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Selecting the right pushrod
Wing servo pushrods:
I prefer to use the lengths of piano wire which have been threaded at one end to take a metal clevice. Cut these to length and at the control surface end either solder a threaded adapter to take a second clevice, create a z bend or use a ball and socket connector (my preferred choice)
Making a ball socket joint.
Most model store sell the plastic ball and socket joints. However the balls are usually"bolt in place" i.e. have nothing more than a hole to take a bolt. With the length of wire that was cut off from the pushrod solder this into the hole on the ball. Be careful with the soldering to keep the ball "clean" from solder. Trim and file (or wet and dry) the wire protruding from the end of the ball, so that the socket can be fitted into place. Now cut the wire to length and epoxy or ca into the control surface. Now you have a well fitting clevice at the servo and a easy removable fixed connection at the control surface.
Make sure you choose the right pushrod for your application. Be careful of running conducting pushrods (including carbon rods) down the length of the fuselage particularly if you intend to run the Rx aerial down the fuz. This may cause interference problems or radio glitches. In the past when I have used carbon pushrods I have insulated the rods using tape ensuring that they are not rubbing against each other, and also run the aerial down the outside of the fuselage.
Fuselage Pushrods:
If you are building a HLG, it is possible to use a smaller pushrods. Planes where a lot of load will be exerted on the elevator linkage, such as an F3B model, slope racer, F3J or duration plane, a strong choice is a must.
Music Wire:
Music wire is nice and stiff, but must have a housing
with no harsh curves to prevent binding. When installing,
it is best to tack the housing at one end and then let
the housing hang down the boom so it follows a naturally
straight or slightly arched path. The only disadvantage
with the music wire pushrods is that the diameter of the
music wire must be smaller than the id of the housing
(also to prevent binding) which builds-in an inherent
amount of slop. Removing this slop is difficult since
it is caused by the wire flexing in the "free space"
within the housing.
It is generally so little, that you may not want to worry
about it.
If you want to minimize it, you can make the housing "porpoise" it's way down the fuselage. The arcs must be shallow and you must lightly tack and test the movement before securely bonding things in place. You must walk the edge of too tight and too loose.
Carbon Rods
For some models, like V-tails, a 5mm carbon tube that
is "free floating" in the fuselage works excellent.
Generally one or two guides of an aluminum tube along
the way (or a bulkhead with slightly oversized holes in
it) will keep the pushrod from flexing and causing a "soft"
linkage. To attach your clevises at either end, I have
used hot glue to fix threaded piano wire links into the
centre of the carbon rods. Then if you need to adjust
the lengths all you need to do is get out the heat gun!
Running your aerial in your model
Never have your aerial folded back on itself, also never change the length of your aerial. The best placement of an aerial is half lengthwise and the rest hanging down so that when the model is coming at or going awy from you these is always a length of aerial that is receiving. This is especially true of large gliders that can be very far from you. However sometime this not always practical.
If you have any metal pushrods of carbon rods running
down the fus or even a corbon fus, then the aerial should
be run down the outside of the fus.
Making your linkages strong and slop free
Creating a linkage that's both free from slop and free from binding can be a challenge. Yet, the investment of time necessary to make a linkage perfect is worth it in terms of the handling and safety of your model.
Every R/C sailplane has linkages, some long and some
short, they can all have slop in them which at times can
adversely affect the precision of your centering or stick
input or worse, can cause high speed flutter and possibly
catastrophic failure.
Removing slop from threaded clevises and z-bends
A trick for taking slop out of clevises: seems crazy, but works perfect. Put thick CA right where the clevis meets the horn, kick it, let it sit for a minute and then manually deflect the surface thereby breaking the glue joint free. What you end-up with is a perfectly solid bearing of CA that removes all the slop from your clevis.
The same trick can be used on metal threaded clevises.
First, be sure the clevis is where it needs to be, then
simply put a small drop of thick CA at the joint where
the threads leave the clevis and kick it.
You can also use the lock nuts that come with the clevis
to prevent the thread slop, but you need to periodically
tighten them. If you rarely need to adjust the clevis
or if it's out of reach, just CA it!
This method also works on Z-bends, but you have to be
very careful that you don't over glue it.
Just a small drop right where the rod passes through the
horn or servo arm (or both) does the trick. On all of
these CA applications, you may need to repeat the process
if the CA gets brittle and crumbles out of position.
Alternatively:
The method that has always worked for me, especially with
metal clevises to plastic horns, is this: usually you
will find that the clevis pin is just too big to go through
the hole in a new plastic horn. So place the pin in the
hole in the horn as best you can ( it will be under tension
), then simply toutch your hot soldering iron onto the
fixed end of the pin. The pin will get hot & melt
its way through the horn. Take the iron off the pin as
soon as it starts to move. 'Violla' slop free, free moving
link.
Ray Huxley.
Safety tip
Always inspect your linkages after a hard landing. Do
BOTH a physical and visual inspection. Look closely to
see if anything looks cracked or bent. Then, with the
radio on, grab the surface in question (like the stab)
and try to deflect it.
If it doesn't move, you're good. If it appears soft, sight
down the housing as you apply pressure and see if it bows
away from the surface.
If it does, reattach it immediately!
How to debond CA glue:
Super glued your servos into the wing, and cant get them
out? Here's how.
Use your girl friends nail polish remover; apply liberally
for a few minutes, and watch the super glue gradually
soften, enabling you to ease out the servo without damage.
Excellent results were achieved using "Nail Overlay
Polish Remover", and its main ingredients are acetone,
and castor oil. (take care if you have foam wings as acetone
may also dissolve foam!)
Thanks to John Sault for supplying this tip.
Building
Straight: The secret to true flight performance
Have you noticed how some people can launch a new model
and it will fly great, with very little trim corrections?
The secret is that these pilots make a series of adjustments
and checks of their models BEFORE their first flights.
Build it straight and it will fly right.
If you're a relatively new model builder, "pretty
close" may seem fine when you're up late at night
and frustrated because you can't quite get the parts to
fit the way they're supposed to.
In those times, it's better to stop and get a fresh look
at the problem in the next building session.
Square alignment of wings to tail; a straight fuselage;
and the freedom from warps in the flying surfaces makes
a significant difference in the performance your glider
will yield. So, how do you insure the model is built straight?
Here are 5 things you should do:
One
Take your time. Sight and check each axis twice before
gluing. In short "Measure Twice, Glue Once."
Take your time. Sight and check each axis twice before
gluing. In short "Measure Twice, Glue Once."
Two
Make sure your building board is straight and flat.
Three
Make sure molded or pre-built parts are not warped. If
you sight down a glass fuse and find a bow or twist, use
a heat gun (carefully!) or very hot water (not boiling--150
degrees max) to soften it and carefully move it back to
true.
Having a second pair of hands makes this much easier.
Four
Make sure that wings and tail are square.
There are two methods: careful measurement, and "eyeballing"
it. I prefer to do a little of both. One thing that is
difficult to measure accurately is the squareness of the
stab to the fin because both surfaces generally have some
taper to them.
Make sure that wings and tail are square.
There are two methods: careful measurement, and "eyeballing"
it. I prefer to do a little of both. One thing that is
difficult to measure accurately is the squareness of the
stab to the fin because both surfaces generally have some
taper to them.
I find its usually easier to check the stab alignment
looking from the back of the model, standing a little
way back.
Five
The "careful measurement" method to ensure that
the wing is square to the tail is also good to perform.
First, be sure the fuselage is straight.
Then, square the stab to the fuse by mounting it and measuring
from each tip of the stab trailing edge to the center
of the nose. The distance should be the same. A piece
of thread fastened to the nose and pulled taut to the
stabs works as well or better than a yardstick and is
easier to work with.
The "careful measurement" method to ensure that
the wing is square to the tail is also good to perform.
First, be sure the fuselage is straight.
Then, square the stab to the fuse by mounting it and measuring
from each tip of the stab trailing edge to the center
of the nose. The distance should be the same. A piece
of thread fastened to the nose and pulled taut to the
stabs works as well or better than a yardstick and is
easier to work with.
Once you are satisfied that the stab is square, remove
it and mount the wings. Use a similar method as described
above measuring from the trailing edge of the wing tips
(in the same exact spot on both sides) to the tail-end
of the fuse, or the nose, or both. Measuring to the tail
will give you a more accurate reading.
You also want the wing and stab on the same plane laterally.
An easy way to accomplish this is to site along the stab
by standing directly behind the fuselage of the model.
Hold the model far enough away from you so you can see
how the stab aligns along the top of the wing. You can
do this with a V-tail by sighting across the tips of the
tail. With a little practice you will be able to detect
any differences and correct them.
The most important thing to remember about building a straight model is to take your time and make sure you get it right the first time. Before I make any final installation, I make sure that all flying surfaces are true to the others: vertical stab is perpendicular to horizontal stab; horizontal stab is level with wings; wings are perpendicular to fuse; and wing tip to stab tip is equidistant for each side. Only after all these surfaces are aligned do I make a permanent glue joint.
A straight plane takes more time to build but your patience
will be rewarded with true and accurate flight.
Don't forget to check the center of gravity (c/g) of
the model. You usually can't go wrong by putting the c/g
of your plane exactly as specified in the instructions.
Then, after flying the model, you can GRADUALLY adjust
the c/g backward or forward by shifting components or
adding weights to suit your flying style. If the horizontal
stab is on the same level as the wing and your model still
won't fly level, adjusting the c/g may help.
If the plane climbs, shift the weight towards the nose.
If the plane dives, shift the weight towards the tail.
If the plane doesn't penetrate the wind well, gradually
add weight right on the c/g until it does.
Often neglected is the lateral balance of the model. Sometimes
one side of the wing will be heavier than the other. This
can cause uneven loops, even when everything if built
straight. Balance the model from the exact center of the
fuse by the nose and tail to see if one wing constantly
dips lower than the other. The slightest weight added
to the wing tip, like a strip of strapping tape, may be
enough to obtain lateral balance.
You may want to do this measurement before permanently
attaching the ailerons. One aileron may weigh more than
the other.
By shifting aileron sides you may be able to offset the
effect of the wings not being evenly balanced without
having to add weight.
Last, but not least, make sure your control linkages
are slop-free. I like to put an aileron servo in each
wing for more positive control.
With linkages as short and rigid as possible, you will
have better control of your model.
This is especially true of the faster slope soarers.
Try these techniques on your next model.
You may be pleasantly surprised at the slope!
For the longest battery life and best reliability, choose
a good charger. AstroFlight and Hitec both make high quality
chargers that can charge up to 36 and 24 cells respectively
using a 12 VDC power source such as an automobile battery.
These chargers are the peak detection type, necessary
for the proper charging of NiCad batteries. Peak detection
chargers are necessary because during the first 70% of
the charge cycle a NiCad battery absorbs almost all of
the energy. After this point the battery cells start to
generate gases and the temperatures rise.
Excess heat, due to overcharging, is the greatest enemy
to battery longevity.
A peak detection charger will sense when the battery is
at maximum charge and then stop charging before excess
temperatures are reached. For long life do not recharge
a battery while it is still hot from a recent discharge.
Most peak detection chargers available at hobby suppliers
only detect peak voltage, not heat.
A test carried out by GTE Government Systems on NiCad
batteries used in radios by the Navy showed that when
these batteries were simply charged and used, 45% had
to be replaced within one year. When the NiCads were exercised
by bringing their voltage down to one volt per cell once
a month,the annual replacement rate dropped to 15%.
The typical sports flying we do several times a month
is usually sufficient exercise for our NiCads even if
the voltage doesn't drop down to one volt per cell. Running
down NiCads until the prop is barely turning after each
flight is not a good idea. It can cause battery overheating,
cell reversal, and armature warping of the motor.
When cells were reconditioned by using a slow, deep discharge,
bringing each cells voltage down to 0.6 volts, with careful
control to prevent cell reversal, the annual replacement
rate dropped to just 5%. Reconditioning is typically done
with cells that have not been exercised for several months.
Matched cells, especially when used in high current applications,
are a good investment. Mismatched cells are sometimes
found in new sport battery packs, as well as those that
have aged.
The reason for unevenly matched cells is poor quality
control from the manufacturer and inadequate matching
when assembling the batteries. If not too far off, cells
in a new pack can adapt to each other with some initial
slow charging at about 1 amp current.
In an unmatched pack, weak cells hold less capacity and
are discharged quicker than stronger cells. This imbalance
can cause cell reversal in weak cells. Cell reversal is
defined as when the stronger cells of the battery impose
a voltage of reverse polarity across a weaker cell during
deep discharge. In other words the plus side of the cell
will now show a negative voltage and the negative side
a plus voltage making the cell unusable. Also, the weak
cells will reach a full charge first and go into heat
generating overcharge while the stronger cells still accept
a charge and remain cool. An easy way to detect a weak
cell in a pack is to feel if one cell is warmer than the
rest after charging. The weak cells are always at a disadvantage,
making them weaker and contributing still further to their
mismatched condition. There is a strong relationship between
matched cells and the longevity of a battery, especially
at high-load currents.
When weak cells are detected it is best to replace them
with cells that have a closer voltage to the other cells
in the pack. Remove the weak cells and re-wire the pack
temporarily Charge the remaining cells to capacity. Then
charge the replacement cells to full capacity before soldering
them into the pack. That way you can assure that all cells
will have about the same state of charge before putting
the pack into use.
Anyone considering purchasing Nickel-Metal Hydride (NiMH)
batteries should take into account that proper chargers
for these type batteries are more complex than those for
NiCads. Also NiMH cells tend to have more resistance than
NiCad cells.
They are recommended for use in radios and with motors
that do not have a high current draw such as speed 400
or smaller motors. The 3000-mAh Sanyo NiMH cells seem
to work o.k. up to about a 20 Amp discharge rate, but
only have an actual capacity of around 2700 - 2800 mAh.
At higher discharge rates they really heat up and the
current flow decreases, severely effecting motor performance
and eventually battery life.
Manufacturers recommend that to achieve maximum capacity
and service life, NiMH batteries be rapid charged rather
than slow charged. Typically this should take around 2
hours for a fully discharged cell. Also, the amount of
trickle charge needed to maintain full charge is critical.
It MUST BE SET LOWER than for NiCds. A trickle charge
that is acceptable for a NiCd will overcharge the NiMh
battery and cause irreversible damage.
The typical NiCad charger is not designed to provide such
a fully saturated charge to the NiMh battery. Full-charge
detection usually occurs with these chargers immediately
after a given voltage peak is reached. Because of the
absence of a topping charge, NiMH cells will not reach
their maximum capacity. Another area to watch for carefully
with NiMH cells is overcharging, even when they feel cool
to the touch.
If charging a battery for 14 to 16 hours is good, why not charge them for even longer periods of time at lower than the 10% rate? Battery manufacturers are strongly against doing this, warning that it can lead to serious battery failure. A NiCd battery loses about 10% of its capacity in the first 24 hours after being removed from the charger. Thereafter, the self-discharge rate is about 10% per month. Charging a battery at less than the 10% rate is like trying to fill your basin with the drain open.
If we charge a NiCad battery at a rate of 10% of its capacity, shouldn't the charge time be 10 and not 14 - 16 hours? During the first 70% of the charge cycle a NiCad battery absorbs almost all of the energy, thereafter the energy absorption goes way down. The extra 4 to 6 hours used to slow charge receiver batteries gives them the time to absorb the remaining energy for a fully saturated charge. This long charge time and low charge rate are particularly important with radio and receiver batteries, where the cells may not be as well matched as in a motor battery.
You can do a rough calculation of how long your receiver
battery will fly your model in combat. Figure on a current
rate of about 100 mA for each servo and about 25 mA for
your receiver. If your wing uses a 225 mAh receiver battery
you will have approximately 1 hour of flying time (100
+ 100 + 25 = 225). These are numbers for full size servos
in heavy-duty use.
Less strenuous flying will draw less current resulting
in longer flying times.
If slow charging at a rate of 10% of their capacity is
good for transmitter and receiver batteries, why not slow
charge motor batteries? Motor batteries usually have higher
capacities and higher charge rates than transmitter and
receiver batteries.
In fact manufacturers agree that generally it is better
to fast charge these cells.
This is because slow charging of these batteries can cause
a build up of large crystals in the cells causing lower
life and performance. This is also why these batteries
can not be left on trickle charge indefinitely. Many battery
manufacturers include instructions in new battery packs.
You can your cells by using the minimum charging voltage
recommended.
by: Sloerdud Don
NiCad batteries, and to a lesser extent NiMH batteries,
suffer from what's called the "memory effect".
What this means is that if a battery is continually only
partially discharged before re-charging, the battery "forgets"
that it has the capacity to further discharge all the
way down. To illustrate: If you, on a regular basis, fully
charge your battery and then use only 50% of its capacity
before the next recharge, eventually the battery will
become unaware of its extra 50% capacity which has remained
unused. Your battery will remain functional, but only
at 50% of its original capacity. The way to avoid the
dreaded "memory effect" is to fully cycle (fully
charge and then fully discharge) your battery at least
once every two to three weeks. Batteries can be discharged
by unplugging the device's AC adaptor and letting the
device run on the battery until it ceases to function.
This will insure your battery remains healthy.
Your New Battery Isn't Charging. What's the Deal Don?
New batteries are shipped in a discharged condition and
must be charged before use.
I generally recommend an overnight charge (approximately
twelve to Fourteen hours).
Refer to your Transmitter and Receivers batteries user's
manual for charging instructions. Rechargeable batteries
should be cycled - fully charged and then fully discharged
- 2 to 4 times initially to allow them to reach their
full capacity. (Note: it is perfectly normal for a battery
to become warm to the touch during charging and discharging).
New batteries are hard for your charging device to charge; they have never been fully charged and are therefore "unformed". Sometimes your device's charger will stop charging a new battery before it is fully charged. If this happens, simply remove the battery from your device and then re-insert it. The charge cycle should begin again. This may happen several times during your first battery charge. Don't worry; it's perfectly normal.
How Are Batteries Rated? (What Are Volts and Amps?)
There are two ratings on every battery: volts and amp-hours (AH). The AH rating may also be given as milliamp-hours (mAH), which are one-thousandth of an amp-hour (for example, a 1AH battery is 1000mAH). The voltage of the new battery should always match the voltage of your original. Some of our batteries will have higher amp-hour ratings than the original battery found in your device. This is indicative of a longer run-time (higher capacity) and will not cause any incompatibilities.
How Can I Maximize Battery Performance?
The following practices will ensure maximum battery performance:
Breaking In New Batteries - new batteries come in a discharged condition and must be fully charged before use. It is recommended that you fully charge and discharge your new battery two to four times to allow it to reach its maximum rated capacity.
Preventing the Memory Effect - Keep your battery healthy by fully charging and then fully discharging it at least once every two to three weeks. Exceptions to the rule are Li-Ion batteries which do not suffer from the memory effect.
Keep Your Batteries Clean - It's a good idea to clean dirty battery contacts with a cotton swab and alcohol. This helps maintain a good connection between the battery and your devise connection.
Exercise Your Battery - Do not leave your battery
dormant for long periods of time between flying.
I recommend using the battery at least once every two
to three weeks. If a battery has not been used for a long
period of time, perform the new battery break in procedure
described above.
Battery Storage - If you don't plan on using the battery for a month or more, I recommend storing it in a clean, dry, cool place away from heat and metal objects. NiCad, NiMH and Li-Ion batteries will self-discharge during storage; remember to break them in before use. Sealed Lead Acid (SLA) batteries must be kept at full charge during storage. This is usually achieved by using special trickle chargers. If you do not have a trickle charger, do not attempt to store SLA batteries for more than three months.
How Long Do Batteries Last (What is the Life Span of
My New Battery)?
The life of a rechargeable battery operating under normal conditions is generally between 500 to 800 charge-discharge cycles. This translates into one and a half to three years of battery life for the average user. As your rechargeable battery begins to die, you will notice a decline in the running time of the battery. When your two hour battery is only supplying you with an hour's worth of use, it's time for a new one.
Original text and info by Corona
Sloperdudes
