[Josh] is replacing the springs in his car’s suspension. He wanted to know the travel rates of these springs, but apparently, this is a closely guarded trade secret in the industry. One company did manage to publish the spring rates, but they weren’t believable. Instead of taking this company’s word, [Josh] built a spring tester.
The theory behind a spring tester is pretty simple: apply a force to a spring, measure it, then measure how much the spring has traveled. Or compress a spring an inch or so, measure the force, and compress it some more. Either gets you the same data.
This spring tester is built around a Harbor Freight hydraulic press. Yes, the spring is completely captured and won’t fly out of the jig if you look at it wrong. The bottom of the press contains a few load cells, fed into an ATmega8, which displays a value on an LCD. For the displacement measurement, a ruler taped to the side of the press will suffice, but [Josh] used a Mitutoyo linear scale.
What were the results of these tests? You shouldn’t buy coils from Bilstein if these results are correct. The rates for these springs were off by 70%. Other springs fared better and won’t bind when going over bigger bumps. That’s great work, and an excellent application of Horror Fraught gear.
You find them everywhere from 3D printers to jet airliners. They’re the little switches that detect paper jams in your printer, or the big armored switches that sense when the elevator car is on the right floor. They’re microswitches, or more properly miniature snap-action switches, and they’re so common you may never have wondered what’s going on inside them. But the story behind how these switches were invented and the principle of physics at work in the guts of these tiny and useful switches are both pretty interesting.
Continue reading “Microswitches: Past the Tipping Point”
3D printers are great for creating static objects, but if you’re clever, it’s possible to print functional devices. If you’re absolutely brilliant you can go far beyond that, which is the case here. This door handle with a key-code lock does it all with 3D printing using mechanism designs that look like alien technology. This is just one application of a much more interesting mechanical digital logic they’re developing (PDF).
Working from the [Hasso-Plattner-Institut], the research team is focusing on metamaterials as mechanisms in and of themselves. The crux of this lock is a series of bistable springs that — if the correct code is entered — will trigger in series to unlock the door. The project builds on the grid of shearing cells seen in the door handle we featured last year. It happens quickly in the video, but the intricate cascade of the handle unlocking is a treat to witness.
It’s a fascinating show of mechanical design. The common elements of digital electronics are all present: set or unset bits, logic gates, propagation issues, the whole works. But there are added challenges in this system, like the need for special cells that can turn the logic chain by 90 degrees and split the signal into more than one part.
This signal splitting is seen in the upper right (bifurcation) and leads into what is in effect an amplifier. The locking bolt must be moved twice the distance of a normal cell, so a dual-cell input is necessary to offset the loss of force from the incoming smaller cells. Cognitively we understand this, but we’re still trying to gain an intuitive sense of the amplifer mechanism.
One thing’s for sure, the overall concept is far cooler than this admittedly awesome door lock mechanism. The paper is worth your time for a deep dive. It mentions their design editor software. You can play with it online but we don’t think it’s been updated to include the new logic cells yet.
Continue reading “3D Printed Key-Code is Plastic Digital Logic”
While it’s often thought of as a criminal activity, there’s actually a vibrant hobby community surrounding the art of lock picking. In the same way that white hat hackers try to break into information systems to learn the ways that they can be made stronger, so do those in the locksport arena try to assess the weaknesses of various locks. For the amateur, it can be exciting (and a little unnerving) to experience the ease at which a deadbolt can be picked, and if your concern is great enough, you can go a little farther and modify your locks to make them harder to defeat.
The lock in question was sent to [bosnianbill] by [Rallock67] with a device that [Rallock67] had installed using common tools. Known as a Murphy Ball, a larger-than-normal spring was inserted into one of the pins and held in place by a ball bearing. This makes the lock almost completely immune to bumping, and also made it much more difficult for [bosnianbill], an accomplished and skilled locksmith, to pick the lock due to the amount of force the spring exerted on the cylinder. The surprising thing here was that this modification seems to be relatively easy to do by tapping out some threads and inserting a set screw to hold in the spring.
Locksport and lockpicking are a great hobby to get into. Most people start out picking small padlocks due to their simplicity and ease. It’s even possible to pick some locks with a set of bobby pins. And, if you really want to see how easy it is to defeat some locks and/or how much good the TSA does for your overall security, you’ll want to take a look at this, too.
Thanks to [TheFinn] for the tip!
Continue reading “Modify Locks to Baffle Burglars”
[This Old Tony] teaches us how to make springs on a lathein this video done in the style of How It’s Made. Mixed in with snark, in his usual style, is a lot of useful information.
The Machinery’s Handbook certainly has all the information one would need to design the basic spring shapes, but it’s not always necessary. [Tony] points out that cheating is entirely acceptable. For example, if you need a spring that’s close to the dimensions of a standard spring, simply copy over the values from the standard spring. He explains all the terminology needed to decrypt the pages in your engineering tome of choice.
He shows the basics of winding a spring on a mandrel (or that round metal thing, if you want to use the industry term). First wind the inactive coils, then set your lathe to the desired spring pitch. Engage it as if threading, then disengage and wind the final inactive coils. A quick trip to the sander squares the ends of a standard coil spring. However, the tools can also be used to make torsion springs, or even exotic combination springs.
For a good… educational laugh, watch the whole video after the break.
Continue reading “Making Springs At Home”
Can we do away with a keypad and just squeeze our phones to check messages and dial contacts? [Sidhant Gupta] has been researching the idea of an electronically adjustable spring mechanism that might just make this possible. He calls the prototype above the SqueezeBlock. If you pick it up and give it a squeeze you can feel springs pushing back against your fingers, but it’s all a trick. Inside you’ll find one motor with a gear that converts the linear motion into a rotating force. Attached to the same axle as that gear are a motor and a rotary encoder. A microcontroller monitors that encoder to detect a user squeezing the two plates together, then drives the motor to vary the resistance. [Sidhant] outlines some possible uses that included stiffer resistence as unread email starts to pile up, or squeezing the device to its smallest size to turn the ringer volume all the way down.
We’re a little skeptical of this functionality in handhelds just because of the power consumption issue. But if that is somehow overcome we think this would make a pretty interesting phone feature… at least at first. Click through the link above for a video demonstration or get the details from the research presentation (PDF)