President
Jim Carpenter called the meeting
to order at 1930 hours. The meeting was held at the Mount Vernon Senior Center.
Total Attendance: 15 President Jim Carpenter welcomed club members
Tom Sprague and Barbara Eades to the meeting.
Club Purpose Article II, Club
Constitution: 1. The objective of the organization shall be to
provide instruction, organization, and promotion, operation sites, safety, and
camaraderie for radio controlled model aviation enthusiasts. 2. The membership
shall endeavor to maintain good relations with all local authorities and
citizens wherever they go and to maintain safety and cleanliness at all
operating sites…AND TO HAVE FUN
Minutes: It was moved to
dispense with the reading of the minutes from the meeting of 14 November 2007.
Treasurer Report: The balance for the
period ending 30 November 2007 was given and accepted.
Safety Report: Vice President Larry Linde presented information on the
care and feeding of the batteries used in your RC Systems. Details of the information
can be found on the club website or at http://members.aol.com/davthacker/balancecharging.htm.
Larry also had information from the JR
Manual on “Recommended Power System Guidelines.” These data from JR are
especially relevant to large aircraft or complex models (for example 35% and
larger or jets). See Larry for
details from the JR Instruction Manual.
Old Business: The Emergency Instruction Placard to be posted
at the field has been completed. John Eades passed an example around for the
members to view. These data provide 911 calling instruction in the event of an
accident or emergency need at the field. “Thanks John for a job well done.”
New Business: Club membership dues
for 2008 are now being accepted. In accordance with the Club Operating Manual,
“Dues for renewing members are due on or before the first meeting of the year.
Thereafter all delinquent members will drop (sic) from membership.“ Thank you
for your continuing support to our Club operations, maintenance, and
activities.
Product Report: Ted Hendrickson told
of some ball end hex bits available from J&R Hobby Hardware in both
Standard and Metric sizes.
The
following is from the J&R website;
“ Here is a very nice item and great for getting out socket head cap screws
with ease. They are 2-1/2 inch BALL END HEX BITS with 1/4in shanks! Sold as
sets ONLY! This set consists of STANDARD inch sizes with 9pcs per set. The
standard sizes are: .05, 1/16, 5/64, 3/32, 7/64, 1/8, 9/64, 5/32 & 3/16.
They fit in any 1/4" hand held bit driver or cordless screwdriver (low
torque type). NOT SOLD ELSEWHERE!! - - - WARRANTY AGAINST BREAKAGE “ Visit http://jrhobbyhardware.com
or call 1-866-206-1955 for information.
Tips and Tricks: John Eades has been making decals for his
models using his computer, clip art, decal paper and printer. See John for “how-to” information.
Show and Tell: John Eades brought his “Eaglet” model to
show. He had modified the model by installing a “lifting tail” and converting
it to electric power. The lifting tail changed the aerodynamics such that he
had to go back and adjust the wing and tail incidence angle. After these
changes the “bashed” Eaglet flew pretty well.
Raffle: The door prize was
won by Don Schlumberger and the
fuel by Barbara Eades.
Adjourn: The meeting was
adjourned at approximately 2030 hours for Christmas cookies and coffee..
Submitted,
Don Schlumberger, Secretary
SOME UPCOMING EVENTS
February 8 & 9 - Northwest Model
Hobby Expo.
Evergreen
Fair Grounds Monroe, WA
March 1, - 13th Annual
Model Show and Swap Meet
Spokane
Shock Football Arena, Spokane, WA
Cell
Break In and Balance Charging
for NiMH and NiCad packs in a nutshell.
Dave,
What
exactly is the balance charge you are talking about and how do I do it? Is it
the charge/10 rate for 16 hours that the digipulse will do? By the way, thanks
very much for going out of your way and finding that information, I really
appreciate it. Thanks again for the help and take care.
Will,
USAF.edu
Yes. All cells have a
daily self discharge rate. Each individual cell will have a slightly different
rate. Generally for NiCads this is .5% per day, for NiMH cells its 1% per day.
Note, as the cells age this rate tends to increase so it changes over time.
This is one of the big reasons it becomes too risky to use TX and RX packs
beyond the 3rd year. Be aware also that these rates are only
approximate; they will be slightly different for each individual cell in your
pack. The cells in a new pack will be some weeks or a few months out from the
manufacturer. (With some suppliers they can be over a year old! Yikes!) So,
they've in a sense, been in storage and had time to change levels from each
other. Also, a pack you own that has been in storage (model last flew last
season or few months ago for example) will have a different level of charge in
each cell.
When you charge it, some fill up before
others. When charging at 1/10th Capacity, (C/10) (100mah in the case
of a 1000mah pack/cell) the cells that fill up first won't be damaged while the
remaining cells are filled. Also bear in mind you need to put in about 140% of
an empty cell’s capacity to fill it up. There is some energy losses during slow
charging. So it takes 1400mili amps total (100mah charge rate x 14 hours)
output to fill up a 1000mah hole in a battery pack.
To visualize this cell un-balance condition, lets use our example 4 cell pack,
think of 4 tall drinking glasses all side by side in a row. The first glass is
1/2 full, the second one is 1/3 full, the 3rd one is 1/8 full, the 4th one is
3/4 full. We start to drip water into the glasses at an equal rate of one drop
every 5 seconds into each glass. The 4th one fills up first, then a little
later the 1st one fills, then the 2nd one, then the 3rd cell fills. The pack of
glasses are now all full. However, the 4th cell was 3/4 full at the start of
the charge (water dripping in the glass) so it was overflowing for a long time
while the charger one by one topped off the other 3 cells. If our rate of
charge (speed of the dripping water) is faster than 10% of the capacity of the
cell then damage will occur on the first cell to fill. It will be overfilling
faster than it can accept; this causes it to overheat internally and contributes
to gassing. So, in effect, we’ve done damage to our “best” cell.
A 1000mah cell can take an overcharge rate of 100mah without a problem. It will
warm up when full but the heat being generated is at a rate the cell can
dissipate into the atmosphere. However, if the over charge rate is greater than
100mah (higher than 10% of our 1000mah capacity) a problem is caused. One good
way to damage a battery is to fast charge an old pack that's been in storage
for a long time, or a new pack. It's always best to slow charge these kinds of
NiMH and NiCad packs at 10% for 14-16 hours to avoid this problem and equalize
(or balance) all the cells.
A pack that is in regular use gets some overcharge all the time. You can’t know
exactly the moment it will become full while slow charging. For example: You
fly a day, charge all night, probably some time during the night the pack has
refilled it’s “hole”. It probably Isn’t empty when you put it in charge unless
you crashed and the battery was dead ;-) . We’ll presume you brought the model
home in-tact. When our partially discharged battery fills, the charger (wall
wart you got with system is presumed or Digipulse or DDVC or whatever kind of
slow charger) doesn’t shut off, it just keeps on charging. A cell that is
behind a few Mili-Amps is caught up during this time.
Even when fast charging a pack that’s in
regular use, there is a little bit of an overcharge at the end of the charge
cycle. (Excepting Sirius and Ace fast chargers which are peak predictors an go
into trickle to accomplish same effect.) A peak detect charger is looking for a
drop off in voltage to find the “Full Point” of the pack. It’s voltage is
dropping because it’s heating up, it’s heating up (were you paying attention
earlier?) because it’s full and still under charge.
With all the above in mind, here is what you
do:
Find the
capacity of your battery pack. Lets say it’s 1650mah.
Multiply the Capacity X .10 to arrive at 10% of this number. The answer here is
165mah.
Set your charger to charge at 165mah.
Come back 14 to 16 hours later and the battery is ready to use.
What if I can’t set a charge rate of 165mah?
Another way to skin the same cat is to multiply your capacity (1650) by
1.4
This gives us the 140% we need to put in to fill up a pack. The answer is
2310mah.
Take the answer (2310mah) and divide by the output of your charger, answer is
“Hours” to full charge.
If your using a Digipulse (max setting is 150mah) the answer is 2310/150= 15.4
hours.
If
your using a 100mah wall wart the answer is 2310/100=23.1 hours.
If your using a 50mah wall wart the answer is 2310/50=46.2 hours.
Warning! If your answer is
less than 14 hours then your charging higher than 10% of capacity, the pack
will be damaged! :(
That is balance charging for NiMH and NiCad
battery packs in a nutshell.
Dave Thacker
RadicalRC.com
Glow Plug Problems
Today’s
glow plugs are well made products and they should give you good service.
Although the life of a glow plug is unpredictable, you should reasonably expect
a dozen or more flights out of one. It’s always best to follow the
manufacturer’s specific glow plug recommendations, but if you have an engine
that seems to eat glow plugs, the probability is that it is suffering from one
of the following three causes:
Overheating: A glow plug coil will melt if it gets too
hot. Reasons why this happens vary. Sometimes the combination of running an
engine wide open with a lean setting before you take the glow plug heater off
is too much for the element. Quite often people use a power panel which has a
built-in surge feature, which sometimes results in a momentary over-voltage to
the plug when the power is first switched on. When a glow plug fails because of
overheating, the end of the element wire has a tear drop shape at the break.
Sometimes a microscope is needed to see this affect.
Vibration: If the engine is soft mounted the element is
shaken from side to side with tremendous force. This literally fatigues the
metal until it breaks. When you look at the end of the element wire break
through a microscope it has a jagged, rough type appearance. The only
solution is to increase the rigidity of your engine mount.
Shockwave: Most model engines use a steel or brass
liner mounted on top of a cast aluminum case. As the engine gets older, the
liner flange works its way down into the case and lowers the head with it. When
the piston clearance gets too low the increase in compression forces air out of
the squish band area with supersonic velocity and the action on the glow plug
elements is like when a jet plane zooms over your house and knocks out the
windows. The cure here is to raise the head with another head gasket.
Less often reasons why glow plugs sometime
fail are:
Cranking the engine when it’s flooded sprays
raw fuel onto the plug and the droplets beat the element over to the side of
the housing where it shorts out.
Another problem that
occasionally occurs is that engines sometimes wear abnormally, causing a
crankshaft to crack, bearings to fail, or a connecting rod to chew metal off
the crank pin. Of course, when this metal goes up and deposits on the plug
element, the plug burns out. Q
AND OF COURSE WHEN THIS
HAPPENS IT IS TIME TO SEE SUZY AT:
PERFORMANCE R/C HOBBIES
for a pocket full of those little glow thingies.
The 2008 membership dues are due now should
you forget
