GrafBot:: a project to develop a UAV to execute graffiti tags.
A marker mounted to an armature of a quadcopter (arducopter specifically).
This model has a limited payload – 500 grams~ -.
Every unit placed on the copter must be weighed and balanced.
However, it is imperative that the GrafBot executes its function with materials proper: ”Hard to Buff” ink and a fat marker, in true graf style, like the below image.
The markers have arrived:
I chose two different “style” of Pump marker. I weighed each one without the cap but at capacity with ink:
To be sure that the GrafBot knows how to execute commands in the most accurate way possible, it is imperative that the arducopter knows when it is against a wall and when it should begin coded draw functions.
To assist the arducopter, we use a sonic range finder and two momentary switches. In order for the copter to begin execution, both the sonic range finder and both of momentary switches mus be activated.
The sonic range finder is activated when the copter is faced the appropriate way (i.e. front) and any surface is within x inches. To assist in precision, the copter has on the armature for the marker, a second stabilizing arm (to assist in keeping the marker, once there, against the wall). On the end of that stabilizing arm, is the momentary switch.
There is a second momentary switch attached to a protruding section of the marker holster. When the copter is pressing the marker against the wall, both momentary switches are activated.
Here is the initial coding for the range finder
Then we attached the momentary switch to the stabilizing arm of the armature.
(below is mock up of the actual quadcopter construction. The blue foam is the approx. size of the quadcopter and is mounted on a remote control car).
We were very concerned about the abilities of the copter to both apply forward force and simultaneously remain at the appropriate level in the air. Therefore the car is meant to simulate the copter’s potential weakened force.
Because we are asking a flying vehicle to come within close range of vertical rigid surfaces, it is imperative that the copter has a protective bumper. This is to ensure that the copter’s blades are kept from danger and that when (not if) the copter touches the wall, it does not spell an end of that particular mission.
In this aim, it would be wonderful for the copter to hit the wall and ricochet instead of crash.
Bear in mind that the payload weight is still a concern.
I attacked, initially, with styrofoam bumpers.
However, these were breakable as when the styrofoam was cut to fit into the hollow arm of the copter, it could not bear the length and width of the required styrofoam bumpers.
So, perhaps, to 3D print (a lightweight hollow plastic material) a holster for the foam, or some thin plastic (re: 2 Liter bottles re-shaped for our needs) would be best.
Grabbed my boyfriend’s digital calipers and went to measuring.
These can be manufactured with ease (as they will break) and might be sufficient on their own to protect the copter blades….
The above design fit into the MakerBot bed, and met all requirements, but would take 11.5 hours to print (as it is quite large).
So, I modified the design:
I printed this file:
This is my first 3D print, and had some scaling issues and therefore this print (which takes 2.45 hrs) is useless (as the arms do not fit outside the rotor’s blades).
Therefore, back to Rhino. This being said, take note of the first and second arms in the image above- the back one is printed hollow and is much smaller than the first arm. The first arm is fairly thick and more robust than I had imagined, and the weight of the print is infinitesimal compared to other materials.
These arms- protruding from the center bar- are holsters for thin plastic (like 2 liter soda bottles)- to make the lightest weighted bumper ever!