Contractor Box

One of the early task in this build was the contractor box. I already had a preconceived image of what it was to look like from building 3 contractor boxes for my 1/4 scale CASE. So I thought this would be an easy task. When I really got into the drawings, what I was seeing was not anything like I had built before. The ¼ scale version had left out the step area for the differential gearing. So a new vision had to be developed. So I made some drawings that I could cipher and translate to flat sheet metal. I did take some liberties with the sizing. I made the overall length a little longer and I put more space between the rear wheel and the fuel bunker area. I wanted more water and fuel capacity and I wanted the extra space between the wheels and the box in case I wanted to put rubber to the rear wheels.

 

The entire box was made of 1/16” thick 304 stainless steel. I did not want to go through what I did with the ¼ scale CASE. They were made of steel and the first one did last me about 6 years. The second one only lasted two years before it started to leak. I had coated the inside with primer paint that never fully dried out spite my best efforts. Then the water got between the paint and the metal and sat there and rotted its way through the bottom of the box. I had pinholes by the dozens. Thus, I chose stainless steel for this build. I welded all the seams via the TIG (tungsten inert gas) method. TIG welding has a tungsten electrode that generates a plasma arc in an inert gas (argon) atmosphere at the weld area. A foot pedal controls the current going to the torch head thus controlling the size of the plasma arc. This way you can control the heat going into the weld joint. If you have a tight joint between two pieces and apply the plasma arc the metal melts and flows together very nicely without the aid of a filler rod. It makes for a beautiful joint. If you need additional metal to make the joint stronger, then filler rod may be added at the time of welding. I tell folks who watch the process that it is almost like soldering. I consider rivets to be an important part of a steam engine model. So I did incorporate rivets in the appropriate areas of my contractor box. I must say my finally way of securing the rivets in place is not what I had planned. I tried welding the rivets from the backside before assembly as I had done on my ¼ scale boxes. All that did was to warp the stainless steel panels way beyond use. I tried soldering from the outside with a small torch and a huge electric soldering iron, same results, the heat would warp the panels. So dad suggested using “superglue”. You know what, it worked very well. I put the superglue around the hole and lightly pushed the rivet in place so I would not push all the glue out of the joint. I gently wiped off the excess and after allowing sufficient time for the glue to cure, it took a hammer to pop the rivets out of their holes. The rest is history. I found some ½ round stainless bar stock that I formed and welded to the top edge of the box to stiffen up the sides and eliminate the sharp raw edge. I washed the entire box down with Dupont “Prep-Sol” to clean and degrease before painting. I used Ace Hardware house brand (Krylon) primer spray paint. I waited a good week before I painted the box a satin black. I did secure a great set of decals from “Gray Barn Machine”. The link is in a previous post. The decals and pin striping will be applied when the tractor is all completed and running. The final touch so to speak.