DSLR KAP..take a deep breath..

A series of quick mods to the Brooxes ‘basic’ rig and the D70 is committed to an AutoKAP flight. The all up weight with a stock 28mm lens came in at 1.1kg when everything but the basics is stripped off the rig. That’s only 100g over what I fly anyway: this is going to be easy! Against my usual practice of using a pendulum I accepted the Picavet suspension on weight grounds and just hope the flat weave Dacron will not let me down. The D70 has very limited remote control options so for testing a rubber ‘finger’ (as neither of us was prepared to remove an actual finger for the job) was taped over the shutter release button with the camera set in continuous mode. With the rig turning every 5 seconds the frame rate might just match the servo trip rate…

On a grey overcast day with freezing fingers I hooked the quick clips to the line of the Lifter, it was pulling well and had found a steady place in the sky, I have got used to its mad short line behaviour and know once it’s up it tends to stay up…with the shutter taped securely down and the camera clicking away, the picavet running freely and the pan servo jerking the rig around 30 deg every 5 seconds I wave it goodbye…the Lifter takes the load and Clive feeds out a big bight of line, the rig leaps into the air …twang…clunk:

388 inverted shots later I get to see what has happened: the jolt has loosened a wing nut and the mass of the camera has swung the tilt platform upside down, obviously this is going to take some sorting out. The tilt pivot point is well below the CoG of the camera. The moving mass of this camera is capable of causing serious problems, it will easily override a tilt servo unless I can gear it down or perhaps I will need to use an industrial robotic servo. To save weight, space and tape I order an infra red (IR) shutter remote from James Gentles, and at the speed of the night mail crossing the border it arrives next day ( thank you James!) and it works a treat..sadly there’s now no wind at all so I’ll have to wait to fly it again. The taped shutter shots are encouraging though; even in poor light the DSLR resolution is clear.

The D70 shot this on ‘Auto’ at:1/160th sec, f6.3 ISO 400. I have tweaked this extract from the shot above a bit in Lightroom:

Since KAPiNed10 I have been changing my view of flying a heavy camera like this, my first instinct with KAP has been to keep the weight to a minimum but as I get better at matching the right kite to the wind I am getting more confident about what I can lift and manage balanced with my bodyweight (I am a 70kg weakling).  I cannot really describe the immense joy of experiencing flying a kite and camera in balance; it is something like walking on air.  I had assumed more weight would require a bigger kite and bigger problems controlling it, this is not necessarily the case if I can get the load, lift and kite matched from a flight of kites.

I have been not a little fearful of flying the D70, it’s clearly is not designed as a lightweight camera and I recall Steve Cole’s words on the matter well: ‘flying a DSLR is not a good idea when dealing with heavy landings’; it’s always going to be a camera I put before a steady and consistent wind, it will never have anything to do with the ‘light variable’ stuff!

The ‘Basic’ rig is powered by 4xAAA rechargeable batteries so I was advised to place the IR emitter as close to the receiver as possible to make the most of the modest power available.

The round spot below the right hand thumbwheel is the IR window.

http://www.gentles.ltd.uk/gentled/shutter-zoom.htm

Next: video relay, RC pan and tilt, done it before with a compact, how hard can it be with a DSLR?

About billboyheritagesurvey

Heritage worker
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16 Responses to DSLR KAP..take a deep breath..

  1. jokerxl says:

    Super!
    I very nearly clicked on “buy” on a second-hand D70 last week but thought better keep it as lightweight as possible for now, until I get confident with it all.
    Is there not some servo/motor unit available that will drive the pan-axis steadily (and slowly) around constantly, instead of jerky movements in degrees, I mean? Then the intervalometer could just do its thing as it revolves, less stress on the servo when working with the greater mass of a DSLR.

  2. The pan servo/shutter business is all ok, Peter shipped a fully functional 360 deg set up with the Basic rig. The motion is jerky but I have managed to sync the shutter with the wobble so that it shoots once the motion has steadied (it was a case of trial and error but a 5s step did the trick. The big problem is the tilt. The camera is too heavy to be held in place by a servo on the axis set up like this. I will need to balance it all very carefully to get a neutral load as it turns; there’s no quick fix, it will be a case building a new rig I suspect.

    I’m going to see how I get on with a fixed tilt to get used to it and then start the build.

    Scott Haefner got it sorted:
    http://scotthaefner.com/kap/equipment/rig/

  3. Ramon says:

    Quite the story, Bill!

    The thing that makes me feel a bit uncertain about this setup is the fact that this camera’s weight could become too much for the servo and the direct picavet suspension. The servo is all plastic. As you can see, Scott also uses a (1:1?) gearbox and I’m quite sure I’d do the same if I was about to use heavier cameras. Just a thought :0)

    • Good point Ramon, if this rig took a pasting the servo case would split and it would be game over! I have the pan gear of a ‘deluxe’ rig and that’s what I’ll use for the build. This is really a case of ‘putting a toe in the water’ I couldn’t fly this set up for any serious work without a vid link or RC shoot, pan & tilt.

      I don’t trust the Picavet either; it’s suspension lines wear at a shocking rate: this one has only done a few hours and the line is furry already. I remember what Scott Armitage said; ‘a Picavet works by friction…’

      By the time I have got this under full control the weight will be a problem, I was very pleased to get it airborne as a 1.1kg payload but it will be closer to 1.5kg using a deluxe rig…and that feels awfully heavy!

      I’m going to have to go down the LiPo battery route and start swapping out aluminium for CF if I’m going to get the weight down.

      I’m assembling the pan gear as we speak!

  4. Clive Hollins says:

    Hi Ramon and Bill. I don’t see a problem with overstressing the pan servo with the heavy camera. Essentially the inertia in the camera and peripherals will be taken up by the flexibility of the Picavet suspension. On the down side the picavet ‘string’ will of course wear out faster because of more friction due to the extra weight and possibly the settling time after a rotational movement.
    In a normal Picavet using a fixed tilted camera the Picavet tends to take care of the camera stability, but with Scott’s gyro stabilized servo there will be much more wear on the string if the camera is not balanced about its horizontal balance axis. Worse still the servo will be fighting the imposed torque and drawing more current from the battery and will probably jitter causing even more wear on a very short section of the string.
    With an automatically focusing lens assembly the balance point will change as the lens assembly motor readjusts the focus and this will add slightly more wear to the string.

    With the existing Brookes rig, it is impossible to get the D10 far enough back to meet that axis balance point. Additionally in Brooke’s design the position of the servo axis of rotation had to be a compromise to meet the majority of cameras out there on the market at the time it was designed. Any ‘improvements’ we do from here on in will be to customise the suspension for the camera in use.

  5. Clive, If you follow the path of the load in the pic at the top of this post you’ll see the problem; all the weight is suspended through the servo bush: it would only take a modest shear force to seperate the self tapped 2mm bolt from the nylon bush: that’s it, nothing else supports the load! Horrible when you think about it!

    • Clive Hollins says:

      Quite right Bill, but as it is, the camera tray is a long way from the suspension bridge piece. If the servo was mounted on the side and the web attached directly to the side of the tray then the sheer force on the servo side is considerably reduced. If the weight of the camera and attachments was considered a problem then the servo could be mounted on the suspension bridge using a 1:1 spur gear. The tray bearing(s) could be beefed up to cope with the weight safely. Scott Armitage’s GS1 can be adjusted to reverse the direction of travel though spur gears as in my rig for the horizontal (roll) stabilization.
      It would require a complete redesign of the rig though.

  6. Peter says:

    I have some new parts in stock. They are not yet on the website as that is under reconstruction.
    The new parts are made out of sandwich carbon so very light, very strong and big enough for a D70 or similar.
    Bill: I’ll send you some pictures later.

  7. Jon Blake says:

    Obviously i know nothing… Perhaps this rig does it, but wouldn’t it be nice if, once the kite and camera were air borne the rig travelled up the line. Here by making full use of the kites height. RGB may have an example from the boys own paper…

  8. Jon, the idea of the ‘ traveller’ has been around for quite a while, I like the idea of using wind power to push the rig up the line perhaps even getting the sail to double as a KAP ‘feather’ too. As it is height control is done by 2 methods: the natual rise and fall of the kite due to wind variation and the hauling of the line in and feeding it out.

    Meanwhile:

    https://billboyheritagesurvey.wordpress.com/2011/03/06/dslr-kap-how-hard/

  9. Tyler Olson says:

    Thanks for the post and nice to see experience lifting a heavier rig.
    Do you have any suggestions for a good lens? Which focal length is good? I am thinking of a prime lens to keep the weight down, but will 28mm be too wide?

    • Bill Blake says:

      On the D70 the 28mm prime works well at 20 to 30m stand off. I guess if you are going for the hallowed ‘full’ 35mm frame something like a 50mm would be the thing. Having got used to the balance between my weight, the kite pull and the rig I have found DSLR to be a lot less flexible than the small format alternative. I keep reverting to the Leica X1 which has a nice resolution to weight ratio. So far I have used the D70 as an AutoKAP ‘donkey’ to keep the weight down but I find using a directed camera much more effective than AutoKAP.

      • Tyler Olson says:

        thanks for the thoughts. the leica X1 should be a great camera for KAP. I am still considering sending up the 5D mark II. I realize it is going to be heavy but that is the camera I use and would like to put it to work with KAP as well. I like the full frame sensor and have tested the kite and line with the weight but still waiting to get my rig in order and see if I still feel the same way. I have a 50mm and a 16-35mm lens I am thinking of using.. just not sure yet which lens to balance the rig for.

      • If it was down to the choice you say I’d want the wider lens but really it dependes on what you want to get out of the viewpoint. I find, even at 60m a wide lens helps get your subject covered. On the other hand you owe it to yourself as a kite flyer to use the lightest lens you have! I flew the D70 yesterday on the rig shown in this blog. :
        it worked ok but I took 750 images of which only a handful are keepers and I failed to cover my subject….

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