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Discussion Starter · #1 ·
I recently built a rocking chair that rocks on its own, using a Monster Guts wiper motor kit and some tutorials online. The issue I am having is that it keeps breaking the screw that anchors the arm to the motor. I loosened the connection and that helped but I still broke a second screw. I'm concerned about burning the motor out.

There also seems to be a little bit of a catch at the top of the rotation. I'm not sure why or how to fix that. Any help for a motor newbie? Photo of where the screw is breaking as well as a video linked below.

Rocking Chair

746342
 

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Keeper of Spider Hill
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Watching your video, I cannot see how you have configured the hardware holding the arm on. I’d put the bolt through the drive arm on the motor, then install a nut and tighten it down. This will keep the bolt straight and rigid as the assembly turns. Install a steel flat washer over the bolt, then a nylon washer, then your long drive arm, then another nylon washer, another steel washer and then a nut on the end. Use nuts with nylon locking inserts. This will keep them from coming loose or tightening on their own. You might need a slightly longer bolt. Hope this makes sense.
 

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I recently built a rocking chair that rocks on its own, using a Monster Guts wiper motor kit and some tutorials online. The issue I am having is that it keeps breaking the screw that anchors the arm to the motor. I loosened the connection and that helped but I still broke a second screw. I'm concerned about burning the motor out.

There also seems to be a little bit of a catch at the top of the rotation. I'm not sure why or how to fix that. Any help for a motor newbie? Photo of where the screw is breaking as well as a video linked below.

Rocking Chair

View attachment 746342
It may be the angle of view, but it looks like the push arm is at a slight angle to the chair. As though you would want to slide the motor toward the far side of the rocker (in 2D land, slide it up your screen). If you used a heim joint you would have more forgiveness in the overall alignment. They make some for RC cars that are not crazy money.
 

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Keeper of Spider Hill
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Not sure how long you've run this prop, but rocking chairs are notorious for "walking" as they rock. Since your motor assembly is not attached to the chair in any way, I'd want to make sure the chair does not walk and cause alignment issues. We had a Distortions Rocking Granny for a few years and I had to build a platform with guides on it keep the rocking chair from walking its way right off the shelf in our bay window. I think this occurs from the rails on the chair not being perfectly aligned.

Mechanical: - Rocking Granny Question
 

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Discussion Starter · #5 ·
Watching your video, I cannot see how you have configured the hardware holding the arm on. I’d put the bolt through the drive arm on the motor, then install a nut and tighten it down. This will keep the bolt straight and rigid as the assembly turns. Install a steel flat washer over the bolt, then a nylon washer, then your long drive arm, then another nylon washer, another steel washer and then a nut on the end. Use nuts with nylon locking inserts. This will keep them from coming loose or tightening on their own. You might need a slightly longer bolt. Hope this makes sense.
Here's a picture of my linkage. I think I have arm > flat steel washer > regular nut > drive arm > steel washer > nylon locking nut.

746377
 

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Discussion Starter · #6 ·
Not sure how long you've run this prop, but rocking chairs are notorious for "walking" as they rock. Since your motor assembly is not attached to the chair in any way, I'd want to make sure the chair does not walk and cause alignment issues. We had a Distortions Rocking Granny for a few years and I had to build a platform with guides on it keep the rocking chair from walking its way right off the shelf in our bay window. I think this occurs from the rails on the chair not being perfectly aligned.

Mechanical: - Rocking Granny Question
That's a great idea. I haven't given it a very lengthy test because the screw kept breaking, but if I mounted both the chair and the motor I could kill two birds with one stone and fix the alignment issue.
 

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Keeper of Spider Hill
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That's a great idea. I haven't given it a very lengthy test because the screw kept breaking, but if I mounted both the chair and the motor I could kill two birds with one stone and fix the alignment issue.
Yeah having the motor totally detached from the chair seems like a recipe for disaster. You might also try a different grade of hardware. Grade 5 possibly? I would not expect that prop to break bolts.
 

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Prince of Arkham Asylum
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So, I might not know what I'm talking about, but wouldn't it be easier to attach a deer motor to the center-bottom of the chair seat with a modest weight attached on a slightly extended arm? As the arm goes around in a circle under the seat it would extend the weight outward front to back and therefore rocking the chair? I know deer motors tend to be a bit cheaply constructed, but maybe there's a more bulked up version?
 
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