Quantcast

DIY tensioned fixed screen

helipilot

Active Member
I have been working on this project for several months.

We have just moved house and I finally have a dedicated room to build my ultimate home cinema in.

In our previous cinema I used a Harkness Hall 1.3 gain electric screen. The screen performed well but was never completely flat. I decided for the new cinema the only way to go was a fixed screen. I looked at various commercial options but none could provide a fixed screen with masking that I could afford.

I drew up various designs until I came up with this. The base frame is 32mm square steel tubing which was welded together. The hoops were made by hand and individually welded into the frame. My Harkness Hall screen was cut for the screen material (very scary for a screen that originally retailed at £1700 !) Brass eyelets were fitted and the screen tensioned using bungie cord. The picture frame is MDF which is covered with velvet. The horizontal frames had to be spliced as the width is over 100 inches. I could only get MDF up to 8 feet wide so there was no other way.

Fitting the eyelets was time consuming and tedious as I was not sure how well the tensioning system would work. I need not have worried as the final result is perfectly flat with a drum like surface with superb results in pans.

Here are a couple of pictures showing progress. The final phase for the screen will be to make and fit top and bottom masks.

I hope the pictures might give others the inspiration to try their own. The screen currently looks very similar to a commercial screen costing several thousand pounds.

smallscreen1.JPG


The bare screen showing the tensioning system and the rollers for the masking system


smallscreen2.JPG


The velvet covered MDF picture frame in place.
 
Last edited:
B

Bud16415

Guest
Helipilot

Very nice job.
I’m glad to see I’m not the only one in the world working on a tensioned fixed screen design. I also considered making one similar to yours but I wanted a borderless screen and went the internal tension method instead.

Yours holds the skin very tight. Very impressive!!!! :smashin:
Below is a link to some pictures of mine and the link here if anyone wants to take a look.

http://www.avforums.com/forums/showthread.php?t=296978

http://community.webshots.com/album/546725411dBQqjb
 

helipilot

Active Member
Thanks for the encouraging comments.

I have just completed the masking system and it has now been put in place.

The masks are currently adjusted by a small wheel at the bottom right of the screen. As the wheel is turned the top mask moves simultaneously in the opposite direction from the bottom one. At some point I may add an electric motor to be controlled from either a Pronto or HTPC.

The bottom mask spar took a lot of thought to get right. Initially the spars were mild steel but the bottom drooped noticeably. I tried several designs eventually fabricating the spars from several layers of model aircraft quality plywood. The top of the spar was then reinforced with carbon rods from a kite shop. An expensive solution but one that works exceptionally well with no bow in the spar and no droop forward.

masked1.JPG




masked2.JPG



My thoughts will now turn to the rest of the room.
 
Last edited:
B

Bud16415

Guest
Alan

Two thumbs up on the masking system.:thumbsup:

Very nice work. :clap:
 
D

danburbridge

Guest
do you have any shots of how the adjustable masking works - have been thinking about doing something like that with my diy screen for a while (just never got round to finding a good way of doing it)

Cheers
 

helipilot

Active Member
The masking system is totally hidden by the main picture frame. Even with the picture frame removed it would still be difficult to see. Here is an exploded rendering of the bottom left of the screen with the screen tensioning components missed out to aid clarity.

MASKING.JPG


The cord, shown in red goes up to the top roller via two idler pulleys. The cord crosses from front to back between the pulleys in a sort of figure of eight shape. This ensures that as the top mask comes down the bottom one goes up. There is a cord at either side of the screen. The cord is fitted first and tensioned. The velvet masks are mounted onto the horizontal spars, shown in yellow and then secured to the cord using small blocks and bolts (not shown in diagram).

That should give you a good idea how it works.
 
Last edited:
D

danburbridge

Guest
wow - cheers for the expoded diagram/render - shows it wonderfully :)
 

catesby

Standard Member
Great screen Alan. Just a couple of questions. How did you cut the MDF picture frame so accurately out of MDF? Also you say you covered it with velvet, how did you manage to deal with the tricky inside corners? Did you glue or staple it? Cheers
 

helipilot

Active Member
catesby,

The frame started off as an 2440 x 1220 x 20 MDF sheet. This was cut into 130mm wide strips using a circular saw. Because the frame is more than 2440 wide scarf joints had to be made to extend the length to approx 2600. Once the glue had set a bevel was made half the width of the frame. This was done by making a carrier to support the mdf at an angle and then feeding through a planer. The mitres were then cut at 45 degrees for the corners. A biscuit jointer was used to help locate the mitres. Corner supports were then made and the whole frame held tight using a spanish windlass while the glue set.

The velvet was attached initially with double sided carpet tape and then stapled to the back of the frame.
 
Top Bottom