How-To guide for building a new dome structure on your passenger car

Thank you for the measurements @Hancock52.  I'm finally making progress on this project and they will be used to build this new ACF dome correctly.

Update 3.  

Trimming the brass window assembly to fit an 18" semi-scale K-Line aluminum shell.  The first thing I noticed was the brass casting is taller than required and it has a significant forward curve on its front side at the roof line.

At this point, I carefully sanded and filed down the front curve of that 30+ year old brass window assembly.  In photo below it shows the roof line curve of these old lost wax brass castings now match the curvature of the K-Line roof line perfectly.  👍

Stay tuned for the next step…

Update 4.

I needed to make this new ACF dome structure proportional to my semi-scale aluminum shell while at the same time filling up the 6.5” opening.   I couldn’t put the brass windows all the way to the front or rear openings because then the new dome structure would be way too long for the 18” shell.   

Small patches had to be created to fill in the extra roof space.  To fill in the opening I liberated a few aluminum roof sections from a 15” K-Line donor car that had the same roof curvature.  The plan is to place a smaller roof patch in front of the forward brass window assembly.  This will move it slightly forward when compared to the Budd dome to better match the Union Pacific plans.  I will put a normal size patch at the rear brass window assembly.  This will keep the rear at the same location as the original Budd dome so it will look proportionally correct.  So far everything is coming together.

Stay tuned for the next step…

Love it! JohnA

Update Nov 27^th

The flat center roof section with side windows was difficult.  I called a large train store that specialized in O-Scale brass to purchase the center roof section with 12 matching windows.  The store said “That center roof section with windows is a single sheet of brass that’s included with the brass model kit.  It’s not sold separately”.  Umm… that puts a major setback on my plan.

Scrambling for a plan B.  I drove to a local hobby store and purchased a 0.06” thick brass sheet for the center roof materiel and flat brass strips for dome sides and window frames.  When I got home I worked on removing the extra knob off the top of the brass casting and then after hours of carefully studying all the parts.   I realized I was in over my head and gave up.

There was no way I could figure out how to create 12 identical windows out of brass, with zero experience in this type material and my limited hand tools.  And even if I could make perfect window openings how was I ever going to get the exact curvature of the domes outer window frames.  After several failed attempts I gave up on making a homemade center dome section and contacted a professional with a CNC machine.

He calculated the window openings with a micrometer, identified the window corner radius and then created a CAD drawing on his PC.  Then, he secured a sheet of 0.06” thick aluminum in the CNC machine, calculate the RPM needed based on the type of aluminum being cut and the size of the end mill (router cutting bit) being used.  After inputting the data the automated CNC machine came to life and went to work cutting in 12 identical windows out the flat stock.  As you can see below a complete center window section was created that’s the same exact thickness as the brass window assembly.  The CNC machine even included the 0.01” thick frames around the windows.

Next we had to find a way to bend and form the sides of this new aluminum window assembly to match the brass window castings.  For this, the CNC shop measured the internal radius of the brass casting.

He inputted the new data into the CNC machine and it went to work creating a solid aluminum mold that I could form the aluminum window sheet over. Send me an email if you want the contact information for this CNC shop.

Next, we centered the new 0.06” thick window section onto the mold and started forming it around and into the correct curved shape that would match the exact radius of the brass window castings.

Stay tuned for the next step…

Wow! Looking forward to seeing the completion.

Update, Nov 28th

After yesterdays project update I believe I have made it through the most difficult part of this ACF dome structure build.  Before everything gets painted I wanted you to see what the raw parts looked like in unfinished form.   Below are the aluminum front & back roof extensions, front & rear brass window assemblies and new center aluminum window section next to the plastic Budd dome.

Next, secure all the pieces together with CA glue.  Then sand, prime, repeat until smooth.  Here’s the latest photo of the new ACF dome assembly while waiting for the gray Tamiya primer to dry.

The above photo makes it easier to see the differences between the Budd and ACF style domes.  a.  No horizontal crossbars through the windows.  b.  Large center roof section. c. Tall side window for better viewing.

Stay tuned for the next step…

Looking forward to you tackling the “glass”!  Nice work !! JohnA

Thanks John, I’m working on installing the glass now 👍

The difference between the two styles of domes is striking.

@T.Albers, can you post a photo of your fabricated ACF dome and one from the LIONEL model in the same or similar angle of view?  I ask because I'd like to see how alike they are,

@Pingman posted:

The difference between the two styles of domes is striking.

@T.Albers, can you post a photo of your fabricated ACF dome and one from the LIONEL model in the same or similar angle of view?  I ask because I'd like to see how alike they are,

You got it @Pingman .   I'm just finishing the windows and hoping to post a progress update this afternoon.   

After that I will take a good photo to use as a comparison between the two domes.

Update 7, Nov 29th

According to the Union Pacific historical photos the tint color used on the dome windows has seems to have changed over the years.  I have found different online photos of same exact dome car where the tint appears to be light green, light blue, clear or smoke color.  I wanted my City of Los Angeles observation dome car to match the original 1955 photos, so I picked a light aqua green/soft teal color.

Note:  If you are trying to match the present-day look of Union Pacific’s excursion cars.  You can see in my October 2019 photo below the dome windows currently have a dark smoke tint.

Searching this O-Gauge forum I have found several different methods to tint dome windows but ultimately I needed four things at this point in the project.  1. Needed to create brand new windows.  2. Needed these windows need to be able bend and curve.  3.  Needed these windows to have light aqua green or soft teal color.  4.  Needed a color transparent enough to allow my guests to look inside and see the detailed passengers.

Finding the exact 1955 Union Pacific tint color was a challenge.  Some tints colors were too bright blue, others were too neon green.  Some tint colors were disqualified because they were too dark and others were eliminated because they had a mirror/reflective finish.   After a week of searching I decided on Solar non-reflective green color tint strips 8” x 6ft with D,I,Y kit from eBay. The reasons were, this tint was thick enough to be used as the window material and had a color was gradient. That meant I could choose the exact level of tint used on the dome windows.  Since I wanted my guests to still look inside and see the passengers I picked the lightly tinted section between 1” and 2” on the ruler.

With an airbrush I applied Tru-Color's Harbor Mist Gray #TCP-025 paint to the new dome structure. Then, painted the silver trim around the 12 window frames with a small paint brush.  Next, I sprayed with a flat Krylon clear coat.

Once dry, I trimmed the tinted windows to the correct sizes and installed them using canopy glue.  

I think this newly built dome structure and its window color are pretty darn close to matching this photo of the real Union Pacific 9004 observation car. http://rrpicturearchives.net/s...ture.aspx?id=4622976

Stay tuned for the next step…

Just keeps getting better and better!!! JohnA

@John A posted:

Just keeps getting better and better!!! JohnA

Thank you JohnA, the next step is creating a new interior for this dome

@Pingman posted:

The difference between the two styles of domes is striking.

@T.Albers, can you post a photo of your fabricated ACF dome and one from the LIONEL model in the same or similar angle of view?  I ask because I'd like to see how alike they are,

Good Afternoon @Pingman, here's the side by side photo you requested.

Hancock52 provided the top photo of the correct style ACF dome used on his 21" Lionel Union Pacific observation car.  Below his photo is a similar angle of the newly built dome for my 18" observation car.

Thanks,

Thanks.  Great work!

@T.Albers posted:

Good Afternoon @Pingman, here's the side by side photo you requested.

Hancock52 provided the top photo of the correct style ACF dome used on his 21" Lionel Union Pacific observation car.  Below his photo is a similar angle of the newly built dome for my 18" observation car.

Thanks,

Superb work, and yes, I think what you’ve produced is closer to the prototype than the Lionel version - which is saying a lot!

P.S. This is a very good illustration of something I realized a few years back, which is that working with hand tools you cannot duplicate the precision of machine made parts. I don’t have any metalworking skills, which is often a frustration, but in any case I really doubt that I could replicate the compound curves of a component like a dome.

@T.Albers, in an earlier post you mentioned trying to purchase the center section from a large hobby store.  Were they willing to sell you an entire dome assembly?  Or only a brass dome car kit?

@Pingman posted:

@T.Albers, in an earlier post you mentioned trying to purchase the center section from a large hobby store.  Were they willing to sell you an entire dome assembly?  Or only a brass dome car kit?

Funny you should mention that @Pingman.   I was surprised to find that hobby store only had in stock "ACF Dome Ends" part number OSA813 for $10.00 each.  They don’t carry the brass center dome sheet that matches these parts.  They said that center dome section is only available with the brass car kit.   I don't know who they are planning on selling all their packages of OSA813 ACF Dome Ends too if they don't have the center dome sections to make a full dome structure.  I didn't push the hobby store over the phone to see if he could get his manufacture to make just the brass center section by special order.   

For what its worth, their brass ACF Dome Ends are made to fit O-scale passenger cars that are 2.5" wide.

Oh! Its Des Plains Hobbies and their OSA parts line!

Update 8, Dec 1st

With all the modifications seen so far, it should be no surprise that my older K-Line dome interior would not fit into this newly built ACF dome structure.  It’s not a terrible loss because my old interior didn’t have a depressed center walkway and it could only fit 5 rows of bench seats when there should have been 6.

To make the new interiors floor I flipped over the dome assembly, got the important measurements and started building.  I began with a basswood floor that was 1/32” thick x 2” wide x 5.325” long.  To create the effect of a lowered walkway I installed two strips of 1/8” x ¾” basswood on either side to raise the floor under the bench seats.

In the photo below the angled lines drawn on the raised floor section represent where the bench seats will be attached.  Union Pacific was famous for turning their 7000 series (dome coach) and 9000 series (dome-observation-lounge) bench seats outward 10 degrees so passengers had better views out the large windows.

Once the main stairway with chrome handrails, front and back walls were installed I took the easy route and re-used my passengers and burgundy colored bench seats from my old dome’s interior.  Two additional K-Line bench seats part# K4400-009-02 were purchased from Brasseur Electric Trains at .50 cents each and trimmed to fit this application.  The new ACF style interior now allows for 12 bench seats, a ½” wide depressed center walkway and has more headroom inside for the passengers.

Stay tuned for the next step…

Update 9, Dec 4th

Finally, here’s the finished views of the new ACF style dome installed on my 18” K-Line observation dome lounge car.  The new ACF dome structure blends in well with the factory's Harbor Mist Gray roof paint and overall I’m pleased how it turned out.

While I had this car apart I took time to install the correct sized diaphragm with striker plate up front (part# 48-225) and two fresh air vents (part# 48-231) from ScaleCityDesign.  On the roof I added wire & cable duct covers that were made out of brass ½” flat strips to match the original Union Pacific plans.  The gray colored trucks that came with this car were changed out with K-Line trucks that were bright aluminum in color.  Now the truck's color accurately matches the mid-1955 through 1971 Union Pacific paint scheme.

After everything was put together I took these final photos and noticed a fun bonus.  That was the gradient tint used on dome windows gives viewers the impression the windows are polarized.  I’ll just tell my guests it was planned that way.   :-)

Thank you for following this project.

Great modeling..... really enjoyed following this project. JohnA

@John A posted:

Great modeling..... really enjoyed following this project. JohnA

Thank you John!  I'm happy with the end result.

This passenger car is back on the track now.  Here's a side by side look of the new ACF style dome next to the original Budd style dome.

@T.Albers, phenonenal project:  repositioning the dome to achieve prototype proportion requiring donor shell for plugs; CNC'g dome roof and sides; glazing; etc.

If you have one, could you do take a photo of an unmodified car with your new one showing the relocation of the dome in comparison to the unmodified car?

Again, fantastic project.

Great work!

It would be fantastic if somebody would design/sell a 3D print of correct plastic dome inserts for the various K-Line 21" dome cars for those of us with less skill.  The K-Line 21" aluminum dome cars are terrific scale-sized cars but the weak point is usually the plastic dome insert.  It would be great to be able to correct that deficiency.

Wow great job. You have some skills sir 🙂.

I agree!  Very nice work.  The K-Line cars are gorgeous, but their domes suck.

My domes are made from the original kit - the metal is closer to .020.  That makes them easier to bend.

The original was photo-etched brass.  I am sure the master still exists, but photo etching has become difficult and expensive, due to hazardous materials.  No wonder they don’t want to rob a kit for you.

@Jtrain posted:

Great work!

It would be fantastic if somebody would design/sell a 3D print of correct plastic dome inserts for the various K-Line 21" dome cars for those of us with less skill.  The K-Line 21" aluminum dome cars are terrific scale-sized cars but the weak point is usually the plastic dome insert.  It would be great to be able to correct that deficiency.

Thank you @Jtrain 👍.

I agree with you on a replacement 3D printed ACF dome structure.  There has to be an O-gauge enthusiast out there with a 3D printer that can make  replacement ACF domes for all those K-Line, Williams, Weaver, Phoenix Railways and Lionel passenger cars that came with incorrect dome structures.  This seems like the perfect project for a 3D printer.

This car is a(nother) masterpiece by @T.Albers. Nuff said, except that it is also unique.

@Lou1985 posted:

Wow great job. You have some skills sir 🙂.

Thank you Lou, 👍

@bob2 posted:

I agree!  Very nice work.  The K-Line cars are gorgeous, but their domes suck.

My domes are made from the original kit - the metal is closer to .020.  That makes them easier to bend.

The original was photo-etched brass.  I am sure the master still exists, but photo etching has become difficult and expensive, due to hazardous materials.  No wonder they don’t want to rob a kit for you.

Thank you @bob2 👍

I was reading an older post and saw were you built a full Kemtron ACF dome structure for your K-Line passenger car.  You did a great job!  Do you remember the length of your brass roof from Kemtron?  I would guess its a full 6.5" roof and matches a 21" car great.  But that 6.5" roof might be too long for a semi scale 18" car like mine.

Also, these ACF dome ends offered by Des Plaines Hobbies are identical to the original Kemtron part.  It looks like Des Plaines Hobbies still offers Kemtron parts, just relabeled as O Scale America.

Thanks,

@Hancock52 posted:

This car is a(nother) masterpiece by @T.Albers. Nuff said, except that it is also unique.

Thank you Hancock52, 👍

@Pingman posted:

@T.Albers, phenonenal project:  repositioning the dome to achieve prototype proportion requiring donor shell for plugs; CNC'g dome roof and sides; glazing; etc.

If you have one, could you do take a photo of an unmodified car with your new one showing the relocation of the dome in comparison to the unmodified car?

Again, fantastic project.

Sorry for the delay @Pingman, here's the answer to your question.

In this overhead comparison the unmodified Budd dome is in the bottom of the photo.  The front of both cars are facing to the right side of the photo.  Also, I included the distances from the domes edge to the shells opening on the ACF dome to make it easier for anyone that wants build there own ACF dome structure.

Hope this helps with your project!

Thanks

Wow !!!

Great thread !!!

Thank you to all posters.

CB&Q Bill