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T O P I C    R E V I E W
Bernd Posted - 12/10/2020 : 4:07:13 PM
At the start of the roundhouse project when I started to cast the first walls that are going to be used for building the master pattern for the roundhouse walls I discovered I was going to need something to remove bubbles from the castings. Louis made a good suggestion that I build a vibrating casting table. I did as he suggested and searched the Tube. Found some interesting setups. I took the idea of one I liked and modified it to the size I needed.

So lets get started. First you'll need a motor that will vibrate when something on the shaft is offset from center. I had the perfect motors. Back many years ago I got very interested in building model air boats. Both gas powered and electric powered. I started to build an electric one to retrieve the gas powered one when the engine quit. I didn't get to far before I lost interest and went back to model railroading. Anyway I had started to build the electric powered one with twin 12 volt electric motors. I got as far as building a frame work to mount the motors and two pontoons to support the batteries and motors. The first picture shows what's left.



The motors are out of one of those little plastic cars that kids first learn how to drive with. They have two motors a bunch of plastic gears, a charger and two 6 volt battery's. I think this is how they get two speeds out of the vehicle. I happen to be two driveways up from the towns transfer station. The guy that is there on duty is my neighbor and allows me to bring back any purchase I don't deem keepable. The motors are quite powerful and run at a fairly high rpm.



Before mounting the motor to the table I needed to find a power supply. The computer power supply didn't like the motor at all. It would start but the power supply would shut down. One of two things happening here, either to much amperage ebing pulled or way to noisy (electrical spikes back feeding into the supply). The old train transformer worked okay but would would also pop the circuit breaker. I lubed up the bearings a bit and the supply seems to be able to handle the motor at around 9 to 10 volts.



when I had built the motor pods I used some PVC piping I bored out to the motors outer diameter. The motor is a tight slip fit. I did that so I could pull the motor out without having to unscrew it from the frame. Also the hold down band didn't squeeze on the OD of the motor.



In order to get a vibration out of the motor I took one of the blades and dismembered it.



The motor was mounted on one to the plates. I purchased two sets of four springs that I thought would work. The set on the right have a larger diameter wire to make the spring a bit sturdier. I turn four pieces of square wood to the ID of the springs for a snug fit. At this stage of the project I couldn't find the dowel I knew I had hid somewhere.



The turned pieces were glued and screw to the bottom of the table.



By the time I got around to doing the bottom part of the vibrating table I had found my dowel. Here I'm marking where the round dowels will get glued to. I was going to drill a pilot hole and also screw the dowels down but found it wouldn't be necessary.



Waiting foe the glue to dry so I can take the table for spin.....ah vibrate.



And the finished tool. Works quite well except it doesn't vibrate enough. I'm going to have to add more weight to one side of the abused prop to give it a bit more vibration or make something on the lathe. That's still up in the air. I tried a casting last night and it still had some bubbles in it but not like before.



I'm going to try some Hydrocal tonight mixed like Rich (Pennman) had said to try.

Click here to take you back to the thread that brought you here. http://www.railroad-line.com/forum/topic.asp?TOPIC_ID=52392&whichpage=10
15   L A T E S T    R E P L I E S    (Newest First)
George D Posted - 01/07/2021 : 10:19:37 AM
I like the three legged solution, Bernd.

George
Bernd Posted - 01/07/2021 : 10:14:21 AM
quote:
Originally posted by Frank Palmer


Bernd, man you are the Goldbergest guy I know. What a work shop.



Thanks Frank.

I got that from my dad. He was a DYI'er. I picked up that DNA.

Bernd
Frank Palmer Posted - 01/06/2021 : 6:55:07 PM

Bernd, man you are the Goldbergest guy I know. What a work shop.
Bernd Posted - 01/06/2021 : 5:41:42 PM
I made a slight improvement to the shaker table. Every time I set something on to shake the bubbles out, the material would shift to one side of the mold. I had to put a shim under one side. After not finding that same shim the next time I needed it I decided it was time for a slight improvement of the table so this is Ver.1.1. Now I can adjust the level both ways by just turning the wing nut.

The parts for one adjustable leg. 3/8" bolt, two washers, one nut and one wing nut.



The sequence of the assembled leg.



The top side with the legs installed.



The bottom side.



Everybody understand the three leg principle of support so you get no rocking? Four legs would be to hard to adjust the level. Remember the three legged milking stool? Same idea. Except your not milking a cow.

Bernd
Philip Posted - 12/13/2020 : 11:19:28 PM
hit em with warm soapy warm water and your pesky bubbles will vanish. Surface tension.

Philip
Bernd Posted - 12/13/2020 : 11:53:37 AM
quote:
Originally posted by deemery

It depends a lot on how much texture you want in 'rough stone'. Russ Greene (NE Brownstone) said one approach is to hold an X-Acto Knife nearly perpendicular to the surface, and then drag it across a strip of 'rock' to get the blade to chatter. I've tried that, it takes practice but the results are pretty good!

dave



Thanks Dave. Interesting method to try.

Bernd
deemery Posted - 12/13/2020 : 10:47:52 AM
It depends a lot on how much texture you want in 'rough stone'. Russ Greene (NE Brownstone) said one approach is to hold an X-Acto Knife nearly perpendicular to the surface, and then drag it across a strip of 'rock' to get the blade to chatter. I've tried that, it takes practice but the results are pretty good!

dave
Bernd Posted - 12/12/2020 : 8:26:33 PM
quote:
Originally posted by dave1905

Have you considered casting them out of resin? You could make them thinner, they would be tougher and wouldn't chip.



The walls I'm casting now are a source of individual blocks. Thickness does not matter here. I'm using the individual blocks to build a master wall for the roundhouse. I will be using one of the dental stone powders for the final walls. Also remember I can make walls thinner because I don't have to ship them to a customer and hope they don't break during shipment.

I think people are having a hard time figuring out what I'm doing. All I need these walls for is a source of rough faced blocks. I basically have to make my own building blocks. Unfortunately I don't know how the rough surface is made on blocks as small as on these patterns or I would have started out that way.

Bernd
dave1905 Posted - 12/12/2020 : 5:58:54 PM
Have you considered casting them out of resin? You could make them thinner, they would be tougher and wouldn't chip.
Bernd Posted - 12/11/2020 : 4:23:06 PM
You guys are a riot to converse with. I just got back from the grocery store with a 12 pack of that Japanese beer, Yuengling. Raise your hand if I got ya! And a bottle of dishwater rinse. If I drink all 12 at once itíll give a new meaning to that bottle of rinse. Can you say ďrinsedĒ. Iím going to give that a try tonight, the rinse that is.



Karl said:
quote:
Just let us know what bubbles to the surface. Iím sure youíll find a solution.


If I drink all 12 bottles tonight Iíll be the one bubbling to the surface. I might just have to have Pennman come up and mix the Hydrocal for me.

Norton pontificated:

quote:
Have you thought about what direction the vibrations might work better? Horizontal? Vertical? Combination?


Yes I did, right after I got back from the store I was looking at the whole Rube Goldberg design and wondered that too. Right now Iím too lazy to mount the motor horiztonally.

quote:
Have you thought about whether the frequency or amplitude of the vibrations might get you better results.


Now weíre getting into the esoteric end of this subject. My take is if I vary the speed of the motor I think I would be varying both the frequency and amplitude. I did notice at a certain rpm the table vibrated more.

quote:
Along with those, does the duration of the applied vibrations make a difference in the results?


If what I said above is true then yes there was a difference.

quote:
Do you own stock in your casting material's company?


No, but do you want to buy some?

quote:
Inquiring minds want to know...


Itís four oíclock and my mind is turning to mush, so youíll have to wait a millennium or two or until I finish my 12th beer. I should be pretty coherent by then, not.

Jim asked:

quote:
Bernd,

Are you going to coat the finished wall with a sealer or paint? The bubbles..."a blind man will never see them". on the other hand, the pieces that got pulled during the release process are different. I've used CRC 03300, with good luck on fibreglass body panel repairs. The paint on types left ridges and 'whoopdees' (It's a body shop term) It doesn't take a lot, just a thin coat. Prices are all over the place, here are some others.

https://www.google.com/search?client=firefox-b-1-d&q=crc+03300

Jim


Once I get the master pattern made I was thinking of spraying it with a matte gloss so the RTV wonít seep into the porous material of the Hydrocal. As far as the mold release stuff, looking at the contents they all seem to be of similar ingredients.

Okay, to wrap this discussion up. Iíd like to thank all of you for putting forth your ideas in a fun way. I think by the time we get done with this project we will be able to handle the matrix of question anybody has on casting almost anything.

I have several observations with the casting process. I think I still mix it too fast and create too many bubbles. The vibe-table isnít doing its job properly and the Hydrocal, plaster of Paris and even the Durham water putty is quite thick, even in a pancake consistency. I'm afraid if I make it to watery the cast medium will loose it's strength and crumble like my first two casting I made.

I have more experimentation to perform, but only after the 12th bottle.

Bernd
Ensign Posted - 12/11/2020 : 4:01:42 PM
Bernd, those wall castings that you made look pretty darn good to me.
If you hadn't pointed out the tiny deficiencies in them I would not have really noticed them.
I'm not certain on how fast your modified propeller spins around, but I'd be worried that your zip tied nuts might go flying off!
Perhaps drilling a hole into what's left of that blade, so that you could feed the zip tie into the hole instead of just around the blade would be a little more safe.

Greg Shinnie
BurleyJim Posted - 12/11/2020 : 3:09:46 PM
Bernd,

Are you going to coat the finished wall with a sealer or paint? The bubbles..."a blind man will never see them". on the other hand, the pieces that got pulled during the release process are different. I've used CRC 03300, with good luck on fibreglass body panel repairs. The paint on types left ridges and 'whoopdees' (It's a body shop term) It doesn't take a lot, just a thin coat. Prices are all over the place, here are some others.

https://www.google.com/search?client=firefox-b-1-d&q=crc+03300

Jim

nortonw Posted - 12/11/2020 : 2:59:27 PM
Bernd,

Let me add some more things to make your head hurt.

Have you thought about what direction the vibrations might work better? Horizontal? Vertical? Combination?

Have you thought about whether the frequency or amplitude of the vibrations might get you better results.

Along with those, does the duration of the applied vibrations make a difference in the results?

Do you own stock in your casting material's company?

Inquiring minds want to know...
k9wrangler Posted - 12/11/2020 : 1:10:11 PM
Just let us know what bubbles to the surface. Iím sure youíll find a solution.
Bernd Posted - 12/11/2020 : 12:54:06 PM
Okay fellow forum followers here's what's shaken.

I followed Pennman's suggestion of a 2 to 1 mix. The hydrocal was of a nice pancake batter consistency. I tried my best not to get any bubbles in the mix. But they did happen. So I waited for a bit for them to come to the surface. After about a minuet I poured the Hydrocal into the molds and turned on the vibrating table. Not much action action of the bubbles raising to the surface. I let the motor run for quite sometime. This morning I demolded the two castings. A close inspection showed bubbles. Hard to see in the picture so I added black circles for bubbles and red where some of the finer mold detail got pulled off the mold.



I increased the weight on the one side of the prop by adding 3 more nuts and cut off the remaining part of the prop on the opposite side. Much more action.



I'm trying to solve the bubble problem here and can think of a couple of solutions. Now, I did clean the mold by washing it in warm water to get any plaster residue out and sprayed it with mold release. I'm going to try what Bruce Hirst suggests in his video of casting dental stone. He talks about using dishwasher rinse agent. I put the link here so you don't have to go back to my other thread. If your impatient click at about the 1:30 mark. That's where he shows the bottle of rinse.

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

So as I walk over shaky ground on making castings, more experimenting is going to happen.

Now lets see if I can comment on some of the questions, suggestions and comments.

So Karl goes first. As you can see the shakedown cruise didn't quite shake the bubbles out. Nothing shaking at the moment.


Greg is next. Glad your ancestors would approve of my using of the "wee bits". Problem is some are so wee I can't find them.

TomO is next. It's always fun working with a bunch of comedians.

Okay Bob, your turn. I sometimes get a headache thinking to much. The table really doesn't shake that much when the molds are on there. I tried an orbital sander, it didn't vibrate enough, plus it was hard to hold the board and mold in one hand. I might try the orbital snader again now that I have the table built. Also tried just tapping with a rubber mallet from the bottom. Did get some results. Again befor the table was built. The picture above is the first molds done with Hydrocal. I did two previously using Plaster of Paris and Durham water putty.

And Norton. See answer above.

Thanks for all the fun and helpful comments. Here's the shake down. I'm going to go with using Hydrocal for the two molds of the large wall. I still haven't poured a casting of the smaller stones of the other two molds. Once I get the bubble problem solved I'll give the smaller stone molds a try.

That's it for now. I got to shake a leg and get some dishwasher rinse.

Bernd

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