I just watched a (https://www.tiktok.com/t/ZPR3vNfYt/) of a guy in an IMAX projector room loading Dune 2 into the projector. But he first had to weave it through dozens of rollers. The film snaked all over the room, requiring the guy to duck under it to cross the room.
Why do they do this? Why can’t he just feed it straight into the projector and straight out?
In: Engineering
The main reason for all those extra rollers is to manage the slack between the storage platters and the projector. The extra loops act as a cushion.
For 70mm IMAX the film alone weights 500+ lbs and moves at 5.6 feet per second, so there’s a lot of momentum on those platters. If it came straight off and fed into the projector, any tiny hiccup could tear the film or damage the projector.
Secondary to the slack, those platter racks (“Quick Turn Reel Unit”) can hold 4-5 platters, with the film spooling off of any one level and back onto any other level. Thus a few of those rollers are just to get the film alignment off and on to the correct levels.
Thirdly, the green rollers near the back of the projector are sticky, and are meant to clean off any dust that’s on the film.
Fun facts about the QTRU: They are operated via a [Palm Pilot](https://www.reddit.com/r/imax/comments/152ybjn/havent_even_heard_of_palm_pilots_in_20_years/) (or an emulated Palm Pilot on an iPad) and they use [light bulbs from Mercedes](https://www.reddit.com/r/imax/comments/194fbak/imax_fun_fact/)
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