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Engineer builds 'working' Thor's hammer that only he can lift (cnet.com)
243 points by davidiach on Oct 14, 2015 | hide | past | web | favorite | 56 comments

This is pretty clever. The major improvements I'd want to make are some sort of RFID chip that deactivates the magnet when I'm close enough, instead of a fingerprint scanner. It seems like anyone who gets close enough can see the scanner, so I'd prefer to have something more invisible.

And the second thing would be just to improve the lag time between grasping the handle and the deactivation of the magnet, so I can just lean down and casually grab it, instead of having to hold it for a second before bringing it up. The more magic, the better.

Still, this is pretty awesome!

There are some ways that he could have improved the deactivation routine, but I thought the most clever thing was that he used a capacitance sensor to activate the magnet the moment the handle was touched. That had to greatly increase the battery life.

But also make it prone to discovery as the guy at the end of the video that spin the hammer out without touching the handle.

You could probably spin it out even with the magnet activated. The friction coefficient is probably too low for any realistic electromagnet to be strong enough to make it impossible to "slide" out.

Just try with a magnet on your fridge door. It's much easier to slide it around than it is to pull it away.

It's a bit of a balancing act between "magical" and "proper". Like it would be very easy to just have a third party control the electro-magnet via a remote control, and it would work perfectly in all situations as long as the third party was acting correctly. But it wouldn't really be a hammer that could only be lifted by one person.

Additionally having the hammer remain locked once he steps away would be a good improvement. It looks like it only locks when a person begins to clasp their hands around the handle.

Seems to me this is by design, to avoid wasting massive amounts of power when the hammer wasn't being grasped.

A Pro Mini draws a tiny amount of power, I'm talking tens of milliamps- he could leave this hammer somewhere for weeks probably without the batteries dying, with the occasional passerby trying and failing to pick it up. To manage that with the magnet running constantly would be impossible.

It's also a great safety mechanism, being stuck between an electromagnet and the metal sounds unpleasant, just shout at the guy stuck to not touch the handle and it will not hurt them!

I think an RFID ring worn on a finger would be the best bet for that.

Cool idea, terrible acting. I feel like the "wow" factor in his audience was really killed by the awkward way he made it look like he was pushing a button and waiting for something to happen, instead of struggling to "lift" the hammer while he waited for the thumbprint to register.

I knew a guy that made a lightsaber that only he could use. Part of the act was that only a "real Jedi" can activate a lightsaber. He used a neodymium ring and a hall sensor. The trick was seamless.

With all the people getting magnets implanted subcutaneously, that would be an even better trick!

This would end badly - around this Thors hammer, it would rip them right out through the skin.

And this is why I will never get a magnet implant, despite the wicked cool ability to sense active AC power lines.

As would an MRI, presumably.

What about implanting an NFC chip and having the hammer stuck to a holder/floor as-is with a strong magnet?

I agree. I think dressing up as Thor and playing up the crowd the way you suggested would have gone a long way. Also putting the fingerprint scanner where you one actually grabs the handle from, somewhere midway on the shaft, would have been a better design.

If you like this kind of stuff, check out Colin Furze's youtube channel. He does some similar experiments, and is very entertaining.


It is kind of terrifying seeing him operate so many machines with his tie dangling around his neck. He obviously knows his way a round a shop better than I do but I always thought neckties were no-nos in the shop.

Wearing them still isn't a good idea, but clip-on ties will at least break away when they get caught rather than forcing your head into some machine...

From the constant cuts to extreme close-up, I'm betting he puts on the tie and collared shirt for talking-to-the-camera shots (and one or two per episode where a machining tool is on, but he's carefully away from it) and takes it off most of the time when he's actually working.

A wireless remote hidden in a shoe or something may have been a better idea. Struggling to lift the hammer doesn't really fit Thor, either.

A simple disguised mechanical switch would have worked much better. Set it up so you have to push the handle down before pulling it up to disengage the magnet for instance.

lol. It's a great geek thing to do. These completely random acts of technology is how great things are born, believe it or not.

Indeed. This is also the kind of thing I would really like to be doing. Alas, $dayjob. :<.

It needs an accelerometer to engage the magnet if the device is disturbed without the handle being touched.

Ahh yeah to prevent the guy from spinning it off and picking it up

Most of the magnetic field lines are along the z-axis (up and down) so anyone could still simply slide the hammer towards the end of the metallic floor it's sitting on(like the sewer cover) and be able to pick it up then. That's how we unstick really strong magnetic targets in our sputtering system, we simply slide them off.

Woulda been cool to add a remote shutoff so that the kids trying to lift it could have a bit of a thrill.

Downside: They might throw it or smash it on the ground like they might with a regular hammer.

I was hoping that instead of magnets, it would just be extremely heavy, and be able to activate an internal gyroscopic system to do something like this: https://www.youtube.com/watch?v=GeyDf4ooPdo

It'd be pretty hard to fit all that in a small package though, and probably dangerous.

That's not how physics works. If the hammer is too heavy to lift, putting a flywheel in it isn't going to change that.

I was hoping he'd just made a really really heavy hammer, and happened to be strong enough to lift it himself.

Instead of a thumbprint, he should have used a bracelet with an rfid chip, much faster response time and his hand could have been anywhere on the handle.

Or just inject the rfid chip under your finger.

A fake wedding ring would be better. Won't look out of place, doesn't require surgery.

Ring would have to be non-ferrous

An NFC ring might have been a better solution than the laggy fingerprint scanner. Still, cool idea!

In 'The Illusionist', the magician Eisenheim did a similar trick to Crown Prince Leopold, except it was King Arthur's sword in the stone.

Magician Robert-Houdin performed this trick in 1846 (without the fingerprint reader) [1]

He used the "Light and Heavy Chest" to demonstrate his ability to remove the strength of men for political ends.

[1] http://www.themagicdetective.com/2012/05/politics-magic-and-...

I think NFC or Bluetooth might have been better but neat execution nonetheless.

NFC matched to a subdermal NFC chip would be great.

Is there enough metal in those that a strong electromagnetic (say, like the one in this device) could rip it out of your skin...?

I'd have picked a different legend: the sword in the stone is more similar to how this works, the sword can be wielded by anyone after the king pulls it out of the stone, and this hammer can be wielded by anyone after the engineer pulls if off of the magnet. Thor's hammer can only be wielded by him, ever.

But it's still awesome.

Is it possible to figure out the force required to lift this with magnets engaged?

Neat project.

I can't help but wonder if you could beat the magnet by kicking the handle sideways, the strong impact multiplied by the lever force might be enough to beat it.

Good observation! If you watch the video to the end, this actually happens.

This is really neat. I wonder if there is the possibility of using a similar magnet set-up as a lock? I worry about my motorcycle being stolen since it is so easy to pick up and most locks can be broken, if I had an electro-magnet like this one it might be much harder to steal.

Could you do something similar with cornflour mix?

In testing, I found that the cornflower mix did not conceal the magnets effectively enough for the illusion to be maintained.


Since it's magnet, did it break the electronic devices the "lifters" were carrying?

Why would it?

I was thinking something like this - https://www.youtube.com/watch?v=_yEu2R1gYSs

Also some credit cards have warnings to not put near magnets, but maybe the magnet's not strong enough to do damage

Magnetic force decreases with the cube of distance from the source. Which is to say that it would take a ludicrously strong magnet at arm's length to do any damage to credit cards in their back pocket.

There's some context not obvious in that video: The machine as a whole fails, yes, but the only part of it that malfunctioned was the hard drive. The rest of the electronics in there are solid-state, and won't (okay, will be, but only minutely, and not enough to cause failure) be affected by the magnet. Your cell-phone is magnet safe.

What happens if the magnet comes back on while the hammer's not touching the metal? Is there a way to make this safe?

The hammer seems to have multiple magnets on the bottom, so you could probably check for a closed circuit between them before turning on the magnets.

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