Day: October 24, 2019

The Blessings And Destruction Wrought By Lead Over Millennia

October 24, 2019 by 120 Comments

Everyone one of us is likely aware of what lead — as in the metal — is. Having a somewhat dull, metallic gray appearance, it occupies atomic number 82 in the periodic table and is among the most dense materials known to humankind. Lead’s low melting point and malleability even when at room temperature has made it a popular metal since humans first began to melt it out of ore in the Near East at around 7,000 BC in the Neolithic period.

Although lead’s toxicity to humans has been known since at least the 2nd century BC and was acknowledged as a public health hazard in the late 19th century, the use of lead skyrocketed in the first half of the 20th century. Lead saw use as a gasoline additive beginning in the 1920s, and the US didn’t abolish lead-based paint until 1978, nearly 70 years after France, Belgium and Austria banned it.

With the rise of consumer electronics, the use of lead-based solder became ever more a part of daily life during the second part of the 20th century, until an increase in regulations aimed at reducing lead in the environment. This came along with the World Health Organization’s fairly recent acknowledgment that there is truly no safe limit for lead in the human body.

In this article I’ll examine the question of why we are still using lead, and if we truly must, then how we can use this metal in the safest way possible.

Continue reading “The Blessings And Destruction Wrought By Lead Over Millennia” →

Student-Built Rocket Engine Packs A Punch

October 24, 2019 by 30 Comments

A group of students at Boston University recently made a successful test of a powerful rocket engine intended for 100km suborbital flights. Known as the Iron Lotus (although made out of mild steel rather than iron), this test allowed them to perfect the timing and perfect their engine design (also posted to Reddit) which they hope will eventually make them the first collegiate group to send a rocket to space.

Unlike solid rocket fuel designs, this engine is powered by liquid fuel which comes with a ton of challenges to overcome. It is a pressure-fed engine design which involves a pressurized unreactive gas forcing the propellants, in this case isopropanol and N2O, into the combustion chamber. The team used this design to produce 2,553 lb*ft of thrust during this test, which seems to be enough to make this a class P rocket motor. For scale, the highest class in use by amateurs is class S. Their test used mild steel rather than stainless to keep the costs down, but they plan to use a more durable material in the final product.

The Boston University Rocket Propulsion Group is an interesting student organization to keep an eye on. By any stretch of the imagination they are well on their way to getting their rocket design to fly into space. Be sure to check out their other projects as well, and if you’re into amateur rocketry in general there are a lot of interesting things you can do even with class A motors.

Continue reading “Student-Built Rocket Engine Packs A Punch” →

Retro Hardware Plots Again Thanks To Grbl And ESP32

October 24, 2019 by 11 Comments

When it comes to building a new CNC machine, you’ve got a wide world of controller boards to choose from. Whether you’re building a 3D-printer or a CNC plasma cutter, chances are good you’ll find a controller that fits your needs and your budget. Not so much, though, when you want to add CNC to a pen plotter from the early days of the PC revolution.

[Barton Dring] just posted the last installment of a five-part series in which he documented putting an Atari 1020 plotter under CNC control. The plotter was a peripheral for the Atari line of 6502 machines from the late 1970s; the guts of the little roll-fed, ballpoint-pen plotter appeared in Commodore, Tandy, and TI versions as well. [Bart]’s goal was to not add or modify anything to the mechanically simple device apart from the controller. That was easier said than done, given the unipolar stepper motors controlling the pen position and paper roll, and the fact that the pen lift mechanism uses a solenoid. Support for those had to be added to his Grbl_ESP32 firmware, as did dealing with the lack of homing switches in the plotter, and adapting the Grbl tool change command to the pen color change mechanism, which rotates the pen holder by bumping it into the right-hand carriage stop. The stock controller was replaced by a custom PCB that fits perfectly within the case, with plenty of room to spare. The video below shows it plotting out a vexillogically relevant sample.

From custom coasters to wooden nickels to complex string art, [Bart] has really put Grbl through the wringer. We really like this retro-redo, though, and fully support his stated desire to convert more old hardware to Grbl_ESP32.

Continue reading “Retro Hardware Plots Again Thanks To Grbl And ESP32” →