|
In a message dated 1/10/2007 2:07:44 AM Central Standard Time, brenthartwig@hotmail.com writes:
Thanks much Dean
I forgot about the etching step. I've been looking at Rhino liner type coatings for many areas of my sub. One brand called Rattle Guard is claiming you can apply it directly to clean bare metal with out any primer since it is self etching and water proof. This type or coating is an elastic material, it can expand and contract with the metal surfaces. Of course rubber can burn and cause you trouble if a fire gets on it. With Rattle Guard you can leave the rubber out of the mix.
I do not know anything of the new rust proofers. What I can say with confidence, the origingal
coatings (30yrs ago) did more harm then good. They lost a little adhesion and created a air
pocket witch rusted the metal as fast as a drill. The new ones I have heard are better but
I do know the surfaces have to be really clean. For example you buy a new car and want it
rust proofed you had better do it before it sees the road.
http://www.rattleguard.com/faqs.htm
For bolts and the like, I like the idea of using nylon washers. You could also use nylon washers backed up with stainless steal washers for strength with allot of none moving connections which help avoid chipping the paint there as well. I also like the idea of using the bluing agent. If you make bolt hole over sized you can use a nylon collar to take up the extra space for connections with more stress and vibrations then most.
One thing I have experimented with is threads coated with JB weld epoxy. This seems to
work really well, but forget about ever getting the bolt back out. I have used this rather
then say stich welding.
On the hyperbaric chambers I worked on we used internally threaded stainless steal couplers for all are through hulls and welded them with stainless steel MIG wire. This was mainly done since treads if not made of stainless will rust badly.
I've seen a fair number of the large springs that are used to make hatches easier to lift and close, and they all look like a rust nightmare. Is there a stainless steal alternative? Some stainless steal will rust in saltwater so I would be interested in knowing which type(s) are best in saltwater? What about the non-magnetic types of stainless steal? I've heard electrolysis will eat away stainless steal at a pretty quick rate if you don't coat it properly with a good epoxy paint or the like and/or use the zinc plates.
If the stainless is magnetic throw it away. I have been very disappointed in the quallity of
these type of fasteners
I was thinking about the stitch welding mentioned earlier and as I understand it you'll get less heat warping on your weldments if you do that. You would have allot of exposed tight voids were rust loves to work unless you can seal it with a bed liner flexible coating or the like. I've never seen a spot welded support ring with spaces left between the welds on a submarine, so there must be a reason or I might need to get out more. How ever it maybe a good idea to stitch weld your rings onto the outer hull and continue to stitch weld until there are no spaces. This would limit your warping. That's the way I weld thin metal together on car bodies and control the heat.
I am not a welder by trade, but I don't think your method is a real good idea. every time you
start and stop a weld you have a potential problem with pockets. I to have done much welding
of tin. My most successfull methods was to stitch weld using wet rag as heat sink and finish
the gaps with brazing rod to seal the gaps. The body shops today don't even weld the replacement
panels on. They actually glue them on no welding. I need to check into this method. There is also
another very old method from auto body days. Leading. I have not tried it for this particular
applications but I do no very low heat and excellant sealage and adhesion.
I don't see to many PSUBers heat treating to stress re leave their weldments for what ever reason. Likely because of cost and availability of local companies able to do the service. Karl Stanley did heat treat his deep diving sub Idabel a couple of different times while he was building it. It seems that heat treating is not always necessary but would give you just that much more strength and/or areas that are so hard they would brake rather then flex.
The experts out here should understand this area. But I am sure a lot of it depends
on the carbon content of the steel. Many years ago when I was building Drag Racing
dragsters I did a little of stress relieving on small parts. I can not imagine doing say
an entire pressure hull unless you are the goverrnent.
Brent and all I am as ignorant as a rock on subs and problems so if anything here
is not correct pleasssssssssse set me straight. I am basically a jack of all trades
and master of none. Well none that relate to building subs.
Dean
Brent Hartwig
|