Mounting for a rack mounted rear light on a bike with no rack

Having a bit of a brain freeze. There must be a mount that can attach to a seatpost or similar that will allow you to mount a 2 bolt rack mounted rear light on.

I'm about to order a Dyanamo wheel and set of lights for my wife's bike and need to mount the rear light. Its got no eyelets so can't put a rack on it. Also seems daft just for a light.

Any ideas?

I know mounts exist to mount band on lights on racks but I kinda need the opposite. Sort of.

I thought of the small metal bracket for Bromptons without racks but its awfully chunky and the wrong angle and with the larger wheels it'll mostly be obscured. Also as its Brompton it'll be about 50 quid.

Saddle mounted somehow?

The light is a bit like this:

If possible I'd rather it didn't look too DIwhY and didn't require too much effort.

Cheers.

bump

You could go with p-clips or similar to mount to the seatpost.
Also there are some bottle-cage mounts that clamp to a tube, which you can fit on the seatpost. They should fit.

God thats a good point. I'll do some measuring.

Will this
http://www.velovitality.co.uk/products/busch-muller-single-bolt-rear-bracket
fit anywhere?
Perhaps on a short bracket off the rear brake mount?

I may be wrong in this case, but some rear dyno lights are designed with the mounting orientation in mind where they're pointing the beam of the led/leds.

Why not drill holes into a strip of plate that you've pre-bent into something like a U or an Omega shape, for the light's bolts, and simply clamp it round the seat pin? Or even use a really large P clip to do this?
Another solution might be to mount a T shaped bit, with holes for your light, into the seat pinch bolt / seat collar somewhere. That would be easier to keep pointing level too.

I think you're correct skully. My intention is to get one of these handlebar bottle cage mounts: http://images.evanscycles.com/product_image/image/c15/4ca/295/73059/large/bontrager-bottle-cage-handlebar-mount.jpg
and turn it sideways, mounting it on the seatpost (resulting in the light in the correct orientation.

If the distance between the screws is correct, that is a very elegant solution.
Mind, that when mounting on the seatpost, you are effectively angling the light downwards, though.

Bugger. So a rack mounting is approx 52-53mm apart (mouting holes) and a bottle cage is 65mm.

I've found one of those brackets I linked above, its obviously designed for 22mm bars so I doubt it'll go around a 27.2 seatpost. Also it'll need new holes drilling (which may work on the above example but not so much on the one I have due to the hinge.

Think that idea is out.

Good point. Had it worked I could potentially file some V-brake pad washers at a slope to shift the angle of the light.

Thats a good call. I reckon that could work. It'd need to be a fairly tall bracket though to go over the rear tyre and mudguard. I'll keep that in reserve as I'd rather have it a bit higher. Or figure out how to mount it on the saddle.

Mount THAT to a single clamp on the seatpost?

These would be good if I could screw them onto the light tightly before putting it all on the seatpost.
http://cdn.mos.bikeradar.imdserve.com/images/news/2015/03/25/1427256208307-zvzqdbm1474s-960-540.jpg
Not ideal though, also back from when I built bikes I seem to recall they only came from Specialized and in 31.8mm seatpost size.

D'oh. Of course! Thanks.

I've got a pair of something similar in a more tubey diameter, and I remember there being at least thee diameter options. But I can't remember where I bought them from or what term I used to find them, so that's not very helpful.

Here's an incredibly expensive option?
http://clee-cycles.co.uk/esite/P20005/product

All in all, it has to be said, a new decent dynamo rear light that is suitable for a seatpost is really pretty cheap ... #justsayin

Yep, just seems wasteful when it comes as part of the kit.

Clee Cycles used to be 10 minutes away before they moved into Bridgnorth. I found everything (I wanted) to be incredibly expensive even before they had a shiny new showroom to pay for...

28mm Munsen ring and a shim? Possibly with aforementioned filed V-brake washers to compensate for the seat tube angle?

Munsen rings are amazing. I could get a brass one!

OK ordered this:

Will either try bending the rod to correct angle or sloped washers. Or the plate that I mount to this will be angled.

I got the longer rod so I can move it back of the saddle/thigh zone a bit.

Still got to order the wheel and lights from Germany which could take some time and I'm away for a bit but I'll update this thread at some point. It'll definitely look shit though. I'm fitting it.

Lots of locktight/glue on the threads too.

Looks really ... practical! Nice.

A plumbing solution?

Very much a plumbing solution for fastening pipes/tubes to stuff.

Larger diameters tend to look less agricultural - clamp screws are smaller in proportion to the rest of it - and the cast ring is usually more substantial than a P clip.

I'd be thinking about filing the end of the stud to the same angle as the seatpost then silver soldering a cross piece / mounting plate to offer a vertical surface for the light.
I'd also use a locking nut rather than locktite, and possibly replace the allthread by counter-bored 10mm bar threaded at one end only. Eventually it evolves into a seatpost-mounted-saddlebag-support-with-fitting-points-for-a-light, but that's a clumsy name so let's call it a rack for short?