BJ42 refurbisment

[crushers]

side question:
Dougal,
on the BJ70 i am also working on, the frame has been galv and then painted over.
are you recommending i sand blast the paint back off and leave just the galv? or will the bare galv inside the frame be enough?

 

[Dougal]

side question:
Dougal,
on the BJ70 i am also working on, the frame has been galv and then painted over.
are you recommending i sand blast the paint back off and leave just the galv? or will the bare galv inside the frame be enough?

I wouldn't bother stripping anything galv that had already been painted. It's still going to last a long time.

 

[eleblanc]

We do this all the time on large prefab building. We use Satin coated galvanized steel, then epoxy and polyurethane. <----best system ever.

Crushers; i would not risk incompatible paint. Unless you know what kind of paint was use on the frame i would sandblast it (quick commercial sand blast). Where ever galvanized came off, use some galvacon liquid zinc on area where galvanization came off. I would then 1- cover it with epoxy or spray it with anykind of good frame anti rust.

That is what i'd do

Epoxy is very durable but will loose color, crack and eventually chip if exposed to sun UV. That is why epoxy when expose to sun should always be covered with a other type of paint.

I think that's a common misunderstanding Dougal.

You're thinking as though the whole chassis in immersed in electrolyte. It never will be. Damp or wet patches will always affect only limited areas and for varying durations.

A chassis on a vehicle is not at all like a hull of a ship ... in other words.

Those companies that sell electronic rust prevention systems for motor vehicles take advantage of this common misconception to rip people off.

The electrolytic action is limited to the vicinity of the "damp stone-chip" (or whatever paint damage were talking about).

And the thick zinc coating thats there (from hot-dipping) still represents fabulous protection (at the site of the stone chip) IMO.

 

[Dougal]

We do this all the time on large prefab building. We use Satin coated galvanized steel, then epoxy and polyurethane. <----best system ever.

This was done on the new offices I was working in on the worst location in my country for corrosion and only 100m from the beach. They started rusting through voids/damage in the paint in under 2 years.

These frames were spray-galvanised to start with. If they had been left with the galvanising exposed there would have been some white oxides showing up, but no rust. Instead now 4 years later they have probably had to have touch up work done already.

 

[eleblanc]

Bad paint / not enough paint, maybe?.

5 years ago we did 6 large enclosure, (2x 3mW generator) For a nuclear power plant in Canada, very close (1km) from the sea. And they are holding good.

People often paint without taking into consideration roughness of the surface to be painted. If the surface is rought you need thick mils of paint. Otherwise when coupled with not very good paint quality, it start to rust through, with small dot of rush right through paint.

BUT there aren't any miracle paint system for the sea. The miracle stuff is called Stainless steel.

When you use galvanised, where ever calcium / salt can get under the zinc, yes it does rust faster. And that it is why i personally would never have my frame galvanised in the first place. It is not BAD, but too many corners or areas that can be missed or thin of zinc. Galvanised steel rust from within. When you realise you have rust it is usually pretty bad, liuke in totally rotten. With a painted only frame you at least can maintain with easy touch up where necessary.

In this case, Crushers is dealing with a galvanised frame. I would personnaly sandblast it to clean the paint. Do galvcon touch up, and cover with epoxy. The epoxy is a added layer over the galvanized to make sure there aren't any tiny spot of bare metal where it can rust quickly and from within. Start with a brush to reach all corner, when you are happy with hard to reach area spray a good coat. I always use Sherwin william 846.

This was done on the new offices I was working in on the worst location in my country for corrosion and only 100m from the beach. They started rusting through voids/damage in the paint in under 2 years.

These frames were spray-galvanised to start with. If they had been left with the galvanising exposed there would have been some white oxides showing up, but no rust. Instead now 4 years later they have probably had to have touch up work done already.

 

[Dougal]

Bad paint / not enough paint, maybe?.

No, simply the worst place in the world for corrosion. Temperate climate (10-20C almost always), prevailing winds coming in from the sea combined with 2-3m annual rainfall and constant high humidity.
Even 300 series stainless steel corrodes there.

It's a place where vehicles don't just rust, they disappear. Abandoned cars even 10km inland collapse into a rust coloured heap with only the engine block recognisable.

I'm very happy I don't live there any more. I'm still amazed my vehicles survived.

 

[crushers]

hummm, sounds similar to New Foundland. in 5 years brand new vehicles off the lot are swiss cheese. a 40 might last a year ...

 

[tmarx]

Don't paint galvanised steel. It can't work as anodic protection if the sacrificial surface is covered with paint.

Bit late for me BUT I must add even though I used a special galv etch solution and primer before topcoat, alot of the painted areas are showing age so if you are correct, then I have enough exposed sacrificial surface. The galv itself was very thick - something like 4 x the accepted " market norm " so figers crossed ..



sorry for the highjack of your thread Wayne

 

[crushers]

highjack accepted ... all informative
<grin>
i suspect there might be a few tangents occuring during the thread on this build.

 

[crushers]

reinstalling the center cross member
the frame is out by 3 mm corner to corner
and
6 mm in the center, which according to the book is acceptable
and
amazing for a 33 year old truck with unknown number of previous owners.

picked up some of the PC today ...

 

[crushers]

reinstalling the corner bracing
bolted to the rear and to the sides
then getting an idea of the rear removable hitch ...

i have decided to go with grade 8 bolts where all the old rivits were as well as welding the inner channel to the outer ... "just cause" more than any other reason.

 

[crushers]

working on the fit and clearence ...
the max movement of the rear shackle is a must...

 

[crushers]

the rear hitch almost finished
notice how it covers over the rear joint
the there is a reinforcement on the inside
welded on an angle as per instructions
plated and bolted on the outside
and
once the bottom of the frame strap is welded to the hitch then it is also bolted to both sides of the joint in the rear ...

i feel comfortable that the frame repairs will stand the test of time.

 

[jfrench]

Man you work fast! I got a frame that's going to need this in the future...great reference thread

 

[Henry James the 47th]

Have you come across anyone who re-rivets the frame? Can it be done without having huge industrial equipment?

 

[crushers]

Hydraulic Hot riveting 3/4" (19mm) rivets structural steel - YouTube

 

[crushers]

Jfrench,
two words ...

good help.

 

[lostmarbles]

I'm a bit worried about all the young women appearing in this thread

They're well and truly out of your age group Wayne....

Just sayin....

 

[singletrackjunkie]

looking great Wayne! Thanks for the updates

 

[crushers]

Lostmarbles,
if you had a choice
would you look at an old rusty 40 with saggy springs, dented fenders, well used and tired


or


one that is still has nice firm springs, the curves are still true and can still enjoy a good ride?