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Old Oct 22, 2007, 03:46 PM
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Vectored Thrust for Multiplex Funjet

I recently picked up a Multiplex Funjet and I'm consisering playing around with a vectored thrust system (for the first time).

I haven't even opened the box yet, but I have come up with a conceptual sketch of a two-axis vectored thrust system, using a swash plate from my T-Rex as an inspiration. It features two servos attached by ball links to pivot the motor assembly on a central ball joint, so that the thrust is actually transmitted to the airframe near the centerline of the system

At first, I was thinking of an inrunner like an E-Flite Six series or a Mega, but this system would be better suited for a high kV outrunner such as the LSPJ or the MicroDAN 2505. An inrunner could still be used if bolts and spacers are used to attach the inrunner using a firewall adaptor (third sketch)

Please realize that the attached sketches are conceptual in nature, but feedback/comments/suggestions are wanted.

**** UPDATE ****

See post 7 for what I actually built... it's different from the sketches!
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Old Oct 23, 2007, 11:14 AM
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I'm building two prototype vectoring systems. The first one will be very similar to the sketch I've provided above, and I will be using a heavy-duty DuBro 4-40 ball link as the central pivot and thrust transfer point. I'll recess the plastic cup of the ball in an indentation to fully support the plastic from the outside, and have the metal ball in a wood or plastic motor mount.

The second one will be based on an MX400 helicopter swash plate (when I upgaded my heli to e-CCPM, the old swash plate bacame "surplus", so I'm donating it's body to science ) This system will likely have a lot less travel (I estimate 25 degrees from the central axis, or 50 degrees of total sweep) but the geometry of the central pivot and ball joints for the push rods is already there.

I really like the idea of transferring thrust through the pivot, as another system that has been done for the Funjet had the thrust being transferred through the pushrods and servos (Details here). This puts a lot of stress on the servos, IMO. That's why I want the central pivot.
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Old Oct 23, 2007, 02:40 PM
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Very nice project indeed ...
Looks prommising, keep it up and post some videos of the performance when it's finished ;-)

One quetion tough, will the center ball joint not interfere with the air flow generated by the ducted fan? Giving you less performance in the end?
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Old Oct 23, 2007, 04:54 PM
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Quote:
Originally Posted by bedeone
Very nice project indeed ...
Looks prommising, keep it up and post some videos of the performance when it's finished ;-)

One quetion tough, will the center ball joint not interfere with the air flow generated by the ducted fan? Giving you less performance in the end?
The funjet is a pusher, not an EDF, and any disturbance to the airflow will be ilmmediately in front of the motor. I could "steamline" things, I suppose.
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Old Oct 24, 2007, 04:12 PM
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Interesting! I have been looking at VT design for a while and have gathered some links that might be of intrest.

http://www.rcgroups.com/forums/showp...2&postcount=42
http://www.rcgroups.com/forums/showp...2&postcount=43
http://www.rcgroups.com/forums/showt...8&highlight=VT

/Kalle
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Old Oct 25, 2007, 12:44 AM
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Kalle,

Good links!
My approach is quite different, since I'm using a heli swash plate as my inspiration. My surplus swash plate is actually being used in both of my prototype systems. The inner part of the swash is in one, and the outer is goung in the other. Originally, I was just planning to use the inner portion of the swash plate since the ball joint (with the hole for the heli main shaft) is alreasu geometrically aligned with the ball joiunts, so all rotation will be in line with the centerline of the motor. But I found that the outer portion of he swash (also with 4 ball joint connection points for the servos to control direction) is almost perfectly aligned with a DuBro 4-40 HD ball joint as the pivot. So, in reality, my sacrificed swash is yielding the basis of two high-potential systems. Both will have thrust transferred through the pivot/ball directly behind the motor, as in my conceptual sketch.

I'm going to get about 50 degrees of sweep from the inner swash (prototype 1) and 90 degrees from the outer swash (prototype 2) Both are essentially faithful to the concept sketch.

An anti-rotation slot will be used to keep things aligned, but I might experiment with a slotted disk that relies on the control rods to the servos, as has been done elsewhere. I'm just worried about slop.

Pics will follow once I'm farther along. I want to shrink things to fit the mount partially inside the airframe for the funjet, meaning inside a tube about 1 5/8" in diameter. This is to have the motor as close as possible to the stock location without VT to simplify CG problems. Of course, it will be located slightly aft to allow room for the motor to rotate.
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Old Feb 18, 2008, 05:31 PM
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Nearing Completion!

After a winter of too many projects, I'm nearing completion on my vectored thrust funjet. I've attached some photos to show what I've done
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Old Feb 18, 2008, 05:52 PM
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YOu can see from the original post that I did not (could not) use an anti-torque pin in a similar arangement to that found in helis, as the geometry did not seem to work in the space I had to work with. I used the plastic guide for the lingages instead.

To control the VT system, I've got one HS-81 servo connected to the rudder channel, and one connected to the AUX channel of by AR6100 receiver. Using my DX7 radio, I've got it set to the mix/rudder dual rate switch. For rudder, I have adjusted the EPA on the rudder to zero in one position (essentially disabling rudder) and to 100% in the other position (giving me rudder vectoring). For elevator vectoring, I've set up an elevator to aux mix on the same switch.
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Old Feb 19, 2008, 02:38 PM
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Wow, very cool project! I have a simpler setup that I did, limited to only pitch-axis vectoring, which will be published in the next issue of RC Sport Flyer magaizne under the monthly "Hop-Up" column.

It's great to see the creativity that folks have to customize models and make them capable of nutty aerobatics. Even with pitch-axis only, I can do end-over-end tumbles and even flat spins, or turn off mixing and just cruise around as a normal Fun Jet. I'm sure yours with both axes and such a large range of movement will make for some really nutty flight capability!


Mike Hoffmeister
Cincy OH
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Old Feb 19, 2008, 06:48 PM
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Quote:
Originally Posted by Dynomike
Wow, very cool project! I have a simpler setup that I did, limited to only pitch-axis vectoring, which will be published in the next issue of RC Sport Flyer magaizne under the monthly "Hop-Up" column.

It's great to see the creativity that folks have to customize models and make them capable of nutty aerobatics. Even with pitch-axis only, I can do end-over-end tumbles and even flat spins, or turn off mixing and just cruise around as a normal Fun Jet. I'm sure yours with both axes and such a large range of movement will make for some really nutty flight capability!


Mike Hoffmeister
Cincy OH
Thanks Mike,

I'll be posting pics of the final version in a few days. It might be a while before I can maiden it since there's still a foot of snow on the ground...
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Old Feb 19, 2008, 09:40 PM
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I've posted a bench-test "teaser" video at:

http://www.rcgroups.com/forums/showp...38&postcount=5
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Old Feb 19, 2008, 10:52 PM
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Wow, that is some pretty serious range of motion in both axes! Should make for some interesting flying!

Mike
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Old Feb 20, 2008, 08:01 PM
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Build Log Thread Started

I started another thread and build log on this project. It can be found at

http://www.rcgroups.com/forums/showthread.php?t=821201
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Old Nov 27, 2015, 05:57 PM
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Dual Pusher Pitch Only Thrust vectoring and OpenTX on Taranis

I have a Taranis X9D and want to control 2 motors and 2 servos. Motors pitch Thrust Vector. 2S battery so i am trying to avoid Battery Eliminator Circuit?

I anticipate outputs:
Ch1 = ESC1 Throttle
Ch2 = ESC2 Throttle
Ch3 = Servo 1 Pitch
Ch4 = Servo 2 Pitch

Outputs need to be mixed so
Right stick up/down (common Throttle) provides a nominal motor speed throttle setting to outputs 1 (Left) and 2 (Right) equally

Right Stick (Yaw Differential Thrust Yaw- NO RUDDER) subtracts or adds to 1 and 2 when moved Left or Right with a pretty steep curve imposed to have lots of effect early (motors are outboard pretty far to give lots of lever arm.

Left Stick Up OR Down moves pitch servos together
Left Stick Left OR Right moves pitch servos together in opposite directions for a (barrel roll???
Left Stick Down and Left moves Left Servo Down, Right servo stays neutral???
Left Stick Up and Right does the opposite???


Do I want some thrust mixing here? Do i really want something diffent from the Left Stick listing above? I think it is right, but not really sure.

RDB
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