Single or dual purpose projector, which is more gentle?

Forum covering all aspects of small gauge cinematography! This is the main discussion forum.

Moderator: Andreas Wideroe

mattias
Posts: 8356
Joined: Wed May 15, 2002 1:31 pm
Location: Gubbängen, Stockholm, Sweden
Contact:

Post by mattias » Fri May 24, 2002 5:23 pm

> The increased radius compensates for the minimal increase in mass by providing more leverage

look, you've alreay agreed that my math is correct, and that a "very large reel" is indeed harder to turn, so surely you must realize that there must be a breakpoint somewhere, where the increased weight becomes more important than the increased leverage? where would you say this breakpoint would be?

/matt

Guest

Post by Guest » Fri May 24, 2002 5:44 pm

mattias wrote: look, you've alreay agreed that my math is correct, and that a "very large reel" is indeed harder to turn, so surely you must realize that there must be a breakpoint somewhere, where the increased weight becomes more important than the increased leverage? where would you say this breakpoint would be?
More importantly, you've already admitted that increased leverage overcomes any minimal increase in mass and that it would take a reel that had miles and miles of film to illustrate an appreciable difference. Where do you think an appreciable breakpoint would be? Miles and miles of film? And what would an "appreciable breakpoint" be considered as it relates to this discussion?

I would say that if the film shows no wear and the claw shows proper registration, then the math is academic because the end result, from the projector's point of view, is that a large reel that is full is easier to advance than a small reel that is full. Otherwise it's like pointing out that one guy is 7 foot 1 inch and another guy is only 7 foot while standing in a crowd of pigmy's. Relative to the crowd, the two guys are basically the same height; they're giants. A technical difference? Yes. An appreciable difference? No.

Further, while the full reel nearly empty TECHNICALLY is harder to turn than a small reel nearly empty, the difference is not enough to merit comment as it creates no ill effect on the film, which is the ENTIRE basis for this discussion. Not what is mathmatically correct as illustrated by a reel with "miles and miles of film" on it but, rather, what the operational reality is for a typical reel with only 400-1200 feet on it that has doodly-squat mass to overcome, full OR empty.

Again, your math is correct but only extreme examples amount to an appreciable difference, here. Now, if this were mongo 35mm film reels with considerable weight and mass, I think that would be a different story altogether but we're not. We're talking about super 8, which has minimal weight and mass issues relative to the power available by a typical projector, sprocketed or not.

I'm not arguing the math. I'm arguing the reality.

Roger

mattias
Posts: 8356
Joined: Wed May 15, 2002 1:31 pm
Location: Gubbängen, Stockholm, Sweden
Contact:

Post by mattias » Fri May 24, 2002 8:33 pm

> More importantly, you've already admitted that increased leverage overcomes any minimal increase in mass

yes, if the reel is "almost empty". add some film to it and it will get easier and easier to turn, but not forever, or a "very large" reel would be extremely easy to turn.

> and that it would take a reel that had miles and miles of film to illustrate an appreciable difference.

no, i said that with miles and miles of film the difference is obvious. this is a normal way of solving scientific and engineering problems. if you can easily establish how things are at the extremes, you're a lot closer to a complete solution, even if the situation you're examining isn't near the extremes at all.

> Where do you think an appreciable breakpoint would be?

like i said: around a 70 mm radius.

> Otherwise it's like pointing out that one guy is 7 foot 1 inch and another guy is only 7 foot while standing in a crowd of pigmy's.

but a full reel weighs several times more than an empty one? maybe my english is at fault here, but by a "full reel" i don't mean a 400' one, but any reel with as much film on it as it can take.

> Further, while the full reel nearly empty TECHNICALLY is harder to turn than a small reel nearly empty

i'm talking about the same reel, emtpy or full. the lever is the radius of the film on the reel and has nothing to do with the size of the reel.

> I'm not arguing the math. I'm arguing the reality.

exactly my point, and reality hasn't got much to do with leverage, torque, mass or math. it was you who brought the concepts of leverage and torque into the discussion. to me it seems obvious that just the force required to overcome the friction in the gate is a lot higher than the force required to pull the film from the reel.

/matt

User avatar
S8 Booster
Posts: 5853
Joined: Mon May 06, 2002 11:49 pm
Real name: Super Octa Booster
Location: Yeah, it IS the real thing not the Fooleywood Crapitfied Wannabe Copy..

Funny

Post by S8 Booster » Sat May 25, 2002 12:28 am

The only major problem is an undampned pull of the reel due to the mass of inertia if the pull is undampened (considering that in theory the reel stops each frame). The difference between a full and a empty reel might not be too big due to the leverage/mass/movement as calculated more times here but the mass is placed further off the center of the reel at an empty reel than a more filled up reel and the rotation (°) of the reel is much bigger per frame at an empty reel than a filled up reel. The stacato pull is much worse at an empty reel than a "70mm" filled up reel.

The wear on the advance system have to be minimized down to a very low level not very far from a sprocketed drive system when tension dampeners are used, at least for some projectors.

RGDS
..tnx for reminding me Michael Lehnert.... or Santo or.... cinematography.com super8 - the forum of Rednex, Wannabees and Pretenders...

User avatar
MovieStuff
Posts: 6134
Joined: Wed May 01, 2002 1:07 am
Real name: Roger Evans
Location: Kerrville, Texas
Contact:

Post by MovieStuff » Sat May 25, 2002 1:09 am

Hi, Mattias!

Well, I guess we'll just have to agree to disagree here. When I stated:
I'm not arguing the math. I'm arguing the reality.
You replied:
mattias wrote:exactly my point, and reality hasn't got much to do with leverage, torque, mass or math. it was you who brought the concepts of leverage and torque into the discussion.
But that came on the heels of:
mattias wrote: by a "full reel" i don't mean a 400' one, but any reel with as much film on it as it can take.
How can you say you are arguing the "reality" of the situation and also use examples of sizes and weights that would never apply to the situation? I understand that using gigantic examples helps clarify your point but such extremes would never exist and totally ignores the reality that the differences in mass and weight between full or empty 8mm reels doesn't add up to a functional difference; only a mathmatical difference. The fact that you have to use an imaginary gigantic reel to prove your point doesn't really help your position. If it made a functional difference in reality, then you could use a 1200 foot reel to prove your point just as easily as an imaginary gigantic reel.

But the fact is that it takes less inch/pounds (torque) to turn a typical 1200 foot super 8 reel at the outer diameter than it does a 50 foot super 8 reel at the outer diameter. Your math notwithstanding, you can prove this for yourself by taping a small button to a 1200 foot reel of film and let it hang and do the same thing with a 50 foot roll. The 1200 foot reel will start to unspool while the 50 foot reel will simple hang there.

The 1200 foot reel has more mass but that mass is clearly overcome by the increased leverage of the larger diameter FULL reel. Therefore, the original statement that Pedro made (which is the basis for everything that I've written), that sprockets are required because film is harder to pull from a larger full reel than from smaller full reel is simply incorrect. The larger the diameter the full super 8 reel (within functional reason), the easier it is going to unspool when pulled on by the same amount of force. At some point, the mass of the reel is going to resist the pull more, especially as the film nears the END of the reel, which is (again) why I clearly stated that a film advance has to work harder at the END of a roll than at the beginning.
mattias wrote: to me it seems obvious that just the force required to overcome the friction in the gate is a lot higher than the force required to pull the film from the reel.
Agreed! Which is another reason why it makes no difference if you have sprockets or not, as it relates to film wear or damage on a correctly designed and well adjusted projector.

Roger

mattias
Posts: 8356
Joined: Wed May 15, 2002 1:31 pm
Location: Gubbängen, Stockholm, Sweden
Contact:

Post by mattias » Sat May 25, 2002 10:31 am

by a "full reel" i don't mean a 400' one, but any reel with as much film on it as it can take.
How can you say you are arguing the "reality" of the situation and also use examples of sizes and weights that would never apply to the situation?
sorry, that wasn't very clear. by "any reel" i meant any existing reel, like a 50', 200' or 400' reel, but not a 400' one in particular. the "very large" reel was only to establish an extreme point of the function, and never to prove a point about a real situation. i still think the "breakpoint" is closer to an empty reel than one with miles of film on it, and probably somewhere close to a full 400' reel, as my math suggests. :-)

i'm glad we've finally agreed on the reality part though. it's been a rather interesting discussion.

/matt

User avatar
MovieStuff
Posts: 6134
Joined: Wed May 01, 2002 1:07 am
Real name: Roger Evans
Location: Kerrville, Texas
Contact:

Post by MovieStuff » Sat May 25, 2002 1:32 pm

mattias wrote: i'm glad we've finally agreed on the reality part though. it's been a rather interesting discussion.
Always! At least you stay on topic, which is refreshing. Some of the Googlites and Hostboardees could take a lesson on focus from you (and I ain't talkin' 'bout lenses, neither).

Lot's o fun.

Roger

PS: My wife occasionally reads our efforts and thinks we all need to get a life. I honestly have no idea what she's talking about, do you? :o

Roger

Post Reply