DIY hydraulic tilt

[Robert Bobson]

I want to add a manual hydraulic tilt to my crane head.

But don't have any experience with hydraulics:

Are there any existing hydraulic control systems that are used on another machine/vehicle that I could adapt?

I'm thinking I basically need two hydraulic cylinders connected with a hose filled with fluid. when I manually push/pull on one cylinder, the other will move the same amount?

[Cole McDonald]

Very cool idea! I personally think it's a bit overkill and perhaps a little more prone to "complicated to fix on set" failure... but I really like the concept.

A parallelogram with fixed verticals will do the same job... I even went so far on mine as to just use a cable for the top of the parallelogram to eliminate tons of weight: works like a champ.

But from a strictly DIY geek POV, awesome! Add some gears and lasers and it gets even better ;)

Practiacally, I would imagine having a lever on the operator end could get some nice smooth tilts with this kind of setup though.

[Warren Kawamoto]

head[2].wmv - YouTube

As you see in this video, hydraulic tilt and pan IS possible, but doing it with finesse and control is very difficult. For my taste, such movements are too jerky for real productions.

As for hydraulics, if you have matching pairs of cylinders on both sides, your input and output should theoretically be the same as long as your lines are totally free of any air bubbles. I think the key to having smooth control is is to have friction free bearings at your pivot points. Any friction there would cause a visible jerk. Please let us know if you can achieve this!

[Alastair Traill]

Hi Warren,

I have given a little thought to this idea in the past but decided that electric motors were much more practical. Electric motors can be connected by simple plugs, sockets and flexible cables etc. Hydraulic fittings are heavier, much more expensive, any fluid loss is messy and will need to be replaced if troublesome air locks are to be avoided.

Below is a picture of a small motorised head. It could be run for quite some time on 4 AA cells but in practice I use rechargeable batteries. It has a useful speed range achieved by using a variable voltage source (0-~5volt). Its power supply is via a 10 core cable that can be lengthened or shortened by plugging in or removing an extension as required. The other cores are utilised for different purposes, for example the curved fitting shown contains an infrared emitting diode that it directed to my camera’s infrared sensor.

http://www.dvinfo.net/forum/images/attach/jpg.gif

[Warren Kawamoto]

Thanks Alastair, I have a Jimmy Jib system that uses wired motors sort of similar to what you have pictured. I have not found any other control system that does smoother pans and tilts....yet. But setup is rather slow and meticulous. I would love a system that sets up faster, providing it can match my current ability to execute perfectly smooth pans and tilts.

In a practical hydraulic system, the hydraulic lines must always be intact, even upon breakdown. I'm thinking that this could mean faster setup time, but it would also add a lot of weight to the rig since all of the lines and cylinders are always full of fluid. At this moment, the Advantajib is the only jib that I know of in the professional market that utilizes hydraulics. If there is any other on the market that is fast to set up and does perfect pans and tilts, I would love to try it out!

[Robert Bobson]

I'm really just interested in being able to tilt the camera down a bit once the crane is at it's apex.
I've found some nice pneumatic actuators with a 13" stroke that I think I can fill with a light oil. should work nicely. I'll post again when I have something to show.

[Paul R Johnson]

pneumatics are very different from hydraulics. You can't compress fluid, so action is immediate, and there is direct feedback. With air it's very different. I'm currently doing a job with a 5m tall giant - that has everything controlled with pneumatics and it's very tricky. No problem with actually moving, but if the item you are moving has variable 'weight', for example as it rises up, over and then down, your initial pressure compresses the gas, then it starts to move, and then if the force required changes, as it goes over the top, the pressure is too high, accelerating the movement, which then needs pulling back. My operator has taken about 20 shows to be able to predict when to pull back, so the movement is smooth. If you want to do this, use fluid - not air.

[Robert Bobson]

Yes, I do want the immediate action. But no one has yet to tell me that it is okay to fill a pneumatic system with light oil and use it un-pressurized. does anyone know if that would actually work?

[Paul R Johnson]

Looking at the works of my air system, with all the valves and joints, I'd suggest the big problem is that air systems work on very narrow bore tube - so the viscosity of the oil, even light oil suggests to me there could be problems, with narrow bore you have higher pressures - so the push in to seal connectors might need proper unions?
Just a guess because I'm by no means an expert, but we experience a few blow outs, when one of the heavy arms goes over the top and the weight suddenly compresses one of the actuators. You could always try with water and see what happens.

[Chris Soucy]

Originally Posted by Robert Bobson

does anyone know if that would actually work?

I think it fairly safe to predict that such an action is going to leave you with a gooey, messy, unusable pile of junk.

Hydraulics are so popular because of their ability to deliver huge amounts of grunt and work with constantly varying loads and pressures without losing work rate.

They are exceedingly difficult and expensive to engineer for slow starts and stops however.

Pneumatics are exceedingly good at working with constant loads but require a much larger footprint to deliver a comparable amount of grunt as hydraulics although engineering slow starts and stops is much easier.

Electrics can deliver as much or as little grunt as required using gearing and matching load rates and are infinately easier and cheaper to engineer for variable start and stop times. They are also infinately smaller devices, are self contained and require little in the way of connection to the power source compared to either of the other two.

Unlike either of the other two, there's nothing to leak, either.

I think Alastair nailed it with his dinky COG mount tilt unit, can't get a lot more compact than that.

Match that with a sophisticated controller allowing the setting of infinately variable start (attack) and stop (decay) rates and you'd have a unit smoother than anything a human could do.

I think the whole hydraulic thing fits nicely in the "it seemed like a good idea at the time" round filing cabinet.

Just my 2 cents.


CS

[Cole McDonald]

I've made mine cable driven and works well. Much cheaper than an electronic version, certainly cheaper than an hydraulic version would be, the test footage on the bottom is with student crane operators who hadn't practiced with the system before the shoot. Like every other camera system, it's a choreographed dance using these things - plan for it if you add one to your arsenal:

http://yafiunderground.com/Video/BTS_Crane.mp4
- I've since added a better tripod and lazy susan bearing for smoother motion
- Added the control system I mentioned I would be adding, it ended up a bit more complex than I had thought it would, but the pan/tilt system only ended up costing about US$50 to build on the end of a US$50 crane, so total expense here is ~US$100 and 3 days of build time (because I had no plans).

Control System Details:
http://yafiunderground.com/Images/pan-tilt.jpg
http://yafiunderground.com/Images/pan-tilt-marked.jpg

In Action:
http://yafiunderground.com/Video/pan-tilt.mov

Sample footage (First shot is on a dolly as well):
http://yafiunderground.com/Video/Crane-move-1.mov
http://yafiunderground.com/Video/Crane-move-2.mov
http://yafiunderground.com/Video/Crane-move-3.mov