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Old Jun 16, 2014, 12:52 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,731 Posts
Oscar nomination anyone?

Shoey - metal is great to work with but does need a few extra tools and skills....

Now for my next exciting block-buster movie - a very early proof-of-concept trial for the retracts mechanism. It works perfectly but a few little improvements are needed to avoid any landing shocks getting back to the servo. But the idea works

HS75bb servo connected via a torque tube configured as a semi-flexible universal coupling. My main concern is accessibility and the last remaining issue is how to mount the servo so it can be removable (heaven forbid!) Maybe an aluminium bracket of some sort.....cogitating.

Pat

Model Avro Anson retract test (0 min 47 sec)
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Old Jun 16, 2014, 04:10 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,731 Posts
...a small update

I was concerned the servo screws were almost impossible to access where I had the servo so it was mounted behind a new ply sub rib and screwed from behind - accessible through holes to be cut in the root rib. Now I'll make a decent ply subrib and repeat the process on the other wing - and I'm happier
I also realised with a duh! moment, I'll need a servo reverser on the other side. Having one wheel up and one down doesn't seem very useful
Pat
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Old Jun 16, 2014, 06:18 AM
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Liverpool, England
Joined Jan 2005
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Gets an Oscar from me Pat, smooth as silk really nicely thought through

If you have to get hold of a reverser why not get one of these - http://www.hobbyking.co.uk/hobbyking...Regulator.html that way if you are using proportional servos you could slow the travel down to get even more realism as well as reversing one channel

I have used these on a few planes with absolutely no issues

Enjoying this build, Ken
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Old Jun 16, 2014, 06:57 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,498 Posts
Now ain't that strange? I have never, ever thought of mounting a servo with screws going up from underneath the tabs......
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Old Jun 16, 2014, 07:03 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,731 Posts
Thanks gents - Ken - the HS75 retract servos aren't proportional - they just run end to end. Has the advantage here that if there is any resistance at the end-points, they can't stall. BUT it means the mechanics have to be setup proper
I've ordered some straight reversers from HK Australia - a whole couple of dollars each!
Tomorrow I'll get the other wing done then I can move on. At last!
Pat
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Old Jun 16, 2014, 08:02 AM
Parkcityflier
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Park City, UT, USA
Joined Aug 2001
1,530 Posts
I'm blown away with what you have done, Pat. Your engineering skills are equal to your building talents. Very nicely done.

Jim
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Old Jun 16, 2014, 09:03 AM
The Hun in the Sun
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Canada, BC, Comox
Joined Nov 2003
7,314 Posts
Very nice, Pat! Many standard analog servos are quite easy to reverse without the need for a reverser. Open up the case and swap the wires to the motor and to the potentiometer. I had to do it for one of my HS-225's that I'm using for my gear doors.
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Old Jun 17, 2014, 12:36 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,731 Posts
A complete reversal...

After some prompting from wise Frank, I took the back off the second HS75BB and reversed the wires on the potentiometer (right) and the motor(left) - you can see the swapped wire's colours have changed. Sure enough, the servo now works in reverse with no ill effects.
I know this process has been described dozens of times here on rcg, Youtube etc but I put it here to remind me it was done!

The blue masking tape was to hold the two parts of the case together not relishing a benchtop covered in small metal and nylon gears.......

Pat
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Old Jun 17, 2014, 03:25 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
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...almost there...

The second servo was reversed, installed and connected and now I have two legs working together. A bit of tidying up and I'll have to think of where to next

Pat
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Old Jun 17, 2014, 09:46 AM
Power Upward
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United States, OR, Albany
Joined Jun 2007
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Pat, awesome work as usual. Obviously more room to work with on a bigger model.

My Annie is calling my name... If I could just get my niece to take her CAT back I could get this out into the open again...

George
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Old Jun 17, 2014, 11:34 AM
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Moab, Utah, USA
Joined Apr 2003
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Excellent work, Pat. Definitely beyond my skill level. However, you have the photos in post #159 mislabeled, down should be up and up should be down. Don't you people in the southern hemisphere know up from down? Maybe it would be better to use the terms extended and retracted instead.

Larry
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Old Jun 17, 2014, 12:15 PM
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United States, NY, Dobbs Ferry
Joined Oct 2008
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Quote:
Originally Posted by Lnagel View Post
Excellent work, Pat. Definitely beyond my skill level. However, you have the photos in post #159 mislabeled, down should be up and up should be down. Don't you people in the southern hemisphere know up from down? Maybe it would be better to use the terms extended and retracted instead.

Larry
Now that's FUNNY! :-)

Stephen
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Old Jun 17, 2014, 12:22 PM
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United States, CA, Emeryville
Joined May 2007
176 Posts
Larry strikes again.
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Old Jun 17, 2014, 12:27 PM
Parkcityflier
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Park City, UT, USA
Joined Aug 2001
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Now that brings up a question. If you are flying inverted, is "up" towards your feet or towards your head and is"down" towards your head or towards your feet? If it's the former in both cases then Pat's description looks OK since the wing is inverted. Of course, in Australia, the earth's pole is to the south where our's in to the north. Oh well, maybe using "retracted" and "extended" is better.
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Old Jun 17, 2014, 03:26 PM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,731 Posts
You northerners - always think you're right 'cos there's more of you I future I'll label my U/C directions as 35 deg south (extended,down) or 35 deg North (retracted, up). Ah what the hell - you know what I mean.........

WRT what is next, I want to build a wing alignment jig as the top sheeting must soon be applied. I must also remove the U/C legs to paint the wheel wells and upper legs....and think about where to route power wiring, flap servos, lighting wires, add some shear webbing,......I wont get bored This sort of 'plan build' is really testing - even with the 'benefit' of laser-cut parts but I love the problem-solving, plan interpretation and freedom of changing stuff as I see fit.

One of my over-arching concerns has been concerned with CG or balance. I also would like a small reserve of power so have upped the motors one size and have a pair of Turnigy G46s - a bit bigger than the Power 32 I was going to fit. This, along with batteries in the nacelles, should help get it right. The balance point is just behind the front spar so all my retract stuff is forward of CG - that is good! Getting the required batteries in the nacelles is more problematic. I may parallel some physically smaller LIPOs to get them to fit vertically accessible from the hatch on top of each nacelle.

Enough rambling....back soon - Pat
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Last edited by Pat Lynch; Jun 17, 2014 at 05:01 PM.
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