Film-Tech Forum ARCHIVE: Unbalanced

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Posted by Ian Price (Member # 14) on 11-09-2000, 11:15 PM:

I think that some of the problems I have been having with my Simplex XL is an unbalanced shutter blade.

The projector has a vibration problem. The vibration is causing the framing to move down. You can see the vibration when you look in the back of the machine becuase the shutter drive assembely is bouncing on its spring.

When I loosened the shutter to retime the shutter, I turned on the machine and the vibration was gone. When I tightened the shutter the vibration was back.

What do you think?

Posted by John Pytlak (Member # 331) on 11-10-2000, 07:02 AM:

Ian said: "When I loosened the shutter to retime the shutter, I turned on the machine and the vibration was gone. When I tightened the shutter the vibration was back."

Your observation would certainly seem to implicate the shutter. Is there any evidence that the shutter has been modified (e.g. cut or bent) in some way? Is there any gap between the hub and shaft which might make it rotate slightly off center? Since it rotates at 1440 rpm, any imbalance could cause vibration.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

Posted by Scott Norwood (Member # 30) on 11-10-2000, 08:22 AM:

If the shutter itself is OK, is there any chance that the shaft is bent? What happens if you swap shutters with another machine? Is this the same machine on which you just swapped intermittents? Did it have this problem before?

(I'm not that knowledgeable about XL's, so this probably seems really obvious, but maybe not...)

Posted by Gordon McLeod (Member # 33) on 11-10-2000, 09:17 PM:

Check and make sure the shutter hasn't got a nick in it from at some point hitting the heat shroud. That can happen and make the blade bent or off balance. Also it can in some cases damage the bearing race

Posted by Richard Hamilton (Member # 321) on 11-11-2000, 05:06 PM:

Hey Ian,
I had this same problem about7 or 8 years ago. I'm not sure, but it seems like one of the screws that hold the intermittent flywheel was stripped and sticking out about half way. I thought i remembered you saying in an earlier post that you had screws that were sheared off? Possibly this is enough to cause a vibration. A quick fix is to clamp a heavy pair of vice grips on the framing knob shaft, and it can't rotate.

Rick

Posted by Randy Stankey (Member # 64) on 11-12-2000, 08:16 PM:

I happen to have a little bit of expreience with bent-up shutter shafts. (I have one sitting right here on my desk.)

If you take the shutter completely off and run the machine for a few seconds you'll see the end of the shaft sort of "dancing" as it spins. If it doesn't then I'd take the shutter and see if it balances. Get a big screwdriver and put it through the hole. Hold the screwdriver perfectly flat and level then give the shutter a spin. Watch how it spins and notice if it spins evenly. Do it two or three more times and see if one side always ends up at the bottom. (Use a marker and put a mark on it so you can tell.) If it does always end up one side down you've probebly got an out of balance shutter.

If not, maybe there is a problem in the shutter shaft, bearings, spline, drive gears or something like that. Are all four of those allen screws that hold the shutter shaft and bearing assembly properly tightened?

Are there any unusual noises? That's a pretty good telltale when your projector starts going, "TICKA-TICKA-TICKA-TICKA-TICKA-TICKA"