Broken Braze-on on an Aluminium frame

[jasonsankar]

Hi all- I just broke off the rear cable stop for the rear brake on my Cinelli Proxima frame. The part came off cleanly, with no damage to the top tube. Right now I am using a full length piece of housing zip tied to the top tube to bypass the cable stops.

My question is this:


Is it possible to get the part re-attached? Can I use some kind of glue to re-attach the piece? (I don't want to ruin the paint if I don't have to...)

Or should I just forget the cable stops and stay with the old- style full housing run to the rear brake?


Thanks

Jason

 

[dabac]

I just broke off the rear cable stop for the rear brake ...
Is it possible to get the part re-attached?

There are several options:

1) Glue it back using a high quality epoxy like Araldite. If you bed it in a bit it might actually hold and give you the most invisible repair.

2) You can solder it back on using a low-temperature solder and a soldering gun. This will be stronger but might give some discolouration around the repaired area.

3) Have someone braze or TIG-weld it back on. Will definitely cause some paint damage but will offer the strongest repair.

4) use something like this http://www.cambriabike.com/brakes/alloy_backstop.htm. It sure looks better than zip ties...

 

[boudreaux]

There are several options:

1) Glue it back using a high quality epoxy like Araldite. If you bed it in a bit it might actually hold and give you the most invisible repair.

2) You can solder it back on using a low-temperature solder and a soldering gun. This will be stronger but might give some discolouration around the repaired area.

3) Have someone braze or TIG-weld it back on. Will definitely cause some paint damage but will offer the strongest repair.

4) use something like this http://www.cambriabike.com/brakes/alloy_backstop.htm. It sure looks better than zip ties...

It's aluminum! Solder or brazing only works with steel.

 

[Weisse Luft]

It's aluminum! Solder or brazing only works with steel.

I would recommend AGAINST any heat process because almost all aluminum frames are heat treated after final welding. Any heat over 300 F will ruin the heat treatment and could cause failure.

Look for a riveted cablestop or something like Cannondale's rear cable stop.

 

[ewitz]

You can get it riveted back in place.

 

[BIANCHI_EURO]

Hi,

So the cable stopper came of the tube, right? I think TIG welding will be extremely difficult taking into account the thin wall thickness of frame tubes nowadays. It's real easy to mess the whole thing up and burn a giant hole into the tube. I have seen the result of a test at the Principia bike factory. They asked a group of about ten top bike mecanics to weld a stopper on a piece of frame tube. What a mess!!!

You need an expert TIG welder who does this job every day if you really want to do this. (The factory guy did it again and again without any trouble).

I have been checking one of my frames and I see the stoppers are nailed (we call em "watertight pop nails", I am not sure for the English equivalent). I am talking about a carbon frame now. I am not so happy with this discovery since four unnecessary holes are drilled in my frame tubes. Amateurs!

My experience with gluing aluminium with epoxy are really great. Advantages:
No drilling in the tubes, no heat stresses in the metal, no paint damage, no accident possible (burning a hole), when the construction collapses you can still try something else.

The epoxy anyone can buy in a handy market will do fine. Do you know the dual injection needle package? They sell it here by Bison brand. I never tried the epoxy paste, but I think for your purpose it might be the easiest thing to work with (least change on messing up). (The expensive epoxies are usually so expensive because with this epoxy the fibres can be penetrated better creating a better laminate). If you use fluid resin, be sure to let the resin thicken up a little first so the viscosity is approaching say... ice cream (otherwise you might drip).

Regards, Frank.

 

[Weisse Luft]

Hi,

So the cable stopper came of the tube, right? I think TIG welding will be extremely difficult taking into account the thin wall thickness of frame tubes nowadays. It's real easy to mess the whole thing up and burn a giant hole into the tube. I have seen the result of a test at the Principia bike factory. They asked a group of about ten top bike mecanics to weld a stopper on a piece of frame tube. What a mess!!!

You need an expert TIG welder who does this job every day if you really want to do this. (The factory guy did it again and again without any trouble).

I have been checking one of my frames and I see the stoppers are nailed (we call em "watertight pop nails", I am not sure for the English equivalent). I am talking about a carbon frame now. I am not so happy with this discovery since four unnecessary holes are drilled in my frame tubes. Amateurs!

My experience with gluing aluminium with epoxy are really great. Advantages:
No drilling in the tubes, no heat stresses in the metal, no paint damage, no accident possible (burning a hole), when the construction collapses you can still try something else.

The epoxy anyone can buy in a handy market will do fine. Do you know the dual injection needle package? They sell it here by Bison brand. I never tried the epoxy paste, but I think for your purpose it might be the easiest thing to work with (least change on messing up). (The expensive epoxies are usually so expensive because with this epoxy the fibres can be penetrated better creating a better laminate). If you use fluid resin, be sure to let the resin thicken up a little first so the viscosity is approaching say... ice cream (otherwise you might drip).

Regards, Frank.

Epoxy will work for a time but without proper preparation of the surfaces, it will eventually fail.

Acrylates are generally a better bond on aluminum when the dircetions are followed. These are generally not a consumer item and you have to go to an aircraft specialty distributor for this. Also, some of the chemicals used are not too friendly to the bodyso read understand and follow the directions and MSDS's provided.

I don't have any idea of the size of the stop but IMHO, a pop rivet with acrylate adhesive would be stronger than welding, even considering the required hole in the tube.

 

[tafi]

Epoxy will work for a time but without proper preparation of the surfaces, it will eventually fail.

Acrylates are generally a better bond on aluminum when the dircetions are followed. These are generally not a consumer item and you have to go to an aircraft specialty distributor for this. Also, some of the chemicals used are not too friendly to the bodyso read understand and follow the directions and MSDS's provided.

I don't have any idea of the size of the stop but IMHO, a pop rivet with acrylate adhesive would be stronger than welding, even considering the required hole in the tube.

I would seriously avoid any heat or riveting to a tube that has not been designed to be riveted. Holes create an incredible stress concentrator which will ruin a frame if theyu are not designed for. Get some professional advice.

 

[dabac]

Solder or brazing only works with steel.

Yeah right, and screws only comes in right-hand threads...

Here's a product from a well-renowned industrial supplier:

Solder for aluminium, ALUSOL
Mfr. Multicore
Solder with water-soluble four-core flux. Suitable for soft soldering of aluminium, stainless steel and other low alloy metals. Not suitable for electrical joints and duralumin. Normally requires no prior processing of oxidised surfaces. Alloy: tin 18 %, lead 80.1 %, silver 1.9 %. Melting temperature between 178–270 °C. Suitable tip temperature 350 °C.

More:
Stock number: 82-912-13
Product name: Aluminiumsold. ALU-SOL
Manufacturer: Multicore
Type designation: 50 916 40 45D ALUSOL 1,2
Country of origin: United Kingdom
Data sheet: 08290769.pdf
Unit: Piece
Original package: 20
Sales package: 1
Replacement:
VAT (or equivalent) rate: 25%
Minimum order quantity: 1
Dimensions (package): 60X35X60 mm
Weight (package): 250 g
Informative text:
Catalogue page / Catalogue number: 1954 / 52
Customs number: 8311300000
UNSPSC: 23171509

Available to anyone with a credit card and a mailaddress from http://www.elfa.se/en/

Or check outhttp://www.alutite-world.com/eng/index.htm for a slightly warmer method.

Now what do you say?

 

[boudreaux]

Yeah right, and screws only comes in right-hand threads...

Here's a product from a well-renowned industrial supplier:

Solder for aluminium, ALUSOL
Mfr. Multicore
Solder with water-soluble four-core flux. Suitable for soft soldering of aluminium, stainless steel and other low alloy metals. Not suitable for electrical joints and duralumin. Normally requires no prior processing of oxidised surfaces. Alloy: tin 18 %, lead 80.1 %, silver 1.9 %. Melting temperature between 178–270 °C. Suitable tip temperature 350 °C.

More:
Stock number: 82-912-13
Product name: Aluminiumsold. ALU-SOL
Manufacturer: Multicore
Type designation: 50 916 40 45D ALUSOL 1,2
Country of origin: United Kingdom
Data sheet: 08290769.pdf
Unit: Piece
Original package: 20
Sales package: 1
Replacement:
VAT (or equivalent) rate: 25%
Minimum order quantity: 1
Dimensions (package): 60X35X60 mm
Weight (package): 250 g
Informative text:
Catalogue page / Catalogue number: 1954 / 52
Customs number: 8311300000
UNSPSC: 23171509

Available to anyone with a credit card and a mailaddress from http://www.elfa.se/en/


Now what do you say?

Well, how about that. Actually I realized the error of my ways in rembering that soldering also works on copper, brass,gold silver, and a number of other things.

 

[Weisse Luft]

I would seriously avoid any heat or riveting to a tube that has not been designed to be riveted. Holes create an incredible stress concentrator which will ruin a frame if theyu are not designed for. Get some professional advice.

See my post #4 above on heat treated aluminum.

No, a small hole would not be a significant stress concentration in the top tube, especially at the neutral axis of the top tube where the section acts in primary bending as a shear web. Holes in plates is a classic theoretical topic of Timishenko et al... I think I know what I am talking about here...

Furthermore, the effect of a hole would be offset by bonding of the cable stop to the surrounding area.

Yes, when people were getting "stupid light" by drilling holes to reduce weight, bad things happened. But a single rivet hole in the top tube isn't going to cause any problems.

 

[boudreaux]

I have plenty of aluminum frames with rivet holes for the cable stops at the front and rear of the toptube. Tube ends are if butted are thicker there too. Aluminum frames typically use rivnuts in the seat and downtubes, even where the tubes are thinner , for water bottle bolts and there are often holes in the seattube for braze on derailer hangers.

 

[dabac]

I would recommend AGAINST any heat process because almost all aluminum frames are heat treated after final welding. Any heat over 300 F will ruin the heat treatment and could cause failure.

That's why I suggested the solder that can be worked with a soldering gun. I'm not sure about where it would end up on the Fahrenheit scale, but as these things goes it's still a very localized and limited heat input.

 

[BIANCHI_EURO]

Hi,

I checked the Columbus manual on this issue. Maybe interesting to let u know:


"The cable stops may be riveted or braze welded in the thickest zone of the tube. It is advised against welding or riveting elements in the inferior semipart of the down tube".


Still I don't understand why they do not just glue it with epoxy. No holes, no chance on failure burning a hole, easyer, much lighter. I strongly dissagree with the argument made that epoxy will eventually fail. Epoxy is incredibly strong, will not be subject to corrosion and if that isn't enough you can reinforce it as a composite with fibre. But hey!.. what are we talking about, a cable stopper. We don't have to glue a Bush to the white house. Of course like allways you need to prepare the surfaces before glueing. And be sure to remove minimal (almost nothing) material from the frame tube. My experience glueing heavy duty windsurfmasts used in meters high surf is that the bond will last forever. The mast will eventually break on another place.

Regards, Frank.

 

[dabac]

Hi,

My experience ...is that the bond will last forever.

I've had some mixed experiences of glueing metal. Even some low stressed items have come off despite decent preparations (sanded down and degreased surfaces). But sure, it can be made to work too.
IMO a soldered joint is easier to check for quality, if the solder "wet" both surfaces then the strength of the joint will be equal to the strength of the materials used. A glued joint with insufficient adhesion will look just like a good joint until you pull on it.

If the cable stop came with an extended base (the size of a coin or so), then I'd be much happier with glueing it on.

 

[BIANCHI_EURO]

I've had some mixed experiences of glueing metal. Even some low stressed items have come off despite decent preparations (sanded down and degreased surfaces).

Hi,

I have quite a lot of experience with polyester and epoxy laminates building windsurfboards for many years. My experience (and that of many others) is that epoxy resin is a mirracle material. The only negative thing is that it is very poisonous (can induce cancer). I have to admit that I often receive remarks like "you wanna use epoxy for everything exept on your bread".

When I read your message I rememberred I forgot something important. When using epoxy resin, one should wait at least a few days before using the bike. Unlike other glues epoxy doesn't dry to the air, it's a chemical reaction (H-bridges). The resin is completely hardened two weeks after applying (dependent from type of resin). Another reason for failure could be an incorrect mixing ammount of resin with hardener. This will indeed definitely result in failure. However with most handy market sets it's very easy (usually) 50% vs 50%. Hardening at higher temperatures in a dry atmosphere will give better results.

If it's a black bike, take into account the exo-thermic reaction heat coming free. Once I laminated a full carbon (black) windsurfboard. The weather was very sunny and the bow of the board stuck out of my workplace. Due to the reaction heat it caught fire.

Regards, Frank.

 

[BIANCHI_EURO]

Be sure to do thorough mixing