Crane stabilization schemes

G

ggrantly

Veteran
Confession 1: At heart I'm a doItYourSelfer and in fact used to build yacht hardware. Though at this point, I'd rather avoid re-inventing the wheel. For the time involved, I'm usually better off buying if it is available.

Confession 2: I'm an unsteady crane operator.

I am the proud owner of a Kessler Crane and while I don't use it too much, it's a nice piece of kit to have. I would use it more, especially with the shortest tip, if it was a bit more stable starting and finishing movement. There is (for me) an annoying vertical bump at the end of most every movement. This isn't terrible, but it is enough for me to think about improving it.

Question: Has anyone ever added a gas-strut shock absorber to a smaller (prosumer) crane like the Kessler? Any thoughts on this would be appreciated.

I also intend to improve the brake which is IMHO pretty lame and is the cause of a slight vertical bump even when using the crane for horizontal moves. But this is more straightforward than adding struts.

Edit: I might have said this a bit more clearly. The brake is just a bit weak in the knees and needs some increase in the thickness of the strut.

If anyone from Kessler monitors this thread, please speak up.

TIA
Grant
 
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If you have a motorised gimbal, have you considered attaching it to the crane? Assuming it doesn't exceed the weight limit.
 
It would take a pretty big (expensive) gimbal to fly my PX270. That would certainly be a thought for something really small like a GoPro. Sometimes my load exceed 10lbs. The crane is rated for a bunch more than that even with the 12ft tip.

My goal would be to be able to effectively use the 5.5 short tip in an interview-studio situation to introduce some movement.

Grant
 
I don't understand what you plan to do with the gas shock.

I made my own 16' jib with motorized pan/tilt head. If you are not satisfied with the performance of the crane, it may be due to insufficient bearing and joint design. Every moving point on the crane should be rock solid with no give whatsover and operated with ball bearings. Anything less than that will give compromised performance. I don't know the Kessler design so I can't comment on the issues you are having.
 
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Paul F said:
I don't understand what you plan to do with the gas shock.

I made my own 16' jib with motorized pan/tilt head. If you are not satisfied with the performance of the crane, it may be due to insufficient bearing and joint design. Every moving point on the crane should be rock solid with no give whatsover and operated with ball bearings. Anything less than that will give compromised performance. I don't know the Kessler design so I can't comment on the issues you are having.
Click to expand...

As stated, I plan to use a shock absorber to reduce the slight vertical bump I get when starting and stopping a movement. Just like in your auto, a shock absorber reduces or softens uncontrolled movement.

I don't plan to add ball bearings to my crane.

Here is a link to the Kessler Crane site so you can see what I am working with. If you scroll down a bit you will see a photo of the crane attachment to the Hercules Video head. Note the brake assy which is a flatbar with a milled slot on the near side of the photo. The only problem with the brake is that the slotted flatbar should have been upsized in thickness; it just needs more stiffness. As for the shock assy, I was thinking of adding the shock absorber on the opposite side of the brake.



http://www.kesslercrane.com/kessler-crane
 
I don't see how the gas strut is going to fix the problem (then again, I don't really understand what is causing the bump either). If there is some design flaw causing the bump, I don't think a shock absorber is the best answer. You should fix the problem at the source, not cover it up. But maybe the shock will do the job and is the easiest solution. I can't tell without more information.

While I don't understand what the shock absorber solves, it also would have to be rock solid with very smooth articulating joints or it will be no better than the problem you are trying to solve. I don't know what you mean by a bump, but I'm guessing you mean tilts have an abrupt start and stop. That would indicate that there is drag in the bearing system. The bearings may be undersized for the job or their mounting is lacking something.

If you can demonstrate the problem, maybe we can help with the solution.

A thicker brake bar is going to be difficult to fabricate without a mill. Do you have a solution?
 
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I used to own a machine and fabrication shop where we did mostly aluminum and stainless projects and I do some solids modeling work for fab shops in my present business (besides video). I can do the work, or get it done, no problem.

You imply that the only solution would be an entire redesign of the crane to add ball bearings at each tilt or pivot access. That would require a total redesign and extensive rework of the crane which isn't going to happen. The amount of work involved would, no matter the result, not be worth the effort. I would replace the crane. In this case, the crane is entirely useable, this is only an irritation which might be improved. Kessler's are used widely and well thought of in their price range. Are there any cranes you can recommend that are designed and fabricated as you suggest in the $2k range that would be perfectly smooth?

Sorry if you can't understand the nature of shock dampening on movement such as this. Think about the gas strut that opens the the hatchback in a car, except without the spring, dampening the motion in each direction. I was seeking info if anyone had added or other wise seen a dampening scheme out in the wild.

Regards,
Grant
 
Ok, so you want a damper to add some drag to the movement similar to a tripod. Got it now. The strut is clever. That's a lot easier than a drag plate. I've not seen this.
 
I would first look at the jib arm and make sure it isn't flexing from inertia at the beginning and end of moves. I'm guessing this is really where the problem is located. You may need to rig up some cables to pull the arm up to keep it from flexing.

If it is really in the brake, then an air spring should help.
 
Using the Kessler 12ft tip adds a cable truss to the system. The 5.5' tip is so relatively short that it is plenty stiff.
 
Are you applying a break at the end of a move? Is the break not just to keep the device safe when not in use?

I don't think a break should be applied mid shot - maybe for a lock off shot but IMO mainly not even then.

Also remember using a "small" jib is an art that requires a fine touch like operating a steadicam.
 
No I wouldn't apply the brake mid-shot and after the crane is balanced, it is only there for holding the unit in place.

The way I am wanting to use this crane (besides the traditional longer tip roles) is for use in a studio environment, with the short tip, and operate the cam directly with my hands on the cam. I can swivel the whole rig side to side and even some vertical if the brake is off. So in my case, when I initiate and finish such a move, I get the little bump. Actually, the beginning of a move isn't really a problem, it is the finish. As admitted in my confession at the beginning of the thread, I could be a better operator. But as careful as I can be, and after several years of use, I still get the little bump...call it a snap-back. So I was imaging a cylinder that could dampen that out. It's not like the Kessler is a piece of junk, far from it. I am wanting to make a decent piece of kit better.

Grant
 
Stiction in the bearings? Or the brake sticking slightly? You might need a second person to operate the jib so you can listen and look around the pivot area and see/hear what might be sticking.
 
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