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Is there a way to adjust the speed on the Elmo st 1200hd? I managed to change the bands and lamp and it’s working great! Issue I have is the sound is a little slow like the machine is slightly slower than it should be. Wondering if there’s a way to adjust that inside the machine or somewhere to get it better at all. Hopefully there is.
Did you change, or was there one, on the shutter? I had one many years ago and the motor started going bad, slowed down and eventually stopped. The shutter belt might help a little but shouldn't be that noticeable from what I remember. But maybe someone else will chime in and help.
It could be a case of a belt slippage including something that happened to me as a result. The belt slipping actually wore the motor pulley and made the sheave deeper and deeper. This made the motor pulley effectively smaller in diameter so that the ratio of motor turns to main shaft turns went up and the machine slowed. (Unfortunately most of this happened before I bought the machine.) If you hear a squeal for a couple of seconds after you start from cold, this could be you!
Making sure your lube is good can't hurt your cause:
(This was written before I discovered the damage to the pulley. It ended the slippage but unfortunately couldn't heal the damage.)
Because of their AC motor, there really is no fine tuning of speed on these other than calling your power company and asking them to spin their generators faster. (-and then all your neighbors' clocks will run fast. Who wants to be that guy?!)
Last edited by Steve Klare; December 19, 2021, 06:37 PM.
Ah ok. This was a used machine which I cleaned all the goo from the decayed belts and replaced them all. It’s running great in the sense it’s working and sounds good but yep it’s running slower than it should. Let me try and clean all the grease and super grease it up like mentioned in the linked post. Thanks so much for your help I shall see what I can do.
oh one more thing. I know that the hz is adjusted by placing the band in a different place. Do you think that could have caused it also? If so not sure how you vary it between 50 and 60 but just wondered. It seems right the way I did it though based on the remains of the old belts.
The belt change for line frequency can't make the FPS too slow here in New York State:
There are two sheaves on the motor pulley: one for 60Hz and the other for 50Hz. In order to keep the main shaft speed correct for 24 FPS, the 50 Hz. sheave is 60/50 times the diameter of the 60 Hz. sheave. Since we have 60 Hz. power if you put the belt on the wrong sheave your frames per second would be 6/5x24 FPS=28.8 FPS=too fast.
(-but if we lived in Europe and made the same mistake we'd get 20 FPS.)
On the UK ST1200HD there are two sides to put the main belt if you ignore the small belt.
IE two on the motor pulley either side and this way or that on the clutch end.
If you put the belt on the right looking in at the back its 24 FPS but on the left its about 21 or 21.5 ish
If you have cleaned the rubber off the shutter, you end up with an extra 1 -2 FPS second faster or therabouts, so you can put the main belt over to the left to get about 23 or so, so not fast. They then run a bit quieter but still fast enough.
Which side is your Belt on Scott ? try the other side possibly and work the belt over inline at the clutch rubber roller end too.
Ah ok thanks. So if you’re looking in the machine I put the belt on the righthand side. The smaller one I’ve put above it to the left. I might give it a little switch tomorrow and see what happens. Oh, also. If anyone has any photos of the parts I should clean the gel reads from and apply new stuff so let me know.
I was hoping to project the snowman on Christmas Day, it’s a Derann print I have which looks fantastic but David Bowies narration at the beginning sounds sluggish haha.
Oh really!!! It’s right at the beginning when the guys walking through the field. Maybe the sound is bad due to that then? I’ll have to check. Below is the photo of how I have it. Can someone let me know if this is correct? These bands are square. Happy to try others if people think that’s best.
The big concern is that the motor belt is running around the smaller of the two sheaves on the pulley on the motor shaft, This allows the motor to spin more turns per frame, because at 60 cycles/sec. the motor naturally runs faster than 50.
-but, it's interesting to think: if you put it on the 50 Hz. sheave the machine will run faster. Too much? In your position it could be worth a try. Maybe by the time all the plusses and minuses add together you might come out close. (In Engineering, two wrongs can make a right as long as one of them has a negative sign!)
Speed regulation is kind of a weakness of these machines. Ideally it will spin up to the speed determined by the frequency of the house current, but in real life this slows down according to whatever drag the whole transport places on the motor. This can even be inconsistent in the same machine as it warms up: the lube softens with temperature and flows better, there is less drag and the frame rate rises. I often let mine run a little before the first film to compensate for this. (Once again: new, clean lube does help.)
This is why I like regulated DC motor machines: it doesn't matter if the mechanism is stiffer when the machine is cold. The motor circuit senses the slow frame rate, steps on the gas and raises the motor voltage and the frame rate rises until it's correct.
By the way: some (including me) have gained a little more speed by removing that small belt that goes around the pulleys of the two drive rollers up top. It's really there for 18 FPS operation and if you are 24FPS only, it's just wasted drag on the mechanism.
Last edited by Steve Klare; December 20, 2021, 10:15 PM.
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