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Old Mar 12, 2011, 09:49 PM
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The blade numbers go up to 11
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Sydney, Australia
Joined Aug 2002
4,478 Posts
Ron, the trick with servo operated gear doors is to make the holes in the linkage oversize and use small rare earth magnets to keep the doors shut. The oversize holes is so the magnets can shut the doors without fighting the servo, and it means you don't have to get the servo end points spot on as the magnets do the rest. It also means when the doors are closed there's no load on the servo, which is very important as you don't want the servo drawing current all the time. I used HS85MG servos for the big main doors on my Fei Bao F5E, just because I had them, but I'd recommend these:

or these:

I use them both in another model and they're great servos. I made my own sequencer, though, it plugs into the Rx and tells the doors to open, then the gear to come down, then closes the doors, and vice versa, and it regulates the speed of the doors to about 1 second opening or closing speed, which is important to reduce the load on the servo in flight (slam them open at full servo speed and the aerodynamic loads will be huge). Bear in mind that I can program my sequencer to limit the servo travel of each servo, so it makes life a bit easier. I can't believe that the electric gear manufacturers haven't some up with something like this themselves, it would make their gear much more usable in scale models. I've thought about making mine into a product but there's a lot of work to get in into a production item.

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