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-   -   Columbus SL Frame-Loose rear dropout (https://www.bikeforums.net/framebuilders/1201722-columbus-sl-frame-loose-rear-dropout.html)

merlinrkd 05-17-20 02:35 PM

Columbus SL Frame-Loose rear dropout
 
I have a home built Columbus frame. Builder unknown. Rumored to have been built by a wealthy man's teenage son. Circa 1980's. Has the rifled steerer tube. Columbus dropouts, Cinelli BB. Cinelli style fastback seat post binder. Forged crown. Bike was snatched at a garage sale by a friend. Frame and fork are very straight

I built it with budget components and gave it to a neighbors kid. He rode it thousands of miles. After a few years he said it made noises. Noticed a rear dropout had separated from the chain stay. Frame alignment wasn't affected.

Gave him another frame.

Wondering about a quick backyard fix. I have a torch and have done a fair amount of brazing. Built a Reynolds 531 touring frame in 1982.

I can see the affected dropout tang had insufficient bronze and poor penetration. It seems feasible to get a stick of low fuming bronze and flux. Heat it until the existing bronze is liquid and moves down the chainstay. Then add some bronze.

Any advice? Can't figure how to load pictures.

unterhausen 05-17-20 03:05 PM

Pictures: go advanced (at the bottom of a new post). Then "manage attachments"
If you need more instructions, let me know.

I think you probably want to try to clean out the stay a little unless it's a lot cleaner than I expect. Otherwise it will be difficult to get good penetration. Use a lot of flux. Concentrate the heat on the dropout until it gets hot enough.

Mad Honk 05-17-20 04:54 PM

Break out the torch and the boric acid, and braze away. Good luck re-entering the brazing group. Smiles, MH

Nessism 05-18-20 07:50 AM

Sounds fixable. I agree with unterhausen that cleaning is important. Some mild muratic acid in a bucket and soaking the stay end inside would be an easy way to clean it inside and out.

Andrew R Stewart 05-18-20 08:16 AM

Just make sure all that acid is cleaned off before both brazing and painting:) Andy

unterhausen 05-18-20 09:01 AM

TSP is less likely to cause corrosion, I think

merlinrkd 05-18-20 09:02 AM

Thanks for the help.I'm soaking the joint in some diluted pool acid

In looking thru my toolbox I have a jar of NOKORODE paste flux. Does that sound appropriate for bronze rod? It's very dark brown.almost black in color. I seem to recall the bronze flux was white.

I took a closer look at the other dropout and found Bondo underneath the paint at the dropout chain stay junction !! Hiding the failure to properly fill the joint. I'm thinking this was a high school shop project.

merlinrkd 05-18-20 09:09 AM

Added note. The job is growing. Checked the fork dropouts. More Bondo under the paint hiding the lack of bronze filling the joint.

unterhausen 05-18-20 09:10 AM

Dropouts seem to be tough for beginners. Makes me wonder about all the other joints though. That nokorode flux looks like an electronic flux. It's unlikely to be the right temperature range.

You don't have your location set on your profile. Most local welding stores don't have brass flux. It's possible they may have a powdered borax type, which is a pita to use. You can get Gasflux type b from most of the framebuilding suppliers.

merlinrkd 05-18-20 09:14 AM

Good tip. I was doing my brazing/soldering in the early 80's I lived in Modesto CA. I got silver solder and low fuming bronze rod locally. I could buy single sticks!! I used to have white flux but it dried up and I tossed it.

unterhausen 05-18-20 10:12 AM

the white flux was for silver. You can put water in dried paste flux and it works fine. Microwaving it speeds the reconstitution process, or just use hot water.
You can put powdered flux in hot water and it forms a kind of paste. Works okay. The real problem is getting it back off again. It requires nearly boiling water to do that, or chip it off mechanically.

Andrew R Stewart 05-18-20 08:26 PM

Agreed that the right flux for the filler is a must. Getting both from the same source will make this a no brainer. Get much more then you thing is needed as you'll want to practice a bunch before burning any flux on the frame:)

Tiny points of body filler is no big deal. Lots and when it's thick is much more an indicator.

Don't know what you mean by "pool acid". My experience with chemical cleaning prior to brazing never proved successful. Andy

Nessism 05-19-20 06:26 AM

Acid dipping is a good way to remove rust. I do a fair bit of motorcycle related restoration work, replating hardware myself using a zinc plating setup, and derusting and stripping the old plating is step one in that process. You can dip an old rusted fastener in diluted acid solution and it will remove all the red rust down to base metal pretty quickly. It's important to not leave the part in the sauce too long though or it will remove metal and cause the metal surface to develop a blackish coating. Soaking that stay in the sauce, minimum time needed to remove the rust, followed by dunking in some baking soda solution to neutralize, will work fine.

unterhausen 05-19-20 07:25 AM

Don't the fumes from muriatic acid cause corrosion? Seems like I have heard of people corroding everything in their garage with it.

Nessism 05-19-20 03:54 PM


Originally Posted by unterhausen (Post 21484133)
Don't the fumes from muriatic acid cause corrosion? Seems like I have heard of people corroding everything in their garage with it.

I use it outside.:lol:

unterhausen 05-19-20 06:42 PM

where do you store it?

Nessism 05-19-20 06:43 PM

I've got a gallon jug purchased from the hardware store. I store the jug outside but it's sealed so not sure it matters where it's stored.

unterhausen 05-19-20 08:45 PM

the reason I decided to avoid muriatic acid is because the web has a number of stories from people that were careless storing it and had every steel thing in their garage covered in rust. I'm horrible about putting lids on properly.


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