The Z axis problem.
This one has been a tough nut to crack, but I believe I am finally on the right track.
I want the camera to move up and down. This means I have to have a mechanical solution to solve this. If I go a traditional Z axis setup like on a CNC machine, the equipment I need to raise or lower the camera a specific distance must equal that distance + room for motors and frame.
Let me try to unpack that a bit. Lets say I want the camera to raise/lower a maximum of 20 inches. This means to use a leadscrew or ballscrew (think our chronos rails) the system to raise/lower the camera must be at LEAST 20 inches. You have to have room for the motor and frame, putting that closer to 24 inches.
In the image below, on the very top is a motor that turns a ball screw, or lead screw. Think of these as highly accurate and very well made threaded rods. There is a carriage with a nut that the rod goes through. As the motor turns, it lifts and lowers the assembly with the cutter. These sorts of systems allow for VERY accurate motion and they can lift a LOT of weight.
So if I wanted to use a traditional Z axis and get 20 inches of travel, the Z axis assembly would be at LEAST 20 inches. I could Probably make it 24 inches.
The pan/tilt system is about 18 inches itself (rough guestimate). since it would have to attach to the carriage and hang BELOW the Z axis assembly, that would mean at MAX HEIGHT the camera would be somewhere around 42 inches from the ceiling. When the ceiling in my studio is 86 inches, you can start to see the problem.
The shooting envelop is the area in which the camera can be moved. My goal is an area 5ft x 5ft by 20-30 inches.
This means the set SHOULD sit roughly on the low end around inches above the ground, and when the camera is fully retracted up, it would only be around 3.5 feet off the ground.
So that means the traditional Z axis is no good for this project. I have to find a way to maximize the travel, keep the accuracy, and have enough vertical travel for my proposes.
So I played around with several ideas. One was an idea of a scissor jack style setup.
If I could flip that upside down and attach it to the X/Y gantry, and attach a motor to the screw that would allow maybe 18-20 inches of travel with only needing 6-8 inches of space for overhead. Thats not too bad. However these are heavy duty systems developed to lift cars, not high precision devices used for motion control. I am skeptical it would be an easy modification, and then there is the fact that the motion would not be linear. When it is just slighty extended moving 4 threads would drop the camera much father than when nearly fully extended. This is still a possibility but I am not really excited about trying to integrate it.
So then I moved onto an idea of creating some sort of a telescoping rig. And I THINK I may be onto something.
I found some heavy duty drawer bearings. They collapse from about 25 Inches to 12 inches, and are intended for drawers that hold up to 500lbs. They are very heavily duty and have virtually no slop or play in them. Click Here
If i get 4 sets, and double up so i have 1 set attached together, for a total of 4 sets, and get the right framework, i can build a telescoping system that is 12 inchs when closed, and about 38 inches when fully extended. This gives 26 inches of vertical travel and keeps the camera much higher when retracted. The camera would sit about 30 inches from the ceiling at full retracted height. That puts the camera at about 53 inches from the ground, close to 4.5 feet up.
How to raise / lower?
Easy enough. I plan to attach one of my Chronos HD rails to the main carriage overhead, and use a teflon belt attached to the carriage of the rail which will hit a pulley at the end and go to the base of this telescoping structure. As the carriage on the chronos rail moves out, the system drops down, as the carriage moves in, it will lift the system
I think this is going to work out fairly well. The parts have just been ordered, I am excited to get this up and running 🙂