Since I've begun to gather attachments for my GoPro camera, I've discovered a large gap between what types of attachments can be used and what's available. In my last Instructable, I was bemoaning the lack of 2 legged attachments that could be used with 3 legged ones.
I also attempted to correct the awkward attachment of the GoPro handlebar mount, which is fine for its intended use, but becomes a pain when frequent attachment and removal is happening. My solution wasn't very elegant and has been eating at me a bit.
This Instructable addresses both of these issues, and does it in a way that 3/D printing is well suited for.
A couple of years ago, I experimented with printing a working hinge in one step. I used my results to print a wire clip that's been very useful in several of my projects. I went on to experiment with strength and the smallest hinge I could reliably print and gathered a lot of useful information, which I've been able to put to use here.
So let's get started:
Step 1: The Parts
Twenty thousandths of an inch. That's the number to remember for printed hinges. Keep that amount of space between working parts on a consumer grade fused deposition printer and your hinges will work right off the bed. No assembly needed.
When you remove one of these printed hinges from the printer, it wont work right off the bat. It'll come out as one solid part. But don't panic, that's how they're supposed to start out.
The GoPro clamp uses that type of hinge, but it isn't exactly a single piece. It uses two additional parts that hold it to equipment and also makes use of a separate metal axle.
The reason for these modifications is strength. Because of the grain effect of the built-up part, the wings used to mount the clamp would have the grain going in the wrong direction, causing them to be the weak link in the design. The axle is metal for the same reason. I used .085" stainless spring wire, but any tough metal .062" diameter or greater should provide enough strength and surface area to work and keep the parts from breaking apart under the stress of clamping a camera and other attachments to a bar.
You'll also need to gather a special GoPro thumbscrew with nut, and a bolt long enough to allow it to swing free. So its not exactly a single piece, but the critical hinge portion is already in position, just waiting for the axle to be inserted.
Update: After playing around with this, I've improved the print quality by adding supports beneath the curved ends of the printed clamp. These are easily snapped off after printing. I've also been unable to find the special handlebar mount thumbscrew (with nut) I've mentioned here, so I've added one to the print as well. The thread size GoPro specifies is 10/24, but 8mm seems to work almost as well.
Step 2: Assembly
Once the clamp parts have been printed, begin by cutting a bit of wire equal in length to the clamp's thickness. The clamp is .686" thick, but don't obsess; anything close to that length should work.
The next measurement is more critical however. Match your wire's diameter to a drill of equal diameter. If one can't be found, use the closest smaller sized drill. You want the wire to fit snugly. It'll be better to force the wire through the plastic than have it too loose.
You'll see a dimple on one side of the clamp. This is where you'll drill perpendicularly all the way through. Round one end of the wire to help it get through, and using a vise, push it through the hole. Don't knock it through with a hammer. You want the plastic to grip the wire as tightly as it can. Shocking it won't help it to do that. Once the vise has pushed the wire as far as it can, gently tapping with a small hammer to flush the wire out will be all the hammering it needs.
Step 3: The Fun Part
This is where the magic happens.
At the moment, the clamp is a solid piece of plastic with a wire going through it. But inside, around the portions that separate the two halves there are .020" gaps (remember those?). These gaps have been locked together by the deposited layer of plastic that was laid down just above them. The extruded plastic droops down and fuses with the plastic at the bottom of the gap. These "threads" don't make a very strong bond, so they're the first things that'll break when force is applied.
Grip the clamp as shown and squeeze. It may take some effort, but as soon as you overcome the strength of the plastic threads, you'll hear a "snap" and the two halves will come together. Open and close the clamp a couple of times and you'll be ready to finish your project and put it to use.
First, you'll need to cement the two "wings" in place. I make a little puddle of acetone in a shallow saucer and set the base of each wing into it, letting it sit for several seconds. This gives the acetone time to begin softening the plastic. You don't want it to get mushy, just soft enough so when you press fit the parts together they fuse and become one. Once that's done, set your work aside to dry.
While waiting for the glue to dry, think through how you'll be using this clamp. You'll notice the clamp has two holes at the open end for the bolt and thumbscrew. You can leave things as they are, or choose which side you want your thumbscrew to slip out of and grind a slot on that that side as shown here. Leaving both of these holes in as they are will require the complete removal of the thumbscrew to open the clamp. You may have some situation where that's desirable, so consider it. Likewise, if you decide to make a slot in one of the holes, the side of the clamp the slot is on and the way the thumbscrew faces is also a choice I can't make for you, Customize it as you see fit. FYI I've placed mine so the thumbscrew faces down, but that also required me to replace the standard GoPro acorn nut on the Camera-to-GoPro fitting over to a standard nut to allow clearance.
No matter how you set the thumbscrew up, this clamp only requires the one thumbscrew to open and close. The thumbscrew doesn't have to be moved far to clear the lip around the slot and both the thumbscrew and top half of the clamp swing out of the way. I'll be using mine to hold my gimbal in place. The gimbal's handle is the same size as a bicycle's handlebar, making this the perfect accessory for it. I'll be able to quickly mount and remove it and not worry about dropping thumbscrews or clamp halves.
I'm pretty proud of myself:)