Film-Tech Forum ARCHIVE: Simplex Lower Constant Speed Sprocket Movement

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Posted by Joe Redifer (Member # 3) on 12-27-2002, 09:31 PM:

The lower constant speed sprocket on my fabulous Simplex 35 is moving laterally back and forth nearly an eighth of an inch, and it causing a bit of print shedding. It's not just the sprocket, it's the entire shaft and the gear that moves back and forth as well. Everything on the assembly is tight. I cannot discern any visable wear or damage on the gear of the sprocket nor on the connecting gear that lives on the vertical shaft. When rotating the motor flywheel forward slowly, there is a point where it feels a bit "snug". The gear to the lower constant speed sprocket stops at this snug point. The connecting gear on the vertical shaft makes exactly 1 rotation per "snugness" so to speak. I hope that I am making sense.

Do I need to replace that gear on the vertical shaft? God I hope not. Does not look like it could be done quickly at all. Also I don't look good in an apron, which you need in order to do that kind of work on a Simplex. [Smile]

Edit: If it were the gear on the vertical shaft, wouldn't the sprocket be rocking back and forth incredibly fast during normal operation? When the projector is running, it bounces back and forth about once per second or so, and it isn't always a steady rhythm. Perhaps I should just say "the hell with it" and build a new theater from the ground up and start over? I bet that would fix it.

Posted by Mark Gulbrandsen (Member # 72) on 12-27-2002, 10:56 PM:

Joe,
Check the gear on the end of that shaft, near the bottom of the gear train. Its about the diameter of a nickle. There is an allen screw that goes through that gear and the shaft. It is most likely loose. There does need to be oil clearance in there, so a thousandth or so end play is a good thing.
An apron only absorbs all the oil and turns you into a human torch just waiting for a static discharge from the next new print arrival....

Posted by Dick Prather (Member # 1136) on 12-27-2002, 11:39 PM:

Joe,
I don't know how much you want to get into this thing but I find it easier to remove the lower sprocket assembly. That way you could see everything dealing with the sprocket and should be able to tighten the lower sprocker drive gear also if needed.

Normally if the gear comes loose or moves I wouldn't expect more than 1/32 +- a little of end play not 1/8".

Things to look for:
Loose or moved lower sprocket drive gear.
Broken or missing wave washer (behind sprocket).
Broken or missing snap ring (behind sprocket between thrust washer & flat washer).

If you do remove the assembly clean rubber gasket or better yet replace when putting it back together. As you know a slight looseness in gear mesh is normal. This will change as you tighten the four screws. Hope this helps.

Posted by Rick Long (Member # 213) on 12-28-2002, 12:21 AM:

Careful though, I have had more than one of these G-1812 gears fall apart on me due to cracks. Might be a good idea to have a spare on hand.

Posted by Joe Redifer (Member # 3) on 12-28-2002, 02:26 AM:

Actually I did remove the entire assembly today, and that's how I discovered everything is tight. I'll have to take a picture of it and post it to see if you guys think anything is missing, but I don't go in again until Saturday night. So check back late that night or early Sunday and you can tell me if you think anything is missing. All I know is that it didn't do this last week.

I wish I had a spare of everything.

Posted by Pat Moore (Member # 380) on 12-28-2002, 06:49 AM:

Joe; Dick covered (very well) what I would recommend, as that whole assembly comes out with four allen screws. You won't need an apron unless the machine's running or it's WAY over-filled with oil. [Wink]

As for what happened, beats me, unless that gear is loose on the shaft or the snap ring behind the sprocket just disappeared. The parts book is pretty clear on the parts used on the assembly. You should be able to take up any lateral slack by adjusting the gear on the shaft. Allow just enough play so the shaft rotates freely. Same thing when the assembly is re-installed, a slight amount of gear play is fine and desirable.

Pat

Posted by Joe Redifer (Member # 3) on 12-28-2002, 04:06 PM:

I could not see any way to adjust it laterally. The gear screws on with a hole that goes directly through the shaft, and the entire shaft moves. I could not see any other way to adjust. From what Dick describes, everything is still there. I am not at the theater now so I am basing all of this from memory.

Posted by Pat Moore (Member # 380) on 12-28-2002, 07:42 PM:

Hi Joe; You should be able to loosen the screw that holds that gear to move it on the shaft. There isn't much play in that hole but you shouldn't need much -- like Dick said, I'd be surprised if you could get as much as 1/16" lateral play unless something is missing from the assembly.

Let us know what you find...

Pat

Posted by Joe Redifer (Member # 3) on 12-29-2002, 02:11 AM:

OK I am back with pictures. Every screw is tight, and I have not been able to adjust anything. Once again it is the entire shaft that the gear sits on that is moving, not just the gear. So something connecting to the shaft needs to be adjusted.

This is the whole thing.

Here is a close-up of the gear itself. Should there be that much empty space between the silver part and the white part? I am thinking "no". I have had this gear off and I cannot move it in any closer to decrease lateral movement.

A close-up of the sprocket itself. Does it look like anything is missing (besides the rest of the projector)?

Thanks in advance.

Posted by Dick Prather (Member # 1136) on 12-29-2002, 02:43 AM:

Joe,
Hard to tell exactly without the sprocket shaft disassembled.

By the space between the G-1812 gear and the casting in your second picture it looks like one of your thrust washers is missing. Sometimes they stick to the gear when you take the gear off the shaft and fall off. There should be a thrust washer(P-1451) on the sprocket shaft at both ends of the bronze bushings. That would cause lots of end play that could not be adjusted out.

Posted by Joe Redifer (Member # 3) on 12-29-2002, 02:49 AM:

I had approximately 15 minutes between shows to get these pics, so I couldn't go nuts disassembling it down to the bare components. I know I didn't drop a washer when I took the gear off, but I will probably order another washer anyway, if my theater can afford it.