EMD F7 in SCALE

Where users can chronicle their builds. Start one thread and continue to add on to it.

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Steggy
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EMD F7 in SCALE: More Lighting

Post by Steggy »

EMD F7 in SCALE
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BODY CONSTRUCTION: More Lighting

Some pages back, I briefly mentioned the lower headlight, which I had monkey-rigged from some Mag flashlight parts. It wasn't pretty. I wanted to duplicate the real number 401’s lower headlight, so once again, I grabbed my sketch pad and started scribbling.

401’s lower headlight was actually two sealed beam units mounted side-by-side behind a protective lens. Some careful measuring suggested that two Mag mini flashlights could be made to work, specifically the ones that use a pair of AA batteries. They aren’t ideal, since they operate on 3 volts, which is a bit of a design nuisance. However, they have the right size and most importantly, are readily available with incandescent lamps. I tracked down some on-line; bought four of them, in fact, in case I accidentally boogered one of them during the machining that would be required for my adaptation.

The lower headlight opening in the nose is two inches in diameter, with a lip. It appeared the best way to mount the lights was to make a “pod” that would support the lights and snugly fit into the opening. As luck would have it, I had a slug of 2 inch diameter, 6061 aluminum that could be turned into a pod. All it would take is some milling and hole-boring.

After contemplating my idea and some sketches for a while, I decided I had a usable design and went to work making parts. Below are some pics of the pod after all machining was completed.

headlight_pod01_rs.jpg
headlight_pod02.jpg

Meanwhile, some minor machining turned the Mag minis into headlights.

headlight_assy_lower01_rs.jpg

In the above, the minis have pigtails, which are directly soldered to the center contact in the flashlight's lamp holder. It was necessary to remove the lamp holder assembly prior to machining the body, as well as to attach the pigtail. Mag has a tool that extracts and reinstalls the lamp holder, but it is possible to do it without that tool by using a jeweler’s screwdriver to pry the lamp holder cap off the end of the flashlight’s body. Using that technique also makes it possible to find out how far little parts can go flying—never to be seen again, of course. :shock:

Mag minis don’t have a separate switch like their big brothers, instead relying on a small tab that makes contact with the flashlight’s body to complete the ground path—that tab is also part of the lamp holder. The force that brings the tab into contact comes from the spring at the other end of the flashlight’s body that presses against the end of one of the batteries. Since the batteries aren't there anymore—in fact, most of the flashlight isn’t there anymore, I used a long spring to apply pressure to the contact tab. That spring is retained by the bracket that attaches the assembly to the body.

headlight_assy_lower02_rs.jpg
headlight_assy_lower03_rs.jpg

In the above photos, the headlight assembly is assembled. The ground connection for the assembly is attached to one of the screws securing the mounting bracket to the pod.

headlight_assy_lower04_rs.jpg

In the above, the headlight pod has been mounted into the nose (the upper headlight is to the right). The 10-24 studs that hold it in place actually thread into the nose casting and are further secured with a little bit of epoxy.

See next post for some more lighting pics...
Last edited by Steggy on Mon Feb 28, 2022 8:00 pm, edited 2 times in total.
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Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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Steggy
Posts: 1976
Joined: Tue Jun 28, 2011 9:19 pm
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EMD F7 in SCALE: More Lighting

Post by Steggy »

EMD F7 in SCALE
————————————————
BODY CONSTRUCTION: More Lighting cont'd

Some more lighting pictures.

nose_with_lites02_rs.jpg

Above, doing some testing with most of the shop lights off.

lites_in_the_dark01_rs.jpg

Above, checking out the engine room lighting. Also, the headlights are on—I was checking their alignment The glow through the portholes looks dingy, sort of like the original. :D
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Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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NP317
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Re: EMD F7 in SCALE

Post by NP317 »

Looking good!
RussN
Andrew Pugh
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Re: EMD F7 in SCALE

Post by Andrew Pugh »

Looks fantastic BDD.

It must be nice to see the body in paint now!
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Steggy
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Re: EMD F7 in SCALE

Post by Steggy »

NP317 wrote: Mon Feb 28, 2022 11:34 am Looking good!
RussN
Thanks!

Andrew Pugh wrote: Mon Feb 28, 2022 12:19 pm Looks fantastic BDD.

It must be nice to see the body in paint now!
It is...a bit strange, actually, after all the years of seeing it in primer.
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Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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Harold_V
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Re: EMD F7 in SCALE

Post by Harold_V »

BigDumbDinosaur wrote: Mon Feb 28, 2022 7:34 pm It is...a bit strange, actually, after all the years of seeing it in primer.
Heh! Reminds me of how our house looked after installing the sheetrock. It took us years to build, so we were used to seeing studs. Felt really closed in after it was rocked, but it looks (and feels) perfectly normal now. :wink:

Nice looking engine --- high praise from the guy who likes only steam.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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Steggy
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Re: EMD F7 in SCALE

Post by Steggy »

Harold_V wrote: Mon Feb 28, 2022 7:46 pm
BigDumbDinosaur wrote: Mon Feb 28, 2022 7:34 pm It is...a bit strange, actually, after all the years of seeing it in primer.
Heh! Reminds me of how our house looked after installing the sheetrock. It took us years to build, so we were used to seeing studs. Felt really closed in after it was rocked, but it looks (and feels) perfectly normal now. :wink:

It’s kind of like the guy who goes for many years with a beard and one days puts the razor to it. You don't recognize him for a while. :D

Nice looking engine --- high praise from the guy who likes only steam.

Well, thanks!

When I got into the hobby I did consider building steam. In fact, I wanted to model an NYC Hudson—always thought they were some of the sexiest-looking steam locomotives ever to ride the rails. However, I also had a lot of demands on my time, not the least of which was running my computer services business. Plus I didn’t have any machine tools with which to make parts. Insufficient shop space was another issue.

Ergo there were too many things stacked against building steam. Building an F-unit seemed like a workable plan, and since the F7 is an important part of railroad history, I felt comfortable with my decision.

Maybe I'll build that Hudson in my next life...
———————————————————————————————————————————————————————
Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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Steggy
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Re: EMD F7 in SCALE

Post by Steggy »

EMD F7 in SCALE
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BODY CONSTRUCTION: Wiring & Some More Lighting

Here are a couple of pics of the body electrical work.

nose_wiring01_rs.jpg
nose_wiring02_rs.jpg

Above is the wiring to the headlights, class lights and number boards. I used .062" Molex plugs and receptacles with crimp-on pins to allow things to be disassembled without disturbing the wiring. Adhesive pads tie the harness to the body. Some Jameco tie-down tabs are also used where screws are available to secure them.

no2_end_wiring01_rs.jpg

Above is the number two end wiring. I used pieces of 1/2" diameter stainless tubing I had laying around to make the conduits on the aft bulkhead. Some 1/4" SS tubing brings wiring down to the bottom edge of the body for connection to the step lights. Wiring for engine room lighting is routed through the conduits that pass through the roof arches.

Immediately above the vestibule door porthole is one of the engine room lamps. This is a 14 volt, bayonet-base lamp that is powered from 12 volts. The lower voltage gives the light a yellowish cast like the 74 volt incandescent lamps did in the original's engine room. Also, lamp life is extended at the lower voltage. Similar lamps are used for the ladder lights.

fan_wiring01_rs.jpg

Above are the roof fans and their wiring—the number two end of the body is to the right in the photo. These fans are of a type used in machine tool control cabinets. They are thermostatically-controlled and can tolerate the engine room temperatures.
Last edited by Steggy on Mon Mar 14, 2022 7:51 pm, edited 1 time in total.
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Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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NP317
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Re: EMD F7 in SCALE

Post by NP317 »

Fan-cy work!
RussN
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Steggy
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Re: EMD F7 in SCALE

Post by Steggy »

NP317 wrote: Wed Mar 02, 2022 11:57 am Fan-cy work!
RussN

Thanks!
———————————————————————————————————————————————————————
Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
User avatar
Steggy
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EMD F7 in SCALE

Post by Steggy »

EMD F7 in SCALE
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ELECTRICAL STUFF: Trainlining

Once again, I’ve fallen behind due to medical malarkey. The last time I was in the shop working on the F-unit was June 2022, as my heart was weakening and the cardiologist recommended I keep a low profile until something could be done. After dealing with Medicare bureaucratic BS spread out over some eight months, that “something” finally got done late in the year (2022) and I am finally able to get back to work on locomotive-building.

Now, I wasn’t idle during the down period. Something that I have been working on is the finalized electrical system for the F-unit. Since the engineer’s controls—other than the air brake—are all electrical and prototypical in some ways, that means the control (riding) car needs to be trainlined to the locomotive, just like the original. How to go about doing that was something that I gave quite a bit of thought.

I have this fantasy of eventually building a powered B-unit. Fantasy or not, the trainline circuitry is designed to be MUed and, in fact, is not direction-sensitive. That is, either end of the loco could be coupled to the control car and consist movement will be correct for a given reverser position. So, in theory, I could hook up the A-unit vestibule end first and run the engine “backwards.” However, I don’t foresee any good reason (or bad one, for that matter) to do so, so there is no provision at the cab end to MU to another loco. Should the B-unit get built, it will be MU-able at both ends, so it can be in the consist facing either way.

Twenty-four connections, including DC ground, are required between the control car and the locomotive. One of the matters to be settled was how to make those 24 connections in a reliable fashion. Excepting 12 volt power and ground, all circuits are “pilot” circuits, meaning they operate relay coils, not loads. Hence large-gauge wire and big, clunky connectors aren’t needed. In fact, the pilot relays are all low-current units, with a maximum draw of about 35 milliamps—some are less than half of that. 22 AWG wire is more than sufficient for that sort of load, which makes the cable choice easier.

As I contemplated things, it became clear that 25-conductor communications cable with DB25 cable-end connectors could work in this application. A DB25 plug is retained into its mating receptacle by two thumbscrews, so it isn’t going to vibrate loose while running, yet will be easy to separate when needed. Shielded communications cable in 22 gauge can be gotten fairly cheaply in bulk—the electronics industry uses the stuff in mind-boggling quantities, which is why it’s cheap. So the question was how to arrange the connecting parts in a convenient fashion.

My initial idea was to mount the DB25 receptacle on the loco’s number-two-end body bulkhead, but in an unobtrusive manner. The place where I would have liked to have mounted the receptacle, underneath the anti-climber, didn’t offer sufficient internal clearance for cable routing. So I settled for mounting the receptacle on the draft box below and somewhat offset to the drawbar centerline.

The same bulk cable from which I would make trainline jumpers would also be used to route connections from the trainline receptacle to the locomotive’s “brain box,” which is mounted at the number one end of the unit. The shield would be grounded at one end of the cable to keep noise out of the lines (engine magnetos generate a lot of “hash”).

First I needed a suitable bracket to mount the receptacle:

tl_bracket01.jpg
tl_bracket01.jpg (381.3 KiB) Viewed 1461 times

The above was cut from 16 gauge hot-rolled, P&O steel. I do have a Greenlee DB25 knockout punch that can make the receptacle cutout, but since I needed the part shaped in a way that I can’t readily handle with the tools at my disposal, I had to farm out the job to the laser shop.

When mounted to the bracket, the accessible side of the receptacle looks thusly:

tl_bracket02.jpg
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The next photo illustrates the internal side of the receptacle assembly.

tl_bracket03.jpg
tl_bracket03.jpg (370.35 KiB) Viewed 1461 times

Back in the old days, when I had good closeup vision, I would have just soldered the cable leads directly to the pins of the receptacle. Doing so is somewhat tedious and error-prone, however, and given that I can’t see very well anymore, I decided to make a small adapter board to which both the cable and receptacle would be terminated. Hence the little printed circuit board (PCB) hanging off the receptacle.

Next are photos of the assembly taken following wiring and bench testing. Amazingly, I made no wiring errors on the first go (I often mix up blue and green wires).

tl_connector_assy01.jpg
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tl_connector_assy02.jpg
tl_connector_assy02.jpg (268.01 KiB) Viewed 1461 times

With that done, I welded the bracket to the F-unit’s draft box, followed by cleaning and paint, and mounted the receptacle and cable assembly. See the next post for photos.
Last edited by Steggy on Mon Jan 30, 2023 12:47 am, edited 1 time in total.
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Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
User avatar
Steggy
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Re: EMD F7 in SCALE

Post by Steggy »

EMD F7 in SCALE
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ELECTRICAL STUFF: Trainlining cont’d

Continued from above, here’s the draft box with receptacle assembly mounted on the F-unit:

trainline_recpt01.jpg
trainline_recpt01.jpg (308.43 KiB) Viewed 1461 times

Here are some photos of a cable plugged into the receptacle. The drawbar, as seen in the second photo, is as low relative to the cable as it will ever get, unless the draft box somehow gets mangled in a wreck.

trainline_recpt02.jpg
trainline_recpt02.jpg (335.62 KiB) Viewed 1461 times
trainline_recpt03.jpg
trainline_recpt03.jpg (199.26 KiB) Viewed 1461 times
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Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
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