EMD F7 in SCALE

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Jerry_H
Posts: 216
Joined: Tue Feb 03, 2009 9:39 pm
Location: Central FL

Re: EMD F7 in SCALE

Post by Jerry_H » Wed Mar 21, 2018 7:14 pm

Here's hoping that you get back in the cab soon.

Jerry
www.chaski.com

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BigDumbDinosaur
Posts: 680
Joined: Tue Jun 28, 2011 9:19 pm
Location: Midwestern United States

Re: EMD F7 in SCALE

Post by BigDumbDinosaur » Wed Aug 15, 2018 9:35 pm

Jerry_H wrote:
Wed Mar 21, 2018 7:14 pm
Here's hoping that you get back in the cab soon.
Thanks!

Although not fully recovered from all the health sturm und drang, I am back in the cab, metaphorically speaking, and will be updating this build log some more.
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Science makes it known. Engineering makes it work.

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BigDumbDinosaur
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EMD F7 in SCALE

Post by BigDumbDinosaur » Wed Aug 15, 2018 11:30 pm

EMD F7 in SCALE
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BODY CONSTRUCTION: Part VI

With the body structural work completed, the next step was to start detailing. Some of the details are fairly easy to handle: grab irons, for example. I used several different sizes of Precision Steel Car (PSC) grab irons, which are secured to the body with 4-40 stainless steel, hex head screws. 4-40 is a bit too large for 1.6 inch scale, but using that size screw made things a lot easier for me. I daresay that once the unit is in paint the slightly-too-big screw heads will be quite unobtrusive. :D

firemans_side03.jpg
Grab Iron Details, Fireman's Side

I made the long irons straddling the cab door by cutting short PSC grab irons in half and joining the pieces with a piece of 3/16" x .032" hard-drawn brass tubing. As the ID of the tubing is slightly too small to accommodate the diameter of the grab irons, I ran a number 30 drill into each end of the tube, which made for a close fit. A drop of cyanoacrylate adhesive at each end keeps the parts together.

Another interesting bit of detailing is in the portholes, of which there are four engine room ones, plus one in the number 2 end vestibule door. The vestibule door porthole glazing was relatively straightforward to make, involving some turning of a piece of cast acrylic rod and drilling some mounting holes. The outer face, which is visible in the below photo, was polished with automotive rubbing compound to give it a glassy appearance. The inner face was roughed up with 60 grit abrasive to make it translucent.

porthole_vest_door02_reduced.jpg
No. 2 Vestibule Door Glazing

The above piece will be inserted into the door from the inside and secured with four hex head machine screws that go into tapped holes in the Alumilite. When everything is finished, a small incandescent lamp will be mounted near the porthole to give the illusion of engine room lighting.

The engine room portholes proved to be more of a challenge. On the exterior of the prototype there is a bezel, into which the porthole glazing is secured with rubber molding. I kicked around a number of ideas on how to go about doing this, finally coming up with a two-piece design, consisting of a steel bezel and acrylic glazing.

The bezel is a machined ring that fits into the porthole opening in the body. The inside-facing part of the bezel has a shoulder that pilots into the body opening, whereas the outside-facing part has rounded edges that approximate the appearance of the full-sized part. Below is an illustration of how the porthole assembly goes together:

porthole_worksheet.jpg
Engine Room Porthole Design

The glazing pilots into the bezel's ID, and will be secured to the body with epoxy.

The below photos are of one of the bezels:

porthole_bezel_inside01.jpg
Engine Room Porthole Bezel (inside surface)
porthole_bezel_outside.jpg
Engine Room Porthole Bezel (outside surface)

Conveniently, the inside and outside diameters of 2-1/2 inch, schedule 80 pipe are almost exactly what is needed—only a small amount of turning was required to achieve the right dimensions. I used ASTM-rated pipe for this part to avoid the scale present on ordinary black pipe—that scale can wreak havoc on lathe cutting tools, as well as result in a rough finish. Visible in the first bezel photo is the shoulder that pilots the piece into the body.

Once the bezel was inserted into the body, I held it in position for welding with a monkey-rigged holding fixture made out of some scraps laying around the shop. Some small and precisely-placed welds secured the bezel's shoulder to the body, and a little cleanup with the angle grinder got everything nice and smooth.

Here's what one of the bezels looked like after installation and priming:

bezel01.jpg
Engine Room Porthole Bezel

I've run out of room in this post for more photos, so I will continue in the next post with more photos of the porthole stuff.
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Science makes it known. Engineering makes it work.

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NP317
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Joined: Tue Jun 24, 2014 2:57 pm
Location: Northern Oregon

Re: EMD F7 in SCALE

Post by NP317 » Thu Aug 16, 2018 10:03 am

Gorgeous!
There aught to be a law...
~RN

rkcarguy
Posts: 908
Joined: Tue Aug 22, 2017 10:33 am
Location: Wa State

Re: EMD F7 in SCALE

Post by rkcarguy » Thu Aug 16, 2018 11:36 am

As always, beautiful work BDD. Glad to see you are back on the build.

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BigDumbDinosaur
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Joined: Tue Jun 28, 2011 9:19 pm
Location: Midwestern United States

Re: EMD F7 in SCALE

Post by BigDumbDinosaur » Thu Aug 16, 2018 9:20 pm

NP317 wrote:
Thu Aug 16, 2018 10:03 am
Gorgeous!
Thanks!
There aught to be a law...
Don't we already have too many of them? :D
rkcarguy wrote:
Thu Aug 16, 2018 11:36 am
As always, beautiful work BDD. Glad to see you are back on the build.
Thanks! As I wrote in my first post when I started this build log, this project has taken far longer than I ever expected. Rickety health can really mess up things. :x
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Science makes it known. Engineering makes it work.

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BigDumbDinosaur
Posts: 680
Joined: Tue Jun 28, 2011 9:19 pm
Location: Midwestern United States

EMD F7 in SCALE

Post by BigDumbDinosaur » Sun Aug 19, 2018 6:34 pm

EMD F7 in SCALE
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BODY CONSTRUCTION: Part VI cont'd

Continuing on the detailing of the engine room portholes, here are some more photos.

bezel_holding_fixture01.jpg
Porthole Bezel Holding Fixture, Inside View

Above is my monkey-engineered bezel holding fixture I used during welding. :D


bezel_holding_fixture03.jpg
Porthole Bezel Holding Fixture, Outside View

Above is what the holding fixture looks like from the outside.


bezel_welded01.jpg
Porthole Bezel After Welding

Above is what the interior looked like after one of the bezels had been welded and cleaned up.


porthole04.jpg
Porthole Outside View
porthole_closeup02.jpg
Porthole Outside View

Above are exterior views of the porthole with the glazing in place.
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Science makes it known. Engineering makes it work.

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