Carbon Fiber And Kevlar Make This Linear Actuator Fast And Strong

May 3, 2023 by Dan Maloney 9 Comments

When it comes to the “build versus buy” question, “buy” almost always wins. The amount of time you have to put into building something is rarely justified, especially with a world of options available at the click of a mouse.

That’s not always the case, of course. These custom-made linear actuators are a perfect example of when building your own wins. For a planned ball-juggling robot, [Harrison Low] found himself in need of linear actuators with long throw distance, high speed, and stiff construction. Nothing commercially available checked all the boxes, so he set out to design his own.

A few design iterations later, [Harrison] arrived at the actuators you see in the video below. Built mainly from carbon fiber tubing and 3D-printed parts, the actuators have about 30 centimeters of throw, and thanks to their cable-drive design, they’re pretty fast — much faster than his earlier lead screw designs. The stiffness of the actuator comes by way of six bearings to guide the arm, arranged in two tiers of three, each offset by 60 degrees. Along with some clever eccentric spacers to fine-tune positioning, this design provides six points of contact that really lock the tube into place.

The cable drive system [Harrison] used is pretty neat too. A Kevlar kite string is attached to each end of the central tube and then through PTFE tubes to a pulley on an ODrive BLDC, which extends and retracts the actuator. It’s a clever design in that it keeps the weight of the motor away from the actuator, but it does have its problems, as [Harrison] admits. Still, the actuator works great, and it looks pretty cool while doing it. CAD and code are available if you want to roll your own.

These actuators are cool enough, but the real treat here will be the ball juggler [Harrison] is building. We’ve seen a few of those before, but this one looks like it’s going to be mighty impressive.

Continue reading “Carbon Fiber And Kevlar Make This Linear Actuator Fast And Strong” →

Building Forged Carbon Fiber Wings For Radio Control Cars

February 2, 2022 by Lewin Day 6 Comments

When it comes to building decent aerodynamic devices, you want to focus on getting your geometry accurate, and making sure your parts are strong enough to deal with the force they’re generating. This build from [Engineering After Hours] delivers on those fronts, consisting of a high-downforce wing for a small RC car.

The video points out that, at best, even a decent RC car will have pretty crappy aerodynamic parts from the factory, with a lift-to-drag (L/D)ratio of 2-3:1 at best. This means that, while they may create some small amount of downforce, they’re also creating plenty of drag at the same time.

The dual-element wing designed here is much more efficient, hitting an L/D ratio in the vicinity of 17:1 – a huge improvement. Even a casual eye can note that the design looks a lot more like something you’d see on a full-size car, versus some of the whackier designs seen on toys.

The wing is built with a forged carbon fiber process using 3D-printed molds, to give the wing plenty of strength. Given that it’s built for an RC car that can do over 100 mph, making sure the wing is stiff enough to perform at speed is key.

[Engineering After Hours] does a great job of showing how to prepare the molds, fill them with carbon fiber, and pour the resin, and discusses plenty of useful tips on how to achieve good results with the forged carbon process.

The result is an incredibly impressive rear wing with aerodynamic performance to match its good looks. It may be more complicated than 3D printing, but the results of the work are that much tougher.

We’ve seen other aero experiments from [Engineering After Hours] before, too. Video after the break.

Continue reading “Building Forged Carbon Fiber Wings For Radio Control Cars” →

Electroplating Carbon Fibers Can Have Interesting Results

October 15, 2021 by Lewin Day 17 Comments

Typically, electroplating is used to put coatings of one metal upon another, often for reasons of corrosion protection or to reduce wear. However, other conductive materials can be electroplated, as demonstrated by [Michaɫ Baran].

Finer details are sparse, but [Michaɫ’s] images show the basic concept behind producing a composite metal material hand sculpture. The initial steps involve 3D printing a perforated plastic shell of a hand, and stuffing it with carbon fibers. It appears some kind of plastic balls are also used in order to help fill out the space inside the hand mold.

Then, it’s a simple matter of dunking the plastic hand in a solution for what appears to be copper electroplating, with the carbon fiber hooked up as one of the electrodes. The carbon fibers are then knitted together by the copper attached by the electroplating process. The mold can then be cut away, and the plastic filling removed, and a metal composite hand is all that’s left.

[Michaɫ] has experimented with other forms too, but the basic concept is that these conductive fibers can readily be stuffed into molds or held in various shapes, and then coated with metal. We’d love to see the results more closely to determine the strength and usefulness of the material.

Similar techniques can be used to strengthen 3D printed parts, too. If you’ve got your own ideas on how to best use this technique, sound off below. If you’ve already done it, though, do drop us a line!

[Thanks to Krzysztof for the tip]

Robot Arm Adds Freedom To 3D Printer

May 25, 2021 by Bryan Cockfield 6 Comments

3D printers are an excellent tool to have on hand, largely because they can print other tools and parts rapidly without needing to have them machined or custom-ordered. 3D printers have dropped in price as well, so it’s possible to have a fairly capable machine in your own home for only a few hundred dollars. With that being said, there are some limitations to their function but some of them can be mitigated by placing the printer head on a robot arm rather than on a traditional fixed frame.

The experimental 3D printer at the University of Nottingham adds a six-axis robotic arm to their printer head, which allows for a few interesting enhancements. Since the printer head can print in any direction, it allows material to be laid down in ways which enhance the strength of the material by ensuring the printed surface is always correctly positioned with respect to new material from the printer head. Compared to traditional 3D printers which can only print on a single plane, this method also allows for carbon fiber-reinforced prints since the printer head can follow non-planar paths.

Of course, the control of this printer is much more complicated than a traditional three-axis printer, but it is still within the realm of possibility with readily-available robotics and microcontrollers. And this is a hot topic right now: we’ve seen five-axis 3D printers, four-axis 3D printers, and even some clever slicer hacks that do much the same thing. Things are finally heating up in non-planar 3D printing!

Thanks to [Feinfinger] for the tip!

Continue reading “Robot Arm Adds Freedom To 3D Printer” →

Techniques For Making Complex Carbon Fibre Tube Parts

July 18, 2020 by Lewin Day 19 Comments

Many a hacker spent their high school years picking up a few new skills in workshop classes. Whether it be woodworking, welding, or the patient, delicate skill of technical drawing, they’ve been a mainstay of secondary education for decades. However, composites are new enough that they aren’t a major feature of the curriculum. For those wishing to fill in a few gaps, [Easy Composites] have some great videos on carbon fibre techniques.

The video in question concerns the manufacture of a complex cross-section tube part, but these techniques can also apply to more complex hollow sections, like a bike frame, for example. Starting with a mold, the first step is to cut a rough template. This is then used to lay down the first layer of pre-preg carbon fibre material, and a more accurate template is made. The rest of the steps involve the production of a secure lap joint between subsequent layers, and how to properly use vacuum bag techniques on hollow parts.

It’s a useful primer on the basics of producing hollow carbon fibre parts with prepreg material. We’ve featured composites before, with this bulletproof armor a particularly good example. Video after the break.

Continue reading “Techniques For Making Complex Carbon Fibre Tube Parts” →

Flywheel Stores Energy To Power An Airplane – Eventually

February 13, 2020 by Dan Maloney 7 Comments

Question: Can a flywheel store enough energy to power an airplane? Answer: Yes it can, for certain values of “flywheel” and “airplane.”

About the only person we can think of who would even attempt to build a flywheel-powered airplane is [Tom Stanton]. He’s a great one for off-the-wall ideas that often pay off, like his Coandă effect hovercraft, as well as for ideas that never got far off the ground, or suddenly met it again. For most of the video below, it seems like his flywheel-powered plane is destined to stay firmly in the last category, and indeed, the idea of a massive flywheel taking flight seems counterintuitive. But [Tom] reminds us that since the kinetic energy stored by a flywheel increases as the square of angular velocity, how fast it’s turning is more important than how massive it is. The composite carbon fiber and aluminum flywheel is geared to the propeller of a minimal airplane through 3D-printed bevel gears, and is spun up with an external BLDC motor.

Sadly, the plane never made it very far, no matter how much weight was trimmed. But [Tom] was able to snatch victory from the jaws of defeat by making the propeller the flywheel – he printed a ring connecting the blades of the prop and devised a freewheel clutch to couple it to the motor. The flywheel prop stored enough energy to complete a few respectable flights, as well as suffer a few satisfyingly spectacular disintegrations.

As always, hats off to [Tom] for not being bashful about sharing his failures so we can all learn, and for the persistence to make his ideas take flight.

Continue reading “Flywheel Stores Energy To Power An Airplane – Eventually” →

Stronger 3D Prints — Glue Or Carbon Fiber?

December 28, 2019 by Al Williams 31 Comments

[CNCKitchen], like many others, is looking to make strong 3D prints. Using a high tech PLA bio copolyester compound, he printed a bunch of hooks in two different orientations. He used several different types of glue including epoxy and superglue. You can see the video of his results, below.

In addition to the glue, he used epoxy and bulk carbon fiber, again, in two different orientations. After several days of curing, he was ready to test.

Continue reading “Stronger 3D Prints — Glue Or Carbon Fiber?” →