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View Full Version : Looking for Advice: Motor to Raise Screen/Pirate-Ship Sail



dmpeaceman
04-18-2017, 10:55 PM
So we were contacted by the casting producer for a certain big Christmas show (keeping excitement at bay), and we interview in June. So, I'm trying to put together all the plans before then, and start construction. I'm looking for advice on thoughts/ideas on how best to execute this.

I'm half way done constructing a pirate ship to put on our roof. However, I also want to have a MAST with a SAIL/SCREEN on it to project on to.

My show is theatrical. I like to progressively reveal new things throughout the show, and not show everything all at once, so I want the screen/sail to be hidden at the start of the show, then pull straight up, and have the projector (on the roof - behind the ship wall) project onto the sail.

See:

36354

There are lots of hurdles to overcome:

1) Wind - it will really be a sail, so I'll need to probably have a punch of U-shaped holes in it. We're in San Diego, so this isn't a HUGE weather issue, but enough to be cautious.
2) Motor Torque - unsure what size motor I need. I know this depends on the weight (which I don't know yet). What's the best way to right size the motor?
3) Stretch - it needs to stretch enough to be a flat "screen", but also stop at the right point when it reaches the top. Thinking of a physical stop switch when it gets to the right position - unsure how best to do this safely.

Really just looking for ideas/thoughts/cautions. I have the mounting sorted, and everything will be rock solid up there. It's just the logistics of moving the screen up and down, repeatedly, predictably, and safely - and of course, still being able to see the projection on it.

Thoughts?

plasmadrive
04-19-2017, 06:31 AM
You will have several issues to overcome on top of what you already know. The following is just my 3am opinion posting..

Wind will be a HUGE issue. you may consider a mesh instead of a solid sail with U shaped cuts. Other than that, when I did laser shows on a big screen, we used bed sheets, and strung clear fishing line back and forth from the side rails across the screen on both sides to keep it in place. We used side rails, you have a top and bottom so you could go up and down.. But your structure would still have to support the wind load. If a heavy wind happens the night you shoot, you could be in trouble if that is a main part of your show.

I don't know where you are but have you thought about rain? What if it rains? Will your material soak up water? If so, that could be a LOT of weight.

You will most likely need a pretty good sized motor/gearbox combo. When you are in a "show" you will have to pull it up rather quickly in order for the effect to be a "surprise". When they shoot the show, you want it to go smoothly if possible of course.

You may want to consider a double bar on the bottom and use a row of springs across the width from the screen bar to the main bar. That way you would have some give to allow for any motor coasting. If you use a DC motor and controller you can control it better and dynamically brake the motor when you want stop. You could also use a switch when you get close to the end to slow it down as it prepares to stop.

Make sure your projector has a high enough lumen output or it may not show on camera that well... or to your normal audience. Also make sure you have enough "keystone" adjustment capability in the projector to make the picture seem flat to the screen.

I personally would have a lot of control of the motor, and it's torque capability so that I could minimize the possibility of the motor pulling the darn thing apart...A relay or two for FWD/OFF/REV would not be my personal choice, though it could work. But that's just me.

You will need really good anchors for the guy wires. With that much sail you could have some amazing torque pulling on things. I'm not a mechanical engineer, but I have seen a lot of things go wrong with adventures like this just because of anchoring, or lack there of.

One more thing, I'm not sure how you will pull off a pirate ship as a Christmas item, but you may want to consider at least Christmas colors.... An opinion you didn't ask for, I know.

dmpeaceman
04-19-2017, 08:27 AM
plasmadrive,
Thank you for your well thought out response. I really appreciate you taking the time. I wouldn't have half the show I already do without this community, so thank you for being a part!


I don't know where you are but have you thought about rain? What if it rains? Will your material soak up water? If so, that could be a LOT of weight.

That's a GREAT thought I had not considered. You are absolutely right. I will definitely need to make sure the material does not soak up water. You probably just saved me a huge headache down the road!


You will most likely need a pretty good sized motor/gearbox combo. When you are in a "show" you will have to pull it up rather quickly in order for the effect to be a "surprise". When they shoot the show, you want it to go smoothly if possible of course.

Had the exact same thought on the gearbox combo. Good to hear confirmation on that.


You could also use a switch when you get close to the end to slow it down as it prepares to stop.

Another great idea! It also gives me another point of fail-safe.


Make sure your projector has a high enough lumen output or it may not show on camera that well...

Wow - yeah, you are right. I didn't think the lumen output would be a huge deal (since it's going to be dark outside), but yeah, it's gotta put out a lot of light to show up on camera, let alone to the crowd at a distance. Will have to crank it up.


You will need really good anchors for the guy wires. With that much sail you could have some amazing torque pulling on things. I'm not a mechanical engineer, but I have seen a lot of things go wrong with adventures like this just because of anchoring, or lack there of.

Yep - had the same thought. The reason I said it will be "rock solid", is that I have a bunch of extra material from a recent solar panel install on my roof. I have a whole set of mounting brackets that will allow me to anchor the sucker at multiple points on the roof straight into the roof rafters with big lags. Since I did about 34 of these already, doing 4 or 5 more should be a breeze.


One more thing, I'm not sure how you will pull off a pirate ship as a Christmas item, but you may want to consider at least Christmas colors.... An opinion you didn't ask for, I know.

It's a constant back and forth with me and my wife on this issue actually -- and you're right. I don't want to give anything away, but it should all tie together nicely with a Christmas theme, even though the ship itself doesn't scream "Christmas". The pirate ship will be something different at the start of the show, and "transform" into a pirate ship -- or at least that's my lofty goal. Go big or go home right?

I'll keep you updated on the progress -- and who knows, if all goes well, you might be able to say "hey I helped that guy" if you see us on TV! :-P

goverland
04-19-2017, 09:33 AM
Now we know where Santa really gets the gifts, he pirates them

Utimgr
04-19-2017, 10:48 AM
Many years ago...as I think...wow it really was that long ago, I designed a controller for a guy that wanted to be able to remote control the doors on semi trailers. He was using a 12VDC motor from wheelchairs. Someone was asking about this a bit ago for a train and I dug it out to give but he never got back to me. Non the less, I had a control box with 3 relays...main power, fwd and reverse, and it had a single button RF remote. The start and stop were done by timers, but I always thought he should have used limit switches. If you want to try that out?

The other way, thinking along the same lines, is to use a very small garage door system, one of the system uses a rail rather than a chain and is supposed to be very quiet. just mount it vertical?

Protege94
04-19-2017, 01:15 PM
What about a gravity type system? Have the sail in the up position and a guy wire on each side of the screen vertically and then when the right moment comes you trigger a pin or pins that pull and drop the screen?

The bottom bar of the screen could be weighted to drop fast. You could more than likely even create a locking feature at the bottom but it might not be necessary.

This way you eliminate a lot of moving parts that could fail.

Ruppro
04-19-2017, 02:15 PM
What about a gravity type system? Have the sail in the up position and a guy wire on each side of the screen vertically and then when the right moment comes you trigger a pin or pins that pull and drop the screen?

The bottom bar of the screen could be weighted to drop fast. You could more than likely even create a locking feature at the bottom but it might not be necessary.

This way you eliminate a lot of moving parts that could fail.

That would actually be a more authentic way the sails would be deployed on a pirate ship, the only issue to work out would be a way to raise it when not in use

plasmadrive
04-19-2017, 02:40 PM
The gravity idea is actually quite smart. You would just have to make sure you have it set up to fall right.. and the perhaps roll it up via a motor afterwards..

kev
04-19-2017, 05:07 PM
An inexpensive winch from Harbor Freight likely would provide enough power to lift/lower your sail apparatus. Just would need to auotmate the on/off/forward/reverse. They have a winch rated for 2500 lbs. with a wireless remote for $70. Use a 20% off coupon for more savings. Might be easy to adapt the wireless remote for automated operation.

dmpeaceman
04-20-2017, 10:21 AM
These are all really great ideas -- THANK YOU.

I thought of the gravity idea as well - the concern is just lack of control of course, but it would certainly look dramatic.

I'm leaning towards this:

https://www.amazon.com/Cloud-Mountain-120-Inch-Projection/dp/B01FXGOME0/ref=sr_1_11?ie=UTF8&qid=1492697857&sr=8-11&keywords=pull%2Bdown%2Bprojector%2Bscreen&th=1

I'm SURE it's not rated for outdoor use, but I'm willing to test it, leave it outside in the elements for a couple months open and closed, getting wet etc, and see how it holds up. I'm guessing the springs inside are eventually going to rust and seize....but hey, you never know until you try. Go big or go home, right?

The idea would then be to mix a bit of all your ideas - DC motor with gear box to pull DOWN the screen instead of up, with decelerating switch, and an end-switch to detect where it physically is.

So I'm gonna go ahead and buy it - and report back. CHEERS EVERYONE!

jchuchla
04-20-2017, 03:06 PM
I was thinking the same thing as protégé above. In the event staging business that's called a kabuki drop. It's a one time use prop (per show) with a manual reset cycle. Often the whole thing comes down to the floor to be rolled, then hoisted up on a simple pulley sort of rig. (or attached to a truss and raised with chain motors). It could also be folded back and forth like the old pinfeed paper for a faster drop with no rotational force to deal with. The release mechanism consists of a handful of cords that wraps under the stored fabric attached to a solenoid, sometimes (less common) an electromagnet catch. when you push the button, it releases the solenoid and it drops. There's usually a second solenoid release mechanism that releases the fabric from the top batten to let it come down just as fast as it was deployed.
When you google kabuki drops you'll mostly find descriptions for mechanisms for the dropping the curtain to the floor, the second stage of the apparatus I described above. But the same systems are used for the first stage as well, just with the retention cord/straps instead of the top batten.

For material selection, you'll want to look into "blow thru" materials. This is a product we use a lot for this type of job. http://www.ultraflexx.com/product/speaker-mesh/ instead of a solid piece with u holes as you're describing, this is a mesh, more like a window screen. It's much more uniform than something with holes in it. This particular fabric will let 70% of the wind pass right thru it while still doing a good job as a visual for a screen. It's PVC coated polyester and thus will not soak up moisture. That doesn't mean it's not heavy. It just means it doesn't get much heavier when wet than when dry.

In this application, I'd stay away from motors to deploy the screen. Anything strong enough is going to be way too slow to be useful in a production. You can certainly use chain motors to lift the rig before the show. (or even HF winches if you want to be cheap, but they don't make any strong enough to be safe anyhow) But they won't be anything near fast enough for the effect you want. Any motor that's fast enough won't take much abuse from the wind or weight, or it will cost a fortune.

Keith R
04-20-2017, 05:24 PM
I think plasmadrive had some great comments. I bought a couple of these (http://www.monsterguts.com/store/product.php?productid=17685&cat=3&page=1) a few years back and they have given great service and have a lot of torque. I also tried using micro switches, but the rain would somehow enable the switch and keep the motors from running. I also think the guy wires are going to be very important. You will have to stabilize it in every direction. You don't want the mast falling onto your roof. Torque may be an additional factor if the wind is not blowing directly into the sail. It could put a load at the base of the mast and "twist" it. Just my thoughts.

Kensington
04-20-2017, 09:16 PM
I would look into theater scrims or gray tulle for this application, and let your projector do the graphical work of making it look like a sail. You'll have an easier time raising and lowering a scrim, and it's somewhat wind transparent. I have a 16x9 foot screen for the back yard, and it's hard enough to control with 4 earth anchors and a rigid frame. If you mount a solid screen on a mast, you're going to have an interesting time.

For raising and lowering, I'd go with something simple. I'll give it some thought, but I like the other ideas here.