Freerails Home 

Freerails IS ACCEPTING new Members ... To join Freerails ... See how to Register as a Member in the 'Joining Freerails' Forum

 Moderated by: .  
AuthorPost
ON30Carl
Registered


Joined: Mon Sep 20th, 2010
Location: Pasco, Washington USA
Posts: 136
Status: 
Offline
A while back a built a jig to make a stockcar,the jig works great but stockcars have lots of parts and are not an easy thing to build even with a jig.I thought this is a great candidate for casting and I'm glad I tried it out. I've never cast anything before so this was all trial and error (emphesis on error)I built up the skeleton of the stockcar and the end pieces and glued them to cardstock

I added NBW castings to the frame and boxed it all in for the rubber.I used Alumalite silicone rubber to make the mold and found it very easy to work with. I had no bubbles in my mold and I didn't degass or vibrate the mold. I did run a .025wire around the master after I poured the rubber to insure no bubbles.

The mold:



The resin is a much different animal to work with You get 90 seconds to mix and pour the resin before it begins to set up.It took me 2 tries before I got a satisfactory casting. The first try I poured too much resin into the mold and got too much flash, infact it was more then flash it was a solid wall of resin.



the plastic you see in the above photo is thick and hard and would be too much work to cut and sand down.



 



The pictures above show what I was after and I got that by mixing small amounts of resin at a time and scraping the back of the mold after the pour and before it began to set. By doing this I found you get more working time by mixing small amounts of resin at a time, if you mix a large batch the resin heats up too fast and cures quickly. I next built and cast the roof wich was a bit tricky because of an undercut.





this is the casting of the roof




The roof has some flaws in it, i'm not sure if I'm not getting the resin all the way to the ends or if there is a flaw in the rubber mold. I will keep trying to use it and see whats up.:bang:
Well this is whaI have so far. I will cast the underbody frame but I'm not sure I will cast the floor planks.
Please comment and make suggestions. It will be a while before I get back to this, I'm all out of rubber and resin.

Carl

sledhead
Registered


Joined: Wed Jun 23rd, 2010
Location: Wisconsin USA
Posts: 185
Status: 
Offline
I've heard casting is not an easy skill to master, but once you get down pat the techniques that work for you building multiple models becomes a breeze. Those last two photos really look great! Keep posting updates and what you learn, I really want to try my hand at this when I have time. Right now I'm still trying to master brass etching. Thanks for showing your work!

Herb Kephart
Moderator


Joined: Thu Jul 19th, 2007
Location: Glen Mills, Pennsylvania USA
Posts: 5893
Status: 
Offline
To make perfect castings, you need a way to draw a serious vacuum on the rubber and the resin each step of the way. This ensures that there are no air bubbles in either the rubber, the resin, the rubber filling the pattern, or the resin filling the mold.

If you have an air compressor, try connecting the air INTAKE to a container large enough to contain any of the above. Try to get at least 20 inches of Hg. Vacuum, and what ever you use has to be quick enough to get to that point without taking too much time, as it will cut down on some of the time that you have before the resin goes off.

Another tip-- instead of scraping the top of the mold, try laying a piece of glass over it with a weight on top to get a flat back on the casting.

You are doing very good so far, keep going!

Herb  :old dude:

ON30Carl
Registered


Joined: Mon Sep 20th, 2010
Location: Pasco, Washington USA
Posts: 136
Status: 
Offline
Thanks for the interest guys,

Herb I will try the glass next pour,

at the moment I am fabricating a master

for the undercarriage of the stock car.

I may not get to it for a bit as I am

building bedroom closet in 1:1 scale.

Carl

 

pipopak
Moderator


Joined: Wed Apr 13th, 2011
Location: Florida USA
Posts: 2057
Status: 
Offline
Why on earth are you wasting perfectly good layout money and space in a .... CLOSET???. Show who's boss, throw the clothes away!!!.

Herb Kephart
Moderator


Joined: Thu Jul 19th, 2007
Location: Glen Mills, Pennsylvania USA
Posts: 5893
Status: 
Offline
If you get away with the above, try keeping the resin and catalyst in the freezer, to get more time before it starts to set. Ninety seconds seems awfully quick--what brand of resin are you using? there are lost of varieties out there that will give you a lot more time to work.

Take a look at    http://www.smooth-on.com/


Herb  :old dude:

pipopak
Moderator


Joined: Wed Apr 13th, 2011
Location: Florida USA
Posts: 2057
Status: 
Offline
Also make sure you are mixing the proper quantities and proportions.

ON30Carl
Registered


Joined: Mon Sep 20th, 2010
Location: Pasco, Washington USA
Posts: 136
Status: 
Offline
Good one Pipopak,

I'm asking myself the same question!

A mormon friend of mine has a good quote,

"you don't have to be a bigamist to

have one wife too many".

I have to admit, the wife is very

suportive of my hobby, so hunnydo's

are part of the give and take.

Besides it would cost alot more

if she contracts it out!:doh:

Carl

 

dave1905
Registered
 

Joined: Thu May 26th, 2011
Location:  
Posts: 24
Status: 
Offline
I have found that putting the castings in a pressure chamber minimizes bubbles.

Pressure makes the bubbles smaller so they aren't noticeable. 40 psi ought to minimize most bubbles, 80 psi will make them so small you won't be able to see them.

Shop other places for resin. I like at least a 3 minute set time. I have used Hobby Silicone resin and RTV before.

Herb Kephart
Moderator


Joined: Thu Jul 19th, 2007
Location: Glen Mills, Pennsylvania USA
Posts: 5893
Status: 
Offline
Pressure will indeed make the bubbles smaller--however, you have to keep the pressure on during the whole cure time. Then, if you have a bubble near the surface of the rubber, you will have a bulge in the rubber surface once the pressure is removed.

Once  you pull a good vacuum for a couple SECONDS --ALL IT TAKES--- the bubbles come to the surface and burst--end of bubbles.

Even the amount of suction provided by a shop vac is better than nothing.

Ya pays yer money and ya takes yer choice---


Herb  :old dude:

dave1905
Registered
 

Joined: Thu May 26th, 2011
Location:  
Posts: 24
Status: 
Offline
True that you have to keep the pressure on for the whole cure time, but the cure time for resin is only a couple minutes and much of that is consumed in the pouring the resin and loading it in the pressure chamber.  So really the resin casting only spends about 3-5 minutes in the pressure chamber.

When it comes out I then put the mold in a warming chamber.  It is two tin foil lasagna pans.  I have a clamp on light fixture that shines a flood light through a hole in the top pan on one end.  That's enough to heat the interior of the pans up to 100 degrees or so.   The castings, still in the mold, go from the pressure tank into the warming chamber for 10 minutes or so to fully cure. 

If I am making a couple different castings I alternate molds, preparing one while curing the other so it really doesn't add that much time to the overall process.

pipopak
Moderator


Joined: Wed Apr 13th, 2011
Location: Florida USA
Posts: 2057
Status: 
Offline
Being married to a dentist I got used to dental materials. My preferred casting media is finely ground clear acrylic and solvent. Make my molds out of rubber, fill with powdered acrylic, flood with solvent, add more plastic on top as needed and wait.

dave1905
Registered
 

Joined: Thu May 26th, 2011
Location:  
Posts: 24
Status: 
Offline
Here is a mold frame:



Here is how the 2 frames fit together:



The master in the female frame with the retaining rods in place:



The male and female molds in the frames:


dave1905
Registered
 

Joined: Thu May 26th, 2011
Location:  
Posts: 24
Status: 
Offline
The gons are cast with 4 board high sides and then cut down to 3, 2 or 1 board high to match various prototypes.





The gon and the P&R boxcar in the back are both homemade resin castings.



This class NMa caboose has a cast resin roof on a Bachmann caboose body.


sledhead
Registered


Joined: Wed Jun 23rd, 2010
Location: Wisconsin USA
Posts: 185
Status: 
Offline
Has anyone tried one of these as an air removal device?

http://www.amazon.com/iTouchless-Sealer-Automatic-Vacuum-Container/dp/tech-data/B000N5WJUG

Seems like an inexpensive way to de-air a casting, but it does not specify how much of a vacuum it creates, too little, and the bubbles won't burst, they'll just get larger.

Last edited on Tue Jun 28th, 2011 03:00 pm by sledhead

sledhead
Registered


Joined: Wed Jun 23rd, 2010
Location: Wisconsin USA
Posts: 185
Status: 
Offline
BTW dave, those are some really nice cars. I hope mine turn out as well. Do you cast your own trucks as well?

dave1905
Registered
 

Joined: Thu May 26th, 2011
Location:  
Posts: 24
Status: 
Offline
Thanks.

Nope, I use a mix of MDC, AHM and Tahoe trucks with IM semi-scale code 88 wheelsets.

Last edited on Tue Jun 28th, 2011 06:10 pm by dave1905

ON30Carl
Registered


Joined: Mon Sep 20th, 2010
Location: Pasco, Washington USA
Posts: 136
Status: 
Offline
I like your cars Dave,
I want to try to cast some high side
gon's in the future.
For now I'm stuck in the "CLOSET FROM HELL"
Carl:doh:

pipopak
Moderator


Joined: Wed Apr 13th, 2011
Location: Florida USA
Posts: 2057
Status: 
Offline
sledhead wrote: Has anyone tried one of these as an air removal device?

http://www.amazon.com/iTouchless-Sealer-Automatic-Vacuum-Container/dp/tech-data/B000N5WJUG

Seems like an inexpensive way to de-air a casting, but it does not specify how much of a vacuum it creates, too little, and the bubbles won't burst, they'll just get larger.
This is what I use:
http://www.etoolcart.com/mityvac-brake-bleed-kit-mv8020.aspx
Not top notch but good enough. HIH.

Herb Kephart
Moderator


Joined: Thu Jul 19th, 2007
Location: Glen Mills, Pennsylvania USA
Posts: 5893
Status: 
Offline
Carl wrote-

For now I'm stuck in the "CLOSET FROM HELL"

Hah--you didn't put a doorknob on the inside, I'll bet!



Herb  :old dude:

W C Greene
Moderator


Joined: Fri May 4th, 2007
Location: Royse City, Texas USA
Posts: 8101
Status: 
Offline
While I rarely make molds of stuff, I just want you to know how much I like your old timey equipment..archbar and Fox trucks, truss rods, and HANDLAID track! Modelers of "turn of the century" and earlier are rare as hen's teeth and should be appreciated. Show us some more photos of the layout.
Woodie

CarlOn30
Registered
 

Joined: Mon Oct 31st, 2011
Location:  
Posts: 24
Status: 
Offline
Wow! its been almost a year since this topic

has seen any activity, it would have been longer

but I was clearing space in the hobby room and

I found my little stock car hiding under all kinds of

plans and unfinnished stuf. Looking it over and

you will see in the pics that this first attempt

at casting was a success in at least learning

what not to do and what should have been done.

Don't get me wrong, the mold is something I

can work with and build credible cars, but I

am thinking about building another master

and trying again. Time will tell.

So here are the pictures with the side boards

painted and placed.











I am now attempting to cast trucks for this car,

as I type the resin is curing in a mold and it

needs time to harden. Pictures tonite!

Carl,

Pasco, Wa.

dave1905
Registered
 

Joined: Thu May 26th, 2011
Location:  
Posts: 24
Status: 
Offline
I have found that putting the castings under a floodlamp warms them up slightly and really helps then sections cure quickly and completely. You don't need them hot, just warm.

mabloodhound
Registered


Joined: Mon Apr 5th, 2010
Location: South Shore, Halifax, Massachusetts USA
Posts: 318
Status: 
Offline
sledhead wrote: Has anyone tried one of these as an air removal device?

http://www.amazon.com/iTouchless-Sealer-Automatic-Vacuum-Container/dp/tech-data/B000N5WJUG

Seems like an inexpensive way to de-air a casting, but it does not specify how much of a vacuum it creates, too little, and the bubbles won't burst, they'll just get larger.


I used a Food Saver http://www.amazon.com/FoodSaver-Advanced-Design-Vacuum-Packaging-System/dp/B000AAYD6W/ref=sr_1_4?s=home-garden&ie=UTF8&qid=1338299867&sr=1-4  because we own one and use it to seal canning jars, food bags, etc. and it has separate containers that can also be sealed.
I am new to this and just used it to de-air the RTV and the resin (before pouring).   Worked fine.   I may try it on the actual casting after my new masters get here from Shapeways.
:cool:

ON30Carl
Registered


Joined: Mon Sep 20th, 2010
Location: Pasco, Washington USA
Posts: 136
Status: 
Offline
Going to make a string of stock cars by casting
resin into molds I made many moons ago.
A few pics
Carl

Attachment: IMG_2696.JPG (Downloaded 34 times)

Last edited on Sat Apr 25th, 2015 10:33 pm by ON30Carl

ON30Carl
Registered


Joined: Mon Sep 20th, 2010
Location: Pasco, Washington USA
Posts: 136
Status: 
Offline
More
Carl

Attachment: IMG_2698.JPG (Downloaded 34 times)

Last edited on Sat Apr 25th, 2015 10:33 pm by ON30Carl

ON30Carl
Registered


Joined: Mon Sep 20th, 2010
Location: Pasco, Washington USA
Posts: 136
Status: 
Offline
Another

Attachment: IMG_2699.JPG (Downloaded 34 times)

ON30Carl
Registered


Joined: Mon Sep 20th, 2010
Location: Pasco, Washington USA
Posts: 136
Status: 
Offline
Last one,
floor is individual planks of 2.5"x5" plastic
painted and weathered with acrylic paint
and chalk, followed by an AI wash
Carl
Im torn as to what I want to cover the cars
with but I'm leaning towards corrigated metal.

Attachment: IMG_2700.JPG (Downloaded 34 times)

Last edited on Mon Apr 13th, 2015 03:07 am by ON30Carl

Shoulders
Registered
 

Joined: Tue Nov 26th, 2013
Location: Kent, United Kingdom
Posts: 536
Status: 
Offline
Hi carl

They look great, must have a go at casting one day.

Cheers Dan


UltraBB 1.172 Copyright © 2007-2016 Data 1 Systems