Adding Payload To An RC Cessna

For just a few bucks you can add a payload to your flying toys. In this case it’s a Cessna RC plane which now has an added surprise. The first thing to be dropped was a parachute with a weight on it (for testing purposes). But there are hints of future projects that will use the same system for different purposes.

As you can see in the image above, the system depends on an additional compartment attached to the bottom of the plane. It was built from foam board to keep the weight down and connects using rare earth magnets. The bottom of the enclosure acts as the door, hinging on a servo motor with a bamboo skewer as the axle. So far the test drops have gone pretty well, but some more work needs to be done with the parachute design. It only opens about 60% of the time. We can sympathize, having had to work out some of our own parachute issues.

Don’t miss video from the plane as well as the ground after the break.

11 thoughts on “Adding Payload To An RC Cessna

      1. Absolutely have. That was my original plan, and I spent a lot of time trying to design one. The problem was that I wanted to make this as cheap a mechanism as possible, and I was having difficulty coming up with a bomb-bay style door actuated with only one servo. I have some fresh ideas on how to achieve that though, hopefully for a future project in which the whole thing will also be embedded in the fuselage to reduce drag. Thanks, please let me know if you have any ideas.

        1. I was about to ask the same thing, I am developing a scale cargo pod for my 1.8m Husky to do candy drops at an event we put on where we take orphans flying, but in the location it’s in deflecting down like this I believe this mechanism would cause a stall because I do the drop at near stall speed with slats and VG’s to delay the stall. I am searching the internet for an effective solution that uses one mini servo but it’s harder than one might think. I enjoyed your project and you’ve given me some ideas but I have to do a split bomb bay style door. If you have any ideas on how to do this please get in touch

      2. Just spitballing here, so it’d probably need some [a lot] of testing to make work…

        Two doors, bomb-bay style, each with a small protrusion perpendicular to the door. This is the fitting to the actuator rod.

        A servo sits between the two, with either a disc or arm style rotor. Wire rod linkage attached 180 degrees apart to the rotor, with the other end leading to the protrusion on the door.

        When the servo turns, each rod is pulled towards the other side, actuating the door open.

        If you have decent fab tools: have both doors swing open with their hing points close to each other. Servo drive one door, glue on/cut out gear teeth so the doors operate simultaneously.

      3. Thanks for that reply! I coincidentally had that same design in mind – I guess it is the most obvious one and you described it very well. The problem I was running into was that the doors would not open a full 90 degrees, which is essential for me. I came up with a way that they would, but then they wouldn’t retract, which was also essential.

        But one thing you said just gave me a great idea. Thank you so much, Kaj!

    1. Thanks. CG is definitely an issue, although I must admit that high wing airplanes are quite forgiving when it comes to tampering with the CG. You can trim out small deviations with relative ease. But I kept the heaviest part of the mechanism (servo) quite close to the CG anyways, so I don’t think it had much of an impact.

      1. Flite Test isn’t the end all be all, this has been done a lot. Candy drops have been going on for decades. What makes it unique is your own design and way of doing things, don’t let your mind be polluted by other people’s design and just do what you want and enjoy :)

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