Testing and Modifying a Crane/Jib

andyharris

Finally got all the bits for my crane today.

I'm happy with the tripod and the jib, but perhaps on the verge of sending the head back.

It turns out that these things are not as easy to operate as I thought, it took more than an hour just to get acceptable footage. Anyway I realised that you need a bunch of other little bits to make it work, so I've set about cutting up bits of carbon fibre and making plugs for LiPo batteries and the like.

Here's first efforts:

Andy

andyharris

ToDo List:

New wider bush that seats the head to the jib end properly so that it is level WRT to the tripod.
Build tray to hold:

Monitor
GlideCam controls
LiPo battery
(This is mostly done as of this evening)

If I don't give up with the head (it was £789):
1. try adding a longer control joystick -- the difference between slow and fast is a fraction of a millimetre
2. Junk the given controls and build a proper PWM set.
3. if still fed up, junk the motors and use 5:1 steppers
4. if double fed up -- rebuild in carbon fibre and use steppers, place the battery on the head and use standard radio control gear (Spektrum DX7)

andyharris

If the head is hanging from the jib all the controls are reversed! So perhaps I need to build in a set of changeover switches.

Unless someone knows any better, it would appear that the next price point for heads is circa £3K so maybe a custom panel isn't such a bad idea.

Here's a picture of the side rail ready to take the batteries and controls -- this is a longer job than I thought!

andyharris

Today's mods:

Found that the connectors could be reversed (they have two location notches),

Added some tiny paint blobs for the 'normal' orientation.

Mounted the Controller and Battery (its just a 1000mAh LiPo but it ran for a couple of hours today and still seems fine)

Here's a photo.

andyharris

Have really given up on the Glidecam head motors, they cannot hold a camera and lens still unless it is perfectly balanced. Then the issue is once there is some tilt there is no longer balanced. Have ditched the DC motors in favour of Stepper Motors which have a lot more torque.

Here's the current state of the prototype:

peternap

Pretty neat video! That's out of my league. I;m using an 8' ProAm.

kronstadt

Isn't all that load a bit too much for the Manfroto sticks? I've built my own extending(telescopic) Crane for around £80 and thought of getting 717 sticks to hold it, but it's max load is stated as 6.5kg, while my crane+weights+gh13(with DIY matte-box +FF)+fluid-head can easily be over 10-15kg.

Since I don't use tripods in my cinematography style, I ended up getting one of those industrial heavy duty STANLEY tripods. The drawback of that is the lack of ballhead - not a biggie, cause I just level the tripod by extending one of the legs, and then the crane is perfectly level.

andyharris

@kronstadt

The Tripod is a 545GB with a 100mm bowl. The Artes doesn't actually use the bowl but clips neatly into the top - so I have the same issue - levelling by adjusting the tripod.

The load is certainly going up, however the original DC motors and gears were heavier than the steppers.

What is pushing the weight back on again is having the control gear on the head. The drivers weigh in at 300g so thats 1.2Kg that needs to be added to the other end and therefore an overall gain of 1.5Kg. The control gear needs to be on the head because of the probability of destroying the drive FETS if the motor gets disconnected. We've been thinking about writing a limit into the software of 540 degrees of turn. But for the moment we have D connections that simply pull apart is the rotation is too far.

I'm finding that I need to do a fair bit of planning of shots since I use the tripod for both locked off shots and the crane. I'm looking around for another tripod just to service the crane so Stanley might be a good source.

Cheers ....

kronstadt

Yeah, Stanleys are awesome as far as handling of weight is concerned, but don't expect any bells and whistles and ease of use that video camera tripods have. It's just a heavy duly tripod that is desgned to take the load and hold it. Normally they are quite costly (can go as high as £100 or more), so you might want to get other brands - search for "survey tripod" on eBay. But every now and then Stanleys pop up with a special offer. I picked mine up (Stanley 1-77-163) for just £27 on eBay + £6 P&P. Make sure that its head is flat!!! (because some of them come as dome-shaped and you won;t be able to level your crane on it). And it can go quite high too. And works great on a dolly track - very stable.

Mounting things on it can get quite awkward. Since my DIY crane is based on a caster wheel I attach it with a M10 bolt and a knob that cost me another £3. It still takes me about 1-2 minutes to set it up, meaning, to get the knob on the M10 bolt. And it's the part of the process that I hate the most (although it's a whole lot quicker than setting up Kessler or EZ-Jib etc).

But now I'm working on mounting my DIY slider and (why not) the fluid head and the camera onto that Stanley (for static shots), so what I'm thinking of is securing a Giottos MH631 quick release plate to the Stanley's head, which will hold all those items, interchangeably. I'm just not entirely sure if mounting a crane on a Giottos MH631 is a very good idea. I'll know better when I get a spare £75 to purchase 3 Giottos quick releases.

andyharris

So, I finally made all the various modifications to the GlideCam head.

Now its silky smooth using stepper motors with 26:1 gearboxes: http://www.active-robots.com/motors-wheels/bipolar-stepper-motors/3318-42bygh40-m-160-4a-nema-17-bipolar-26-1-planetary-gearbox-stepper.html

We're using drivers set to 128 microsteps, which means that we can get 200x26x128=665600 steps per revolution. The other key advantage is holding torque, now the head stays where its put!

We're really pleased with the noise reduction - this was much better than expected.

And whilst we were about it we add button to reverse the sense of the joystick, this means that the head can be mounted either way on the jib and the joystick controls still make sense.

On reflection was it worth it? Well the head cost £789 and I must have spent £700 on the modifications.

So here's the test of the modified version

mk47

I dont like the fact that the construction hangs directly from the motor axis like that. It would be much better if the axes would be separate constructions and the motors would move them using gears.

kavadni

@andyharris, that's awesome .. the latest test :)

What are the controllers and joysticks? Are they from the Glidecam head?

andyharris

@mk47 --- Yes we did consider this, but since the gears are enclosed in the housing they are less noisy. We hung a good 10Kg from the head and it seems perfectly fine - no change in sound. I'd had a look for internal diagrams so that I could work out where the the thrust is absorbed -- I don't have any answers to this.

@kavadni --- Andy Stephenson, the engineer who did the mods has a background in building industrial models and flying RC. He had a old but posh Futaba transmitter hanging about - this became the donor for the controls.

Someone asked me somewhere about the circuit diagram, I haven't got this, but here's a video that has block diagram.

As an aside this video took more than 8hours to render, there must be something about using Motion 5 to create a 3D space as a background for chroma keyed stuff:

https://www.youtube.com/watch?feature=player_detailpage&v=5gP4aDZuuog

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