Bottle Dynamo Mount

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Scott

Bottle Dynamo Mount

Post by Scott »

I recently bought a B & M S6 bottle dynamo (CJ - from Rose Versand at less than 50% of the U.K price). The problem is that it is to be fitted to a bike with disc brakes and consequently no boss for v or canti brakes. There is a low rider type boss about half way down the front fork on the outside but other than the Zinkens Dynashoe (which is only suitable for a boss on the front of the fork) I don't know of any other purpose built bracket for mounting bottle dynamos. I'm willing to fashion something for myself but given how crticial the alignemnt of the dynamo is to the tyre, I don't really want to end up in a trial and error situation. If anybody has any suggestions, they'd be very welcome.

Thanks

Scott
CJ

Re:Bottle Dynamo Mount

Post by CJ »

All that you can get ready-made is a basic clamp-on dynamo bracket to go on the seatstay. It'll have to do until you have the opportunity to get a secure fixture welded onto the forks.

Do not be tempted to try clamping one of these or something home-made onto the front forks. On the forks things tend to vibrate loose, never mind how firmly you think you've clamped them, and a dynamo in the front wheel spokes is quicky followed by teeth in the tarmac! (Whereas rear wheel lockup merely produces a skid.)

It should be possible, however, to make something that uses a low-load carrier boss for security. Snag is, that boss is a lot lower than you want and the M5 screw that it takes is way too feeble to support the dynamo by itself, so you need a combination of a clamp at the appropriate height with a safety strut to the low-load braze-on. It won't look pretty and nothing like that exists ready-made. And I would not recommend just anyone to attempt such a safety-critical item as a do-it-yourself job, so it's with trepidation that I share this idea.
richardirving

Re:Bottle Dynamo Mount

Post by richardirving »

I had a similar problem with a tricycle with a roller (tyre tread) dynamo and rear facing brake mounts. It was solved by Tony Oliver (long gone as a frame maker, sadly) who fashioned a custom made bracket which used the drilling in the fork crown as a stabiliser. That suggests (to me at any rate) that you might be able to use a flat plate U-shaped brake booster anchored to the crown drilling - assuming you have one of course - with large P-clips (fixed to the cantilever brake drillings) clamping onto the forks; that might then allow you to use the Zinkens dynashoe a little more conventionally with a few M6 bolts and nuts of the right length. I would, however, earnestly endorse Mr. Juden's cautions regarding such DIY projects.
Scott

Re:Bottle Dynamo Mount

Post by Scott »

CJ,
I have an engineering background (albeit much more on the applied maths side than anything else) so I've made a somewhat over engineered bracket that is fixed to the low loader boss at the bottom and then secured higher up the fork to stop the bracket loosening or rotating round the puny bolt on the bottom boss. The leverage exerted by the dynamo at that distance is quite considerable so the bracket weighs about the same as the bike.It's only a temporary measure until I can persuade someone to tig something more precise and stable to either the fork or at the rear.

Richard, the problem is that there are no cantilever brake drillings at that's why the dynashoe isn't an option.

Thanks to both of you for your help though
dreamermike

Re:Bottle Dynamo Mount

Post by dreamermike »

Thanks, Chris, you have probably saved my bridgework. I read the message quite by chance but am just about to fit a bottle dynamo to my front fork and intended to use the clamp provided by Lightspin, which is just an overgrown version of the clamp that used to be used for Never Ready rear lamps. Mine ALWAYS worked loose and rotated around the seat stay. Fortunately due to gravity and the slope of the seat stay they rotated so they contacted the spokes forward of the seat stay and all that happened was a tinkle of spokes as they pushed the lamp out of the way. I intended to mount the bottle dynamo behind the fork blade and the effect of it rotating to contact the spokes would be very different; it would jam and as you said, teeth on tarmac. I will now mount it in front of the fork blade with a safety link to the V brake boss. It might be of interest that Orbit show in their online catalogue a "canti/V-brake mounting bracket for mounting dynamo on the front of your forks using the brake boss (left hand side only)". It appears to be a clamp that incorporates the safety link to the brake.
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