Advice wanted, on making free-hanging windows rotate

[Jram]

A brief search has turned up little of use except threads about rotating gobos and windows operating systems...

 

The windows in question will be made of an as-yet-undetermined material, possibly wood or (in order to facilitate the effect) moulded two-part foam. Or any other material that will enable the effect to be achieved.

 

There are four windows, that fly in and out over the course of the show, 2 upstage and 2 larger ones downstage. The designer wants the windows to rotate without the actor having to do it, and preferably with the method unseen. Ideally, she wants them to be light enough to hang on catgut, although 2mm steel drifts may be what she has to live with, dependent on construction material.

 

So far, I'm thinking that we should hang two short bars (be it flat steel or wood) above each window. The top bar would be attached to the grid on spotlines, the bottom bar would be attached to the top bar in the centre with some sort of bolt or other fixture that would act as a pivot point. By attaching a rope to each end of this bar, and running both ends to the flyfloor, it should be possible (I figure) to move this bar upstage or downstage (think of the basic steering mechanism you would find on a home-made go-kart or box car.) The window would then be suspend from the lower bar. In this way, the window can be made to swivel from the flyfloor and so with no visible effort.

 

The problems I foresee in this method are thus: by pulling on the ropes to turn the window, there's a high chance that the bars would also move, and you would end up pulling the whole thing towards you rather than causing it to turn. The window will have to be light enough, and the pivot point strong enough, that the lower bar doesn't just snap off with the weight of the window. I'm sure there was another reason which may come back to me.

 

We are pressed for flying space due to other scenic pieces, swathes of fabric that block off three 2-metre spaces (ie the fabric is attached to a downstage bar, then the bottom is tied to a bar 2m upstage). Therefore the turning mechanism wil probably have to sit at flyfloor height, unless it is incorporated into the window itself. Incorporating it into the window means there would be part of the window which doesn't (or can't) rotate, as it would be supported at both ends by drifts of some description.

 

Using catgut run into the wings doesn't seem feasible for various reasons.

 

The windows will need to be able to stop at their new (rotated) positions, but will need to rotate back to their original positions to enable them to fly back out. The effect will need to be repeated throughout the show (on a constantly open stage, so no behind-curtain resets.)

 

Whenever people post on here they are usually berated for not providing enough information. I'm hoping I've provided sufficient but please fire any questions at me or mention any omissions.

 

We have 44 linesets, of which 30 are counterweights, the rest hemp. Dropping spotlines in is simplicity itself. Our grid height is 15.8m and the flyfloor is at 7.2m (we also have an intermediate flyfloor.)

 

So, while I try and work out how the hell to achieve this effect (it has been left to me to decide whether or not it can be achieved, but as the designer is a friend who's already had a less-than-perfect experience on this show I figured I'll try my best), any outside thoughts or previous Real-World examples would be gratefully received.

 

Thanks in advance.

[Jivemaster]

Mirror ball rotators have been good for similar purposes. There are battery powered ones and mains ones and SOME have a good rated load.

 

Someone will have to manually control the rotation to get the frame parallel to the bar for flying out. Beyond that there must be a way of driving a slow motor through a servo system with position encoder then the whole rise and fall and rotate can be automated.

 

Lots depend on the rotating mass of the window-frame Is there to be a film for the window pane.

[zonino]

how about a steppermotor rather than mirrorball rotator? similar to Brian's post about the panto clock here

[Jram]

Is there to be a film for the window pane.

 

No, the frame will be just that - a frame. No glass, perspex, film, other at all. So that'll lighten the load.

 

Thanks for your fast responses, I'll pass them on at today's meeting. If anyone has any further suggestions I'm very happy to hear them.

 

Thanks again.

[Tom Baldwin]

The main challenge I see with flexible hanging wires (be they steel or catgut) is inertia and momentum - i.e. whatever is twisting in the flys will move ahead of the window at first; the window will then move, probably overrun its intended position, and then oscillate about this position for a while before settling.

 

Have you considered Robe's StageBanner rotators - gives you the same control as you'd get with a mover:

Stage Banner

 

Possibly over-expensive (Hawthorn Theatrical list at £80pw), but if there's no time to build your own electronic system, these offer a ready made alternative.

[Jram]

Thanks. If anyone has any further suggestions I'd still be very interested to hear them.

 

The show doesn't go up until the end of May (22nd-ish) so we have time to wire or build or whatever. If anyone has any further (maybe non-electric)suggestions please add them.

 

Thanks again to everyone who has contributed so far, I'll offer these ideas up at today's preliminary design meeting.

[Tomo]

The big issue here is one of stiffness.

 

Regardless of what form of rotator is used, the backlash between driver and window will be huge!

 

You'll need to hang each window from two points as far apart as possible to minimise the problem, but you can't eliminate it entirely.

You may be able to use long thin steel rods such as welding rod to make it stiffer - it's about 2mm dia, so just as visible as steel drifts and can of course be painted.

 

All movements have to be fairly slow and deliberate - if the director wants the windows to 'snap' into position then forget flying them, they'll need to be stage-mounted.

If they need to gently 'drift' into new positions, then it should work.

 

As far as physically moving them is concerned - heavy-duty RC servos may be your best bet as they are fairly cheap, very reliable and include position feedback, which would be lacking in a stepper-motor.

Suitable wired interfaces exist, either back to a simple joystick or controlled via DMX, although it may be cheaper to build your own as the protocols involved are very simple.

[Jram]

You may be able to use long thin steel rods such as welding rod to make it stiffer - it's about 2mm dia, so just as visible as steel drifts and can of course be painted.

 

All movements have to be fairly slow and deliberate - if the director wants the windows to 'snap' into position then forget flying them, they'll need to be stage-mounted.

 

Welding rod may be the way to go - if we use a central piece and weld it to a piece of steel, then build the window around that, then that could act as the pivot point... just thinking aloud but yeah, thanks for that! It may come to it that an actor would then have to manually move the windows but it's all very much up in the air and open to suggestion.

 

Oh, and yeah, I realised pretty much immediately that any fast movements will translate into jerky movements over a distance.

 

Any more for any more?

[Jivemaster]

If the frames can be sculpted out of a sheet of foam polystyrene then the rotating mass should be a minimum even when coated for fire retardance.

[dbuckley]

You could use RC style servos to provide the turning power, use three 1mm support wires, two for power and one for data. Or just little DC permanent magnet motors, then just two wires, but you'll have to control them manually remotely, as thre no positioning sensing. With a servo you can drive them off a computer, so the start and stop speeds are controlled so reducing shocks.