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Projects ... A3 Switcher    Tender Frame   12/27/2006

This page covers the machining of the Tender Frame ... Section 4.0 - 4.9 pages 22-28


The Tender Frame includes not only frame for the tender but also a few attachments ... Draw Bar and Pocket; Front Step and Brackets; Rear Coupler Pocket; Foot Board and two sizes of pins. I silver soldered thicker material this time ... that gave me a few problems ... get to that later. Additionally did a couple of new things ... drilling/tapping holes for flat head screws and cutting thin grooves for the e-clips. The material used is 360 Brass stock and 260 Brass sheet material (0.04", 1/16" and 3/32"); brass screws except for the flat head screws which are Stainless Steel. The pins were also made from Stainless Steel (I think) rods. I think because I took the rods from a old copy machine.

I don't show all the operations as some of them have been shown before or are very basic.

Each picture below is a thumbnail so it can be enlarged to get a better view ... back arrow to return.
          

After cutting the brass to approximate lengths using the band saw, I used the lathe to square and face one end, the other end was then blued and scribed to the length needed. Then faced to the scribed line, removed, measured for length, repeat until each were within 0.001" of each other. The shorter sills and bolsters were easy. The side sills (15 1/8 " long) needed a little booster to get the correct length (see picture at left). The actual lengths are not as important as being the same length. The end result is that the frame needs to be square.

As can be seen from the pictures I red marked all the parts ... I didn't want to drill holes in the wrong place.
I blued and scribed where the flat head screws would be placed, then used that as a fixture to locate the hole for the threads. These two holes must be very accurately placed, the drill point will serve as scribe point and a small center hole.

Each sill corner and bolster corner was done in the same manner. This assured that all fasteners would be located in the exact location needed.
The basic frame was very flat and all corners square.

Nice job ...
  Shown above is a sample where I scribed the location for the thru hole for the flat head screw. Ignore the two big red dots as they were only there to help note the approximate hole location. Even though I have a DRO, I still do a layout ... it helps prevent mistakes. If the layout is wrong the DRO distance will not line up ... if a move in the x or y direction is wrong the layout won't match. In any event if they don't agree I stop and find out the error ... before cutting!!

To get the correct diameter of the hole (0.210") I set up the 82 Spot Drill just touching the surface then drill down 0.121". The flat head screw is then recessed a little.
 
Drilling the holes for the end is somewhat easy ... just be sure they are vertical. Here I am using a Brown and Sharpe square.   The side sills require a little more work. Had to move the mill/drill head over and use a V block. Also made sure the sill was vertical.
 
Here is how I made the slots for the Rear Coupler (and Foot Step). After cutting the 260 Brass on the Band saw I milled them down to size. Sanded the edges to get a smooth surface. Super Glued them together, so that I could put them in the vice as one piece. That way they all came out the same. The DRO would give me the depth and the Dial Indicator the distance between each slot. I am using a .040 Slitting saw, which was perfect for that size. When cutting for the .093 width ... just move it down and make a new cut. Worked great.   This is the rear coupler after silver soldering, trimming to size and drilling mounting holes. Behind the back plate there is another side plate the hold the coupler to the fixture. To get the 3/4" radius, some would use a 4 jaw chuck. I used my 3 jaw and a 1.5" round stock aluminum fixture ... that worked too.
 
I always make a CAD drawing of the work I am about to do. In this case I was able to use the printout as a fixture to get the correct side slope of the Foot Step (see above ... before trimming).

To cut out the curve, (see photo copy above) I used a copier to enlarge the side view by 205%. Then pasted it on the Foot Step side, now I have a guide so that the curves would be the same or at least very close.

Silver soldering ... a near disaster. My Propane/Oxygen torch flame was just too small to heat up the 2" x 2" x 1/16" back plate. Ended up using 2 tanks of Oxygen (at $9 each) and still not getting good wetting. In fact it took three tries to get the first one done. The second never did ... changed to two Mapp tanks heating the assembly at the same time ... that worked!

I will be changing to using a Turbo Torch for my future silver soldering.
  Now that the Foot Step is trimmed to size it needs to be mounted on a bracket ... since we are using flat head screws the alignment needs to very close. So I Super Glued the bracket to the Foot Step ... placed in vise and drilled through the back plate and bracket with a #43 bit (0.089"). Then drilled the 82 counter sink hole to a diameter of .190" and we are done ... perfect alignment! Remove bracket and tap for a 2-56 screw.
 
Now that the bracket and Foot Step are in alignment, the bracket needs to be mounted on the Front Bolster. Did the same thing as before ... Super Glued the Foot Step to the Bracket and the Front Bolster. Used the surface plate and a square for alignment. Removed the Foot Step, placed in vice ready to drill.
  Well ... here are all the pieces that make up the Tender Frame.
Doesn't look like much, but a lot of detailed work went into making these parts.
The rest of the pictures show varies views of the completed assembly.
 
Moving on to the Tender Tank!
     
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