This week I made the dual injectors, the one cylinder auger motor and the cab & roof
Sometimes Dennis CNC mills the cab front but this one is fairly simple so I decided to do it myself.
The thing about cutting the windows out on the mill is that they come out to scale and in the right place.
The front windows are not rectangular so the inside cut needs to be done at an angle which I cant to on the mill.
I can however do all of the other cuts.
On the cad program, I draw out the cutout and then plot the coordinates for milling. I am using a 1/16" endmill so I need to offset the readings by .0325" (1/32)
Then on the mill I cut out the outline
I then cut the angled line with a jeweler's saw
And clean things up with a needle file
I then cut out the scribed lines with the 1/8" band saw blade and clean up with the drum and belt sanders.
I cut out the sides on the mill with a 1/8" end mill. Everything is pretty straight forward but this is the first time I am making the window frames on the mill. I start with a CAD drawing.
I had some questions about soldering so I took some photos of the cab soldering. The horseshoe clips hold the sides together while the music wire pins keep it square .
Here is a shot of the injector and auger motor. The lever is for the axle pump bypass.
Ok, I'm back online
This transition piece connects the top of the coal load with the doors in the front
The next piece is tricky as the shape changes as it is bent down. I first cut it from card stock and the glued it on to a brass sheet as shown below. it came out close but not good enough to solder. So I added some masking tape to fill the gaps and used it for the second try.
It is then soldered on. As you can see there are only a few small gaps which will be filled with JB Weld
Then the vertical pieces are cut to shape and soldered on and the two curved pieces are cut after getting the correct shape by trimming card stock to fit.
I lay the doghouse out in CAD. The wood slats need to be carved with a V end mill and I will be using the cad drawing for the measurements.
After the sides are cut, I cut a bottom to the inside dimensions. This helps to keep it square and from falling apart like a house of cards during the solder process. I have four small snippets of 1/32" staybrite on the bottom and four with hooks bent hanging from the corners.
I heat the corners from the outside starting at he bottom and move up till the solder flows. the bottom snippets will melt on their own.
This trick I learned from the HO model It is an easy to make snap holder for the roof
So here is the finished product. I still have frames for the side windows coming from Dennis
I don't like to have the gas valve sticking out the front of the tender. It is hard to conceal it and usually it is hard to get to.
I like to use a vertical valve and make a round hatch that can be used for the knob.
On this tender, there is not enough room for a standard valve so I make one with all of the piping on the inside.
The trick to making it work is to have the inlet pipe bend up so it is taking gas from the top of the tank
The frame on the prototype was a C channel
I cut out the center on the table saw using my steel cutting blade which has a hacksaw type kerf and makes a flat cut. I can't mill it without removing my vice and clamping it to the bed. if I were to clamp it in the 4" mill vise, the ends would bend down ruining the job.
Dennis cut out the truck frames on the CNC mill and I made the little turnbuckle out of 1/8" hex
The axle boxes are tapered down on the outside. I cut the angle first out of 3/8" square stock and then cut them to length.
I then drill out the axle hole on the four jaw
The prototype is held together with two big bolts on each side. After everything is soldered together, i drill out the holes for this on the mill using the DRO for accurate spacing.
I am just about finished now. I just need to hook up the tubing and the link between the engine and tender.
I decaled everything last week and Dennis milled out the tender steps for me.
They now need to be curved on the outer profile. Because they are so small, I soft solder them to a brass strip.
Then I can cut them on the band saw
And clean them up on the spindle sander
I goofed and painted the frame before I got the steps so cant solder them on so I use a 0-80 socket head screw and JB Weld.
While I have the JB mixed, I will attach the builder plates. But first I need to bend them to the smokebox shape. I select a piece of pipe 1/2" smaller and clamp one end down with a piece of oak and then pull the other side down with another piece of oak, both with small vice grips
I'm limited to 10 photos here so here are a few shots of the decaled engine& tender
The Z is officially finished
I gave it a good steam test this morning and took some photo's and vids.
It was a good day for photographing as it was overcast but fairly bright.
Two photos and two videos
Good build Bill, it looks like that was a very heavy load it was pulling with all those real logs. Just curious, what pressure do you think goes to the low pressure cylinders after being used in the HP ones and does the exhaust blast still have some strength left to it. Judging by the exhaust steam plume it looks like the exhaust still has some oomph.
They say that the pressure going from the HP to the LP is about 1/3
Most of the G scale manufactures set their compound's boilers to pop off at 80 psi. they say that the compounds need more pressure but My engines are very happy at 50 psi. this keeps the boiler temperature a little cooler. This engine is set to pop off at 60 and 65 psi so the pressure under a heavy load would be between 15 and 20 psi but the volume would be much greater because if the expansion. As far as I know compounds never had a draft problem except for the Triplex, but that was because they only drafted half of the steam. The rest went out the rear exhaust on the back of the tender.
As you probably know, my ceramic burners don't need or use a draft.