Is a single torsion spring garage door supposed to have a center bearing?

Disassembling my first torsion spring setup, on my 8'wide by 7'tall garage door, I just found something unexpected.
My single-spring 7'wide garage door doesn't have a center bearing.

Is that normal not to have a center bearing?

I have a bearing on each end, but no center bearing?

The reason I ask is that the center, when hand spun, with no weight on it other than the loose spring, has about a 1/4 inch sag in the center.

Seems to me, I was expecting a center bearing.
Can it be that single-spring torsion systems don't have center bearings?
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Danny D. wrote:

NO! That is missing the bearing, it MUST be on there!
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On Tue, 20 Nov 2012 11:47:55 -0600, G. Morgan wrote:

Dan Musick of DDM Garage Doors is kindly sending me a bearing.
The construction appears to be: a) There is air under the entire spring anchor plate. b) The spring anchor plate is bolted by 1 bolt to the angle iron. c) There is air below the angle iron except at the very top & bottom. d) There is air under both end bearing plates.
Given that, what appears to be happening (0.250" steel): A) As the door rolls up, the spring compresses 7.5 turns (~2") B) This (invisibly) pulls in both end bearing plates (hard to see) C) Which also visibly pulls in the spring anchor plate (~1")
Here is what I think the forces are:

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On Tue, 20 Nov 2012 19:54:59 +0000, Danny D. wrote:

New information!
This DASMA spring reference says there is a new solution to the bending forces on single torsion spring brackets: http://www.dasma.com/articles/tech/tips33.asp
It says (verbatim): "For a garage door using a single torsion spring, the spring bearing bracket ... is subjected to bending back and forth each time the spring winds and unwinds. This action not only stresses the bracket and ultimately its fasteners beyond capacity, but eventually can cause the bearing itself to fall apart."
One solution to explore might be a different kind of bracket: "Ken Martin...suggests that a double-flange, side-bearing bracket be used on single spring doors. He notes that this [double-flange side-bearing] bracket is normally fastened to both the top of the horizontal track angle and into the wall"
Googling for "double-flange side-bearing bracket", I don't find a definitive article - but I'll keep looking as that might be a solution in and of itself in my special circumstances.
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On Thu, 22 Nov 2012 17:25:21 +0000 (UTC), "Danny D."

You might be dealing with cheap original hardware. Or poorly fastened. Never saw a pic that showed if the entire bracket was moving. or it was just flexing. One other thing that I noticed taking a look at an older post to look at the bracket. DOOR CLOSED:
DOOR OPEN:

The spring is wound in the DOOR OPEN pic. Isn't that backwards? Anyway, I think others have posted pics of their single spring doors that show the spring bracket stiff. Seem the torsional forces on that bracket are always going to be no more than the weight of the door can apply, no matter what spring was used. Might be wrong on that, I'm not an engineer. That would point to a too-weak bracket/fastening. Might be age/fatigue, or poor initial quality. Personally, I would try a new or fabricated bracket of more strength. I tend toward fabricated, because it would give me an excuse to buy a drill press and a band saw. Others might go for welding gear. But you have to remove that drywall to get at good fastening points. Others may say fuggetaaboutit, and What, me worry? Happy Thanksgiving!
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On Thu, 22 Nov 2012 14:55:46 -0600, Vic Smith wrote:

I did snap a video - but it's hard to tell, in the video, exactly what is flexing. END PLATE:
http://www.youtube.com/watch?v=fHKjGDqz9wE
SPRING PLATE:
http://www.youtube.com/watch?v=DNAfZP1bMQM


This is a difficult thing to get my mind wrapped around. Pardon me if the explanation below is difficult to decipher.
You are correct that the spring should be close to RELAXED when the door is open. Well, the spring should be only a 1/4 or 1/2 turn tensioned at the door open position - but that's close to being relaxed.
However, we have the enigma that force bending the spring end plate happens ONLY in the door open position. Why?
This caused me a lot of confusion - but I think we have to consider the situation at the exact point when the spring was initially BOLTED to the hollow rod. The spring was bolted to the hollow rod AFTER it grew 7 coils.
So, the paradox is that the FORCE on the end plate now occurs NOT when the spring is tensioned - but when it is RELAXED.
This is a counter intuitive conclusion - but it's the only explanation that makes sense when trying to explain WHY the force is greatest when the spring is in the relaxed position.
If I'm wrong - please correct me as I'm also trying to figure out why the forces appear greatest when the spring is most relaxed!
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On Thu, 22 Nov 2012 14:55:46 -0600, Vic Smith wrote:

Actually, according to Dan at DDM Garage Doors, no spring anchor bracket is strong enough to withstand the forces from the relaxed spring.
In fact, Dan told me by phone that he has seen entire cripple studs ripped out of walls by these forces on the spring anchor bracket.
If I understood Dan correctly, what prevents the spring anchor bracket from moving is NOT the mounting of the spring anchor bracket. What prevents the spring anchor bracket from moving is the lack of movement in the two bearing end plates.
I don't quite UNDERSTAND that - but - Dan told me there is no way my spring anchor bracket would be moving unless the bearing end plates were also moving. He did not know about the air under my bearing end plates - so he surmised the fact that the bearing end plates were moving solely from the fact the spring anchor bracket was moving.
The interesting thing is that, while I can see the spring anchor bracket movement ... I can not see the bearing end plate movement: END PLATE:
http://www.youtube.com/watch?v=fHKjGDqz9wE
SPRING PLATE:
http://www.youtube.com/watch?v=DNAfZP1bMQM

But, Dan knew that the bearing end plate was moving.
I don't quite understand this ... but Dan's experience must be respected so I assume he's 100% correct. Especially since we all realize there is air underneath both of the bearing end plates.
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On Thu, 22 Nov 2012 14:55:46 -0600, Vic Smith wrote:

According to Dan, even a stronger spring anchor bracket would eventually fail unless I also fixed the flexing of the bearing end plates.
Of course, the spring anchor bracket is installed badly - so that's not helping things.

When the parts arrive from DDM Garage Doors, I plan on moving the spring anchor bracket angle iron 18" to the left so that it is mounted directly onto the cripple stud.
At the same time, I will (somehow) shore up the bearing end plates by either tying them to the studs a foot and a half distant ... or I will tie them to the steel horizontal track.
I'm waiting for the parts from Dan at DDM Garage Doors, who has already figured out what I need to do (even though I haven't figured it out yet).
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On Thu, 22 Nov 2012 14:55:46 -0600, Vic Smith wrote:

Happy Thanksgiving to you too!
I made pumpkin pie, from scratch!

The kids wouldn't touch it ... even though it used their carved pumpkins for the guts ... and they loved the seeds ... but they just wouldn't touch my 'experimental' pumpkin pie!
Oh well ... yet another family day!
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