My broken Scott

[TooManyMatts]

My Scott Genius mc20 2005 frame has cracked. Scott's "lifetime" warranty only covers four years!!!!!!!!! so it wont be replaced.

 

 

 

I want to look at attempting to fix the crack and where better to ask than on the hub.

 

 

 

The crack is here:

 

 

 

 

It goes down the dropout lug about 4 or 5mm. Here is a closer picture:

 

 

 

 

I thought of taking it to a welder who specializes in aluminium. I am worried that the high temperatures of aluminium welding will damage the carbon or weaken it to the point when it breaks and the whole exercise and expense is for nothing.

 

 

 

Is this job possible?

 

Is it advisable?

 

Has anyone got suggestions?

 

 

 

Thanksmatmum2009-07-24 15:16:50

[Pr0PheT]

 

Your best bet would be to weld it, aluminium welding does not require temperatures as high as conventional welding, depending on the purity of the aluminium it can be welded at about 700 degrees celcius, the carbon depending on it's production process can easily withstand anything from 1500 to 3000 degrees celcius.

 

The only problem with repairing an area that is subjected to constant tension forces the one side may be stronger by welding it which places more stress on other areas which may cause another crack elsewhere.

 

Pr0PheT2009-07-26 06:18:53

[paulvs]

for peace of mind I would recommend investing into a new frame.

[David #7]

That little crack can be fixed. A good engineering shop will do it. Where do you live?

[Capricorn]

new frame, or have someone CNC you some new mounts. Welding to the BB and the remainder of the current mount which should be ground off, will give a better result. In fact, have them redesign it so the webbing is a bit thicker, giving better resistance to the failure you just experienced.

[johannrissik]

The Scott "Lifetime Guarantee" covers the average lifetime of a guinea-pig. It's in the fine print.

[Christie]

Is it a carbon frame? It looks like that from the pics.

 

I don't think it will be expensive to weld up, so it may be worth giving it a try.

 

If it is a full alu frame, welding up the crack may work. Most aluminium used in bikes are age hardened. Welding will work in the short term, but the heat pumped into the component will undo the heat treatment given to the part initialy. It will reduce its mechanical properties, and cause it to break again. Imo it would be ideal if the fix could be heat treated after welding to restore the original material state. But it may be worth t

 

If it is a carbon frame, with the BB bonded in, the risk of failure is higher:welding may cause a disaster: most composites can not handle high temperatures. The carbon fibres are not the problem, but rather the epoxy resin that holds them together. I would guess that the epoxy used in bikes melt at about 80 to 100 degrees C. The second problem would be that aluminium conducts heat very well, and welding would heat up the bonded in part significantly. I don't think the glue bonding the insert to the carbon will handle lots of heat well.

Another problem with welding the aluminium inset on the frame, is that the thermal expansion coefficients of alu and carbon composite is verry different. This means that the heat will cause the alu part to expand a lot more in size than the composite surrounding it, causing thermal stress.

 

From the pics, it looks as if the carbon starts far away from the area of the break - if that is the case, welding it may still work.  

[TooManyMatts]

Thanks for all the input.

 

 

 

It is a carbon frame. The aluminium insert goes about 30mm into the tube and the carbon overlay comes right down to the lug.

 

 

 

SO like Christie said (and for the same reasons given) a simple weld will almost certainly ruin the frame or cause cracks that may end in a helluva crash for me.

 

 

 

What I am trying now is to weld a steel support structure together that fits over the lugs. It is both screwed and epoxied to the frame. It looks good so far and you will barely be able to see it when all the bits are back on the bike. I just painted it tonight so I'll let you know how well or if it works.

 

 

 

I'm with johannrissik. A spade needs to be called a spade. Why say "lifetime warranty" if you mean four years????!! I think its absolute crap that they are allowed to define what "lifetime" means.

[Capricorn]

that lifetime story is just about everywhere, and i take my example from the PC industry. Flash drives for example, are often branded in bold bright front with the words, LIFE TIME WARRANTEE. but there is always a little asterisk attached, which the fine print translates properly to limited lifetime warrantee. In the PC industry. LLW means it's only warranteed whilst that product is in production. Kinda makes sense. but I do agree the lifetime warrantee schmiel is a bit of a bear trap in disguise, ie, not to be taken at face value.

[Christie]

Please post some pics when it is finished. Sounds like an interesting solution.

 

 

[Free]

Weld it. I had an alloy ds frame welded on about the same spot. Its been more than a year now and its still 100%. And I ride it daily.

[Dirty Twin]

Send Azonic a PM he has just done some repairs like this recently.

[Plentipotential]

That looks like a bad design to start with. The carbon might very well take the heat from welding, question is will the epoxy resin used take the heat. If I were you I would start at the agents for Scott, they might just have some experience in this matter.

[TooManyMatts]

Scott fell through badly, the frame was not weldable and a new frame was too expensive.

 

 

 

The only option was to fix the damn thing. My father designed a kind of brace that sits between and round the existing lugs. It's made of steel.

 

 

 

Here is the fix looking at it from the top (bike upside down). The arrow points at the rounded part that fits snugly round the aluminium of the frame. There are 3 screws that bolt through the aluminium to another rounded steel plate on the inside of the frame. The whole brace is glued in with a lot of epoxy.

 

 

The arrows here show the lugs that sit inside the existing aluminium lugs and take the weight of the rear triangle

 

 

One last picture from the side.

 

 

Yes it makes my carbon bike weigh more than an alu bike... but I am really happy with the situation because it cost me nothing and I have my beautiful machine back.

[Gasping]

Looks like a decent "jerry-rig" solution to a budget problem. I hope this lasts and lasts and lasts until you can afford a new bike of your dreams.

[AndreZA]

goodness gracious, what did you rape those bb cups with?