Motorized Jib

[caseyjames]

Hi.

Im looking to create a motion control jib. I've looked at a number of threads on the topic, but I haven't seen anyone approach a jib arm.

Is the torque too great for most servos or stepper motors? What are the complications?

I'm shooting with DSLR, so with the lens, thats only two pounds. Would 2lb at 8ft work? What about with carbon fiber tubing or something of the sort?

I'm not looking for precise repeatability, I'm just trying to get in the ballpark, for a green screen stage, with programmed operator-less control.

Any tips would be greatly appreciated. I have a little time coming up very soon and I really want to get this together before my gig starts up again.

Thanks,
Casey

 

[Paul F]

I don't think it is that difficult, but it may cost a bit. it really depends upon the reach. The taller/longer the reach, the more counter-balance required. Starting and stopping with all that weight is the issue; moment of inertia. It also depends upon how fast you want to start and stop. I'm building a very light jib with motor controlled head. It can reach to 16' high. With an AF100 on it, it requires 35lbs of counter balance. It is very easy to move. But that's because my hand is 2 or 3 feet from the pivot point. With motor control, you have a very short lever (the gears). So it will take some strong gears and motors to get that much mass moving and stopped smoothly.

The math isn't that difficult to determine how much force is required. I would suggest you go to a motion control forum (robotics forums and the like) to get some assistance. They have a lot of experience with this.

 

[caseyjames]

Thanks for the reply.

Ill check the motion control forums.

I figured inertia and torque would be the problem, but I imagine a 1lb on a 3' arm wouldn't require more than a $50 motor -- I guess Im looking for the sweet spot, hoping to get about 6' or 8' with a 2lb cam without breaking the bank.

Time to look into brakes -- it might be cheaper to use something other than the motor to dampen the energy.

I post back here if I find anything.

 

[Coach56]

Has anyone atempted to use a hydralic or pneumatic cylinder? I used to build animated Halloween decorations and it is amazing what you can do with an old convertible top pump and cylinders. You could need to use a relay and an adjustable microswitch to control where the pump started and stopped.

Just throwing that out there,
-Harry