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Yeah, I know. Don't.
But…
Rebuilding my commuter. Steel frame and fork: 1993 Kilauea and P2. Old. I've noticed I can run a dynamo wire up inside the fork leg, and the only thing stopping me running the rear wire internally is the lack of entry to the down tube.
There are three ways I could feed the wire in:
1. by drilling a hole in the down tube itself,
2. by drilling a hole in the head tube (NB it's a long head tube and the frame has narrow-profile tubing so there's a large available area at the back of the head tube) and then feeding the wire into the down tube via the existing internal breather hole in the back of the head tube, or
3. by drilling a hole in the fork steerer tube and then wiring down through that same breather hole.
Option 3 is neatest, as it would mean the only exposed wiring would be at the front axle and under the saddle. Super tidy.
In all cases the hole would need to be a minimum of 3mm in diameter. The bike's not going to see massive stress: it's long been retired from off-road use and mostly just goes to the train station and back.
A few things are obvious:
1. Holes are stress risers, duh
2. I don't have a means of reinforcing the hole
3. Drilling a curved steel surface without a machine press is nigh on impossible
Pragmatically, I suspect point 3 counts it out before we even get to whether points 1 and 2 mean certain death, but does anyone fancy kicking the idea around anyway? I'm drawn to the steerer… partly because it's super neat and partly because having keyed the frame ready for a respray I found some odd surface marks around the down tube butt… I'm kinda happy to pretend I haven't seen them, but for what remains of peace of mind I'm a little reluctant to add a hole to whatever's going on there 🙂
I stumbled across this, which is drilling-a-go-go—steerer and then some…
http://nyvelocity.com/articles/equipment/cx-di2-live-build-with-mark-purdy/
I remember George French used to have a weird front brake routing on his BMX where he ran the cable inner down the steerer tube and drilled an exit hole in the crown - worked for him but his BMX forks probably weighed more than your frame.
Wow - I wonder how long that CX build lasted? Drilling holes in aluminium is riskier than steel, AFAIK.
My main concern about no. 3 is the lack of clearance inside the head tube - it's not like a modern internal headset tube, it's going to be pretty tight in there and you'll have to find a way to allow for lots of bar rotation (loop the cable right round the steerer loosely a couple of times?) or you'll be re-wiring after every time you stow the bike in the back of a car or someting.
Other than that... I'd say go for it. 🙂
1993 Kilauea
drilling will void your warranty 😉
I think the wire will get damaged quickly on either of the head tube options.
I think I'd go option #1
For problem #2 look up Rivnuts - they are actually intended to provide a threaded hole in a tube perhaps there's threadless versions. Here's a guide on installing: https://bikepacking.com/gear/rivnut-bottle-cage-mounts/
My main concern about no. 3 is the lack of clearance inside the head tube – it’s not like a modern internal headset tube, it’s going to be pretty tight in there and you’ll have to find a way to allow for lots of bar rotation (loop the cable right round the steerer loosely a couple of times?)
Yeah, I reckon there's enough clearance. The wire's 1.5x3mm twin, and it seems to sit ok, and yes, I was going to ensure there was enough slack in there to allow full rotation. One remaining concern (because I don't trust electricity) is whether the wire sheath will wear through and start electrifying the frame 🙂
I think the wire will get damaged quickly on either of the head tube options.
Yeah, that.
drilling will void your warranty 😉
Heh. That was voided in April 1993 when I had to have a new top tube brazed in 🙂
For problem #2 look up Rivnuts
Yeah, I thought about those (not that I have a tool) but I wasn't sure they'd provide any reinforcement value, especially as the hole would have to be drilled much larger (though I wonder whether a 3mm hole is actually too small from a fatigue point of view). Brazing something on would work, but all I have to hand is electrical solder and a washer, and I can't see that adding much strength either.
I wouldn't even consider drilling through your steerer tube, unless you like facial traumas?
Making holes in stuff is fine as long as it doesn't fail; the steerer tube's already got two 26-year-old holes in it, they're just in places where it doesn't cause a failure.
The question is whether there are areas somewhere between the headset bearings where a hole also won't cause a failure, and I'm guessing neither you or I have done the FEA on this one 🙂
I definitely wouldn't bother, but if you must, I would go for the back of the head tube if it's quite long (i.e. far enough away from the welds and HAZ).
The size of the hole won't have much effect on the magnitude of the stress raiser, until you get to the kind of size where you're removing a lot of the actual tube (although it works strangely so although your net section goes down, your SCF goes down too so it's not as bad for fatigue as it might be).
Don't put it on the down tube, although there are holes there already it's under a lot of cyclic torsion loading the whole way down so any hole anywhere could start off a fatigue crack.
Even with reinforcement, the hole could be worse from a fatigue perspective. What you really want to do is cold work it in a way that will introduce a compressive residual stress around the hole, so that you then can't get fatigue cracks starting in the region where the SCF is highest. You could do this with some sort of expanding thing, but might totally wreck your frame trying to do it. I'm sure there must be some sort of crack stopper kit that could do this, not sure about whether it would be suitable for the sort of thickness you'd be dealing with.
Make sure you protect it from rust, too.
Oh and I would be worried about pulling the wire about too much on option #3, though I'd think you could do it in a structurally sound way.
Yeah, my thoughts were similar, I had pretty much ruled out the down tube on the basis of fatigue risk given its current state. Back of the head tube was still vaguely under consideration, though I'm pretty certain it would be a nightmare to actually drill.
I'm not too concerned about rust. Back in the 90s when I was in uni halls I used to regularly throw this thing in a canal, literally, to clean it. It's survived a quarter of a century since then.
Just buy a decent drill bit and go for it.
The frame is not going to implode because of a 3mm hole.
Ooh ooh!
I can be the first to say it!
How do bottle boss holes in the down tube get there?
Wont putting it through the steerer mean its moving every time you move the bars?
I would either
a) Have it follow the rear brake cable and then into the frame via rack mount holes on rear seat stays or
b) Drill a hole near to cable guide for rear brake on top tube.
How do bottle boss holes in the down tube get there?
Yeah, obvs, but they’ve got way more metal than would otherwise be there. Which isn’t to say that a frame would fail without them; in fact I drilled both bosses out on my old In red because they were too far up the seat tube and I couldn’t drop my seatpost enough. And I properly caned that bike 🙂
I would either
a) Have it follow the rear brake cable and then into the frame via rack mount holes on rear seat stays or
b) Drill a hole near to cable guide for rear brake on top tube.
Unfortunately neither of those are any good for routing up inside the seatpost 🙂
What I’ve done is glue some guides (in the form of aluminium cable crimps, in a size I bought specifically for routing dyno wires) along the bottom of the down tube. From there it’ll go in the hole in the BB shell where the cable guide would normally go, and up the seat tube and seat post.
I think a hole in the frame would be ok, but I just think doing it with a hand drill would be a bit optimistic. I’m short on time and patience at the moment 😀
if you want to do a proper solution, how about pushing the electricity (I guess its only a little bit needed) through the frame/fork interface wirelessly? the distances are small, but the metal in the way might block it?
I'd do the little hole in the downtube myself. if its tucked behind the fork crown you'll never see it
I'd be putting a rubber grommet in the steerer hole to protect the wire from saw-like rubbing every time you move the bars (may require a larger hole tho )
Well done using a retro bike as a commuter.