20 Oct Stability – Lesson 1
Cable cams are very unstable by nature. You have a rope (or more than one) suspended over a large distance. Wind, motor jolts and vibration, head shake and rope pulley bounce all cause the system to become unstable. All of this translates onto camera. High tensioned ropes and high tech stabilized camera heads make a big difference but as usual the devil is in the details.
One of the very first things we discovered here at STSCC when we started playing with cable cams years ago was that shake on the trolley could be caused by vibration we couldn’t even see with our naked eye. We would be walking along beside the trolley and we could not see any vibration, meanwhile the DP would be complaining about shake they could see on the monitor. Extremely small frequency vibration would be humming down the drive rope causing the trolley to oscillate, even though it looked perfectly stable. This kind of problem can be quite annoying as linking the vibration to a cause seems like looking for a needle in a haystack.
In a system like this the very first thing that needs to be done is removing all shake and vibration from every sheave on the rigging. Clipping a loose carabiner to an off the shelf pulley is really asking for it. Once operating you can easily see the pulley shaking up and down causing the drive rope to bounce and voila, the trolley is shaking and bouncing all over the place. Even a $350,000 gyro stabilized head can’t deal with this kind of movement.
If you can lock the pulley into place, with no ability to move, even the slightest in any direction, you are well on your way to getting rock solid stability on your camera trolley. We invented the FISH BLOCK to solve this problem. A multi axis device that can be rotated or tipped to one side to keep the pulley in perfect alignment and then locked solidly into position so that it can’t move.
The image shows two Fish Blocks attached to a speed rail. A low profile anchor built specifically for TED Talks in Vancouver BC.