The Droll Yankee Flipper is one of the best-known squirrel-proof bird feeders.
When a squirrel puts its weight on the perch, it activates a motor which rotates the perch, thereby flipping the squirrel off; hence the name Yankee Flipper.
The mechanism runs on a rechargeable NiCad battery and both the battery and charger are included.
Droll Yankee makes a couple of different feeders, and the Flipper is just one of them.
Some things to consider:
All batteries tend to perform poorly in cold weather, so the Droll Yankee Flipper may not perform as expected year-round.
The batteries also mean that the feeder won’t function while you are charging them for a few hours.
Any feeder that relies on movement is subject to the elements. For example, a freezing rain may prevent the Flipper from flipping.
> Tube feeders, such as the Droll Yankee Flipper, are not totally waterproof. The seeds at the bottom tend to get soggy during a rain.
The perch is calibrated specifically for a gray squirrel and cannot be adjusted. So it won’t work for a red squirrel or chipmunk.
With that said, here are some advantages of the Droll Yankee Flipper:
It is one of the most entertaining of the motorized squirrel-proof feeders. How often will the squirrel be thrown before giving up? (Your cat will enjoying watching it, too.)
The motorized action insures that the squirrel never lingers on the feeder long enough to try to chew through it.
It is very effective in keeping the squirrels off.
If you do purchase the Droll Yankee Flipper, hang it where the squirrel cannot be injured when he falls. Over level ground should be fine.
Here are some online places to find it:
The Bird Shed
Yardiac

Have misplaced instruction book. Many times, the ring will turn and toss the squirrel off but sometimes, the squirrel(small) can sit on the ring which will not activate. Batteries new and fullly charged. Is there a way to change the pressure required to activate the ring?.
I found some instructions online:
http://www.yankeeflipper.com/droll/manual/print_instructions.cfm
It doesn’t look like the ring action is adjustable. How long have you had it? It may be a defective unit. Have you checked with Droll Yankee to see if it is still under warranty?