Why identical frames weigh more sometimes
 

Was modding a frame and found a suprise inside. Figured some here might get a laugh out of this.
https://cimg9.ibsrv.net/gimg/bikefor...d14f5ddb9b.jpg

OMG, can you tell what that material is? Lead solder maybe? That's effin' hilarious.

At a shop where I worked once, there was a sales guy who got a new tri-bike and someone there thought it would be funny to fill the frame with steel shot, from a shot-blasting cabinet. I don't remember what the victim did to deserve that but I gather it was well-deserved. It took him a long time to notice, like after a few races. I also heard of a solid steel mandrel being dropped into another guy's seat tube, full length from the BB shell up to the bottom of the seatpost. Even heavier than steel shot, which has air spaces in it.

Could this be another prank, or was it an attempt to stiffen the frame, or repair a crack? The mind boggles.

Mark B

Strategic ballast makes you go faster

Its bronze, how it got there, no idea, maybe when the dropouts were brazed on? It hasnt been repaired from what i can tell.

I suspect this frame was hearth brazed with a coil fed filler. Inattention, lack of skill, just because one can and a whole lot more filler was fed into the chainstay/shell joints. It would be interesting to see if the shell had a brass coating on most of it's interior surfaces too.

Or someone loaded the chainstays with a few too many preform filler rings. Andy

As someone who has now built the large bits of exactly one frame I can attest to lack of skill being at least one cause for much excess braze metal winding up in places where it does nothing but add weight. :(

Are you all talking about the shiny soldering material or the rust-colored plates that (especially in the left chainstay) look like tilted discs?

Carbon-fiber frames are often ( slightly ) heavier or lighter than expected due to resin flow or drip-out,at least that was the case, anyway, 10 years ago.
For instance, BMC frame builders would badge/decal the lighter frames Roadmachine and the heavier ones Racemachine although the frames are outwardly identical.

I love this pic of a BMC Team Machine that tore in half, in the perfect place to where the decal now says "Tear" Machine. I wonder if tears were shed, over that tear?

https://cimg9.ibsrv.net/gimg/bikefor...4246fb386d.jpg

Also on the subject of unintentionally funny decals, there's this one named after the 5 points where it'll break if it actually gets ridden:

https://cimg2.ibsrv.net/gimg/bikefor...6a109c1fe1.jpg

And this one, also named after the point where it will break:

https://cimg0.ibsrv.net/gimg/bikefor...2ad53ee4f5.jpg

I suspect the tear machine was made of carbon with a manufacturing defect.The five points I wonder about the stability when riding....

It seems obvious to me, the BMC broke its toptube only after the DT pulled out of the HT lug. No defect needed in the CF; nearly any TT of any material would break if the DT is not longer connected. So the defect is clearly in the glue joint between the CF DT and the lug, which appears to be aluminum. Al and CF have different electric potential, so in the presence of an electrolytre you will get galvanic corrosion. Also different thermal expansion coefficients, so heating/cooling cycles might tend to break the joints apart if not done right. Just guessing at reasons the glue joint came apart, but I don't think there's any question that the glue joint is 100% to blame here. I mean, the CF in the TT could also have a defect, but that's moot once the DT pulls out.

That is just wild.
hearth brazing or not, considering the "waterline" of the bronze, I would have expected the bottom bracket shell to be filled solid too. The shell does not appear to me to have a closed off wall at the chainstay spigots.