Frame Damage

[jrsunt]

To all you people in the know, what do all these marks in aluminium mean. Frame took a massive impact around that area. Is it kaput?

[kramit]

The paint is cracked???

[jrsunt]

Its anodised not painted. The marks run from the brake pedal mounting point all the way down to the bottom of the frame, but only on the inside, which confuses me slightly because thats where the compression has taken place, I would expect to see those (stretch marks) on the outside where the tension has taken place. (correct me on the science please)

I've snapped those off before on the mont, but never seen what has caused or the process of it breaking.

C'mon all you engineers out there.

[steveo]

dadof2 will have an answer, you will probably need a heavier bike JR

[copemech]

It means the area has been stressed, not necessarily cracked or broken. Ali is a great material in that respect as it will flex and come back, at least once or twice!

If unsure, overly concerned, fix would be grind the anodize off and run a bead of reinforcement weld around it is it is that critical of a point.

[sherpa325]

I think the technical term is wrinkling and is normally associated with sheet metal failure. As copemech suggested I would grind the area until smooth and fill with weld as there appears to be plenty of room to add a reinforcing weld

Cheers Greg

[ourian]

It is possible that it's just the anodising that has cracked, the anodised surface is harder and more brittle than the aluminium underneath, so where as the aluminium will bounce as it were the anodising won't.

Personally I wouldn't do anything other than keeping a close eye on it should a larger crack develop.

[sportsawyer]

What was the nature of the impact?

A very hard, head-on hit of the brake pedal would cause bending rotation that would result in tension in that area (backside of brake boss).

If that's the case, it could be just crazing of the brittle anodized surface, like others have already brought up.

Here's a link to an explanation of anodized surface crazing:

http://www.aacron.com/docs/Crazing%20Caused%20By%20Bending%20and%20Forming%20Operations.pdf

I've seen a lot of crazing radiating from spoke holes in hard-anodized bicycle rims. The rims lasted and cracks didn't start (or go to failure / nipple pull-through) in the aluminum rim.

There still could be underlying cracks starting in the alumimum frame, so keep an eye on it as suggested.

[perce]

What was the nature of the impact?

I'd have thought 84 miles of balls out over the back & right hand to the stop.

[jrsunt]

84 miles and 1 stone that I knew was there.... sump guard, brake pedal and footrest slowed me down quite quickly

I've taken it someone in the know, and they said the same. If they were to try and weld it, it would ultimately weaken the whole area, so its best left alone and weld as a last resort.

Edited December 8, 2014 by jrsunt