There seem to be two schools of thought on this, and I'd like to get a cross section of opinion from the experts on what to do.

I plan to mount the sound drum shaft in a drill press Thursday evening, then apply 3M Finess-it II finishing material with 3M Imperial microfinishing film until I see a high mirror finish. This technique was recommended by Jim Duncan in Decatur AL.

However, I mentioned this to another tech, and he said I would ruin the sound drumm using this method. He suggested taking the shaft to a machine shop, having it indicated, then reground.

Which is better? Do I risk ruining the sound drum with the finishing compound?

Wolk wants 289 bucks to replace this part. I think we all know that is more than this sound head is worth.
 

First of all, drill presses are not very accurate when it comes to precision work. And if you do insist on using a drill press, then use the best chuck that you can...like a precision Albrecht!! And double check that the drill press is running true and that there are no burrs in the chuck! How do you know that a chuck will not damage the bearing surfaces on the shaft! If you insist on this method, then put the shaft and drum in a lathe with a collet--which should not damage the shaft. Also, when hand polishing, how do you know that you are not going to screw up the coeccentricity of the drum and shaft which will result in a definate unwanted wobble!! Also, Even though it may look like a good polished surface, how can you be sure that you have not created a taper or "wave" on the drum surface! If you do insist on this method, then you will probably need to inspect your work with proper inspection dyes and oils--such as if you were scraping bed ways--which is an art of its own--or a surface plate with v-blocks and dial indicator.

If you look at the ends of the shaft, then you can see the center drill counter sinks that were used when the part was origonally turned, heat treated then o.d. ground. If the shaft and drum is put back on an o.d. grinder, then a mag base and dial indicator can be used to get everything perfectly "clocked in" and coencetric--not to mention a perfect finish! My only concern is the possibility of maybe having to regrind the bearing surface also to match the drum. You would then either have to find new bearings with the correct dimensions, and grind to those dimesnsions, or press on sleeve bearings to make up the difference.
 

As far as ruining the heat treated surface. This is dependant on the type of material used to make the drum, and the heat treat process. There are heat treating processes used to just treat the surface of the material (case hardening), as well as proceses used to treat the entire thickness of the part. There are also secondary heat treat processes used to do things like tempering.

If anyone knows what type of material these shafts were made of, then I can look up the correct heat treat process.

My only regret is that I am already finished with my machine tool classes for now. Making a sound drum and shaft would have been a suitable class project! Harry--see if any of your local community colleges have machine tool programs. Enroll--you'll learn something and may be able to make some parts? Also, check out if there are any machinists hobby clubs in your local community--they may be able to help you out!

 

I was taught to take a piece of brown paper, like a grocery bag, and saturate it in WD-40. Then use that as if it were a piece of sandpaper to remove the rust. I have used this technique with some success to remove rust from sound drums as well.

Whether using this on a projector or on guns, the main idea here is if the problem can't be fixed this way it's probably too bad to be fixed another way without replacing the part in question.
 

Here is an example: When I went away for basic training, one of the things that I did was prep my tools for storage. I thourghly cleaned them, coated them with WD-40 and put them back into my roll-a-way. Mind you that my roll-a-way was indoors and not subject to a corrosive atmosphere: ie water etc. Well, when I came home on leave between leaving basic training and going to my first duty assignment I of course checked my tools. ARRRRRRGH!!!!!!!!MAJOR RUST!!!!!!!!!!!!!
I had to spend a lot of time cleaning them, and was lucky that some very expensive tools were not ruined!!!!!!!!!!!! Anyhow, after cleaning them up, I had to reprep them for storage. I used Marvel Mystery Oil, and did not have the same problem--in fact, it did an excellent job of protecting my tools, which were stored under the same conditions that they were when I origonally stored them with
WD-40. I WILL NOT recommend WD-40 to anyone!!!!!!!!!!!!!!!!!!!

Another MAJOR contributing factor leading to rust/corrosion is fingerprints and the oils emitted from your skin!!!!!!!!!!!!!!

There have been articles in machinists hobby magazines like Home Shop Machinist about hot blueing metal...
 

Can you describe in explicit detail the kind of scratches you are getting? Honestly, assuming that your sounddrum is spinning freely, I'm thinking your scratches are most probably coming from elsewhere in the projector. Can you take a brand new trailer and run it a bunch of times and mail me a clipping of the scratches? I'll take a macro picture of it and post it here.
 

I downloaded the RCA books from Film-Tech. Quote the RCA 1040 book page 6 item(10) second edition Sept 23, 1936 or 8 ('tis hard to tell):
"The A.C. Motor is of the split phase starting, induction type and runs at a constant speed of 1765 R.P.M. It is rated at 1/4 h.p. The motor incorporates an automatic starting winding from the motor circuit when normal running speed has been reached." I wonder if the 1765 r.p.m. is a typo? Unfortunately, I could not find a reference to motor r.p.m. in any of the other RCA 1040-9030 or Simplex SH1000 books. Furthermore, much of the info was not stamped onto the motor's data tag at the factory--I wonder why not, since there are blocks in which to stamp this info.

Gordon, what about the start resistors having been removed on the 1050 and later soundheads as per the books?

According to the RCA 1050 book, downloaded from Film-Tech, the origonal open bearings were replaced with metal shielded bearings. One thing that I have learned is that metal shielded are much-much better than rubber shielded, which tend to be stiff!! But, the metal shielded will not hold lubricants/grease as well as rubber shielded bearings. The only thing that I like about shielded vs open bearings is less chance of notorious oil leaks, which can ruin slit lenses!

Gordon, surface grinding and o.d. grinding should be done after heat treatment, otherwise you are defeating your purpose. Thanks for the info about the origonal heat treat process. My guess is that case hardening was picked as a means of shortening the production time!
 

Harry, if that cat of yours was mine he would now be a wall decoration after what he did!

WD40 is more solvent and only a lubricant until it evaporates. Once it has evaporated so has any protection you thought you had.
 

------------------
Greg Mueller
Amateur Astronomer, Machinist, Filmnut
http://www.muellersatomics.com/
 

I agree that it isn't the best thing to use in many circumstances but in this case it is used to help dissolve any rust on the surface.
 

Incidentally, I am sending a few frames of some virgin trailers I ran through the system five times. The scratching is almost invisible, but I want to be absolutely sure my system is running as clean as humanly possible. Take my word that in no other facet of my life am I this anal.
 

------------------
Greg Mueller
Amateur Astronomer, Machinist, Filmnut
http://www.muellersatomics.com/
 

We'll find out a week from tomorrow. Incidentally, I printed this entire thread out, and I'll take it along for him to read. That way he'll get the gist of what's expected of him.

Are your scratches contained to just the middle of the film or are they kinda random?

If they are just in the middle, often the culprit is not the drum but the pad roller for the sprocket just past the drum. If the isolation loop between the upper and lower sprocket is too large, the film will pucker into the middle of the pad roller (this is true on the simplex gear-box soundheads too). The solution is to reduce the size of the isolation loop until the film clears the pad roller (typically it will look like a ")"

Steve

------------------
"Old projectionists never die, they just changeover!"

Most of all I'd like to thank John Ulery for his help in regrinding the sound drum. He told me that the surface had some crowning.

It looks like new. I replaced the bearings as well. The difference with the new bearings and drum is dramatic.

I ran a virgin trailer through the system today, and it looks like we're scratch-free. I looked at it through a magnifying glass while reflecting the surface off of a light. Time will tell, but I think we licked it.

My screening room is approaching a place where I will send pix. I think ya'll will be pleased. All you guys deserve some of the credit.
 

So now, the best thing to do would be to put the soundrum on V-blocks and a surface plate and measure the "crown" with a base and dial indicator. That way the O.D. Grinder can be properly adjusted for a taper, or the grinding wheel can also be "dressed" for the proper profile.
 

Just my $.02

Josh
 

I agree with you about the Davis Tight Loop seeming to be the prefered method. However, when I started to rebuild my RCA 1040 I was concerned about scratching prints with the full drum and roller assembly. I was also concerned about possible print scratches caused by dirt being trapped in the indentations in the pressure roller. So, I asked several parties for their opinions about the Davis Loop vs the full drum/roller assembly. One of the parties I asked was Dolby Labs. Everyone has said that as long as the componets are kept clean and properly maintained, then you should not have damaged prints. Everyone has said that the two methods are accomplishing the same task in a different manner. Notice that the Simplex 5 Star is a hybred between the two methods. However, having the film be in minimal contact with a surface seems to logically be better. One thing to note on the full drum/roller assemblies is that the pressure roller should be left open when not in use-to prevent flat spots from forming. On older soundheads like the 1040, this will prevent you from closing the compartment door. But there is a little pin pressed into the compartment door that I removed--so that I can close the door and keep the pressure pad in the open position when not in use. But this may be a bad idea because that pin in the door can act as a safety to prevent the pressure roller from accidently opening while in operation. Also remember that there were several types of pressure rollers used over the years. Metal, felt, and now the rubber with indentations. The rubber with indentations is the last one introduced and is the only new style available and is the preferend style. Wolk makes them and they are around $30.00
 

I know you guys have sometimes between 12 and 25 projectors going at once in your theaters. And you techs...good lord, you have to service hundreds of them. But this huge thing that I refer to as "Black Betty," sits right next to my desk in my home. I nursed her back to health after she sat around in a barn for who knows how long. She was just a rusty hulk. Thanks to a lot of help from everybody, she shows a bright, steady picture again, this time in my screening room. All my friends think she's really cool. Part of me is allowed to be a kid again. Life is good.
 

When I was with Josh in July, we "cleaned up" (very gingerly) one of his scanner drums.

I will agree with Josh - If they are too glossy, they'll slip more. I heard somewhere that if they are too glossy, they will cause problems and should be replaced or refurbished. I think it was MTS that told me that. I also heard something to that effect in MPO school in 1967.

Paul

P.S. - your screening room with the Moshees is a real beauty! I would love to run a booth like that. You must have spent alot of time and money on that project. Job well done.

Paul

Soon it will get renovated to a pair of 35/70 with a 200 when time permits
 

The squirrely rubber rollers were not much better. Even if those were kept clean, you could still see railroad track smudges on the emulsion side of the film after many runs of the print.

The solid rubber ones seemed to fare much better. All they left was a BIG WIDE railroad track.

Unfortunately, operators forget to clean the rollers and guide flanges on a regular basis.

Some of those scanner drums get really bad! Even Buzz-Track was all over the place...especially if the guide flanges and the scanner shaft bearings were less than perfect.

The scanner drum Josh and I did looked good when we finished. It was almost a basket case when we started, but now it has has a smooth (but not glossy) machined looking surface. I think it will be OK. It still had some small rust specks in it, but those will polish out eventually. I have seen some in service that look much worse that what he has now.

I forgot to take my micrometer and a run-out indicator with me, so I could not check it for "wooga wooga's" or other defects. It was a "fly-by-the-seat-of-the-pants" type of repair.

If for some reason it is out-of-round, there is a good machine shop in his area that could square it up for him without too much trouble. The only thing he might have to re-do is the sound focus.

Paul