Molding switch knobs and others

[Guest]

Anyone, I just got all of switch knobs from aircraft bone yard, but there weren't enough of them. But until then, the ideas that I have just popped up by having them molding it. If I could remember, All I do is create a cardboard box and pour molding in half then apply switch in it, then again pour molding to fill it up. As soon as it get dried up I would tear up card board box and cut the dried mold in half so it could have similar shape as the knob. then drill the hole in middle of it so I could pour in fiberglass or some kind of plastic-like into it and let it dry up for couple of mintues and open up the modling-box and it would have similar shape as the original knob. Unless anybody can bring up similar ideas but better methods let me know.

[Guest MikePowell]

Arthur,You might have better luck with acrylic casting resin than epoxy. Casting resin is sold by art stores and plastic suppliers like Tap Plastics www.tapplastics.com There are how-to books that describe how to do casting. I've seen them in passing, but unfortunately do not remember any titles or authors.Fortunately there is an expert at making knobs in our midst! Nihad Allush has made some excellent looking Boeing style knobs for his B747-400 sim. http://www.allush.net/techinfo.html You might drop him a note for details.Mike

[Guest dakenskys]

Hi Arthur,There are a few casting choices. If you want clear castings so you can transilluminate them, you can try the hobby plastic which is a polyester resin. It has an awful smell and you add a few drops of catalyst to make it set up in several minutes. The pros - nice and clear, can set up rather quicklyThe cons - Is very prone to shrinking away from the mold and creating a surface that has "wrinkles" in it. The other method is to look for an industrial plastic resin supply and use a poly-urethane liquid compound. The pros - Much nicer surface finish, very clearThe cons - Takes much longer to set up...perhaps a few hours.You can help the castings along with a little heat and if you have a pressure pot, adding about 40 psi pressure.On the mold side...the best compound to use is also available at that resin supplier, in the name of silicone RTV.This is also a liquid that you mix in a catalyst and it cures in several hours. There are many different types of silicones, which vary in durometer (hardness) and other properties. I have worked with all these resins and silicones for the past 25 years, so there is a lot to learn.Take a look at the attached photo...Silicone rubber picks up every little detail!Good luck, and if you need any further advice, drop me a line.Ken

[Guest]

Ken, Thank you for replying... Basically, what I am looking for is some kind of molding that can shape up the knobs, and pour in some polyester or silcone. I was hoping if I could use molding, I could reuse it again and again in order to make knobs as much as possible. I have experienced with polyester resin, Yup! it sure smell awful, very strong. I applied on one of my friend's jet skt tha has a cracked bottom. Bad experience is, I made a terrible mistake, I had to sand it for hour and hour to get it shaped like it should be. Now I suppose without any molding that can shape up knobs would be hell of a work for me. I wouldn't mind trying using this but would it be possible for it to come off of molding so I could reuse it? About silcone, I don't have much knowledge on silcone. But I got e mail from Nihad www.allush.net, He briefly explained me that all I need to get a original knob, and have wood stick underneath the knob, apply vaseline on the knob so it can get it greased not getting silcone stuck on it. Then mix up silcone rubber with its hardner and to brush it first to create layer so that can avoid air bubbles then I can pour rest of it. As it get dried, I ll have the molding. Then next thing I would need to do is to get clear polyester or expoy reseude and pour in it and it would dries up like crystal clear. Now I suppose its a good way of doing it unless you propose some idea if so please e-mail me at projectb767@aol.com please also include some step-by-step on creating knobs. Again, Thank you

[Guest dakenskys]

Arthur,Some of your info is correct, but let me explain a bit further:A silicone mold will keep it's shape and be good for at least 100 castings before it starts to break down. You do not need to use vaseline as the silicone has a natural release property. The steps are:1) mount the knob onto a piece of plastic on the bottom.2) any holes that are on the sides (hex keys) you should plug up with childrens modeling clay.3) you can take a plastic disposable drinking cup, cut open the bottom, and turn it upside down and glue over the knob to the base.4) Mix the silicone, read the directions, usually 1 part catalyst to 10 parts rubber, but different brands have different mixing ratios.Make sure you mix very well! or you will get uncured spots in your mold.5) you can brush over the knob as Mihad says, then pour in over the knob. Cover the knob at least 1/2" over the top of it.6) Let cure. Make take 16 hours to overnight.7) cut the cup off of the cured rubber and peel the rubber from the knob. That's it/8) I would then bake the rubber at a low temp, around 200 deg F for a few hours to force any catalyst out of the mold.9) Now you can pour a casting. Let cure, and pop out of the mold.If you have a problem with this, perhaps I could help you by making the molds for you.Ken

[Guest dakenskys]

Arthur,I tried to e-mail you, but it was returned.Send me an e-mail at: daken@optonline.netKen

[Garys 209]

You can also use a product called Knead-A-Mold which is a 2 part silicone rubber mould making material made by synair corp. www.synair.com I use the sp-25. The best part is that it only takes 40 mins to set and it gives the exact result as the pic above. Like Nihad I used knobs from the 747-400 so I was only able to have the knobs off the aircraft for a few hours at a time. 0nce you knead the 2 parts together you apply a thin layer over the knob to begin with to make sure that you have a good bond and no airbubbles and once it is fully covered you then apply more to build it up. Once the mold is hardened you then mix up some auto putty in a cup and place the mold in the putty. You dont have to do this if your only making 1 or 2 knobs but if your making plenty then its advisable as this will stop the mold loosing its shape over time.As for what to use to make the knobs ive again just used autoputty.It gives great results and its easy to paint. I originally started to make translucent knobs using polyester and epoxy resins but if I decide to make it like that in the future I would definatley take Kens advice and use a proper plastic.CheersGaz