RE: CD ScaleDesigns Sopwith Snipe build

RE: CD ScaleDesigns Sopwith Snipe build
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RE: CD ScaleDesigns Sopwith Snipe build - 5/13/2008 12:31:26 PM

Michaelj2k

Posts: 312
Joined: 9/15/2006
From: Newark, DE, USA
Status: offline

quote:

ORIGINAL: Teus

Don,

You know how sharp cocodile teeth are?

This could seriously damage your wire.

Slip on a couple of pieces of fuel tubing over the jaws.

_____________________________

"He''s crazy Lew, he builds toy airplanes."
Waco Brotherhood #6

(in reply to Teus)

Post #: 1451

RE: CD ScaleDesigns Sopwith Snipe build - 5/13/2008 7:21:28 PM

abufletcher

Posts: 5183
Joined: 2/13/2004
From: Zentsuji, JAPAN
Status: offline

The mechanical part of the aileron servo installation is now done. Next comes the cosmetic part, which shouldn't be a problem since the hatch is located within the roundel.

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Post #: 1452

RE: CD ScaleDesigns Sopwith Snipe build - 5/13/2008 8:22:44 PM

phantom_najd

Posts: 55
Joined: 7/17/2005
From: Riyadh, SAUDI ARABIA
Status: online

Hi Abu,

Nice job congradulations, though, sorry you had to tear into the beautiful covering and paint job. Do you use 4-40 pushrods for the ailerons or it is the picture cheating

?

Azzam

(in reply to abufletcher)

Post #: 1453

RE: CD ScaleDesigns Sopwith Snipe build - 5/14/2008 1:23:46 PM

abufletcher

Posts: 5183
Joined: 2/13/2004
From: Zentsuji, JAPAN
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quote:

ORIGINAL: phantom_najd
Do you use 4-40 pushrods for the ailerons or it is the picture cheating ?

2-56 rods. But I notice there's still some slop in the system. I'm not sure what's causing this. At the moment I'm just using z-bends on the ends of the 2-56 rods but it's a good fit in the servo arm so I don't think that's it. Still I can replace that will a clevis on both ends of a 2-56 threaded rod. But, actually the arm itself seems to move a little, which I can't quite understand.

(in reply to phantom_najd)

Post #: 1454

RE: CD ScaleDesigns Sopwith Snipe build - 5/14/2008 1:49:30 PM

smcouch77

Posts: 655
Joined: 10/31/2006
From: Indianapolis, IN, USA
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Hi Don. Are you saying that there is play in the servo arm? If that's the case I wouldn't use it. I have some pretty old servos, but none of them has any play at the arm. I'm a firm believer in not taking chances with questionable equipment.
Steve

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Post #: 1455

RE: CD ScaleDesigns Sopwith Snipe build - 5/14/2008 2:53:14 PM

abufletcher

Posts: 5183
Joined: 2/13/2004
From: Zentsuji, JAPAN
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quote:

ORIGINAL: smcouch77

Hi Don. Are you saying that there is play in the servo arm? If that's the case I wouldn't use it. I have some pretty old servos, but none of them has any play at the arm. I'm a firm believer in not taking chances with questionable equipment.
Steve

Maybe I'm just being unrealistic here. I was looking at the Cub and here's the same 1/8" or so of "play" on all the surfaces. It's not floppy sloppy but it's also not rock solid. Actually, there's also about the same amount of play on the Snipe's rudder and elevator. I've replaced the 2/56 rod and z-end with a threaded rod with clevises on both ends, nuts behind the clevises, and small holes in the servo arms.

With the geometry the way it is, it only takes about 1/8" of travel on the servo arm to provide a full 1/2" of deflection (more than enough with four ailerons). So even miniscule amounts of play in the linkage are getting translated into 1/16-1/8" of movement on the aileron. There may even be some fractional flexing of the servo arm.

The Cub flies just great with at least as much "play."

(in reply to smcouch77)

Post #: 1456

RE: CD ScaleDesigns Sopwith Snipe build - 5/14/2008 3:04:54 PM

TFF

Posts: 742
Joined: 10/30/2006
From: Memphis, TN, USA
Status: offline

With Z bends, the rod, where it runs through the servo arm, shifts back and forth. As it is used, the bends rub the arm, and work the hole bigger making more slop. Now I cant say I dont use them, but I always regret it when I do. Because you have the access I would change it, but it will be ok as long as it is not too bad.

(in reply to abufletcher)

Post #: 1457

RE: CD ScaleDesigns Sopwith Snipe build - 5/14/2008 3:28:42 PM

abufletcher

Posts: 5183
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From: Zentsuji, JAPAN
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I've already replaced the z-bend rods with fully threaded 2-56 rod with (metal) clevises (with nuts to lock them down) on both end (in the smallest possible holes) and there is still movement. I don't think there's anything else I can do.

< Message edited by abufletcher -- 5/14/2008 3:47:18 PM >

(in reply to TFF)

Post #: 1458

RE: CD ScaleDesigns Sopwith Snipe build - 5/14/2008 4:57:23 PM

phantom_najd

Posts: 55
Joined: 7/17/2005
From: Riyadh, SAUDI ARABIA
Status: online

quote:

ORIGINAL: abufletcher

quote:

ORIGINAL: smcouch77

Hi Don. Are you saying that there is play in the servo arm? If that's the case I wouldn't use it. I have some pretty old servos, but none of them has any play at the arm. I'm a firm believer in not taking chances with questionable equipment.
Steve

Maybe I'm just being unrealistic here. I was looking at the Cub and here's the same 1/8" or so of "play" on all the surfaces. It's not floppy sloppy but it's also not rock solid. Actually, there's also about the same amount of play on the Snipe's rudder and elevator. I've replaced the 2/56 rod and z-end with a threaded rod with clevises on both ends, nuts behind the clevises, and small holes in the servo arms.

With the geometry the way it is, it only takes about 1/8" of travel on the servo arm to provide a full 1/2" of deflection (more than enough with four ailerons). So even miniscule amounts of play in the linkage are getting translated into 1/16-1/8" of movement on the aileron. There may even be some fractional flexing of the servo arm.

The Cub flies just great with at least as much "play."

Instead of using threaded rod which is so weak by nature, use the same push rod and http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXR765&P=ML with http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXR768&P=V to make your own threads keeping in mind that you must lubricate the rod and threading one turn then backing up half turn to remove the metal.

What I know is that the servos have some degree of play because of their internal gears mechanism backlash. Maybe I am wrong! For that what I do when I need to minimize the play is to make sure to use plastic clevises on both sides (servo side and control surface side) or use metal clevises with nut retainer. Further, and given that I don't mind losing some servo torque and control surface travel, I try to keep the push rod as close as possible to the servo and as far as possible to the control surface by doing this you will lose the mechanical advantage (torque) and travel but the control surface will not be moving (noticeably) when the servo horn play a little.

For the Snipe a little play won't be a problem since it's a slow flyer.

This is the way I do it and it's been okay with me so far. If you guys think that I am wrong please correct me.

< Message edited by phantom_najd -- 5/14/2008 4:59:31 PM >

(in reply to abufletcher)

Post #: 1459

RE: CD ScaleDesigns Sopwith Snipe build - 5/15/2008 12:40:52 AM

abufletcher

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From: Zentsuji, JAPAN
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quote:

ORIGINAL: phantom_najd
What I know is that the servos have some degree of play because of their internal gears mechanism backlash.

I think that's what I'm seeing here. It's really REALLY miniscule but that's getting magnified by the servo arm and then translated into even more movement at the aileron. But I suspect that this doesn't make any difference on a WWI model.

(in reply to phantom_najd)

Post #: 1460

RE: CD ScaleDesigns Sopwith Snipe build - 5/15/2008 2:34:41 PM

abufletcher

Posts: 5183
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From: Zentsuji, JAPAN
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Got the access plates covered and painted, so this is basically it for the servo installation. It's not the most perfect job ever but it'll do.

After I do the rigging, I'll make the connections to the top ailerons and also add some cosmetic stuff like the wire on the aileron horn leading back to the aileron edges and the dummy cable on the top. One nice thing about putting the servos in the wings is that I don't have to deal with the top closed loop setup which of course I ALREADY spent days (and days) figuring out!

Sometime practical trumps scale.

The carb arrived and I've put it on the engine and hopefully with give it a test run on a stand tomorrow. Then on the weekend, if everything's going well, I'll move it to the Cub and get in a couple flights. Just as soon as I'm satisfied that it's "back to normal" after the crash, I'll pull it and install it on the Snipe. I'm not going to tempt fate (again).

I'm certainly getting close to being finished.

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Post #: 1461

RE: CD ScaleDesigns Sopwith Snipe build - 5/15/2008 3:06:55 PM

abufletcher

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From: Zentsuji, JAPAN
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And, no, it doesn't look quite that yellow in real life.

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Post #: 1462

RE: CD ScaleDesigns Sopwith Snipe build - 5/15/2008 8:25:50 PM

1bruno

Posts: 76
Joined: 6/3/2006
From: Brentwood, CA, USA
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I love this build. I just finished reading Winged Victory by V Yeates and after reading it ,I have an urge to build a snipe. I cant tell you why you will have to jsut read the book to find out

(in reply to abufletcher)