Stone Buildings

[fsmcollector67]

Roger,
You should not need to seal the stone prior to pouring in the RTV. I just finished reading an article from a 2003 Model Railroader, and it was never mentioned. It did state that mold release was needed when pouring into the RTV mold. I would have concern about the deep wider cracks between some stones. I would think about filing those part way with white glue, or you might have a tough time getting the mold off.
Loren...

[postalkarl]

Hi Roger:

Very nicely done so far. Can't wait to see it all come together.

Karl

[Jerry]

Roger

Beautiful job.  You must have the patience of a saint!

Jerry

[Mkrailway]

Sealing the stone or not? It comes down to how much detail you would want to reproduce. Unsealed with attempt to reproduce every single detail, pour and crack and when you de-mold you will have silicone left in the master to pick out. If you seal the smallest of holes will be smoothed out and the casting children will be less rough and silicone will re-produce more accurately for subsequent castings. The undercuts, etc are the worst things in damaging your silicone, so fill them in.

Good luck.

[Graffen]

I've never sealed plaster before pouring silicone.
Very nice work btw! 

[Random]

So, no sealing seems to have won.   

I needed to make sure these wall sections would interconnect.  So I built a jig to check the finger stones.

This is built from the same strip wood used for the frames in which I made the plaster "sticks" to make the blocks.




These small gaps leave room for the glue between blocks.  These fit together so any wall that fits them should.




This wall section fits on the right but the left side is off.




After a bit of trimming the wall section now fits.




The first set of walls have all been adjusted to match the jig.  We have the freight door, window without the arch, window with the arch, and two spacer wall sections.  These will allow raising the foundation or adding additional space vertically between sections.

[Random]

And, one more section finished.  This is the entry door for street level and the platform level (or wherever else one might need an entry door).





I wanted to put a window in the upper arched opening but I could not find a window commercially available that matched the doors.  So I decided to build the casting with an open frame.  It can be filled with a bit of siding to make a wood panel or glazed for a window.  Hopefully the beam will cast ok.  If it proves problematic I'll add a thin panel to fill the arch in the casting.




I still need to make a blank wall section and I'm considering a section with a single door and small windows as a warehouse side entrance.

That's it for now,

Cheers!

[Random]

There comes a point when you must dive in and give it a try.  So here we go with the first attempt of making a mold.

Parts mounted in the mold box. 




And the molding compound poured in place.  I agitated the forms to try to work bubbles to the surface.  Hopefully they migrated away from the parts at least.  We shall see tomorrow.




What was it Admiral Kirk told Saavik?  "We learn by doing."


Cheers!

[Random]

Hey! Whaddayaknow?  it worked. 




I need to get a better coating of mold release on the sides of the masters.  There were a few spots were plaster pulled off and went with the mold.  Also, the canopy glue I used to build the masters is a positive and a negative.  Because it remains flexible a few bricks pulled off.  But this flexibility allowed the masters to flex a bit as I removed the mold.  The four row wall section on the left broke along a prior break that had been re-glued.  I suspect this happened because I was a little over aggressive pulling that bit loose.  I'll need to do some trimming of the deeper fingers in the mold before casting a copy.   

Overall I'm pleased.

[fsmcollector67]

Roger,
Looking good so far......
Loren...

[Random]

As the test went well its time to get busy.  I set up all six completed masters so that I could pour molds.  Two of these were done in the test.  I want at least 2 molds of each wall to speed production.





The mold making kit I bought has just the right amount for 4 of these molds.  So I used the remaining half from the test batch and a second kit.  Lego, not just for kids.





Hopefully the morning brings good news.

Cheers!

[postalkarl]

Hi Roger:

What can I say but WOW!!! Very nicely done so far.

Karl

[donatode]

[Random]

Thanks Karl.


Things are a bit explody this morning.  I suspect I did not get enough mold release on the masters.  I'll be spending some time repairing them.




But it does appear the molds came out ok. They need some cleanup before I try my first castings.





Cheers!

[Random]

I've completed two molds of each master.   I don't think I'll try to repair the masters again. I think I'll try to turn a copy into the new master.  That said, here's the set.





I'm making batches of castings with regularity.   The parts with the narrow bits tend to break when they are removed from the mold but they are easily glued together.  I think there is opportunity to create some solid connectors that would sit behind the door castings.  That is something to consider as I turn some good copies into new masters.




I picked two castings to clean up and fit together.  These are the left and right warehouse door castings. Note the off center nature of the doors.  There are one and a half blocks to the left of the left door and one and a half blocks to the right of the right door with only one block to the center.  When fitted together this gives a separation of one and a half blocks between the door.   As long as you add on with the correct casting this spacing can be maintained throughout the wall.   The connection inside the doorway is due to overfilling the mold.





These walls will let me build the station and a warehouse building.   I still need to make a full height blank wall and the office side door but I needed a break from building masters.

More to come.

Cheers!