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lyd
Joined: 15 Sep 2007
Posts: 390
Location: Lake Mills, Wi
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| Posted: Sat Oct 27, 2007 11:21 pm Post subject: How sensitive will a ceiling mount be to shock from above? |
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Somewhere in the middle of this process some new neighbors moved in upstairs, and there seem to be a number of small children involved.
I'm not sure whether it is those children or not, but as I sit here typing this it sounds a bit like a bison playing soccer up there.
Am I going to experience serious problems maintaining adjustment if I have this much vibration being transmitted from above, or will the hanging nature of the unistrut mount make it less of an issue? Is there anything you would suggest, mounting-wise, to mitigate it further?
Thanks.
lyd
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Elaine Benes
Joined: 25 Apr 2006
Posts: 1416
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| Posted: Sun Oct 28, 2007 12:45 am Post subject: |
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Its an issue.
When my lovely wife is walking around our kitchen(right above the projectors mount) the picture often shakes. It doesn't affect convergence/setup, but its awfully annoying at times when watching...
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Zebu Fellenz
Joined: 21 Dec 2006
Posts: 2567
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| Posted: Sun Oct 28, 2007 1:33 am Post subject: |
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It really depends on what the floor above you is made of and how stiff it is, put your hand on the ceiling when sounds like they are really moving and see if you can feel the vibration; if you can, then yes I bet it will be an issue
Erik
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bomrat
Joined: 10 Mar 2006
Posts: 117
Location: chicago
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| Posted: Sun Oct 28, 2007 2:01 am Post subject: |
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it depends on how stiff the house is and how soft the wife is.. or like my x, she heel toe's everybody, sounds like a damn train going through the house.
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lyd
Joined: 15 Sep 2007
Posts: 390
Location: Lake Mills, Wi
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| Posted: Sun Oct 28, 2007 2:20 am Post subject: |
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I can absolutely feel the vibration, significantly.
I am going to look into some sort of decoupling solution. I have found a few things so far, but most of them are intended for digi projectors and have nowhere near the load capacity that I need. The most likely candidate at this point is this from OmniMount:
Ceiling Vibration Isolators are typically fastened between two lengths of 3/8" - 5/8" threaded rod, one to the ceiling and one to the mount
Looks good, although I haven't found engineering data on it yet, but at ~$60 a piece, forget about it.
Having established this as a basic idea for the design, though, I think I might be able to put together something myself, if I don't find a ready-made option for a more reasonable price.
Please don't hesitate to chime in if you know of something or have a better way to do it.
My final design for the unistrut mount turned out to be longer pieces running perpendicular to the joists and fastened into 4 each, so hopefully that will help distribute the effects of any vibration a bit as well.
lyd
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Sun Oct 28, 2007 3:14 am Post subject: |
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| lyd wrote: | I can absolutely feel the vibration, significantly.
I am going to look into some sort of decoupling solution. I have found a few things so far, but most of them are intended for digi projectors and have nowhere near the load capacity that I need. The most likely candidate at this point is this from OmniMount:
Ceiling Vibration Isolators are typically fastened between two lengths of 3/8" - 5/8" threaded rod, one to the ceiling and one to the mount
Looks good, although I haven't found engineering data on it yet, but at ~$60 a piece, forget about it.
Having established this as a basic idea for the design, though, I think I might be able to put together something myself, if I don't find a ready-made option for a more reasonable price.
Please don't hesitate to chime in if you know of something or have a better way to do it.
My final design for the unistrut mount turned out to be longer pieces running perpendicular to the joists and fastened into 4 each, so hopefully that will help distribute the effects of any vibration a bit as well.
lyd |
All those parts can be fund in an automobile. I'd use valve springs ( or two stacked for more load capacity ) the bushing that's attached to the celing side looks like an altenator bushing and the bracket can be made from a piece of flat bar stock using a bench vise and a hammer. Add a couple of flat washers and you're done.
Not sure though what the load capacity of the valve springs are. IT would be a fun experiment to try.
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HD done right!
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lyd
Joined: 15 Sep 2007
Posts: 390
Location: Lake Mills, Wi
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| Posted: Sun Oct 28, 2007 5:10 am Post subject: |
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I agree that auto parts are probably an easy source for the components. I was thinking of those urethane sway-bar bushings, but same general idea.
This seems to be the real stuff, though. I am going to look into sourcing.
lyd
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stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
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| Posted: Sun Oct 28, 2007 11:09 am Post subject: |
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First, hearing that someone just moved in over you leeds me to think that you are renting. If so, you don't want to do anything to the ceiling without the owners permission. Second, if it's that bad, I'd consider table mounting it. The vibration will not only will it mess up the picture but could loosen chips on boards, or the boards themselves.
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A Barco is only a AmPro with training wheels
Card carrying member of the AVS chain gang.
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lyd
Joined: 15 Sep 2007
Posts: 390
Location: Lake Mills, Wi
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| Posted: Sun Oct 28, 2007 12:27 pm Post subject: |
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| stefuel wrote: | | First, hearing that someone just moved in over you leeds me to think that you are renting. If so, you don't want to do anything to the ceiling without the owners permission. |
Its a bit late for that, I've already removed a (totally superfluous) light fixture and patched the giant hole that was underneath it. It is really not a problem in my situation, though. As long as I patch and prime the subsequent holes from the bolts when I move out, there's no trouble.
| Quote: | | Second, if it's that bad, I'd consider table mounting it. The vibration will not only will it mess up the picture but could loosen chips on boards, or the boards themselves. |
Well, my original plan had been to table mount it, to be possibly followed later by some sort of scaffolding to get it overhead. I was persuaded to do otherwise by various old and new postings on the topic in these forums.
And rightly so, I think, except for this vibration issue. A floor mount would not work well at all in this space, resulting in really sub-optimal seating positions in the best case.
If vibration from above causes a lot of ongoing problems for me, even using some sort of isolation hanger, I may need to reconsider and try something else, but at this point I am willing to give it a shot.
lyd
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tri_joel
Joined: 03 Jul 2007
Posts: 646
Location: Northern Virginia
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| Posted: Mon Oct 29, 2007 1:18 pm Post subject: |
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You can buy spring isolators at a plumbing supply store. You will need to know the weight at each point to ensure you get the correct size spring.
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lyd
Joined: 15 Sep 2007
Posts: 390
Location: Lake Mills, Wi
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| Posted: Mon Oct 29, 2007 9:44 pm Post subject: |
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| tri_joel wrote: | | You will need to know the weight at each point to ensure you get the correct size spring. |
That was my next question  . Since I haven't received the projector yet, I cant weigh it myself at this time to try to determine the distribution. Has anyone else already done this?
I know that it is about 150 lbs total (at least according to the spec sheet pdf on Curt's site), and that it will of course be heavier in front. I just need to know how much heavier.
lyd
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tri_joel
Joined: 03 Jul 2007
Posts: 646
Location: Northern Virginia
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| Posted: Tue Oct 30, 2007 2:39 pm Post subject: |
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In a perfect world you would want to mount the PJ so the majority of the weight is at a balance point somewhere near the front to middle of the PJ. This will allow you to adjust the the PJ up and down for mechanical set-up. I discovered how well this works with my PG9, it has a balanced mounting point built in. To adjust the height and to stabilize the PJ I adjust the front and rear mounting bolts (all-thread in my case) which have almost no weight on them. In a balanced mounting position your point weights will be the weight of the PJ divided by 2. A 150# PJ would need 75# isolation springs. I would then use a neoprene isolator at the four corners where you adjust and hold the mechanical aim for height.
Clear as mud?
I am working on a design for a universal ceiling mounting bracket with built-in vibration isolators. I have been tossing around lifting mechanisms for those of us with low ceilings and no room for an electric wench (er I mean winch = ) ).
Please let me know what you end up doing and how well your system works.
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lyd
Joined: 15 Sep 2007
Posts: 390
Location: Lake Mills, Wi
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| Posted: Wed Oct 31, 2007 10:38 am Post subject: |
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| tri_joel wrote: | In a perfect world you would want to mount the PJ so the majority of the weight is at a balance point somewhere near the front to middle of the PJ. This will allow you to adjust the the PJ up and down for mechanical set-up. I discovered how well this works with my PG9, it has a balanced mounting point built in. To adjust the height and to stabilize the PJ I adjust the front and rear mounting bolts (all-thread in my case) which have almost no weight on them. In a balanced mounting position your point weights will be the weight of the PJ divided by 2. A 150# PJ would need 75# isolation springs. I would then use a neoprene isolator at the four corners where you adjust and hold the mechanical aim for height.
Clear as mud?
I am working on a design for a universal ceiling mounting bracket with built-in vibration isolators. I have been tossing around lifting mechanisms for those of us with low ceilings and no room for an electric wench (er I mean winch = ) ).
Please let me know what you end up doing and how well your system works. |
I'm not following that at all. The bolts have almost no weight on them? Balanced or not, the bolts will be supporting the weight of the projector, right? I also don't understand your total weight divided by 2 calculation. Even if the load were equally distributed among all four threaded rods, which would mean they were bunched up quite close to the front, there are still four of them. So you would divide by 4 to get the weight on each bolt, no?
As it is, it doesn't seem really practical to try to balance it that way, at least with this projector. The mounting holes are not balanced at all, as far as I can see.
The strut on the ceiling will be perpendicular to the projector (side-to-side rather the front-to-back), the hanging strut will be parallel. I could achieve equal weight on each rod by mounting the two on the ceiling very close together and very far forward relative to the projector, but I don't know if that makes the most sense...
lyd
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tri_joel
Joined: 03 Jul 2007
Posts: 646
Location: Northern Virginia
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| Posted: Wed Oct 31, 2007 2:29 pm Post subject: |
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Okay, let me see if I can explain a little more clearly.
If you were to attach a third unistrut to the ceiling above the approximate balancing point then have a total of six pieces of all-thread, the two attached over the balancing point would carry all of the weight. The two in the front and the two in the back would only work to achieve vertical mechanical alignment (they will in effect carry a small portion of the load).
So now you have a total of six mounting points with almost all of the load on two points, so the spring isolator rating would be the total weight divided by two. The two spring isolators would be located on the two center pieces of all-thread. For the four corner points I would use a neoprene type isolator or four light weight springs.
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lyd
Joined: 15 Sep 2007
Posts: 390
Location: Lake Mills, Wi
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| Posted: Thu Nov 01, 2007 1:46 am Post subject: |
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Aha!
Gotcha now. That makes perfect sense, thanks.
I don't think it's the route I want to go for this, though. For my situation it seems like I'll be better off sticking with 4 points only.
lyd
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Fujifrontier
Joined: 20 Oct 2007
Posts: 354
Location: San Antonio, Texas
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| Posted: Sat Nov 03, 2007 2:22 am Post subject: |
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a much simpler solution would be to make the children disappear 
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