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Author Topic: Anyone have a RCA soundhead thread pattern? Will Kutler Phenomenal Film Handler Posts: 1506 From: Tucson, AZ, USA Registered: Feb 2001 posted 12-04-2004 08:41 PM                     Hi Paul Usually the powder coater will do the stripping for you, and is included as part of the service charge. It is usually done by media blasting. Clean media is usually used to prevent surface prep contimination, and media blasting will also help with coating adherence. Media blasting is technical, and correct media and technique must be done so that the part is not actually ruined. You need to specify what surfaces are to be masked. Besides taping, there are various types and sizes of plastic plugs and caps specifically made for masking machined surfaces on industrial equipment as preparation for paint finishing. The powder coater should have these. And if not, then auto body/paint masking tape (that wont leave unwanted residue like regular masking tape) can be used. Cheers K.  |  IP: Logged Pete Lawrence Expert Film Handler Posts: 192 From: Middleburg, PA Registered: Aug 1999 posted 12-04-2004 09:32 PM                     Did I start something I shouldn't have? Maybe those of us that like RCA sound heads should line up on one side of the street and everyone else on the other side. Then we could throw old trailers at one another. Seriously, I do agree with Brad that the rubber roller is a real weak spot in the design, but I'm not ready to toss them in the bay yet. Even though the bay is only a block away. I do use Film Guard and haven't seen any roller marks. As to Will's comments about the motor and slit lens... The original slit lens can be easily disassembled and cleaned if it's full of oil. I've done several of them. Would I use them in an operating theater? No, of course not. There would have been reverse scan readers in there, but for a home screening room allowences can be made. I have replaced the originals with narrow slit ones. The budget hasn't allowed for reverse scan, yet. The motors on RCA heads are another matter. Flywheels, special shafts, and couplings aside, the book says they must be 1765 R.P.M., not the readly available 1725 R.P.M. ones. Only about 2.3% difference in speed, but enough to be wrong. One mans "patina" is another mans "gunk". That's easily cleaned off and there's really no excuse for it being there.  |  IP: Logged Michael Wilkinson The Entertainment King of Colusa and Beyond Posts: 89 From: Colusa, CA USA Registered: Apr 2004 posted 12-04-2004 10:01 PM                        With almost all prints in digital anyways. How big of a deal is .3%? As for the rubber roller-Yes I do see some marking on the film at tear down. However in running a print 4 shows per day for 7 weeks I did not notice anything which detracted from the presentation. If anyone has a workable pad roller replacement, please let me know. I look at the 9030 as a great workhorse. They have run for nearly 60 YEARS and could probably go another 60! They start smooth which I believe is also a plus. Once again with the optical sound now basically a back up, why would I want to change them out??? Oh yes, I just drove 250 miles to save three orphaned 9030's from going to the scrapyard! PS Brad-If you have a boat-I could send you a couple of castings so you could live out your little fantasy.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 12-04-2004 10:13 PM                    Here's an interesting question: Is there really a difference in the gear ratio from input shaft to sprockets between the RCA's and the Simplex 10XX? BTW, what's the difference between the motor that does 1765 vs. 1725? Same basic type of motor, isn't it? You have so many poles on the rotor and so many poles on the stator and 60 Hz. power, yes? It chases sync but unlike a sync motor doesn't catch it. So it lags and isn't the amount of lag largely due to loading? Are these really different motors or is there a difference in someone's interpretation of nominal speed?  |  IP: Logged Will Kutler Phenomenal Film Handler Posts: 1506 From: Tucson, AZ, USA Registered: Feb 2001 posted 12-04-2004 11:07 PM                     Some time ago, I asked a few very experienced (older and wiser ) FT members about the 1725 vs 1765 rpm differences in motors. The answer I received was that the projector motors are actually the standard 1725 rpm, and that the 1765 rpm info was used to encourage customers to purchase the more expensive motors from the projector/soundhead manufacturers. However, if there is any doubt, a small motor repair shoppe can run the motors on a test stand with a tachometer to see what is true ! Cheers K.  |  IP: Logged Pete Lawrence Expert Film Handler Posts: 192 From: Middleburg, PA Registered: Aug 1999 posted 12-04-2004 11:16 PM                     quote: How big of a deal is .3%? Well, it's 2.3%, not .3%. I know musicians that would go ballistic if their recordings were played back with that much error. With regard to digital sound, the error has to be made up somewhere, probably by a pause or skip periodically. As to traveling that far to save a couple RCA heads, I'd do the same thing. Way to go Michael. I drove from NY to FL and back one weekend to save a pair of 1040's. As to Steve's question. The amount of lag or slip is controlled by design. Motor speed is usually quoted at full load, whatever that may be. Four pole sychronous speed is of course 1800 R.P.M. Non-synchronous four pole induction motor speed is always less and a balance between running torque, starting torque, starting current, rotor resistance, and assorted other characteristics. Instead of my posting a bunch of links, do a Google search on "ac motor slip" and you will find many detailed articles discussing it. Edited to add the following about Will's comment... Based on the RCA books for 60 Hz the bronze sprocket gear is 49 tooth, the drive shaft pinion is 10 tooth and the film sprocket is 4 frames per revolution. So 24 frames per second equals 360 R.P.M. for the sprocket. The motor shaft should rotate at 360 X (49/10)R.P.M which is 1764 R.P.M. That seems pretty straight forward to me. Does a 1/3 HP, 1725 R.P.M motor run close to that when driving a projector and sound head load? I can't answer that.  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 12-05-2004 02:02 AM                     With regard to digital sound, the error has to be made up somewhere, probably by a pause or skip periodically. Nope. All 3 digital formats speed up or slow down their rate to match the film rate. No skips, jumps, pauses, or double dutch. --jhawk (Though if there was to be double dutch, obviously SDDS would be the one to do it.)  |  IP: Logged Ian Joseph Parfrey Film Handler Posts: 56 From: Bollier Queensland Australia Registered: Sep 2004 posted 12-05-2004 04:36 AM                     Pete. Good to see you've started this RCA thing. It's a passionate thing when it comes to what someone likes and dislikes. That's probably why we don't have just one make and model of projector/soundhead/lens &tc. Mind you, if I had my choice........ Mike. I'm getting a boat!!!!!!!!!!!!!!  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-05-2004 08:34 AM                     quote: Paul Trimboli Will was talking about getting the soundhead powdercoated and have read others talking about it before. How do you deal with covering up parts of the castings like where bearings would be installed? The reason I say this is becuase if you masked the holes up they would then chemically strip it. So do you strip it yourself or do you just got back and mask the holes before its powedercoated? Has anyone powdercoated a Simplex Standard before? Again similiar questions to masking it. Chemically stripping any projector part with critical tolerances is the only way to preserve those tolerances. There are others that will tell you that certain types of abrasives are ok to use but by experience in refinishing hundreds of pieces of projection equipment I have found that to be very false. Abrasive blasting not only removes the machined finish but it also does this in a very uneven fashion because its all done by hand. The only other method that might work that I have yet to try is extremely high pressure water blasting. There are only a few p[laces in the U.S. that do that sort of operation. As for powder coating.... environmentally its a great thing and from a quiality standpoint its excellent if applied peoperlym has to be just the right thickness. Masking is done with a special high temperature green colored plastic like tape that is available in alot of different sizes, use it just as you would macking tape. Holes are plugged with high temp cork like plugs that come in a myrad of sizes. Several things to be aware of if you powder coat is that any casting that has been subjected to lots of oil must be properly cleaned before coating. If its not properly cleaned it will bleed oil and ruin the finish at that spot leaving a big splotch with no paint adhering. Castings cannot be preperly re-powder coated once that have been coated. Since the coating is so tough it pretty much has to be machined off before that could happen... so you pretty much have one chance to make it come out looking good! You can also have problems with air bleeding out of castings that will leave you pin holes in the finish..... Very large castings cannot be powder coated because the casting has to evenly heat up for the paint to fuse properly... even preheating it wown't work on something the size of a DP-70 main casting. Hope this helps.... and don't sand blast anyting with machined surfaces!!! Mark  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 12-05-2004 08:36 AM                    So then how many teeth on gears & pinion in the Simplex gearbox?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-05-2004 10:27 AM                     RCA and Simplex are the same... just different hubs on them. MArk  |  IP: Logged Will Kutler Phenomenal Film Handler Posts: 1506 From: Tucson, AZ, USA Registered: Feb 2001 posted 12-05-2004 12:05 PM                     Yes Mark Any part with machined surfaces needs to be given extra attention when media blasting. As I previously stated, there are proper ways of masking off those machined surfaces when preparing to media blast. Furthermore, care should also be taken when chemical stripping. Damage can also be done with these methods, if the correct chemicals and procedures are not followed...namely immediate corrosion caused by water and water based chemicals, and possible material removal caused by surface-prep etchants. Cheers K.  |  IP: Logged Bob Koch Expert Film Handler Posts: 183 From: williams ca Registered: Nov 2001 posted 12-05-2004 02:25 PM                     About 1947 RCA supplied a metal roller to replace the felt one used prior on all RCA stabilizer soundheads similar to some Western Electric reproducers. I changed to this on all reproducers on my run. Then came the "rubber tired" roller[#51961]. Some of the first were eccentric, making the pressure roller move rapidly up and down on the film. Some damage was reported{the rubber tire mark] to film but in those days [changeover remember] it was usually traced to one machine only which was usually found to be bad stabilizer or pressure roller bearings or improper assembly of pressure roller shaft and split ring. All in all I liked the soundhead although when you had a Brenkert on top of it you were putting on overalls and doing a gearbox rebuild every year or so. If you had an XL that was the end of doing the rebuilds.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-05-2004 02:28 PM                     We use a local place called "The Stripper" and they use an industrial grade paint remover on our stuff. When you get the castings back they look like new... they are also reasonable. I've also used Redi-Strip as well for really huge batches of castings and they always did a really nice job on them as well. Unfortunately most of the Redi-Strip locations are no longer because they used Sodium Cyanide(in hot tanks)as the stripping agent. They are still in operation in a few states and in Canada though. Mark  |  IP: Logged Will Kutler Phenomenal Film Handler Posts: 1506 From: Tucson, AZ, USA Registered: Feb 2001 posted 12-05-2004 02:51 PM                     Hi Mark Thank you for mentioning Red-Strip. They have a location in the Phoenix, AZ area...Mesa or Tempe, I believe. Anyhow, I am interested in your feed-back regarding this company, as they have recieved much publicity in automotive restoration circles. What I understand, this is one of the few companys that will do a full emersion tank strip of an entire car body, as their process can get to areas not accessable to dry media blasting...especially in unitized construction car bodies. From what I understand, they use a two-tank process, the first strips everything, and the second kills corrosion. They state that their process is non caustic, so metal thinning via caustic etchant chemicals is not a problem. Cheers K  |  IP: Logged

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