Reel Arm Bells on 5in cores vs 8in cores?

[Ryan Gallagher]

Does anyone who runs both core sizes have a method for reliably adjusting reel arm bells for suitable timing with 8in core?

Our bells are on Simplex 35/70 arms:
https://www.film-tech.com/warehouse/manuals/SMXARM.pdf

Of course the exploded diagrams have no mention of the bells we have installed. We have a batch of new 8in core 70mm house reels now... and they are silent. We have run without bells, but nice to have if doable.

It's quite possible the bells are designed for 5in core and aren't even adjustable. I'll snag a photo of our bell setup tomorrow.

[Rick Raskin]

Are you referring to the Hatke reel end alarm? If so, there is an adjustment screw that varies the timing.

[Ryan Gallagher]

Are you referring to the Hatke reel end alarm? If so, there is an adjustment screw that varies the timing.

Probably (confirm tonight), I guess the problem would be our booth does not own a suitable length 70mm test print/reel to use it to confirm timing ahead of a 70mm print, nor do we currently have an 8in core 35mm reel either to use in surrogate (although I'd like to change that). We only do 3 or so 70mm per year, one might be able to get the alarms adjusted over the course of the 1st one. But seems not worth the hassle unless there is a reliable way to count turns on the screw etc for repeatability next time.

[Ryan Gallagher]

These are our arm alarms. I've never had to investigate them before cause they always just worked with our entirely 5in core house inventory, until now (on 8in cores)

Edit: In looking closer at the photos on my computer... I see I captured brand tag. Bit fuzzy to make out... that bell is hard to get close to cause there is a christie in the way. Never noticed a tag on our other one because a prior projectionist taped a oil rag over it, because as we learned, sometimes it prefers to alarm continuously with 8in cores. But the rag has been hiding the make/model from me.

Edit Edit: Yep. Hatke. There is a better picture of that sticker on an ebay listing right now: And I see there is an "Adjust" arrow pointing hole in the outer face.
https://www.ebay.com/itm/204552946428

I wonder if the most painless way to go would be to score two more... and keep them adjusted for 8in core. Just swap alarms.

IMG_6335.jpgIMG_6336.jpg

[Ryan Gallagher]

Hah, found a photo of the paper documentation (not that there is much to it, but does say "clockwise" to increase time between alarm and reel end, good to know!).

But yeah, rather than count turns on a screw and pray, I think two sets of bells would be the way to go.

Hatke-Western_Reel_End_Alarm.png

[Tj Hopland]

Back in the day an extra set was how I saw it done. They were just in the cabinet with the rest of the conversion parts complete with the classic dymo label indicating which machine and size reels they were for. I remember some booths with several to accommodate not only 35 and 70 but small vs big 35 reels. I think part of that was to make the changes quicker since some sites would have to go back and fourth fairly often. I don't recall having to adjust that specific brand very often but some of the other brands the adjustment wasn't repeatable. Just not a fine enough thread pitch or precise components. They would hold the adjustment fine but say a 1/4 turn of the screw would not always get you the same time shift. Also note that 35 and 70 move at different speeds so an 8" 35 reel won't help you set a 70. From possibly fuzzy memory 35 is 90 ft/mn and 5/70/24 is 112 ft/mn? So the 70 reel will always be turning faster at any given diameter than 35.

Finding another set these days could be a lot easier said than done even if there was a reasonable budget. Also note that if you do find a set there could be some custom fabrication required to make them fit your arms which could be fairly expensive if you just went to a machine shop. Back in the day you could order them with the correct threads or I think in later versions they came with an assortment of adapters to fit the most common arms. These days I would think some sort of electronics would be fairly easy and cheap and would likely allow for either presets or easy calibration number that could be entered before a run. All sorts of options with something like an Arduino or Pi Pico sort of computer and a simple optical or proximity sensor on the shaft. You could then have different types of alerts depending on the operators hearing or preference and if people were seated in the balcony.

Personally I never worked many booths that had them. First couple runs I'm always nervous and watching things extra close so no need for a bell at all then if there are more runs you still either just look or know the timing from the audio. Things like the big explosion at the end of reel 1, The end of the song is near the end of 2.... After several runs it turned into a game to see how close you could cut it and how short of carbon you could burn.

[Ryan Gallagher]

Back in the day an extra set was how I saw it done....

Thanks TJ. Our booth is very much still "back in the day" in many ways despite some modern additions. Sounds like if we want bells we need a couple more for 70mm/8in setup unless there is a happy compromise timing. I like the idea of some kind of modern programmable variation, fun little side project some day.

Right now 70mm is only programmed within one week sharing no space with 35mm, but that might be possible to change if I can streamline a few things about our format conversion.

The main reason bells are nice for us is that we tend to only run 1 screening of each film (classics rep house), often without having seen any reels on screen prior. There tends to be other booth tasks to contend with in the gap periods prepping the next film's DCP pre-roll so you don't have to come in super early that day or stay too late etc, up to a point anyway... no major side projects allowed other than contending with rewinds (there is usually a 2nd person on 35/70mm screenings that helps with that). The person doing the changeovers tends to not do much else other than threading and standing by, but the alarms are nice for anyone else in the booth helping out too. Also fun to point out to lay-persons during booth tours.

I'm the type of personality that is able to hyper-focus which can cause the rest of the world to kinda fall away. I'd hate to end up into some small task in the booth and have that happen when I've got a change coming up. Prepare for the best, plan for the worst, yada yada.

Noted on the alarm timing, 35 and 70 on 8in cores will not be the same, film speed was a variable I wasn't thinking of in my original post. One of the bell sets may be able to cover two modes, just with more than normal warning. We ran Brutalist 35mm in a festival condition on 24in/8in and I don't recall not having bells, I think they were just very close to the changeover (perhaps too close depending on tail and leader beyond it).

[Ryan Gallagher]

Everything old is new again to fresh faces. Here is a prior thread on the old forums that is relevant, has a better scan of the Hatke document too:
https://www.film-tech.com/ubb/f1/t007353.html

[Ryan Gallagher]

I ended up splurging on the only two Hatke alarms on Ebay. Perhaps there were cheaper industry sources, but getting them close to their original 1970 price seemed fair enough. ;-)

We'll see if they were universal or threaded for particular reel arms.

[Jim Cassedy]

The Hatke alarms have been around for decades, (the original patent was filed
in 1945) and are pretty reliable, and I've always admired the clever way they
work. I've only encountered them in a 35/70mm booth once when I was doing
"relief duty" for The Union in the late 70's . I never ran 70mm there, but there
was a note on posted on the booth wall to move the Hatke adjustment screw
a certain number of turns clockwise (or maybe it was counter-clockwise) when
going from 35mm to 70, or vice versa. At a small (50 seat) screening room
here in SF where I used to run a lot of press screenings, the sound-proofing
of the booth wasn't that great, and so someone had covered Hatke bell(s)
with gaffer tape, so that instead of 3 dings, they sort of made a clacking
noise near the end of a reel, which anyone sitting in the back row right
under the port windows couldn't hear, but the clacking sound was still loud
enough to be heard in the projection room.

[Rick Raskin]

That's interesting Jim. I worked a booth where the bell was covered with gaffer tape for the very same reason. When I worked the old MacArthur and Apex theaters in DC they ran both 35mm and 70mm on 8" core reels so the timing was good for both formats.

[Ryan Gallagher]

Our booth is not very soundproof by our port lights either, we figure anyone sitting back there is kinda doing it on purpose on 35/70 days. But all areas that could do with improvement. Clacky bells included. ;-)

[Steve Guttag]

Rick, the MacArthur (and any AA2 projectors I ever saw with Hatke reel-end-alarms) used a pulley and chain system. The upper pulley had three grooves for the chain (35mm, 70mm 24fps, 70mm 30fps). The Alarm was mounted to where the upper magazine bolted to the projector head. It was on a 2-piece bracket. The one on the head was bent into an "L" and was fastened to a straight bracket with a collar. This formed a hinge so the bell and bracket could move as the bell and pulley turned. The bell was modified to have a pulley mounted to its back for the chain to engage. And note, by chain, we're talking about a small one that, effectively is a belt but without the wear or memory issues of a belt. I'd say that the grooves of the pulleys were on the order of ⅛".

The standard Hatke reel end alarm will not work with 8" hubs. There isn't enough adjustment for the slow-speed of the reel. For one site, I modified the track with some "shoe goo" to build up the rubber (think RTV) to allow the ball to activate at the slower speed. The next problem is that the out-track is too large so the ball falls back into the main track and resets. Effectively, you get a bell that starts ringing until the end of the reel. I don't recall ever getting the out-track small enough to prevent that.

Going with a pulley system would be better as then you can just set up the ratio desired. The size of the pulleys is going to be an 8:5 ratio (1.6:1).

If you don't want to gumm up your bells with tape...you can effectively mute them with a suitable rubber band. Use a fatter one and just put it around the bell's edge...it will kill the "ring" and you'll get a "clack."

[Ryan Gallagher]

Rick, the MacArthur (and any AA2 projectors I ever saw with Hatke reel-end-alarms) used a pulley and chain system. The upper pulley had three grooves for the chain (35mm, 70mm 24fps, 70mm 30fps). The Alarm was mounted to where the upper magazine bolted to the projector head. It was on a 2-piece bracket. The one on the head was bent into an "L" and was fastened to a straight bracket with a collar. This formed a hinge so the bell and bracket could move as the bell and pulley turned. The bell was modified to have a pulley mounted to its back for the chain to engage. And note, by chain, we're talking about a small one that, effectively is a belt but without the wear or memory issues of a belt. I'd say that the grooves of the pulleys were on the order of ⅛".

The standard Hatke reel end alarm will not work with 8" hubs. There isn't enough adjustment for the slow-speed of the reel. For one site, I modified the track with some "shoe goo" to build up the rubber (think RTV) to allow the ball to activate at the slower speed. The next problem is that the out-track is too large so the ball falls back into the main track and resets. Effectively, you get a bell that starts ringing until the end of the reel. I don't recall ever getting the out-track small enough to prevent that.

Going with a pulley system would be better as then you can just set up the ratio desired. The size of the pulleys is going to be an 8:5 ratio (1.6:1).

If you don't want to gumm up your bells with tape...you can effectively mute them with a suitable rubber band. Use a fatter one and just put it around the bell's edge...it will kill the "ring" and you'll get a "clack."

Ahh see, I knew it was not gonna be as straight-forward as I thought! The variable pully idea is clever. I also like the rubber band, much cleaner than current vintage rag taped over one of them.

70mm 30fps also raises another point. We technically have 30fps capacity... and it has been done in the past. Not likely in the future but still.

So both 8in core 35 and 70 24fps will be too slow for the adjustment screw? Or just 35mm 8in?

The clever arduino approach is starting to sound more and more appealing. At least with our black reels an IR tachometer sensor would be pretty easy to add, for the goldbergs one might have to inverse the function and use a piece of black tape. Hall effect would be doable but don't want any magnets near our 70mm reels, we'll probably have mag prints again one day after a mag head swap.

Could avoid adding tape to the reels and just put a target on the rotating part of the clutch, or a disc target that lives behind the existing hatke alarms. Or you could take a different approach entirely and attempt to use a laser rangefinder to measure how much film exists on the feed... but any out of true in the core or spindle would easily throw that method out of the needed precision. Using such a proximity sensor would probably be better aimed at a rotating flag on the back side of the arm, to calculate RPM, not unlike the IR method and targets.

Seems logical considering sound spillage concerns, that a better modern alarm would include a silent mode and instead flash a beacon or LED strip as the warning, provided it is mounted in such a way as to not spill into the house itself.

Seems like a bit of a trap to have an non-fool-proof electronic alarm that requires selecting the correct preset for the film type, core dia, and playback speed. If you wanted to get really spendy with sensors you could add a 2D barcode scanner or RFID reader that "IDs" each house reel's variables... and FPS could probably be gotten from the VFD. Hands free! (Unless there is a ton of post tail leader to contend with, but early alarms are fine, late ones are not).

[Ryan Gallagher]

This is just getting silly. But with enough "calibrated" tach targets on a ring, you could probably start to live characterize reels behaving badly (excessive bounce or out of round cores etc). But now you are getting into functions that would probably be better handled rotary encoders and discs. And suitably overkill for reel end alarms. lol