Hi Dom. I'm listening.cameratech wrote:Carl, I appreciate your curiosity, I really do, but you're not listening.
I don't believe I've said anything about the pull down being for a Super8 cart. Be that as it may I don't think gaining insight from a claw design for a Bolex will be entirely useless for Super8. The process of solving one problem can easily become useful in relation to whole range of similar problems.The H series pulldown design won't work for a Super 8 cartridge, because it acts from the wrong side of the gate.
Thanks Dom. So during forward motion the Bolex forward claw isn't rubbing up against the pin at all. It's depending entirely on spindle (pivot) friction to ensure it swings around and engages the film. Cool. I can certainly see that friction happening. When I remove the gate it certainly wants to swing out (towards the film). And for the swing back it again relies on friction not to disturb the film. And I notice there is a side pinch during swing back, I assume to further guarantee the film isn't bumped during swing back.The pin has no relation to the forward claw movement when it runs forward, it only acts as a stop when the movement is run in reverse. What keeps the claw engaged with the gate is the friction of the turning spindle, which needs to be strong enough to keep the claw pressing against the gate, but not so strong that it pulls on the film as the claw pulls back (in conjunction with the pressure plate tension).
I can see what you're saying. If the camera is to perform in both forward and reverse, then one of the arms has to be disengaged completely during either direction. With the gate off I was inferring the film plane too high, pushing both claws against the pins, so that both pins became involved.
Yeah I don't know if a plastic claw will work either. Will find out in due course.Even the cheapest movie cameras used metal claws - perhaps plastics technology wasn't as advanced as today, but I don't think a coarsely manufactured plastic movie camera claw is worth investigating.
I don't know if I'm missing any particular point. I'm certainly not claiming to know anything in particular about any particular camera. I'm using what's called "propositional logic" which is where you (or someone else) proposes something- regardless of whether it is true or false - such as the arm has a designed back - and then you test it to see if it holds. The aim is not to reproduce the Bolex design or any other design for that matter, small or large. It's to test out a theory (any theory), and in the process get a better idea of the problem space from which one can then design one's own's mechanism.You're missing the point that the main design factor with small gauge film movements is not the claw shape or movement curve, which tends to be quite basic, but the various tensions involved - claw spring, pressure plate and take-up.
If I misread the Bolex, as I've done a number of times, it doesn't really matter. The testing (computer modelling) I'm doing, or help from yourself, ensures it gets corrected. Or ensures it will work whether it reproduces the Bolex, or invents an entirely different design altogether. The computer modelling is not be read as an explanation of anything. The computer modelling is a testing of the various propositions. Or a "trial and error" process, as my preschool teacher liked to say. It's both a creative and technical process. You allow yourself to be creative in the proposition, but become technical in the testing. If I can come up with a design that isn't the Bolex design - but works - that's just fine. Or if it reproduces the Bolex design that's fine as well.
For sure. I can fully appreciate that.With professional 16 and 35mm movie cameras the pulldown curve becomes much more important, but there are also so many other factors involved.
cheers
C
