Camera Jib Crane Information / Weight Reduction 101
During the pre-production of our feature Desert Wasteland, we created an ambitious shot list and were faced with a limited budget. With prop construction, and machining background, I took to designing and building all of our equipment as the shot list called for it. Just to list a few, we started with a shoulder rig, fig rig, heavy duty platform dolly, suction cup camera car mount, but the one piece of equipment we didn't want to do without, was the 21' jib crane.
There are many thing to consider when building a jib crane from the ground up, and many variables need to be taken into consideration. I suggest you build your crane in accordance to how much money you have to invest on material and counter weight- it plays a very important factor. There's a link for a simple lever calculator at the bottom that will help you determine counter weight. The position of fulcrum has great importance of how much of a load you can lift. The basic lever formula goes F=(WxX)/L, F= Counter Weight, W=Camera, X=Length between camera and pivot point of stand, L=Length between stand and counter weight. Pictured is an example of our current crane at Camera Hogs. Notice that the amount of force it takes to lift the weight of a 35 lb. camera, and crane head with a 21' span from pivot to camera, is 245 lbs. It is about $1.25 per pound for standard olympic weights and the counter weight alone could get expensive.
Extending the length of distance L, will allow you to lift a heavier load, it will also put your handles high when dipping into a ditch.
The ultimate goal is to take the stress off your lever as much as possible. To accomplish this, you can easilly do some custom weight reduction making sure you are minimalizing the amount of strain you are putting on structual integrity. In other words, don't go drill crazy and swiss cheese the entire crane. Let's talk about crane head weight reduction. The Camera Hogs 3 -axis crane head we currently stock to shoot commercials, motion timelapsing and music videos was originally desiged for up to a 21 lb. pay load. After a few modifications, I was able to support up to 30 lbs without overloading circuits on the joystick.
The crane head was well built and we were pleased with the overall torque, gearing quality, ramps and speeds. Overall, it's a pretty solid head with no wobbles or slipping when everything is tightened properly. I'll post a link at the bottom if interested in this specific model. The dutch roll can go more than 360 degrees when minimal wiring between the camera and base are used. It works great with wireless monitor and focus pulling systems.
The crane head was a bit heavy for what we had in mind and I began by drilling 1 1/2" holes on the 2 1/2"wide arm allowing about 1/2" of space between each hole. This took down the weight of the crane head signifcantly. For every pound you lose at the camera end , you lose 14 lbs. at the load end, your counter balance.
The other way of taking stress off of the lever is to build a cable suspending system, adding the jib to crane. There are a total of 4 tension poles, 2 upright and 2 for horizontal to reduce whipping. The photograph below shows the two upright- I believe they are about 28" in height. There is a total of 7 separetely cut cables, each with adjustment. You can't run a single piece from one end to the other- it defeats the purpose. I will attach a video so that you can better see the horizontal uprights and cables. I chose 2" aircraft strength square aluminum for the construction of the lever for this crane.
Calculator Link:
http://www.engineersedge.com/calculators/levers/page_levers_1.htm
3 Axis Dutch Camera Crane Link
http://stvfe.en.alibaba.com/product/1978082272221261612/camera_crane_3_axis_360_dutch_roll_head.html:
We hope that this was a useful read and hope it helps anybody interested in constructing or designing your own jib crane- whether it's 10 feet or 40 feet. Thank you from all of us here at Camera Hogs,LLC. Stay tuned, stay connected, and we will continue to post and blog about what we learn from our daily experiences. Please comment and share; if you find improvements, we'd love for you to share your ideas. Visit us at www.camerahogsllc.com and come see what we are all about.
