Take Up Reel Adjustment/Sound drum tension...

[Yves Leibowitz]

Hello All,

I have mentioned issues on here before with the projector I am running. My take up Reel was not picking up speed and The tension becomes too much. I have noticed as I have increased the speed of the take up reel tightening up the spring on the mag arm, The tension jumps to dangerously too much when starting the motor. Could the speed of the take up effect tension around the sound drum? And is there a quick easy fix to moderate the tension and have the correct speed for the take up reel? Please let me know. Belts and such look good on the Projector. So do sprockets and rollers.

- Yves

[John Eickhof]

what make and model projector / soundhead ? if its century, you are probably experiencing too fast of start up causing reel to lag then catch up and pulling film pasdt holdback sprocket, this can also tighten the film around the sound drum causing flutter and wow. if using 24" or larger reels, make sure they are floating hub type and it would be advisable to have 6 or 7" hubs and not 5", thus the reel will keep up with the projector start up speed better, the other solution is to make sure there is a slow-start kit installed on the motor preventing high torque, high speed start up. take up clutch adjustments should be made carefully and some are quite sensitive do not make radical adjustments. it appears that you need to have a qualified technicoian come in and check things out.

[Yves Leibowitz]

It is Century JJ3TA
I made some adjustments and so far it seems to work better. Looks like all the reels are 5 Hub. I cleaned the lower mag arm and put in a new Kelmar Pad. Naturally adjustments were made. Looks like i need some time to get the right speed since one would have to adjust very slightly. Silly question what would a slow-start kit look like on the motor?

[Gordon McLeod]

depending on the vintage a small metal box that is bolted onto the motor or underneath the paddel

[Yves Leibowitz]

Here is the motor in the attached photo's. There were two little boxes attached and same color as the entire motor.

[Mark Gulbrandsen]

What we really need to see are the take up and feed arms. Not the motor. It's obviously an issue where the take up clutch needs to be serviced...It's simple, unless the felkt pads in the clutches themselves need to be replaced. The felt pads in the take up and feed clutches need to be properly oiled and then the tension gets adjusted.

[Sam Chavez]

Let's back up here a minute. It's not the actual speed of the reel you are adjusting. One way or another it's 24 frames per second. LOL! It's the amount of friction of the take up clutch that determines the tension on the film and to some extent, how fast the reel starts when you start the projector rolling.

[Steve Guttag]

...and belt slippage. The mass of the reel will also come into play at the start of the projector (hence why floating hub reels can reduce that).

[Jim Cassedy]

Yves Wrote: "There were two little boxes attached and same color as the entire motor."

I believe the things attached to the motor in your photos are just the motor capacitors.
But I know the other 'boxes' you are talking about and have seen them on some older
machines. The boxes I saw simply had a large high-wattage resistor inside which was
connected in the starting winding circuit to and gave a psudo soft-start to the projector.

A true soft-start is a really nice addition to a projector. It not only prevents the film jerking
at start-up, but puts a lot less stress on the projector drive-train. It usually requires a 3
phase motor, but I think there are devices for single phase motors too. (Or you can do
the old 'big resistor" trick if you know how to re-wire your motor) One of the venues I'm
at has a 500ms ramp-up, and the whole machine starts nice & smooth, instead of
with the usual sudden "jerk". It's much easier on the projector & film. Since I run
change-overs, I just need to thread up a little shorter to compensate for the start time.

As for the issue you raise about the take-up tension affecting the sound drum, this
should not be a problem. The 'hold-back' sprocket, in combination with the mechanical
filtering properties in the sound-heads in modern projectors should prevent any take-up
irregularities from 'back-feediing' into your sound system, unless something is really
out-of-whack

On a historical note;
The very early sound heads in the late 1920's and early 30's were not as well designed
and were somewhat prone to having take-up irregularities (say from a bent or uneven
reel) find their way back to the sound track scanning mechanism and affecting the sound.
Several devices, such as the one below, which were intended to be bolted between the
sound head and the take-up magazine, were designed to add an additional sprocket
to insulate the take-up from the sound mechanism.

Stabilizer.jpg

[Dave Macaulay]

That's a standard synchronous motor, used on almost all projectors after multiplexes boomed. The external things are the start and run capacitors. No slow start beyond having the heavy flywheel, that takes a while to get to speed.
So the start speed is as designed and your take-up should be ok. What size reels do you use? Large ones, like 6000ft, need to be slip hub to have reasonable tension while avoiding slack and snatch on startup.

[John Eickhof]

the motor is a bodine synch motor, known for high torque and fast start, increase the capacitance of the start cap and starting torque will be lessened, it is more apparent since the projector is direct drive and starts fast like the msa 35mm, century notoriously had a slow ratio take up drive, thus the simple way to solve is to wind a hundred or so feet of junk film onto thge take up reel to increase hub diameter thus the start up speed of the reel will increase slightly and with careful adjustment you should be able to get it solved. the slow start kits were designed for the original split phase ac motors not for cap start motors. the only other remedy woulkd be installing a 2-3 second time delay relay that would place a 50-100 ohn resistor in line with the ac feed to reduce the line voltage on start up then cut out after 3-3 seconds, otherwise, be patient and keep carefully adjusting the clutch.be sure the new felt pad is lightly oiled too.

[Gordon McLeod]

Is it possible you have the wrong takeup arm for a century The one for simplex had a different diameter pully on the early ones

[John Eickhof]

thanks gordon! i forgot that kelmar had a smaller drive hub just for century and motiograph! it should be approx 2 1/2" dia smaller then the one for simplex and rca soundheads....my memory is showing its age! i probably have a couple of the smaller diameter pulleys....

[Nantawat Kittiwarakul]

Probably too late to join in but...

All symptom mentioned sounds like too slow takeup reel, or too fast motor start, or both.
In that case you may try these two tings.
1.Adjust the takeup tension so that it gives you just enough torque to spin the reel from start to finish without film saging/spilling at the end.
2.Lots of projectionists in my country back then had a habit of placing their free hand on the takeup reel spoke, and give it a "push start" when first start the projector to help the reel to get up to the speed. Sounds crude/barbaric, but when properly done - it simply works.

[Mark Gulbrandsen]

Is it possible you have the wrong take up arm for a century The one for simplex had a different diameter pully on the early ones

Actually, the Simplex 5-Star and the Century had the same diameter take up drive pulleys. The SH-1000 and XL reproducers were just a little bit larger if at all. That's why there was just one set of Kelmar arms made.... other than the 35/70 arms. Oh, RCA was similar to SH-1000.