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Bernd
Fireman



Posted - 12/10/2020 :  4:07:13 PM  Show Profile  Visit Bernd's Homepage  Reply with Quote
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
New York, Vermont & Northern Rwy. - Route of the Black Diamonds

Country: USA | Posts: 3894

BurleyJim
Fireman

Premium Member


Posted - 12/10/2020 :  6:02:56 PM  Show Profile  Reply with Quote
I see we go both go to the same tailor. How about grinding down the short end of the prop right to the center hub?

Jim


Take the red pill

Country: USA | Posts: 6027 Go to Top of Page

Carl B
Fireman

Premium Member

Posted - 12/10/2020 :  6:09:25 PM  Show Profile  Reply with Quote
Good old fashioned American ingenuity right here, Bernd.

Using whatever you got, make it work, buy only what you need, and give it a go. Bravo.



Country: USA | Posts: 4077 Go to Top of Page

Bernd
Fireman



Posted - 12/10/2020 :  6:31:06 PM  Show Profile  Visit Bernd's Homepage  Reply with Quote
quote:
Originally posted by BurleyJim

I see we go both go to the same tailor. How about grinding down the short end of the prop right to the center hub?

Jim




I added some more weight to the longer side of the prop. Never thought of cutting off the shorter side. Thanks Jim.

Bernd


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

Country: USA | Posts: 3894 Go to Top of Page

Bernd
Fireman



Posted - 12/10/2020 :  6:32:58 PM  Show Profile  Visit Bernd's Homepage  Reply with Quote
quote:
Originally posted by Carl B

Good old fashioned American ingenuity right here, Bernd.

Using whatever you got, make it work, buy only what you need, and give it a go. Bravo.



Thanks Carl. I now know why I have so much crap laying around. I can't throw nothing away because I might need it someday.

Bernd


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

Country: USA | Posts: 3894 Go to Top of Page

Bernd
Fireman



Posted - 12/10/2020 :  6:33:47 PM  Show Profile  Visit Bernd's Homepage  Reply with Quote
quote:
Originally posted by Carl B

Good old fashioned American ingenuity right here, Bernd.

Using whatever you got, make it work, buy only what you need, and give it a go. Bravo.



Thanks Carl. I now know why I have so much crap laying around. I can't throw nothing away because I might need it someday.

Bernd


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

Country: USA | Posts: 3894 Go to Top of Page

k9wrangler
Engineer



Posted - 12/10/2020 :  7:26:25 PM  Show Profile  Reply with Quote
Looking forward to the report from the shakedown cruise it appears to have a real professional Vibe to it

What else is shaking in your workshop?


Karl Scribner
Sunfield Twp. Michigan
H.M.F.I.C
Kentucky Southern Railway
The Spartan Line

Edited by - k9wrangler on 12/10/2020 7:27:34 PM

Country: USA | Posts: 11769 Go to Top of Page

Ensign
Fireman

Posted - 12/10/2020 :  7:50:04 PM  Show Profile  Reply with Quote
Bernd, my Scottish ancestors would be proud of you laddy!
Making something from the wee bits you have laying around, into something useful.
Looks like your now ready to shake rattle & mold!

Greg Shinnie



Country: Canada | Posts: 8932 Go to Top of Page

tloc
Fireman

Premium Member


Posted - 12/10/2020 :  8:01:18 PM  Show Profile  Reply with Quote
Karl and Greg have me laughing, but I am intrigued that this will work for you. Have fun!

TomO



Country: USA | Posts: 4202 Go to Top of Page

brownbr
Fireman

Premium Member

Posted - 12/11/2020 :  07:59:43 AM  Show Profile  Reply with Quote
Very inventive.


Country: USA | Posts: 1543 Go to Top of Page

BJL0825
New Hire

Posted - 12/11/2020 :  11:30:17 AM  Show Profile  Reply with Quote
Wow, almost to much thinking going on there. With all that space between layers and the springs, I would expect plaster to be flying all over the shop on your first test.

Why not just use a sander without sand paper on the table to vibrate the molds. Don't need a huge amount of vibration to remove trapped air bubbles.

Some say just tap on the table and that will remove the air. Really fine details it might be better to have the faster vibration.

Oh to see the first test of those big molds.



Bob

Country: USA | Posts: 27 Go to Top of Page

nortonw
Section Hand



Posted - 12/11/2020 :  11:46:03 AM  Show Profile  Reply with Quote
Bob has a great idea there. Strap an orbital sander to the lower piece of your table and turn it in. Should vibrate quite well. No external power supply needed.

Norton

The V & T lives in my garage (soon)

Country: USA | Posts: 92 Go to Top of Page

Bernd
Fireman



Posted - 12/11/2020 :  12:54:06 PM  Show Profile  Visit Bernd's Homepage  Reply with Quote
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


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

Country: USA | Posts: 3894 Go to Top of Page

k9wrangler
Engineer



Posted - 12/11/2020 :  1:10:11 PM  Show Profile  Reply with Quote
Just let us know what bubbles to the surface. Iím sure youíll find a solution.

Karl Scribner
Sunfield Twp. Michigan
H.M.F.I.C
Kentucky Southern Railway
The Spartan Line

Country: USA | Posts: 11769 Go to Top of Page

nortonw
Section Hand



Posted - 12/11/2020 :  2:59:27 PM  Show Profile  Reply with Quote
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...


Norton

The V & T lives in my garage (soon)

Country: USA | Posts: 92 Go to Top of Page

BurleyJim
Fireman

Premium Member


Posted - 12/11/2020 :  3:09:46 PM  Show Profile  Reply with 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



Take the red pill

Country: USA | Posts: 6027 Go to Top of Page
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