Antieverything,

Good eye.

BTW, that's an ATAX pressure cast aluminum stem (euphemistically called "melt forged" by the Japanese in "Jinglish"). ATAX was part of Phillipe.


There were millions of cast aluminum bike stems produced from the 1930s up to the present. They were made by dozens of companies. For example from the C&V era alone:

France
ATAX
AVA
BELL
BELLERI
BF
CTA
GUID
MILREMO - Made by Phillipe and others
PHILLIPE
PIVO
And others

Italy
3TTT
AMBROSIO (3TTT)
CARNIELLI
FB
ITM
And others

UK
GB and others

Japan
ARAI
NITTO
SAKAE RINGYO - SR
Many other brands

velobase link to stems:

VeloBase.com - Component Listing

The point is that most of them have performed satisfactorily over the years.

The problem was that during the US Bike Boom of the early 70s, the demand was so high for "10 Speed Racing Bikes" that European component makers couldn't keep up...

Consequently many poorly cast aluminum stems that should have been thrown back into the melting pot ended up on new bikes. From my experience it was these poorly made cast stems from the early 70s that where the one that most frequently failed.

Unfortunately Sheldon Brown RIP, chose the cast AVA stems to tar with the "Tige de la mort" death stem label. AVA stems were far from the worst offenders. In my experience, I found that the French made Pivo cast aluminum stems were poorest made...

Here's a BAD example of a Pivo stem that should have never made it out of the foundry:



The casting shrinkage defects in the quill were probably caused by the casting cooling too quickly leaving voids in the surface. The quill should have measured 21.9mm (22mm nominal size). In places this stem measures ~21mm! It was only 21.9mm at the bottom!

Something else that happens, when the temperature of the molten aluminum is not hot enough it results in large size grains or crystals forming when the casting cools. These large crystals are not as strong as finer grain size crystals and crack more easily along the crystal planes. One advantage of forging is that crystal grains sizes are much smaller resulting in denser, stronger products.

Fine grains on right - coarse grains on left.



This early 70s Milremo stem made by Belleri shows the coarse grain structure where the stem broke off (while I was riding):



I wrote this post back in 2008 (see Verktyg messages):

gitaneusa.com :: View topic - death stem?

A recent BF post:

http://www.bikeforums.net/classic-vi...l#post17767500

Columbo moment:

One other thing... (or more)

Most of the poor quality stems were sand cast (vs. die cast). The sand cores could shift while the molten aluminum was being poured resulting in voids and thin casting walls in places which weakened the stems. Also the wall thicknesses of the quills were too thin to begin with.

The most common area where these stems failed was at top of the expander split or splits at the insertion end of the quills. The sharp corners of the splits created "stress risers" which generated cracks.

An easy solution the lessen the possibility of crack generation is to drill or file a round hole at the top of the split. A Dremel tool with a small burr works great. You can use this trick on any stem.



Another failure point is the bar clamping area. Using a bar that too small of a diameter is the most frequent cause. Unlike steel, the bar clamp on an aluminum stem can only be compressed a small amount. Cast aluminum stems can be even less compressible.

Don't try this at home kids!

Here's a Cinelli stem for a 26.4mm bar that I used with a 25mm French bar for years. I put this combo together back about 1975 before "we" knew better. A few years ago I wanted to switch to a wider bar. When I tried to spread the bars clamp the front end popped off with a musical ping sound!



Notice the fine grain structure in this Cinelli forging.

Here's a 3TTT stem someone gave me. When I went to use it I discovered the cracks from being used with an undersized bars - should be 26mm don't use with a 25.4mm or 25mm bar!!!



It could also be the result of a flaw in the metal...

The forged Cinelli and 3TTT stems were top quality - much stronger than most cast aluminum stems!

So, it never hurts to inspect your bars and stem periodically. Any squeaking, creaking or loose feel should be carefully inspected!

verktyg

Chas.