The retracted gear are looking good right now and so it is time to install the retract servo for the mains.

       To get started on mounting landing gear servo in the wing I needed to figure out a good location for it.

       The center joint of the wing panels seemed to be a good place as any for a servo mounting location. I just needed to shave it down to recess the servo a bit into the wing to clear the existing servos in the fuselage. A platform was cut in the wing 55 mm long and 12 mm high from the “floor” of the wing. The notch at the left of the platform was cut 20 mm wide. This will leave clearance for the servo arms as they turn.

       The mains will be actuated by the HS-225MG servo which weighs about 1.09 oz. This is a super strong servo which will help to efficiently swing the gear into a retracted position. 

       Servos that are purpose built for retracts are much too heavy for use in this project. This is why I opted to use standard use servos for the build. The only disadvantage of using a standard servo for retracts is that it cycles much faster than a retract servo would. This can be a problem if you use a “standard” radio transmitter that does not have the option of slowing down the servo transit speed. This means that if you do not have radio mixing slowing down the transit time that the gear will literally slam open and shut which is hardly a scale look.
       To fix this problem you can either use a computer radio transmitter that has the option of adjusting transit speed or use an on-board servo speed adjuster like the EMS Jomar Servo GoSlow module (Cat #1030). You can buy the GoSlow from Tower Hobbies. In this project I will be using my Futaba 14MZ programming to slow down the gear transit time.

       A servo mounting plate was made out of 1/8 birch plywood. It measures 45 mm by 48 mm wide and has the ends beveled to reduce weight a bit. Hardwood blocks were made to support the servo screws and CA glued to the servo plate. The blocks were pilot drilled before the mounting screws were installed.

       To install the servo mounting plate to the foam wing I used 5 minute epoxy with microballoons mixed in. The microballoons reduce the weight of the epoxy while maintaining good strength. Note: do not attempt to use any CA type glue on foam unless it is marked “foam safe” as it will eat the foam until it is removed.

       The plate was epoxied in so the top of the servo horn is about 62 mm from the back of the platform (on the upper right of the photo). The servo body mounts in the center of the wing, no offset is applied for the servo arm location.

       The control linkages to the retracts can covienintly be replaced by a 2-56 rod which eliminates the need for a clevis in the middle of the linkage. I used a couple of Dubro 2-56 rods (Cat# 801) and cut the excess treads off the ends to expose only about 4 mm of threads.

       The rods easily thread into the retract mechanism. At this point the gear is reinstalled and the wires routed through the foam wing. I just poked the rod through the foam at a slightly “downward” angle to meet up with the servo. You might need to widen this hole later to allow for free movement of the control rod.

       To connect the actuator rods to the servo a custom servo horn had to be made. I used the heavy duty servo horn that came with the HS-225MG to fabricate a horn with the right geometry to fully open and close both retracts within the normal range of the servo.

       The exact measurement of the holes will change slightly from installation to installation so it won’t help much to drill them the same as I did but you can use these photos as a general guide where to start. You can always use a spare horn to drill a few test holes in to get the perfect alignment and then drill a new horn to match. Notice that the holes are slightly offset to one end, this is to compensate for the servo horn being closer to one side of the wing.
       The offset from center line (as shown below) is to compensate for the geometry of the retracts below the servo. You may also notice I trimmed one end of the servo horn, this is so the horn clears the servos above the wing when installed on the fuse. I installed a couple of Dubro E/Z Connectors (Cat#121)  to the servo horn to connect to the 2-56 rods.

       After I installed the servo horn I hooked up my receiver and tested the servo under power. I checked to make sure that both retracts would lock in the up and down position. I then set my end points in my radio so the servo was not binding at ether end of it’s transit. The photos below show the gear in the up and down positions for reference.

       After the mains were fine tuned I mounted the wing to the fuse and trimmed the back of the wheel bays to match the wing mount plywood. So far so good :0)

       The nose gear of the Super Airliner is designed to be a modular unit and come out in one piece. In a way this will help me greatly with the installation of the nose retract unit.

       To start the conversion of the nose gear I stripped off all of the parts from the stock plywood support plate. I then made a mark 13 mm down from the top edge of the plate. From this mark down I applied a single layer of 6 oz woven fiberglass cloth to the plate. I used 30 minute epoxy and brushed it into the cloth making sure there were no bubbles or excess epoxy on the plate.

       Notice the direction of the plate and what side the glass is on. You don’t want the glass on the other side or it will not fit back into the fuse.

       I let the epoxy cure for a few hours and then trimmed off the excess. I now had to figure out how to mount the nose gear to the mounting plate.

       After looking at the nose gear a bit I figured out a way to mount it and loose some weight as well. I could trim off the side brackets and mount the nose retract unit with through bolts into the plywood plate.

       I proceeded to cut the sides off of the retract unit and sand them flush with my belt sander. I was sure to keep the sides square and not remove any excess material.

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