My Vertical Masking Master Plan

Ok WARNING, this is totally over engineered, over designed and over thought!!! But it was kinda fun figuring it all out.

Any way this is my idea for vertical masking that will also close completely to cover the screen when not in use. Once set it should be 100% accurate all the time and never need any adjusting or maintenance which were top priorities when I was doing it. No springs to wear or break, no cables that can stretch causing alignment problems. It should be rock solid. I haven't worked on anything as far as automation yet, but it will all be driven by one 12 volt motor, probably just an open/close switch to start with.

So any way let me know your thoughts on this.

DOWN LOAD THIS FILE

It is a SketchUp file so you will need Google ScetchUp to read it (free program)

Here are some 2D images, much easier to look at in SketchUp though.

I would prefer a coged belt to the chain also because of the noise. But so far I haven't found a source for a belt that is that long. But I am still searching.

It is 60-1/2" center of shaft to center of shaft. Any info you have would be great. I am starting to put together a parts list to order

One side is right hand thread and the other is a left hand thread. So even though it is all turning the same direction they will move in opposite directions.

I just one place that I think will have what I need, they are called SDP/SI, looks like I should be able to get what I need.

I have to figure out the RPM's on my motor first though so I can figure pulley size.

Thanks for the offer. I do have laying around a 12v motor that is made for operating the landing gear on an equipment trailer. I have to test it out some more because I don't know if it is a 1600 or 2200 rpm model and it also has a 59:1 gear box on it. I think I can eliminate the gear box and use just the straight motor. I want about 1700-1800 rpms to the screws when done.

I also don't want to drive the threaded shaft directly, I want to drive the belt/chain. Reason is: if I ran just a belt from top shaft to bottom shaft and they drove the bottom shaft with the motor directly (would be easiest), then what happens if the belt/chain happens to break or jump off... You could get a big mangled mess as the motor would still drive the bottom shaft but not the top. Guess that would be a way to correct keystone though!!!

If you have the picth and number of grooves in the pulley you can figure the length. I am going to get my motor figured out this weekend before I put to much effort into finding correct pulley and belt. But I am going to do the belt since I have some good souces, thanks much.

Wonder if I will need to do an idle pulley to keep the belt from slaping with that long length....

Just an update that I have the main frame all built and am working on the treaded shafts now, been too lazy to take pictures yet. After this week end I should have it all done except for the belt and gears, need to get the motor mounted first so I can figure out belt length. So far looks like everything is working as planned.

OK I ran into a small snag. The DC motor that I had intended to use doesn't look like it is going to work out. It has a 59:1 gear box on it that I thought I could just pull off and use the motor itself. Which I can but the actuall motor has just a tiny, maybe 1/8", shaft on it. Shaft coming out of the gear box is 1/2" so I thought the motor shaft would be close to size. Well this is way to small of shaft to put the gear on to run the belt, and I can't leave the gear box on or it will be way to slow....

So any good sources out their for a 12V DC motor that turns around 1800 rpm and has a 1/2" shaft on it? As long as I have to get a different motor how about something with a built in control for stop points?

I am guessing somewhere around 300-400 inch pounds of torque is needed.

The extra sprocket is where the motor will be mounted. Don't have a motor yet so I didn't draw it or the mount in. Also I will do a belt instead of chain.

I really don't know how much power I need. A cordless drill will turn the shaft with every thing together. But I don't have the masking material on yet which will add some resistance also, how much depends on how much tenstion is needed to keep 6' of material from sagging.

I see a couple of possible problems.

1) screw drive openers only come in one thread direction. This means that to work you would have to use a motor on each end. One turning forward and one turning backwards, the screws can't be connected beacause they have to turn opposite directions. So some how you would have to get each motor to start and stop at exacty the same time and run exactly the same speed to stay in sync with each other. Or you would have to use seperate position sensors and controls on each one.

2) you are going to need screws top and bottom I think to keep the masking edge square to the top and bottom of the screen. You have to remember that you are going to have the tension of the masking pulling on that leading edge trying to bend it to the outside edge of the screen. I don't think you could ever brace it enough using only a top or bottom screw to keep it square.

3) shortest door opener is 7' so you are going to have to cut it of, unless you have a 14' wide screen. And like I said earlier you would need to buy 2 of them atleast.

I look at this option also and just came up with too many problems or possible problems down the road. Plus it is no cheaper when you really start figuring it out.

As far as motors go you can use 120v, I am going to use a 1/3hp 120v motor that I had laying around out of a furnace that is reversable and very quiet. I will be using a rotor control that will alow you to program in 99 memory positions for different screen sizes. The rotor out put 19volts which is will use to trigger a relay that is triggered by DC and switches AC to the motor. A timing belt will transfer power to the upper screw, so the entire thiing is controlled by one motor. The ony way it can possible get out of sync is if one of the dowel pins that I have connecting the screw shafts was to shear off, and I don't see that happening.

ScottJ0007 has a very good thread that explains how to use the rotor: http://www.avsforum.com/avs-vb/showthread.php?t=941076

Never mind I should have looked at the name first, you know all about the other thread......good work

Good idea.

I am working on hurdles right now. Running into far to much vibration in the treaded shaft that are spanning 6' with now support. I had thought that the 3/4" shaft would have been a little stiffer then that. I have some new pulleys on the way to slow down the RPM's and I am also going to add a rail system that they moving part of the mask rides in so it can't move up-down or front-back as the shaft is trying to vibrate, should take care of alot of it.

Oh and a furnace blower motor has no starting power at all so I am up to a regular duty 3/4 HP motor. Its a little over kill but it works.

I like the belt idea: Queit, doesn't need a fast RPM speed, that could be made to work. If I wasn't so far into this now I would do a design around that. But now it is just a personal mission to get this thing to work. I can make it work, bigges draw back when all is done could be that it is not a silent system at all.

Yea they are reversible that is no problem. I tried both a 1/4 and 1/3hp version and they just don't have the power, you can hold them with your hand, no starting capasitor on them. Luckily I oversized my relays so I could step up to a 3/4 10amp motor no problem.

Screen is going to be Seymor Center Stage XD. Masking will be black 701 GOM

I have the system all built now but am having some problems with the control system that I can't figure out. That is being discussed in this thread http://www.avsforum.com/avs-vb/showt...941076&page=25 starting at post #722

UPDATE:

I have a 99% complete theater now with a working masking system based on the rotor control that was figured out in this thread. For some reason I do have to do a little voodoo magic to get it to reset correctly but it does work. My masking is only 2 way but it goes from completely closed to open on a 142" wide screen.

Here are pictures at closed, 4:3, 16:9, 2.35. It will go open about another 3" from the 2.35 position.

More pictures can be seen at the link in my signature.