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Old Jul 24, 2014, 08:03 PM
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Another 2014 Alex/Enigma

yet another of these threads,

I bought this plane 2 years ago,
only just got the time and motivation to work on it.

Prior to this I was flying a Wilco with kpg5.2/tacon/16x17/hk200 combo which suffered an elevator failure and was totaled.

Power to be 1509/1.5d/6.7 4s with a left over 14.5x14.5 rfm prop I am supposed to have.

Only have to flash software onto the HK Red Brick 200a and organize wiring in fuse to maiden hopefully Saturday.

couple booboos,
put elevator horn hole to far back and only got about 5mm throw, jb welded a piece sideon along with a couple metal pins through both, hope it don't fail.

Horns were cut by a friend with cnc, did not make the flap horn tall enough so got pushrod binding at hinge line, had to bend pushrod a little to clear, getting about 35-40degrees flaps, have to live with this.
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Old Jul 25, 2014, 12:16 AM
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Hi lennyk,

Quote:
Originally Posted by lennyk View Post
...hope it don't fail
I'd redo that elevator horn for safety's sake. If it does fail, someone could get hurt.

Quote:
Originally Posted by lennyk View Post
Horns were cut by a friend with cnc, did not make the flap horn tall enough so got pushrod binding at hinge line, had to bend pushrod a little to clear, getting about 35-40degrees flaps, have to live with this.
You need to cut away some more wing material at the hinge line to stop the linkage from binding. Bending the linkage will make it prone to bending more under load.

The horn looks too tall to get the required flap throws - the linkage hole needs to be closer to the hinge line.

Martin
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Old Jul 25, 2014, 06:21 AM
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will do
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Old Jul 25, 2014, 01:07 PM
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Martin made some good points.

Here's how I set up the flap horns on the Enigma. Good for 90 degrees of flap travel if you want it.

I've never run that motor on a prop that small. There might be a risk of over revving the motor and throwing a magnet.

Good luck on the maiden.

Lenny
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Old Jul 25, 2014, 01:31 PM
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Two major mistakes,

first, elevator servo wrong direction mounted. turn it around 180 degrees.
This will lead to a better optimized pushrod direction.

second, elevator linkage was almost ok at the beginning. after turnign the servo it should fit nice for the travel also.

Don`t fly the plane in any case as it is right now.
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Old Jul 25, 2014, 05:28 PM
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Quote:
Originally Posted by plastikmann View Post
Two major mistakes,

first, elevator servo wrong direction mounted. turn it around 180 degrees.
This will lead to a better optimized pushrod direction.

second, elevator linkage was almost ok at the beginning. after turnign the servo it should fit nice for the travel also.

Don`t fly the plane in any case as it is right now.

I have a different view on that.

I agree that turning the servo 180 degrees (so the output arm is near the trailing edge of the fin) would make the pushrod closer to being perpendicular to the elevator, but that's really not necessary.
I've built many Enigmas with geometry similar to this with no problem at all.

Having the servo arm toward the front puts it in the area of the fin with the most space and makes more sense.


Lenny
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Old Jul 25, 2014, 06:30 PM
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No problem on that, if its ok for you, do as you want.
Kinematics is a precise defined science for good solutions. If yours is sufficient to you its ok.
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Old Jul 25, 2014, 07:24 PM
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I actually considered both horn positions a while back,
in one case the pushrod is acting like traditional pivot type
and in other it is more or less poking/pulling.

gonna stay as is for now.

Lenny,

Are you cutting through the flap wiper and gluing the horn inside the space ?


Elevator horn had been dremelled out and replaced.

Gonna run the 16x17 rfm, just ran it up on test bench with the hk200/4s 3300
and all seemed well, no overheating etc.
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Old Jul 25, 2014, 07:58 PM
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Cg with a 4aaa rx pack just behind wing is around 65-68mm

I assume this is a safe nose heavy cg as many fly around 80mm.
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Old Jul 25, 2014, 10:50 PM
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Quote:
Originally Posted by lennyk View Post

Lenny,

Are you cutting through the flap wiper and gluing the horn inside the space ?

Yes. I make a horn that extends through the flap spar and back into the flap.

65-68mm will be very nose heavy. I'd suggest starting about 78mm instead.

Good luck,
Lenny
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Old Jul 26, 2014, 12:29 AM
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Hi lennyk,

Looks like its getting there

Just looking at your original photos. Is that tape that youve put around the servos before gluing in? Its not easy to see.

If so, there's a good chance that they will come loose at some point. Elevator servo looks particularly vulnerable - a quick twist and it may break away.

I always glue my servos in without tape and attach them to the top and bottom skins for maximum strength. Also stops the top skin flexing under load.

Cheers,

Martin
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Old Jul 26, 2014, 04:42 AM
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Yes, I thought masking tape was a "standard" practice by many ?
I tested it with a servo against a piece of wood and it held up fine but I will look into it in the near future.
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Old Jul 26, 2014, 12:32 PM
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My main concern is actually the wing connector you have chosen to use. Looks like a balance connector to me. Infortionately those connectors are not "self cleaning" and sometimes make for a rather poor connection.

I have trouble frequently with the balance connectors on my Lipo packs not making full contact and the charger then screaming at me that the pack is out of balance, or worse, the charger brings the pack back into what it thinks is in balance but due to the higher resistance in the connector and the voltage drop, the cell now actually gets over charged. Specially when I've had a speed controller catch fire, the balance plug on that pack is practically a write off as it gets covered in crap from the smoke and the connector does not clean when you plug it in and out a few times.

Another types of connectors that are similarly poor in design are the RS 232 type PC serial connectors and Futaba/JR female servo plugs.

The famous green 6 pin multiplex connectors and also the various deans connectors are self cleaning. Also the header strip that is the female version of what you find on your RX is fine. You can get it from the various electronics stores in a 1 or 2 wide strip that you cut to the length you want.

Be sure to check function before every flight if you keep this connector!!!

P.s. In my opinion normal masking tape on the servo actually works well. Specially with plenty of epoxy around it to form a pocket. The glue on the masking tape is better at gripping the plastic housing then epoxy ever will yet the epoxy grips the paper side of the making tape well. The glue of the masking tape also becomes more rigid over time and is not likely to start letting go. Unlike say electrical tape. It's a strange one for most people to believe but it works.
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Old Jul 26, 2014, 02:32 PM
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Quote:
Originally Posted by jjmouris View Post

P.s. In my opinion normal masking tape on the servo actually works well. Specially with plenty of epoxy around it to form a pocket. The glue on the masking tape is better at gripping the plastic housing then epoxy ever will yet the epoxy grips the paper side of the making tape well. The glue of the masking tape also becomes more rigid over time and is not likely to start letting go. Unlike say electrical tape. It's a strange one for most people to believe but it works.
Hi Joe,

Unfortunately, my experience has not been the same as yours, which is why I no longer masking tape wrap my servos. The joint may improve or deteriorate over time, which is an unknown factor.

I now put a thin layer of epoxy to the top skin and then brace it to the bottom skin for maximum support.

Lennyk, are you wishing that you'd never posted those photos?

Cheers,

Martin
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Old Jul 26, 2014, 06:03 PM
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not at all, good to hear the explanation of the opinions.

Had a few flights this afternoon.

Maiden went well today, elevator throws had to be reduced and about 30% down on the crow brakes. Turn nice and flies even better than the wilco I had before.

I have never flown crow brakes and neither anybody at my field, they were pretty impressed to see it slow down and self land even with the lowish flaps I have.

slightly puffed a 4s 3300 glacier battery on about 1min runtime.
I also used a parallel pair of 4s 2200 gensaces 25c and they fared much better, just barely warm.

I previously used this 16x17 prop on a kpg 5.2/tacon 3650 setup and it was a little less demanding than the 1509/1.5d
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