Twin Speed 400 model - RC Groups
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Sep 04, 2002, 03:56 PM
Registered User

Twin Speed 400 model

Help, please: I am in the planning stage of a twin design that is to be powered by a pair of Speed 400 motors. Electric stuff is significantly beyond me, and I really need help. What are the advantages and disadvantages of wiring my batteries in series, vs. in parallel. Also what are the advantages of putting all of the batteries in the fuselage, vs. splitting the cells, and putting one half in each nacelle. Since I am quite a techonophobe, please make your comments in the least 'techno' jargon possible. So that even I could understand them! Thanks...
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Sep 04, 2002, 06:58 PM
Registered User
Sorry but I have no idea how I could discuss the pros and cons of technical decisions without using any technical language.

So I'll just say what I'd probably do which is to wire the MOTORS in parallel to one speed controller and a single battery in the fuselage. Like every other Speed 400 twin I've ever met .

Sep 05, 2002, 07:30 AM
ChrisP's Avatar
THE Gus Morfis ? WOW !

I guess you would have a hard time getting the model to balance with the cells in the nacelles. On a Twinstar the 8x2400 mAh pack is right up in the nose.

Motors in parallel i.e. both motors 'see' 9.6v.

Speed controller 25A minimum, 35A better.

The Twinstar has good numbers for a twin 400 powered model :

453 sq ins (net i.e. without the fuselage area) @ 45 - 50 ozs AUW.

Bare model ca. 20 - 22 ozs

Geared motors (e.g. 1:2 ratio) will give you more punch.

Love your 1/12th plans. Bought a bunch way back.
Last edited by ChrisP; Sep 05, 2002 at 09:30 AM.
Sep 05, 2002, 11:47 AM
Still learning.....
JWC's Avatar
Hello Gus,

You probably aren't aware, but you share your name with a famous (for this group) person, hence the good natured ribbing.

Good luck on your twin, do a search on this site and you'll come up with a BUNCH of information on how to wire twins together.

Sep 05, 2002, 12:00 PM
ChrisP's Avatar
Originally posted by JWC
You probably aren't aware, but you share your name with a famous (for this group) person, hence the good natured ribbing.
No ribbing intended.
You mean (and it's an honest question) this is NOT the 1/12th scale warbird Gus Morfis ?
Sep 05, 2002, 12:22 PM
RPV builder & operator
Pierre Audette's Avatar
Wiring pack in series is feasable, but should be done on 'matched' packs (capacity, # cycles), otherwise one may dump into the other. I would also think that using two packs (ie: two 1250 packs) would be heavier than a single pack (ie: 2400 cells).

One option could be to use Sp400 race 4.8V motors in series with a single pack. Depending on the props used, the number of cells would vary.
Sep 05, 2002, 08:57 PM
Still learning.....
JWC's Avatar

Take it easy on me!

Holy Cow!! I just thought you had a cool name! Okay, enough of the hero worship, we'll get down to the question.
First, a disclaimer: There are many more people out there with much more experience than I. I'll do my best.

Here goes: To wire a twin, your real issue is weight. Two speed controllers and battery packs or one.

My recommendation is to wire both motors negative to negative and solder that junction to the negative wire of a single speed controller. Then, wire both motors positive to positive and solder that junction to the positive wire of the speed controller. Now you have the option of using one battery pack, hence, saving weight. (Ensure that your speed controller can handle the amps that your motors draw, assume approx 35amp esc minimum for a speed 400.)

The question of series or parallel usually applies to battery packs, whether to combine the packs to increase voltage (power) or amperage (endurance).
Series: increases voltage, motors turn faster, life expectency of motor is reduced.
Parallel: increases amperage, plane flies much longer per charge, carrying more weight, performance suffers.

Your question as to the advantage of one over the other? Hmmmmm......Ensure you have enough cells to make the motors turn fast enough to fly the plane, ensure that the cells you choose have enough endurance to make the flight long enough to enjoy. It's kind of a balancing act.

Simply stated: To fly a twin speed 400 plane, wired as I have suggested above, use a single battery pack 8-10 cells between 1300-2000 Nicad or Nimh.

(Whew!) I think my brain has had enough exercise for today! Attached is a link to an e-zone discussion where some nice soul has drawn a picture of how to wire twins. Personally, I think pictures help out a great deal!

Gus, I hope this helped out a little, apologize for being so long winded. If you have any other questions or I need to clarify something, please feel free to PM or e-mail me. I'd be more than happy to help.
Take care,

Jeff Charlot