Friday, August 28, 2015

Anna Needs Help. Bad.

My poor trailer is neglected. Things have been breaking and I throw a bandage on it and keep rolling. Unfortunately some thing has come up that needs attention straight away.
We went to the beach a few weeks back. On the third morning I was enjoying a book and my morning coffee. The strong and distinct smell of black tank kept hitting my nose. I went to investigate and from the valve there was a steady drip, drip, drip,  about as fast as you are reading that. The site was all sand and it was absorbing the dripping black tank juice. I immediately went to into action. I emptied the tank into the sewer dump, taped off the toilet, and bee lined it for the store to buy baking soda. The place we were camping would not be happy if they found out what had transpired. 

When we got home I knew I needed to get to them bottom of the problem. It was not pleasant to say the least. This issue has gone on for a long time.

Around 2008 a good friend machined this plate for me. We used some internet instructions developed by a guy many refer to as Mr Airstream. The plate is used to convert the old valve bolt pattern on the bottom of the black tank to a more modern valve system. Many vintage Airstreamers have made one of these plates to make this conversion. They all follow the internet instructions that tell you to use a 6x6 chunk of 1/2" aluminum.

As far as fabricating this is a great material. There is one major issue; aluminum and acids are mortal enemies. Aluminum always losses. The uric acid in the black tank juice just ate it's way out. A new solution was hatched.

The metal part in the bottom of the tank is bronze.  For 53 plus years it has worked perfectly. I will just fabricate a new plate out of bronze. 6"x6"x1/2"... please do not ask me the cost. I very carefully laid the pattern out on the new plate. The holes have zero margine of error. Measure twice, cut once not cut twice and it is still wrong. The spot for each hole was punched to give a starting point for the drill bit.

The bolt holes were drilled with a #7 bit. This is what a 1/4-20 tap requires. You do not see it but the plate is firmly clamped down. If you do not clamp it down, the very soft bronze will grab onto your bit and it will be spinning. Bronze is very hefty and the chunk will easily cut you or mangle your hand severely. 

The center hole was drilled out next.

The bolt holes that go into the bottom of the tank need to be counter sunk. It is important the heads of the those machine screws are flush with the face of the plate. 

All the bolt holes were next tapped for threads.

And there you have it, an exact copy...