Converting Decathlon to DX6 [Archive]

Longbranch

03-14-2006, 09:46 PM

Hi Guys,

I have had a Parkzone Decathlon for some time now, and as it's been knocked around, and gotten older, it's gotten glitchier (if that's actually a word). Perhaps the electronics are getting old, or maybe I'm getting spiked by who knows what out in my very rural flying area. Either way, I recently purchased a new Spectrum DX6, thanks to some of your advice. I want to use the DX6 with the Decathlon airframe, as it's well within the size intended for the DX6. My question is this: can anyone offer some advice concerning replacement parts for the esc etc.?

The Decathlon (which is nearly exactly the same as the Parkzone J-3 Cub) comes as an RTF with Parkzone's standard Rx, which is an Rx & esc all in one.

Parts list etc. can be found here:

http://www.horizonhobby.com/Products/RelatedParts.aspx?ProdID=PKZ1400&Category=Parts%20Listing

It's a big heavy beast, and so are their servos for that matter. The gear that comes with the DX6 is much lighter and smaller. I haven't checked exact specs, but I'm guessing that the Spectrum S75 servos are a rough equivalent to the Parkzone mini-servos in strentgh and torque. They certainly weigh less. I'm assuming they'll work fine for the Decathlon. The next question is the motor. The Decathlon comes with a 370 brushed motor and gearbox, and swings a 8.25x5.5 prop. I have not been overly happy with the power of the stock setup, nor the performance of the stock battery and battery charger combo. I suspect the chargers of having been giving me false peak indicators etc. I would love to step this plane up to a brushless/li-po combination, losing weight and prolonging flight times in the process. Given the stats for the stock power system, can someone recommend a combination of brushless motor, prop, battery and esc to fit the DX6 components? Any help or advice you can offer for this little project would be greatly appreciated. It was largely due to aeajr's recommendation that I bought the DX6, and I'm glad I did. I think it will be a wonderful radio and do exactly what I want it to do, if I can only modify the Decathlon to carry it, and maybe upgrade the power train at the same time. Thanks!

aeajr

04-14-2006, 05:20 AM

Let's look at batteries and chargers. Let's just say that you need to use
the
right charger for the
right battery. Don't mix and match or you could create a dangerous
situation.
Used properly they are all safe to use. If you want to know more about
NIMH,
NICD and Lithium batteries, these links contain useful information.

Battery Basics:
http://www.modelaircraft.org/mag/FTGU/Part8/index.html
Notes on Lithium Batteries
http://www.rchobbies.org/lithium_battery_breakthrough.htm
safety warning on Lithium Batteries
http://www.modelaircraft.org/safetycom.asp

Transmitter and Receiver Batteries

These are typically made
from NICD or NIMH cells that are designed for lighter loads than motor
batteries. As such, they need also to be charged at slower rates. The
general rule is 1/10 C charge rate where C is the rated capacity of the
battery. So, on a 600 mah transmitter or receiver pack would be charged at
60
mah. At this rate you would charge an empty pack for 10 hours to bring it
fully up to charge adn in fact you have to charge them a little longer than
that to really get them fully charged, so figure 12 hours to be sure. This
is
handled nicely by the charger that comes with the radio system. This is an
example of such a charger.
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXNK66&P=ML

Quick charging these packs is not recommended as a standard practice.
If you quick charge them, they will likely get hot. Don't quick charge them
in the plane or the radio as the heat build up could damage some of the
surrounding electronics or might deform plastic or epoxy based components
near
them. Fast charging at 1C will generate a lot of heat and can lead to early
pack failure which could happen during a flight.

There are after market chargers that are focused on transmitter and receiver
packs. Here is an example from AccuCycle
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXL357&P=ML

Charge 'em slow and treat them right and they should last for years. If you
tend to fly for long periods, pick up an extra transmitter and/or receiver
pack and charge them slowly, at home. Here are a couple of examples.
http://www2.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=futaba+battery&FVPROFIL=++
http://www.amondotech.com/index.asp?PageAction=VIEWCATS&Category=228

Motor Packs

The motor on the typical parkflyer needs to pull power at a much higher rate
than a receiver pack can provide. So the batteries that power the motors
are
typically of a different design/grade so that they can supply electricity
at these rates. As a result when we charge them we can charge them much
faster too.

The general rule here is that NICD motor packs can be charged in the 1.5 -
3C
range with 2C typical. NIMH packs are best charged at 1- 2C with 1.5C
typical. Higher performance packs can take the higher rates. See what the
maker recommends. This way you can get in your flight, then put the battery
on a charger and be ready to fly that pack again in 15 minutes to an hour.
Have 3-4 packs and 2 field chargers and you may never have to stay on the
ground for more than a few minutes. That's the way I do it.

Lithium motor batteries are becoming popular. However their chemistry is
very
different from NICD and NIMH cells. As a result they need a different type
of
charging process. If you are using Lithium packs, you MUST use a charger
that
is specifically designed to charge lithium or you could end up with an
explosion and/or a fire. This is not joke. Don't ever put a lithium pack
on
a charger that is not designed for lithium cells. Follow the charge rate
recommendation of the battery maker carefully!
Video of a lithium battery being overcharged.
http://rc.andersh.com/video/lithiumbattery.wmv

S and P terms

When we talk about battery packs, a designation of XSYP is sometimes used.
This indicates how may cells are in serial and how many groups of these
cells
are connected in parallel. While the terms are most common in the Lithium
world, they can just as easily be applied to NIMH or NICD packs.

So a 3S2P pack is made up of 6 cells. There are two groups of 3 cells. The
three cells are connected in series. This is the 3S designation. When
connected in series their voltages add. So 3.7V Lithium cells in a 3S
configuration would have a voltage of 11.1V and be designated as a 3S1P
pack.
If these cells were rated at 2000 mah each then this would be a 3S1P 11.1V
2000 mah pack.

Now if we took two of these 3S1P packs and connected them in parallel, the
capacity adds, not the voltage. So this would now be a 3S2P pack rated at
11.1V and having a capacity of 4000 mah. Like connecting two gas tanks
together. The motor in you truck would not be stronger but you could drive
further because you are carrying more fuel.

You could do the same with NICD or NIMH packs. .

Battery Chargers

There are timed chargers and peak chargers. Timed chargers, often bundled
with RTF airplanes, work well if you always run your pack all the way down.
If
you have one, use it, but I don't recommend you go out and buy one. Peak
chargers, are the way to go. They read the pack and know when it is fully
charged.

An AC powered charger is convenient to use at home, but won't help you
recharge at the field. All of mine are DC peak chargers except for my radio
chargers. I have a car booster pack that runs my DC equipment in my shop.
And, by the way, I have used it to jump start cars. Works great! This is
similar to the one I have.
http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=AUTO&pid=02871472000

While many peak chargers are focused on charging motor packs, most also have
low charge rate settings that can be used to charge transmitter/receiver
packs
too.

Here are a few examples of peak chargers for your consideration. I have the
first three shown here.

HobbyZone Peak Charger - $19
Simple and inexpensive - This came with my Aerobird. I added
different types of connectors so I can use them for all kinds of battery
packs. Plugs into the cig lighter port. Work just fine. 4-7 cells NIMH
and
NICD
http://www.horizonhobby.com/Shop/ByCategory/Product/Default.aspx?ProdID=HBZ1026

Hitec CG-340 - $39 This is an older
model. It works well, but the charge rate is limited to 1.5 amps for NIMH
and
3 amps for NICD. You need to make or buy leads. It will charge up to 16
nimh
or nicd cells.
http://www.horizonhobby.com/Shop/ByCategory/Product/Default.aspx?ProdID=HRC43340

Triton Charger - $130 - This one showed up under the Christmas Tree - :-)
It handles up to 24 cells NICD/NIMH cells or 4 cell
Lithium cell packs as well as Lead/acid batteries.
It will also cycle battery packs which my others will not do. So far I am
very happy with it.
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCJG7&P=ML
Reviews
http://www.rcbatteryclinic.com/triton.htm
http://forums.radiocontrolzone.com/printthread.php?t=135705
http://www.rcuniverse.com/product_guide/NewProduct.cfm?product_id=19\

I don't have these but have heard good things about them.

GWS MC 2002 Peak Charger - $49
Seems to be a good value for a first charger for NIMH and NICD packs of
4-12
cells. It has charge meter, but not the digital display or memories of the
Triton or others. Includes a variety of connectors. It can not slow charge
receiver/transmitter packs due to 90 minute charge time cutoff.
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXHHV3&P=7
http://www.horizonhobby.com/Shop/ByCategory/Product/Default.aspx?ProdID=GWS3000
http://www.gws.com.tw/english/product/aux%20circuit/charger.htm

Wattage Parkflyer AC/DC charger $50
http://www.hobbypeople.net/gallery/130108.asp
AC/DC convenience for Nicd or NIMH up to 12 cells. You need to make or buy
leads. In my opinion, this would be best for field charging packs from 250
mah to 1500 mah as 2 amps is the top charger rate. However, as a second
charger for home use on AC where charge times would be less of an issue,
This
pack could be used to charge packs up to 4000 mah, which would take 2 hours.
Not good for field use but just fine for getting your packs ready the day
before. Then take it to the field for DC charging your smaller packs at a
reasonable rate.

Multiplex multicharger - - $80
Charges 1 to 5 Lithium cells or 1 to 14 Nicad or NiMH cells at up to 5 amps
I read a review about this one somewhere, may have been Model Aviation, and
it
sounded pretty good.
Details here
http://www.multiplexusa.com/product_fs.htm
Manual
$79 at Tower Hobbies
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXKSY1&P=ML

Accu-Cycle Elite - $149
Charges two batteries at once
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXEYD4&P=7
manual
http://www.hobbico.com/manuals/index.html
Reviews
http://www.rcuniverse.com/magazine/article_display.cfm?article_id=405
http://www.rcgroups.com/links/index.php?id=4607

Great Planes PolyCharge4 DC - 4 Output LiPo Charger - $100
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXKAU0&P=7
If you are seriously into LiPoly ( not Li-ION) This may be the charger of
your
dreams. Charges 4 Lipoly packs at one time. Each charge port is limited to
30 watts, so it can charge 1S or 2S packs at up to a 3 amp rate. 3S packs
can
be charged at up to about 2.5 amps and 4S packs can be charged at about 2
amp
rate. Therefore, this charger seems a very good choice for 1S or 2S packs
up
to 3000 mah capacity, 3S packs up to about 2500 mah and 4S packs of up to
about 2000 mah. You can charge packs of higher capacity but it will take
more
than 1 hour to charge based on the typical 1C charge rate for LiPoly packs.

If you have packs with a 2, 3 or 4P designation, this charger might also be
good for you. 3S4P packs up to about 10,000 mah would work well if each 3S
component can be charged separately. 4S4P packs up to about 8000 mah would
also work, if you can charge them as four 4S1P packs of 2000 mah each.
Discussion thread on this charger
http://www.rcgroups.com/forums/showthread.php?t=354754&page=3&pp=15

A review of a group of Lithium battery chargers
http://www.rcgroups.com/links/index.php?id=4676

Sometimes I have 3 chargers running at the field at one time charging motor
batteries for my parkflyers or receiver batteries for my sailplanes. I hate
being grounded. So they are put to good use.

I invite others to provide insights on the subject or to recommend chargers
that have served you well.

A series of posts on electric power system basics
http://www.wattflyer.com/forums/showthread.php?t=1933
http://www.rcgroups.com/forums/showthread.php?t=417868