Anyone have any clue what would cause a loop to shrink if its not the splice and the sprocket or the lateral guide is not loose?

Thanks in advance.
-Mike

If it's not set correctly the film may jump off the sprocket when a splice goes through. This could cause you to "blow your loop".

Make sure the pad roller is set so that two layers of film will go through but three won't. Put three layers of film on the sprocket and close the pad roller. When you turn the roller with your fingers you should feel it dragging because of the contact with the film. When you take one of the layers of film off, the roller should turn freely again.
Also make sure the roller is set laterally. It sould be perfectly centered over the sprocket. It shouldn't have any "end play". (In and out movement.) It sould be as tight as you can make it, yet still allow free rotation.

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But also check your splicing technique. When bent into a loop, the spliced film should form an even arc, with no kinks or tendency to fold up. Some people still make an overlap splice with tape over both sides of the overlap --- so you have two thicknesses of film plus two thicknesses of tape at the overlap, which is likely to "pop" a pad roller or get "hung up" in the gate. A "butt" tape splice on a properly adjusted splicer will usually be the most satisfactory.

Make a loop of film with an assortment of splices and see how well they go through the projector without jumping a sprocket or getting "hung up" somewhere.

I assembled a test loop of about seven splices and it shrank on only two of them, repeatedly. The thing is, there is nothing different with those splices than any other ones. My splicers are in perfect condition.

I've gone as far as taking the whole thing apart and putting it back together and there's nothing out of the ordinary. All the pad rollers (which are metal) are spinning with ease.

The next thing I would do is to be sure that the feed sprocket isn't "stalling" momentarily.
The sprocket is driven by a gear in the back (off operator) side of the machine. It is a fiber gear that's prone to chipping if the machine gets jammed. (Usually because of a "brain wrap".) The strength of the polyester film can keep the sprocket from moving but the motor will try to keep turning it. The gear will get chips taken out of the teeth which will cause them to eventually strip out. If one of these "dead spots" on the gear hits at just the right moment it will stop turning for just a split second, just long enough to blow your loop.

Open the back of the projector. (And for God's sake, make sure the power is off!) Turn the machine over by hand and look/feel for any chips taken out of the gear. While you're at it, take a look at the vertical shaft/gear that drives it. After that, turn the motor on (but keep your fingers the hell out of the way) and look closely. Can you see any wobbling of the shaft or gears? (...Wooga-Wooga... )

Looks like all areas have been covered. But nobody mentioned the sprocket itself. Is it "hooked"? Worn down to nubs?

Maybe it would be good at this point to ask if the picture stays in frame when the top loop gets smaller. That was never mentioned, either. Just scrambling for possibilities now.

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