TREX 550e FBL RC Heli Creating a Build List


Setting out to just decide what to order for my first build was an interesting task. There are two ways to go into a hobby on the cheap to see if you like it or like you will be in it forever. I started out cheap with a $40 ClearView flight simulator. Then came an mCP-X RTF kit. After upgrading to a DX8 transmitter things have been a lot of fun. The RTF DX4e is now collecting dust.  After really enjoying flying my 2 mCP-X’s for a couple months it seemed that I might be in this hobby for a little while.  For the 550 build I’m going the other direction and chose every part that I would ultimately want on this heli.

Initial Selection

Why choose the TREX 550e FBL heli? It’s relatively large, with reasonably priced easy to find high quality mechanical parts and it has proven to be a good flying heli. Going flybarless was a no brainer, as it appears that all helis are going in that direction. FBL helis also offer more stability(i.e. behave like a larger heli), have less drag and less parts to break in a crash. The mechanicals of the 550 are 600 sized but pushing smaller blades in lighter heli so the batteries last longer. The next size up TREX 600 is about to be replaced and the TREX 700 was past my size comfort level. It’s just plain big.  The TREX 550 seems to be in a sweet spot where the price, performance and size seem reasonable.

Creating a Build List

Starting a build seemed easy at first.  A TREX 550e FBL kits comes with everything but receiver, batteries and a transmitter.  That didn’t seem too bad. However, Align has put a lot  of effort into producing a very affordable kit and the electronics are adequate but could be better.

GrandRC has a great build your own 550e FBF Combo which offers many upgrades and the ability to delete many components. This can save money or the time and effort to sell off the parts that you don’t want.

Batteries: Hyperion 5000 VX G3 6S 22.2V

From what I have read Hyperion and Thunder Power batteries have the best reputation with Hyperion getting some press for handling more charges without losing capacity than the others when charged and used properly.

Charging System:   Cellpro PowerLab 8 v2

Ideally this is a forever purchase, and numerous people suggested the Cellpro PowerLab 8 v2 which is a NICD/NMHD/LIPO charger with many cell balancing and charging options. This charger has numerous optional boards supporting  different battery types. Hyperion batteries are compatible with ThunderPower connectors.  The  “Cellpro (JST PA) PowerLab-to-ThunderPower (Molex) or PolyQuest (Yeonho) Safe Parallel Adapter” allows charging multiple batteries of the same type in parallel.  The parallel kit comes with 2 boards for charging 2s through 6s batteries.

Power Supply:   Feather Power

This is an inexpensive solution that a number of RC guys have had good luck with. You can order a pair of power supplies connected together to give you 24V at 47A if you want to charge faster.  These are modified computer server power supplies. You need to supply your own power cable and will need to do some wiring.

12V 47A power supply for the charger:

Gyro Systems: Skookum SK-720

There really are two 3D Gyro systems  that seem to be above the fray( Skookum and Mikado V-Bar).  I decided on the Skookum SK-720 because of the upcoming GPS option for it and the bail out feature it has as well as the programmable ( Training Wheels )  Basically you can dial in some auto-leveling while you learn to fly it better and gradually remove the training wheels if you like. Considering the cost per mistake, this seemed like a good choice. It offers support for a number of servos.

The Motor: NEU 1515 2.5 DF  ( 1650 kV )

The stock motor is fine but it is known to overheat and have bearing failures. Kontronik  has a new 600 class motor that looks really nice, but has no service history.  What made my  decision easy was that a local heli guy was upgrading his 600 series heli to a 12V system and wanted to sell his NEU 1515 2.5DF for a great price that I couldn’t refuse. As mentioned earlier the TREX 550 takes 600 class components.

ESC/BEC: Kontronik Jive 100LV  ( Electronic Speed Control for the motor )

The ESC is an area where there seems to be agreement that Kontronik is a leader. The Jive 100+  ESC/BEC is supposed to offer rock solid stable rotor speeds and has  a solid BEC circuit. That said the BEC isn’t completely eliminating the battery. They suggest putting a 4 cell NIMH receiver battery in parallel with  the BEC circuit especially when driving high powered servos.  The BEC is rated at 5-6V ( configurable in .2V steps) and 5A continuous – 15A peak. The  BEC defaults to 5V and requires a special device to change that.

Servos: JR DS8717’s, BLS251

The DS610’s that come with the system are respectable, however the JR 8717’s are faster with more torque and are more durable. I swapped the DS650 out for a Futaba BLS 251 which isn’t any faster, but should have a much longer service life being brushless. From what I can see Futaba’s cyclic servos would last longer than the 8717’s and pull less current, but in this case the JR’s are much faster and pull with more torque.

The SK-720 has a drop down list of supported tail servos and the BLS 251 already has a standard setup.

Receiver:  (SK-720) with DSMX satellites and TM1000 telemetry

The key is that the SK-720 allows two DSMX satellites to be connected and the T1000 telemetry has its own transmitter so it stands alone, or could send the RPM signal to the SK-720 for it’s SD logging.

One DSMX satellite came with my DX8 transmitter as well as the TM1000 telemetry module with voltage and temperature sensor. I chose the DX8 for a  number of reasons but I could have just as easily gone with JR or Futaba. With the DSMX system, Spectrum seems competitive with Futaba’s FAAST system.  The Telemetry Voltage sensor is a plus and will allow setting a voltage alarm in addition to using a timer. These batteries are all very sensitive to being drawn too low. (I’ve since ordered the brushless rpm sensor as well for the T1000 )



Pinion Gear

Because my motor has a 5mm spindle, the default 6mm 16T motor pinion gear will not work. So I ordered the following:

RevCo 0.7M Hardened Pinion Gear 5mm Shaft Diameter 16T HO-0700H-16T

Connectors: Deans Ultra Plug

The ESC, batteries and charger all have unfinished ends and require the selection of connectors.   Deans Utra Plugs have a keyed connection that can’t accidentally be reversed and they generally looked solid.

Additional Tools:

  • Ball link pliers
  • Hex Driver Set
  • Pitch Gauge
  • Digital Calipers

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