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Guinea pig cargo door

Ryan O.

Well-known member
#6
I haven't built a Guinea pig yet, but I have come up with an idea for a mechanism that can work. You can take a 12 gram servo and remove the potentiometer from the inside. Next take essentially a barrel that has a servo horn glued to the side and attach it to the servo. Make a string that only becomes taught when the door is fully deployed. You would still need the 9 gram servo in the original location to keep the door from opening before the cargo is dropped. Anyways, back to the string servo, set it so that it can bring the door closed at least an inch further than normal and once it is in far enough turn the servo arm back to the closed position and stop winding up the string. You will need to fly the plane close so you can see when the door is almost closed, otherwise it might destroy the servo. When I make mine the attachment point where the string meets up with the cargo door can be connected with rare earth magnets which will release from each other when enough force is applied. This probably takes a lot of practice and also some good piloting and multitasking skills, but it should work. Unfortunately, this needs two servos to work. If you plan to carry larger cargo this will need to be moved more to the side. The door also has to open more so that the cargo doesn't detach the magnets. The door will also need some strengthening. I attempted to draw a diagram of what it would look like.
WLwR5wuZQ%SaUqSH52yLIg.jpg

Note, everywhere on the diagram that says actuator, it should be potentiometer.
 

mach1 rc

Well-known member
#7
I built a mini Guinea pig a long time ago but I don't have any pics😔. I just attached a controll horn to the cargo door and then ran a push rod towards the front of the plane i hooked it up to a servo to make it kinda like a elevator that was hooked up to one of my switches. So when I flipped the switch it would open and when I flipped it back it would close. Hope you can understand that.
 

Sero

Well-known member
#9
I haven't built a Guinea pig yet, but I have come up with an idea for a mechanism that can work. You can take a 12 gram servo and remove the potentiometer from the inside. Next take essentially a barrel that has a servo horn glued to the side and attach it to the servo. Make a string that only becomes taught when the door is fully deployed. You would still need the 9 gram servo in the original location to keep the door from opening before the cargo is dropped. Anyways, back to the string servo, set it so that it can bring the door closed at least an inch further than normal and once it is in far enough turn the servo arm back to the closed position and stop winding up the string. You will need to fly the plane close so you can see when the door is almost closed, otherwise it might destroy the servo. When I make mine the attachment point where the string meets up with the cargo door can be connected with rare earth magnets which will release from each other when enough force is applied. This probably takes a lot of practice and also some good piloting and multitasking skills, but it should work. Unfortunately, this needs two servos to work. If you plan to carry larger cargo this will need to be moved more to the side. The door also has to open more so that the cargo doesn't detach the magnets. The door will also need some strengthening. I attempted to draw a diagram of what it would look like. View attachment 151970
Note, everywhere on the diagram that says actuator, it should be potentiometer.
Not bad. Main issue for me would be the string that's right in the middle, it will get in the way.
 

Sero

Well-known member
#10
I built a mini Guinea pig a long time ago but I don't have any pics😔. I just attached a controll horn to the cargo door and then ran a push rod towards the front of the plane i hooked it up to a servo to make it kinda like a elevator that was hooked up to one of my switches. So when I flipped the switch it would open and when I flipped it back it would close. Hope you can understand that.
Kind of the route I'm thinking. Just need to make sure there is no stress on the servo in the fully closed or open position.
 

Ryan O.

Well-known member
#14
I took apart a broken servo, and tried to remove the potentiometer, but it was a part that held the plane together, and had to stay in. A standard, or even 12 gram servo placed on the bottom bellow the door can close it, but would get damaged if cargo slipped back when it was closed, so the 9 gram in the top would still be needed. If set to a two position switch it can close the door after it is opened. To keep it from being stressed as the cargo falls out the door can be braced at the fully open position. The on problem is that it requires a 7+channel radio for all the controls. Differential thrust or the rudder servo can be sacrificed for the last channel. If you have the time pinning the rudder is probably the better option because Differential thrust is more than enough to turn it. Just be prepared to land it without rudder if your mixing isn't good.