Not sure about the noise yet. We’ll see about that during the tests. Yes, the body is an obstruction, the RPM on the 2nd propellers will be higher than on the front ones. There’s no obstruction there, they’re going to work in conjunction.
No, they don’t. They are just protections. To have an improvement in efficiency, the shape of a ducted fan has to be very different.
So far I don’t see any reason the design would be a problem to launch, whichever way you decide.
Ducted regular propellers are not ideal. The best design is ducted fans, with particular shape, like the ones on turbofan jet airplanes, with 12 blades or more. Some EDFs have 5 blades, but they are noisier. The blades shape also has impact on the noise level.
The more I think about this idea, the more I think it’s great. The wings would fold/unfold by servos activated by the throttle or a torque controlled hinge to make a smooth transition that takes around 2 or 3 seconds to fully fold or unfold. The wings in folded position would reduce the drag quite considerably.
Hi Mateo! I didn’t see your post before now. It’s cool we have the same concept in mind. I’m at work right now and I’ll read the whole topic at night and I’ll comment more. Cheers!
That shaft-within-shaft was created to be used in airplanes I guess, with paramotors it’s not necessary and it’s a lot easier and cheaper to use opposed motors.
I think you should come up with a way to make the arms open and close softly using just the thrust. Similar to a door with a pneumatic piston.
That particular guard design would most likely increase drag quite considerably when folded. With a different guard design I agree the drag could be reduced.
I’ve been thinking a lot about concepts like this for more efficient soaring with the motor but I started to lean more towards just reducing the drag of the overall unit without it folding up. Any improvements made there would improve the efficiency of both the glide AND the powered flight.
I’ve also implemented several ways to make setup and tear down of the OpenPPG quicker and easier than it already is… it really doesn’t take long to set it up as is. Too bad we can’t just fold the net and hoop and arms up like an umbrella. One of these days I’ll get a concept like that figured out… maybe even get it to fold that way during flight.
They could be mechanically linked in such a way that the angle would always be the same between each side. Then they would open and close simultaneously and you would only need one piston or one servo.
@RogerThat
Hello
The first thing to do is to make some preliminary experiments on a bench
One system
2 motors possibly 180 rpm/V or 160 rpm/V
2 contra-rotating props Tiger 26x8.5 , 3 blades
2 ESC
Battery V1=12S, V2=14S (for example, to get two sets of results)
Testings on V1 and V2, on the bench
one prop : rpm1 (WOT), voltage V , amps I, Static thrust 1
two contra props : rpm1 & rpm2, voltage V, amps 1 & 2 , Static thrust 2 (total)
The objective is to get around 25 kgf static thrust (per system)
Probably (?) the rpm have to be in the 5000-5200 rpm range
Louis
Hi RogerThat,
Have not read the thread but, seeing that the term “shroud” is missing here, I assume the problem with shrouds could be not known here.
Well, the rings around your props are called shrouds (longer versions for EDF fans are usually called ducts). There are some pretty serious challenges related to the use of shrouds if you want them to work as they should. Since I have recently watched a vid on YT, I would suggest you and anyone who is serious about engineering to watch it. Its called “Master Lecture: Ducted Lift Fans w/ Bob Parks”
This is Boeing’s GoFlyPrize channel video. The channel has exceptionally well made and informative contents of aerospace engineering basics with the particular emphasis on eVTOL (Electric Vertical Take Off and Landing) aircrafts. Highly suggest for anyone!
Also, for flight mode at low speeds (in the PPG case), reducing prop diameter, going higher disc loading and higher rpm ONLY decreases efficiency. I suggest watching a nice lecture about props and CHEAP DIY versions of large dia props. “HUGE Drone Propellers - Build or Buy?”
Again, exceptional quality of video contents. One of the best engineering channel I know in terms of quality.
