[SEL] Cracked Head/Epoxy information

[Jerry Evans]

At 07:00 PM 24/01/2009, you wrote:
>From: "Jim Hardman" <Jim at hardmanfamily.net>
>Subject: Re: [SEL] Cracked Head
>
>Hi all...
>
>I spent my working life in the epoxy business and agree that the 5-minute
>formulations are not the best for water resistance.  The slower setting
>varieties will perform a lot better, especially when driven to a more
>complete cure under heat.  Yes, warming the head at the time of application
>will thin the mix and promote pentration.
>
>I used a 5-minute epoxy to make a repair inside a boat house and a year
>later it had reverted to a cheezy mass, about like chewing gum except easily
>flaked.  Slower varieties will do a lot better inside shower stalls, boat
>houses or engine water jackets.
>
>My father-in-law repaired his broken boat throttle with our 5-minute epoxy
>and it scared the lights out of me when he'd come charging in to the dock at
>a full plane and then haul back on the throttle at the last second.  The
>good Lord was watching over him. Repairing a broken throttle arm with a
>butt-joint repair with 5-minute stuff ain't smart.
>
>If I can offer a suggestion to anyone using epoxies, mix them twice as long
>as you think you have to.  The extra mixing time allows greater association
>between the resin and the curing agent and results in a much stronger cure.
>And avoid adding solvents to either thin the mix or extend potlife.
>Reaction rate doubles with an increase of about 18 degrees fahrenheit (10
>degs. C.) which also benefits the final cure.
>
>Maximum temperature allowed varies with the recipe, but anything over the
>boiling point of water should be suspect.  Use silicones to repair anything
>exposed to higher temperatures.  JB Weld should do fine for a crack in an
>engine head as long as there's enough cast iron to take the stresses of
>compression and ignition.
>
>As for surface prep, grind down into fresh metal and wash down the surfaces
>with  a fast solvent like toluene to get rid of any oil residue.  Avoid
>mineral spirits (paint thinner), it takes too long to evaporate.  Wipe up
>the solvent with a clean rag, that's the only way to reduce oil film.
>Evaporation just leaves the oil behind.
>But I'll bet you already know all this.
>Jim in frozen Vermont

Jim,
         Thanks for the post - very interesting and a few things to remember.

         Now, is there an epoxy that will successfully bond to "brass to 
brass" ? I mean really bond it - not just stick it together.


Keep the revs up (or down)
Jerry Evans
Near Johannesburg in Sunny South Africa.
Etched Brass Engine Plates made to order:
<www.oldengine.org/members/evans/plates/index.htm>