what its the function of the droptime ?

[Eric Fletcher S.O.C.]

I totally agree with Jerry. I don't understand what's with this Eric's primal urge to pick on some people like this.

You both are right, but talking about slightly different things.

Now imagine a 100 feet long superpost. Yeah, I know it's not possible, but for the sake of argument- imagine! If it's droptime would be 3 seconds, then who on earth would be able to control that? Imagine, or calculate, if you're able cause I'm not, how much mass it produces!

If you had a 100ft long superpost and had a 3 second it would feel just like your normal sized superpost as long as you changed your drop time with the gimbal position vs adding weight.

 

Jerry, yourself and Alfeo don't seem to get that. With the same camera weight it doesn't Matt how long your post is, drop time is drop time. 30 degrees a second is always the same speed.

 

What you all are confusing is camera weight. Post length has nothing to do with drop time, camera weight does. What Jerry should have said is that with the different camera weights vs rig sizes its harder to compare drop times, and then even that is misleading

[Jerry Holway]

What's so annoying about all this, Eric, is that you often to respond so aggressively to someone else's opinion: "You really want to stick with that answer Alfeo?"

 

Can't you just explain what you believe and let it go without all the personal stuff?

 

Regardless, and back to the question at hand: I suggest that anyone simply go ahead and try to control a 100ft rig (or, okay, a 5 or a 6 ft one) with a 3 send drop time and see how it feels to you, as that is all that matters.

 

We do this exercise at every workshop when we work with superposts, and it's never a surprise that drop times must be increased to get the same feel.

 

So many of us have tried to explain this in so many ways, but it all gets down to the feel and response of the rig, and that's a snap to test.

 

If you don't have a superpost rig or a Merlin, then this may all be of little interest to you. But if you are particular about drop times, and want to know how others set up their rigs, then you should be comparing apples to apples and not just seconds. Be sure to compare the length of your rig to length of their rig. And get out the old stopwatch and a video and count frames - your seconds may not be his or her seconds (this amusing variable is in the archives somewhere).

 

I don't even do the old drop test anymore; one can feel how bottom heavy the rig is when supporting it horizontally and adjusting the gimbal. Of course, I vary the length of the rig a lot, and the inertial qualities - monitor in or out - and play a lot with my bottom-heaviness (drop time) depending on the shot (lots of tilts, hard accelerations on vehicles, slow moves, etc.), so any particular number of seconds or even a standard feel is not my cup of tea.

 

Jerry

[RonBaldwin]

Jerry, you can't fool me. We have already established who you really are...either Eric's alter ego or sitting next to him on a sofa this very instant, high-five'n, beer and laptop in hand giggling at the thought of a 3 second drop with a 100' post! You Taoist mofo! Or is it mofos!?

[Ants Martin Vahur]

 

I totally agree with Jerry. I don't understand what's with this Eric's primal urge to pick on some people like this.

You both are right, but talking about slightly different things.

Now imagine a 100 feet long superpost. Yeah, I know it's not possible, but for the sake of argument- imagine! If it's droptime would be 3 seconds, then who on earth would be able to control that? Imagine, or calculate, if you're able cause I'm not, how much mass it produces!

If you had a 100ft long superpost and had a 3 second it would feel just like your normal sized superpost as long as you changed your drop time with the gimbal position vs adding weight.

 

Jerry, yourself and Alfeo don't seem to get that. With the same camera weight it doesn't Matt how long your post is, drop time is drop time. 30 degrees a second is always the same speed.

 

What you all are confusing is camera weight. Post length has nothing to do with drop time, camera weight does. What Jerry should have said is that with the different camera weights vs rig sizes its harder to compare drop times, and then even that is misleading

 

Eric, I'll agree to your statement, that "a 3 second drop time is a 30 degree per second drop time" even though physically it's slightly different, because there are acceleration and centripetal forces involved, but for the sake of this argument it is not utterly important.

 

After some time of going through the old physics formulas, which some I have forgotten and the others knew briefly, I have come to two conclusions:

 

1) It is impossible by far to emulate the same effect with super post as with "normal post" when wanting to do tilting (or rolling (dutching)). Because the masses are so spread out, you would need to apply excessive amount of force close to the gimbal to do a tilt or roll move, regardless of the same drop time in seconds per 90 degree or same tangential speed between the "normal post" and mega-super long post.

 

2) It is possible to emulate with (mega-super) long post the same effect as with "normal post", if you're only doing a spatial movement and not going to tilt (or roll (dutch)).

That is only if your tangential acceleration stays the same, meaning that longer post has longer drop time in our language. Meaning spreading masses out from the CG in proportion.

 

My two cents..

[Ken Nguyen]

Simple math:

F3d3 = F1d1 + F2d2

Where:

F3 is the force to pivot camera weight about the gimbal (pivot point)

d3 is the distance of camera weight center of gravity to gimbal.

F2 is the force to pivot bottom load about the gimbal.

d2 is the distance of the bottom load center of gravity to gimbal.

F1 is the force to control/operate the sled (the feel).

d1 is a distance from gimbal center to where we place our fingers.

F1 is also a function of drop time.

We set the drop time so the sled is bottom heavy.

The force to put the sled back to balance is also F1.

In neutral drop time, 0 second, F1 = 0, without controlling, F3 = F2.

Let set the condition for our situation.

- Camera weight is the same.

- Feel force (F1) is the same.

- Distance from fingers to gimbal center (d1) is the same.

Then,

F1d1 = B (constant/the same) = how we want to feel/touch the gimbal.

F3d3 = B + F2d2

B = F3d3 - F2d2

Since camera weight is the same, F3 is the same.

The only variables are F2, d2, d3.

So, to have the same feel, we have to change F2, d2, d3 depending on the sled length.

If d2 is longer, F2 must be less, or d3 must be longer. The case of longer sled.

Less F2 means less weight on the bottom load.

If d2 is shorter, F2 must be increased, or d3 must be shorten. The case of shorter sled.

Larger F2 means more weight on the bottom load.

I need to take my kids out for holidays.

Will be more discusses (if needed) after vacation.

Cheers,

Ken Nguyen.

Here is the link to the diagram: http://www.flickr.com/photos/98401677@N06/

[Alan Rencher]

[JobScholtze]

[Quaid Cde Baca]

Hmm. I think Eric is right. We extend the post and adjust the gamble in most cases in order to achieve our desired drop time since the drop time is what relates to the desired feel/ effect of the sled we want while operating.

Heavy camera /high shot. Long post to = a decent drop time

Light camera/ small size. Short post to = a needed drop time

[Jerry Holway]

BTW, if you have a three second drop time starting with the sled held horizontal (90 degrees), you will have a three second drop time with the sled held at 45 degrees or 30 or any other angle.

 

Sort of gives us a hint at what reality is.