Well, i dont have data for the pazzo's yet...
However, i did have a few momments on the hardness tester and a piece of a stock lever laying around from when i broke mine..
SO....
The results on the stock lever... Nothing amazing really, i had assumed it was likely a cast aluminum piece, and the hardness test seems to coincide with that notion...
I had to polish the specimen, and ran about 10 locations to establish a mean...
The median value came out to 100.47 MPa... which is right on the money for a cast aluminum alloy..
Anyhow, i did this only to establish a baseline, and because a handful of people requested i look into the stock lever...
In regards to the lever itself... As i said, its a cast aluminum alloy most likely, and the quality is average, to below average quality...
My piece had a little bit of pourosity in it, which surprised me... Nothing major, but enough that i noticed it while polishing the sample... It could be i just had a bad lever, or perhaps indicative of the cast levers in general..
A sample size of one, indicates very little...
Anyhow, while the pourosity would weaken the specimen SLIGHTLY, it wouldnt be enough that i would yell for people to switch levers... It really just doesnt matter honestly...
Other comments...
The tensile strength of cast aluminum alloys tends to be OK, certainly good enough for a lever.
Correspondingly, its ductility is on the low side which is kinda normal for most cast alloys, though for aluminum they tend to be low...
This is likely very intentional, as levers are designed to fracture first, not bend in a ductile way...
You can see this by noticing that the lever is also notched near the end to facilitate that fracture point.. The notching creates a crack stress point as well as weakens a specific spot so that when it is impacted, it fractures quickly and cleanly...
Looking at Charpy impact test information for cast aluminums also suggests this is designed into the system, as the charpy energy is very low for a metal...
This is actually a perfect example of engineering something for controlled failure...
If you catch your lever on something, its a MUCH better thing for your lever to fail and break leaving you riding down the street, rather than having the lever be so strong it pulls the bike down...
I still need to get SEM testing done to confirm the specific casting alloy being used, however, i just wanted people to know some progress is being made..
Anyhow..... Some pictures.... for those interested...
Here is a fuzzy picture of the sample of the lever in the machine... Hardness testers are basically a fancy microscope, with very acurate indentation probes that press into the material...
Its hard to see, but down and to the right of the flash on the screen, is a "x marks the spot" indentation. Its actually a pyramid.. That is the indentation left by the force probe.. This is at 50X..
This picture is the results i get basically, i manually indicate the outlines of the indentation, and based on the diameter of the indentation, and the force of the probe into the material, a hardness is calculated...
The whole buisness.. Doesnt look very impressive... but its about 40k dollars worth of machine...
However, i did have a few momments on the hardness tester and a piece of a stock lever laying around from when i broke mine..
SO....
The results on the stock lever... Nothing amazing really, i had assumed it was likely a cast aluminum piece, and the hardness test seems to coincide with that notion...
I had to polish the specimen, and ran about 10 locations to establish a mean...
The median value came out to 100.47 MPa... which is right on the money for a cast aluminum alloy..
Anyhow, i did this only to establish a baseline, and because a handful of people requested i look into the stock lever...
In regards to the lever itself... As i said, its a cast aluminum alloy most likely, and the quality is average, to below average quality...
My piece had a little bit of pourosity in it, which surprised me... Nothing major, but enough that i noticed it while polishing the sample... It could be i just had a bad lever, or perhaps indicative of the cast levers in general..
A sample size of one, indicates very little...
Anyhow, while the pourosity would weaken the specimen SLIGHTLY, it wouldnt be enough that i would yell for people to switch levers... It really just doesnt matter honestly...
Other comments...
The tensile strength of cast aluminum alloys tends to be OK, certainly good enough for a lever.
Correspondingly, its ductility is on the low side which is kinda normal for most cast alloys, though for aluminum they tend to be low...
This is likely very intentional, as levers are designed to fracture first, not bend in a ductile way...
You can see this by noticing that the lever is also notched near the end to facilitate that fracture point.. The notching creates a crack stress point as well as weakens a specific spot so that when it is impacted, it fractures quickly and cleanly...
Looking at Charpy impact test information for cast aluminums also suggests this is designed into the system, as the charpy energy is very low for a metal...
This is actually a perfect example of engineering something for controlled failure...
If you catch your lever on something, its a MUCH better thing for your lever to fail and break leaving you riding down the street, rather than having the lever be so strong it pulls the bike down...
I still need to get SEM testing done to confirm the specific casting alloy being used, however, i just wanted people to know some progress is being made..
Anyhow..... Some pictures.... for those interested...
Here is a fuzzy picture of the sample of the lever in the machine... Hardness testers are basically a fancy microscope, with very acurate indentation probes that press into the material...
Its hard to see, but down and to the right of the flash on the screen, is a "x marks the spot" indentation. Its actually a pyramid.. That is the indentation left by the force probe.. This is at 50X..
This picture is the results i get basically, i manually indicate the outlines of the indentation, and based on the diameter of the indentation, and the force of the probe into the material, a hardness is calculated...
The whole buisness.. Doesnt look very impressive... but its about 40k dollars worth of machine...
