My acoustically transparent screen with electric masking

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

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.

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

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.

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.