Brother Farrokh – Yes the tank is pressure tested several times thru the build. The tank is filled with 5+ psi of pressure then dipped in a water tank to check for any leaks.
I will indeed post detailed pics of the bottom panels and welds. I am about to finish the work on the bottom of the tank also. Will post the pics once the weather clears up and I can take outdoor pics.
Tank’s progress – Sorry for the pic quality. It has been raining since the last 4 days, so we will have to manage with indoor pics this time.
As you can see, the tank has now been sanded. I handed sanded the tank with a 120-150 grit sandpaper first, then moved to 400 thru 1500. Hand sanding takes a lot more effort than using an orbital sander but it sands the tank in a very even manner. Since it’s a slow & controlled motion, one cannot over-sand a certain area. Like I said before, the further we get closer to finishing the tank, the easier it becomes to damage it, thus, each step needs a lot more patience now.
Once the tank is sanded with a 1500 grit sandpaper, it becomes very smooth and any pitting, scratch or rough spot stands out. Our original welds, where the top panel met the side panels needs to be polished to a mirror shine to further check for any hairline cracks or pitting.
After the polishing I found 3 areas which needed some additional care. To fix a small pitting, say less than 1 mm, at least an inch of area needs to be sanded, cleaned and re welded. One cannot just tack weld the pitting as the filler metal won’t be able to penetrate properly into the pitting. If we increase the voltage of the weld, we risk the metal spreading out & deforming unevenly with the heat. That’s the last thing we would want as it would take hours to fix such an issue. Again, at this stage, one needs extra care for the tank.
Polishing is done over my 2HP 2800 rpm (adjustable) motor. In the pics I have marked the various buffing & polishing wheels I use, along with the polishing compounds/bars.
Jute wheel – very hard & coarse. Something like a 1500-1800 sand paper. Used with the rough Brown compound.
Tight Cotton – As seen in the pic, it has multiple stitching rounds holding it together very tightly. The wheel is hard but not as rough as the jute. Used with Brown or white compound.
Loose denim – As the name suggests, denim loosely stitched. It is used to get into tight spots – around the filler cap, indents, etc. Used with fine Green compound.
Loose Cotton – fine & soft, used with Green compound. By now the tank gets really shiny.
Fine Cotton – Just cotton fabric, no stitching. Very loose & soft. For enhancing the shine only. This wheel cannot cut into or sand the metal. It just polishes it.
While polishing the tank gets really hot and very prone to ‘sag’, I fill the tank with water when I polish it. Makes it heavy thou, but keeps it cooler. ONCE AGAIN, one has to be very careful while polishing; the slightest of extra force over the tank towards the buffing wheel can make the tank Sag. Always keep the tank moving and not let one area heat up too much and deform.
Now the tank’s shell is all set. I have already worked on the bottom panels & under tunnel. Will upload the pics once the weather clears up.
We are not that Far from the final finished tank now.
Regards
Singh
http://www.singh-precisions.com
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