Fitting standard CatEye lights to a Brompton

Pre-waffle

I have a 2022 Brompton C-line (3 speed sturmey archer, mudguards, straight bars). It needs lights, but Brompton charge an extortionate amount of money for the official ones; £60 for what is basically Cateye Ampp 500 with a fancy mount - and that's just for a front light. You can get the Ampp 500 with a Vis150 rear light in a combo for £44 at the time I write this. When I bought the set, it was even cheaper at £34. It's a decent set of lights for city riding and the occasional dark lane.

The other big problem with the Brompton light set in my opinion is that the standard rear lights mount near the rear brake, which is very low on a Brompton and easily blocked by hills, luggage, street furniture etc. I wanted a rear light which was mounted much higher. This can't go on the seat post like most lights as the seat post goes fully inside the frame when the bike is folded.

Front light

A while ago I found a forum post somewhere - unfortunately I can't find it now - where someone described a process to mount the CatEye Ampp 500 on the front brake by using the mount that comes with the standard Brompton front reflector.

The process went something like this:

Take the reflector off the wire mount it comes with by undoing the screw on the back of the reflector.

Bend the wire loop that remains forward so it is horizontal. You'll probably need pliers for this.

Take the mount that comes with the CatEye front light, and disassemble it by undoing the screw from the top such that the handlebar loop is separated from the part of the mount that attaches to the light.

Take the part of the mount that attaches to the light, and slide the loop over the wire mount that used to be part of the reflector.

Secure with the bolt and a nut. A washer is probably sensible to stop the screw from spreading the wire mount but I've found it not to be essential.

The finished product looks like this:

Rear light

This required a bit more custom. The Brompton saddle has two mounting points under the rear. I designed and 3d-printed a mount which would hold the light onto these, and retain the quick-release functionality.

I was doubtful that the retaining spring clip would work, especially when printed from PLA (which is pretty stiff), but it actually worked perfectly on the first try.

The file can be downloaded from Thingiverse here, and printed from PLA with only a little support.

It mounts to the saddle with two M4 screws. The holes in the mount are tight enough that the M4 screws self-tap nicely, but there is space to add nuts for added security. I originally did but managed to lose one somewhere along the line.

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License of model: Creative commons share alike. Non-commercial.