Stripper Advice

[Jim Cassedy]

(I knew that would get your attention!)
An unfortunate crummy tail splice came apart the the other night right after I did a
change-over. By the time I could get over to the other projector, most of the tail leader
had wrapped itself around the upper feed sprocket, knocking the 'stripper', which is
supposed to prevent that sort of thing, out of place.
While I can rotate the stripper-thingy back into position, it is still very loose, and can
be easily moved if my fingers bump it while threading.


Here's The "Stripper", Rotated Back Into Position
Stripper_1.jpg

There Is A Setscrew In Here, But No Matter How Much I Turn It, it
Doesn't Seem To Have Any Effect On "Locking" The Stripper In Place
Stripper_O.jpg
But On The Other Projector, I Can Turn That Setscrew And
Make That Stripper Plate Tighter Than A New Pair Of Shoes


Any Ideas? I 'm thinking that either the set-screw is stripped, although it 'feels' like it
isn't. Or, I think that stripper plate is just press-fit onto the end of an axle-like shaft, and
perhaps that's come loose. Other priorities and having to work an overabundance of
live events have kept me from doing much troublshooting yet.

[Randy Stankey]

I think, maybe, that film stripper did its job and sacrificed itself to save film and projector from further damage. In the process, the shaft that mounts it to the projector has been galled to the point where the set screw no longer has enough purchase to hold it in place.

If you remove that part from the projector and inspect for damage, I bet you'll find a deep groove in that shaft.

Since the film stripper is kind of a sacrificial part, that's what I'd expect to see.

[Jim Cassedy]

<edited>

Since the film stripper is kind of a sacrificial part, that's what I'd expect to see.

I didn't think of that!. I've got a couple of 70mm shows coming up (including some sort of
BRUTALIST media preview in 70mm right after Thanskgiving) - - so I'll be doing the 35-->70mm
conversion probably over this weekend, and I'll have a chance to look at it when I do that.

[Mark Gulbrandsen]

Just place a thin internal tooth lock washer where it plugs into the chassis, or grind a point on the tip of the set screw.Either way, problem solved...You'd have to have a really bad Estar pile up to sacrifice that stripper!

[Frank Cox]

You'd have to have a really bad Estar pile up to sacrifice that stripper!

That sounds like the setup for a horror movie.

[Ryan Gallagher]

If the shaft is not terribly damaged, I would try tightening the set screw without the stripper installed to test if I is bottoming out on a bad thread before it has enough pressure to hold the shaft? Solvable perhaps if true.

i’ve reshaped at least one set screw head to avoid prior divots in a shaft causing a part to index incorrectly upon tightening.

[Steve Guttag]

The plate is press-fitted to the axile. It is entirely possible that it has come loose. You might have luck peening it in place (use an appropriate pointy tool that has stronger metal to, effectively, expand the metal.

Note, the upper feed stripper should be bent over such that it blocks the film from being able to go back up into the penthouse. This would also prevent it from rotating due to the force of the film piling up above the gate. The sprocket side of the stripper should come VERY close (as close as possible without touching the sprocket screw or any part of the sprocket) for it to be effective.

[Ryan Gallagher]

The plate is press-fitted to the axile. It is entirely possible that it has come loose. You might have luck peening it in place (use an appropriate pointy tool that has stronger metal to, effectively, expand the metal.

I didn't think of that either. If one removes the plate and axle should be able to tell in hand if the parts are no longer solidly mated in the friction fit pressed connection. In projector would be hard to tell if it is the plate rotating or both the plate and axle. Though some good light and a reference dot on the axle might reveal if the axle is stationary but the plate is rotating around it.

[Mark Gulbrandsen]

It should be ptetty easy to tell if that's the case. I don't think it's a press fit, but instead some sort of weld. I've had over a dozen JJ and Cinerama heads, pass through my shops over the years, and never had any issues with the film strippers.

[Jim Cassedy]

I had some time today to pull that sprocket stripper outta the JJ.
There is a set-screw in that mystery hole, but that wasn't really a surprise.
The pivot thingy that the stripper plate is attached to is pretty scored, as
you can see in the photo.(and as Randy S predicted it would be. )

I might clean this up a bit over the weekend. The setscrew is OK.

Perhaps that was from when it got knocked out of place a couple of weeks
ago by a film pile-up, or when a co-worker also had a major sprocket-wrap
about a year ago. I've always felt its been very slightly loose since then.
Notice the flat-spot worn near lower end if the shaft in the photo too.

And, as Steve G mentioned, the plate is press-fitted to the axle-thing, and it
was obviously stressed. I was able to peen-it pretty securely back into place.
Stripper3.jpg
'I've got a couple of other minor fixes I want to take care of in the booth, so
I'll so I'll put this all back together some time over the weekend.

[Randy Stankey]

Thanks, Jim. I'm glad you got things figured out.

I think that the common concept of the film stripper standing at the ready, just in case, but never really doing much is oversimplified. In reality, that little hunk of metal can take a real beating. Maybe not every time but more often than people realize.

Every time a reel of film tails out, the last bit of film flaps around as it goes through. Maybe the last frame or two has tattered sprocket holes. Maybe there's a stray bit of tape or something. Maybe a bit of random bad luck makes the film get hung up. To make an analogy, it's like the goalie in a soccer game. The goalie stands at the ready to be sure that an errant ball doesn't go into the goal but 90% of the time he just seems to stand there and watch.

The film stripper doesn't take big hits very often but it can, very well, take small bumps on every reel of film. As the old saying goes, "Water wears away the rock, not by strength, but by persistence." A little bump, here... A big hit, there... It all adds up. Then, one day, you look over and realize that hunk of metal looks like it's been through a war.

It can be an easy thing to overlook because, after looking at the thing, day after day, it becomes like a piece of furniture. You don't look at it because it's "just there."

I've had the same thing happen to me. One day, I take a look at the projector and realize that some part looks like it's been through the mill. I try to think back, through recent memory and say to myself, "Hmm... That bump I had the other day must have been harder than I thought."

[Brad Miller]

Tailing out will not put any "wear" on a stripper moreso than if you took a piece of film in your hands that was 4-5 frames long and you held one end and slapped the other end up against a stripper. Essentially if the last frame on a roll during a tail out touches the stripper at all, it is an effective zero hit.

[Randy Stankey]

I wasn't trying to say that an ordinary tail-out will damage the projector. Of course, the equipment is designed to handle that sort of thing. It can happen all day long and nothing bad will come of it. Absolutely agreed.

On the other hand, there are things that happen which will give the projector a hit which will, gradually, take their toll. It is very easy to overlook things like that. It's just human nature. Sometimes people just don't notice things until the water has already gone under the bridge. Call it "entropy" if you will. A person has to be on the lookout for things like that, even if they only happen a few times per year.

All I was saying is it that, often, a person looks back at things and realizes that something has gone wrong when he didn't think anything bad happened. It's important to keep this in mind even if it only happens on once in a while.