Parts-bin hack: DIY magnetic phone mount for indoor training

Delve deep enough into a hobby and you get to a point where you have all sorts of bits and bobs lying around. Cycling is one such hobby. If this blog’s history is any indication, I’ve gone through a lot of parts and devices which are now junk. With some ingenuity though, junk can become ripe for the picking for a second chance at life.

One of my first front lights is Cat Eye’s Nano Shot. At this point, the battery barely holds a charge, and the 206 lumen light output is pretty pathetic, long since outdone by its Volt 800 and Volt 1200 brothers. All three of these front lights, however, mount with the very same FlexTight mount you leave on your bike’s handlebars.

As I don’t really need a front light when training at home…today I take advantage of Cat Eye’s front light mount system to fashion myself a phone mount. This is useful for sessions on RGT Cycling, where the phone app controls the training experience and serves as a hub for connecting your sensors, power meter, and smart trainer. I can also use it to control the Wahoo KICKR SNAP’s resistance settings and ERG mode power when following along on one of CTXC’s various indoor cycling workout videos, which have lots of intervals.

Quite a bit of this “hack” was already done long ago, when I installed the Redshift Sports ShockStop suspension stem and its optional utility mount. I used that extra portion of “handlebar” to wrap Cat Eye’s FlexTight front light mount shoe around. You don’t really need the utility mount, but it centers things really nicely.

Cat Eye’s FlexTight front light mount shoe. Smaller lights have a single rail that slide into the central channel, like a flash on a camera. Larger lights swallow this shoe from the outside in.

This will serve as the foundation of the phone mount.

The Nano Shot front light then needs its mounting rail taken off. A single bolt holds it to the light’s underside, secured with a bolt turned by a teeny tiny 1.5 mm hex key. Note that this single central mounting rail design is also used by some other Cat Eye front lights, such as the Volt 800.

With the mounting rail free, the next component comes into the picture. This is a magnetic cellphone mount meant for use on cars, which I had a spare of.

This particular unit is a ball-jointed affair. The black face houses four or five rare earth magnets, which I already know work pretty well in holding on to a medium-sized smartphone. The other end is meant to stick to your car’s dashboard or some other sufficiently flat surface with supplied 3M VHB adhesive tape.

To mount your phone onto this, the box contains a flat metal sticker for the magnet to pull on. Stick that onto your phone’s back side. There are larger sizes of these metal stickers if you want more leeway in adjusting how your phone sits on the magnet.

In my car, I have a version of this mount which has a rubber clip to hook onto A/C vents. The vent clip tends to let go before the magnets do, in my experience. This is strong.
That ball joint is pretty tight and sturdy. I’d bet the adhesive gives out before the ball joint goes loose.

Take the mounting rail from the Nano Shot and stick it onto the adhesive tape on the magnetic cellphone mount.

You can then slide this entire thing into the front light mount shoe on the bike. Adjust the angle of the magnetic mounting face as needed, then just lay the phone onto it.

So how well does it work? Pretty darn great! I was concerned about the mounting rail sticking to just one-third of the 3M VHB adhesive patch, which may not provide sufficient purchase, but the whole arrangement holds fast quite nicely. The ball joint is quite a bit more mobile than I thought, easily moving along with the smartphone as you alter its position or peck at the screen, but still holds its position solidly once you go hands-free.

The magnetic retention makes for convenient attachment and reattachment, but it’s also the reason why I can’t recommend this for outdoor use. Unlike a dedicated mount like the Quad Lock ecosystem, which has mechanical attachment to the phone, I don’t quite trust this to hold together under the vibrations from Metro Manila’s crappy road surfaces. The phone starts to jiggle on the magnet when cranking out a 700W sprint or three, and I’m not really a fan of riding outdoors with your phone on your handlebars, either. For indoor training and virtual cycling though, this is a nifty hack.

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