Repair Hacks

593 Articles

3D Print The Blasphemous Helicopter Part Known As A Jesus Nut

January 27, 2018 by 17 Comments

Today, when we say “Jesus nut”, we’re not referring to the people who spend their days proselytizing down at the mall. The term, likely spawned in the Vietnam war, refers to the main nut holding the rotors on to the mast of a helicopter which is in the shape of the Christian cross. If the “Jesus nut” was to fail, the rotors would detach from the craft, and there would be little for crews to do except to pray.

[Marius] was presented with a failed Jesus nut, though thankfully from an R/C helicopter, meaning there was no loss of life. A friend needed the part replaced for their FQ777 copter, so it was time to bust out the 3D printer and get to work.

The first step was to reconstruct the broken piece so it could be measured and then modeled in CAD software with the help of calipers to determine the original dimensions. What followed will be familiar to many 3D printing enthusiasts — a case of educated trial and error, experimenting with different filaments and print settings until a usable part was produced. [Marius] notes on the part’s Thingiverse page  that they achieved the best print with an 0.2mm layer height, and printing two parts at once to allow the layers more time to cool during each pass. It was then a simple matter of tidying up the part with sandpaper and a drill bit before installing it on the vehicle.

[Marius] reports that the part was successful, being both strong enough to withstand the forces involved as well as having a fit that was just right to suit the rotor pin which needs to be able to turn freely within the Jesus nut. While they’re not always the right tool for the job, 3D printed replacement parts can sometimes surprise you. These prints that are used in repair work often don’t attract the same interest as printing cosplay armor, kinetic art, and low-poly Pokemon. But they quickly prove how transformative having a 3D printer, and the skills to use it, are. That’s why we’re running the Repairs You Can Print contest… take a few minutes to show off the really useful repairs you’ve pulled off with your 3D printer!

Vintage Logan Lathe Gets 3D Printed Gears

January 13, 2018 by 34 Comments

In December 2016, [Bruno M.] was lucky enough to score a 70+ year old Logan 825 lathe for free from Craigslist. But as you might expect for a piece of machinery older than 95% of the people reading this page, it wasn’t in the best of condition. He’s made plenty of progress so far, and recently started tackling some broken gears in the machine’s transmission. There’s only one problem: the broken gears have a retail price of about $80 USD each. Ouch.

On his blog, [Bruno] documents his attempts at replacing these expensive gears with 3D printed versions, which so far looks very promising. He notes that usually 3D printed gears wouldn’t survive in this sort of application, but the gears in question are actually in a relatively low-stress portion of the transmission. He does mention that he’s still considering repairing the broken gears by filling the gaps left by the missing teeth and filing new ones in, but the 3D printed gears should at least buy him some time.

As it turns out, there’s a plugin available for Fusion 360 that helpfully does all the work of creating gears for you. You just need to enter in basic details like the number of teeth, diametral pitch, pressure angle, thickness, etc. He loaded up the generated STL in Cura, and ran off a test gear on his delta printer.

Of course, it didn’t work. Desktop 3D printing is still a finicky endeavour, and [Bruno] found with a pair of digital calipers that the printed gear was about 10% larger than the desired dimensions. It would have been interesting to find out if the issue was something in the printer (such as over-extrusion) or in the Fusion 360 plugin. In any event, a quick tweak to the slicer scale factor was all it took to get a workable gear printed on the third try.

This isn’t the first time we’ve seen 3D printed gears stand in for more suitable replacement parts, nor the first time we’ve seen them in situations that would appear beyond their capability. As 3D printer hardware and software improves, it seems fewer and fewer of the old caveats apply.

Continue reading “Vintage Logan Lathe Gets 3D Printed Gears” →

Repairing A Macbook Charger… With A Pistachio Nut

January 4, 2018 by 61 Comments

Laptop chargers face a hard life. They’re repeatedly plugged and unplugged, coiled up, stuffed into bags, thrown around, and just generally treated fairly poorly. Combine this with fairly lightweight design and it’s not uncommon for a laptop charger to fail after a few years. It’s usually the connector that goes first. Such was the case when I found myself face to face with a failed Macbook charger, and figured it’d be a simple fix. Alas, I was wrong.

Unlike most PC manufacturers, who rely on the humble barrel jack and its readily available variants, Apple liked to use the Magsafe connector on its Macbook line. This connector has many benefits, such as quick release in the event someone trips over the cable, and the fact that it can be plugged in without regard to orientation. However, it’s not the easiest to fix. When the charger began failing, I noticed two symptoms. The first was that the charger would only function if the cable was held just so, in exactly the right orientation. The other, was that even when it would charge, the connector would become very hot. This led me to suspect an intermittent connection was the culprit, and it was quite a poor one at that; the high resistance leading to the heat issue.

It’s at this point with any other charger that you get out your trusty sidecutters, lop the end off, and tap away at Digikey to get a replacement part on the way. With Magsafe? No dice. Replacement parts simply aren’t available — a common problem with proprietary connectors. I endeavoured to fix the problem anyway. I began to strip away the metal shell around the back of the connector with my sidecutters, and eventually an angle grinder. A Dremel would have been the perfect tool for the job, actually, but I persevered regardless. After much consternation, I had the connector peeled back and was able to identify the problem.

Continue reading “Repairing A Macbook Charger… With A Pistachio Nut” →

60’s Comedy Rescued From Nigerian Basement

January 2, 2018 by 27 Comments

In the sixties, videotape used to film television programs was expensive. When a program had been shown as many times as the contract required the tape was wiped and reused, unless someone requested it be saved for some reason. At least, this was the BBC’s doctrine. Many episodes of the BBC’s programs have gone missing due to this reuse of the videotapes but sometimes the films of these episodes are found in an attic or storage facility. [Cplamb] brings us the story of the salvation of some episodes of British comedians Morecambe and Wise’ first series on the BBC, their first color series.

Do make duplicates, the BBC would film a television playing one of the videotapes. This film duplicate would be sent out to television stations around the world, rather than the tapes. The Morecambe and Wise film was found in the humid basement of a television station in Nigeria. Due to the conditions, the film was “diseased” and was in danger of decomposing into soup.

A series of hacks was used to restore the episodes from the rotting film stock. X-ray microtomography was used to scan a roll of film to see if this could be used. This worked because the film has a layer of silver oxide emulsion(the image) on one side and plastic (the film stock) on the other. A program was written so that the resulting voxels could be remapped into two dimensions in order to see the original frame. However, the volume that the machine could x-ray was small – using it on an item the size of a full roll of film would probably destroy the film, if it could be done. The next hack was to cut the film into small blocks using a laser cutter. This itself seems destructive but if you can either cut it up and scan it or let it turns into soup the choice is easy.

A second part of the story has been published, but the third article in the series hasn’t been yet, so we don’t know how the resulting film looks. But this is a pretty cool story involving scanning, x-rays, programming, and laser cutters — all hallmarks of the great hacks we see on Hackaday. Check out this article on the mechanics of film projection and this one on automatically scanning 8mm film for similar style hacks.

Custom PCB Revives A Vintage Tree Stand

January 1, 2018 by 5 Comments

After 56 years, [Jeff Cotten]’s rotating Christmas tree stand had decided enough was enough. While its sturdy cast aluminum frame was ready for another half-century of merriment, the internal mechanism that sent power up through the rotating base had failed and started tripping the circuit breaker. The problem itself seemed easy enough to fix, but the nearly 60 year old failed component was naturally unobtanium.

But with the help of his local makerspace, he was able to manufacture a replacement. It’s not exactly the same as the original part, and he may not get another 56 years out of it, but it worked for this season at least so that’s a win in our books.

The mechanism inside the stand is fairly simple: two metal “wipes” make contact with concentric circle traces on a round PCB. Unfortunately, over the years the stand warped a bit and the wipe made contact with the PCB where it wasn’t intended do. This caused an arc, destroying the PCB.

The first step in recreating the PCB was measuring the wipes and the distance between them. This allowed [Jeff] to determine how thick the traces needed to be, and how much space should be between them. He was then able to take that data and plug it into Inkscape to come up with a design for his replacement board.

To make the PCB itself, he first coated a piece of copper clad board with black spray paint. Using the laser cutter at the makerspace, he was then able to blast away the paint, leaving behind the two concentric circles. A quick dip in acid, a bit of polishing with toothpaste, and he had a replacement board that was close enough to bolt up in place of the original hardware.

If you’d like to see the kind of hacks that take place above the stand, we’ve got plenty to get you inspired before next Christmas.

[Ken Shirriff] Becomes A Core Memory Repairman (Again)

December 29, 2017 by 5 Comments

Lately, [Ken Shirriff] has been on some of the most incredible hardware adventures. In his most recent undertaking we find [Ken] elbow-deep in the core memory of a 50-year-old machine, the IBM 1401. The computer wasn’t shut down before mains power was cut, and it has refused to boot ever since. The culprit is in the core memory support circuitry, and thanks to [Ken’s] wonderful storytelling we can travel along with him to repair an IBM 1401.

From a hardware standpoint core memory makes us giddy. It’s a grid of wires with ferrite toroids at every intersection. Bits can be set or cleared based on how electricity is applied to the intersecting wires. [Al Williams] walked through some of the core memory history last year and we enjoyed hearing [Pamela Liou] recount the story of how textile workers consulted on the fabrication of core memory for the Apollo missions during her OHWS Talk in October. But giddiness aside, core memory has pretty much gone the way of the dodo having been displaced by technologies that take up exponentially less space.

Bad inductor (green housing has been dissolved away)

We chuckle at [Ken’s] mention of the core memory capacity for the IBM 1401. It has 4000 characters of memory built-in (with another 12,000 in an expansion box) and he goes on to detail that these are 6-bit characters on a machine that operates in decimal and not binary (hence 4k instead of the base-2 friendly 4096).

You may remember his work a few years back to repair core memory on the same model. The Museum has two 1401’s, which turned out to be a huge help in trouble-shooting this. After tracing out the control lines, the repair team began swapping cards between the working and non-working machines. They were able to bring it back online — establishing one of the green inductors was bad — only to be struck with a second fault in the power supply.

Get this, [Ken] comments that “the whole computer is pre-silicon”. When working through the PSU, some suspect transistors were replaced with germanium power transistors. Those may have been a red-herring, as a penciled-in fuse on the original schematics turned out to be the linchpin of the PSU repair. Buried deep in the assembly, replacing the designed-to-fail part let the ancient beast awake once more.

Machines of this quality were heavily documented, and the schematics make this type of trouble-shooting a lot more manageable. But it’s still as much an art as it is skill. Make sure to give [Ken’s] article a read, and look around at the other repair jobs he’s documented — keeping these machines in service is becoming wizard-level work and we love being able to follow along.

Hexbright Repair Keeps Torch Out Of Landfill

December 24, 2017 by 26 Comments

The Hexbright was a Kickstarter project from a few years ago, to create an open source, rechargeable LED light. [Nick] quite likes them, and has learned a thing or two about keeping them operational.

The torches have a few key issues which [Nick] lists for us, before outlining the necessary repairs. These problems highlight certain design flaws, something one might expect for a hardware product from a new startup. Components inside are easily damaged if the device is dropped, and there is no reverse polarity protection on the battery.

It’s always disappointing to see a product in the marketplace fail to take into account such rudimentary things, but in the meantime, repair is always possible. The guide highlights the basic parts and tools required, which is important, but also goes the extra mile and gives important hints and tips on how to effectively execute the repair in a quick and easy fashion.

Overall, it may not be a hack, but what [Nick] has done both educated on us the mistakes made by a crowdfunded hardware startup and also taught us how to write a useful and thorough repair guide. It’s not just about the parts that need to be replaced, it’s about the best method to replace them. The details and the order of operations always helps – anyone that’s ever attempted a serious automotive repair knows this, for example.

We see a lot of great repair hacks here – like this excellent use of a 3D printer to reproduce belts for old hardware.