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phlegma
08-09-2007, 03:00 PM
Hey guys,
I'm looking for an inexpensive way to drop and return a falling prop. The timer is not the issue, but some sort of mechanism / motor that can wind up, but also release it's torque so that it may then spin the reverse way by the weight of the prop.

Also looking for just an inexpensive reversible, low speed motor. That can be flipped one way to open a door, and another to close it.

Thanks for your support!

gadget-evilusions
08-10-2007, 04:52 AM
IT would be 100 times easier to use pneumatics for both applications!!

phlegma
08-10-2007, 08:38 AM
true, but how could that be done? considering that the prop is falling instead of rising, an air cannon wouldn't really do the trick...

what if an air cannon, mounted on the floor, was attached to a pulley system that liked the the prop. a counterweight held the prop to the ceiling, but the blast of air was powerful enough to override the counterweight. it would then automatically rerise after the air was dead.

any thoughts?

thanks again!

gadget-evilusions
08-11-2007, 06:45 AM
Pneumatics are not just air cannons. When I have a falling prop ( you didn't specify exactly what you were doing) I do two things, I use a long stoke double acting cylinder, one end mounted to the wall or ceiling, the other to the prop, or I use the cylinder to pull 1/4" air craft cable through pulleys, cylinder goes in pulls the cable, prop goes up, cylinder goes out, cable allows prop to drop. Give me some specifics and I will help you out more.

phlegma
08-11-2007, 11:14 AM
I see what you mean, we're basically running the same idea, except you mentioned the double acting cylinder.

Check out this drawing: http://theriddleremedy.com/carrieroom.jpg

gadget-evilusions
08-15-2007, 05:10 AM
Yes, that's pretty much the idea, except that you can simplify it even more by using a double acting cylinder and not having to use a weight to reset. With a double acting cylinder you will get control of the exact speed of descent, and ascent with flow controls either on the cylinder or exhaust metering fittings on the valve, and you can regulate down the pressure to only use what you need to move it at an acceptable speed (but not using pressure to control the speed, just the force). The less pressure you use the less air you consume and the less stress on your compressors.