On Wed, 21 Mar 2018 21:20:19 -0400, Frank Krygowski
wrote:

That probably sounds terribly risky to some people, as in "But what if
the lever breaks at the repair???"

I'm sure the TIG welding will hold together if there's sufficient
penetration. The epoxy glue job is a bit risky depending on
temperature. The difference between the coefficients of thermal
expansion for aluminum at 23 PPM/C and epoxy[1] at 95 PPM/C could
easily tear apart the glue joint when hot or cold.

Looks like Masterbond has several low CTE range epoxies:
https://www.masterbond.com/properties/epoxies-low-coefficient-thermal-expansion
which are a bit too low but should work. If that's too much work,
just mix in some powdered aluminum into the epoxy mix, and it should
bring the CTE of the epoxy down a little. If that's still to much
work, use the largest diameter roll pin as possible.

But in any normal use, the force on a brake lever is quite small. A
strong person can bend many designs fairly easily. I did that on the
levers on my wife's touring bike, to better fit her smaller grip. They
don't have to be super-strong because you'd go over the bars if you
squeezed too hard.

Agreed. I don't think grip force is going to bend or break the levers
(under normal use). More likely, impact damage from dropping the
bicycle on the brake levers will break the joint. Epoxy is rather
brittle and will crack before it bends. If that's a problem, a thin
strip of aluminum, glued over the joint, should help protect the glue
joint.

[1] MG Chem 9200 structural epoxy adhesive:
https://www.mouser.com/ds/2/265/tds-9200-2parts-1149953.pdf


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Jeff Liebermann
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Santa Cruz CA 95060 http://802.11junk.com
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