Bent Gate Stem
Bent Gate Stem
(OP)
Hi there,
I have a question about a bent gate stem used in the operation of a dam gate structure. The stem is threaded stainless steel and is raised a lowered via a geared system. One of the stems is out-of-plumb by approximately 1/16 of an inch. My question is will this bend affect the torque required to operate the gate? We are concerned that this bend will make operation a challenge, however do not have anything quantifiable to confirm that. Does anyone have any experience with this kind of situation and can offer even an explanation of whether a bent stem like this is a concern?
Thanks
I have a question about a bent gate stem used in the operation of a dam gate structure. The stem is threaded stainless steel and is raised a lowered via a geared system. One of the stems is out-of-plumb by approximately 1/16 of an inch. My question is will this bend affect the torque required to operate the gate? We are concerned that this bend will make operation a challenge, however do not have anything quantifiable to confirm that. Does anyone have any experience with this kind of situation and can offer even an explanation of whether a bent stem like this is a concern?
Thanks





RE: Bent Gate Stem
If the rod is in compression at any time then yes, especially if fairly slender, the propensity to buckle increases even with very small initial deflections.
A lot depends on length, diameter, other items holding it out of position etc, none of which we know other than it is 1/16" out of plumb.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Bent Gate Stem
RE: Bent Gate Stem
The stem is actually bent. The stem is an old stem that the owner is considering trying to salvage. The stems raise into aluminum stem covers.
RE: Bent Gate Stem
Are the fixed threaded supports (for the threaded rod) themselves fixed, or do they pivot as the gate moves?
RE: Bent Gate Stem
RE: Bent Gate Stem
Is it a gentle bend? What does the grated operator look like? I'm finding it difficult to see how there isn't 1/16"of give or flexibility in this system.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Bent Gate Stem
I believe we will suggest to have it straightened if possible.
Thank you all for your responses.
RE: Bent Gate Stem
Yeah, my brain went in that direction, too.
Note that I have zero professional experience in this area. However, I do not believe that the .030" spec noted above can be applied to the straightness of the screw, it just doesn't make sense. That's not how the spec reads, either, in my opinion. For example, a quick peek at McMaster-Carr shows that some off-the-shelf, ground, linear bearing shafts have a straightness tolerance of .002 per foot.
164 inches ==> 13.7 feet ==> .0273 straightness error (and this is precision ground shafting, not a rough service screw that spends decades in the weather doing a crude task)
"Alignment of operating machinery and supporting components" is not the same as straightness of the screw. In this arena, I'm a nobody, but I have strong doubts about the numbers being thrown around here.
RE: Bent Gate Stem
RE: Bent Gate Stem
RE: Bent Gate Stem
RE: Bent Gate Stem
RE: Bent Gate Stem
I agree, it seems like a small bend and probably not an issue but, in my opinion hardly worth trying.
this is a dam and the gate is on the water side, generally below the ordinary high water line. installing or removing a gate would be done by divers or by lowering the reservoir and possibly working from a barge. If it binds during operation it may possibly jeopardize normal operation during a flood stage. If this is a gate on a penstock than dewatering the penstock would be difficult. all good reasons to make sure it works the first time.
RE: Bent Gate Stem
My guess I'd that at some point this gate got jammed with some gunk and the rod went into compression.
If this gate arrangement is fixed to a value of less than an inch I would be astonished. A system like this that doesn't allow for some lateral movement of the gate is going to jam very easily. I'm really struggling with this one being an actual problem.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Bent Gate Stem
I think it's also important to know if the slight bend really tells the whole story. The screw could be damaged more than it shows, because it's already binding and the structure of the thing is fighting the screw and winning, springing the screw back to a straight-ish condition.
In other words, how bent would the screw be if it was out of service, just sitting on a workbench?
RE: Bent Gate Stem
Thanks again to you all!