Magnus Build thread - TJIRC

[SC_Pilot]

Put in 6 hours today and got the horns, servo trays, and most of the linkage in. Tomorrow I’ll be gluing in the elevator, cutting out and installing the rudder servo tray, and finishing things up. Looks like I may have most of it done by Monday. ?

I managed to get enough travel out of all the surfaces that it should be no problem meeting the spec throws. I can get the ailerons to match full down flap deflection... whether the servo will allow that much travel I’m not sure. But it’s nice to know I’m not limited in any way. I was worried how I’d make the slot and horn geometry work and I think it came out real nice for never having built a moldy before. Cutting just makes me nervous ? especially when that Dremel starts to walk on ya ?

 

[SC_Pilot]

Should be done by tomorrow! I’m really happy with the way the build is going. ? Only problem I’m running into is I think the X08 servos seem to be a bit too tall for the fuse. It looks like the servo arm height puts the elevator pushrod right into the wingspar. It looks like they’ll interfere but I’ll have to double check once my pushrod dries. The height of the tray is as low as it can go as the servo is already touching the bottom of the fuse.

Also looks like I’ll need to sand both aileron wipers to get the aileron travel I‘d like to see. Appears to be bottoming out on the top skin at full deflection. Who knows, maybe what little I sand will be enough to get that famous Comp ARF whistle that I love. ? Whistling is probably an indication or inefficiency but damn it sounds cool in a roll!

 

[Konrad]

Both of these builds are looking good. I particularly like learning that it takes you guys many many hours to fit the servos into the wings. That is to say I'm happy to learn I'm not the only one!

As to the wing spar and push rod clearance you are using the X08 and not the X08+? I often find this to be a problem with these small glider fuselages. I often will use a Z bend on the servo side of the push rod to help drop the push rod 2mm or 3mm.

All the best,
Konrad

 

[Konrad]

SC,
I having not flown one of these, but I think you only want/need about 1/3 the downward motion in the ailerons. The set up chart given by Jonathan Wells (post #42) is only showing 3mm of downward movement.

All the best,
Konrad

 

[Konrad]

Jonathan Wells, I just read this thread in detail and like at least two things that I see you doing. Using the threaded push rod directly into the servo arm. Can you please give us some details on how you accomplished this? I find that when I bend the threaded portion of the push rod I often get a fracture starting from the minor diameter of the threads. The sharp V of the thread is the source of the stress riser.
(I assume you cut the threads after you make the 90° bend).

I also like where you are sliding the wing servos further into the thicker parts of the wing (airfoil). Has this been a problem with servicing the servo? I assume you remove any epoxy fillet at the rear (TE side) when glueing down the servos. This would be to aid in slipping a replacement servo in place should the need a rise.

I'm a bit confused, is the stab to be glued or are there hard points to allow the stab to be bolted to the fuelage?

All the best,
Konrad

 

[SC_Pilot]

Both of these builds are looking good. I particularly like learning that it take you guys many many hours to fit the servos into the wings. That is to say I'm happy to learn I'm not the only one!

As to the wing spar and push rod clearance you are using the X08 and not the X08+? I often find this to be a problem with these small glider fuselages. I often will use a Z bend on the servo side of the push rod to help drop the puch rod 2mm or 3mm.

All the best,
Konrad

I’m using the X08+ servos. I can squeeze out another mm or 2 by using the low profile horn and a thinnner clevis. But it does rub on the servo case and I did get it to lock up once. So I figured I’d take rubbing on the spar vs possibly locking up on the servo case. But I just checked and it doesn’t interfere with the spar too bad.

SC,
I having not flown one of these, but I think you only want/need about 1/3 the downward motion in the ailerons. The set up chart given by Jonathan Wells (post #42) is only showing 3mm of downward movement.

All the best,
Konrad

The ailerons are bottom hinged so it binds going upwards.

It has what looks to be carbon tube hard points in the elevator. There’s no threaded insert. I glued mine just cause I thought it’d be stronger. I did try to run the screws in after glueing but one slipped off the Allen driver and fell down into the rudder cavity... Bad part was the epoxy from the elevator was still tacky so the screw was tacky as well. This was followed by banging the tail around like a hammer and cussing profusely for 5 minutes. Once the sucker finally came out... I abandoned trying to put them in. ?

I think @Diceman was going to glue his in as well but not sure what approach he will be taking.

 

[SC_Pilot]

No deflection change in elevator before or after inserting spar. So all it well ??

First photo = before.

 

[Konrad]

Yikes, to my eye that’s a lot of drag. I’d be concerned with double centering. As much as I hate to use kinks in push rods for fear of added flex at full load. I’d think about using a slight kink to remove the interference drag around center.

I'm adding an annotated photo of what I think might gain one 1.5mm to 2mm. with a Z bend at the servo end. I'm liking Jonathan's idea of a threaded pin (vertical part) of a push rod.

I’m curious as to what servo was used when 3D modeling in CAD. I thought that maybe the inverted motor of the MKS 6100 might allow one to sink the servo tray deeper into the fuselage. This doesn’t look to be the true. I did find that the MKS servo deck is 1mm lower (5mm vs 6mm) than the KST X08 but the motor tower might complicate things.

 

[Jonathan Wells]

@Konrad - I heat up and bend the rod first and then thread it otherwise thread portion can break, as you say.

 

[Jonathan Wells]

Designed to bolted but can be glued

I'm a bit confused, is the stab to be glued or are there hard points to allow the stab to be bolted to the fuelage?

 

[Konrad]

I see Jonathan is using BMS 105 servo. As of late I've been having very good luck with the Blue Bird brand of servo particularly the digitals.

Do you re-harden the push rod? Looking at your push rods I assume you thread the end before bending. So you are threading after bending?

Jonathan, Thanks

 

[Jonathan Wells]

Post #73 - I heat up and bend the rod first and then thread it, otherwise thread portion can break as you say.

I see Jonathan is using BMS 105 servo. As of late I've been having very good luck with the Blue Bird brand of servo particularly the digitals.

Do you re-harden the push rod? Looking at your push rods I assume you thread the end before bending.

Jonathan, Thanks

 

[SC_Pilot]

All finished! I posted my in-depth build thread over on RC Groups. Can‘t wait to fly it!

***New Build - TJIRC Magnus 60*** - RC Groups

Build Log ***New Build - TJIRC Magnus 60*** Slope Soaring

www.rcgroups.com

 

[SC_Pilot]

@Konrad What do you use to edit those pictures? I’m always mesmerized how professional they look. I checked the double centering issue and it seems to be non- existent. That photo may be at a slight angle as I was trying to enhance what the issue looks like since everything was black in the fuselage.

I did they the lower profile horns that KST gives you And a thinner clevis, but it was too tight. I noticed that 3 different servo arms I made of the “low profile” version, all seemed to give differing results on binding. Either I wasn’t seating the arms on the splines all the way or KST has some variances in tolerance on their arms. I would have liked to use metal arms on this build but couldn’t find any... and given how much trimming I had to do for the wing servo arms, probably better they were plastic.

 

[Konrad]

Thank you.

I use "preview" which is part of the Mac OS for the simple stuff. For the next level of stuff I use an antiquated program called Canvas. I don't have any modern stuff as I actually hate computers. I'd rather spend my money on toy airplanes.

As to the arms I think KST uses a 23 spline output shaft. This means that there is an offset when rotating the arms 180°. This can be an added feature if one knows about it. Or it can be very frustrating if one doesn't and is trying to match arm offsets between two servos (like with dual flaps, aileron, or V tail).

As to seating the arms you need to use the hold down screw to ensure they are seated. And yes there a various configuration of arms so you need to look closely when grabbing an arm to use.

I'm not here to tell you how to do things. I just point out what I think might be an issue. In all likelihood it should work fine. but if it doesn't now you and I have an idea as to what might cause any double centering if it rears its ugly head.

Too bad about posting on RCGoof.

All the best,
Konrad

 

[SC_Pilot]

Thank you.

I use "preview" which is part of the Mac OS for the simple stuff. For the next level of stuff I use an antiquated program called Canvas. I don't have any modern stuff as I actually hate computers. I'd rather spend my money on toy airplanes.

As to the arms I think KST uses a 23 spline output shaft. This means that there is an offset when rotating the arms 180°. This can be an added feature if one knows about it. Or it can be very frustrating if one doesn't and is trying to match arm offsets between two servos (like with dual flaps, aileron, or V tail).

As to seating the arms you need to use the hold down screw to ensure they are seated. And yes there a various configuration of arms so you need to look closely when grabbing an arm to use.

I'm not here to tell you how to do things. I just point out what I think might be an issue. In all likelihood it should work fine. but if it doesn't now you and I have an idea as to what might cause any double centering if it rears its ugly head.

Too bad about posting on RCGoof.

All the best,
Konrad

I ran into the spline offset problem with my flaps. I messed with both of them for two hours like a dog chasing it’s tail and gave up under the belief that I was one spline off or something to do with the servos being mirrored of each other. That or my horns were slightly different heights causing a geometry issue that resulted in one with a few more mm of deflection than the other. I’d be interested in hearing your solution. Is there a post or thread about it somewhere?

I was going to post a duplicate thread on here as well, but didnt want to detract from Jonathan’s original thread. I can try to post the whole thing in this thread in one fell swoop if that would be better?... if you can even post that much in a reply ?

 

[SC_Pilot]

What a dodo head I am... Heres the link to download a PDF of my build process and photos. Short and sweet... ?

TJIRC Magnus 60 - Google Drive

drive.google.com

 

[Konrad]

There should be an arm that allows the arms to be 90° to the body at center pulse. When you find this and the 90° possition it just a matter of cutting off the side you don't need. (Now don't swap the arms as you can't with a 23 spline output shaft swap the arms 180°)!

I think I may have some photos about this in some of my builds. I think Mo (Motowncali) has some comments on this as well. Then there is the trim offset in the radio and or curves in OpenTx templets like Mike Shellim on rcsoar.com. Do try to get the geometry correct. It makes a huge improvement in how the aircraft responds!

All the best,
Konrad

 

[Konrad]

What a dodo head I am... Heres the link to download a PDF of my build process and photos. Short and sweet... ?

TJIRC Magnus 60 - Google Drive

drive.google.com

Not working for me. Does one need to join Google?

Maybe I was too fast on the draw, it's working now.

All the best,
Konrad

 

[SC_Pilot]

There should be an arm that allows the arms to be 90° to the body at center pulse. When you find this and the 90° possition it just a matter of cutting off the side you don't need. (Now don't swap the arms as you can't with a 23 spline output shaft swap the arms 180°)!

I think I may have some photos about this in some of my builds. I think Mo (Motowncali) has some comments on this as well. Then there is the trim offset in the radio and or curves in OpenTx templets like Mike Shellim on rcsoar.com. Do try to get the geometry correct. It makes a huge improvement in how the aircraft responds!

All the best,
Konrad

Thanks ? I managed to get it closer. What little variance is left, I can fix in my radio.