New video update. Need feedback!
Also, some calculations to see just what kind of RPMs we can expect in the system. Please take a look and tell me if these look right to you. I’m dense when it comes to this stuff.
35mm Linear Length
1 frame = 18.6mm
24 frames = 446.4mm/s
RPM Calculations for Standard Reel & Split Reel Cores
STANDARD REEL
diameter of reel @ base: 107.95mm
circumference: 339.135mm
446.4 / 339.135 = 1.32 RPS
= 78.98 RPM
STANDARD CORE
diameter of core: 50mm
circumference: 157.08
446 / 157.08 = 2.84 RPS
= 170.4 RPM
Outer Circumference
STANDARD REEL (this represents the max, as most split reels are smaller)
outer diameter of reel @ edge = 361.95mm
outer diameter circumference = 1137mm
446 / 1137 = 0.39 rotations per second
= 23.5 RPM
Conclusion: The maximum RPM of the system will happen with a split-reel core, and is 170RPM. The minimum RPM system will occur with a full standard reel, and is 23.5RPM.
We should be able to use these figures in other calculation - IF THEY ARE CONFIRMED. Please take a look and let me know if my head is on straight.
I have been busy on another project, so l am a little behind. I will post as I read through each topic, so excuse me if someone has posted past my thoughts elsewhere. I am not a theory person, but I can offer what I have abserved from experience.
The old Prista film cleaning machine is very similar to the Kinograph design.
It uses a capstan drive PTR (eliminates sprocket damage issues) on a CM31D17NZ8C Leeson 90V 1750RPM 1/6 H.P. 1.8 A motor to drive the film and set the film speed, which is measured by an identical PTR on a rotory encoder. This would by like your centre drive in your just previous video. You can incorporate the encoder as your counter and display actual film speed.
Then it uses 2 D50-90 90V DC 1/5 H.P. PM motors from US MOTORS as the hold back and take up motors that you can then control individually to set and vary torque and tension to match the film rate speed of the drive. I realize that this is an old design, but most (a lot at least) web systems use this design. The problem here is that these motors are very large.
I would suggest using servo motors for the unwind and rewind motors, which enables you to use the feedback for torque and tension to match the feed rate of the centre drive motor. These can pack a lot of power in a small frame nowadays. Or stepper motors, if you can overcome their problems.
Not saying that this is the best design for this application, but I’ve been reading a lot on web control design, and the 2 zone, 3 motor design seems very popular…
John
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Accounting for the weight of a full reel, can someone figure out minimum H.P. to start from a dead stop?
@Maker awesome! Love the specific specs. Exactly what I needed. Thanks. Will look up those motors.
Re: servos - seem pretty expensive. If you have any recommended sources, let me know. It will help, as you say, to have HP/torque requirements figured out first.
I ordered some materials with which I hope to make torque measurements and from there, HP/torque requirements. Will update this weekend, hopefully.
Starting my rough set up. Seeing how large it needs to be. Will start drilling when motors are decided.
Is all film a standard thickness(not considering shrinkage)? Then it would be easy to calculate reel diameter at any given moment by adding 1* film thickness to every rotation of the take up reel and subtracting same from hold-back reel. Then the film angle is easy to interpolate and can be used for film tension. I think. Correct me if I am way off base.
Vertical reels for Kinograph is not a good idea in my opinion because their centre of gravity cannot be controlled, leading to probable tension variations as they rotate, which could be a real problem for heavy reels. Horizontal reels will not suffer from this.This is not a problem in movie projectors because they use intermittent frame drive with plenum loops driven by sprocket rollers on each side of the gate.
As for bearings that will take huge loads with low friction, why look at small ones? I propose to use tapered bearings used for auto wheels. They are widely available, cheap, and are not likely to be greater than about 60cm in diameter which is in scale with a film reel 14" dia. Moreover, some of them have built-in oil seals. Designing suitable flanged drive shafts to fit these bearings is also not a problem in this day of 3D printing. I recently designed one that incorporated a constant-velocity flexible coupler to overcome slight misalignment in drive motor shaft.
Jeff
Hi Jeff,
If you are referring to my pics, I was just sizing things up to decide on a frame size. Definitely going to be vertical. Thanks.
Not sure if 2 drives is a good idea. Specially geared and so close together. Using a gear, you would have no control over the tension in between the 2 gears, and at such a vital spot.
Being so close together, the slightest motor adjustment is going to be a large change. I think the hold-back motor, (unwind motor) would be better at controlling tension through that whole first section. From unwind hub to drive hub.
In this hat same video, I noticed that the “pretend” film was A wrap and then B wrap at the take-up (rewind) roller. Just a slip of the marker, or is that motor able to reverse wrap?
Not at all. I was following this thread and noticed the discussion was veering away from horizontal, primarily based on reel bearing loads. My experience with vertical operation is that eccentric centre of gravity can be a problem, and you can see a bit of this in the videos that Matthew posted earlier, so I thought I would add my voice to the discussion.
Jeff
Okay then. I think I was getting confused on my horizontal vs vertical orientation. The build started out horizontal, switched to vertical, and now I don’t know where we are anymore. I see what you are saying about centre of gravity, but if the spindle, hub,platter, and reel are all fixed well with good quality parts, wouldn’t you have problems in between the reels trying to resist gravity? It seems that almost all web winding machines are vertical. Could you be more specific about the issues? Are most machines vertical just to keep the footprint small?
Just to clarify on my comment. There are 3 main orientations that I can think of, not counting tilted back. The first 2 are pretty similar. That would be axis aligned through 90 and 270 degrees, along Z axis, or perpendicular to sea level. Next would be 0 through 180 degrees, parallel to sea level, but still on end. The 3rd would be laying flat on the X, Y axis. Or flat on sea level. Like a compass is held, N,S,E, and W all level. I know, a little over the top. Just
@Maker Not sure if I understand the question. Film moves left-to-right in the pic, at least that is the assumption in the design.
16mm and 35mm film can be on a reel or on a core. I see that there is no platter on the Kinograph so far. Is that something that will be added later?
A-Wind and B-Wind - This is the emulsion position of the film. There are two possibilities, just as there are two sides to a piece of film. Camera original is B-Wind. A print struck from it will be A-Wind. This is because film is printed emulsion against emulsion.
From, Glossary of film terms, www.joelschlemowitz.com
Sorry that the drawing is off 90 degrees. Replace wrap with wind.
Right now I have no plans to include a platter - but welcome any designs that include that modification!
M
Hi all,
Sorry for the delay in updates. I have come very very close to making a final decision on take-up and supply motors. I am just waiting for one more shipment. More details below.
WORKING NOW
Right now I have a stepper motor system working with enough torque to power the entire system:
Motors
Power Supply: 48V @ 6.3A (enough for two motors)
Controller
Logic: Arduino Uno
I have not incorporated any feedback loops into the system for speed control yet. My only focus thus far was to find a motor with enough torque and to test it with a full reel on the take up side and then again with a full reel on the supply side. I’m adjusting speed manually with a potentiometer attached to the Arduino, which in turn changes the speed of the stepper.
I will post a video of the system working this week.
ON THE WAY
I found out that pancake servo motors might be exactly what we’re looking for. They have a slim profile, do not require a driver (PWM signal for speed control), and are built for continuous, consistent linear motion. They are used for tape recorders and the like - so they’re perfect, especially if we ever decide to incorporate our own sound reader.
I found one supplier in the UK (see PDF attached), and one in China. For the take-up/supply reels, we want something like a GPN12, and for the capstan we’d be able to get away with a GPN9.
GPN12 UK cost = $420/ea. So there’s your bad news.
Right now, the stepper motor setup is around $145 each. But I want to do a comparison with both systems so we have an informed choice before we move to the next phase. Once I have the pancake servos installed, I’ll send a video of both running and ask for your feedback.
GPN12 SCS.pdf (188.7 KB)
Matthew,
I purchased an old bell and Howell super8 projector from Ebay and was able to harvest enough parts to get a good start on a Telecine machine.
I plan to drive one of the sprockets from the BH proj. with a stepper and arduino uno. The stepper mtr is a 200step, NEMA 17 and per my calculations I will run it in microstep mode, 29 steps to advance one frame, pause, trigger the camera then repeat. the camera is a 5mp imaging camera with electronic rolling shutter and I am using a 12mm s mount, M12 lens. Unfortunately, there is no trigger on the camera.
If this works, then the resulting frame shots should be exactly super8 mm size with no sprocket holes to deal with.
I plan to use Debut software from NCH which will trigger the shutter.
I will be counting on the repeatability of the stepper to move the film one frame and not get out of sync with the window in the frame. Do you have any experience with steppers? Am I expecting too much?
Thanks
Johnc