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Pusher Park Jets For all pusher jets and jet-like models.

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Old 05-01-2014, 08:54 AM   #1
solentlife
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Default Thrust vectoring with Pushers - ideas ?

OK .. I have TV on EDF .. it's ok .. its prone to create heart-attacks when first used ! .. but basically so far I'm not totally sold on it ..

BUT with a decent pusher set-up - I reckon it could really 'push the boat out' ...

Ideas of how to mount. I have a concern that high power as many pushers are could strain a servo .. or two.

In simple terms I've looked at single servo pitch vectoring. A ply mount plate with metal rod mounted across horizontal centre line pivoted at ends. A servo attached via rod to top or bottom of ply mount. Main thrust is taken by the rod axle ..

Any other ideas ?

One of the best uses I can think of .. some of us push the limits of models such as high power pushers .. and often we have trouble with thrust angles of the power unit. This could solve that by having a variable thrust angle that can be set via AUX channel to aid launch ... then reset to aid fast flight. We can play with it ON the flight line instead of on the bench adjusting shims etc.

mmmmm this is something I need to get into more ....

C'mon guys and gals ... thoughts ... please ...

Nigel

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Old 05-01-2014, 10:30 AM   #2
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I've never been convinced by the concept of thrust vectoring as a method for control. Sure, it works fine when you have power on, but what about when you have the throttle closed

I guess if you have it 'in addition' to normal control surfaces it should be safe enough but unless you want to do stuff like post stall flying/hovering/tumbling or such like I'm not sure it will give you anything that normal surfaces cant?

I did try timer adjusted thrust angle back when I was designing and flying rocket power freeflight models. It was good in concept but never really worked as intended in practice.

Personally adding a few shims seems like a much simpler, easier/quicker, lighter and more reliable solution if all you want to do is minor thrust angle 'tweaking' during trimming.
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Old 05-01-2014, 11:20 AM   #3
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I would never substitute TV for normal surfaces ... my Twister that has TV has it switched to link in with elevator and rudder - and can be switched off completely. Took ages to find way to make sure it centred when switched off ! That may sound a bit strange .... but think of it ...

You are flying and as usual the sticks are not stationary ... you switch of and the servos are at position related to the surfaces .. not centred. But when you switch of - you want TV to be neutral so that model flies normally ..

My thoughts on tweaking - yes I agree that shims are not hard ... but given that some of my pushers are nit your garden variety jobs - that have crazy power setups that make a hash of any slight nisaligned thrust .. it's nice to think that a click or so on Tx could alter it without need for spanner and shims. And its' alterable to a much more variable degree... up and down.
1.2KW stuck up behind a model that is designed for 150W is not childs play !!

For normal practice .. certainly it's unnecessary.

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Old 05-01-2014, 12:52 PM   #4
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I take your point Nigel but trimming doesnt have to be done by going straight to warp speed. You could fly on half power, make any course adjustment that is necassary, then prograssivly build up the power making any further minor tweaks as and when.

Yes it could take a few flights to get it nailed but compared to the hassle of adustable mounts I know which I'd prefer. I guess a compromise might be to make a mount that is adjustable by screws, that would mean adjustments would take seconds.
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Old 05-01-2014, 01:04 PM   #5
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Had a 3 vane rudder thrust vector setup in an Ottoo Dieffenbach F-15. Worked pretty good. http://www.rcgroups.com/forums/thumb...=threadgallery

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Old 05-01-2014, 01:54 PM   #6
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Originally Posted by JetPlaneFlyer View Post
I take your point Nigel but trimming doesnt have to be done by going straight to warp speed. You could fly on half power, make any course adjustment that is necassary, then prograssivly build up the power making any further minor tweaks as and when.

Yes it could take a few flights to get it nailed but compared to the hassle of adustable mounts I know which I'd prefer. I guess a compromise might be to make a mount that is adjustable by screws, that would mean adjustments would take seconds.
I wssn't planning on going deeper into the high power stuff but as an example ... the 1.2kw parkjet has a runtime of barely over a minute .. 2 mins if I'm careful. Agreed I can slow her right down to normal PKJ speed and maybe get 3mins ... but in reality there are only two areas of interest - that's launch and WAY HEY WHAT THE HELL WAS THAT !!

In a more normal set-up I agree ... you'd build up adjustments as necessary etc.

I think the pitch concept could be more interesting than the yaw aspect personally and given good control that can be switched on / off - put to good use.

Many of the Youtube videos that mention TV on the model do not really show any real benefit or antics as a result of it .. pity as it can really make a difference when set-up correctly.

Nigel

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Old 05-01-2014, 02:20 PM   #7
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I've tried this simple mount.
http://shop.flitetest.com/accessorie...thrust-vector/
It works very well but I've never used it on more than 400 watts.
You could also make your own with a simple ball joint and some thin ply mounted to a standard motor mount. Add two servos mixed to elevator and rudder and Bob's your uncle.
There's a bit of a ooh aah when you use TV but I prefer traditional controls.

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Old 05-01-2014, 03:17 PM   #8
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Originally Posted by Wrongway-Feldman View Post
I've tried this simple mount.
http://shop.flitetest.com/accessorie...thrust-vector/
It works very well but I've never used it on more than 400 watts.
You could also make your own with a simple ball joint and some thin ply mounted to a standard motor mount. Add two servos mixed to elevator and rudder and Bob's your uncle.
There's a bit of a ooh aah when you use TV but I prefer traditional controls.
Nice one - but that's really same as my own DIY description .. single axis with rod axle etc.

I thought about conversion of a TV nozzle from EDF ... but they do not take any motor torque / real thrust on the swivel mounts - they are just basically a tube that swivels.

There's the vanes as Hawk has shown .. and others I know of ... but that means extra details extending back from the model / prop.
I think I'd prefer to have motor mount move so I keep minimum outside airframe / prop ...

Nigel

222kph PKJ,EDF Concorde, Mini4,Mig3,T45,PKJ twin,ME109,Edge540,Cessna182,Skymaster Biplane,F15,F16,Badius,Ultimate,SE5,Qbee10,450 Heli,V911,J3 Cub Founder 9x forum: http://groups.yahoo.com/group/Flysky_RC_radio/
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Old 05-01-2014, 06:56 PM   #9
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Steve Shumate did a very simple and effective pitch TV system on his Su-37:

http://www.rcgroups.com/forums/showthread.php?t=666686

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Old 05-01-2014, 08:50 PM   #10
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Shumate knocks up some amazing machines ... his F15 I reduced to 75% and it's one of the most fun machines out ..

Nigel

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