Aluminium weld for a hairline crack on chainstay

[Hairy]

OK. so I went to Link because they were closest to me. The guy takes one look at the chain stay and says "No problem. I'll add a little gusset for strengthening Purposes" .

 

It took them a day. Here are some pics

awesome ... could I ask what they charged you for the works?

[BuffsVintageBikes]

Great stuff, let us know how it holds up

[edkin]

awesome ... could I ask what they charged you for the works?

The repair was just over R400

[Hairy]

The repair was just over R400

Bargain!

[aftershock]

Just a quick question while the people who know a bit about welding are still around on this post , if you have an aluminium frame with carbon seat stays with a crack in the aluminium , would the welding repair and "heat treatment" cause damage to the carbon ?

[MrJacques]

It might affect the resin that holds the carbon together.... ?

[Goosebay]

OK. so I went to Link because they were closest to me. The guy takes one look at the chain stay and says "No problem. I'll add a little gusset for strengthening Purposes" .

 

It took them a day. Here are some pics

Your weakest area will be where the paint went brown,  normally the frame re-cracks just next to the weld.  If a gusset was added that would mean more heat.  Hopefully they baked the swingarm in an oven and followed a good cooling protocol - otherwise you might have trouble quite soon.  It is very important to de-stress the weld with heating the whole frame - otherwise the areas next to the weld is going to be weaker than before.

[TyronLab]

Judging by the discoloration of just a small section they didn't preheat or post-weld stress relieve this weld, so Goosebay is on point. You're probably going to see a crack at the edge of the welded section, what's called the Heat Affected Zone (HAZ).

 

Also, never heard of a pencil grinder dudes? Neaten that **** up.

[MudLark]

Aluminium alloy welding is a complex thing to get right and much depends upon exactly what the alloy is to start with. There are various types of aluminium alloys and how they handle heat pr should be heat treated (some can't be) is very different. Those that can be welded and heat treated need to go through a few steps for it to be done properly... otherwise the material will be at risk of structural failure when stressed repeatedly. Judging by the quality of the welding and what you paid for it, I very much doubt whether what you have is fit for purpose.

 

A sudden structural failure at speed on a key component like a chain stay can lead to very serious injury. If it was me and I couldn't find a replacement swing arm either new or in good used condition (there is a Ghost agent in Honeydew, Johannesburg), I would simply scrap the bike. Some things in life just aren't worth it.

[edkin]

I think I may have found the cause of the chainstay crack. The shaft that goes through the bearing was slightly too large to go the the inner race without a lot of effort, subsequently made worse by having to hammer the shaft out of the race. 

 

The bearing was replaced but because it was difficult to get in the hammer was again applied subsequently damging the new bearing which soon siezed up. After mobility was lost the chainstay was left to take the strain causing the crack.

 

This my theory. Hope I'm right. Time will tell.

 

 

Before

 

 

After machining

 

 

 

[MrJacques]

Some older Scott Sparks had a similar issue where chain stays would crack if the pivot bearings weren't free to move.

[DieselnDust]

more and more modification only spells trouble.

[edkin]

I wouldn't call it modification. I would call it correction

[Andreas_187]

Just for future reference, the guy I recommended above repaired these. I told you he was the best!

[Andreas_187]

Just for future reference, the guy I recommended above repaired these. I told you he was the best!

[Wannabe]

Andreas, where is this welding guru based? 

Those 'spannies looks exquisite.