When I entered the hobby a couple years ago brushless gimbals were just becoming popular. I wanted a way to stabilize my camera in flight, but I could not fork over the cash for a basic two-axis, let alone 3-axis, gmbal. Being the person I am, I decided to build a gimbal from scratch. The first build was a moderate success and it taught me the basics of gimbal design. As the years have passed brushless gimbals have come down significantly in price, and for the more common action cameras it may no longer be economical to scratch build a gimbal. Despite this, one may wish to construct a brushless gimbal to fit a unique camera or acommodate a certain airframe. In this article I'm going to show how to build a two-axis brushless gimbal from scratch, using very basic tools and techniques.
Homemade gimbals are commonly 3D printed. For those of us who do not have access to a 3D printer, using acrylic can be a great choice. Acrylic, aka Plexiglas, is a thermoplastic that can be cut and drilled with basic hand tools, and with adequate heat it can be bent into various angles. You can buy it in the form of large to small sheets for a relatively cheap price at your local home improvement store.
On a fundamental level, a two-axis gimbal is composed of two motors, two ‘arms’, and the camera. The roll motor connects to your aircraft, one arm connects the pitch motor to the roll motor, and the second arm connects the camera to the pitch motor. To build these arms, I first start with acrylic strips.
The strips are rough cut to approximately 3/4x5 inches in size and 1/16 inches in thickness. These dimensions will vary depending on the motors and camera you use, bu a long rectangle is the basic shape. To get the thickness required for a strong, rigid arm, two strips of the acrylic will have to be glued together. This will bring the thickness up to 1/8 inch. I find standard superglue works well to glue the pieces together. Apply enough glue to one piece so that when you sandwich the two strips together only the glue remains in between. Wait 24 hours for the glue to fully cure before you continue working. A faster option for bonding the two strips together is to use Acetone. Acetone will melt the acrylic and turn the two pieces into one physical piece. This is the idea in theory, and it may take multiple tries to get it right. One thing to note is that acetone fumes are dangerous and acetone should be used with caution, in a well ventilated area.
With the two strips now one, it will be very helpful for the next couple of steps to cover one or both faces of the acrylic with masking tape. This will allow us to mark where we want to cut, drill, or bend the acrylic.
Two pieces of acrylic glued together
One of the things necessary for a two-axis gimbal to function properly is having the camera perfectly balanced on each axis. Without the modeling and analysis to build a perfectly balanced gimbal from scratch, there will have to be some method of adjusting the positions of the motors and camera. To do this, a slot is cut into the roll arm where the roll motor mounts and another slot into the pitch arm where the pitch motor mounts. The motors will then be adjustable up and down each arm to facilitate balancing the gimbal. The exact method for mounting the motors to the arms with the slot will be discussed later.
To cut the slot a Dremel with a router bit is the preffered tool. The process can be described as a reverse router table. There is a flat surface and a fence, but instead of moving the piece along the fence into the router bit, the piece is secured and the router bit (Dremel) is moved along the fence. This allows for a predictable, measurable, and straight cut slot. If you do not own a Dremel or other rotary tool then the slots can be cut using two holes and a coping saw, or by drilling a series of holes which you can sand down to a slot. I advise cutting the slots before the next step, which is bending the acrylic. It will be miuch easier to work with the piece when it is still flat.
Slot cut into pitch arm. Scrap pieces of acrylic are used to bring the dremel up to the height of the piece to be cut. Carpet tape works great to hold everything in place.
Now that the slot has been cut, it is time to bend the acrylic into the right angle required by the gimbal. Being a thermoplastic, acrylic will soften as it is heated up. For a good bend, the heat needs to be concentrated and controllable. A small tea candle will work just fine, providing a constant heat source that you can move in and out of. Mark a line where you want the bend and hold the acrylic just above the flame while constantly moving back and forth along the bend line. This is necessary to avoid heating one spot for too long and risk over softening the plastic. You'll know if one area is too hot if you see bubbles forming and the surface starts bulging. After some time the acrylic becomes noticeably flexible around the bend area. Once it’s ready carefully try to bend the piece around a ninety-degree form. A chamfer on the edge of the form helps because the acrylic will not easily bend sharply. If you feel the force required to bend the acylic may break it, just heat the piece for longer. It may take multiple reheatings to work up to 90 degrees so be patient and take your time.
Heating the acrylic along the marked bend line. Make sure to keep the piece moving.
Acrylic bent to ninety degrees around a form.
Cutting to Size:
At this point it is important to lay out the motors and camera in order to best assess the final size of each arm. In this case I wanted the arms to be as small as possible while allowing full rotation of the camera on each axis. There is no precise calculations here, just eyeball it and make some marks where it looks like the motors should be located. Once this is done you can drill the motor mount holes according to the mounting pattern of your motors to mount the pitch motor on the roll arm. Now knowing where to mount the motors, you can trim the excess material off of each arm and clean things up.
Laying out the pieces to approximate size.
Arms cut to final length and cleaned up around the edges.
Mounting the Motors:
Now it is time to mount the motors to the arms. This is done through a small, thin, acrylic or metal piece with holes sized to mount the motors. One side of the piece is covered with a thin layer of dried hot glue. The motor mount bolts will pass through this piece, through the slot cut earlier, and into the motor. The hot glue provides the friction necessary to hold the motors in place when the bolts are tightened, while allowing the motors to be moved along the slot in order to make the adjustments needed to balance the gimbal when the bolts are loosened.
Acrylic plate covered with a thin layer of hot glue.
Metal plate covered with a thin layer of hot glue and mounted to the arm and motor.
Mounting the Camera:
Once the motors are secured it is time to secure the camera on to the gimbal. Doing this varies depending on the camera used. To secure my Hero2 I used a Velcro strap with a hand cut acrylic piece that holds the camera by its lens. The Velcro strap is secured to the gimbal in this case using a routed out channel in the pitch arm, but glue or a bolt may also work. Commercial gimbals use many methods to hold the camera, so it is up to you to decide which method works best for your camera. With action cameras like the GoPro, holding the camera by its lens seems to work well, while with larger cameras a larger tray with a mounting bolt may work better. After the camera is secured, the IMU can be attached to the bottom of the pitch arm, the gimbal can be balanced, and tuning can begin.
Gimbal balanced with mounted gimbal.
With a fundamental understanding of gimbal design, it is fairly easy to construct your own two-aixs gimbal from scratch. For those of us without access to 3D printers, acrylic is a great material to work with. The processes used in this build exemplify that acrylic can be glued together into multiple layers, bent into various angles, cut and routed, and used with hot glue. I hope by reading this article you learned how to construct a basic two-axis gimbal, as well as some basic acrylic building techniques required to do so. These ideas can be extended much further to the construction of a three-axis gimbal or any other acrylic parts you desire.
Final gimbal mounted on a pole for hand held use.
Thank you for reading!