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Internal wiring for dynamo lights: the heads tube connection

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Internal wiring for dynamo lights: the heads tube connection

Old 11-13-18, 11:21 AM
  #51  
rhm
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Originally Posted by unterhausen View Post
I got the brushes. Most common dimension is 3.93mm. Two of them were 4mm in one dimension, 3.9-ish in the other dimension. I feel like 4mm might be the best choice of hole size.
How easy is it to adjust the size of the brushes, with sandpaper or a file or something?
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Old 11-13-18, 11:37 AM
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it's not too bad. I used an old oilstone, and got it down .02mm before i got bored, which happens fairly quickly. Now my oilstone looks like a 3 y.o. went crazy with a pencil on it.

I'm not sure what an appropriate sliding fit is for these things. I feel like if I design it to 4mm, then it will be rough enough that it will be fine with a smaller brush. And a little acetone should open it up if needed.
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Old 11-13-18, 12:09 PM
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I can add a lot of these together before they start charging more for the cheapest plastic. Still $5 for 4 of them. I just added them together until I got bored, is there a theme developing here?

I probably would make a join between parts that is easier to separate, but I just wanted to try it. Intention is to experiment with tolerances and hole sizes.


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Old 05-06-19, 08:45 PM
  #54  
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Updates and improvements in making the slip ring, forged as a result of screwing up.

I forgot to make the tab when I cut this slip ring out of my sheet of copper; not wanting to waste it I forged ahead, thinking I might be able to make a thin enough solder joint (in spite of the prototyping lessons to the contrary). So I just soldered the wire directly onto it as shown in this photo: www.flickr.com/photos/21624415@N04/33754623348/in/datepos...

As was the case during the prototyping the lump was too thick. Additionally the insulated B&M wire has a large OD, relative to the clearances we're working with. Inserting the fork damaged the wiring. I decided to try to add a tab offset, in situ, to this ring instead of going straight to "remove and replace mode", as shown here: https://www.flickr.com/photos/21624415@N04/47792905381/in/photostream/

Glad I tried it. I was able to remove the old wire, dress the ring and silver braze on the thin tab. Lo and behold there was no continuity between ring and steerer! I'll still clean up the area and apply a thin insulative epoxy coating, letting capillary action suck it in, under the ring and tab. Then I'll secure the wire loop and tab with epoxy, keeping both tight against the steerer (waxed paper with string wrapped tightly around it). The good news is that this works; I wrapped a piece of tape around the steerer to secure the wire loop and the whole assembly slipped inside the HT without any binding. I'm very happy with that!

Notice the length of the tab and placement of the hole in the steerer. Both are such that they will be several mm clear of the lower cup spigot before the entire circumference of the ring enters the bore. That's vital. Also note that I used Velo-Lumino's thinner wire this time. There is so little spare room for this operation that it's definitely worthwhile. An improvement to this, that of course occurred to me immediately after finishing this work tonight, would be to have the long axis of the tab in line with the hole, and the hole a few mm from the end of the tab. That would improve the clearance issue a little, and every little bit is worthwhile.

It was a successful evening. The fork in my BSP bike has the original type of tabbed ring and B&M wire. It fits but it does ever so slightly kiss the ID of the lower cup spigot. Not enough to damage anything but it's a little off-putting. This approach doesn't have that problem.

John Clay
Tallahassee, Florida
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Old 05-07-19, 08:41 AM
  #55  
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Thanks for the update John

As an aside, I'm finally building a fork out of one of the set of blades you raked for me.
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