I'm building four logging flat cars (log bunk flat cars) for my Hebard Cypress Company in On30. The master and mold shown above are the basis for the cars.
The log bunks are the brackets on the flat car that hold the logs as shown on the photo above. Essentially it is a timber across the flat car with metal cleats on each end, and a chain for securing the log. My plan is to build two log bunks for each car, or eight all together. I may actually want to build more, so I decided to build a master and mold, then cast all that I need.
This is a wood prototype but I'm using styrene for the master as it slips out of the mold more easily. This mold design will trap air so I'm building it to be pressure cast. The depth of the timber is going to be slightly higher than the prototype so that I can sand it down to the precise size. Pressure casting leaves a "fillet" or raised edge around the casting that needs to be removed.
I cut two identical timbers which are just a tad longer than the width of the flat car frame. The steel cleats on the ends will be made with thin strips of styrene.
The cleats are made each with three pieces of thin styrene. I cut and glue each piece then cut off the extra and file it clean and square.
Using a #72 bit I drill 7 holes, two on each cleat and three across the timber for bolts and washer castings.
Her is a completed piece, on my hand so you can guage its size.
The thre bolt washer castings hold the piece to the frame, and the cleat castings hold the cleat assembly to the timber.
I made two of them so each casting would give me enough for a single car, although on some cars I may use three instead of two for some variety. Logging operations often build their own cars from kits they get from the steel casting manufacturer so there is usually some variance between groups of cars.
The assemblies are glued with white glue to a plast base. The glue is not permanent but hold the timbers in place so the don't move or float in the mold making compound. You can remove them from the base later.
The mold box is made from thin strips of styrene that I buy in large sheets. I cement them with Plastruct styrene cement. This system works great because the styrene is melted and forms a leak proof bond to the other styrene. The star pattern allows the strips to be pealed off quickly. The mold material was mixed as per the directions, poured in and allowed to cure for 24 hours. This is Smooth On Mold Max 40, which is a bit too hard for this kind of mold, but it did work well.
After curing I gently removed the mold dam from the mold rubber and removed the block.
This is why I use the Elmer's Glue. The masters break clean from the base and can be used again.
Carefully I removed the masters from the mold, and trimmed the flashing from the mold. Looks good!
To cast this mold I will heat it in the microwave oven for two minutes to get it warm to the touch but not so hot I can't handle it. This allows the resin to flow in the mold better, and to help release bubbles.
This casting was made without a pressure vessel (pressure pot) that I would normall use. It is still in the mail, but I wanted to get a test shot immediately.
The impression is good and the mold will work. This casting has some critical bubbles in it so that it was rejected, but when I pressure cast it there won't be any bubbles as the 50 PSI pressure squishes the bubbles so small you can't see them.
I love Bar Mills models and have built several of them. Be sure to tune in to First Mondays with Art Fahie and catch up on the latest. I hear we are going to learn more about the soon to be released Stewart's Rods kits! I want one!
We have all built kits of all types, from easy
to advance craftsman types. I would venture to say that about 70% of the
instructions I've seen have been bad or at least missing steps. The Ambroid
(ancient) instructions above come with a nice drawing and steps, but building
this car is far more complicated than it says here. With today's modern
technology there really isn't a good reason to have bad instructions. One
previous kit manufacturer told me it was the hardest part of the business for
him!
So, I poled several groups to find out what they
like in instructions, what they don't like, what they would rather see, and how
they would like them presented. Here is what we found out...
1. Visual instructions and photos are important.
We get lost with long explanations and text, thus causing mistakes. Good pics
are much easier to understand, and our world is becoming more and more visual
each day.
2. Great photos of the finished model. It
certainly helps to know what you are building. It also helps to see the
finished model so you can decide how you want to treat the colors, the weathering,
and the detail parts. Clear, colorful photos from all directions give you what
you need. Often, I've had to go on line to see what someone else did because
there were no kit photos, not even on the box!
3. Digital instructions. Having instructions on
the web, a CD/DVD or a thumb drive can provide many photos and directions
without filling the kit full of paper. It also allows you to enlarge and
manipulate the model. Thumb drives are getting unbelievably cheap and could
easily be included in a kit, though I've never seen this before. We'd like a
kit manufacturer to have an instructions page to selected from. Having
instructions online can also help me decide to buy a kit! Digital instructions
can be updated on the fly, so if there is a problem with a kit or a better
technique (or the paint manufacturer goes out of business) you can make the
change. Digital only will save on the cost of the kit as printing can be expensive,
but I think some customers won't like that. RR Kits has their instructions online.
4. Instructions online. While I prefer
instructions in the kit, I do like online instructions. Maybe for no other
reason than I spilled paint all over my kit copy and I need a backup.
5. Overcomplicated. Some instructions can be
verbose and intimidating or have so many steps that they just aren't fun to
build. Mine Mount Models has clear, easy instructions, written by Ron Klaiss
who is rumored to be one of the best instruction writers.
6. We like a story! The readability of the text
is important. We not only want to know that tab B goes in slot C, but what we
are really building overall. BTS kit instructions have a story like quality,
and can be quite lengthy, but the model will be amazing.
7. Drawings. The drawings need to be in scale
when necessary, especially when building on the plans is expected. This is
common with interior board by board walls, such as seen in FSM kits. Working
off the plan with a scale rule to convert is problematic and a sure way to have
an accident. Nasoj Slidder has seen dotted lines right through small parts where you can't tell if it is "over" or "under". Blurry drawings are a problem too.
8. Text. Folks are saying they like a font that
is easy to read and large enough they don't have to go back and forth with
reading glass while using magnifiers. Do not crowd too much text on a page, and
don't try to save paper, per Jake Johnson. Leave nothing to chance when
explaining because some skill modelers will do fine, but newer modelers may not
understand.
9. Build in order. Skipping steps or jumping
around in the instructions is very difficult to follow and a good excuse for a
mistake. Always write like you are talking to a beginner. Glen Evans suggests
Sierra West for great instructions.
10 Build along events. Matt Savage reminded me
of this and it’s a great idea! I've been part of build-along events online with
the Wiley Scale Model's Overtime at the Bench Podcast. We pick a kit and 16-20
of us buy it and we build a little on it each Monday evening. Great way to
learn new skills and see things differently. Even better the video is captured,
and you can review it before you start your model. Another benefit is that the
kits are bought in large quantities so usually you can get a better price, free
shipping or extra goodies.
11. Bad printing. I know the kit masters want to keep cost down, but printing the instructions is important. The print should be clear, crips and straight. Copies of copies of copies are blurry and messy. Color is always better, but I've never really need it much except for one color print of the finished model.
Observations:
Greg Cassidy says that after he builds a couple of kits from one manufacturer he mostly skims the later kits from the kit company for any oddities, and just plug along withour reading them.
What are your thoughts?
Want to give a good kit maker props for their instructions? What would you like
to see in kit instructions? You can post a comment below, or email scottgperry@comporium.net
As some of you know I've been in the resin casting business off and on for about 25 years. I've recently decided to get back into it under the new business Micro Reproductions. Technology advances all the time, and its no different with casting. New mold materials, more advanced resins, and better machines are making castings better all the time.
1. Warped parts. Nothing is more frustrating than getting a model, like that of a flat car, and the first thing you have to do is to warm the casting and flatten it out. Deformed one-piece car bodies are the worst problem.
2. Air bubbles in the casting. Usually this is mostly an appearance problem with the quality of the model, but it can occur in a problem place where a detail or critical part has to be mounted. Either way they have to be filled and sanded.
3. Poor quality castings. This is a cottage industry, and most castings are made by semi-pro mold builders in their basements. Nothing wrong with this but they don't usually use the proper resins, tools and methods to get the best products.
4. Difficulty Painting. Resins can have an oily finish if the wrong materials are used or release agents are put on the mold and not washed off. Acrylic paints can be difficult to apply, and chipping can result. One great cure for this is casting in color.
5. Poor fit. Resin casting usually contract, mostly around 4%. Getting things to fit accurately is a bit of an art. Some castings are reportedly 1/8th of an inch off! Designing and qualifying the part and mold are critical.
6. Drilling and fitting. Some models require the drilling of many holes for items such as grab irons and hand rails, instead of the hold being cast into the piece.
7. Fragile small parts. Resin parts are reasonably strong if thick enough, but small parts can be brittle and break easily. Changing the resin formula can sometimes fix this.
8. Poor directions. This is common to all types of model kits, not just resin ones. The vast majority of kit makers are not good instruction writers. It is recommended that they outsource this service. Often they don't make reference to the parts in the kit. The photos can be very poor quality as well. Super heavy text pages are very hard to model from.
9. More difficult to build than other kits. Injection molded kits are far easier to build, I agree! But is that because the kit is resin, or because we are using resin to make up for getting a model, we need instead of spending big bucks on an injection mold tool? I do know this; resin models are far more fragile on the layout that plastic models.
10. Resin dust. Resin dust is extremely fine and gets everywhere. Some resin dust is toxic.
11. Too much concentrated detail. Sometimes the detail on one area of a model is so dense that the components are hard to paint and weather. It also prevents customizing. Might be better if the detail was stackable instead of unit cast.
12. General assembly. Resin is difficult to glue together. CA adhesives are common, but the bond is brittle, unlike plastic cement that fused the parts together. I've even used screws to put large pieces together as resin drills and taps nicely. Epoxy is another method, but that has to be mixed in small amounts, stinks, and is messy to use.
The best solution to your parts not falling apart is
cleanliness of the resin castings before assembly. Before any assembly or
painting you must thoroughly clean the parts in warm soapy water and rinse or a
really good wipe down with Alcohol or similar solvent. Most all manufacturers
use a mold release when making the parts and it stays on the model. Paint and
glue do not stick well to mold releases. Same issue with Talc used when making
white metal parts.
13. Not enough new kits coming out. The Covid issue has caused model railroading to explode with new modelers and a surge in building by current modelers. Getting kits is getting more difficult as well since the supply is dwindling due to demand.
14. Part numbering. It can be difficult for someone to figure out which part is which if they are not numbered or identified somehow. The instructions at least need to have clear pictures of the parts for identification. I prefer a page that is nothing but part identification.
Some of the good things about resin kits:
1. It can provide a way to get a model of something that doesn't generate enough interest to mass produce, such as a rail car from a shortline that no one but me has heard of.
2. It build your skill set. They are challenging.
3. They are satisfying to build. Spending your hard earned dollar on kits, you want some fun back! They take time to build, and provide you with a creative outlet.
Other ideas for improvements:
1. DVD or video on line to show how to build the kit
2. Picture based guide instructions
3. Include techniques, tutoring, something extra to help advance the modeler's skills.
What bugs YOU about resin models?? Post your response below, or send me an email to scottgperry@comporium.net.
Expanded Polystyrene XPS Insulation Foam Board - Is It Safe To Use on Model Railroads?
Note: the following is a study I've done only for my self and is not an endorsement or recommendation of any kind. Its information that I'm using to make decisions for myself.
Recently my friend Clark brought up the question about the safety of using XPS when building layouts. The concern is that we commonly use hot wire cuttin tools or heat guns to shape the material sheets. When you do this you get smoke, fumes and odor from the melting. It has been reported that this is toxic, but I wanted to know if that truly was the case. Other rumors are that it offgasses cyanide.
My research shows me that this is not really the case. While the smoke and gases coming off of XPS are considered toxic, in relation to burning wood, plastic and other materials used in building houses it is of less concern that most. The main chemical release is carbon monoxide, which is toxic. However, the limited amount generated by working on a layout is very negligible. There are no other chemicals over trace amounts to be concerned with, and no cyanide.
The biggest cocern with burning XPS is eye irration, and in extreme cases nausea. So the counsel is to do this in a well ventilated area and you should be fine. Cut the foam outdoors if you can, or at least use a fan to prevent eye irritation. Using a heat gun is fine, but do be aware that XPS can burn if ignited.
Copyright ® 2021 Scott G. Perry. All rights reserved.
Duplication and publication are prohibited.
Click on Photos to Enlarge
01 Bachman On30 Flat Car - Out of Production
Buying a Bachman On30 flat car costs over $70 now that
they are out of production (Pic 01). Building a single flat car from scratch is
a tedious and time-consuming project. If your railroad needs a fleet of flat
cars, say one dozen, you are looking at tons of money or tons of time building
the same thing. If you can’t buy the cars you want, you can build one very good
model and replicate it using resin casting techniques. While this appears to be
a difficult process, it really isn’t and its loads of fun to see your first
part release from the mold! I’m making a fleet of freelanced cars for my Hebard
Cypress Lumber Company and the frames I cast will be used for several logging
flat cars, boxcars, gondolas and logging passenger cars. These will be used earn
my AP Master Builder Cars Certificate in the NMRA. Feel free to make any scale
frame you wish as the process is the same.
02 Reference Materials
03 Find Plans or Draw Your Own
The first step is to gather reference materials on the
frame that you want to make (Pic 02). There is a ton of information on making
flat car frames available. I decided to base my car on a plan I found in the
Narrow Gauge and Short Line Gazette magazine (Pic 03). Using their drawing and
the reference materials, I drew my own freelance plan and got to work.
04 Choose Your Materials for End and Side Sills
Remember you are building a master for a mold, not the
car itself. Materials are a critical choice in mold making. Styrene works
amazingly well for a master, but wood (Pic 04) is a little trickier. Molding
materials can get into every crack and crevice and can cause the master to
break when you remove it from the set mold. Wood can also float, causing the
mold material to encapsulate it and make it unusable (want to see one)? We are
going to use wood in this case so we can get the grain look on the cast parts.
The silicone is so good at mold production I have even cast my own fingerprint
on a mold just by handling the master.
05 Take Your Time and Be Precise
Since this master is going to make lots of castings, it
should be your best possible work (Pic 05). Take your time to be precise and
build it very sturdy! Start with the basic frame. Using a sawblade and a worn
hobby knife blade I scored grain into each piece of wood. Carefully cut all the
outside boards and put them together with Carpenter’s Glue or Elmer’s White
Glue. Be sure to keep the work square and clean. Next put in the long
stringers.
06 Install Bolsters
07 Make The Assembly Strong
Once the frame has dried, I use thicker piece of wood to
make the truck bolsters per my drawing and glue them in place (Pic 06). I’m
careful to make sure they are straight and firmly attached with no cracks between
them and the stringers. Clamp them if you need to hold them in place and give
it plenty of time for the glue to dry (Pic 07).
08 Queen Post Supports
09 Queen Post Support Installed
To build the two queen post supports you will need to
measure and notch the wood, so the board is mounted in between the stringers
(Pic 08). Carefully mount these in place
being sure to get the best fit possible (Pic 09). Remember the mold compound
will find every crack and make the mold harder to remove.
10 Install Coupler Pocket Pad
11 Basic Frame Complete
I fill in the area on the ends of each car where the
couplers will go and added a small piece of wood to be a mounting pad (Pic 10.)
Once that is done the main frame of the model is complete (Pic 11).
12 Add Your Details
13 Queen Posts Can Be a Problem
14 Truck Mount Circle
15 Truck Mount Fill In
Details are next. Using Tichy and Grandt Line casting I install nut/bolt/washer castings where appropriate on my drawing (Pic 12). You will need to drill the holes for the castings because if they aren’t mounted securely, they can “float away” in the mold compound. Only add the detail parts that can be easily cast. Some, like queen posts (pic 13), will cause air pockets in the mold and won’t cast correctly. You can get away with this, as I am doing, when you do pressure casting but it requires a lot of equipment and isn’t necessary for this model. I would suggest you apply these to the part after it is cast. To make the bolster truck mount I used a small piece of styrene tube (Pic 14) and filled it in with plastic putty (Pic 15) to make a solid, round piece. After the casting is removed, I’ll drill and tap a hole for the truck mounting screw.
16 Fill Gaps With Putty
The last step for the master is to make sure that all
spaces are filled. The area between the bolster underneath and the top of the
frame will need to be filled with small pieces of wood. Once the glue is dry
take a wood filler (putty) and fill in all gaps anywhere (Pic 16). Sand each one
smooth and make sure there are no undercuts or gabs that could cause the master
to hold in the mold.
17 Coat Model with Clear Sealant
You’ll need to sand the top of the frame flat and smooth.
Wood may not release from the mold compound so I spray a light coat (Pic 17) of
clear sealant (Rustoleam Crystal Clear Enamel) and let it dry thoroughly. It
only has to be a very thin coating so you don’t lose any detail. Be sure to
spray the top of the frame, too.
18 Mount Model to Plastic
19 Build Mold Dam and Add Mold Release
20 Check Mold for Last Minute Repairs
We need to build a mold box next, so I start with a sheet
of .060 styrene and glue the frame upside down on the plastic using a few drops
of super glue. You want enough CA to keep it from moving, but not enough you
can’t remove the frame (Pic 18) from the base. The mold box needs to be about ¼
inch away from the master on all sides and on top. This gives the mold enough
strength for multiple uses without using too much expensive mold compound. I
just cut some .060 styrene into 1 inch strips and cemented them to the base
using Plastruct Plastic Cement. This attachment is in a pin-wheel fashion (Pic 19)
which allows it to be removed easily. You can’t allow any gaps in the mold box
anywhere because the mold compound will find the tiniest leak! Check your model
one last time for any missing parts like this one NBW that fell out somehow
(Pic 20).
21 Silicone Mold Compound
22 Read the Directions!
23 Measure and Mix The Silicone and Activator
There are tons of mold making and urethane resins out
there, and many more suppliers. I recommend you start with Alumilite products.
They have been long time supporters of model railroading and have great
products and video training. You can also call them up and ask a question
anytime. For mold compound I recommend Alumilite Amazing Mold Rubber Kit High
Strength (Pic 21) which is $26 on Amazon, or possibly at your local hobby shop.
This is a high strength mold rubber which you’ll need for pulling out the long
casting. Be sure to read the directions (Pic 22). I know, you are a model
builder and don’t read directions, but I warn you if you don’t do it exactly
right the frame will be coated in a silicone slime forever. When you mix it be
sure to mix it 10:1, silicone to activator. I use a gram scale for more
precision (Pic 23), but you can use the measuring cups that come with the kit.
You have plenty of time to work the material so stir it thoroughly!
24 Pour Mold Compound Into the Mold Slowly
25 Let Cure for 24 Hours or More
Starting
in a corner of the mold box (Pic 24) start pouring very slowly. I get a tiny stream going so that the compound
can drape around the master and eliminate air bubbles naturally. Pro mold
builders will put the compound in a vacuum chamber and remove the air bubbles, but
that isn’t really necessary for this project. Fill the mold box up to ¼ inch
above the bolster (Pic 25) and let the material cure for 24 hours.
26 Remove from Dam
27 Gently Remove the Master from the Mold
28 Clean Up Flashing on Mold
In 24 hours you can tear off the dam and remove the mold
(Pic 26). You’ll notice that a little mold compound will have found its way
over the wood in very thin sheets (called flashing). This is normal. Gently
remove the master (Pic 27) from the rubber mold, taking your time and going
slowly. There is no rush and you want to save the master for making new molds,
or for finishing out a model. Once the frame is removed take a hobby knife or
scalpel with a brand new blade and cut away flashing that is in the way. You now
have a production mold (Pic 28)!
29 Open Resin Kit and Prepare Area
30 Two Bottles, Parts A and B
31 Indentify Your Mixing Cups
32 Uncured Resin In Mold is Clear
Do not wash the mold in water! Urethane foam reacts
dramatically with water. The mold must always be dry. I recommend that you
start your casting work with Alumilite AlumiRes (RC-3) Tan Casting Resin (Pic
29). You’ll need about 2/3rds of an ounce per frame. This is a fast curing
resin that cures tan in color. I have used this resin for over 20 years with
great results. Many hobby shops have it or you can order online from Amazon. It
is a two-part urethane product (Pic 30) that you mix together at a 1:1 ratio.
Again, please really read the instructions and don’t bother using mold release
for this project. Mark the two mixing cups as A and B parts so you don’t get
them mixed up (Pic 31). I use a small paper cup and a popsicle stick to mix the
two. Pour in the clear A part first as it is thicker and takes more time. Then pour
in the brown liquid and mix quickly for about 15 seconds. Squeeze the cup to
form a narrow lip and pour slowly into the mold. This can be tricky so your
first casting may not come out perfect. You
only have a short time to work with the liquid so get it into the mold as quick
and clean as you can (Pic 32.)
Video Showing Rapid Curing - This is Actual Speed!
33 Resin Can Cure Very Fast
34 Different Resins Act Differently - This One Expands Slightly
35 First Piece May Need Cleaning Up
36 Put Casting on Hard Flat Surface to Cure for 24 Hours
Now the amazing part. These chemicals cause a thermal
reaction when mixed and they get very hot in the mold. Once it reaches a
certain level it begins to cure by turning a tan color (Pic 33). This happens
very quickly, and you’ll have a solid casting in a minute or less (Pic 34). Allow
the casting to cure for longer than the instructions say. I leave them in for
about 30 minutes each to get them very firm. Once cured gently remove the
casting from the mold a little at a time (Pic 35). If the casting bends a
little, don’t worry. Once it is out of the mold you can straighten it if it is
still warm. You may have a little resin flashing on the top but it can easily
be removed with a hobby knife or a sanding block. Put the casting on a hard
flat surface for 12 hours to allow it to fully cure (Pic 36). Ignore the
instructions on this because speed is NOT a friend to a casting.
37 Make Up To 25 Parts With The Mold
Inspect the casting for air bubbles and details that didn’t
cast correctly. Small bubble holes can be filled with Squadron Putty. If you have
a lot of small details that do not cast right due to air pockets, put the mold
in the microwave on high for two minutes and get it warm, then immediately pour
it. It should cure most of the problem. Depending on the master, the mold material,
and the resin you can get an average of 25 castings per mold before it wears down
or tears. I have gotten much more than that however (Pic 37).
Give it a try and have fun! If you have questions,
contact me at scottgperry@comporium.net. There is a lot more to casting and by
changing resins or making more complex mold you can make a lot of things.
