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Old Jun 05, 2016, 06:06 AM
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Question
Reverse Thrust for Small Airstrip?

Just wondering if anybody has tried reversing the fan rotation to achieve reverse thrust. I know the real guys use cascades or buckets, but merely reversing seems easier for electric.
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Old Jun 05, 2016, 07:51 AM
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I'm not aware of any ESCs designed for aircraft that have a reverse mode ... only surface controllers suppport reverse.
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Old Jun 05, 2016, 12:05 PM
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Quote:
Originally Posted by tkallev View Post
I'm not aware of any ESCs designed for aircraft that have a reverse mode ... only surface controllers suppport reverse.
There are a few multirotor escs that can do reverse rotation.
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Old Jun 05, 2016, 02:26 PM
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There were some larger fans that had reversing but I doubt their effectiveness. I think it was HSD or TAFT models. Brakes on the wheels is very effective. You can buy electric brakes or make mechanical paddles to rub on the tire. Both work well.
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Old Jun 05, 2016, 06:16 PM
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Some 10 years back I created weird braking system with specially designed servo arms to rub against tires on my large IC powered "C-130, Herc" to keep it stationary at low idle of all four power units, it worked great for a while till the arm cut into the tires just as the cutting knife on the lathe! Wish I had the picture of those tires,
Now converted into electric no such issue as wanting to taxi during the idle.
I hate to see the stress of the E-motor to put it into reverse thrust, but you could always copy the system they use on full size airliners, the bloke did pretty nice job of it in 3/D printing, tho only as a desk toy not practical in real terms, Good luck!
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Old Jun 06, 2016, 05:01 AM
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Reverse thrust J10 video - https://www.youtube.com/watch?time_c...&v=bM79Jd6ckMw
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Old Jun 06, 2016, 05:18 AM
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It could certainly be done with a 2 pole two way switch controlled by a servo to reverse two of the motor wires although a suitable high amp switch is likely to be relatively heavy.

Probably not a good idea to reverse the EDF when under power though!
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Old Jun 06, 2016, 06:58 AM
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http://www.bananahobby.com/120a-brus...ueryId=1793522

This ESC will do reverse thrust.

It automatically does motor braking to bring the motor to a stop before reversing direction, so you just flip a switch.

Note: It doesn't give you much thrust.
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Old Jun 06, 2016, 07:53 AM
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If you're running any sort of lightweight thrust tube, it'll collapse on you.

As already mentioned, brakes are simple and very effective.
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Old Jun 06, 2016, 06:00 PM
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Quote:
Originally Posted by Quorneng View Post
It could certainly be done with a 2 pole two way switch controlled by a servo to reverse two of the motor wires although a suitable high amp switch is likely to be relatively heavy.

Probably not a good idea to reverse the EDF when under power though!
Firstly, the rotor spinning in opposite direction wouldn't be very efficient and secondly the rotor nut would get lose and undone!
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Old Jun 06, 2016, 06:15 PM
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Add a brake chute (Servo controlled - three settings: Retracted, Deployed - and Released, so you are able to drop the chute if wrongly deployed up in the air) . Much easier and works fine. It also adds a kind of scale touch for jet landings.
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Old Jun 07, 2016, 03:25 AM
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That sounds great, it would look fantastic with models like "Black Bird", I have never seen video of such a landing with RC model, anyone?
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Old Jun 07, 2016, 04:51 AM
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Quote:
http://www.bananahobby.com/120a-brus...ueryId=1793522

This ESC will do reverse thrust.

It automatically does motor braking to bring the motor to a stop before reversing direction, so you just flip a switch.

Note: It doesn't give you much thrust.
Is that because we are talking only 5A here or because EDF's are not very efficient in reverse?
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Old Jun 07, 2016, 05:32 AM
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Maybe that's why cars have brakes! -- Can't see were throwing it in reverse would be beneficial -- or cheap!

Open you wallet, let the moths out, and buy some electric brakes ..
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Old Jun 07, 2016, 05:57 AM
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Quote:
Originally Posted by rcgroupie View Post
Is that because we are talking only 5A here or because EDF's are not very efficient in reverse?
I have flown and used the thrust reversing ESC in the J10 and it works well, later it was used in a Meteor. It will also let you taxi backward, watch the video of rcinformer I posted earlier - https://www.youtube.com/watch?time_c...&v=bM79Jd6ckMw
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