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 Post subject: Radio Knobs
PostPosted: Feb Sat 07, 2004 1:24 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1586
Location: ayer ,ma usa
This is weird, but it is almost impossible to find just plain ole like 1/2-5/8 " brown knobs, like most small AA5's in wooden cabinets or bakelite have, for a half flat 1/4 shaft ; I contacted Larry, and bought some knobs for a special Emerson (the u5A) but he had nothing for low $ for the run of the mill sets we often work on. The latest thing for the mental defectives among us to do (there must be a lot of them!!)is to go to a flea market or antique radio meet and pull the knobs off antique radios, and sell them on Epay; as a result, the last two truly junk radios I bought at NEARC ($15 for one , you can have both for $20) had no knobs. Both came back to perfect..I really like saving very small dumpster radios, a problem I have! Anyway, what about finding generic brown knobs that look nice on these small radios? AES does not have the right stuff, either. Someone should ask these Epay guys where they got all those knobs...with no radios.<P>------------------<BR>


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 Post subject: Radio Knobs
PostPosted: Feb Sat 07, 2004 1:28 am 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34326
Location: Sandpoint, IDAHO 83864
That's probably explains all the old sets I have come across without any knobs. I have often wondered what happened to all the knobs, as I know some of them can be a real bearcat to remove, and I doubt if any of them simply fell off! I can imagine people at a yard sale or flea market simply walking by and helping themselves to the knobs and then putting them on Epay.<BR>Curt<P>------------------<BR>Curt, N7AH


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 Post subject: Radio Knobs
PostPosted: Feb Sat 07, 2004 1:49 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 11474
Location: Valley City ND USA
It's the bane of the antique business too. Tube swipeing not unheard of either. <P>I sometimes wonder if they pilfer in the hope that I will sell the remains to them eventually, for cheap.<P>------------------<BR>terry h


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 Post subject: Radio Knobs
PostPosted: Feb Sat 07, 2004 1:54 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3667
Location: Circleville, OH, USA
It's interesting that radio auctioneers like Richard Estes remove the knobs from sets like Zeniths when they put them on the floor. The buyer can get them from the cashier when he checks out. Learn from experience.<P>------------------<BR>


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 Post subject: Radio Knobs
PostPosted: Feb Sat 07, 2004 2:44 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 27407
Location: Detroit, MI USA
Sometimes surplus dealers like Fair Radio have offered some older looking generic radio knobs for less than a buck apiece, but those kind of deals are hard to come by. There used to be plenty of sellers offering original knobs in the range of $2 to $5 each at the major radio shows but the supply is rapidly drying up and prices increasing accordingly. On an expensive radio, say one worth $200 or so, you don't mind paying a reasonable price to get one or two original knobs. But on the majority of collectible radios which are valued in the $50 and under range, the cost of a set of original knobs can sometimes approach the value of the radio. <P>I find that one solution to this problem is to learn how to make your own knobs.<P>Knobs are very easy to duplicate at home using casting resins. All you need is one good original and you can make as many copies of it as you want for under 50 cents a knob in material costs. There is about $3 to $6 in special RTV silicone needed for each mold, depending on the size of the knob, but you can usually make a lot of knobs from a mold. The resin costs maybe 10 to 20 cents per knob, and the setscrews about 20 cents each. <P>It is not hard to do. I could not believe it was so easy until I saw it done and then tried it myself. You can dye the resin any color you want, and even make acceptable looking replicas of wood knobs. The detail is so good on the repros you can see the grain of the original in the new part. The only thing that may be a problem for some people is that a drill press is needed to make the shaft holes after the knobs are molded. Then a small hole is drilled in the side of the knob and tapped for a setscrew.<P>This is the only easy and inexpensive solution that I am aware of to the ever growing problem of missing knobs. Just pick a few nice looking knobs that are generic enough to be usable on many different radios, and make up a supply of 20 or so of each one, so you have them on hand when needed.<P>------------------<BR>Dennis


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 Post subject: Radio Knobs
PostPosted: Feb Sat 07, 2004 2:52 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2255
Location: Saskatoon
I'm interested in trying to make some knobs for couple of my radios, but I have one that could be a problem. It's a two tone plastic/bakelite, light brown with black flakes in it. Has anyone ever tried making anything like that?<P>------------------<BR>


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 Post subject: Radio Knobs
PostPosted: Feb Sat 07, 2004 3:07 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 27407
Location: Detroit, MI USA
Bob, the technique for doing that would be similar to what is used for making swirled colors in a knob. You mix the resin and dye it with the lighter color, take a toothpick or an artists brush with a tiny bit of the darker color, and touch it to several places on the inside of the mold. Experiment to get the right technique. <BR>If you wanted to duplicate catalin or other swirled colors, you would take the second color and very lightly swirl it into the mixed lighter colored resin just before pouring it into the mold. <P>If you want to get some ideas for just what kind of parts people in all hobbies are making, check out the demonstrations and examples at <A HREF="http://www.alumilite.com/" TARGET=_blank>http://www.alumilite.com/</A> Look at "applications" on the top header bar.<P>I saw their live demo setup at a hobby show and was very impressed. This is not rocket science. You need to be very careful with correct proportions of all the mixtures when using, but it is very doable on the kitchen table. There are many other suppliers for the various resins but Alumilite Co. has excellent tech support, has a very nice demo video available, and if you live near their headquarters in Kalamazoo, MI they will supposedly even give you one-on-one lessons in the methods of casting parts.<P>------------------<BR>Dennis


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 Post subject: Radio Knobs
PostPosted: Feb Sat 07, 2004 5:32 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 12
Location: granger, IN, USA
I would like to echo those comments. I have been casting some knobs for my Beolit 40, which is an unusual set. No way would I be able to find original replacements. I was lucky enough to have one original knob with the set. Using the Alumilite product, I have had no problem replicating the knob, and the results have been great. I even used it to replicate some broken bakelite grills on the back of this set, and they turned out very good.I know I may sound like an advertisement, but they deserve credit for a fine product.<P>------------------<BR>


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 Post subject: Radio Knobs
PostPosted: Feb Mon 09, 2004 6:26 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2947
Location: Lexington Kentucky
To Mr Detrola and fargoboy,<P>I have experience around similar casting technology and I'm wondering how you got the shaft bore centered and if you were using some type of insert for the set screw threads? Maybe I'm too much of a perfectionist but I'm concerned about concentricity, stripped threads, or slipping retainer springs after doing a lot of work to cast the parts. In my industrial experience the shaft bore would be formed by a polished, tapered, metal pin coated with mold release.<P>Also what about bubbles in your casting resin?<P>I'm not being critical - just would like more info before spending money.<P>------------------<BR>


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 Post subject: Radio Knobs
PostPosted: Feb Mon 09, 2004 10:26 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 27407
Location: Detroit, MI USA
Dave, I suppose you could do it that way with an insert for the shaft and setscrew. The method I have been using when making repro knobs is after removing the knob from the mold, to first file or sand the back side smooth. Then find the center using X method. I have a really nice vise on the drill press which is adjustable in two dimensions (as well as at an angle which is not helpful for this), and of course can also move the table itself if needed. I wrap the OD of the knob with friction tape or use a section of a flat rubber vacuum cleaner belt for padding, and drill with a 17/64 bit, using the adjustable stop on the drill press. After getting the depth right, I change bits to another 17/64 bit with the pointed end ground flat to get the bottom of the blind hole flat. Then flip the knob on its side, and using a #29 machinists drill, make the hole for the setscrew, which once drilled is easy to tap by hand. <P>Your mileage may vary depending on exactly which brand and type of casting resin you choose, but so far with the Alumilite I have never stripped out a setscrew that was 3/16" to 1/4" long. The material seems to be pretty hard when cured. I know that some others are using various 2-part industrial epoxies to cast with, and have similar results. I think this would be a good area for experimentation. The mold making process itself seems to be relatively straightforward, and once you have a good mold, then different casting materials can be tried to get the results that suit you.<P>If you wanted to set up a jig for casting and could get the shaft hole perfectly centered I see no problem in using a pin the diameter of the shaft coated with mold release. In fact, when we went to the hobby show to see the factory reps do the live demonstration, they suggested either using that method or drilling depending on how much time you wanted to spend or how many of a particular part you wanted to make. But if you are even a tiny bit off when locating the pin, the hole is either not going to be concentric to the knob or not deep enough.<BR> <BR>I also see no problem if you want to make inserts from brass or aluminum stock that are predrilled for the shaft. They would have to be splined on the OD to prevent tearing loose in the knob, just like the originals were on old knobs. I would still want to drill the setscrew hole and tap it in the insert after the resin was cured. <P>As far as bubbles in the resin, I mix in the small plastic medicine cups, and stir in a manner which creates a minimum amount of bubbles. More bubbles are created from the required shaking of the resin bottles before mixing, than from stirring it. On a really intricate mold, I sometimes use a small brush to insure the resin is conforming to the mold, or just use the wooden stirrer stick to coat the mold before filling it. Out of about 10 parts cast, I get maybe one bad one, but the resin is dirt cheap and there is a learning curve to everything. You learn pretty quickly about mixing in exact proportions and having everything clean.<P>If casting clear parts using the clear resin, it is necessary to use a small homemade or purchased vacuum chamber before pouring the resin to de-air it, or some bubbles may be trapped inside the resin. I find that I can make acceptable solid color parts using the beige or white resins dyed to whatever color, without using a vacuum chamber. <P>I also learned that you want to use a premium quality RTV silicone for the molds. It does not cost much more than the standard types, and is much more durable. It is possible that you can buy small quantities of the RTV and resins at some local hobby shops, the model car and train hobbies have been using Alumilite and Castolite for many many years. The RTV and resins have about a 6 month shelf life once the original seals are broken on the bottles.<P>------------------<BR>Dennis


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 Post subject: Radio Knobs
PostPosted: Feb Wed 11, 2004 7:44 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3423
Location: Olympia WA USA
I can add a bit of information on casting.<P>I worked a bit with John & Nancy Greaves of NW Special Effects. (www.lifecasting.com) He also does life castings.<BR>He uses a vacuum chamber to draw out the air.<P>Some others use a vibration table.<BR> <A HREF="http://WWW.Cementex.com" TARGET=_blank>WWW.Cementex.com</A> is a great source for mold materials. I have ordered from them. Good product. Great info and assistance from them too<BR>I also understand Tapp Plastics (sp)carries molding materials.<P>I am very interested in this as I have dozens of radios missing 1 or more knobs, and have been considering starting to mold my own.<P>David Pirkle (of Pirkleations- artist &, sculptor), has helped me out in the past. He has become quite adept at making many small, intricate parts with the 2 part plastic casting resin. He told me he was able to match the colors by using CeramCoat paint to color the 2 part plastic material. He has used liquid latex to make 1 use molds and RTV for several use molds.<P> If you add Seco powder (a thickener & binder)to liquid latex and make a thick mold, you can get several copies out of it without much degradation.<BR> I have made some very rugged latex molds by reinforcing the latex with strips of nylon pantyhose or stockings. The latex really oozes thru the nylon, and the nylon adds incredible strength to it.<BR> (I made an "alien headpiece" ala STTNG using that method and it has held up to repeated rough use for over 7 years now. No "Static Kling-on" jokes please.)<BR>FrankB<P>------------------<BR>


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 Post subject: Radio Knobs
PostPosted: Feb Sat 14, 2004 10:46 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 22
Location: Spain
I have seen original ones in a magazine called, "Antique Radio Supply", they have all kind of knobs". Did you try there?.<P>Bye folks.<P>Gus From Spain.<P>------------------<BR>Gustavo M.


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