Resin casting a freight car?

Yes, the silicone would stick to the raw wood I believe. So some type of sealer would be best. Maybe finish the panel and seal it before making a mold. You may get the imprints of the lettering if they were applied. You'll be surprised how well details will transfer. Trapped air is always the culprit though. So pour the silicone out onto the panel like the product videos show on U-tube.

brr posted:

 

I'm wondering if it's possible to build one side and use it to make a silicone mold which I would then use to make resin car sides?

Yes, absolutely.

Can a mold be made from scribed wood such as shown above?

Yes, absolutely.

If so, should it be clear coated?

Yes, absolutely. I have generally just painted the car side using Polly Scale and let it dry for several days before using it as a master to make an RTV mold.  Whatever you use to seal the wood, and yes you need to seal a wood master, just make very sure that the paint/sealer is completely dry.  Having traces interact with the RTV cure is a great way to ruin your day and probably the master as well.

Never done anything like this, but a recent article in MRC got me thinking that resin may be easier than building 12 carsides.

It's the right way to go to make 12 identical sides!  Might as well make a mold for the ends and floor as well.

all these are resin cast

Thanks for the replies. Now I know it's possible. 

Making the mold: I've done a little research and found everything from expensive model specific RTV to a tube of silicone pumped into a bowl of soapy water. I like the silicone caulk method because it isn't liquid so I could build up the sides and wouldn't have to make a leak-proof container to hold the mold until dry. On the other hand, seems a bit, well, cheesy. I may try it for the ends just to see how it works.

Resin: Alumilite seems to come up most frequently and people seem to like it, at least on-line, and the price seems reasonable. I'm wondering how thick the resin sides should be? I've built a few resin structure kits, and they seem to be about 1/4" thick. I was hoping for thinner, but perhaps that isn't possible.

Any tips, tricks, or advice would be appreciated. 

I've brushed on one coat of sealer, and will steel wool, clean and apply another coat to the master this afternoon. Hope to start the process late Saturday or Sunday.

I haven't done any casting in a while but I found the Smooth-On products work well.

Google them, you may have a dealer near you.

+1 for Smooth-On products.

When you figure out how to make it work, let me know. I made some heavyweight frames for the old MPC boxcars, but kept having to make a new mold every few tries due to issues unknown.

brr posted:

Making the mold: I've done a little research and found everything from expensive model specific RTV ................

Ok, don't skimp on your mold materials or your resin, but do shop around for best value and for materials that work best for you.  I spent 3-4 years trying different brands before settling on products from Freeman's (Miapoxy) and have been using their products for 6-7 years now - lots of good info and tutorials on their web site.  Just took delivery fo 4 pounds of resin today.

Resin: Alumilite seems to come up most frequently and people seem to like it, at least on-line, and the price seems reasonable. I'm wondering how thick the resin sides should be? I've built a few resin structure kits, and they seem to be about 1/4" thick. I was hoping for thinner, but perhaps that isn't possible.

I still use one specific Alumilite RTV for specific jobs - part of those years shopping around let me learn which RTV to use for what kinds of jobs. 

I do not like the Bragdon or Alumilite resins - too short a working time particularly when pouting larger molds that might have undercuts and a propensity for trapping air bubbles.  Prefer the Freeman's that give me double the working time.

With good resin and a good mold, you can make car side 1/8" think or thereabouts.  You can go thinner but only as thin as your master.

Any tips, tricks, or advice would be appreciated. 

I could spend a hour or 2 on this - I used to give clinics on resin casting (even a hands one...) at NMRA conventions.  One very important bit of advice - do not start trying to do something big and important - make molds and cast little stuff and get a feel for everything that you need to do before putting a valuable 1 of kind master that you spent a lot of time making.

I've brushed on one coat of sealer, and will steel wool, clean and apply another coat to the master this afternoon. Hope to start the process late Saturday or Sunday.

Best of Luck!

Here's a little trolley that is 5 resin parts

!

I can't be of much help here, as I have only done a limited amount of resin casting of small parts such as passenger car doors. But I did come across this article years ago that might help.

Dean

There was a guy named "Big Dawg Originals" making resin (I think) shells, mainly engines (mainly HO but not exclusive to it) ... web site is not responding but was able to find facebook info.   Might contact.

I have not tried making a two sided mold yet. For flat or nearly flat pieces like some freight car sides I have been able to use a simple one piece mold. The simplest way is to put the piece in a container, good side up and pour the molding material over it. The resultant cast will not be an exact copy of the back side but have a good front.

To make an exact duplicate of front and back make a thin container about 1/2" wider or more and fix the object centered in the container. Pour the molding material so it just barely covers the object. After curing cut the top open. 

I make my containers with one side held on with tape, the others glued together. That allows easy removal of the mold and allows the container to be reused in the casting process. Remove the mold when pouring in the resin squeezing it to open it up. After filling place it in the container and tape the remaining side so the mold holds it shape. By having relatively thin sides on the mold it can be pulled apart to help remove the casting. 

Here are some examples.

The cast ones are on the left. They have since been replaced by even thinner ones closer to the brass ones on the right. The casting is flexible and tolerates normal handling without breaking.

Pete

mwb posted:

 

I do not like the Bragdon or Alumilite resins - too short a working time particularly when pouting larger molds that might have undercuts and a propensity for trapping air bubbles. 

 

I haven't had an opportunity to test it, but I've read that if you need a longer working time from Alumilite, you can refrigerate the two halves of the resin before mixing them.

---PCJ

SMOOTH-ON

best product and tech support

located in PENN. I think

RailRide posted:

mwb posted:

 

I do not like the Bragdon or Alumilite resins - too short a working time particularly when pouting larger molds that might have undercuts and a propensity for trapping air bubbles. 

 

I haven't had an opportunity to test it, but I've read that if you need a longer working time from Alumilite, you can refrigerate the two halves of the resin before mixing them.

---PCJ

Ok, maybe, but why not just use a resin that gives you longer to work, and then with that slower cure time also provides a harder resin after it's cured?  Cooling it down almost certainly makes it thicker and harder to pour and get into undercuts and traps bubbles better, too.   Smooth on is where I started a decade ago and while easy to use, just not up to casting the parts I wanted to make then or now with reliability. 

The stuff posted here is amazing work.  I've thought about this area myself but have no prior knowledge, not even sure where one would get it (well here!).  I like seeing that it can be done.  I'd of course strive for a much lower bar of success... but hey, you gotta start someplace...

but hey, you gotta start someplace...

That might be the most critical aspect - you gotta start!  Sitting around gets you nowhere fast. 

I started with an Alumilite starter pack and a similar thing from Bragdon, and just tried stuff fully expecting failures and whatever, but you try stuff, learn stuff, get some basic skills and understanding, and you find out it was never all that hard to begin with..... 

The best Mold making material I have ever used is Repro-Rubber its Expensive but it get every last detail. I made a casting of a small brass whistle once and it got every detail.

Severn posted:

There was a guymaking resin (I think) shells, mainly engines (mainly HO but not exclusive to it) ... web site is not responding but was able to find facebook info.   Might contact.

 

Severn can you please email me at the addy in my profile about this post... thanks! 

PS please see my sig line... then I'll explain my question to you. 

Thanks, Rob. 

Thanks for all the tips and suggestions.

Gave the silicone caulking method a try this morning. It's still not dry, so don't know how successful it will be. I have very low expectations, though. Perhaps I'll be impressed. Doubt it. I'll post the results when I can.

I went ahead and purchased a Alumilite super casting kit. It doesn't appear that Alumilite is prefered from the previous posts, but figure I need to start somewhere, and it was available locally at a nice price. I'll take the advice given above and start with some smaller unimportant projects first.

 I like the Allumilite kit. I think you'll like the experience you'll gain. Work smart, and clean. Time is key. Make your moves count. You'll learn as I am too.

I have had very good luck with materials from MPK Enterprises.

http://hobbysilicone.com/

I use a 2 part polyurethane resin system with 3 minute working time - you can remove the parts in 15 minutes, can make a whole yard full in one night.

Their silicon mold material is great as well, good prices too, and very good service.

Jim

brr posted:

Thanks for all the tips and suggestions.

Gave the silicone caulking method a try this morning. It's still not dry, so don't know how successful it will be. I have very low expectations, though. Perhaps I'll be impressed. Doubt it. I'll post the results when I can.

I went ahead and purchased a Alumilite super casting kit. It doesn't appear that Alumilite is prefered from the previous posts, but figure I need to start somewhere, and it was available locally at a nice price. I'll take the advice given above and start with some smaller unimportant projects first.

One of my first experiments with molding was with silicone caulk, used to replicate one of the end stops of Lionel's MPC-era open autoracks. The silicone...left something to be desired since it's relatively thick.

Since then I use liquid rubber made especially for casting, mostly Castolite Castomold, but only for small parts in open-face molds (most successful was a journal box for an HO scale E-8 for a friend) . The only bugaboo I have with Alumilite is that, I've had two instances where Part B ate through the bottom of it's plastic bottle and leaked over time. I'm looking at one long-expired example of a Part B bottle where a sizable chunk of the cardboard of the starter kit box is permanently stuck to the bottom after it leaked. It's sealed itself, but I'm still debating how exactly to dispose of it.

Moral: Have projects ready to make molds of and start casting before you buy the kit. In my case, the project (K-line-style 2-axle ore cars) vanished when I found enough of them to make a 40-car train and decided I didn't need any more.

---PCJ

The fall back plan when you run out of freight cars to duplicate are buildings. Skyscrapers, industrial warehouses, roundhouses. A three stall roundhouse can become a 20 stall.

Pete

Jim Waterman posted:

I have had very good luck with materials from MPK Enterprises.

http://hobbysilicone.com/

I use a 2 part polyurethane resin system with 3 minute working time - you can remove the parts in 15 minutes, can make a whole yard full in one night.

Their silicon mold material is great as well, good prices too, and very good service.

 

Jim

Jim, thank you for that link, I have been getting my resin in small quantities from Amazon and have been looking for a better source.

david

brr posted:

I went ahead and purchased a Alumilite super casting kit. It doesn't appear that Alumilite is prefered from the previous posts, but figure I need to start somewhere, and it was available locally at a nice price. I'll take the advice given above and start with some smaller unimportant projects first.

Good plan with a good starting point from which you will learn a lot very quickly!

David

What I buy:

MPK70 resin system, 3 minute working time (I bought the 8 lb package recently - $49.95)

2125 green silicon mold material. Very flexible, and seems to be very durable. Picks up amazing detail, and as you know - with this system, no shrinkage.

I use this for the Lee Lines car ends. Make sure you discuss shipping charges with him before paying, his standard calculator prices a little high, and he cut the charge when asked.

Jim

After reading the instructions, this appears to be a little more complex than what I thought it would be a week ago. Not quite as simple as poring some "goop" over the car-side for the mold, then mass producing them.

My master needs some more work, and my idea if using a bread pan as the container for the mold no longer seems as brilliant as it did. Actual working time is also much shorter than I anticipated. I now understand some of the above comments much more clearly.

Should I quit? Probably. Not going to, though. If anything the difficulty may add to the enjoyment. My first Labelle passenger car kit was the same way. Once I figured it out, each car has been better than the last, and I'm even kitbashing the current one. 

brr posted:

After reading the instructions, this appears to be a little more complex than what I thought it would be a week ago. Not quite as simple as poring some "goop" over the car-side for the mold, then mass producing them.

Well, yes....

My master needs some more work, and my idea if using a bread pan as the container for the mold no longer seems as brilliant as it did. Actual working time is also much shorter than I anticipated. I now understand some of the above comments much more clearly.

The quality of the master is critical; I generally build a box out of styrene around the master after I've secured the master to the base (when the master floats off the base, it's just going to be a bad day...) - I like to work on glass - it's flat!  Otherwise, for small parts I'm using 12 oz paper cups that I've cut down, small plastic parts boxes, etc - anything that contains the master and leaves a reasonable amount of room around it (and depth!) to make a mold that will support itself.  I did mention that working time - once mixed, there's no stopping now!  That extra 3 minutes with the Miapoxy resin really makes life a lot calmer, too!

Should I quit? Probably. Not going to, though. If anything the difficulty may add to the enjoyment.

Excellent!  Forge on and conquer!  Beats sitting on your thumb whining "I don't have the skills....",

My first Labelle passenger car kit was the same way. Once I figured it out, each car has been better than the last, and I'm even kitbashing the current one.

If you can build LaBelle pass car kits, resin casting should be a breeze!!!!!!!

Don't quit yet. One of the tricks is to get some uncolored modelling clay to use as the base under your part model, then build a 'dam' around it.  Form it into a flat plank, then use small bits to seal around the edges of your part.

I used some pieces of wood screwed together as the dam, with masking tape around the inside to keep the stuff from leaking out the cracks. The clay can be used for 'caulking' as well. Good videos on Youtube that walk you through the whole process. Definately worth watching before taking the plunge.

Jim

,,,,,some uncolored modelling clay.....

Make sure it's a non-sulfur containing clay - some resins will react with some types of clay.

Most of the resin casting suppliers also do sell clay for this purpose.

Well, here's where I'm at:

Built a box out of a 1x4 and extra paint sticks I had laying around. Applied a couple coats of Krylon crystal clear. The kit comes with 1lb. of clay, so I'll use that to seal it off. Decided it would be best to have removable sides, just in case. I fear it may be a little big, but I'd like the mold to be strong. I built a smaller one for a boxcar door to practice on as well.

I glued a piece of 1/32" basswood to the back of the master for strength and a little more depth. Hoping to tape the master down instead of gluing, but not sure I trust the tape.

Well, the mold is poured:

It's been done for about an hour now. I made some late changes to my plan. I added the door hardware to the master. I figure if I can cast those in it will be a money-saver not having to purchase 2 sets for every car. Not sure if that was a good idea or not. I also decided to build another master. My reasoning being that the kit didn't contain enough RTV to do much practicing. I might get lucky with this and get a good mold the 1st time. If not, and my original master is destoryed, I have a back-up. Then decided to purchase a relatively cheap kitchen scale to get precise measurements for mixing. The price of the project is adding up quickly which I hope to save in building car-sides, but I'm still trying to stick to a bit of a budget right now.

The product:

I think it's been on the shelf for awhile. It took a long time to get the rtv mixed before adding the catalyst. 

I did get air bubbles while mixing and pouring, which seem to dissipate rather quickly. I did tap the frame after pouring for awhile. At the moment there are no air bubbles showing on the surface.

Posting this in real time. By Friday at this time I should know if I have a success or failure. Will post either way. 

brr posted:

<snip>The price of the project is adding up quickly which I hope to save in building car-sides, but I'm still trying to stick to a bit of a budget right now.<snip>

For your first go-around you should expect a high(er) price as the cost of your learning curve. Besides, you are trading price/cost vs the time (and cost) of individually making car sides.

rex desilets posted:

brr posted:

<snip>The price of the project is adding up quickly which I hope to save in building car-sides, but I'm still trying to stick to a bit of a budget right now.<snip>

For your first go-around you should expect a high(er) price as the cost of your learning curve. Besides, you are trading price/cost vs the time (and cost) of individually making car sides.

Hard to put a price and value on what you are learning  through direct experience.

Anchoring the master - I usually work on glass, glue the master to glass, and build a box around it using styrene sealing the corners with interior bracing.  If I can't get it off the glass later, that's ok - I know I can build another if I need to do that.  Beats having it come loose and being embedded in the RTV - that can ruin your day real fast.

If you are worried about bubbles in the RTV -- one of the standards is a vacuum bell, but that's not always practical or even needed.  Take your poured RTV box mold and put it on top of the clothes drier and run it for an hour - vibrations will release the bubbles....

Failure.

While the RTV dried according to plan, some of the door hardware became loose during the process. Other than that, and my attempt to "fix" the mold, the product worked very well. 

Since the mold was going to have to be redone, I decided to go ahead and add resin. Didn't go as well as hoped. The mold wasn't level allowing one side of the car to be thicker than the other. The more disturbing problem was that when removing the resin side, some of the RTV stuck in the scribed siding, thus completely ruining the mold. The instructions stated to use baby powder as a "mold release", but I was concerned with the powder getting stuck in the scribing. Wondering what a good method would be to keep this from happening?

I'm a bit discouraged, but the only thing I can do is keep going. I've already fixed the detail items that were a problem. They are now firmly attached. Wondering wether I should add another coat of sealer over the whole master just to be sure?  As far as the resin goes, I'll make sure the mold is level next time, and will try and come up with something to use as a mold release. I think once a solution is found for these problems this will be a successful endeavor, and/or an interesting learning experience.

Wood is not the best choice for a container. Silicone is easily pulled away from styrene. I have only used Smooth On Oomoo 30 and never had a problem removing the mold.

Pete

Thanks Norton. The container, and even the wood part of the master, isn't a problem. Mold released fine from it, no problems. The bigger problem is the resin releasing from the rtv in the scribed lines. 

I think I've fixed a few of the problems. Can't be sure until I make another mold, but am very optimistic. My biggest concern is keeping the rtv reusable.

2nd mold attempt was 100% successful.

When re-reading the manual, in the very small print at the back, it stated that using a mold release will prolong the life of the mold and make de-molding easier. In normal print the manual states over and over that no mold release is necessary. This time I'm going to err to the side of caution and use a mold release. 

Hopefully tomorrow I'll have some nice car-sides to work on.

Done:

Thanks again for all the help and encouragement!