One Last Shorty

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

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ccvstmr
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Re: One Last Shorty

Post by ccvstmr »

WINDOW PAINS - Part 1

Yes, that was purposely misspelled. The wood work on the car body was for the most part done at this point. But the objective of this project was to NOT build a wood sided box car or refrigerator car. Car #7 would need something to "let the light shine in"...windows.

Looked on line for parlor and rear end observation car examples. Peaslecreek offered assistance from afar by flipping photos my way. Some of the photos featured some rather unique arrangements like this...

Elegant curved window parlor car.jpg

Note the rounded glass on the back end of the car. Nice, but perhaps a little TOO elegant for my taste. Besides...I'd have to figure out how to heat and flex a piece of acrylic AND would have to frame that too. Thanks, but I'll admire that work from afar.

The side windows had round tops or more like oval tops. That had possibilities. Here again, would have to cut the car side to that profile and fit that kind of window into the car side. Cutting the car sides for that kind of opening concerned me.

Here's another example...

PCEBridgeRiver.jpeg

Had already decided I'd like to pursue the "round top" window arrangement. This would be departure from the square windows used for #5 and #6. As I considered this "problem", I was thinking, I could machine a pattern from aluminum and then pour resin castings as before. That's only half the battle...had to figure out how to install these windows. Would I need special tools and tooling to cut the window openings into the side of the car? That was when I had one of those "AHA!" moments. A cordless drill and a hole saw. PERFECT!

To maintain this similar window appearance as #5 and #6, I selected a hole saw size that would produce windows for car #7 that would end up being nearly the same width and height. Found that a 3.25" diameter hole saw would cut the appropriate outside diameter for the window. The inside diameter would be 3.00" diameter. The difference was basically the cutting width of the hole saw itself...approximately, 1/8". Thick enough for the window frame.

Came up with the following drawing: the window dimensions for car #5 and #6 with their squared off window design on the left. The new window design dimensions for car #7 on the right.

parlor window 053120.jpg

The question now was...how many windows would be installed and with what arrangement. The beauty of the CAD program is the ability to copy, paste and repeat the pasting. Here's what I ended up with...a design that didn't look too crowded, but certainly had enough viewing glass. Instead of using the same round top window design on the sides of the observation deck, opted to simply make a round window, about the same diameter as the round top and then make a smaller round window for the opposite end of the car where a lavatory might be located.

car #7side view 021022.JPG

Decided the observation deck end of the car body would also get a couple round top windows like used on the car side and be arranged as follows. As luck would have it I could fit the round top windows between the corner wall frame and the door frame.

car #7 end view.JPG

No doubt, the appearance of the car was starting to take shape. Would look similar enough to cars #5 and #6, but different enough to represent a special purpose car.

The window fabrication tally...would need (12) round top windows, (2) large round windows and (2) smaller round windows. The large round windows would get a machined from aluminum plate. The window plexiglass be retained by an inner machined aluminum ring. The small round windows would also be machined from aluminum plate and only need a retaining ring for the plexiglass.

Next time, we'll get started on making windows. 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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Steggy
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Re: One Last Shorty

Post by Steggy »

Following this project with interest, as it is demonstrates there’s a lot more to railroads (full-sized and model) than just locomotives. :D Granted, a smoking, belching locomotive is indeed very interesting, but the huge variety of cars that locos have been dragging along over the years is as equally-interesting, even more-so in the current era in which Diesel-electric freight engines all look, smell and sound alike.
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ccvstmr
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Re: One Last Shorty

Post by ccvstmr »

Steggy wrote: Sun Jan 22, 2023 6:05 pm Following this project with interest, as it is demonstrates there’s a lot more to railroads (full-sized and model) than just locomotives. :D Granted, a smoking, belching locomotive is indeed very interesting, but the huge variety of cars that locos have been dragging along over the years is as equally-interesting, even more-so in the current era in which Diesel-electric freight engines all look, smell and sound alike.
Thanks Steggy...(BDD now equals Steggy). There was a time when the more interesting parts of a train going by were at the front and back of the train. Can't really get excited by a FRED going by...unless it's missing...which implies a mishaps somewhere down the line. As for car #7...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
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Re: One Last Shorty

Post by ccvstmr »

WINDOW PAINS - Part 2

Following the last post regarding window type and design...and now having made a drawing...and now having determined the various window dimensions...it was time to start carving a pattern that could be molded to make (14) duplicate windows for car #7 (plus a few extra).

Pulled a chunk of 1/2" thick plate aluminum from the scrap bucket and squared that up for the window outer dimensions. Cleaned the aluminum and covered both front and back sides with dye. When both sides were dry, scribbed the window layout on both sides using the same bottom and side for references. Why? The most critical part of the window layout would be the center point of half round window. Had to insure the recessed shoulders, front and back, were in good alignment. A "prick mark" was stamped on both front and rear sides of the aluminum. This was the 0-0 reference point.

Once set in the mill vise, holes were plunged for the main window and the half round window. Used a roughing end mill to chew out most of what would eventually become the two window openings. Left more than enough metal for final clean up.

IMG_5615.JPG

When the main window opening machine work was finished, the aluminum frame was flipped face down to machine the window mounting flange and other window back side recesses. There was no flange on the bottom of the window. A wooden window sill attached to the car body would take car of that. In particular when the sill spanned several windows. The vertical sections of the window frame are approx. .060" thick.

IMG_5621.JPG

When the machine work front and back were completed for the lower window section, dragged out a little 6" rotary table to machine the arcs for the half round window. Once secured, used a pointed wiggler to pick up the half round window center prick mark. Final profile cuts were done with an 1/8" carbide cutter and climb cutting (leaves a better looking finish).

From this point on, having the half round window center mark was no longer needed. The prick mark was machined away. When the window face machine work was finished, flipped the frame over one more time to machine the window recesses for the back side. All the time hoping I didn't make a wrong table move (wouldn't be THAT noticeable on the back side of the window)!

IMG_5622.JPG

After removing the window frame from the clutches of the rotary table...here's what the front of the aluminum window pattern looked like. Had a window frame with a "mounting flange" around the perimeter and the necessary recesses to look like a double hung window.

IMG_5628.JPG

Turning the window over, here's how the back side looked with the necessary recesses machined to hold the window glazing pieces which would be inserted later on.

IMG_5629.JPG

After several hours of whittling away at the slab of aluminum, we got us a window frame pattern!

Molding and casting these windows would be done over at Honest Dave's shop. But before the molding process was started, the window frame was glass bead blasted to remove the sharp edges and mill tooling marks.

Next entry...will show/explain the process of making a 2-part mold. 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!
Odyknuck
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Re: One Last Shorty

Post by Odyknuck »

Nice way to make a mold.
djjh87
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Re: One Last Shorty

Post by djjh87 »

Carl you are raising the bar on us nice job. Jim
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ccvstmr
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Re: One Last Shorty

Post by ccvstmr »

Ody...will be getting into how to make a mold next.
Jim...I've got short frame (this is all my parents gave me)...so, I can't raise the bar too high! :lol:

Thanks for the compliments guys. 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
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Joined: Sat Jan 04, 2003 10:37 am
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Re: One Last Shorty

Post by ccvstmr »

Window Pains - Part 3

Well, this would have been so much easier if there were commercially available windows that could be purchased. When starting construction of cars #5 and #6, looked for available windows on-line. Outside the doll house hobby, there wasn't much available and most doll house accessories are 1/12th scale. Even the largest 1" scale windows would be too small.

Making window frames out of stick wood (bass or other) would have been terribly labor intensive. Would take and extremely long time as well. When Honest Dave and I got into the passenger car building effort, we figured we'd need some (100) windows in 4 different styles in all. There had to be a better way. We looked at casting in metal, but low temp melting alloy metals get expensive fast.

Next best solution was to try resin casting. If anyone is interested in pursuing resin casting, check out the Smooth-on.com website. While most of the products appear to be geared towards the "artistic" end for movie props, theater shows and more, Smooth-on like Loctite, must have been approached by many customers requesting existing products be modified to suit a particular application. Similar to Loctite that has a variety of products to choose from...the same applies to Smooth-on products for both molding and casting applications.

Primary characteristics on the Smooth-on data sheets for their 2-part rubber molding and resin casting compounds are: 1) mix ratio, 2) pot life, 3) cure time and 4) hardness. For making silicone rubber window molds, we were pointed in the Mold Star 30 direction. Here's a data sheet photo...

IMG_7490.JPG

If you look to the middle of the Mold Star 30 line, you'll see the mixed compound has a 45 minutes pot life and a 6 hour cure time. Once mixed, you've got 45 minutes to use. The cure time is self explanatory.

One of the recommendations from Smooth-on...is to provide a 1/2" of clearance on all sides of the pattern for molding purposes. Okay, we started with some molding clay (can be purchased from Smooth-On). The stuff comes in slabs about 3" wide x 12" long. With a window pattern measuring some 5.25" high x 3.75" wide...will need a clay base that's 6.25" high x 4.75" wide.

As the clay was massaged, set (2) 1/2" steel rods on either side of the clay and rolled the clay out like cookie dough. Measured and cut away the excess clay. Honest Dave had previously made some aluminum angles that could be clamped together at the corners to form a mold box. Clay would be rolled into a small string and then pressed into the corners to keep the rubber from seeping out.

When ready, the glass-bead blasted aluminum pattern was pressed into the clay, this is done as evenly as possible. Small spatulas are then used to insure the clay is pushed up against the pattern. The height of the clay against the pattern will determine where the casting parting line is located. Best to use natural pattern corners and edges. Any small gaps need to be filled with clay. Brass 1/2 cones were pressed into the clay to make fill and vent passages. Lastly, used the butt end of a Sharpie pen to create index dimples for the (2) mold halves.

IMG_5718.JPG

When satisfied the molding clay will not let any rubber go where you don't want it...there's one important step that should NOT be overlooked. And that is...spray the mold and mold box with MOLD RELEASE! It's recommended to give the mold in the form box 2 light coatings. I sprayed the mold from all 4 sides of the mold box...and then let that dry will preparing the rubber.

Time to mix some silicone rubber. 1st thing to determine is...HOW MUCH? Some basic math here will indicate that a 6.25" x 4.75" by 1/2" deep mold box volume needs to be filled. This comes out to (in round numbers) 15 cu. in. The two parts of the silicone rubber compound are mixed in a 1:1 ration. In other words...need 7.5 cu. in. of each Part A and Part B material. Good luck finding a measuring container calibrated in cu. in.

Honest Dave had a measuring container calibrated in CC's (cubic centimeters). Okay, don't pull your hair out. There's nominally 2.5 centimeters to an inch. A cubic centimeter would be 2.5 x 2.5 x 2.5 = 15 cc's (rounded off) for each cubic inch. Therefore, we're going to need 7.5 cu. in. x 15 cc's per cu. in. which comes out to 115 cc's of each Part A and Part B.

If you pursue this method for parts replication, you'll find that Smooth-On products are VERY FORGIVING when it comes to dispensing materials. We need 115 cc's of each part...but if you measure 120 cc's of one part and 110 cc's of the other part...as long as you're close to the proper ratio things will still work.

Using the calibration on the plastic cup, dispensed some 115 cc's of each part. Mixed THOROUGHLY! This includes using your mixing tool to scrape the sides of the measuring cup. Mold Star 30 has one white compound (Part A...I think) and one deep blue compound (Part B). It's easy to see any white left on the inside surface of the measuring cup. Since Mold Star 30 has a 45 minute pot life...you'll have some time to mix the two parts before pouring into the mold. But the clock does start when the two compounds come in contact with one another.

Smooth-On recommends "degassing" the rubber compound to draw off any air. Yeah right...every shop will have a vacuum chamber. If you do investment lost wax casting, you probably have such a chamber. We didn't. We mixed and poured...and let happen what happens. As the silicone rubber finds its level, could see tiny bubble rise to the surface and disappear. Those pock marks would not be visible after the rubber cured.

IMG_5723.JPG

Returning the next week, it was do or die time. The aluminum form box was removed. And started to lift the corners of the rubber to have a first look at one-half of the rubber mold.

IMG_5728.JPG

When the entire 1/2 rubber mold was removed, could look at the pattern, the clay and brass ports and the rubber mold. Also used this opportunity to trim the rubber that seeped up the mold form box walls.

IMG_5730.JPG

Okay, was now time to get ready for the 2nd silicone rubber pour. The aluminum mold box was reassembled around the rubber mold just made. The mold box corners were "sealed" with clay. The pattern was set in place in the rubber mold as were the brass ports. AND...once again, had to spray everything with mold release. Perhaps more important now than before as you don't want the (2) halves of the rubber mold to bond to each other.

IMG_5731.JPG

The 1st silicone rubber pour was for the window face. The 2nd pour will be for the back side of the window.

Since Chaski limits us to (6) attachments per post, I'll pick up here when I write the next entry. I'll be back. 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!
Odyknuck
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Re: One Last Shorty

Post by Odyknuck »

Really cool stuff and seems like a great way to make a lot of less expensive repeatable windows.
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rmac
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Re: One Last Shorty

Post by rmac »

Agree. This is fascinating.
ccvstmr
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Re: One Last Shorty

Post by ccvstmr »

Ody...your response is spot on. When you can't find anything commercially available, your choices are limited. Depends on the usual (2) criteria... 1) time vs 2) cost...and trying to find a reasonable balance between the two.

RMAC...glad you find this interesting. Like most things, you start with a bit a caution and nervousness. After the first item is produced, you're ALMOST and expert. With the skills needed for these kinds of parts, this opened other avenues in casting with resin and low temp alloy metals.

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: One Last Shorty

Post by ccvstmr »

Window Pains - Part 4

Time to keep moving here. So far, developed a window design with dimensions. Machined an aluminum pattern. Took that pattern and poured a two-part silicone rubber mold. Now, it's time to see how well the pattern will replicated using polyurethane resins.

After pouring the 2nd half of the mold and waiting a week to visit Honest Dave's shop, it was time to separate the mold halves and remove the pattern and brass cones. Once the mold box was unclamped and set aside, used a shop knife to cut a shallow bevel on all the rubber edges. Unless the silicone rubber mold is damaged, will most likely NOT need the pattern again. But, will keep that patterns with the others made.

IMG_5758.JPG

Let's talk about resin casting...

Same as previously cast windows for cars #5 and #6, Smooth-On Smooth Cast 320 was used. This is a 2-part polyurethane compound mix. Comes in 2 bottles. Smooth-On doesn't say which bottle has what, but one bottle most likely contains the resin, the other bottle contains the hardener. Kind of like epoxy or JB Weld, etc. Throughout our casting experience, we were purchasing what's know as "1.9 pound trial kits". This is the smallest quantity that can be purchased. You get 1 pound of Part A (resin?) and 0.9 pounds of Part B (hardener?). Will explain this.

Per the instructions, you can mix the two parts by volume...in which case a 1:1 mix ratio is used. If you mix the two parts by weight, then you weigh out 1 part of Part A for each 0.9 parts of Part B. I'll get back to this. Smooth Cast 320 has a 3 minute pot life. Once the 2 parts come in contact with one another...mix quickly and pour into the mold. Else, you end up with a slug of hardened resin in the bottom of the mixing cup. Or as I had happen early on...the resin turned on me DURING the pour! Had to throw that away and then start over. Once poured into the mold, the cure time is 10 minutes. Mixing and pouring the resin goes a LOT faster than mixing and pouring the silicon rubber.

The next question would be...how much of each part needs to be mixed? The data sheet includes information regarding the specific gravity of the compounds. Using that can cause a headache when figuring material needs. We made a somewhat SWAG...scientific wild ass guess. Pulled out a digital scale. Measured the weight of the aluminum pattern. Based on the weight in ounces, poured some water into a paper cup until we got the same weight of water (in ounces). Once we had the water weight, we knew what are estimated resin weight should be. Could then do a little math. As an example, if the water weight was 4 ounces...we get an equation like this...1X + 0.9X = 4...for 1 Part A per 0.9 Part B. Or... 1.9X=4. Solve for X. In this case, X=2.1. So we'll need 2.1 ounces of Part A and 2.1 x .9 = 1.9 ounces of Part B.

How close are these numbers? When you make your 1st pour, if there's too much resin left over in the mixing cup, cut back on both Parts A & B. If after the resin is cured and you find the casting is short after separating the mold...add some more Parts A & B in the same ratio. Once again, this is not an exact science. There's a little latitude here when dispensing...but do try to keep the quantities close to what's needed.

We found by mistake...when mixing according to weight (2 ounces each part per the above example)...the castings came out fine, but we emptied the Part B bottle before we finished the Part A bottle. Hence, the mix ratio by weight 1: 0.9. Next...if you're using a rod across the bottle opening to carefully dispense A and B into a cup on a digital scale...wipe that rod clean BEFORE touching the other bottle. And lastly, the polyurethane compounds have a bad habit of absorbing moisture. Once the A & B bottles are opened, they should be used up in 6 to 12 months. Else, casting problems will occur. You can try to put a nitrogen blanket over the materials before re-sealing the bottles. I tried electrical tape around the bottle top. Don't know how well that will work or how long that will extend the life of the materials. Enough about dispensing and mixing.

Let's make some window castings...

Cut some scrap plywood to act as "backing boards" on both sides of the mold. Used a bunch of rubber bands to hold the mold together. Found if we tipped the mold, we had a better chance of getting air bubbles to migrate to the top vent hole. In this case..."we thought".

Smooth-On suggests spraying the mold with release agent. If making a lot of castings, that might mean several cans of release spray. Instead, Honest Dave had the idea to use Goldbond Foot powder. Dumped a little on each half of the mold. Used a make up brush to "sweep" the foot powder in all the knooks and crannies of the mold and then blow off the excess over a garbage can. Backing boards were set on both sides of the mold. Rubber bands were stretched in place. Marked the rubber mold to know which was the top and bottom of the window inside.

IMG_5759.JPG

Don't recall how much of Part A and Part B were mixed for the round top window. Wrote that info down on the backing boards after the amounts were "dialed in". Lifted one end of the mold with a 1/4" or 3/8" thick piece of aluminum to TRY and give the air a way to escape. After 5 minutes or so, the yellowish A & B mixture starts to turn opaque. It's strange to watch the transformation thru the fill and vent ports.

IMG_5761.JPG

Used a kitchen wind up timer to keep track of the time. The timer was set for 10 minutes. When the timer rang, the rubber bands were removed. The backing boards were set aside and the mold opened. Could now see the result of the work done so far. Could also see a white-ish foot powder residue on the mold.

IMG_5764.JPG

The casting was removed and set aside on a flat surface with a scrap piece of metal on top as a weight to hold the casting flat. Even after 10 minutes, the casting was still somewhat pliable. The mold was cleaned and the process started again with the foot powder dusting, etc. The window casting fill and vent port "sprues" were cut off with a diagonal cutter. The excess sprue material will be sanded later along with the removal of any parting line "flash".

IMG_5817.JPG

Car #7 only needed (12) good window castings. Believe (21) pours were made. Were there problems with casting air bubbles? In a word...YES! Was frustrated by this. Knew Honest Dave had a Dremel engraving tool. Asked if I could borrow that. Decided to try a "Magic Finger" solution if you will...and the best part, no quarters were needed. So, held the engraver next to the mold and rubber banded the engraver to the side of the mold. Either before or after the resin mix was poured into the mold...turned on the "vibrator". Believe this helped.

IMG_5815.JPG

Have one more Window Pain part to share next time. Will show how I was able to save some window castings with air pockets and then close out window discussion to get back to car #7. I shall return. 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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