Nice error recovery on the 1/16" dimension, and the soldered assembly looks great.

I was going to say "bueno notches" as a greeting , and in reference to your milling cuts, but I don't trust my Spanish skills! 

I'd think PET would hold up better to abrasives, but either material should take the forces (weight of payload plus the overburden during scooping) at that scale (I'm imagining a pile of wet sand to work on, not the wife's cache of raw diamonds and assorted carbide tooling shards).

 

Thats the way I  was thinking too. No diamond digging, though the elves may use it on thier swarf pile, to get more in the truck to sell for beer money!        




Fun and easy to find  materials to learn digging in will include sand, small gravel (fish tank? Chick grit?) Or even fresh clean kitty litter. I  have some bags of chick grit left over from train layout making. For those who never got near a farm, chick grit is a clean fine gravel used to give baby chickens something to swallow for thier gullet digestive  system. Same reason you see sparrows pecking at and swallowing small stone bits around driveways. Perfect size for G1 rail ballast.




After the suggestion the other day about that circuit board place that also does metal printing and cnc, I did more digging, pun intended, into similar  places. After lots of looking around and getting quotes, plus seeing what it would take to fabricate  those parts myself, I  wound up ordering a bucket and door 3d printed in steel by a laser melting process, like the way plastic powder printers work. Cost seemed high at first, but it would have taken me a lot of material and time to make myself. These parts are large, about 4x3x3 inches, with 1/8 to 3/16" thick walls, so the total print time on the SLM printers totals 120 hours!! The final parts should be very strong given the thickness of steel, plus the weight is  needed to counterbalance the dipper stick and cables. CNC milling was another option, but the internal gaps between the teeth and ribs down inside the bucket makes that complex to machine, driving up costs.




So, this will be an interesting  test, and will let me concentrate on  my normal engine builds while getting a fun excavator  to play with. Stay tuned!

There are some little notches in the sides of the cab front that I wanted to cut out now, while things are still square and flat.  Once I solder the windows and doors on the front, it won’t be flat.  So now seemed like the time to do it.

I’ve used some 1/8” plate on either side of the piece to help provide some rigidity to the steel sheet.  Regardless, I took many very light cuts to make this 3/16” wide notch.


Then I made an even tinier 3/32” notch in the middle. This notch is to give some room for the roof pivot pins.  I notched both sides of the cab front like this.


Next, I laid the cab front down and proceeded to center mark out all the holes that needed to be drilled.  To make sure I was putting the solder holder screw holes in the right place, I lined the parts up to the scribed lines on the cab front.  It’s a good thing I did that – the calculated position didn't line up with the hole in the door!  As it turns out, the position I'd calculated for the cab front was right.  However, I’d miscalculated the X coordinate by 1/16” on the doors!  But since the doors were already drilled, I decided to make THEM the right ones and change the position of the holes on the cab front to match.  Good catch, but a dumb mistake. 


Here I’ve gotten all the holes drilled in the cab front.  There are more than it looks like! I also drilled a hole in the center of the boiler opening and for the bump for the throttle neck.  Figured it doesn’t hurt and they should come in handy if I have to reregister the part for other ops later.


Then I tapped the solder screw holes and test fit everything together.  Looks about right!


For soldering, I thought I’d try whetting the backside of the windows and doors.  I’m not sure I did a great job here, but it was as good as I could get. I just couldn't seem to figure out how to get the solder to spread evenly across the surface.


Then I set it all up to solder it together.


It took me a couple of tries, but I think it came out OK.  Guess we’ll see.  It’s not really as satisfying as silver soldering, that’s for sure.


Next, I’ll cut out all four windows, then move on to the boiler cutout and the roof line.

Kim

I'd think PET would hold up better to abrasives, but either material should take the forces (weight of payload plus the overburden during scooping) at that scale (I'm imagining a pile of wet sand to work on, not the wife's cache of raw diamonds and assorted carbide tooling shards).

 

Really great and fascinating project Chris. Your attention to detail is always first class.

Thanks  George! Much appreciated!