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Bernd
Fireman
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 Posted - 12/06/2020 : 10:51:26 AM
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I need to step back here and regroup. I thought I had it all planned out. Make the molds, cast them, find which material works best to make individual blocks, start assembling the master pattern, cast the wall and I'm done. So right now I'm stuck at making the individual blocks. They are not coming out as consistent as I would like them to be. And I think I know what the problem is.
It's the rocks/blocks in this mold.
There are to many different sizes both length, width and thickness. After looking back at the pictures of the South River Model Works block roundhouse walls I've come to the conclusion that the blocks from the mold in the above picture also have to course of a face to be using on a building. They should be smoother. Like this wall I cast last night, minus the bubbles. I have to learn not to stir so many bubbles into the mix.
Looks like I'll be stuck in this stage of development for a bit. I'll report back all the failures and successes when I get a good block.
This is for Carl. After watching Bruce's video's on dental stone casting, I've decided to not use the dental stone material because he said after casting it it's actually stone. I think I would have a hard time and would be going through saw blades trying to cut out the blocks. The dental stone will be used for the final castings of the wall. I also didn't realize that this was not "dental plaster" it's "dental stone". Quite a difference in material.
That's it for now. Back to experimenting with what works and what doesn't.
Bernd
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| New York, Vermont & Northern Rwy. - Route of the Black Diamonds |
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Country: USA
| Posts: 3968 |
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Bernd
Fireman
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Posted - 12/06/2020 : 10:56:09 AM
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quote:
Originally posted by BurleyJim
This is like watching "Mr. Wizard" 
Good stuff!
Jim
Thanks Jim. More disasters .......I mean good stuff to come.
Bernd
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| New York, Vermont & Northern Rwy. - Route of the Black Diamonds |
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Country: USA
| Posts: 3968 |
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Carl B
Fireman
Premium Member
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Posted - 12/06/2020 : 3:16:04 PM
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Reporting failures is very helpful to everyone Bernd. I share the same issues in my own threads. Nobody's perfect.
dental stone will be used for the final castings of the wall
And that's precisely where you need the strength!
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thayer
Engine Wiper
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Posted - 12/07/2020 : 04:01:09 AM
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Bernd, I believe by actual stone, he means it has gone back to its previous physical state. Plaster of Paris could also be considered stone once it cures, as it is simply gypsum that has been ground up and heated to drive off the water. Adding water allows it to crystalize again, returning to its "rock" state. Different processing techniques and conditions give different results, thus the variation between PoP, Hydrocal, Dental Stone, etc. It is definitely harder than PoP when cured though, and given all the additional work you are using to build out your patterns, I would also use a softer product. The other good news is that PoP is less expensive than most other options.
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Bill Gill
Fireman
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Posted - 12/07/2020 : 07:05:04 AM
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Bernd, a couple thoughts
The holes from the bubbles can easily be filled with a variety of stuff you probably have around.
In the second photo the stones look fine, can youquickly grind/sand the high spots on the other walls to reduce the coarseness instead of making
all new patters and molds?
That just leaves the question of how best to cut the walls without dulling your saw.
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Frank Palmer
Fireman
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Posted - 12/07/2020 : 09:32:05 AM
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As Thomas Edison once said, "I've learned 5,000 ways NOT to make a light bulb".
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desertdrover
Engineer
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Posted - 12/07/2020 : 11:18:59 AM
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Bernd, those air bubble holes can all be deleted by building a vibrating table. All my wall molds were filled with plaster, then vibrated for a short time to raise all the bubbles to the top, and out of the mold.
There are many Google simple vibrating tables that can be made. Just placing a hand held vibrator next to your mold will get ride of the bubbles.
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Louis
Pacific Northwest Logging in the East Coast
Post count: 5000 posts added to below count.
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Bernd
Fireman
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Posted - 12/07/2020 : 2:22:38 PM
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Okay, lets see if I can answer everybody's post.
Carl B said:
quote:
Reporting failures is very helpful to everyone Bernd. I share the same issues in my own threads. Nobody's perfect.
dental stone will be used for the final castings of the wall
And that's precisely where you need the strength!
And here I thought I was perfect.  Darn. I sure hope those failures will help.
So it'll be a while before I report on using that material.
thayer said:
quote:
Bernd, I believe by actual stone, he means it has gone back to its previous physical state. Plaster of Paris could also be considered stone once it cures, as it is simply gypsum that has been ground up and heated to drive off the water. Adding water allows it to crystalize again, returning to its "rock" state. Different processing techniques and conditions give different results, thus the variation between PoP, Hydrocal, Dental Stone, etc. It is definitely harder than PoP when cured though, and given all the additional work you are using to build out your patterns, I would also use a softer product. The other good news is that PoP is less expensive than most other options.
Yes, I understand what is going on here. In Bruce Hirst's #3 Comparing Dental Stone to Plastic (resin) he mentions how hard dental stone actually is. So I figured that the steel saw blade would dull very fast. From last nights pour of Hydrocal, it will look like I'll be using that for my blocks.
Bill said:
quote:
Bernd, a couple thoughts
The holes from the bubbles can easily be filled with a variety of stuff you probably have around.
In the second photo the stones look fine, can youquickly grind/sand the high spots on the other walls to reduce the coarseness instead of making
all new patters and molds?
That just leaves the question of how best to cut the walls without dulling your saw.
Welcome to the conversation Bill.
That mold in the second picture was hastily mixed and poured. I didn't care much about having bubbles show as I wanted to compare the blocks from the mold in the first picture on this page with mold in the second picture. I like the contour of that second mold picture. Not as rough. Sanding/grinding down the other casting would leave scratch marks on the surface, so that would be a no go. If you go back a few pages you'll not I made six RTV molds to try out different textures of rock. Looks like right now I'll be making more casting of the mold in the second picture.
Frank said:
quote:
As Thomas Edison once said, "I've learned 5,000 ways NOT to make a light bulb".
I should have a lower number on how not to pour molds. Thomas Edison didn't have access to the internet to tell him how it's done or a fine bunch modelers helping out with their thoughts. 
desertdrover said:
quote:
Bernd, those air bubble holes can all be deleted by building a vibrating table. All my wall molds were filled with plaster, then vibrated for a short time to raise all the bubbles to the top, and out of the mold.
There are many Google simple vibrating tables that can be made. Just placing a hand held vibrator next to your mold will get ride of the bubbles.
Yes, know about vibrating tables. Looks like I need to build one for the final castings. I did try my orbiting sander and a rubber mallet. Trouble was I couldn't find then in time to use on this casting. It had already started to set up. My main interest was in seeing what the block would look like from this mold. I will be using the two molds for these blocks to build the master pattern.
So the next step is to build a vibrating table as Louis suggested. Looks like I'm narrowing this casting process down to where I might get some good castings. I know if I ask now if anybody wants some castings made when I'm done with this project, many hands will go up. Just hang for a while and we'll see what can be done.
Oh, if I slack off to long on this project by not posting any updates please somebody come and kick me in the behind.
Bernd
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| New York, Vermont & Northern Rwy. - Route of the Black Diamonds |
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Country: USA
| Posts: 3968 |
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Pennman
Fireman
Premium Member
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Posted - 12/07/2020 : 2:53:41 PM
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"please somebody come and kick me in the behind"
Originally quoted by Bernd...
OK, I'll kick you now !! LOL
Why don't you try a 2/1 mix for any of the hydrocal powders? I was told to use 2/1 by several casters using these products, and it works. I used 2 (7ounce) plastic cups, with a line drawn where I filled both cups with powder up to their lines and another (1) 7 ounce plastic cup with a line drawn at the same height of the other two cups. You want volume -(not weight of powder and water)
Pour the same way as previously, powder to water. Wait about 60 seconds until the powder settles in the mixing bowl, (without any stirring yet). Note: (A mixing "bowl" I use is a flat-bottomed container, rather than a round bowl) Then, stir, but do it slowly so not to induce in any bubbles. You want this mix to be the consistency of pancake batter, but on the "thinner side" rather than thick.
Do Not let this mixture sit after stirring as it will soon harden. (To help with any bubbles, you can slam the container down on your workbench, being careful not to spill its contents, and then pour your molds.
I had a difficult time doing molds this way, at first, but since then, I have been pouring consistent molds and getting good results. Another tip is to clean all of your molds prior to re-pouring them without leaving any residue of hydrocal or plaster in them. I usually soak them in a bucket of warm water, shake out the excess water, let them dry for a few minutes, spray them with a fine mist of wet water, then pour again. I hope this method is one you will try. Sorry for no pictures, but I think you can follow what is written to get a great product. Just try it. Good luck,
Rich
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Bernd
Fireman
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Posted - 12/08/2020 : 10:56:47 AM
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Rich,
Advice taken. Thanks. Working on a tool right now. Hint:read Louis' post.
Bernd
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| New York, Vermont & Northern Rwy. - Route of the Black Diamonds |
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Country: USA
| Posts: 3968 |
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Bernd
Fireman
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Posted - 12/10/2020 : 4:00:34 PM
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I built a vibrating table like Louis has suggested. You'll find it here. Follow this link:http://www.railroad-line.com/forum/topic.asp?TOPIC_ID=53410
I've provided a link to find your way back here.
Bernd
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| New York, Vermont & Northern Rwy. - Route of the Black Diamonds |
Edited by - Bernd on 12/12/2020 4:12:01 PM |
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Country: USA
| Posts: 3968 |
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Bernd
Fireman
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Posted - 12/12/2020 : 4:05:25 PM
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I posted an update of a product I used for the walls. It can be found in RED PRINT on page 1.
Bernd
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| New York, Vermont & Northern Rwy. - Route of the Black Diamonds |
Edited by - Bernd on 12/12/2020 4:06:35 PM |
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Country: USA
| Posts: 3968 |
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Bernd
Fireman
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Posted - 12/13/2020 : 2:18:45 PM
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Since I couldn't find a proper sub-forum to put this I thought I mention it here since it sort of pertains to the rock crusher build. I had been looking for a more real looking and feeling gravel to run through what will be my animated rock crusher building. Some where I read about aquarium sand. So this past week when the wife and I went for a quick run to the grocery store and we stopped at the Country Max Store to buy food for our birdies and Chippy, the resident but shy chipmunk. I browsed through the fish section and found the sand. They had three colors on display and I got a bag of each, white, beige, and black.
The black would be perfect for coal loads or coal scattered around where ever coal is used. I placed a penny in the sand to give a perspective of size.
I don't know where the white would come in handy.
The beige is close to what I was looking for. Still not quite what crushed limestone would look like. Limestone is more of a light gray.
And the bag it comes in for those that might want to try some out. At $3.49 for five pounds, I think it's cheaper than HO ballast.
Bernd
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| New York, Vermont & Northern Rwy. - Route of the Black Diamonds |
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Country: USA
| Posts: 3968 |
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Frank Palmer
Fireman
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Posted - 12/14/2020 : 09:51:47 AM
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It's amazing what you can find in bulk outside the hobby for much less.
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Country: USA
| Posts: 6134 |
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Bernd
Fireman
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Posted - 12/14/2020 : 10:30:23 AM
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quote:
Originally posted by Frank Palmer
It's amazing what you can find in bulk outside the hobby for much less.
I've always wondered about using aquarium sand when I was at one of the stores that also sold fish and fish tanks. I then read some where somebody suggested aquarium sand, so I finally picked some up. Might not work for ballast in HO because I think it's a bit to big, but for car loads I think it's ideal. A long time ago I used canary gravel. Odd name but it was used for the birds to eat and help with digesting food. It was the perfect color for limestone. Can't find it any more. I've looked and search the net.
They always say to look outside the box. That's what I'm doing. I think they call it cross pollination.
Bernd
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| New York, Vermont & Northern Rwy. - Route of the Black Diamonds |
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Country: USA
| Posts: 3968 |
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