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From: TOG on 11 Nov 2009 08:58
On 11 Nov, 11:29, Bob Scott <B...(a)bobandaileen.co.uk> wrote:
> Come to think of it, I've unscrewed the tank badges but they are still
> stuck fast to the tank. I suspect there isn't much structural integrity
> under the badges.
>
Notorious weak spot on a lot of tanks, that. Water trickles down
behind the badges and gets trapped. The Kawa GT550/750 fours suffered
from it. I used to take the badges off mine every year ot two, and
dollop a load of grease beind them. Never had a problem.
From: TOG on 11 Nov 2009 11:28
On 11 Nov, 14:29, Bob Scott <B...(a)bobandaileen.co.uk> wrote:
> Bob Scott <B...(a)bobandaileen.co.uk> writes
>
> >TOG(a)Toil <totallydeadmail...(a)yahoo.co.uk> writes
> >>On 11 Nov, 10:09, Bob Scott <B...(a)bobandaileen.co.uk> wrote:
>
> >>> In fairness to the lining, it did last more than 10 years and, having
> >>> removed the tank from the bike, I reckon the tank would have been
> >>> unusable years ago as the underside of it was unbelievably rusty. When
> >>> the current tank starts to look rusty inside I'll get it lined as well
> >>> and that should see out the rest of the bike.
>
> >>I suppose 10 years is pretty good going.
>
> >Oh yeah - I was annoyed when I saw the flaking then had to think about
> >when the lining had been applied...
>
> Bad form and all that, but something occurred to me just now - I think
> this was the first time we had put the bike away with an empty tank.
> Wonder if sitting with a tank full of petrol might have prevented the
> peeling?

No idea. Ask a materials specialist?
From: Shantideva Upasaka on 11 Nov 2009 12:34
On Nov 11, 6:29 am, Bob Scott <B...(a)bobandaileen.co.uk> wrote:

> Bad form and all that, but something occurred to me just now - I think
> this was the first time we had put the bike away with an empty tank.
> Wonder if sitting with a tank full of petrol might have prevented the
> peeling?

Maybe. You have to consider the effects of long term exposure to
alcohol upon epoxy.

You can build an airframe from fiberglass or carbon fiber, but if you
want to
carry gasoline inside an integral composite tank in the wing or
fuselage, you have to use epoxy to bond the fibers together, because
alcohol will gradually eat up the traditional polyester resin that's
been used since the 1930's.

Volatile alcohol additives are the first fraction to self-distill out
of stored gasoline.

But, if the tank is empty, rust will start finding its way through the
epoxy tank liner.

Did you know that the pressure vessel of the Apollo command module was
all
epoxied together to make a very strong, lightweight structure?

We had to go to extreme degreasing of the surfaces and then abrading
them with Scotch Brite abrasive pads to get the epoxies to stick to
the parts that we were bonding together.

We had to prepare a test specimen with every joint we bonded together
and it was pulled apart on a tensile strength tested to prove its
strength.

Of course you cannot get inside of a motorcycle gas tank to abrade it
evenly, unless you want to sandblast it inside.

So the Kreem kit gives you some acid to etch the inside of the tank,
and how long you allow the acid to work and how you neutralize the
acid and dry the tank out will determine how much oxidization starts
on the inner surfaces before you get around to pouring the liquid
epoxy into the tank...


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