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Written by Jim Ryan
How To Tame the Wire Monsters
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As seen in the September 2019 issue of Model Aviation.


With the increasing availability of reliable, electric-powered, retractable landing gear and low-cost servos, even inexpensive ARFs might have six or more servos built into the wing. Unfortunately, those six servos, in turn, require six servo connectors, which can make removing the wing for transport a bit of a hassle.

Luckily, replacing all of those connectors with a single master connector is a simple project if you have the right hardware. Follow along and see how it’s done.

How To Tame The Wire Monsters

e-flite t-28 trojan
01. The E-flite T-28 Trojan 1.2m features flaps and electric retracts for added realism, but the wing wiring is complex. Replacing the six stock servo connectors with a single latching connector is a quick and useful upgrade.

six servo leads
02. With six servo leads, the T-28’s wing wiring is a bit of a mess. Disconnecting (and reconnecting) all six leads for transport is time consuming and increases the chances of connecting something wrong. Wouldn’t it be better to have a single, mistake-proof connector?

trim all six leads
03. First, trim all six leads to the same length. The T-28 doesn’t give you much slack with which to work, but with a little care, you can neatly connect everything. Separate the leads and strip approximately 1/4 inch of insulation from each wire. Be sure to mark the signal wires so that you can match them up later. I use a fine-tip Sharpie permanent marker and put one, two, or three marks on each signal lead.

key to routing all six leads
04. The key to routing all six leads through a single connector is knowing that standard RC systems use a common bus for positive and for ground. You can join all six positive leads and all six ground leads and route them through a single connector. The signal leads for aileron, flaps, and retracts can likewise be joined into pairs.

multipin connectors
05. There are various options for multipin connectors. I like the Hansen Hobbies kits. The company’s 0.1-inch latching, polarized connector kits range up to 12 pins (enough for 10 functions!) and work well. These kits take different contacts than regular servo connector kits, so be sure to buy the right ones.

crimp the connectors
06. It’s easiest to crimp the connectors onto the leads before soldering the leads to the wing wiring. I own a Hansen Hobbies deluxe crimper, but I still prefer this old basic crimper that I’ve owned for nearly 30 years. There’s an excellent video on crimping connectors on the home page of the Hansen Hobbies website.

joined servo wires
07. The leads are carefully soldered to the joined servo wires. I find this to be easier if I first anchor the joined wires with masking tape, as shown here. This keeps the splice joint from moving around while I solder it.

soldering completed
08. With the soldering completed, the splices are covered with heat-shrink tubing. A larger piece of heat-shrink tubing covers it all. The contacts are pressed into the housing until the locking tabs click into place. I use the standard signal/positive/ground sequence for the aileron leads on the middle three pins then connect the flap and retract signal leads to the outer two. With positive on the center pin, there’s never any risk of reversing polarity and damaging the electronics.

male contacts
09. Next, crimp the male contacts onto the fuselage wiring harness. Crimping is much the same as for the female contacts on the wing harness. The contacts are then clicked into the housing. Be careful to match the exact pin pattern you used on the wing connector.

pin latching connector
10. With the five-pin latching connector assembled, regular servo connector contacts are crimped onto the other end of the wiring harness. You can then insert the contacts into the servo connector housings.

How To Tame The Wire Monsters

wiring harness
11. Here’s the completed wiring harness that is ready for installation. Note that the aileron receiver lead is connected to the three middle pins of the five-pin wing connector, but the flap connector has just a single lead. The retract receiver connector has an extra servo extension for the nose retract, and both single leads are spliced to a single pin.

radio compartment
12. This shows the finished installation. Not only is a tangle of wiring replaced by a single connector, but it’s now easy to bolt the wing on first then connect the wing from inside of the radio compartment. The latching connector is more secure than a regular servo connector but it disconnects easily.

What an improvement! It is simple with the right hardware. Share your project photos with me!

Sources:

Hansen Hobbies

chris@hansenhobbies.com

www.hansenhobbies.com

3 comments

If you have access to the tools, you can install D-sub plugs in the wing roots so that everything "automatically" plugs in when you mate the wing to the fuselage. Many RC sailplane enthusiasts have been using these to make field assembly easy on airplanes that can have up to 6 servos in each wing.

Yes, connectors right in the wing roots are a nice solution for aircraft with plug-in wing panels, but they don't really lend themselves to retrofits, or to aircraft with bolt-on one-piece wings like this T-28. There are several other choices besides D-Sub connectors. Multiplex MPX are another good option for instance.

The new E-Flite EC-1500 takes this a step farther by incorporating bullet connectors for the wing-mounted motors into the plug-in servo connectors. This is a really cool idea, and I hope Horizon makes those connectors available separately for builders.

Thanks for your comments,
Jim

Thank you for sharing that! Nice pictures with excellent step-by-step instructions. I will be printing this article and refering to it for many years for sure.

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