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dummy rotary engine

Old 03-09-2017, 11:44 PM
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jugglingtony
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Default dummy rotary engine

Has anyone tried fixing dummy cylinders to the case of an outrunner motor for genuine rotary engine simulation?
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Old 03-10-2017, 12:32 AM
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Bald Paul
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It would make a good 3D printer project!
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Old 03-10-2017, 01:21 AM
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subzJC
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http://www.wattflyer.com/forums/show...ight=ballerina

at the bottom of this thread this man printed a nice one.

may want to ask him about it.
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Old 03-10-2017, 05:17 AM
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Read on a forum somewhere that someone did. One cylinder flew off due to the high rotational speed and that led to serious vibration.

Problem is the difference in rotation speeds. A rotary engine operated at around 1,200 rpm and for a scale speed the outrunner would need either to be slowed way down for a direct mount or have some sort of reduction system fitted for the rotary part. There might be an outrunner out there that could provide usable thrust at 1,200 rpm but I'm not aware of it.

You'd also have to deal with the increases in weight, drag, and torque. I seem to recall that the WW1 planes fitted with rotories would turn readily with the torque but would struggle to turn the other way. The opposition pilots knew this and used this limitation against them.

If you try it, keep us posted.
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Old 03-12-2017, 07:35 PM
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quorneng
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Do you mean like this?

Its doing about 7000 rpm. There is a big difference in the centripetal force between a full size engine and a model.
The cylinders are paper tubes with cotton wound round for the fins and are glued directly onto the out runner bell. The whole 'engine' only adds about 2.5 g
Yes, it absorbs a bit of power but well worth it for the scale effect.
The rotary in the finished 24" span Sopwith Pup.
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Old 03-12-2017, 08:06 PM
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Very fine job there. Thanks for posting.

This isn't the one i was thinking of, and your success negates some of my cautions. Seems now worth a try.

Bill
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Old 03-13-2017, 11:36 AM
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That's so cool! I'm building a 1:6.5 Fokker D8, and started thinking about how to represent the rotary. It is a lot bigger than the Pup, and forces would be higher. Balancing would be critical of course. Since i first posted the query, I thought about having the cylinders rotating on a separate bearing and using a turbine (hidden behind the motor) to spin them from the airflow, obviating problems with high revs, and strength. We'll see....
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Old 03-13-2017, 11:45 AM
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quorneng
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There was a bigger 1/6 scale DH2 that used a "free running" rotary relying just on the bearing friction to turn it. Sort of self speed limiting.
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Old 04-15-2017, 12:44 AM
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I was reading through some old magazines and found this:

from Airborne #63, May-June 1984, Brian Winch's wonderful column The Airborne Engin-ear.
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