I'm working on a museum exhibit where a 65" plasma monitor (150lb) is manually moved back and forth along a 15' linear rail. We're looking for a passive (non-electronic) means of limiting the speed to thwart kids flinging the screen from one end to the other. We want the screen to move freely at slow speeds but max out at ~0.5 ft/s. I may be wrong but the long 15' run and seems to preclude using a cylinder. Are there stock solutions to this problem? As always, any advice is much appreciated.
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Speed Damping Mechanisms?
- Thread starter futnuh
- Start date
With a copper bar (6 inch) in a 210 magnet rail, I found the drag force to be 2.5 lb.in/sec.
Although there is fringing, most of the magnetic field is contained in the "U" of the magnet rail. Things have to bee pretty close to be affected by the magnetic field.
Although there is fringing, most of the magnetic field is contained in the "U" of the magnet rail. Things have to bee pretty close to be affected by the magnetic field.
- Thread starter
- #22
Thanks tlee123. Regarding shock absorbers, to keep the original question simple I neglected to mention that we need the screen to come to a definite stop at the end. This would trigger a position lock (either solenoid or electromagnetic) and then playback of a final 30 seconds of animation.
As you point out, a fixed end stop is going to cause a harsh impact (even at our desired max of 0.5 ft/s). We might have to rethink the design - perhaps a motor-positioned screen and a separate slide control. Bumping a separate slider into an end stop wouldn't be an issue. Further, the slide would become a target location for the screen (which can lag at its max velocity). At the end, we could "ease" the screen into position.
Thanks to everyone for the suggestions. This is our first experience in eng-tips - what a great online community.
As you point out, a fixed end stop is going to cause a harsh impact (even at our desired max of 0.5 ft/s). We might have to rethink the design - perhaps a motor-positioned screen and a separate slide control. Bumping a separate slider into an end stop wouldn't be an issue. Further, the slide would become a target location for the screen (which can lag at its max velocity). At the end, we could "ease" the screen into position.
Thanks to everyone for the suggestions. This is our first experience in eng-tips - what a great online community.
sreid, I was surprised to hear you got that much damping from the eddy current device. Thanks for the info.
I looked into the magnet track from Parker/Trilogy. It's pretty neat that you can buy long lengths or modular. However, the tracks are expensive. A 48" long pc is $2500-$2700 (210 style) and futnuh would need about 4 of them. Being non-contact, it would never wear out, so I imagine the cost would be justified only if it saw constant usage.
I looked into the magnet track from Parker/Trilogy. It's pretty neat that you can buy long lengths or modular. However, the tracks are expensive. A 48" long pc is $2500-$2700 (210 style) and futnuh would need about 4 of them. Being non-contact, it would never wear out, so I imagine the cost would be justified only if it saw constant usage.
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