Help me with drawer slides or scissor arms for projector drop down - AVS Forum
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post #1 of 22 Old 08-22-2013, 12:05 PM - Thread Starter
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I'm in the design process of building a drop/lift for my BenQ W1070 projector. According to their website I"m going to mount it about 9' from the screen and 13" from the ceiling to get a 100” picture. My original plan was to use 4 drawer slides such as the ones below but I'm concerned about binding and I would really like everything to fit within my floor joists if possible (2x8, which I guess is more like 7.25"). These slide rails are 7.9” closed which are the smallest I can find anywhere! I know this will be difficult as the projector is little over 4" tall.

My next option was to try and build/buy scissor jack/legs whatever they are called. I can’t seem to find them anywhere to buy…might be because I don’t even know what the proper name is. In my random searching I came across these lab jacks. I wonder if I remove the threaded screw if they would open/collapse easily and I could just mount this to the ceiling and projector…assuming I can find one that will expand to 15”+ inches.

A linear actuator would then raise/lower the projector into place.

Any input would be greatly appreciated!!

Drawer slides, 7.9" when closed and expand to 15" when open.
http://www.ebay.com/itm/271183603078?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Lab jack
http://www.ebay.com/itm/400556394901?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649


PJ_zps5bad7e65.jpg
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post #2 of 22 Old 08-22-2013, 05:58 PM
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I don't really have a sensible answer, but here's a few related, random thoughts:

I used a high-spec pair of Accuride slides for part of my screen masking system and while they don't actually bind, they sometimes don't slide 100% in unison - probably not an issue for you as the weight of a projector would ensure everything dropped into the right place. Also, all the slides I've seen could be trimmed and/or adapted somewhat, so you could probably accommodate the slightly too long model you mentioned.

The lab jack you linked to looks promising - if the thread quality was semi-decent I'd be tempted to try to drive this using an electric motor, rather than retro-fitting linear actuators.

Another type of construct to consider would be to utilize a rectangular panel that is hinged on the edge furthest away from the screen and have the projector mounted directly to this at an angle that allows it to be parallel to the floor when the panel is 'dropped' - this gives good stability (by using a solid rear hinge) and allows for multiple options to power the raising/lowering (linear actuators, motor driven pulleys, worm drive, etc.).

It would be prudent, in any design you settle on, to include some form of emergency access or release - you don't want to have to dismantle the ceiling because a cable came loose and jammed the mechanism in the closed position!

There are commercial units that would do what you're looking for, but they all have pretty unattractive price points. One of the cheapest I've seen is this: http://www.mountdirect.com/EPL_Electric_Projector_Lift_p/epl.htm at about a grand. [Edit: Just re-checked the dimensions, and even this one would be too big! Duh] I use an Auton lift that could be adapted for a drop-down install, but it's way too bulky and definitely not a bargain!

Anyway, looks like a cool project!

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post #3 of 22 Old 08-23-2013, 08:06 AM
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What about a simple cable-pulley setup?


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Is it solipsistic in here, or is it just me?
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post #4 of 22 Old 08-23-2013, 11:51 AM
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Quote:
Originally Posted by BllDo View Post

What about a simple cable-pulley setup?


I'm concerned it might be a big let down.....biggrin.gif
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post #5 of 22 Old 08-23-2013, 03:48 PM
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6" drawer slides are not common but they are available: http://www.drawerslides.com/6inch-fulterer-fr-5000-series-100lb-drawer-slide-zinc

Having said that, I'm not sure how any drawer slide that fits into your 7"-ish joist space is going to move your projector 13" below the ceiling. A 6" slide only gives you 6" of travel. An 8" slide only gives you 8" of travel.

A hydraulic lift cart uses a scissor mechanism: http://www.harborfreight.com/automotive-motorcycle/lifts-stands/500-lb-capacity-hydraulic-lift-table-94822.html
The examples I have seen could not fairly be called "precision instruments," though. You might be able to adapt the mechanism to work in your situation and give you consistent positioning, but I imagine it would take a bunch of work.

It's an interesting challenge but I'm afraid I can't help much. Good luck!

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post #6 of 22 Old 08-23-2013, 04:06 PM
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Quote:
Originally Posted by dwightp View Post

.....Having said that, I'm not sure how any drawer slide that fits into your 7"-ish joist space is going to move your projector 13" below the ceiling. A 6" slide only gives you 6" of travel. An 8" slide only gives you 8" of travel.....

There are drawer slides that extend further than their closed length - called "over-travel" (or similar) - they typically use a three part slider.

Edit: Sorry missed your point completely - must be Friday! ....exactly as you were highlighting, the slides linked to in the OP's first post do expand to 15.5" but are only giving 7.5" of travel from their 8" closed length, not the 13"+ that are needed.....maybe ganging two together to give double the throw could be worth looking at?

[BTW, loved your cabinet!]
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post #7 of 22 Old 08-24-2013, 05:50 AM - Thread Starter
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I actually just realized what you guys are saying yesterday when I was working in the basement and thought I'd draw out a diagram. I also realized the ceiling joists are 2x10's not 2x8's so I have about 9"to work with. Would it be possible to attach two together drawer slides together or am I asking for more problems with binding etc?

The lab lifts I found won't extend far enough away but that idea with an electric motor and the thread could be interesting. I'm also trying to figure how I can manually open/access the projector if indeed something does go wrong. Last thing I want to do would be to take a hammer to the drywall and make an access panel after the fact!!

I did try to figure out how to do some type of pulley but I think the projector wouldn't be lowered into a fixed location, I'm afraid even slight movement would mess with the picture.

It really looks like my only option to fit this inside my ceiling and lower it the 13" needed is to buy some type of scissor arms, I just can't seem to find them anywhere.
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post #8 of 22 Old 08-24-2013, 06:21 AM
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tricky install, the desired drop and lack of depth really complicate this. Short of fabricating your own scissor arms, DGF's idea of stacked or ganged drawer slides seems feasible. No matter what, it will take a two step mechanism to drop a flush platform almost twice the distance of your available depth. Not sure that the lab jack will provide the range of travel or weight bearing capabilities in the installed position without modification. Good safety practices allow for at least a factor of 3 times the weight of the load you are suspending overhead, including the weight of the mounting hardware itself.
You probably already know this, but the commercial scissor lifts usually let gravity and the weight of the projector do all the work going down and travel is restricted and retraction provided by a motor driven nylon belt attached to the base. DGF also makes the excellent suggestion of making the installation accessible from the outside in case of malfunction.......just in case.
Please post pictures of the solution regardless. Here's to your pending creativity.

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post #9 of 22 Old 08-24-2013, 06:34 AM
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It might take a trip to the village machinist, if you don't have a drill press and some other fairly accurate tools, but a few pieces of 3/4" x 3/16" aluminum bar stock, some nylon bushings, etc, you could build a pair of scissor arms capable of the travel needed.

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post #10 of 22 Old 08-24-2013, 09:51 AM
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I have seen two drawer slides joined together to double the throw length, and they didn't bind (need to get decent quality slides though). One thing in your favor will be the weight of the 'sled' - this will help to overcome any hint of binding when lowering it, and stabilize things when raising the contraption (you'll need to have a lowering/raising mechanism that operates very squarely on the platform - attached either at all four corners or to the center - in order to minimize the possibility of skewing/binding).

I looked at the lab jack you linked to - does it not have the extension you need? As Weasel alluded to, you would be using the device "upside down" so some of the bearing loadings (like at the current base) will be the opposite to the way they were designed. The one shown weighs 13lbs, so that's one indication that it's pretty well constructed.

Which way are the joists running? If they're perpendicular to the screen then you could consider my (very poorly described) suggestion of a rear-hinged trapdoor-like assembly, especially now you have 'found' a couple more inches of room.
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post #11 of 22 Old 08-24-2013, 01:06 PM
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Will this work?

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post #12 of 22 Old 08-27-2013, 01:36 PM - Thread Starter
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First off let me thanks everyone for their input and apologize for the horrendous drawings, I’m a numbers guy not artistic!

DGF, the first picture is of what I think you were referring to in your post above. This does seem like the easiest solution however the projector is 9.6" without plugs etc. and my joists are only 9". In addition I don’t know that I could mount the projector that it would drop into position without hitting the floor joist across from it.

The second picture is another version of this. The projector would have to be upside down within the ceiling and somehow hinge down into a horizontal position. I don’t want it to be so complicated with two actuators etc. and am not certain I could get away it linking it all to one? I guess I could have a manual clasp but that takes away from the coolness factor.

Third option is to build some sort of scissors as discussed. This doesn’t “appear” to be too difficult. Go to a local machine shop and ask them to cut maybe 6-8 pieces of aluminum 1”x12” with holes on both ends. Then get some nylon washers and bolt them together.

Forth option is to band two sets of drawer slides together. Doesn’t “appear” to be difficult either but I’m not certain on how exactly to do this. I’m guessing I would have a good/metal block in between that they would both attached to. The first slide bolted within the ceiling would extend only enough to drop the second set to the ceiling height, then the second set would extend fully lowering within range. On another note do the below drawer slides appear to be a decent quality? They are about ½ the prices of the ones I found on eBay, I don’t want to have this build and then experience binding or uneven raising/lowering problems.

http://www.drawerslides.com/fulterer-5000-drawer-slide-zinc

Any thoughts or suggestions are GREATLY appreciated!!






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post #13 of 22 Old 08-27-2013, 02:03 PM
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With option four, I don't think you would use drawer glides. A linear slide set up would be fine and give you almost 7" of travel. You could probably make something out of 80/20 pretty easily.

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post #14 of 22 Old 08-27-2013, 02:14 PM
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The drawings were good!

Your example 1 was similar to what I was trying to describe, but I didn't envision needing to mount the PJ at 90 degrees to the 'trapdoor' - I was thinking of having the door swing down (say) 30 degrees, and having the projector mounted at 30 degrees to this, so that when the hinged door was fully lowered (by 30 degrees) the PJ would be level with the floor. However, it looks like your joists are running parallel with the screen, so you wouldn't get the 13" drop down from the ceiling you need. You might possibly be able to achieve the 13" if you were able to create an elongated trapdoor and hinge it one joist-bay back from where the PJ is located - the trapdoor would span two joist bays, with the projector housed in the one nearer to the screen. [It would be much simpler to draw this, but hopefully you get the idea!] I obviously don't know if this is feasible in your room, but it would potentially be the simplest to construct and maybe more reliable than some of the more complex variants.

Dave
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post #15 of 22 Old 08-27-2013, 02:16 PM
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Quote:
Originally Posted by Jasman View Post

Will this work?


I struggled the whole weekend to come up with a suitable retort to your post....but failed frown.gif ...it deserved better!
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post #16 of 22 Old 08-27-2013, 05:24 PM
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Blum and Accuride both make reliable, quality drawer glides. Have you checked these guys out for hardware?
http://woodworking.rockler.com/c/drawer-hardware
PS if you go the scissor route, you will also need the shop to drill a hole at the mid point intersection of each scissor to provide a pivot point.

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post #17 of 22 Old 08-28-2013, 11:24 AM - Thread Starter
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Gotcha, you mean like this? Two issues I have are I'm not sure how I'd measure the angle and drop to get it right...sure I could figure it out with some geometry and trial error though. This does seem to be the easiest method with less of a chance of slides binding or making a scissor lift with ?? potential problems.

My other issue is this would create a rather large panel in the ceiling, how do I go about hiding/making it look nice? The ceiling will be drywall but I don't want just a rectangular cut but on the other hand if I put some molding around it am I just drawing more attention to the ceiling?



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post #18 of 22 Old 08-28-2013, 12:36 PM
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Yup, that's what I was trying to describe! As you mentioned, this approach does require the biggest opening - approx. 16" bigger than any of the other alternatives. A 3' x 1' inset panel isn't that much more egregious than a 1.5' x 1' one, but finishing off any in-ceiling panel can be tricky - how were you thinking about doing it with the other options? - it's hard to answer the question without knowing your skills and confidence levels, and without seeing the room....

Drywall will cut cleanly with a blade, but you definitely want to put some form of edging (either hidden or obvious) on all the exposed faces - if left unfinished they will be a constant source of dust and will easily fray with the slightest knock from the trapdoor. If you are intending to use the cut-out piece as a part of the trapdoor make sure that you check out the location of the joins - you won't be able to change where you're cutting, but you'll know to take care that the cut-out doesn't accidentally fold in two while you're sawing!

To minimize how obvious it is, the fit of the door needs to be very precise - the edges need to be beveled inwards so that the visible join width is minimized and you prevent binding.

I've seen some well-hidden examples of in-ceiling doors that use a thin sheet of material (like tin/aluminum/ply) that is cut oversize, so that it extends beyond the actual opening on all sides - when retracted you just see a small raised lip and it blends in well with the original ceiling.

It's harder to hide the door on a solid-colored ceiling - a faux paint finish or some other visual distraction definitely helps.

[As an aside, I was wondering if a car hood hinge might achieve what you want? This type of mechanism swings "up & out" but without researching it, I have no idea if the geometry is anywhere near to being applicable to your situation.]

Dave
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post #19 of 22 Old 08-29-2013, 07:16 AM - Thread Starter
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I'm decently confident/skilled so if there is a good idea I'll figure it out myself or get a buddy etc to help if it's above my skill level. Below is my basic layout in excel, each cell is 1' and I'm still in the framing stage so any idea(s) are open now.

I was thinking of either a very thin border attached to the drop down or a thin larger piece as you suggested to cover the opening. It might be hard to do it the first way as my ceiling will be dry walled but the lift will also have a piece of plywood as the base AND then drywall covering it making it thicker than the rest of the ceiling. I'll check out the car hinge idea as that rear hinge may create the most problems for hiding the opening in the ceiling.

I did have someone from 80/20 contact me about making a scissor lift so I'll at least see what they have to say and report back.

layout_zpscf8aff39.jpg
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post #20 of 22 Old 08-29-2013, 07:08 PM
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http://www.draperinc.com/LiftsMounts/LiftProducts.asp?detail=777

Might keep an eye on ebay if one comes up.
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post #21 of 22 Old 08-30-2013, 06:03 AM - Thread Starter
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Yeah that would be perfect if I could get a steal on one!
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post #22 of 22 Old 12-26-2013, 04:58 PM
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Just use a linear actuator from Firgelli Automations, they sell actuators for just these types of applications. You just need a linear actuator, remote control, and power supply which they also sell.

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