Va1984

So, dear framebuilders:
I have a bunch of 1980s steel frames that I would like to drill one tiny hole through the head tube lug in, to run dynamo wiring. They are:
2x 1983 Miyata 610
1x 1984 Univega Specialissima
1x 1983 Raleigh Gran Tour
...so all are fairly sturdy touring steel frames, all are lugged. And all of them have decent paint that I would rather not wreck fully.

the idea would be to drill the smallest possible hole to run a dynamo wire through, on the head tube lug joining the down tube. According to some, I should do this on the side rather than underside (anyone seconds that?).
the wire would then emerge through the bottom bracket shell (either through an existing drain hole or through a new one).

Anyone has any special advice? Any tips for minimising the impact on the paint? Any do’s and don‘ts that I should be aware of?
thank you

unterhausen

I drilled my access hole in the middle of the underside of the lower head lug, like everyone else does. I don't see why you would drill it on the side. Maybe people think that's the neutral axis, but it's not.

Nobody can see the underside of that lug. Just make sure your drilling process is good.

base2 

Sometimes, on some forks, the bottom of the steerer has a hole clean through big enough you can stick your finger in. If you grab a flashlight, sometimes, about a half to 3/4 inch up, there is a hole in either side where the fork blade mates.

If you are lucky, you can feed the dynamo wire up the drain hole at the drop out. Then up the blade & out the hole in the top of the leg & out the bottom side of the steerer. You might find that making a loop with some 20 or 30 gauge magnet wire & inserting it in the vent hole from the bottom side of the crown so as to "catch" & extract the dynamo wire will help with your goal.

As you can tell, I'm not a big fan of drilling holes in things, but if you are lucky & have perserverance you may be able to at least run the wire up the fork leg. From there, just run the wire along a shift or brake cable & save yourself the trouble. Dynamo wires are small & easily broken enough that you'll be changing it frequently anyway.

unterhausen

I took the op to mean getting from the fork to the main triangle.

When I made my fork, I drilled holes in the fork blade and steerer to get the wire through. Sometimes there are vent holes in these same locations, but unless there is a vent hole in the steerer I don't know how you would know that the blade was drilled. Or get the wire through for that matter. Would be somewhat tricky to drill after the fact.

base2 

Indeed. Yeah. You'd definitely need to be able to see up inside the steerer from the bottom of the crown to even tee if there is a hole where the legs meet.

The feed wire from the hub would have to go directly to the light, from the bottom side of the fork crown. This would minimize flex in the wire, making it a moreorless fixed installation. Then a second & more easily replaced wire from the light to whatever routing to the rear tail light.

Going from internal to the steerer to internal to the frame would require a hole from the steerer to the inside of the head tube. (As I gathered from the op) The amount of wire flex there would be insane. If the wire lasted one ride, I'd be surprised. I would not recommend drilling a hole in the steerer to let the wire out so that it could be routed down the inside of the downtube.

A gas pipe Opafiets I rode in the Netherlands had a hole drilled in the down tube a few inches from the lower head tube lug for internal dynamo wire routing, but the wire was broken at the hole & never replaced. I suspect all internal routing would suffer the same fate.

Va1984

thank you — I’ll do it from the underside then. Any specific advice on what will constitute “good” drilling here? I’m not new to drilling into steel but I am in an apartment and have mediocre tools. So I was just going to start small, use metal grade newish bits and generally speaking just be careful.

yes, the Raleigh has a generous drain hole by the fork dropout and there is some hope of being able to run a wire up the fork. The problem is that I could not have the wire come out again at the crown because in my builds the crown is usually “plugged” by a daruma for a fender. But, in general, I am not very concerned about the first wire section (front hub to front light) as it can also crawl on (or even in) a stainless steel front rack. The problem I am trying to solve is the down tube: zip ties, tape and the likes aren’t allowed. If I cannot drill cleanly I could consider gluing the wire carefully to the underside of the down tube but that seems less elegant.

Correct.
The “all internal” routing you suggest seems cool but I am not sure you would be able to turn the steerer (you know, in order to steer the bike!) without essentially having it work as a scissor and cutting the wire off. On the other hand, I don’t see why you think the wire in the down tube would be particularly fragile. All I am planning to do is to drill the lower head tube/down tube lug so that a wire (originating at the front light, on a front rack) can travel inside the down tube until the bottom bracket shell, where it gets pressed into the rolled steel of the rear fender until the rear light.

This system was a standard feature on many touring bikes of the 80s and it still is a standard add on for most of today’s custom builders here in the US. I have a 1984 Centurion Pro Tour with the 36-years old dynamo wire in the down tube, pre-installed at the factory, still going strong. Maybe I’m missing something, but surely the wire feels safer in the tube than out!

base2 

I am not suggesting you route through the steerer to to the inside of the head tube. I was waving you off in case that's what you were thinking. I think we are both in agreement such an arrangement would be a train-wreck.

The hole in the downtube is a stress riser in a high stress location. Especially with the cheap single margin drill bits that seems to be the most common available at the local hardware store. A proper double margin drill bit &/or reamer & the proper cogsdill deburring tool would be the proper tools for the job, along with a drill guide to ensure a straight round hole. Expensive city.

All that aside, the wire will flex at the downtube enterance hole with each & every correction in balance as you ride the bike. The wire will eventually break from all the flexing & that'll be all she wrote.

You do what you want. Drill the lug if you insist on making holes, (I wouldn't, nor do I recommend it) but as a machinist, I would not do so in the downtube.

I would count on replacing the broken flex prone wire regularly. Sure. The part in the tube will be fine. Nice & durable & protected. But it'll get 6 inches shorter with every fix 'cause the flex at the hole is the problem.

unterhausen

I am as paranoid as the next guy about breaking wires in this flex situation, but I have a batch of bikes with dyno taillights and I have never had a problem with wire flex getting across from the fork to the frame. I was a little worried about my travel bike since I had never used internal wiring before, but there is no more flex in that setup than there is on the external wiring jobs I have done. Just have to make sure there is enough slack. It just doesn't move that much and the wires I use are stranded and very flexible.

And if it does break, it's easy to replace.

Va1984

Usually the flex problem is solved by coiling the wire that dangles between the fork crown and the downtube. From the point of view of cable flex it makes no difference whether the cable enters the downtube or it is merely clamp on on the outside of it.

Can either of you recommend a few upgraded tools that a home— (in fact, apartment—) mechanic can buy to make the drilling into the lug as neat as possible? I can spend up to $200-$300, especially if those are tools that I may reuse here and there, whether drilling into stainless steel fenders and racks or making furniture or whatever. Nice cobalt bits (I had never heard of double margin bits but would be happy to see if they are affordable)? A consumer deburring bit set? I understand that your professional conscience tells you I should just not do it. But we are talking about a <5mm hole in a couple of <$300 frames for my personal use, and I am a <150lbs rider who does not really do any loaded touring or any crazy log-jumping or anything that would really make a disastrous failure likely. So — any tips you can give me to help me make the job less crappy are welcome. Thanks folks.

unterhausen

Just get some good drill bits. I assume you have a drill.

The brand name drill sets like Dewalt or Milwaukee are good enough for this. Nothing special is needed. I usually use cutting oil, but you don't really need that.

wsteve464

One of the best tools I have found for deburring, shaping, cutting, sanding ( little drum sanding wheels with a mandrel) tubing and small things is the top of the line battery powered Dremel, I have 2 of the refurbished ones and no problems, I buy bits, cutter wheels, diamond and abrasive, tungsten cutters/shapers off of ebay/amazon. I had a Dremel years ago and was less then impressed but with this new battery powered one I don't know how I managed without it.