My acoustically transparent screen with electric masking - AVS Forum
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post #1 of 13 Old 07-03-2008, 09:56 AM - Thread Starter
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It took me 6 months to complete this project.

Making the screen only took 1 week.






Then I spent the rest of the time to figure out how to make the moving masking. A picture of the driver.


Now I can flip a switch on the wall and set whatever aspect ratio I like! (My projector is 4:3)


Masking in action. (sorry the system does not allow me to post a link to the video)
Please search JBbRFMy-IJ4 on youtube.

Part list and source:
Acoustically transparent cloth: Dazian
Frame materials and parts: Home Depot/Lowes
Background and masking fabric: Joann
Gearbox and motor: Tamiya worm gear box from local hobby store
Timing belt and pulley: McMaster-Carr
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post #2 of 13 Old 07-04-2008, 08:08 AM
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Here's the video:
Electric Masking

I'd like to hear more details about how you built the electric masking.
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post #3 of 13 Old 07-04-2008, 03:06 PM
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Any more pics of the masking system?

The Zen Garden HT - Move Along...There is Nothing To See Here.
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post #4 of 13 Old 07-04-2008, 10:14 PM
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Hi "threeinone",

Would love to see more detailed pics & info on your masking system, like model numbers for pulleys, belt & motor & gearbox. Thanks & great job on your build, hope you & your family & having a blast !

John
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post #5 of 13 Old 07-06-2008, 03:01 PM
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Quote:
Originally Posted by HDGTX View Post

Hi "threeinone",

Would love to see more detailed pics & info on your masking sysytem, like model numbers for pulleys, belt & motor & gearbox. Thanks & great job on your build, hope you & your family & having a blast !

John

+1

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post #6 of 13 Old 07-07-2008, 09:59 AM - Thread Starter
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Thanks Gerry for the link to the video and all for your interests. I wanted to reply earlier but was trying to draw a better illustration of the masking system. But finally I gave up and just drew this in Powerpoint.



Overall, the principle is simple. I use strings to synchronize the rotation of the rollers in opposite direction. When the top masking drops down by gravity as the top roller rotates, the lower masking is pulled up by the string. At a point on the string it is fixed to the roller so it will pull the roller to rotate and will not skid.

One motor/gear box is driving the lower scroller.
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post #7 of 13 Old 07-07-2008, 10:16 AM - Thread Starter
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As for the parts, the motor and gearbox are from tamiya, just search "Tamiya Worm Gear" in google it is in the first link. I got it from a local hobby store called Hobby Land. The timing belt and pulley are from McMaster-Carr.com. McMaster-Carr has a section of catalog for different timing belts and pulleys so I think it is easy to find one to fit. My order

2 Each 1679K119 Trapezoidal Tooth Urethane Timing Belt .200" Pitch, Trade Sz 100XL, 10" Outer Circle, 3/8" W $3.93 $7.86
2 Each 57105K22 Acetal Pulley for XL-Series Timing-Belt for 1/4" & 3/8" Belt Width, 1.75" OD, 24 Teeth $7.36 $14.72
Merchandise $22.58
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post #8 of 13 Old 07-08-2008, 06:25 AM
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What are you using for rollers?
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post #9 of 13 Old 07-08-2008, 08:10 AM - Thread Starter
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Finally the toughest question comes. Just laugh at me.

The rollers are PVC water pipes and the axles are iron electrical pipes. Both are from Home depot or Lowes, cost a few dollars a 10-ft piece I think. The rollers are actually sitting very loosely on the axles.

Yes the system is loud when it runs and possibly it will fall apart one day. But I am not running it very often so I can live with it.
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post #10 of 13 Old 07-08-2008, 05:18 PM
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Ok thanks....I think you really have a great design going here. I am going to do something similar and will post (perhaps to this thread) once I get started. I am also going with a 16:9 setup and then want masking for 2.35, 2.40, etc as oppossed to the loss of screen real estate by starting with a 2.35 screen and then masking the sides to 16:9.

Nice job on this.
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post #11 of 13 Old 07-12-2008, 12:16 AM
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Thanks for the info & drawing "threeinone"

When you say it is noisy, do you mean the little Tamiya worm gear motor is loud or the roler ?

How does that little motor do handling the big rollers ?

I did find the that motor (it's model # 72004).

Thanks, John
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post #12 of 13 Old 07-14-2008, 11:49 AM - Thread Starter
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Both the worm gear and the roller makes noises but the roller is louder. The motor handles the roller very well. I am using an AC->5VDC power supply of an old PDA to drive the motor. Now I feel the masking is still moving too fast. I should have used a smaller pulley on drive shaft of the gearbox to further reduce the speed.
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post #13 of 13 Old 07-14-2008, 10:03 PM
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Quote:
Originally Posted by threeinone View Post

Both the worm gear and the roller makes noises but the roller is louder. The motor handles the roller very well. I am using an AC->5VDC power supply of an old PDA to drive the motor. Now I feel the masking is still moving too fast. I should have used a smaller pulley on drive shaft of the gearbox to further reduce the speed.

Maybe you could find a 4 V DC power supply for the motor, that should also slow it down.
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