A Look Inside A DIY Rocket Motor

September 11, 2024 by Dan Maloney 6 Comments

[Joe Barnard] made a solid propellant rocket motor, and as one does in such situations, he put it through its paces on the test stand. The video below is not about the test, nor is it about the motor’s construction. Rather, it’s a deconstruction of the remains of the motor in order to better understand its design, and it’s pretty interesting stuff.

Somewhere along the way, [Joe], aka “BPS.Space” on YouTube, transitioned from enthusiastic model rocketeer to full-fledged missile-man, and in the process stepped up his motor game considerably. The motor that goes under the knife — or rather, the bandsaw — in this video is his “Simplex V2,” a completely DIY build of [Joe]’s design. For scale, the casing is made from a 6″ (15 cm) diameter piece of aluminum tubing over a meter in length, with a machined aluminum forward closure and a composite nozzle assembly. This is a pretty serious piece of engineering.

The closure and the nozzle are the focus of the video, which makes sense since that’s where most of the action takes place. To understand what happened during the test, [Joe] lopped them off and cut them roughly in half longitudinally. The nozzle throat, which was machined from a slug of graphite, fared remarkably well during the test, accumulating only a little slag from the propellant, a combination of powdered aluminum, ammonium perchlorate, and HTBP resin. The lower part of the nozzle, made from phenolic-impregnated linen, did pretty well too, building up a pyrolyzed layer that acted much like a space capsule’s ablative heat shield would. The forward closure, whose sole job is to contain the inferno and direct the exhaust anywhere but up, took more of a beating but stood up to the challenge. Especially interesting was the state of the O-rings and the way that the igniter interfaced with the closure.

Post mortems like these are valuable teaching tools, and while it must be heartbreaking to destroy something you put so much work into, you can’t improve what you can’t measure. Hats off to [Joe] for the peek inside his world. Continue reading “A Look Inside A DIY Rocket Motor” →

DIY Spacer Increases FDM Flow Rate For Faster, Better Printing

July 12, 2024 by Dan Maloney 8 Comments

The host of problems to deal with when you’re feeling the need for FDM speed are many and varied, but high on the list is figuring out how to melt filament fast enough to accommodate high flow rates. Plus, the filament must be melted completely; a melty outside and a crunchy inside might be good for snacks, but not for 3D printing. Luckily, budget-minded hobbyists can build a drop-in booster to increase volumetric flow using only basic tools and materials.

[aamott]’s booster, which started life as a copper screw, is designed to replace the standard spacer in an extruder, with a bore that narrows as the filament gets closer to the nozzle to ensure that the core of the filament melts completely. Rather than a lathe, [aamott]’s main tool is a drill press, which he used to drill a 0.7 mm bore through the screw using a PCB drill bit. The hole was reamed out with a 10° CNC engraving bit, generating the required taper. After cutting off the head of the screw and cleaning up the faces, he cut radial slots into the body of the booster by threading the blade of a jeweler’s saw into the bore. The result was a bore wide enough to accept the filament on one end, narrowing to a (roughly) cross-shaped profile at the other.

Stacked up with a couple of knock-off Bondtech CHT nozzles, the effect of the booster was impressive — a 50% increase in flow rate. It’s not bad for a prototype made with simple tools, and it looks a little easier to build than [Stefan]’s take on the same idea.

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Deep Dive Into 3D Printing Nozzles

January 18, 2024 by Al Williams 14 Comments

[Lost in Tech] set out to examine a variety of 3D printing nozzles. Before he got there, though, he found some issues. In particular, he found that his current crop of printers don’t take the standard E3D or MK8 nozzles. So, instead, he decided to examine various nozzles under the microscope.

Unsurprisingly, each nozzle had a tiny hole at the end, although the roundness of the hole varied a bit from nozzle to nozzle. As you might expect, more expensive nozzles had better orifices than the cheap ones. Grabbing pictures of nozzles at magnification isn’t easy, so he set up a special image stacking setup to get some beautiful images (and he has another video on how that works).

But the real star of the video is when he virtually travels into the orifice to show the innermost details of the nozzle from the inside out. This let him visualize the smoothness and finish. The Creality nozzles looked very good and weren’t terribly expensive. Many of the expensive nozzles were quite good. However, as you would expect, the quality of cheap nozzles were all over the place.

By the end, [Lost in Tech] speculates if the non-standard nozzles are a way to prevent you from buying low-cost nozzles and eating into sales or if they are a way to prevent you from buying low-cost nozzles that may give you poor print quality. What do you think?

There’s more than one way to look inside a nozzle. We just buy our nozzles, but some people make their own.

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Printed Gas Can Accessories Make Refueling A Little Neater

April 26, 2023 by Dan Maloney 44 Comments

No matter what your position is on internal combustion engines, it’s pretty safe to assume everyone is on the same page regarding wasting fossil fuels: it’s a bad thing. And nothing is as frustrating as spilling even a drop of the precious stuff before you even get a chance to burn it.

Unfortunately, the design of gas cans, at least here in North America, seems to have been optimized for fuel spillage. Not willing to settle for that, [avishekcode] came up with a 3D-printable replacement nozzle that should make dispensing gas a bit neater. It’s designed to fit one of the more popular brands of gasoline jugs available here in the States, and rather than the complicated stock nozzle, which includes a spring-operated interlock that has to be physically forced into a filler neck to open the valve, the replacement is just a slender tube with a built-in air vent. The vent keeps a vacuum from forming in the gas can and makes for a smooth, easy-to-control flow of gas and less spillage. The video below shows it in action.

The obvious issue here is chemical compatibility, since gasoline doesn’t work and play well with all plastics. [avishekcode] reports that both PLA and PETG versions of the nozzle have performed well for up to two years before cracking enough to need replacement. And then, of course, the solution is just to print another one. There may be legal issues, too — some localities have ordinances regarding gasoline storage and dispensing, so it’s best to check before you print.

Of course, one way to avoid the problems associated with storing and dispensing gasoline is to convert to electric power tools and vehicles. But as we’ve seen, that presents other problems.

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Go Big Or Go Home: 0.6 Mm Nozzles Are The Future

July 29, 2022 by Al Williams 51 Comments

Most desktop fused deposition modeling (FDM) 3D printers these days use a 0.4 mm nozzle. While many people have tried smaller nozzles to get finer detail and much larger nozzles to get faster printing speed, most people stick with the stock value as a good trade-off between the two. That’s the conventional wisdom, anyway. However, [Thomas Sanladerer] asserts that with modern slicers, the 0.4 mm nozzle isn’t the best choice and recommends you move up to 0.6 mm.

If you know [Thomas], you know he wouldn’t make a claim like that without doing his homework. He backs it up with testing, and you can see his thoughts on the subject and the test results in the video below. The entire thing hinges on the Ultimaker-developed Arachne perimeter generator that’s currently available in the alpha version of PrusaSlicer.

We’ve experimented with nozzles as small as 0.1 mm and, honestly, it still looks like an FDM 3D print and printing takes forever at that size. But these days, if we really care about the detail we are probably going to print with resin, anyway.

There are a few slicer settings to consider and you can see the whole setup in the video. The part where an SLA test part is printed with both nozzles is particularly telling. This is something that probably shouldn’t print well with an FDM at all. Both nozzles had problems but in different areas.

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Cleaner Laser Cutting With A 3D-Printed Nozzle

November 25, 2020 by Donald Papp 24 Comments

[Nervous System] does a lot of laser cutting, and [Jesse] shared a fascinating experimental improvement to their laser cutter that consists of a 3D-printed nozzle for cleaner cuts. You can see the results for yourself above, where the difference between the two cuts is striking.

[Jesse]’s modification doesn’t affect the laser beam itself; it is an improvement on the air assist, which is the name for a constant stream of air that blows away smoke and debris as the laser burns and vaporizes material. An efficient air assist is one of the keys to getting nice clean laser cuts, but [Jesse] points out that a good quality air assist isn’t just about how hard the air blows, it’s also about how smoothly it does so. A turbulent air assist can make scorch marks worse, not better.

3D-printed nozzle to promote laminar air flow on the left, stock nozzle on the right.

As an experiment to improve the quality of the air flowing out the laser nozzle, [Jesse] researched ways to avoid turbulence by creating laminar flow. Laminar flow is the quality of a liquid having layers flowing past one another with little or no mixing. One way to do this is to force liquid through individual, parallel channels as it progresses towards a sharply-defined exit nozzle. While [Jesse] found no reference designs of laminar flow nozzles for air assists, there were definitely resources on making laminar flow nozzles for water. It turns out that interest in such a nozzle exists mainly as a means of modifying Lonnie Johnson’s brilliant invention, the Super Soaker.

Working from such a design, [Jesse] created a custom nozzle to help promote laminar flow. Sadly, a laser cutter head carries design constraints that make some compromises unavoidable; one is limited space, and another is the need to keep the laser’s path unobstructed. Still, after 3D printing it in rigid heat-resistant resin, [Jesse] found a dramatic improvement in the feel of the air exiting the nozzle. Some test cuts confirmed a difference in performance, which results in a noticeably cleaner kerf without scorching around the edges.

One of the things [Nervous System] does is make their own custom puzzles, so any improvement to laser cutting helps reliability and quality. When production is involved, just about everything matters; a lesson [Nervous System] shared when they discussed making the best plywood for creating their puzzles.

Unconventional Drone Uses Gas Thrusters For Control

June 8, 2019 by Dan Maloney 28 Comments

You’ve got to hand it to [Tom Stanton] – he really thinks outside the box. And potentially outside the atmosphere, to wit: we present his reaction control gas thruster-controlled drone.

Before anyone gets too excited, [Tom] isn’t building drones for use in a vacuum, although we can certainly see a use case for such devices. This is more of a hybrid affair, with counter-rotating props mounted in a centrally located duct providing the lift and the yaw control. Flanking that is a triangular frame supporting three two-liter soda bottle air reservoirs, each of which supplies a down-firing nozzle at each apex of the triangle. Solenoid valves control the flow of compressed air from the bottles to the nozzles, providing thrust to stabilize the roll and pitch axes. As there aren’t many off-the-shelf flight control systems set up for reaction control, [Tom] had to improvise thruster control; an Arduino watches the throttle signals normally sent to a drone’s motors and fires the solenoids when they get to a preset threshold. It took some tuning, but [Tom] was eventually able to get a stable, untethered hover. And he’s right – the RCS jets do sound amazing when they’re firing, as long as the main motors are off.

This looks as though it has a lot of potential, and we’d love to see it developed more. It reminds us a bit of this ducted-prop drone, another great example of stretching conventional drone control concepts to the limit.

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