Core77

Wheels To Watch: Make Way For Magnetic Bike Hubs?

By Kat Bauman - April 11, 2014

in Cars

This appears to be a run of the mill lightweight mountain bike wheel. It's glossy and show-friendly, but it follows protocol with its fancy direct pull spokes and a standard splined freehub body to take your standard fancy gears of choice. Don't be fooled. Inside that hub lies madness. No, wait, magnets. At a recent Taipei tradeshow Pinkbike got an enviable first look at Spank's unreleased Mag-Drive hub.

For the uninitiated but interested, a bike's drivetrain is almost always controlled by 3+ spring loaded pawls that rotate within a toothed collar in the rear hub, providing the forward engaging/backward freewheeling action that powers the bike and lets you coast. Notable exceptions like DT Swiss included, it's still pretty rare for a rear wheel to not use pawls. Anyone who's ever had to work on a freehub knows that pawls are both simple and a little irritating. I get grumpy fingers just thinking about the widgety bits. More importantly, for performance riders (and those of us who commute competitively) unnecessary friction and gaps in engagement are distracting and offensive, and a failed freehub can be devastating. All of these issues can come up in even newer wheels, and increase in likelihood with age and dirt and abuse. Spank, and a few other companies (like DT), are proposing that the opposing resistance of magnets can solve some of these problems.

DT Swiss' complicated chip in the mag-hub game

Though it sounds like the Spank Mag-Drive hub has been in development for a couple years its specs are still hushed up. (Impatient? Check out the Soul-Kozak M-Netic or the DT Swiss patent.) However, the general appeal of a magnetic system boils down to a couple key points: lower friction and stronger engagement. As magnets push away from one another their force decreases, whereas a spring's tension increases when compressed. As Mike Levy points out on Pinkbike, pawls provide the opposite of the desired mechanical relationship: "Weak when engaged and stiff when freewheeling adds up to more noise, less positive engagement, and more freewheeling friction."

What you want is high friction under load, low friction (and therefore lower noise) while freewheeling. By all available accounts, the Spank system is super simple and tight but loud. The DT system pictured above is a magnetized version of their existing star ratchet system. Also unreleased, but based on magnet-added version of a well-tested design.

This is not rocket science, but it is a finicky and interesting problem in a finicky and interesting industry. So maybe it is rocket science. Bike nerds weigh in—is this a good direction?

o

Favorite This
Q
5

Comment

Comments

K

10 years ago

Z

Z

Reply

These magnets need more power!

Aside from strapping a couple car batteries to your frame and running electromagnets, magnetic bearings wont lift your weight off the ground.

So, its not as cool as it sounds. But, it still might lift more weight than the device weighs, marginally reducing friction.
!Report as spam
matt

10 years ago

Z

Z

Reply

It looks like the engagement on the DT patent drawing is the same as the engagement in the non magnetic version of the system (which works awesomely). So the benefit is that you are using magnets instead of springs. Is that a benefit?

I'd say it is if you have ever had a spring problem in a DT 240 or similar hub, but you haven't because they are already so simple and well designed.

This isn't adding any value to an already exceptional hub drive system. And for the record, pawls work really well too. When talking about the resistance differences between pawls and a magnetic ratcheting system in the above example, you would see a bigger difference in rolling resistance by getting a haircut and shaving 15g off your head.

With that in mind, who knows where this will end up and it is most definitely worth DT's time and money to add to their IP portfolio.
!Report as spam
Greg

10 years ago

Z

Z

Reply

tech is a bit old. Tune had prototypes out in 2009.
http://www.bikeradar.com/us/news/article/eurobike-tune-uses-magnets-in-new-hub-23279/
!Report as spam
Antipodean_G

10 years ago

Z

Z

Reply

It's interesting, yes. The issue is that it's coming from an industry that constantly reinvents things for no other reason than to create hype and forced sales.

Does it solve a problem that exists? I would have to say no. Pawl hubs are extremely refined and a good high end hub can outlast the owner. Even the cheap ones are pretty good these days and can keep on going for a good long time.

Does it make the hub cheaper, lighter or longer lasting? Probably not.

Does it simplify the design? Maybe, maybe not.

If it can be tangibly proven that the magnet option is better in more than one facet, then it could be a good thing but if it's just a parallel version of the same thing, then what's the point?

Progress in design and manufacturing is a wonderful thing and indeed there have been many in the bike industry that have improved the quality and performance of bikes at all levels over the past 10 years. At the same time though there has been, and continues to be, and even greater plethora of what I like to call marketing engineering and design, designed to force sales. Is this one of them?
!Report as spam
Benjamin Talbot

10 years ago

Z

Z

Reply

I theory yes, less friction and better engagement would be an improvement.

In practice, I think the difficulty will be in developing a mechanism that works consistently, isn't heavier than existing designs, and isn't vastly more expensive than current top end that uses ratchet and pawl.

So yeah, magnets are cool and mysterious! magnetic freewheels today, magnetic hubs, bottom brackets, headsets, and pedals tomorrow...
!Report as spam