks tank capacity
Fuel filters and fuel line are part
of the measurement and will be added to the tanks capacity, and that could put
you over the legal limit.
Fuel Bubble !
Engine vibrations can cause fuel in the tank to bubble causing air bubbles to
form inside the fuel line to the engine. This can make the engine stall from
lack of fuel. Loosening the screws that hold the tank can keep the vibrations
down. You can also use old o-rings between the screw and tank to help further
cushion any vibrations.
Battery packs
If you are using pre assembled battery packs, you should change the way they are
assembled. The wrap around the batteries increases the temperature. The tabs
that connect each battery are not very good either. Re-assemble the pack in a
side-by-side configuration with battery bars. You will notice a difference in
battery temperature and overall performance.
Sticky Screws ?
Believe it or not, you can actually magnetize a screw driver! (Some One didn't
listen in class...) This can be done by rubbing a piece of magnate along
your screw driver. However make sure you rube it in only one direction, either
from tip to handle, or the other way around. And be careful not to place the
magnate near electrical equipment! The effect of magnetism will last for about
24 hours.
Pinion to Spur gear distance
To determine the right pressure between the spur gear and pinion gear, take a
piece of paper and run it between where the two gears meet. The paper should
almost be cut through. If the paper is cut through, the mesh is too tight. If it
is hardly dented the mesh is too loose.
Storing your Car
If you are going to put your car away for long periods of time, be sure to put
it on some sort of stand or take off all four wheels of the car. If you don't,
the tyres are very likely to deform under pressure. The tyre does not
deform when running on the ground because the pressure is supported evenly
during the wheel's rotations
Removing Glued Tires From Rims
Never ever rip off the tyre from the rims if they are glued together. This
will leave little bits of rubber on the rims making the rims unusable. Always
remove the tyres by boiling the entire wheel in hot water. Boiling water will
not be hot enough to melt either the rubber or the rim but it will be hot enough
to disable most of the glue. *Caution* Kitchen will smell like burring condom
Wing Reinforcement
I've seen it too many times at races where the wing of a car gets busted off
their mount after being hit etc. Later I found out the screw that attached it to
the body were ripped through the body itself. My solution to this is to add
washers on both the wing and the body and check to see if they are lose after
every race because those spots are barely visible but the effect is FATAL
Quick Repairs no leaks.
At the track, between your races, you have to fix the car in anyway and
disconnect everything. The fuel line is probably the most annoying one. Once you
take the line off the Carb it blows out fuel (which is wasted). Get a spare
screw (not countersunk) so that it covers the tube and insert it in the tube.
This will hold the fuel in and won’t waste or make a mess from the fuel.
Futaba S3003
Servo Ball Bearing Conversion Kit
The conversion kit is a great way to replace standard servos to gain the
friction free performance of ball bearing servos
Features
Not only do ball bearing servos deliver smoother operation, they also offer
better centering and a tighter fit throughout the gear train.
Kit contains enough new case tops and ball bearings for the output shaft to
convert four S3003 servos.
Retail FUTM2355 Servo Ball Bearing Conversion Kit.
Pinion
Gear Replacement Time
 After
running your RC for a while, you will notice your vehicle makes weird noise.
These noises could come from many places, one of which could be from the pinion
gear.. The pinion gear is the gear attached to your motor. The gear on the left
is the one which has been worn out, the teeth on it look like sharks teeth The
gear next to it is new. The Pinion gear is the easiest to wear out because it
spins at the highest RPM of all gears which means it is subject to friction with
other larger gears.
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