Duplicating parts

Scratch build the parts! Keep your eyes peeled for anything, anywhere that can be used for scale models. I recently ripped apart a few old watches for the gears and small parts to be used somewhere. Actually some gears will complement a mechanics scene I am building for a contest this weekend. Basically think outside the box, scratch built and scavenged parts will complement the contents of said box.

Look for a PE set that has the blades as part of the fret. Much cheaper and less time consuming than casting. You can also scratch'em out of styrene sheet. Cut each blade and start assembling them. Just takes a little patience and time.

Make an impression mold, preferably with sulfur-free clay, and cast them in 5 or 15 minute epoxy.

I'm with Ross, on this one.  It's fast, simple, effective and the outcome is repeatable.

Depending on the amount of detail, you may want to brush a little bit of the epoxy into the mold first, as it will help avoid blank spots and air bubbles.  Just make sure to use a brush you don't mind throwing away, afterward.

-Fred

I like scratchbuilding, and using the clay mold and epoxy as Ross and Fred suggest is a good method, too.

If I knew that I had to make many examples of the same part, I'd consider making a full 2-part mold and cast them in resin.

What is meant by "sulfur free" clay? Are we talking of the type of modeling clay that I played with as a kid or the kind I made ashtrays out also as a kid? All I am trying to do is I have a several Hasagawa F-16's that I want to build. One each of  an "A" and a "B" model with Twobob decals in Navy Aggressor markings, and then two "C" models with ANG markings for Colorado Mile High Militia (my home state) and South Dakota Lobos (I love SD and I love wolves)

The kits feature blank, closed intakes and I decided to open them up. I was then left with a gaping hole and I needed something there. I then thought of an old Monogram (no Revell then) A-10 Warthog kit I never built because of the poor fit and quality (In my opinion) There were 2 fans I could use. I used a little better than half of one for the F-16 and decided I needed more to complete all 4 kits, plus there have been other kits that are lacking as well. I don't want to sacrifice the second until I can obtain more. The fans are barely visible in any case so perfection would not be required here.

A sulfur free clay is one specifically made for making molds for casting, as the sulfur can interfere with mold-making materials and casting resins. Do a web search for "Chauvant clay." You want the softest variety. Some sellers of casting supplies also sell the clay, and you can probably get it from a sufficiently large artist's supply house like Dick Blick.

I think MicroMark also carries sulphur-free clays, and I think you can find it at the craft store chains, Michael's, A C Moore and maybe Hobby Lobby, too.

Thanks for all the info. I have a Hobby Lobby about 1/2 mile from me and I will have to check it out. I also need to order some Parafilm from Micro-Mark and will look there as well.

If you have a Hobby Lobby, then by all means, use the 40% coupons and buy the latex and resin... Skip the kit though.. You'll get more material buying the larger latex tubs...  HL sells Alumalite latex mold material for about 20.00 IRRC...  I use "Amazing Casting Resin" for the parts...

To get the coupons, go to the HL site and print out as many as you need for that week..  They don't have the 40% coupons every week, but you'll hit every couple weeks... You can use one coupon per day... 'Course, there's ways around that, heh... I'll use one in the morning, then another after shift-change around 1700, and have the wife use a third if I need to...

http://www.hobbylobby.com/weekly/coupon.cfm

After a day of rotating tires, yard work, house work, and running across town to check on Mum, I finally got to HL 10 minutes before they closed. All I was able to locate was some regular modeling clay that says 'sulfur free' in that short time. I thought to give that a try with the epoxy. The results do look fairly good, but the clay stays stuck to the part, and is hard to remove. I tried to see if lacq. thinner would remove it and found out that the thinner does a nice job dissolving the epoxy. Scratch 1. Any hints or tips here?

I've done some experiments with ordinary fibreglass resin from the autoshop & plasticene, crude & smelly.

Prep some plasticene in a container 2-3 times larger than the desired object, allow to warm, dust with talc or other release agent, then drip resin into the smash inpression.

Also tried with plaster for pouring & impressions in plasticene, then cleaning up the plaster part & painting on the resin as above, for strength, better.

Some guys swear by using sillicone Silly-putty instead of plasticene, but can't comment on this as I haven't found Sillyputty in the uk. 

jimbot58

After a day of rotating tires, yard work, house work, and running across town to check on Mum, I finally got to HL 10 minutes before they closed. All I was able to locate was some regular modeling clay that says 'sulfur free' in that short time. I thought to give that a try with the epoxy. The results do look fairly good, but the clay stays stuck to the part, and is hard to remove. I tried to see if lacq. thinner would remove it and found out that the thinner does a nice job dissolving the epoxy. Scratch 1. Any hints or tips here?

Just a little 'bump' her to try for a possible answer to my question about removing the modeling clay from my cast piece.....

You need to use a mold release on the clay before you pour the epoxy. Vaseline will work, as will some silicone grease.

Thanks for the tip! I wonder about some Labelles grease I have from my model Rail Road...safe for plastics and contains Teflon? Perhaps if i coated my original part in it, and pressed it into the clay, it would leave a coating behind? I shall have to experiment a bit here-try both ways. After all  it's a learning process for me!

I wouldn't use the grease, as it may react with the fluid epoxy. Vaseline is pretty inert. A silicone lubricant will also work, provided it isn't absorbed by the clay.

I'm happy to report that the grease I used had no effect on the epoxy, the molds came out very well, and after a bit of trimming and fitting, a bit of paint, I placed  the new fan at the end of the duct, and....well, I think it looks pretty darn good for my first attempt! Besides, I am the only one who will ever see it! I plan now to save the original and use my copies for my F-16 family.

Thanks a bunch to all of you who offered advice and your knowledge! It was a great help!

Jim