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Need some help from the auto-rotating monitor experts...

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nitz:
No problem at all, I'm enjoying the discussion...even if most of it is over my head. ;)

Le Chuck:

--- Quote from: DNA Dan on March 17, 2012, 06:57:57 pm ---
--- Quote from: RandyT on March 17, 2012, 01:50:18 pm ---The simplest device I can think of is a round piece of MDF used as a monitor mount, with a shaft going to two bearings acting as an axle.  This will turn very easily.


--- End quote ---

That is precisely what I had in mind. Looking for "light duty bearings" the flange mount typically only has 2 holes.
http://www.thebigbearingstore.com/servlet/the-1067/1-fdsh-2%22-Light-Duty-Two/Detail

That might be strong enough, but I was wondering if you think the 3 or 4 hole flanges are necessary? Also, these aren't "light duty" type bearings, they have thicker grease in them, do you think this is too much drag? Such as these: http://www.thebigbearingstore.com/fourboltflangebearing.html

Sorry for the hijack Nitz, just drop any questions if need help.

--- End quote ---

I'm using a similar model minus the grease zerk for another application but those are fantastic bearings.  If I was doing an axle mounted monitor I'd go with a four hole just because I'd probably be working with a substrate that would need the added support. 

DNA Dan:
I'm sure I could put some lighter weight grease in there if the drag seems excessive. I agree the 4 hole seems like a better strategy especially if there is some wobble in the rotation.

Do you think 6 seconds is too long for a rotation switch? The pololu linear actuators are nice because they have built in potentiometers for feedback if used with the JRK modules. Plus they're ~30% off right now.

DNA Dan:
If I can get the double flange bearing with an axle shaft working it might be cheaper to just slap a sprocket on there with some chain and drive it directly. I could then get a motor with feedback position (how's that working out for you Jimmy?)

What I am trying to accomplish is a system that eliminates the need for limit switches and a tension type aparatus.

I just realized you have to center the rotation no matter how balanced or unbalanced the monitor is on the center point. Reason being is the bezel will be off in L/R or T/B if you offset the rotation to balance it. Basically you need to counterweight the aparatus once it's completed. I didn't have this issue the first time I did this because the mount was completely centered on the monitor and balanced perfectly. I am going to use a smaller monitor that has built in speakers I can cannibalize for sound which was a "leaner" type style, not mounted on a VESA compliant monitor stand. I am also going to make it "inset" in the disk to decrease the depth of the cab and make the bezel gluing easier.

I think I am in love .... http://www.robotmarketplace.com/store.html  Excellent place for the mechanical parts/gears/etc.

Le Chuck:
Dan, kinda spitballing based on what you're saying but if you just use a second flangette locking collar bearing behind the first one spaced, oh, maybe 6 to 8 inches back and I would think that would take enough of the stress off the center collar to get your rotating smoothly w/out a counterbalance.  I think the $8 for a second bearing would be worth the trouble even compared to the price of free for a thick-ass peice of rusty iron you can bolt onto the ass of the axle to balance it out.
  
I like the linear actuator for rotation but I still think that a direct driving servo would be easier and faster.  I think 6 seconds would start to get one your nerves after a while.  The whole point is to get this as unobtrusive as possible and 6 seconds can be a long time, just ask a bull rider.  It's an untested theory but for $40 bucks the GWS Giant Servo should have the ass to do a CRT rotation condsidering it pushes 30kg at 6v.  Save you some dough over linear too.  When I do this I'm going to mill a collar that I can screw directly onto the servo output so I don't loose power through an actuating arm.

<edited to include example servo and adjusted cost> 

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