SJX426 

I have acquired an early '71 frame with two holes added to the top tube for internal cable run. The holes are on the sides of the TT not the top or bottom but on opposite sides.
I believe the tubes are Columbus Allle or SL. No decals on the frame to identify.
The holes were filed so they are oblong to accommodate the angle of the cable housing. I am sure the structural integrity has not been significantly jeopardized.

The holes are about 5 mm from the eye-balled end of the top tube where it intersects both ST and HT with the other end of the dimension being the far edge of the hole from the ST/HT. Overall length of the TT is about 57mm. The vertical dimension of the holes are 7mm.



I have options:
1. leave them alone and go with the Patina of the frame finish despite the modification.
2. Add braze-on reinforcement pieces.
3. Fill them.

I am interested in understanding if it is even viable to fill them and if so, what would be the approach?

unterhausen

my temptation would be to fill them with metal filled epoxy so you could tell if they are cracking. This has the advantage of looking original and saving the paint, if that's important. It looks like they left a burr on the inside, but it's difficult to tell from a picture.

One complication for adding reinforcements is that there is chrome there, which should be removed for the health of the person doing the brazing. And then you're left with a big patch of no paint. You can tie wet rags to the tube to minimize paint damage, but there will still be a circle missing paint. Here is an instagram post showing what's possible https://www.instagram.com/reel/CfWau7ID1Ml/?

SJX426 

@unterhousen - thanks for that added option! What would you use as a backing for the epoxy? I kinda like this option.

guy153

Epoxy sounds like a good option as the holes are "non-structural". Otherwise I would cut a piece of sheet metal to fit in the hole as they are quite large and then TIG braze it in, a bit below the surface, so it could be covered in braze (and/or car body filler) and sanded smooth. The heat from TIG is quite localized but wet rags around the chrome bits still a very good idea.

unterhausen

if you were going to use epoxy, you would have to clean the holes. Maybe fill it in multiple steps. Or I'm thinking that wrapping with plastic wrap after you put the epoxy in the hole. Obviously, I have never tried this, except on multi-million dollar fighter jets.

SJX426 

I was thinking some kind of backing put in the hole with something like floss with a little tension to pull it toward the metal and then filling the void and cutting the floss. Then sanding it down.

bulgie 

Some decades ago I used a product called Heat Fence. It was like putty or clay, moldable, sticks where needed. You can build up a little volcano caldera around the spot, so it directs the flame up and away from adjacent paint too (not relevant if TIG welding). Might be the same as this stuff, found with a web search. Not endorsing that seller, just the first good google hit. Another one to maybe try is Markal "Block It" Heat Absorbing Paste — never tried it but it sounds interesting.

Having used both Heat Fence and wet rags, I'd say the heat fence is better, by enough to be worth tracking some down.

Oh cool, check it out, WetRag is a trademarked product! Gotta get me some WetRag!

Mark B

Andrew R Stewart 

I have gone through a couple containers of these products. (IIRC it was Heat Fence that I used). When the stuff was fresh and moist it worked very well. Some of the stuff was able to be scraped off and remoistened to use again. But there is a loss with each use and the stuff can dry out over time. As I moved on from doing repairs to "clean" work I found I didn't need the stuff. Andy

bulgie 

I wonder if you could expand on this. I was under the impression that brazing over chrome plating wasn't too bad. All the articles I've seen on chrome-6 (hexavalent chromium, a known carcinogen) mention it being created from the intense heat of arc-welding.

I'm definitely not an expert though. If the fumes from brazing on/near chrome are known to be bad, any chance of getting a reference for that? Note I'm not asking you to do my homework for me, just thought I'd ask in case you had that info handy.

I'm all for caution for caution's sake though. Lungs are touchy things, but good to have!

When brazing on repairs where there can be some paint burning, I use a cartridge respirator with cartridges made for organic vapor, with a HEPA filter on top of that. I easily believe that would not be approved for chrome-6. I've heard it said (don't quote me!) that metal fumes are usually in the form of tiny blobs, not a gas but rather a fine particulate, and HEPA is good at taking them out. I've found that to be true for the zinc that boils out of brass ("bronze"), but maybe chrome is a whole 'nother thing. The zinc is not very toxic at low concentrations, so letting a little through won't kill you.

Another thing I've done with chrome is cover it with flux, i.e. what you're doing already. I recently silvered a chainstay housing stop on a chrome "sock", where I removed chrome down to shiny steel only at a tiny dot, the same size as the foot of the braze-on or a little bigger. With an unbroken layer of molten flux over the whole hot area, I can't imagine much fume could be coming through that for me to breathe. Maybe wishful thinking?

I asked my HMO if I could get some test for accumulated heavy metals in my system (cadmium maybe?) but they don't want to pay for the test unless it's ordered by a doc, who'd need to see symptoms I guess. Cheap bastards! I don't even know what tests are available though, maybe they have to biopsy my liver or bone marrow? I sure wouldn't do that out of idle curiosity.

Mark B

unterhausen

yeah, I don't know for sure. But I have asthma, and I don't want to make it worse. I feel like it's easy enough to get careless and overheat things enough to make metal smoke.
they do make filters for that though, I have some.

suprchunk

Eastwood sells something similar. I haven't had a chance to try it, but I was going to on my 51 Ford F1 rebuild. But moving put a damper on that.

SJX426 

So here is an approach I think might work.
I obtained a fine screen from a tea fliter and cut it out.


Cut a piece for the hole.


So the next challenge is how to hold it in place inside the tube.
1. Use a string like floss attached to the center and pull up while applying the steel impregnated JB Weld. Challenge is to keep the right amount of tension for a period and then cut the string.
2. Insert a balloon into the TT through the hole in the seat tube and head tube. Blow it up just enough to hold the screen in place. Challenge is getting the balloon in and it not rupturing.

Thoughts?

I am working on determining the approach for touch up paint.

bulgie 

Looks promising, thanks for the update. Watching with interest to see next steps.

Tension on the floss could be applied by a clamp-on block near the repair point, with some sort of "gallows" attached to the block, hovering over the site.

For the block I was thinking something like the classic design that Alex Meade sells for $30, a bargain IMHO:
https://alexmeadetools.com/?product=...oval-and-taper
Maybe $$ just to do that one repair, but I find lots of uses for them. A DIY block could be free or nearly so, just the cost of your labor to make it from scraps.
The gallows bit could easily be a scrap of metal off the shop floor, pinched into the slit of that block while tightening it.

Nessism

Duct tape to keep water out.

suprchunk

That screen is SS. Is the bike frame stainless steel as well? I don't think it is.

You may have corrosion issues mating two dissimilar metals together.

I'd cut a piece of steel, same material as bike or as close as possible, tack it in, then weld it in completely (moving around, a little at a time, etc.)

You could even braze that in since it isn't structural.

unterhausen

I'm not sure I would worry too much about corrosion.

It's going to be difficult to get that screen in full-size. You don't need it to be full size, you just need enough of a backer to keep the filler from sagging too much. And you can re-apply if there are gaps.

If the frame were worth fixing correctly, I think the tube can be replaced without killing the lug chrome. Gugie has shown the way with replacing fork steerers. That would be my approach

SJX426 

Thanks for the feedback from everyone. I am not too concerned about corrosion between the SS and the tube. I suspect it will be mostly covered with the JB Weld.

Here is my approach.
First step is to clean the hole and as much of the inside surface as possible. A set of SS, Brass and Nylon brushes of assorted sized was acquired and will be my best shot at cleaning the surfaces.
I found bailing wire with a small diameter in SS. I punched it through the screen and bent the end to keep it from coming out


The frame is mounted in the stand next to a table with the BB shell resting on the table so the hole is straight up. Keeps the JBW from running.
A spoke whose head failed, is bent slightly to raise it off of the TT when mounted in the clamp. The clamp keeps it secure.


The spoke provides some spring to hold the backing screen in place via the bailing wire.
The screen is inserted into the oblong hole for placement. The screen is shaped to the radius of the tube over its length.

Once the screen is in place, the JBW will be applied on the perimeter and allowed to set.
With the screen bonded to the inside of the tube and edge of the hole but not the middle of the screen, the bailing wire will be removed by rotating the long part to allow the "hook" to come out the hole. Then the final application of JBW will fill it in.

Then the final challenge will be to blend the fill to the surface of the tube.

A Jewlers file was used to remove the burrs from the hole edge and to add a bit of a chamfer to allow the JBW to "flange" over the hole on the outside.

I will likely try this tomorrow morning when I have uninterrupted time. If the weather is good, I will go for a ride instead and do it on Sunday.

guy153

Tack a piece of wire a few inches long (1mm welding rod would be a good choice) to the centre of the mesh (before inserting it into the frame). Put a loop in the top of the wire and tie string to that and around a rafter or something to get the tension right (a taut line hitch is a good knot to use for this). When it's all good just put a few "tacks" of JB Weld to start with and after that has set cut off the wire and push the centre in just enough that it's all just below where you want the final surface to be. Put JB Weld over the rest of it.

SJX426 

Update:
Decided to solder a wire (SS) to the screen (SS). I happen to have the right flux and solder. I let the wire protrude about a diameter on the other side of the screen and soldered it together.
I had to trim the screen just a little to get it in the hole. used the wired to wrap around the spoke for tension then added JBW.

Let it dry overnight and then sniped the wire off with cutters. This left a protrusion of the wire sticking up.


Then took a dremel to the protrusion to lower it below the surface of the tube.


The JBW was not very flat and did shrnk or sunk into the screen. There was a small amount of JBW on the edges above the surface of the tube. A flat wide fine file was used to remove any JBW material above the surface.


Going to do the other hole next.

My thinking is to use body filler to fill in the voids to blend into the tube. I will likely loose some paint but there are much larger spots of chrome exposed elsewhere on the frame. If I can get a match on paint (oh boy!) then it will be less noticeable and look much more acceptable.
Don't know how long that will take so will update as completed.

unterhausen

That looks good

SoCaled 

I was so rooting for the balloon! love the ingenuity and just plain funny. Although taking that thought to its logical conclusion, it does seem using a bike tube in the same way as a balloon might solve the rupture issue and keep it "in the family", insert and then inflate? or even cut an old tube off and knot the end, so you could go in without doubling over?

The other classic is a foam backer.
love your creative thinking to get this done

unterhausen

There is no way to get a bike tire tube into most top tubes.

Inusuit

I think the OP has an elegant plan.

SJX426 

Thanks all for the comments! I thought of a balloon but as stated, hard to get one in the TT with the small holes:



The con to using a balloon was the risk of it popping from the edges of the screen. I wanted to use the screen to provide some support of the JBW. As viscous as it is when wet, it does tend to migrate while it is curing. The second hole had a much better result with the slightly extra JBW to file down.
PXL_20220923_121037321.PORTRAIT on Flickr

The next challenge is to determine what to do about this damage for chain suck! The black paint helps obscure the damage but the rough edges helps point it out. The damage looks like an extension of the dimple toward the shell


Any suggestions?
`````

SteelyMan

Sorry no suggestion for the chain stay. That lugged BB sure does look nice. So many lugged frames have ‘utility’ lugged BB with no scroll work whatsoever. If lugs are not scrolled I’d rather not even have lugs.