Hole Repair Problem..?
 

My next project, and I am really looking forward to it, presents a problem. The bike, a 1971 Bianchi high end machine, sports two holes in the top tube that the original owner drilled to allow for an internal brake cable routing. Needless to say, I want to repair the holes, as in plug them up and do so without damaging the lovely chrome plated integral Bianchi head set shell. I am seeking suggestions as to how to do this. The two most likely options are JB Weld (not what I really want to do) or silver solder an alloy plug into place using a small soldering iron and taking great care to NOT damage the chrome. Any suggestions would be appreciated. Thanks...
https://cimg4.ibsrv.net/gimg/bikefor...5f6dca5275.jpg
https://cimg8.ibsrv.net/gimg/bikefor...1df4c61ebc.jpg

Just spitballing... Could you perhaps epoxy the alloy plug instead of soldering it?

I was going to suggest titanium putty as we use it at work for things but after checking the price it would likely be too expensive for this use.

I would think you, or one, could propane a brass plug with silver and safely be far enough away from the chrome to damage.

That's funny, SwimmerMike had this exact same issue with one of his Bianchis. He took it to a local framebuilder who filled it in with brass, if I'm remembering corectly. Maybe SwimmerMike can chip in on how he got it fixed.

Mike Barry used to fill dents with brass. I can't speak to holes but his work was excellent on two of my bikes.

An entirely non-heat method, often used as a cheaper repair ( compared to welding ) on car sheet metal body work is to use a high quality body filler. You would want some sort of backing in the hole first to support it. Maybe a carefully placed piece of fibreglass cloth secured inside the hole, around the inner edges, with epoxy. Body filler is easy to sand to match the contours of the top tube.

we call that "Bondo" (a brandname) and yeah it has some fans but...if this was my frame and I wanted a "no-heat" method I would use epoxy putty. There are many colors (if you go to wood/furniture repair sources) but the typical one sold in hardware shops is gray.
I think it's a stronger "patch" than Bondo.
But Do The Prep (roughen surfaces and clean with denatured alcohol) to optimize bonding.
If you shop around (and if it matters) you can find epoxy putty in white, I know Mohawk and maybe Behlens sells a tube in that color.

What's the problem with the holes? But if you insist, anything beyond bondo is overkill.

Any hot work will need paint, and a soldering iron may not work - the surrounding tube likely has enough heat-sinking capability that you won't get it to even the 225-plus degrees you need for soft-solder-with-some-silver-in-it. Real silver solder is flame-work.

And if by alloy you mean aluminium it'll need an inert gas for sure and probably special fluxes/prep...

If the prep work is done correctly, JB weld is great stuff . I have used it for water jacket repairs on outboard motors and it worked amazingly well. I was shocked and after many hours of use , it was still holding strong. I don’t think a torch is necessary . That paint still looks pretty good for its age and a less invasive approach would be better .

Stress fracture at that point might be a problem. Sweat and water intrusion is another. Filling it with epoxy won't solve the prior, but will help the latter. I'm not quite sure it's a problem, but I'm definitely not sure it isn't. Could be a case of FUD, but perhaps not. I wouldn't recommend just drilling a hole through the frame to pass cable housing through. What could possibly go wrong?

I did a similar job for [MENTION=168558]Drillium Dude[/MENTION] awhile back on his Casati. For small holes I used silver to fill, larger ones brass. Bigger yet I used a bit of brass stock and silvered it in. Of course these were all filed and sanded flush with the rest of the tubing. The elephant int he room is the cost of repainting.

Those holes are far enough away from the chrome, no worries about heat affecting that.

IMO,
I would not use brazing (heat) for a repair such as this. ..you may find that drilling the holes left a burr or high point around the hole, filing it or dimpling it will provide some "extra" hold for the filler. If you do not do this there is no way the Bondo will a stay in place when sanding the filler down. etc.
Find a small peening hammer or pick/scribe and just barley dimple the hole to allow for a thin layer of filler to adhere to the frame.
If this seems too drastic a solution (SMALL dimple), then I would find a suitable sticker or reflective tape and move on, watch for stress fracture (not likely) and it they occur us the more aggressive solution.
Best, Ben

I used JB weld on the oil pan of my car. It was a temporary fix until I had time to change the pan. Well, that was 7 years ago and it's still holding strong through all temps and weather. JB weld gets my vote for a "no heat" repair.
BTW, I patched the fuel tank on my lawn mower with JB weld about 3 years ago. It's still fine.
And, yes, I do have a replacement oil pan for the car and fuel tank for the lawn mower. I just don't want to get into any more projects, unless absolutely necessary.

Epoxy putty sounds good. But it needs a backer support. A couple of ideas. Tape over the surrounding paint to keep drips from sticking.

1. can you reach the holes from the seatpost and the headset tube? On the inside of the tube, epoxy in a piece of fiberglass screening or similar. A couple of layers of screening. Apply the putty after this is cured.

2. a thin rod, with a very fine wire or doubled up thread wrapped around the middle. Use a nail with the head cut off? Liquid epoxy on the rod, slide it in the hole endwise, pull it tight against the inside of the tube and secure the wire around a stick until cured.. Oh, and put a couple more drops of epoxy into the hole with the rod in place to wick out along the rod.

It's the same idea as a drywall anchor:

https://cimg7.ibsrv.net/gimg/bikefor...4b08c0000c.jpg

or using a glued in backer for drywall holes:

https://cimg2.ibsrv.net/gimg/bikefor...847c05d2b9.jpg

Tap the the hole(s), contoured rubber washer or a dab of silicone and insert appropriate sized button head screw that will insert a few mm into the tube. Not pretty but structurally sound.

I have seen dozens of Italian bikes with that exact drilling. I have owned at least 2. I never have seen a problem with it.

So again, done with bondo, it is a $10 fix. Dude to brass fill and paint, $1000 fix. Or do nothing. Or follow SurerRosa's lead. Nothing wrong with a sticker. All will yield the same result with different refinement.

Depends on how good you are with paint matching, touch-ups, etc., and how much you want to spend.

Trying to tap that thin-walled tubing for a screw is not advisable.

Large sequin and a pin; bend the sequin (with pin inserted) to get it through the hole,

Good point. I had images of the lead sleds I own which could take a lag bolt.

I had good results tin soldering cable guides with a 200W iron. But that was on a bare frame.

Adding to the dogpile here, my suggestion is to do the internal cable guide up proper-like, brazing in a stainless tube like Joe Bell does.

Doesn't exactly help the OP's predicament however. If I were Randy, I'd make a tight-fitting plug out of something plasticky and JB-Weld it in place. Then touch-up paint/blending/whatever.

Sadly, he's no longer around, but another competent and local framebuilder might be an option.

I've had two separate people send me requests to fix cracks on frames with holes like this, which biases my opinion. Both instances the solution would have been to replace the top tube, both times the frame wasn't worth the expense to the owners.

Perhaps the fact that people with problem frames tend to seek me out biases my perception of the magnitude of the problem. Anecdotal evidence is always hard to account for. We don't have any real statistical evidence.

Bondo won't stop a crack from propagating, but it will stop water and sweat intrusion. That's an area that gets a heavy dose of dripping sweat, so cleaning and filling or covering it makes sense to me as a minimum.

If someone gave me that frame, it was my size, and I wanted to ride it, I'd fill it in the method I posted, but my labor's free to me. I filled several cable guide holes in [MENTION=168558]Drillium Dude[/MENTION]'s Casati for aesthetic reasons, and it was nowhere near $1000. Most of my repair jobs get either paint patched (glossy black works out pretty well, for example) or powder coated (~$150 at my local place).

Maybe the best compromise is to fill it with JB weld, carefully sand it down trying to avoid damaging the surrounding paint, then patch, check the area often for signs of cracking, and ride it. Steel should give plenty of warning before failure.

I don't disagree. Where we probably differ is on the strength of a brass filler. While stronger than bondo, it is still extremely soft when compared to steel and I don't think it will do much to stop a crack from propagating.

I should mention that I plan a full repainting of the frame, followed with an application of art. I already have the art and I plan to mix Rustoleum paint to achieve a close color match and then apply the paint with a brush (I prefer brush to rattle can spray)...
https://cimg1.ibsrv.net/gimg/bikefor...86bcf7d3b7.jpg

We'll have to agree to disagree on the brass (bronze) filler. Bronze may not be as strong as the steel, but you can use more of it to compensate. That's why a bronze fillet brazed frame is as just as strong as a lugged one.

Crack propagation is a study in fracture mechanics, a field that I haven't studied much, but what you're trying to do is remove stress risers. In many cases you actually want a softer material. I wouldn't fill this hole with brass, I'd make/machine a small plug and silver braze it in. That keeps the heat affected zone down to a minimum. Filling that large a hole with brass filler would take some skill.

I did something similar to this a few years ago on a vintage Falcon frame.

https://cimg4.ibsrv.net/gimg/bikefor...d9e1491b34.jpg

https://cimg5.ibsrv.net/gimg/bikefor...a85779f8ee.jpg
Defluxed, filed and sanded the outside. Luckily a new wrap around Falcon decal hid the repair and no repaint was needed.

But, again, odds are nothing will happen on the OP's frame if he leaves it alone and just rides it, however the odds of a crack propagating are much, much higher with the hole (my 2 examples I mentioned earlier, for example). Ride it or not - that's a personal decision. I'm not saying it's a bad choice to not fill it. Saying it won't crack is just guessing, however.

Quote:

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Originally Posted by xiaoman1 (Post 22467599)

IMO,
I would not use brazing (heat) for a repair such as this. ..you may find that drilling the holes left a burr or high point around the hole, filing it or dimpling it will provide some "extra" hold for the filler. If you do not do this there is no way the Bondo will a stay in place when sanding the filler down. etc.
Find a small peening hammer or pick/scribe and just barley dimple the hole to allow for a thin layer of filler to adhere to the frame.
If this seems too drastic a solution (SMALL dimple), then I would find a suitable sticker or reflective tape and move on, watch for stress fracture (not likely) and it they occur us the more aggressive solution.
Best, Ben

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I agree that bondo is not structural and I do think that the holes are going to compromise the frame .....so an "extremely" small dimple will provide enough area to allow the filler to adhere without applying a backer. If careful when applying the filler very little filler will be required and touch up of the paint will be minimal......been there, done that.
If you think the holes will lead to a catastrophic failure of the frame then welding/brazing is the only way to go....lots of paint damage to the tube and a lot of paint work to look forward to.
To my eye, adding more decals where they shouldn't be will just draw more attention to the area in question a small touch up will soon be forgotten.
Again,,to me, KISITB
Best, Ben

tough call, in the late 40's and 50's this was not an uncommon cable port, albeit with a brazed on bezel.
Silver will "stick" to chrome. one could silver on a bezel, then repaint.
if the vents to the headset and or seat tube are big enough, a roofing "tack" might be slid inside point out and epoxy welded as a backer, then fill with more weld and grind/file back.

last would be a small section of sheet silver, cut to an oval and formed to fit the tube, bonded in place then filed a bit of an angled port, polish it up.

Then why just not braze in a steel rod? And fillet brazing works because of the cross-section of material, not a thin layer of soft material. Hence the "fillet".