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Thread: Homemade Stabilizer for use in aviation?

  1. #1
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    Default Homemade Stabilizer for use in aviation?

    I'm being asked to put together some video footage of key places on Lake St. Clair from the air. I really do not have a big budget so I been thinking of ideas. A gyro stabilizer would be amazing, but its defitinly outta budget.

    Ok, for camera we have a Sony Handycam DCR-SR42. Its a low-end camera but its fine for what were doing. I'm not rulling by out a HV20 ethier, but the SR42 is what we have already. I'm going to buy a set of 3rd party lenses (telephoto, wideangle, depolariser.) The thing where I am running into trouble is I need to minimize the shaking of the plane from the engine. Since we need to be compact, this is my idea. I have a nice tri-pod that can shrink down to size. My idea is to attach sponges to the bottom of the legs. and add weights hanging from the center. My bet is it will hold down the camera to the plane since the whole setup without is just a few pounds. The weights will hold down, and the sponges even under the compression will deaden the vibrations.

  2. #2
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    Your friends for this are 'Inertia', and 'Isolation'

    The mass of the camera is very important, and it's not 'light' that helps, in fact the heavier the better. The reason being that the more mass the camera has the more it resists changes in position. Gyroscopic mounts work so well because they generate 'apparent inertia' which is kind of like increasing the weight of the camera big style, and then some! Of course they also resist attitude changes, their primary function. So that's the Inertia bit. There is a consideration about where the weight is, but I'll get back to that.

    To reduce the outside influences we need to 'Isolate' the camera from the forces trying to make it change position, generically known in industry as 'Resilient mounts', or 'AVM's (anti vibration mounts).

    So, first off, make your rig as heavy as you can, simple, but it's the isolation that causes problems. Your suggestion of using sponge is fine, but every material has a 'resonant frequency', a natural frequency of vibration. Generally the harder the material the higher the frequency, so your sponge is going to be well down on the scale. That's ok, but there's a problem with this, in that assuming your aeroplane is a piston engine, there's going to be vibration from the engine, and the propellor, and if that vibration is divisible into the resonant frequency of the sponge, it will still vibrate the camera. These vibration harmonics can be a real pain, particulalry with continuous influences like an engine.

    Something like a microphone shock mount could help, but they are designed to damp out single incidents of shock, such a mount will still allow vibration to kick off in sympathy to a regular source like an engine albeit rounded, so no good there.

    OK, all very techy, so what's the solution?

    For me it may be simpler than you think. I have a regular need for camera stabilisation which is not met by regular steady cam mounts, the reason being I need to make rapid tilting adjustments for my chosen subject, and none of the steady cam setups allow the degree of movement needed, I'm talking from slight tilt down to pointing dead upright to the sky in a second or two here. They are also dependent on using both hands, and as I have to run after my subject that's just not comfortable. The setup I use employs a directly interactive resilient mount of immense sophistication. My arms!

    OK, a lot of talk there, for now then take a look at this first trial of the mount in its current form, in particular the bit where I'm following the guy in the buggy towards the end. If you're still interested I'll expand on the mount, how it works, and how it might work for you, bearing in mind that it's low cost (there is a link in the description on this video). I have better tests on film, but need to render out short sections if you care to see them. Whilst this is not a vehicle mount that you need as such, it is relevent in my view. Keep your eyes on the ground to get a perspective of the amount I'm running around.

    Steady Cam Trial
    Last edited by Jerry Hill; 08-30-2008 at 07:54 PM. Reason: typos

  3. #3
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    Those are very impressive results. If I hadn't read your post first, I'd have assumed you were using some very expensive kit. Just goes to show what a bit of knowledge, a bit of ingenuity and, I guess, no little amount of practice can produce.
    Presumably a classic case of necessity being the mother of invention.
    Last edited by TimStannard; 08-30-2008 at 06:57 PM. Reason: spelling
    Tim

  4. #4
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    Yeah it's not bad for a home job, hopefully you can see what I mean about the angles changes, hence why gimballed mounts are no good for me. You do need to develop 'The Ninja Run', but all steadycams need that no matter how fancy they are, I borrowed a true Steadicam rig once, with gyro stabilisation, it still needed care, and Schwarzenegger strength! But sginificantly the point is that SMDSkata's need may be met by using himself as the shock mount, it just needs inertia to aid a steady camera. In the confines of an aeroplane perhaps a monopod version would work, though these are less good at stibility in the vertical axis, for reasons of a lack of spread of weight.

    If he wants to put the cam on the wing, then no use at all of course .

  5. #5
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    Quote Originally Posted by Jerry Hill View Post
    ...If you're still interested I'll expand on the mount, how it works, and how it might work for you...
    Who wouldn't be? That's a very good demo indeed....

  6. #6
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    Yeah maybe, I'm just thinking that it would be wrong to expand on this particular setup in this thread when it might not be appropriate for what he wants to achieve, or more importantly the physical issues he may face in an aeroplane.

    What may interest folk whilst we are waiting for him to get back, is this vid which shows the mount in use in a very awkward situation, in close woodland, it's very difficult to get some rigs through this sort of growth, and a lot of it was shot whilst running through the woods and other slippery and muddy uneven ground, so it's not super smooth by any means, but usable I think.

    Latest Steady Mount trial

    Perhaps a seperate thread? The limits of image posting here makes presentation of this tricky, so I may add to my articles pages with something instead. The place exists because of this kind of request following my building a camera crane.

  7. #7
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    Sorry I've been very busy latly.

    I am very amazed. Your film looks like you were using a glide cam.

    I like the idea, but I really am not sure how much of a difference it'd make in the air. Being in a light aircraft, you are very prone to turbulence. Its very similar to a ride in a very old wooden rollar coaster.

    Heres to videos from flying on a very calm night.

    (This is my smoothest flight in a general aviation aircraft I've ever been in - Cirrus SR-22)

    (This is the plane I mostly likly would be flying in. When I am not zoomed in, the films not to bad, but soon as Im around, i'd guess 8x, it shakes. Also it seems there was interference, or my cameras auto audjust make those white flashes. I forgot to do the contrast on this one, so its not as rich feeling, just deafult video.)

    I picture your mount, and actually any kind of device would only eliminate shaking for the operator. Could I use somthing else to weigh the other side down, cause I dont have a DSLR like that laying around :P

  8. #8
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    Right, good information, I can work with that.

    First off, do you have image stabilization turned on on your camera, like 'steadyshot' on a Sony, because if you do, turn it off when using steady mounts. These work by repositioning the image. they zoom in slightly to give some room around the edges, then shift the image around as necessary to stablise it. If the image movement exceeds the degree the frame can be moved, it jumps suddenly to catch up, the net result being those dramatic hops in the picture every now and then. Steadyshot is good for absorbing hand shake, but not for big movements, where it actually makes things worse! But that's an aside.

    It strikes me that for part of your shooting you don't need a steady mount at all, your problem on the internal shots of the instrument panel etc is arising because of the camera being decoupled from the aeroplane. What you actually need to do is to ridgidly mount the camera so that is moves with it.

    So why am I so confident about that?

    Well, I've been through a similar issue some years ago, and the good folk on the Home Built Stabilizer forum jumped through hoops with me to try and over come the problem, we looked at gyros, isolation, shock mounts et al, but the answer laid in direct coupling. To prove the point look at this (at the start I'm going over very rippled sand, so it shows another problem I'll come back to) The thing to watch here is not the horizon alone, but the kite buggy itself in relation to the camera too: Kite Buggy Camera

    What you're seeing is the camera moving with the buggy, so the horizon jiggles about a bit, but the buggy doesn't so much, just the front end shifting as the buggy flexes. I proved this by fitting accellerometers to the buggy and the camera, and comparing the signals received, this showed the camera moved slightly in relation to the buggy, but not much at all really. So bracing your camera in the aeroplane will solve the internal shots issue. The only thing you need to be wary of, that I touch on above, is that cameras with mechanical recording systems, be it tapes, hard drive or DVD's. rely on rotating parts for them to work. In a regular MiniDV, or digital8 type camera for example there's a heavy rotating recording/playback head. It's heavy to make it's rotation smooth, but this weight resists rapid changes of direction, so with a direct coupled camera if the vibration is extreme, and I mean real jarring knocks, it will upset the recording head and a glitch appears, hence the initial wobbliness in that video above. The way to get around this problem is to simply use a solid state recording, but now we are talking fat wallets so we'll avoid that for now.

    To fix the camera do not rely on the tripod mount alone, in this video the camera is mounted like that, and the result is appalling. The reason for this is that most tripod sockets are simply not man enough to hold the camera in these circumstances, bear in mind this beach was smoother than the first one! First Buggy cam trial

    The tripod mounts in cameras like ours are fiddly little things which are usually fixed to a thin chassis in the camera, sometimes it's just the plastic case, and after that film it actually fractured the casing on that camera. So, the way around this is to clamp the cam completely. I can't show you know because of link limits, but basically I made up a huge 'C' type clamp which holds the cam bodily, that's what was used in the first vid shown, and still is to this day. On decent cameras the chassis is made from an aluminium casting, and that is very much better, but then it's still not perfect and the subject of the mount on to which the camera is fixed comes up and so on and so on.

    So for your internal shots I'd find something that will allow the camera to be jammed up against the headlining of the cockpit. This can be done with some form of firm foam, not a sponge, more like camping-mat material, maybe sandwiched to make up the thickness. Use your tripod legs on the cockpit floor to sort that end, and wind up the centre column to jam the cam up against the foam on the headlining. If the headlining is 'false', i.e. it's suspended, use something to spread the load over a bigger area, a sheet of plastic or something.

    For your window shots we are back to the steady cam mount. Without knowing what space you have you may or may not be able to use a similar rig. The reason I use another camera is that I'll always have that with me, so it simply saves carrying extra weights, it might as well be there serving to add to the inertia than sat in a camera case. I've subsequently rigged a remote switch so that I can take stills whilst shooting video, but that's another story.

    The idea is not only to make the rig as heavy as is managable, but to spread the weight as much as possible. So why is that?

    Let's take a ball of lead, say it weighs 10 lbs. It would be, what, maybe 3 1/2 - 4 inches in diameter, for the sake or discussion lets say 4 inches. hold the lead ball upright, like a shot putter as he mounts it to his chin, and rotate your wrist back and forwards. You'll be able to do this reasonably easily.

    Now take a piece of wood, say 2 inches square in section, but long enough to be the same 10 lbs. Hold that in the air horizontally in the same way, and without having to actually do it you can imagine that there is no way you can do the same rotating action at the same speed as the lead ball.

    The reason for this is that the same weight is spread out over a much much bigger distance, and so we have what's known as the 'flywheel' effect. Where the effort required to move the mass is much greater, conversley the effort required to stop movement is also much higher, like a flywheel. Our piece of wood will take more effort and longer to make it turn, and more effort and longer to get it to stop and change direction.

    So this is what we want to build into our steady mount, and that's the simple reason why the legs are splayed on the tripod I use for my steady cam mount. It allows a fairly lightweight tripod to resist rotating in the vertical axis, which brings me back to why monopod style steady mounts are not so good. They often use a simple barbell weight on the bottom end, this provides the necessary horizontal axis stability, but does little for vertical axis. If you look at a steady cam mount such as a Glidecam, they put the weights on a 'T' Shaped bar on the bottom, this is entirely to spread the weight out, make that a three position one like a tripod and even better, you just have to ensure that the operator doesn't hit the legs whilst moving. If you extend the splayed legs you get a massive increase in stability, but of course the overall weight is just the same.

    By adding as much weight as you can bear to the whole rig, like my added camera, and by ensuring that the position you hold the rig is in a place that puts the control in the centre of mass, your arm then acts as a decoupling device, and the mount looks after itself. Holding it in this place is important, if you hold it too high, then the weight will be greater under your hand, and that will resist movement more that the parts above the hand, so it will try and stay where it is when moved so the cam will tilt accordingly, if you hold it too low, then the opposite. I often get a low angle shot by simply inverting the whole thing, it's just as steady, but only a few inches off the ground.

    So all being well I've given you some things to think about:

    Couple the camera to the aeroplane as much as possible when the subject is within the plane itself, so that the camera moves with it, using 'steadyshot' is ok here.

    Decouple the camera by using lots of weight spread as far as possible and by isolating that mass from the aeroplane to shoot objects which are outside of the plane, and turn steadyshot off.
    Last edited by Jerry Hill; 08-31-2008 at 06:51 PM. Reason: typos

  9. #9
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    You've obviously been working with these ideas for some time and no doubt discussed them many times. The result is some very clear explanations that even an idit can understand. Added to this we have the benefit of your real world video examples. What a great conrtibution you're making to the forum.

    Now perhaps I can ask a question . How do you manage to post so clearly and concisely at 3.56 AM???? (I realise Devon is to the West of Surrey, but last time I checked it was in the same time zone)
    Tim

  10. #10
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    Hehe. I dunno, I seem to think more clearly at night, so at the weekends I shift my waking hours. I generally only like six hours sleep, so I'm usually up till about 12:30 AM on weekdays too.

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