Window Framing

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ccvstmr
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Window Framing

Post by ccvstmr »

Background

With some recent interest in making window frames, thought I'd start a separate thread rather than bury this in recent passenger car threads.

Several years back, there were several hobby suppliers selling die cast window frames in what they called: small, medium and large sizes. Figured there must have been one guy casting these and selling them to various suppliers. The die cast windows were identical. During the 2014/2015 rebuild of my cupola caboose, was looking to purchase some more small windows...but nobody had any available in stock for sale. So, when it came to model building or rebuilding...was either stuck with what's available in the hobby market...or bite the bullet and make my own.

By the time the passenger car project came around, we knew we'd need (4) different windows. None of those were close to the die cast window dimensions. Honest Dave and I considered several methods of making window frames including low temperature melting metals. Low temp melting metal wasn't cheap and we'd need to make re-usable molds that could withstand the metal melt temperature. Never did find a good combination. Making window frames from strip wood would have been VERY time consuming. Doll house window frames were looked at. Size, cost and style were a problem. Remember, we needed some (100) windows in (4) different window styles for our cars.

Our local club has a 1" scale guy that markets rolling stock using cast polyurethane resin and silicone rubber molds. Talked to him and found out what he was using. He suggested we visit Reynolds Advanced Materials showroom in the Chicago area. These folks sell the Smooth-On line of molding making and casting products. Showroom people were all friendly, knowledgeable and helpful. We explained our project and they came back and said the same products suggested by our 1" scale contact were best suited for our application.

Okay, we got our material and supplies. The end of the process was taken care of. Had to make something to replicate. My window design experience started with those die cast windows...here's the face and back side of the small and medium sized windows.

IMG_4086.JPG

The face of the window has a wide-r edge frame or flange. This, to cover any inconsistencies when cutting the window opening in the sides of the cars, caboose or other. Provides more surface area to attach the window frame to the car body. The window glazing would be somewhat recessed. The window frame rear view shows several pegs. Assumed these were leftovers from the die cast process, but also act to provide additional grip when the frame is in the window. We would not replicate that part of the die cast window. You will note the inside portion of the frame has a recess. We would use that area for the glazing. That recess was about .060" deep...perfect for 1/16" acrylic glazing.

After scaling the windows from whatever information references were being used, it was time to draw something in CAD. Here's the side window drawing for the window exterior of the shorty passenger cars.

ccv side window exterior.JPG

On the right, is a side cutaway view of the window frame. Can see how the frame was "stepped back in 0.100" increments for each level of the frame with the glazing recess of 0.060" or 0.100". The face window frame was designed to have a 3/16" wide lip around the perimeter of the window for gluing and hiding window cutout inconsistencies.

Since this was a double hung windows, selected a piece of 1/2" alum plate make the window pattern. The view in the middle are the basic window dimensions. The view on the left shows the machine dimensions. Once the frame had been roughed out, would use a 3/32" square end mill to cut and creep up on the recess inside dimensions. The small circles you see in the corners represent the cutting tool. Used the center of the cutting tool to establish mill DRO coordinates. The final .005" to .010" cuts were done by climb cutting...high speed and slow feed. This seemed to leave a nice, clean surface. And brought the window recess to its final dimension.

You'll note there's no good way to make a square inside corner. By using a 1/8" or 3/32" diameter end mill...can be pretty close. And for that practice the 10 foot role...the window will look just fine from 10 feet away. And if anybody complains...simply ask them to show you THEIR windows!

A similar set of CAD drawings was prepared for the rear or inside of the window frames.

ccv side window interior.JPG

You'll forgive me as might jump around to different style windows. Don't have a collection of photos for any one window style to take you all the way thru the process.

The clerestory window frame was machined 1st using a 1/4" thick piece of aluminum plate. After the perimeter was squared up, started to remove the center of the window. As for window order, we started with a small window as were grew confident of our skills and methods and worked our way and then worked our way up to the larger passenger car windows. Here's the back side of the aluminum machined clerestory frame so you can see the shoulders on the back side of the frame.

IMG_1373.JPG

While working on the CAD drawing for the shorty passenger car side windows, realized the window frame would be MORE than 1/2" thick. Not only would that require a thicker piece of aluminum from the scrape box, would have also used considerably MORE silicone rubber compound to make the mold. So, Honest Dave and I opted to eliminate the bottom window sill and take care of the sill with wood strips on the car sides. Therefore, the cast window frame would sit directly on the wooden window will. Here's the side window face side...

IMG_1732-1.jpg

Don't mind the blue in the back ground for now. Will note here...you'll need to eliminate any surface blemishes or deep scratches in your pattern. Else, those will be transferred to the mold and ultimately your casting resin. Sometimes, sand blasting the pattern has a way of diminishing such surface imperfections.

With (2) the patterns ready to cast, was time to make a mold box. Honest Dave came up with some aluminum angles (suggest use 1.5" angles for this) and (4) small "C" or spring clamps to make an adjustable mold box. After the mold box size was determined, the side pieces and clamps were set accordingly. A heavy piece of foam board was used as a base. Eventually, used blue masking tape to secure the mold box to the foam board.

DSC02074.JPG

Next time, we'll start on the mold making. Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
I don't walk on water...I just learned where some of the stepping stones are!
I love mankind...it's some of the people I can't stand!
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Dick_Morris
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Re: Window Framing

Post by Dick_Morris »

The thinnest glass I have found is from Delphi Glass, .8mm (.032") micro glass in 8"x12" sheets for $4.55. (Also 12"x16" sheets for $8.95.) Their Lower 48 cheapest shipping is $27.27, a bit overpriced but affordable. But it's $67.52 to Alaska and I'm not willing to let them gouge me for that much. I haven't had any luck finding another supplier.
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Greg_Lewis
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Re: Window Framing

Post by Greg_Lewis »

If 1/16" works, you can get that in the cheap picture frames from the dollar store.
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.
ccvstmr
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Location: New Lenox, IL

Re: Window Framing

Post by ccvstmr »

Dick and Greg...thanks for your posts. Went to Menards and purchased a 30" x 36" x 1/16" piece of plexiglass for something like $20. If I recall, made most, if not all of the window glazing needed for the (100) window frames in the four passenger cars that would soon be cast. Asked Honest Dave to assist when scoring and breaking the longer strips of material over a square edge. For the part, there was little waste. Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
I don't walk on water...I just learned where some of the stepping stones are!
I love mankind...it's some of the people I can't stand!
ccvstmr
Posts: 2230
Joined: Sat Jan 04, 2003 10:37 am
Location: New Lenox, IL

Re: Window Framing

Post by ccvstmr »

Not So Moldy Oldy

With the pattern machined, took the aluminum window frame and sand blasted both sides to remove any tooling marks, round the edges sightly and prepare the window frame for silicone mold making.

As part of the original supply purchase, we also got some Sculptex modeling clay. This material came wrapped in plastic. For just under $5 you get a slab of clay, approx. 1/2" thick x 3" wide x 8" or 10" long. Sculptex clays are an oil based clay that doesn't harden, but can be purchased in one of (3) different hardnesses: soft, medium or hard. Believe we got a couple slabs of the "soft" clay.

Smooth-On suggested there should be at least a 1/2" of space between the pattern and mold box on all sides including the top and bottom faces. Using the clerestory window as our "test subject", cut a chunk of the clay right from the plastic and used that as is. The adjustable "box frame" was clamped around the clay and the frame taped to the foam board base. The clerestory window frame pressed back-side down into the clay. Decided to use the back side of the window perimeter frame/flange to be the location of the mold parting line.

IMG_1545.JPG

The corners of the aluminum box frame were "sealed" with clay as well. The exposed clay surface was smoothed as much as possible and most important, the clay was smoothed up against the sides of the aluminum window pattern. Any gaps between the clay and pattern would be transferred to the silicone mold and ultimately to the window resin casting...creating more finished window cleaning effort.

Was suggested "index pins" be used so the two halves of the mold always go together the same way. Reached into my pocket and used the butt end of a Sharpie pen to make index depressions in the clay. Did not put any index pins in the top of the mold (left side in the photo) as this is where the resin fill and air vents would be cut in later on. The mold box was coated with several applications of mold parting spray.

IMG_1546.JPG

Used the Smooth-On Mold Star 30 silicone rubber kit to make the mold. This material has a 45 minute pot life and a 6 hour cure time. We purchased a couple 2# "test kits". Each kit cost approx. $30 to $35. Two bottles are included in the kit labeled: A and B. The two-part mix would be measured in 1:1 amounts. There are other silicone rubber mixes available with differing pot life and cure times.

We estimated (guesstimated) how much silicone mold material would be needed. Dispensed 1/2 that amount of part A into a clean mixing container and then added an equal amount of Part B. Mixed the materials together thoroughly and poured into the mold box.

IMG_1547.JPG

While the silicone rubber was supposed to cure in 6 hours, believe we let the rubber cure for a good 24 hours. Last thing you want is to pull the mold out too soon and find it hasn't fully cured. When the mold box was stripped away...we had what looked like a casting parfait. Okay, looks like we mixed a little too much for the 1st silicone rubber our. No harm done.

IMG_1558.JPG

The modeling clay was separated from the silicone rubber. Made sure the pattern was still embedded in the silicone rubber. Assembled the mold box around the rubber with the pattern in place. Can now see the Sharpie pen "index pins" facing up from the original silicone pour.

IMG_1559.JPG

Once again, the mold box, rubber and pattern piece were sprayed with mold separating spray. Another batch of silicone rubber was mixed up and poured into the mold box. 24 hours later, we had a clerestory window silicone rubber mold. Somewhere inside that block of silicone, was an aluminum clerestory window pattern waiting to see the light of day.

IMG_1564.JPG

Even after using the mold parting spray, it still took a bit of effort to separate the two halves of the mold. Took my time. Didn't want to tear the rubber. Worked my way around the block edges pulling the two halves apart using my thumbs only. Eventually, the two halves came apart.

Next time, will finish preparing the mold and start making some window frames. Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
I don't walk on water...I just learned where some of the stepping stones are!
I love mankind...it's some of the people I can't stand!
ccvstmr
Posts: 2230
Joined: Sat Jan 04, 2003 10:37 am
Location: New Lenox, IL

Re: Window Framing

Post by ccvstmr »

Cast Off!

With all of the silicone rubber material poured for the clerestory windows, was time to separate the (2) halves the mold. While mold separating spray was applied before the 2nd silicone pour, still had to work to get some air in between the two mold halves. Used my thumbs to work the rubber halves apart slowly starting at the corners and working my way around the mold. In time, the mold came apart.

IMG_1565.JPG

Yep, the aluminum window pattern was still there.

An X-acto blade was used to cut (2) "V" grooves at the top of the mold...on the back half only. Why? To minimize casting clean up later on for the window casting face. One of these grooves would be used to fill the mold with resin. The other groove was an air vent. Both halves of the mold were dusted with foot powder. Excess powder was blown off. The rubber mold was assembled. Used some plywood backing boards and rubber bands to hold everything together.

For these windows, we used Smooth-On, Smooth Cast #320. There are several resin compounds in the 300 series family. The #320 has a 3 minute pot life and a 10 minute cure time. Other 300 series resin mixes provide longer pot life, or longer cure time or both. Color is off white. Once again, using the 2# "kit", you get a bottle of resin and a bottle of hardener (never could tell which was which. Bottles are only identified as Part A or Part B in different colored bottles...yellow or blue. These "kits" run in the $30 to $35 range as well.

For the clerestory windows, didn't need a lot of resin. Our original guesstimate of materials was high. What wasn't used went in the garbage. So with each successive window pour, we would cut back the amount of material dispenses from the bottle. An electronic scale was used to measure each part. Started by "zeroing" the scale with a Dixie Cup on top. Need to be careful when dispensing the materials. Pour too much in the cup of the first compound...you can pour some back. Once you add the 2nd compound...you're committed. Pour too much...the mix might as well go in the garbage.

As soon as the 2nd compound is in contact with the first...the clock starts. Take your time, mix too long or get distracted...and the resin WILL harden in the bottom of the cup. Time to start over. Best to concentrate. Measure carefully. Mix quickly. Introduce as little air as possible to the resin mix. Squeeze the mixing cup so there's a pouring lip and aim carefully to get the resin in the fill hole. When the mold is full, you can discard any remaining resin mix. Soon enough, the resin mix turns an off white color.

IMG_1569.JPG

When the resin pour was complete, the timer was set. 10 minutes later, it was time to de-mold. In the next photo, the "white-ish" residue on the face of the rubber mold is the residual foot powder. The window casting was removed from the mold. After several pours, it will be necessary to wipe the foot powder residue from the mold. When removed from the mold, the casting is still somewhat "soft". Set the casting on a flat surface with weight on top to keep it flat and hopefully prevent warping. Any piece of scrap steel or brass will do. After all, the resin is still curing.

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The casting "sprues" can be removed now or leave them intact and remove them later when the window has fully cured.

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One of the problems we ran into early on was...as long as the mold sat flat on the table, air bubbles would remain in the horizontal parts of the casting. After the mold was wiped clean, refreshed the foot powder coating and closed up, set the mold on something to tilt the mold and allow a path for air bubbles to escape. Could also "pump" the front/rear of the mold to give the air bubbles some incentive to move. If needed, we adjusted our Part A and Part B mix amounts (by weight)...and repeated the process.

Over time, we were letting the resin cure for a longer period of time before de-molding. Maybe as much as 15 minutes. Still, we were able to cast 4 to 5 windows per hour. Next photo, you can see how we used a die-cast window to tilt the rubber mold and allow air bubbles in the horizontal window pieces an escape path. There's a brass plate to the right that was used as a hold down weight.

IMG_1630.JPG

Next photo shows the "casting department" that was set up at Honest Dave's. We basically took over one of the work benches in the shop. With (4) different types of windows to make rubber molds for and (100) windows total needed (plus a couple spare windows each style)...we consumed a lot of material. Windows visible on the bench include the narrow clerestory windows for the shorty passenger cars (needed 36 windows) and the coach windows for Dave's Central Pacific coach car (needed 24 windows).

IMG_1706.JPG

Next time, will discuss window casting cleaning and show you the other window frame rubber molds and castings. Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
I don't walk on water...I just learned where some of the stepping stones are!
I love mankind...it's some of the people I can't stand!
Steamin
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Re: Window Framing

Post by Steamin »

ccvsmtr, Appreciate the detailed posts and pictures of the build, especially with new materials/processes (casting plastic). Look forward to the next update!
Steamin
ccvstmr
Posts: 2230
Joined: Sat Jan 04, 2003 10:37 am
Location: New Lenox, IL

Re: Window Framing

Post by ccvstmr »

Steamin...you're welcome! Nice to know the info is/will help someone in the future. The process isn't difficult. There's usually a bit of apprehension when you start something new. Once you've made your first complete casting...the process gets very repetitive.

Anyway, been away from this thread for too long. Need to get going as the series draws to a close. Stay tuned. Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
I don't walk on water...I just learned where some of the stepping stones are!
I love mankind...it's some of the people I can't stand!
ccvstmr
Posts: 2230
Joined: Sat Jan 04, 2003 10:37 am
Location: New Lenox, IL

Re: Window Framing

Post by ccvstmr »

Other Windows

Figured I'd side track again (sorry) and to show some of the other window mold examples for the passenger car project. Didn't get a photo of all the molds, but think you'll get the idea.

The shorty passenger car side windows were nominally 5.25" high x 3.625" wide. These were the largest of all (4) window castings made. Adding a 1/2" to each side of the window...the mold box was getting large. Meant more rubber mix would be needed too.

Decided the best way to cast this window would be on it's side. Of critical importance was to make sure air bubbles had a way to vent/escape. Dave machined several brass cones to use as fill/vent ports. Most anything could be used for the fill/vents...plastic, aluminum, wood, etc. The cones were used this time when the 2nd part of the silicone rubber mold was poured. Note 3 of 4 vents are located over vertical parts of the window frame. When it was time to pour, wanted to fill the mold quickly before the resin mix started to set up.

IMG_1727.JPG

After the 2nd silicone rubber pour, the halves of the mold were separated. We were ready to start mixing/pouring resin after the mold preparation was completed (foot powder dusting).

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Once again, the mold was raised on one end to allow air to escape...but not so much that we would not see mixed resin start to fill the upper vent hole. The resin mixture was poured into the lower hole. As soon as we could see resin in all the holes, we knew the mold was full.

Used lots of rubber bands to securely hold the mold halves together and minimize casting flash. Found over time, the rubber bands would get some stretch in them. Threw those away and used new-er rubber bands for this part of the casting process. Plywood backing boards were used. In fact, would sometimes "lightly pump" the plywood backing boards to ensure air bubbles could be pushed towards a vent.

IMG_1737.JPG

So what happens if you take to long to mix and dispense the 2 part resin? ...or put too much hardener in the mixing cup? ...the resin sets up before the mold is filled. Chalk this up to...lesson learned! Mix quickly and try not too induce air bubbles to the mix. next photo you can see how the resin mix started to fill the (3) parts of the window before the pour was finished.

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Some other mold examples...

Here's the mold box for Dave's coach car window. The window was a relatively simply pattern. Note the vent and pour cones located directly over the vertical parts of the window frame...quick fill...easy vent.

DSC02089.JPG

The last of the (4) windows to share is the baggage car window. Sorry, don't have a photo of the mold. The window pattern was basically a smaller version of the side window for the shorty passenger cars. This time, the lower window sill was included with the original pattern. This rubber mold, like some others, was made to sit on its side for the resin fill and air vent openings.

IMG_3089.JPG

Next time, will cover the casting cleaning and preparation for painting. Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
I don't walk on water...I just learned where some of the stepping stones are!
I love mankind...it's some of the people I can't stand!
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