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Friday, January 20, 2012

Fixing the Flyzone Fokker Dr.1 Micro

Update:  Shortening the front 2 of 4 landing gear struts by slicing off the existing anchors, making them shorter by an 1/8th inch when reinserted and thereby increasing the Angle of Attack of the fourth wing, fixed the plane's tendency to tuck-under (unwanted, increasing nose down).  It also allows the plane to fly a smidge slower.

Also see:

It is a shame to lose the cool factor of the Flyzone Dr.1 because of Hobbico/Flyzone's crappy micro gearboxes, so I had to fix the Triplane.  The Z8RC brushless Parkzone Corsair conversion was so quick and easy, I decided to transfer an old Hobbyzone Champ's internals into the Fokker.  This project wasn't quite as easy, but only because I had to figure it out as I went along.
If you follow this tutorial, it should take about an hour for a full Flyzone Dr.1 to Spektrum DSM conversion, perhaps as little as 30 minutes for a motor and gearbox only conversion.  Both are easy.

Since I had the plane open, I opted to do a full conversion so I could lose the additional transmitter when I fly the Triplane.  Plus, a full conversion allows computer control.

There is another possible fix, but I haven't confirmed it. On Tower's site it shows the Flyzone Playmate replacement motor with a metal pinion.  This motor should fit.  It seems like it would be a pretty similar level of effort to the gearbox-only change-out, as far as opening the airplane and cutting out the gearbox (I don't think you could change the motor without pulling the gearbox but it might be possible).  But it wouldn't power up the plane any more or allow the use of a better radio.

I was tempted to add ailerons, that would be an easy mod, but the Dr.1 airframe is so light I decided to keep it as much of a slow flier as possible.  The final, full conversion weighs 35 grams in RTF form, a whopping 1 gram lighter than stock.    Thrust to weight ratio came in right at 1:1, a monster improvement!

1. Remove the white cowling, it was glued in place with two dots at the bottom sides and another dot or two at the top middle.  Slice the glued spots with a sharp knife.  Take your time and it'll work loose.

2.  Cut along the green line, below, just behind the landing gear to remove the entire motor section with the gear attached.
The Champ motor is way bigger than Flyzone's motor.  But the biggest difference is the motor pinion is brass instead of plastic.  Flyzone's plastic motor pinion will strip within a few flights, guaranteed.  They are selling known defective products to save 0.0004 cents per copy.
3. Glue the black dummy radial motor between the four spikes sticking out of the nylon Champ gearbox frame.  You'll need to trim a little bit of foam out of the center of the dummy radial to make it fit snuggy.  It is important for the radial to be snug and glued securely, because the back of the dummy radial will help glue the Champ gearbox to the Dr.1's firewall in the next step.
4.  Glue the back of the dummy radial to the Dr.1's firewall.  The motor axis should be aligned with the existing shelf where the old gear box sat.  You'll need to trim away some of the foam underneath the original gearbox to make room for the larger motor.  You'll also need to trim a bit off the two highest cylinders since the dummy radial will be a touch lower inside the white cowling.

The back edge of the nylon frame of the new gearbox should be aligned with the front face of the Dr.1 firewall to make sure the motor shaft sticks out far enough to clear the Champ prop.
5.  If you are doing a motor-only conversion, solder the two pins of the Champ motor's male connector to the male connector of the Flyzone's motherboard's motor connection (shown in the picture below Step 2, above).  Keep the red wires in the same orientation to make sure the motor spins the right direction, it won't hurt the motor if you get the polarity wrong, but you'll have to do it again.  Wrap the connections with a small piece of electrical tape.  Button up and you are done!

6.  If you are doing a full conversion as shown above, cut the foam below the Flyzone servo motherboard to remove it.  Insert the Champ's all-in-one motherboard in the nose.  I moved it back a little to help with the CG.  It needs to be oriented just like it sits in the Champ, with servos on the top side of the board as it sits in the plane (with both the plane and the board sitting right side up), otherwise the rudder and elevator servos will be swapped.

7.  With the rudder and elevator control surfaces centered, bend a 90 degree angle in the control rods and insert them into the Champ servos.

8. Plug in the motor.

Button up and you are done!
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