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Author Previous Topic: All Scale Rails Issue #26 2021 Topic Next Topic: Santa Fe Mechanical Refrigerator Car: Coming Soon
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Bernd
Fireman



Posted - 12/04/2020 :  5:04:52 PM  Show Profile  Visit Bernd's Homepage  Reply with Quote
quote:
Originally posted by Michael Hohn

Very nice acquisitions, Bernd. The vinegar works has always appealed to me. My introduction to resin kits was a Westerfield hopper. Are your kits flat castings or single casting bodies?

Mike



I just checked a couple of the boxes and they are flat castings. The vinegar works came from NJ. I knew a hobby store owner by the name of Jeff Kucsma. Him and his wife ran the Big Little Railroad Shop in SOMERVILLE, NJ. I just searched it out and I see they are closed down. Jeff knew the owner of the Railroad Shop in Piscataway, NJ. If I remember right that's where I got the kit. So it's been many years. There 1200 of these kits made and I have kit #501. Looks like now I've got to build it with all those Heinz refer cars.

I plan on taking a kit or two with me when we go up to the summer cottage this coming year. Wife is retiring and we'll probably be staying up there a couple of weeks at a time. I can't see spending all my time boating or floating in the water. Will need something to do on a rainy day.

Bernd


New York, Vermont & Northern Rwy. - Route of the Black Diamonds

Country: USA | Posts: 3993 Go to Top of Page

Bernd
Fireman



Posted - 12/04/2020 :  6:48:01 PM  Show Profile  Visit Bernd's Homepage  Reply with Quote
So I went into casting mode this afternoon. Iíll start by presenting my vacuum equipment. I used these items when I first got into making both resin castings and RTV molds. It consists of a refrigerator compressor, a few Pyrex glass bowls, a flat piece of plywood with some counter top Formica glued to it with a brass tube epoxyed in a groove in the wood and some a plastic hose. The bowls have a ring of high temperature silicone, the type used to seal exhaust pipes on power vented furnaces, as a air tight rubber seal.



Hereís closer look at the hole in the center of the board. The brass pipe runs up to the hole under the Formica.



The compressor is from one of those small refrigerators that are about 30Ē square that only hold bottles of beverages. All I did was splice in an extension cord. I never got around to installing a switch to turn it on. I have tested the vacuum power, these can pull up to almost 25Ē of mercury. Itíll pull the bubbles out of any RTV and resin.



This is the largest of the bowls. Itíll easily cover a cottage cheese container full of RTV, resin or any other casting material.



The three bowl collection.



Hereís an example of using the vacuum with a container under the bowl.



Hereís what it looks like when you pull a vacuum on Hydrocal. It looks like yeast rising. This was the first time I have ever used Hydrocal. My friend gave me some the other day to try. Glad he did. Hydrocal handles a lot different than Plaster of Paris.



Hereís the first disaster. I used about Ĺ a cup of water and then poured in the Hydrocal. I noticed that it was very watery so I added a bit more and it still was watery. I figured I better pour it before it starts to set. Hereís the result.





I noticed that the Hydrocal was getting a little stiff so I poured it into the next mold. It was still watery. Hard to really explain why this happened, but as you can see another disaster.





I decided it was time to RTFI. It states 1 ľ cup Hydrocal to Ĺ cup water. Mix and pour in 30 seconds. WHAT? Thatís a little too fast to learn for the first time around, but I poured the mold. Better success. It didnít crumble. I guess I need to develop a technique for pouring Hydrocal.





Again the excess I poured on to crumpled up aluminum.



Okay, on to making little blocks and building them up for the master pattern. This first attempt will be a trail run. There may be more than one trial run.

Iím using the Durham Water Putty blocks to build an experimental first wall to get the feel and process down. I look for the proper size blocks for the bottom of the wall. Iíll call these the foundation blocks. There will be two rows and then a narrower row at window height.

Iíve marked a block that I want to cut out.



Close up of the block and saw kerf. I use my fret saw with a course tooth wood blade for this.



I then sand the block so itís parallel all the way around and also sand out any taper from the cutting process.



Here Iím showing the profile along the block. The rock face youíll see is pointing down.



Nice and parallel along the length.



Next I scribe the stone to a specific thickness so they all match when glued to a support wall.



Now here comes the tricky part, cutting it length wise without cutting a taper into the part.



Success. Thereís a slight lip at the bottom that will be sanded flush.



And a jig to hold the blocks in place while gluing them on to the paper.



I printed the wall on a piece of paper after having drawn it up in CAD to the dimensions I developed for wall width and height. I used the 3M Adhesive tape to attach the paper to a piece of chipboard. I then used gator board to frame around the chipboard and drawing. Now you can see how I determined the thickness to the stones three pictures back.

Thatís it for today. Maybe more tomorrow, depends if the Honey Do List calls me.

Bernd


New York, Vermont & Northern Rwy. - Route of the Black Diamonds

Country: USA | Posts: 3993 Go to Top of Page

Carl B
Fireman

Premium Member

Posted - 12/05/2020 :  08:38:47 AM  Show Profile  Reply with Quote
Interesting vacuum chamber setup Bernd.

I've experienced Hydrocal is critical on the 60% powder-40% water ratio. The instructions calling out 30 seconds doesn't make sense.. But it claims a compression strength of about 6000 psi when cured. Or 3 times plaster of paris.

I'm really interested in the "stone" varieties you ordered. Mix ratios are different and they're rated at 10000 psi or more.



Country: USA | Posts: 4229 Go to Top of Page

Bernd
Fireman



Posted - 12/05/2020 :  11:02:57 AM  Show Profile  Visit Bernd's Homepage  Reply with Quote
quote:
Originally posted by Carl B

Interesting vacuum chamber setup Bernd.

I've experienced Hydrocal is critical on the 60% powder-40% water ratio. The instructions calling out 30 seconds doesn't make sense.. But it claims a compression strength of about 6000 psi when cured. Or 3 times plaster of paris.

I'm really interested in the "stone" varieties you ordered. Mix ratios are different and they're rated at 10000 psi or more.




I never knew that a fridge compressor also had a vacuum side until I took one out of a deceased fridge. I literally took a saw to the compressor to find out what makes it tick. So instead of buying an expensive vacuum pump I used the fridge compressor. On resin and RTV it works great.

The 30 doesn't make sense it because in my reading the tiny instructions on the container it says to shake gently for 30 seconds and working time is 5 minutes. Magnifying glass works wonders.

Speaking of mix ratios for the dental plaster, I'm going to see if I can find something on the net.

This is all new ground for me to work on so there's going to be failures. One thing I need to learn is to read and then re-read the instructions. (RTFI)

Thanks for the comeback.

Bernd


New York, Vermont & Northern Rwy. - Route of the Black Diamonds

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Bernd
Fireman



Posted - 12/05/2020 :  12:17:41 PM  Show Profile  Visit Bernd's Homepage  Reply with Quote
I came up with several great videos from a guy that is not boring to watch. He runs through the casting techniques without the "Ah's" or "Um's". Interesting thing is he describes casting plastic. That got my interest. Come to find out he's talking about resin casting. He gives a good explanation of casting dental stone in video #4. I included the other two video's, #3 and #5 for information. Well worth watching if your interested in casting something in either dental stone or plastic (resin).

Bernd


New York, Vermont & Northern Rwy. - Route of the Black Diamonds

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Carl B
Fireman

Premium Member

Posted - 12/05/2020 :  12:34:26 PM  Show Profile  Reply with Quote
Could you post the link to the videos Bernd?


Country: USA | Posts: 4229 Go to Top of Page

Bernd
Fireman



Posted - 12/05/2020 :  12:51:20 PM  Show Profile  Visit Bernd's Homepage  Reply with Quote
quote:
Originally posted by Carl B

Could you post the link to the videos Bernd?



Ya, that would be nice if I would post them.

A bit upset with a former forum I was on. I'm over it now.

Here they are:

https://www.youtube.com/watch?v=3soDNI0ZYtQ&ab_channel=HirstArts

https://www.youtube.com/watch?v=6mJrYxUVaAQ&ab_channel=HirstArts

https://www.youtube.com/watch?v=r3Tm0A7wSL4&ab_channel=HirstArts

Enjoy.

Bernd


New York, Vermont & Northern Rwy. - Route of the Black Diamonds

Country: USA | Posts: 3993 Go to Top of Page

Bill Gill
Fireman



Posted - 12/05/2020 :  2:20:53 PM  Show Profile  Reply with Quote
Hi Bernd, Never having done any plaster casting beyond animal tracks in the Boy Scouts, the only thing I remember being told was: alwyas add the plaster to the water, not the other way around. I appreciate you posting all your trials and testing.

As to refrigerator compresors, they are interesting critters. A few years back my son was actively engaged in converting a slightly larger refrigeration compressor into a steam engine to power a small boat...



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Carl B
Fireman

Premium Member

Posted - 12/05/2020 :  2:44:43 PM  Show Profile  Reply with Quote
Thanks for those links Bernd. I'm familiar with Bruce Hirst & his products.
Neat stuff..

Bruce is an excellent teacher. Unlike most, his videos are concise and to the point.

add the plaster to the water
Right Bill.



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Bernd
Fireman



Posted - 12/05/2020 :  3:33:28 PM  Show Profile  Visit Bernd's Homepage  Reply with Quote
Hi Bill,

Yes, add the plaster to the water. Have always done that but it's good point to bring for the newbies that want to try casting.

The compressor contains a Scottish Yoke. Any steam engine or for that matter any engine can be turned into a compressor as any compressor can be turned into an engine. At least I think they can.

Here's a 38 second video for those who are wondering what a Scottish Yoke is.

https://www.youtube.com/watch?v=k5gSeP8BVeM&ab_channel=LudicScience

Carl,

You're welcome. So you're familiar with his video's. I just came across them today.

Bernd


New York, Vermont & Northern Rwy. - Route of the Black Diamonds

Country: USA | Posts: 3993 Go to Top of Page

Frank Palmer
Fireman



Posted - 12/05/2020 :  5:59:49 PM  Show Profile  Visit Frank Palmer's Homepage  Reply with Quote

Rock on Bernd.


Frank

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Bernd
Fireman



Posted - 12/05/2020 :  10:12:33 PM  Show Profile  Visit Bernd's Homepage  Reply with Quote
quote:
Originally posted by Frank Palmer


Rock on Bernd.





New York, Vermont & Northern Rwy. - Route of the Black Diamonds

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thayer
Engine Wiper

Posted - 12/05/2020 :  11:08:09 PM  Show Profile  Visit thayer's Homepage  Reply with Quote
Bernd,

There are only a few minor differences between your setup and mine.

First, I am using an expensive vacuum pump I was lucky enough to cart off when the afore mentioned feature film shut down.

I have been using self-adhesive weather sealing foam as the gasket between my pyrex bowls and base. Your solution looks a lot better, as the foam "creeps" due to the circular shape, and I usually have to fuss with it at the start of each session. Thanks for the inspiration.

As for the base, I started with a scrap of laminate countertop, and it worked great, until it didn't. One day I was degassing some silicone for a mold, and there was a loud bang followed by a few seconds of hissing. I looked over to see my silicone coating the inside of the pyrex bowl, and the vacuum gauge at zero. Sure enough, the countertop base was MDF, and it bled enough air to delaminate the formica. Which, incidentally, is not up to spanning the rim of a 10 inch bowl when the vacuum is approaching 29 inches. I swapped out the broken base for a piece of high density plastic, about 1 1/2 inches thick, and all has been good ever since.

Lesson learned, if you ever think the bowl is causing an optical distortion of what you see inside while the seal is compressing, yeah, that's not what is happening. Bleed the air back in and get a new base.

Even after all these years, I still get a kick out of boiling water at room temp.

Sorry about the hydrocal trouble. I expect you will sort it out soon.

Thayer



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Bernd
Fireman



Posted - 12/06/2020 :  10:07:29 AM  Show Profile  Visit Bernd's Homepage  Reply with Quote
Thayer,

The base is a piece of birch plywood that has 13 layers and comes in 5 foot square sheets. IIRC it's called European Birch plywood and comes in metric sizes. I used that to build the base's of the kitchen cupboards. I then used Weldwood Contact cement to glue on the Formica. It hasn't blown up yet and doesn't look it ever will. I can't quite get enough vacuum to boil water at room temp.

The first time I used it to vacuum the Smooth-On RTV I had a mess. Couldn't believe how fast it came to a boil. Happened to the resin I vacuumed also. That was a worse mess. But through trial and error you learn what works and what doesn't. That's why I also shown my failures. It happens to everybody.

I found out the hydrocal will have a more watery consistency than plaster with the same amount of water. Mixed up a second batch of hydrocal and poured one of the bigger walls and it turned out better. Anybody need any talus rock?

Thanks for stopping in and commenting. Always great to hear from others on the same subject.

Bernd


New York, Vermont & Northern Rwy. - Route of the Black Diamonds

Country: USA | Posts: 3993 Go to Top of Page

BurleyJim
Fireman

Premium Member


Posted - 12/06/2020 :  10:39:32 AM  Show Profile  Reply with Quote
This is like watching "Mr. Wizard" 

Good stuff!

Jim



Take the red pill

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