DIY Curved AT screen with Somfy based automated masking - AVS Forum
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post #1 of 111 Old 12-03-2010, 03:56 PM - Thread Starter
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Teaser:


========= Original Post ==============

I posted this in my build thread, but then thought that it might be better to document here....

It is with great trepidation and mixed feelings that I'm launching into my screen building. The reason for the emotions is that I am so desperate to watch some movies in my HT since I've hardly seen any since I started my build and the movie-catch up is going to take weeks.

Anyway, I haven't come this far to give up on my screen plan, so here is the first installment.

The plan:
130 wide curved AT screen with integrated (within the frame border) horizontal masking with full independent left/right masking control. The goals I've set are that I want to create a professional job that is less than 4 thick so that it disappears into the screen wall frame, the mechanism needs to be simple to reduce build and setup time and the budget should be around $1600. Possible.??? We shall see.

After numerous design scribbles I realized that building a curved screen complicated what really should be a fairly simple process for a flat screen. Some of the problems include attachment to the screen fabric along the arc whilst allowing a very close fitting mask, bending of any linear slide mechanism for the mask, keeping a simple drive mechanism that can stay within the 4 thickness goal.

The basic construction approach is shown here:



The goal is to leverage the precise repeatability of the new Somfy ILT motors and to use a constant spring to provide closing tension. I.e. no pulleys, no wires, just the KISS approach. Of course the devil is in the details and I'm under no illusions that a cheap, curved and smooth linear motion track that doesn't get stuck is the key. The plan is to have the mask ride right next to the screen fabric (to prevent shadows) and to have a minimal gap at top and bottom for the leading edge of the mask.

Step 1. I wanted to be sure that the size was going to work, particularly the location of the leading edge of the mask at the prime aspect ratios. The leading edge of the mask will be solid and I didn't want this to fall in the direct path of the tweeters.



Step 2 was to get the horizontal frame members bent to my calculated 42' radius. My preference was to use an extruded aluminum frame with various t-slot cutouts for convenient attachment but I completely failed to find somebody to bend these or to purchase them pre-bent. The problem with bending aluminum is that it is difficult to keep the extrusion profile intact without the correct bending die or by bending as the extrusion is made.

My fallback was to opt for a steel frame. Aluminum would have been nice and lighter but one advantage of steel is that it is much easier to bend and weld. So off to my local steel yard to purchase the steel and to get them to run a couple of pieces through their Eagle rolling machine. Cha-ching: $320 including bending.

Once home I cut the pieces to size and welded up the frame, taking care to ensure it stayed square. The primitive rolling machine the metal yard used did get the radius curve correct but gave me a slight warp which I needed to work out during the welding process. You can see a laser level in the second photo keeping me honest.



Once welded it was outside to do a bit of cleanup of the welds on the inside edge (the side that I plan on using a cunning plan to mount the screen fabric). In fact the screen attachment plan is so secretive that I don't know it myself yet



Then a coat of primer. You can see the cleaned up weld to create a perfectly smooth surface.



It was precisely at this point that I panicked and questioned what the heck I was doing and call up Jason Turk at AVS to see if I could get a 130 non-masking SMX screen cheap. No luck. A few beers later I calmed down and got my wife to lift this monster back into the garage. Then I panicked again what if this wouldn't fit through the theater doorway? Luckily, I think it will simply due to my fortunate door arrangement (alignment).



I then spent the rest of the day on-line ordering parts:
2x Somfy Sonesse LT50 ILT motors: $740 (yikes!)
RS485 interface: $60
2 tubes and roller blind mounting h/w: $100
Grommets + tools, rubber rings: $32
USB to RS485 interface: $40
6061 aluminum bar, t-tracks, etc: $70
SeymorAV CenterStage XD fabric: $280
Total: $1,322

Plus steel, total to date: $1,622. Well, that's blown the budget already so I might as well give up... Seriously, other than some miscellaneous fabric, misc hardware, some scraps of steel plate and some MDF (most of which I have lying around) I think I have all the raw materials I need.

I should probably explain my choice of the expensive Somfy motors a little. There is no way to get around the fact that these are expensive, but I know from experience how much time a motor control system takes to build when I converted my home mill/lathe tp CNC. The neatness of the Somfy system, the quietness of their Sonesse motor (44 dbA), the ability to program 16 intermediate stopping positions, encoder based positioning and the fact that the RS485 control bus can easily interface to IR/RF/Z-wave, etc makes this an obvious cost/time tradeoff to me. If anybody is curious I'd suggest you read up on the ILT line of motors and their SDN control bus. I briefly looked at the SMX masking system functionality and this motor and controllers can do everything that can do

To be continued

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post #2 of 111 Old 12-03-2010, 10:15 PM
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Enjoying your screen & masking system build, thank you for sharing the process!


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post #3 of 111 Old 12-03-2010, 11:30 PM
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Nice Moggie,

I am just about to embark on a 170" curved screen DIY build my self. So I am very interested as to how you get on.

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post #4 of 111 Old 12-04-2010, 05:59 AM
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Very well thought out project, I'm sure you'll post picts of your journey as you climb to the top.
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post #5 of 111 Old 12-04-2010, 10:03 AM - Thread Starter
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mtbdudex, HDGTX

I'll be sure to document the whole journey. I have most of the details worked out but right now I'm waiting on parts. I should be able to resume progress in a few days.

I've been experimenting with a simple approach to a constant spring. I believe that I can accomplish this with a piece of thin bungy cord running inside the linear slide. The convex curve on the back side of the frame will aid in keeping it in place. If this works out the benefit will be a very simple approach that keeps within my goal of creating a low profile mechanism. I've read most of the other builds here (including yours mtbdudex) and found talk of a constant spring approach but didn't find anybody that has actually implemented it. Do you guys know of any?

Quote:
Originally Posted by JapanDave View Post

Nice Moggie,
I am just about to embark on a 170" curved screen DIY build my self. So I am very interested as to how you get on.

170" wide? That's a monster! Are you planning masking?

It seems to me that a flat screen with automated masking or a curved screen without masking are of reasonable complexity. The combination of both a curve and masking keeps making me scratch my head...

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post #6 of 111 Old 12-04-2010, 04:05 PM
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Hi Moogie, You might look into UHMW plastics if you need some very slippery surfaces to cut down on friction. I have can prvide some sources if needed. That's a mt'l I plan to use whenever I get around to building my screen & masking system.

AV-Outlet has some tensioners, not sure if they would work with your designm but take a look, they are called "PESA Pin-end spring assists, meant for roller shade tubes. Click on "Roller Shade Componets" in the left column & ;ook for the "Roller Shade Spring Assit Componenrs" fpr 1.25" & 1.5" AL tubes. They also sell AL Rolleze roller shade tubes in 1.25", 1.5", 2" & 2.5" size;

http://www.av-outlet.com/



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post #7 of 111 Old 12-04-2010, 05:48 PM - Thread Starter
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Quote:
Originally Posted by HDGTX View Post

Hi Moogie, You might look into UHMW plastics if you need some very slippery surfaces to cut down on friction. I have can prvide some sources if needed. That's a mt'l I plan to use whenever I get around to building my screen & masking system.

AV-Outlet has some tensioners, not sure if they would work with your designm but take a look, they are called "PESA Pin-end spring assists, meant for roller shade tubes. Click on "Roller Shade Componets" in the left column & ;ook for the "Roller Shade Spring Assit Componenrs" fpr 1.25" & 1.5" AL tubes. They also sell AL Rolleze roller shade tubes in 1.25", 1.5", 2" & 2.5" size;

http://www.av-outlet.com/

John

Thanks John, I did order some parts from av-outlet. I was planning on using Derin for the slides because I have some and it machines much better than UHMW. If it is not slippery enough then I'll look at UHMW. I'm lucky enough to own a small mill so I can experiment.

I first thought of using a roller shade assist in the normal manner to provide opening tension and using a motor to pull the mask open but changed my mind when I saw the versatility and neatness of the Somfy ILT motors. Or are you thinking about using the shade assist to provide closing tension at the opposite side to the motor? It seems to me that this would result in a more complex mechanism than a simple piece of bungy attached to the slide and running the length of the screen. If this is not long enough to approximate to a constant spring then it could be extend around a pulley to add length. I still have flexibility on bungy vs wire and spring at this point.

Edit: Actually I realized that I will be using UHMW tape on the inside of the top/bottom frame to create a surface for the mask fabric to rub against...

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post #8 of 111 Old 12-04-2010, 06:10 PM
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This should be fun to follow. Your theater build was excellent !! Congartulations.

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post #9 of 111 Old 12-04-2010, 08:14 PM
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Here's a link to another AVS member (CIR-Engineering) who built his horiz masking system around a Somy tube motor...

http://www.avsforum.com/avs-vb/showt...ighlight=somfy
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post #10 of 111 Old 12-04-2010, 08:44 PM - Thread Starter
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Quote:
Originally Posted by HDGTX View Post

Here's a link to another AVS member (CIR-Engineering) who built his horiz masking system around a Somy tube motor...

http://www.avsforum.com/avs-vb/showt...ighlight=somfy

Maybe I've always had it backwards but wouldn't you call CIR-Engineering's design a vertical mask?

It sounds like he was able to put it together very quickly and cost effectively and clearly it works well! Other than the flat vs curved and vertical vs horizontal differences the main changes I'm trying to incorporate are:
1. Independent masks/motors for fine tuning
2. Programmed multi aspect ratios with ability to integrate into my automation system. The ILT motor line allows this with 16 (not just 2 or 3) positional stops and its RS-485 based control.
3. I'm using motors from the Sonesse line which are much quieter than the standard motors although about $120 more expensive.
4. I'm trying to get the mask to be flush with the screen rather than something that rides over the frame.

One thing that I might have over engineered already is the use of the LT-50 504 (35 in.lbs) motor rather than the LT-30 (18 in.lbs). I probably don't need the additional torque but the price difference wasn't huge and the ST-30 is a DC motor so would require an additional power supply.

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post #11 of 111 Old 12-07-2010, 07:56 PM
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Good Luck with your automated masking. I think you are making a very smart move in using the Somfy motors and controllers. Yes, they are expensive, but when you consider the cost of a commercial masking system, it is not too bad. I guess you could of used one motor to save some money. Is there a real need to move the masks independently? If you are going to use IR to control the masks, do you need an IR component to interface with RS485 controller?
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post #12 of 111 Old 12-08-2010, 09:14 AM - Thread Starter
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Quote:
Originally Posted by Mike_2008 View Post

Good Luck with your automated masking. I think you are making a very smart move in using the Somfy motors and controllers. Yes, they are expensive, but when you consider the cost of a commercial masking system, it is not too bad. I guess you could of used one motor to save some money. Is there a real need to move the masks independently? If you are going to use IR to control the masks, do you need an IR component to interface with RS485 controller?

Hi Mike, yes I could have used a single motor. In fact that was my original plan. With that approach you would need a pulley system and some form of manual adjustment to align the left/right mask. Also don't some anamorphic lens (prism based) introduce a slight horizontal shift? I could easily see the $350 saving being eaten up with expense on more mechanical complexity. I like the simplicity and flexibility of the dual motors and when you compare the cost to a commercial curved masking system, this project is not expensive at all.

Somfy offer an IR/RS485 interface at the motor for around $30. I'm not sure if I'm going that route or IR->RS232->RS485 at my rack. Probably the former, at least initially.

I should have an update soon - I'm still waiting on a few parts but did cut and fit the SeymourAV Center Stage XD fabric. BTW, while I was cutting the fabric I had a question about orientation and so sent Chris a message via his web site on a Saturday. Two minutes later I got the reply! That's what I call customer support.

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post #13 of 111 Old 12-08-2010, 07:43 PM
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I look forward to your progress and updates. I was correct that you are going to need another component for control. If you go RS232, are you thinking of using home automation software? Is so, which software? I have looked at Home Premise on the ConcoonTech.com which is free, but not widely supported.
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post #14 of 111 Old 12-14-2010, 04:13 PM - Thread Starter
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I'm still waiting on the roller tubes and motors but have made a dent in the rest of the screen/masking build so I thought I'd share.

First job was to complete the screen material mounting plan. Since I'm attaching the fabric to concave face I needed a way to ensure a consistent curve in the surface. To do this I drilled and tapped a 2" x 1/8" piece of aluminum strip to the face making sure the holes accounted for the fabric thickness. These scrips will also serve a couple of other functions: (i) stiffen the steel frame, (ii) add the desired standoff for the frame, (iii) provide a mounting lip for the wood frame.

I made some mounting brackets out of angle iron and welded to the frame. I also added "wings" at either end to carry the rollers and motors. In retrospect I should have just continued the horizontal tubes. After the welding was complete to reduce the possibility of resonance I filled the frame with expanding foam. I drilled a few holes on the backside and squirted the foam. It quickly spread out of every little hole which at least proved it was working although it was extremely messy.



After cleaning up the foam and a coat of paint I performed a trial fitment of the SeymourAV Center Stage XD fabric. You can see the approach in this picture. Basically the fabric was cut on the greatest angle I could get about 1 3/4" larger than the frame outline. I borrowed Seymour's approach and fitted grommets on 6" centers then used silicon o-rings to pulled the fabric tight around the frame. The o-rings attached to a line of self tapping screws on the backside (I cut up some plastic pipe to eliminate the sharp thread of the screws and to ensure consistent height.



You can see that even with about 60% of the o-rings fitted and without the aluminum strips the fabric followed the curve rather well. The placement of the threaded holes (for aluminum strip) were marked and then an additional over-sized hole was punched so next time the aluminum strips can be fitted after the fabric is fully stretched.



With the frame finished it was time for the screen border (which is going to house the masking system). I used the curved steel as a template to glue two pieces of (pre-routed) MDF together for a total thickness of 1 3/8". The inside profile channels from left to right are (i) channel for bungy cord providing a constant spring, (ii) channel for the linear motion track, (iii) recess for fasting the velvet covering. The flat between (ii) and (iii) will have a 1/32" thick piece of UHMW tape to provide the surface on which the mask will glide.



I'm making the linear motion track out of t-track and some custom made glides. The glides were machined out of Delrin, a pretty slippery and easy to machine plastic. I experimented a bit with the shape and length and found 2 1/2" long provided enough glide surface without the possibility of binding when the track is curved. Each glide will be tapped so the leading edge of the mask can be attached.



Here's a video showing how well the slide works.

Finally, perhaps this last picture will convey what I'm trying to do with the border? If not it should become clear in the next update (or else I go into hiding because the attempt was a complete failure ) The idea is that the bungy cord is attached to the slide and by virtue of being under tension and pulled around in a curve will sit inside the t-track. In the center pocket the bungy will exit the track and be routed to the parallel channel. The same will occur on the other side so the bungy cords will cross in this section. The bungy channels will be sealed by being tight against the aluminum strips fitted to the steel frame.


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post #15 of 111 Old 12-14-2010, 08:10 PM
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The screen with the material looks perfect- Your work is unbelievable!!!
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post #16 of 111 Old 12-15-2010, 01:40 PM
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Nice work!
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post #17 of 111 Old 12-16-2010, 08:31 PM - Thread Starter
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This is probably going to be my last update of 2010 (boy has it gone quickly) since I'll be enjoying a little Christmas vacation. I had really hoped to have my screen hung by now in preparation for a new projector in Jan but it looks likes my time line has slipped again.

More parts arrived today including the Somfy motors. They didn't send the darn software to program them as promised so I'm going to have to track that down. Also I found out that you need a special device ($) to perform the one time setting of the limits. I'm going to chat with customer support on this but it seems daft to have such an advanced and windows-programmable motor that requires a dedicated device to perform a one time setup task? Anyway the motors look very high quality.



I did manage to complete the screen border shaping/framing as well as creating a mechanism to allow the removable sides to accurately press into place. I thought a single dry biscuit joint would suffice but in order to keep the accuracy needed for such a minimal screen/mask distance I added two additional dry dowel guides. I was thinking of adding a magnet coupling but the sides seem to fit snugly enough that this may not be necessary. You can see the planned location of the Somfy motor. I still need to route a recess on the frame sides to give room for the rolled fabric -- I think this screen/mask will end up being only 3.5" thick! You can also see the end of the 1/8" aluminum strip that acts as a spacer under the border.



Here is a view of the 1/8" gap (that exists all around the frame) where I hope to run the mask and sled.



There is no margin for error with tolerances this tight. Fingers crossed.

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post #18 of 111 Old 12-16-2010, 09:45 PM
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Moggie: I am not sure if you have the new ILT2 motors, but the below link references part 9050280, that looks like it is used to set the initial motor direction and end points. I did see the software you referenced for programing the motors. Maybe the process changed for the new ILT2 motors. I agree with you that everything should be software driven to do the required setup.

The link contains the word beta, so I do not know if this is actually "live" information.

http://www.somfy.com.tw/downloads/tw...e_may_beta.pdf
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post #19 of 111 Old 12-16-2010, 09:58 PM - Thread Starter
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Mike, thanks for the link. Yes, mine are ITL2 motors. This is definitely an updated catalog and I see the part I need. I wondering, given that everything else about these motors is s/w programmable, if the limit setting is done in the same way as the original non-ITL motors. I.e. just a simple set of contact switches? If so I'm not going to pay for this part -- I can wire up a temporary switch. I call Somfy tech support tomorrow and find out.

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post #20 of 111 Old 12-17-2010, 08:50 AM
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Without question, Awesome!!
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post #21 of 111 Old 12-31-2010, 01:17 PM
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updates, updates!

you are a perfectionist, your craftmanship is impeccable. glad to see someone designing a nice vertical masking system.

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post #22 of 111 Old 12-31-2010, 08:41 PM
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updates, updates!

Seconded. This is amazing.
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post #23 of 111 Old 01-08-2011, 09:52 PM - Thread Starter
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Quote:
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updates, updates!

you are a perfectionist, your craftmanship is impeccable. glad to see someone designing a nice vertical masking system.

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Seconded. This is amazing.

Thanks guys. I'll have an update soon, but a Christmas vacation got in the way...

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post #24 of 111 Old 01-08-2011, 10:04 PM
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It'll come when it comes. As long as it does come, eventually!

I'm impressed by your fabrication skills. I can't weld worth anything. Still, this is something I think I'd like to try and duplicate when I get to my theater.
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post #25 of 111 Old 01-08-2011, 10:10 PM - Thread Starter
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Quote:
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It'll come when it comes. As long as it does come, eventually!

I'm impressed by your fabrication skills. I can't weld worth anything. Still, this is something I think I'd like to try and duplicate when I get to my theater.

You could probably get the frame welded up by your local metal shop. Failing that you could probably bolt it together with some heavy duty angles in the corners. Of course if you don't want a curved screen then bolted extruded aluminum is the way to go.

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post #26 of 111 Old 01-08-2011, 11:32 PM
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Wouldn't bolts hold on a curved screen anyway?

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post #27 of 111 Old 01-11-2011, 06:42 PM - Thread Starter
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Quote:
Originally Posted by CAVX View Post

Wouldn't bolts hold on a curved screen anyway?

You mean with extruded aluminum? Yes, but getting the extrusion bent is the problem.

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post #28 of 111 Old 01-23-2011, 05:01 PM - Thread Starter
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Boy am I slowing down towards the end of this build ... what with getting used to a new job and Christmas vacation I've only managed to push my screen build along a bit, but I thought I'd share the progress. At least I'm at the point where I just got out my wife's sewing machine to make the masking panels (time to learn another skill).

I fitted the aluminum t-track with epoxy glue and small wood screws. I didn't have any problem bending the track to the radius as it was secured in place. The track was routed flush with the wood but since the slider inserts stand proud 1/32" I glued some 1" UHMF tape next to the track. The idea was that this would create a low friction surface on which the masking panels would slide. You can also see that the frame has been covered with black velvet.



One problem I needed to solve was to figure out how the bungy cord springs where going to cross over with minimal friction. The solution was a combination of some guides and a tunnel for one of the runs. The guides are simply some small diameter aluminum pipe with a couple of washers:




The vertical frame members needed to be stiff (because they are only attached at the corners) and needed a surface on which the masking fabric would rub on. Because the masking mechanism is actually built into the frame they also needed to be hollowed out to provide space for the fabric as it rolls on the aluminum tube. The second picture shows a 1/2" rod embedded to provide the correct height for the fabric payout. I actually ended up using some aluminum tube for this function so it could be glued with epoxy. It was as this point that I tweaked the frame to be perfectly straight -- the aluminum rod acting as a stringer.



Now for the final assembly. First the screen material was stretched over the frame with small rubber o-rings. Then the aluminum strips where fastened through the holes punched in the face of the screen fabric. This pulled the screen perfectly curved and created the gap necessary for the masking mechanism. It turned out that my 1/8" gap was just a little overly optimistic. Everything did fit but it was a little tight for comfort so I used up the rest of my UHMF tape and increased the gap to 3/16" -- still not enough to create a shadow.



I also realized I needed to stop to prevent the slides from running off the middle of the channel during assembly.



This is the point where it starts to get hard to take photos because the Fidelio velvet is so black. The next two photos show one end of the screen with the masking roller fitted and the leading edge of the mask attached to the slides (but without the bungy cord tensioned). The frame sides press fit with a combination to two dowels and one dry biscuit joint to ensure accurate location.



The next couple of shots show the all important masking mechanism. Hopefully this is reasonably clear because it's kind of hard to describe.



This final photo clearly shows how the frame rides 3/16" off the fabric. BTW the leading edge of the masks is made from the aluminum extrusion used to hold door brush seals (McMasterCarr part # 8813T13) with the last 2" machined/filed flat to fit under the frame.



Hopefully next weekend I can fit the masking fabric...

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post #29 of 111 Old 01-23-2011, 05:15 PM - Thread Starter
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I'm clearing out my camera and thought these two shots might make the frame corner clearer. You can see the aluminum tube on which the fabric will ride and how the end of the t-track can be accessed.


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post #30 of 111 Old 01-27-2011, 01:10 AM
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Moggie your documenting the fabrication of the curved screen with auto masking is amazing. I have been following your HT and the screen build. The only part that I don't see in the photographs or in the detailed explanations that you have been writing is "how the Bungee cord is attached to the Somfy motors to provide the necessary movement of the masking" I will appreciate if you can write about this with few photographs to show it as well.
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