Saturday, July 1
Custom Aluminum Wheels Teach a Thing or Two about Casting
For some mobile projects like small carts or rolling cabinets, your standard casters from Harbor Freight will do just fine. But some projects need big, beefy wheels, and these custom cast aluminum wheels certainly make a statement. Mostly, “Watch your toes!”
To be honest, [Brian Oltrogge]’s wheels are an accessory in search of a project, and won’t be crushing feet anytime soon. He made them just to make them, but we have no beef with that. They’ve got a great look that hearkens back to a time when heavy metal meant something else entirely, and things were made to last. Of course, being cast from aluminum sort of works against that, but there are practical limits to what can be done in the home foundry. [Brian] started with a session of CAD witchcraft followed by machining the cores for his molds. Rather than doing this as lost foam or PLA, he milled the cores from poplar wood. His sand mix is a cut above what we usually see in home-brew sand casting — sodium silicate sand that can be cured with carbon dioxide. All his careful preparation meant the pour went off without a hitch, and the wheels look great.
We’ve featured quite a few metal casting projects recently, some that went well and some that didn’t. [Brian] looks like he knows what he’s doing, and we appreciate the workmanship that he puts on display here.
[via r/metalworking]
Filed under: tool hacks
Launch Pad for Air-Water Rockets is Good Clean Fun for STEM Students
We have fond memories of air-water rockets, which were always a dime store purchase for summertime fun in the pool. Despite strict guidance from mom to shoot them only straight up, the first target was invariably a brother or friend on the other side of the pool. No eyes were lost, and it was good clean fun that was mercifully free of educational value during summer break.
There are many ways to launch an air-water rocket, from the simple to the complex. [Robert]’s build leans toward the complex, but looks robust enough for repeated use and makes the launch process routine so the kids can concentrate on the aerodynamics. Or to just enjoy being outdoors and watching things fly.
Filed under: misc hacks
TMS9900 Retro Build
[Robert Baruch] found a TMS9900 CPU from 1983 in a surplus store. If that name doesn’t ring a bell, the TMS9900 was an early 16-bit CPU from Texas Instruments. He found that, unlike modern CPUs, the chip took several voltages and a four-phase twelve-volt clock. He decided to fire it up and — of course — one thing led to another and he wound up with a system on a breadboard. You can see one of the videos he made about the machine below.
This CPU had some odd features, most notably that it stored its registers in off-chip memory and can switch contexts by changing where the registers reside. That was a novel idea when the memory and the CPU were similar in speed. In a modern computer, the memory is much slower than the CPU and this would be a major bottleneck for program execution. The only onboard registers were the program counter, the status register, and a pointer to the general-purpose registers in memory.
[Robert] doesn’t quite have a full system yet, but we bet he’ll get there. He built a four-digit display and did some simple control line decoding of the processor. He can watch the address bus and also manages to single step. The TMS9900 used dynamic logic, so you can’t just halt the clock. However, there is a way to do it with a state machine [Robert] built with some flip flops and an ATmega processor.
To overcome the fast memory problem, TI’s TI-99/4 home computer only had 128 words of memory directly addressable. Main program storage was cheaper and slower dynamic RAM (16 K bytes) that you could only access via the display controller. This meant performance suffered. If you had the optional floppy controller, you got extra RAM, but that was pricey in the day.
We recently saw a TI 99/4A doing service as a weather station. If [Robert] duplicates the TI-99/4 display system, maybe he can run this demo. We are waiting to see where [Robert] takes his surplus store find from here.
Filed under: Microcontrollers
3D-Printed Halbach Motor Part Two: Tuning, Testing
Building your own Halbach-effect brushless DC motor is one thing. Making sure it won’t blow up in your face another matter, and watching how [Christoph Laimer] puts his motor to the test is instructive.
You’ll remember [Christoph]’s giant 3D-printed BLDC motor from a recent post where he gave the motor a quick test spin. That the motor held together under load despite not being balanced is a testament to the quality of his design and the quality of the prints. But not wishing to tempt fate, and having made a few design changes, [Christoph] wisely chose to perform a static balancing of the rotor. He also made some basic but careful measurements of the motor’s parameters, including the velocity constant (Kv) using an electric drill, voltmeter, and tachometer, and the torque using a 3D-printed lever arm and a kitchen scale. All his numbers led him to an overall efficiency of 80%, which is impressive.
[Christoph] is shipping his tested BLDC off to the folks at FliteTest, where he hopes they put it to good use. They probably will — although they might ask for three more for a helicarrier.
Filed under: misc hacks
The U.S. government is removing scientific data from the internet
Ars Live is filmed by Chris Schodt and produced by Jennifer Hahn. (video link)
In our latest episode of Ars Technica Live, Ars editors Annalee Newitz and Joe Mullin talked to UC Santa Cruz sociology professor Lindsey Dillon about how the Trump Administration has been removing scientific and environmental data from the Web. Lindsey is part of a group called Environmental Data Governance Initiative (EDGI), which is working on ways to rescue that data and make it available to the public.Lindsey told us how EDGI got started in November 2016, within days of the presidential election. Its founders are scientists and academics whose main goal was to make sure that researchers and citizens would continue to have access to data about the environment. They organized data rescue events around the country, where volunteers identified vulnerable climate information on websites for several government agencies, including the EPA, DOE, and even NASA. The Internet Archive helped by creating digital records of all the at-risk pages.
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Gateway to Metal Casting
Casting is an exciting and very useful pastime, but it’s not exactly common these days. That’s a problem whether you’re just getting started or have been doing it for years: everyone can use the advice of another. Fear not! The US Department of Energy is here to help with the Industrial Metal’s Program’s Metal Casting cornucopia.
Although not strictly a hack, this is certainly a facilitator of hacks and any experienced user would do themselves some good by perusing the site. Click on the maps to find complex issues presented remarkably well for papers at this level of rigor. Seriously, check them out.
However, since these papers go into such depth, we can’t really say the material is beginner friendly. That’s not to say it would be bad for a newbie to read through, just that it might be a bit discouraging. But, if you need to figure out where to start in the maze of molds and sand and molten metal, we might have some articles that might help you out.
Do y’all know of any good casting resources on the interwebs? If so, leave ’em in the comments!
Thanks [RunnerPack] for sending this in.
Filed under: how-to
