Film-Tech Forum ARCHIVE: Flywheel problems on my Century Projector

This is topic Flywheel problems on my Century Projector in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Mark Farr-Nash (Member # 4233) on 07-20-2007, 09:43 PM:

Here's a doozy for you:

I recently swapped my flywheels on my two century projectors (as part of a project involving replacing and then re-replacing my intermittent). The new flywheel didn't quite fit as well, making a little more noise while the projector was running. I'm in mid-run, so I decide to swap it out first thing in the morning.

Heh. My bad. First, the screw unscrews itself and the flywheel falls off during the run. No problem. I stop the projector, replace the screw, tighten it down extra tight, and then start the movie. Voila. It even sounds quieter.

At the end of the movie, my projectionist is threading the movie and I decide, just for grins, to check the screw again. Sure enough, it's come out. I retrieve it and notice that it's somehow shorter...

The movement of the intermittent sheared the screw in two. Yep. In two. My brother-in-law is in the booth, right now, trying in vain to drill out the still-in-the-shaft piece so that I can hurry to the hardware store and pray to Jesus that they have a replacement screw in the narrow threads, same diameter, and length, so I can un-swap my flywheels and get both projectors up and running by 3 PM.

Otherwise, I'm in a world of hurt.

Mark

Posted by Eric Robinson (Member # 2966) on 07-21-2007, 01:41 AM:

I had a loose flywheel which spit out every screw I put in. It sheared two of them, but luckily I was able to get the remainder out with a sharp tool and lots of patience. I didn't have any good luck until I installed a new properly fitting flywheel. It does make you wonder though how it is able to shear these screws ???

Posted by Monte L Fullmer (Member # 2797) on 07-21-2007, 03:30 AM:

NOW, I'm kinda wondering how an assembly flywheel can have so much rotational force to shear off the holding screws like that when it's not that big and heavy ..

Only thing I can think of is that the rear cover plate got put back on backwards and was dragging on the flywheel...let alone a snap start from the motor..

And you'd think that the vertical driving gear that drives the assembly would be shredded out in the meantime ..

.. just interesting questions like this..

Posted by Pete Naples (Member # 761) on 07-21-2007, 05:24 AM:

The later/latest flywheel screws have a terrible habit of doing this, we often have to drill out the screw hole and tap it for a larger size, I don't remember what off the top of my head.

I suspect this is down to good old Strong manufacturing tolerances being a little wide of the mark. Never happens on older Centuries or Westrex machines. The fit between the flywheel and the shaft isn't great, so you tighten the screw up sufficiently to take out the movement, and it breaks. Personally I've never had one break but I've had them get to the stage of felling spongey through the allen key, and the flywheel is STILL slipping on the shaft fracionally.

Posted by Mark Gulbrandsen (Member # 72) on 07-21-2007, 08:01 AM:

Try getting your flywheel from LaVezzi or Wolk instead....

Mark

Posted by Mark Farr-Nash (Member # 4233) on 07-21-2007, 08:47 AM:

My current plan is to hammer out the remaining bit of screw (carefully and gingerly) and then tap in the next size up of screw and hope that it'll hold through the rest of the weekend. Otherwise, my schedule will look really wonky.

Thanks, Mark, for the alternate flywheel suggestion. I'll look into that.

Mark

Posted by Louis Bornwasser (Member # 3063) on 07-21-2007, 10:26 AM:

The secret is to realize that the flywheel wants to rotate continuously while its shaft is rotating intermittently. The screw must be really really tight to CLAMP DOWN the flwheel onto the shaft.

Soft screws are inappropriate. Use a 10-32 x 3/4" allen hex screw: Hollocrome or equivalent.

The screw is not the device by which the mounting is made; it is the force for the clamping.

Some people put the screw in backward; this is noisy and leads to broken screws. Louis

Posted by Mark Farr-Nash (Member # 4233) on 07-21-2007, 12:10 PM:

Update:

We tapped out the flywheel (10X32, thanks for the tip, Louis), fit the new screw in, and I tightened the bejeezus out of it. Also, re-switched the flywheels. I noticed that my OTHER screw on the other projector had the exact same wear as the screw that sheared off, so we tapped out THAT flywheel, too, and put a new screw in. Started it up; the projector is purring now, without that loud, plinky metallic sound.

I'm gonna watch and tighten screws today as needed, but I think the problem is fixed.

I love this website. I've told you that before, haven't I? I'm starting to feel like a projectionist.

Mark

Posted by Louis Bornwasser (Member # 3063) on 07-21-2007, 04:44 PM:

FYI: same problem on the screw in the GR-207 (fibre shutter) gear. Same screw, too. We changed them out wholesale in the 70's. Louis

Posted by Richard Fowler (Member # 893) on 07-21-2007, 06:21 PM:

Louis is giving out a trade secret on Century [Wink]

I have drawers of these screws.

Posted by Michael Moore (Member # 3867) on 07-21-2007, 07:22 PM:

Holo krome good stuff is all I have to say.
Mike

Posted by Steve Guttag (Member # 268) on 07-21-2007, 10:12 PM:

Louis is on the money here...including the mode of failure. I don't recall having to go to larger threads but definately using hardend screws and that the collet of the flywheel MUST be clamping the shaft tight or you will have the flywheel constantly trying to chop the screw on each and every pull down.

As for the GR-207...I couldn't imagine not using a hardened screw to make sure it is nice and snug on the shaft.

A common mistake I see is when one throws up their hands and loads hex-cap screws in the Century to do away with the fillister slot head screws is that the GR-7 that drives the GR-207 MUST remain as a fillister head OR one must grind down the corners of the hex-cap or they will find themselves cutting up the GR-207.

And...no complaints with Holo-Krome either.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 07-22-2007, 12:10 PM:

quote: Louis Bornwasser
The secret is to realize that the flywheel wants to rotate continuously while its shaft is rotating intermittently.

I donno Louis.. All the cams shafts in the Mountain States rotate continously.... but with pull down placing a little back load on the cam itself. Perhaps it something to do with being East of the Mississippi... or you are using some really old Wolk gears [Eek!]

.

Really, I think that you meant that the kinetic motion stored in the flywheel helps to overcome the intermittent load that is placed on the continously rotating cam [thumbsup]

.

Mark

Posted by Monte L Fullmer (Member # 2797) on 07-22-2007, 04:40 PM:

quote: Mark Gulbrandsen
flywheel helps to overcome the intermittent load that is placed on the continously rotating cam .

Now, this can bring un an interesting question with this statement above and on the issue of shearing flywheel screws: Would high gate tension cause excess work on the cam rotation and with the combining rotation force of the flywheel cause these screws then to strip if not tighten correctly?

Now, we know that Century cams are quite a bit bigger than the Simplex variety, thus more mass that has to rotate, would this be a factor as well in the condition?

Another thing on this issue is wondering if the intermittent sprocket shaft lock collar is too tight against the shaft boss where there is no allowable oil clearance between collar and the boss which could cause the 'chug-chug-chug' startup of a machine and putting excessive workload on the cam and going back to the flywheel issue as well ..

...just some observation questions to ask.. - thx Monte

Posted by Mark Gulbrandsen (Member # 72) on 07-22-2007, 05:39 PM:

1. Yes

2. Yes and No

3. [Confused]

you'r drivin slow in the left lane again....

Posted by Monte L Fullmer (Member # 2797) on 07-22-2007, 09:07 PM:

quote: Mark Gulbrandsen
you'r drivin slow in the left lane again....

.... ..been told that one before. Guess,I'd better find the gas pedal and use it, or lose it . [Big Grin]

..

Let's speed this one up a bit then: Would a tight intermittent shaft coller cause any of these above conditions?

Posted by Mark Gulbrandsen (Member # 72) on 07-22-2007, 10:14 PM:

Yes, possibly.

Posted by Randy Bowden (Member # 587) on 07-28-2007, 01:27 PM:

This has been an interesting thread. don't get me started on the poor quality of the metal that strong uses. I have had quite a few of the strong built simplex intermittents in my shop where both flywheel screws had completely sheared off. I always replace them with the lavezzi version. I also like to use brand new lavezzi oil drain screws on every century intermittent that I rebuild, the strong version is rather easy to snap the head off. How would you like to deal with that in the field? BTW I have NEVER had a single lavezzi oil drain screw break on me.

[ 07-29-2007, 01:23 AM: Message edited by: Randy Bowden ]

Posted by Mark Gulbrandsen (Member # 72) on 07-28-2007, 06:22 PM:

Randy,

No Doubt that Strong is getting their hardware from the same lame factory in Singapore (or was that Krakatoa) that makes their bearings.... [Eek!]

. Absolute crap!

Mark

Posted by Louis Bornwasser (Member # 3063) on 07-28-2007, 09:03 PM:

To be fair; Simplexs had this problem as far back as 1970. Louis

Posted by Mark Farr-Nash (Member # 4233) on 07-28-2007, 11:17 PM:

Is Lavezzi a brand name for a type of screw?

Newbie Mark

Posted by Randy Bowden (Member # 587) on 07-29-2007, 01:19 AM:

What's even more scary Mark is that people will actually order bearings from Strong as opposed to just taking a trip down to the local bearing shop [Mad]

Of course I could also complain about the poor design of the outboard bearing on the Ultramittent. I know Lavezzi builds the Ultra but did they actually design the thing? BTW I have a nice upgrade to that crappy bearing design. Perhaps sometime in the future I will post on this with pics.

Lavezzi is the manufacturer of a number of precision projector components, ie. starwheels and cam shafts. they sell the oil drain screw for the century as part number sc-1010 they also sell the washer stack that goes along with it. visit lavezzi.com sometime and you will find online photos of all the parts they are stocking. All in all I have very few complaints about Lavezzi.

Posted by Louis Bornwasser (Member # 3063) on 07-29-2007, 06:18 AM:

Lavezzi: Like UPS, most of the time they are very very good; once-in-a-while they are very bad. Luckily the good is 99.5% of the time. Louis

Posted by Mark Gulbrandsen (Member # 72) on 07-29-2007, 08:30 AM:

quote: Randy Bowden
What's even more scary Mark is that people will actually order bearings from Strong as opposed to just taking a trip down to the local bearing shop Of course I could also complain about the poor design of the outboard bearing on the Ultramittent. I know Lavezzi builds the Ultra but did they actually design the thing? BTW I have a nice upgrade to that crappy bearing design. Perhaps sometime in the future I will post on this with pics.

Haven't had all that much trouble with outboard bearings in Ultramittents in the last few yers but would be interested in seeing your solution.

You're right on folks ordering bearings from Strong as replacements... There are much better bearings available just down the street in many cases. Another VERY GOOD reason not to use the Strong Service Organization for any booth maintainance, very likely the same crappy parts will be re-installed!!!

Mark

Posted by Mark Farr-Nash (Member # 4233) on 07-29-2007, 09:25 AM:

Awesome sauce. Thanks for the tip. I'm going to check out Lavezzi right now.

Mark

Posted by Monte L Fullmer (Member # 2797) on 07-30-2007, 04:02 AM:

Yea, nice thing about living in large populus areas is that their has to be at least one bearing house to get your bearings, especially if you know the bearing number-which is stamped either on the outer race or the bearing shield.

..and saving you a few sheckels per bearing in the meantime..

(yea, STRONG .. pretty scary stuff ...)

-Monte

Posted by Michael Moore (Member # 3867) on 07-30-2007, 09:13 AM:

These days you don't need numbers on the race just a good micrometer.

does anyone know of a good source for fillister head bolts and screws? local hardware stores do not have them. I know I could use socket head cap screws but I like fillisters. I know of one source, fillisters
any idea of a better one?

Mike

Posted by Eric Robinson (Member # 2966) on 07-30-2007, 10:50 AM:

I just googled the following web page when trying to figure out what a fillister screw was:

Types of Screw Heads

Until now, I was not aware of the many classifications of screw heads. I guess I spent too much time in woodshop.

Posted by Steve Guttag (Member # 268) on 07-30-2007, 11:49 AM:

There are more head types than those too. Michael, you will want to go to an industrial supplier rather than a local shop to get the type of hardware you want.

Steve

Posted by John Hawkinson (Member # 1135) on 07-30-2007, 02:06 PM:

On the topic of alternative bearing sources, Monte writes, "especially if you know the bearing number-which is stamped either on the outer race or the bearing shield."

Michael Moore then says, "These days you don't need numbers on the race just a good micrometer."

Err, my understanding is that neither of those pieces of information are themselves sufficient. Correct me if I am wrong, please.

Replacing a bearing requires knowing the bearing grade (e.g. ABEC 7) as well as its dimensions, and a micrometer does not give you the grade. Furthermore, often the numbers stamped on the bearing do not give you either, though sometimes they may.

--jhawk

Posted by Randy Bowden (Member # 587) on 07-30-2007, 02:21 PM:

I get my fillister head screws locally at winks hardware, however the only one I ever really seem to need is the 8-32 x 5/8 that goes to the GR-7 Gear.

Yes, you can take your bearing into the local bearing house and a micrometer is all you really need to figure out what bearing you need. Same can be done with oil seals.

Posted by Monte L Fullmer (Member # 2797) on 07-30-2007, 02:26 PM:

I can see where John is coming from and give him credit for such a question, yet with my experiences I've had no problems with bearings purchased and used with just having the bearing number - even though my bearing purchases been limited to projector rebuilds and not with heave machinery devices where work tolerances are more drastic.

Posted by James Westbrook (Member # 3690) on 07-30-2007, 02:31 PM:

I wonder if bearing shops would carry the plastic bearings that Speco uses on their payouts...or at least used to use on their payouts. The last time I ordered some from them, they sent metal bearings and these were harder to install and to get to work than the plastic ones.

Posted by Louis Bornwasser (Member # 3063) on 07-30-2007, 06:51 PM:

jhawk" You are correct on both accounts. I once bought a batch of 250 new BG-9 from the local bearing shop who used a micrometer to measure. The error on the I.D. was just enough to lure him to a "standard" bearing which, alas, was not correct. I "ate it all." Louis

Posted by John Hawkinson (Member # 1135) on 07-30-2007, 09:51 PM:

Well, measurement error is one problem, but I think grade is more serious and subtle.

Let me take the case of sound drum bearing on the Century R3. When we installed CE's STRD-30 readers, we replaced those bearing, because they had started to stick. I think this is the BG-0726.

If you just measured the dimensions, you'd be tempted to use an ND77R8 bearing, which is a $5 bearing. But if you call Strong, they'll tell you that its an NHBB-SSR1812ZZ-RA8. Cost $17 from the local bearing supply house (versus $24 from LaVezzi or $32 from a local dealer).

What goes wrong if you use the wrong grade bearing? Well, probably you are compromising something. In the case of the sound drum, I imagine it worsens wow and flutter. Or maybe just lifetime.

(Now, perhaps someone will tell me that actually the SSR1812ZZ isn't anything special and paying all that extra wasn't warranted...but I wouldn't want to make that call.)

--jhawk

Posted by Randy Bowden (Member # 587) on 07-31-2007, 02:07 PM:

That is interesting. I have always just used a 7R8 bearing without any issues. I am also curious about the difference. The point that I was trying to make earlier about the micrometer is that, if you are a theatre or a tech with a failed bearing and in need of a replacement ASAP. Head down to local bearing shop with dead bearing in hand.

Posted by Mark Gulbrandsen (Member # 72) on 07-31-2007, 08:47 PM:

Jhawk,
The New Hampshire Ball Bearing they spec. is a decent bearing... not the best but pretty good for production stuff. If they'd only use bearings that good in Simplex produts [Cool]

. Barden Bearing is THE preemenent bearing manufacturer in the USA and their products are way superior to NHBB but generally costs at least 4 times more! The lower cost NHBB you mentioned is stainless steel and precision and a precision bearing is exactly what belongs in any rotary scanner mechanism. Christie also uses precision bearings in their projectors.

Mark