Figure this out, win a prize!

[JayDarden]

I used some two part epoxy putty to repair a hole in my air cooled motorcycle head. I mixed up more than I needed and put half over the hole. The extra hardened in 1 hr just like the package said, and the stuff on the head was still soft two hours later. Why?

The answer is simple, but it took me a few minutes of "head" scratching.

The winner gets the left over ball of hard putty. Postage not included

[John Rogers]

Most two part epoxies and glues require heat to cure or get hard. I'd say the head sucked the heat away so fast it could never cure without a little extra heat.

[sean_V8_914]

were both parts mixed well?

[JayDarden]

Sean - this is what I feared at first.

John you win a dried up blob of putty!!! The head acts like a big heat sink, the stuff cures faster at higher temps. The head takes away the heat of the reaction, and cures slower.

Oh yea, take your wedding ring off before mixing the stuff - it is a pain to scrape off when it starts to dry.

[John Rogers]

I have some very high epoxy that has to be heated to over 400 degrees before it will cure! What a pain...

[sean_V8_914]

good info for future pain avoidance, thanks

[Special K]

Greater thermal mass in the container. The chemical reaction of combining the resin and hardener creates heat, which in turn cures the epoxy faster, which creates more heat, and so on, kind of a vicious circle....It's the same thing that happens with epoxy or any other two part resin system used in composites (fiberglass, carbon graphite, kevlar, etc).

[Special K]

Okay, I have an unfair advantage....I have to work with the crap every friggin' day in the old airplane factory. We have some bonding adhesive called EA934, basically Mil Spec JB Weld. If you mix a pack and only use a little....DON'T THROW THE REST IN THE TRASH!! Ask me how I know..

As for the 'prize', I will defer...I already have serveral hardened balls of crap on my workbench already.

[helowrench]

special k, I have the same stuff on my desk along with the 1838, 9309,all of the magnobond stuff. at least the sealant can come in handy.where do you work?
rob

[Andrew_J]

Originally posted by Special K
Okay, I have an unfair advantage....I have to work with the crap every friggin' day in the old airplane factory. We have some bonding adhesive called EA934, basically Mil Spec JB Weld. If you mix a pack and only use a little....DON'T THROW THE REST IN THE TRASH!! Ask me how I know..

As for the 'prize', I will defer...I already have serveral hardened balls of crap on my workbench already.

So how many trash can fires did you start before figuring this out...lol

[Special K]

So how many trash can fires did you start before figuring this out...lol

B]Nearly[/B] "one"....and that was WAY back

special k, I have the same stuff on my desk along with the 1838, 9309,all of the magnobond stuff. at least the sealant can come in handy.where do you work?

I'm at Boeing in St. Louis, F-15K (which is an F-15E for Korea) line at the moment.

[helowrench]

I play with helicopters now in the overhaul shop, but worked structures on anything with wings (Cessna 140 to Boeing 767) for a long time. And I started many many fires that way just remember you get smoke for about 30 seconds before the flame.............
Rob

[Special K]

Oh yeah!...and it smells sooo gooood!