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Dynon AP photo

F

FrankK90989

Well Known Member
It arrived today:)
img2289rtb6.jpg

I will try to post more of the install, if I don't freeze. oat got close to a doughnut last night. its long handle time:(
 
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Rob, double check your connecting servo rod for binding. I can't tell from the picture, but the connecting rod should be straight and not angled. Try full deflection on the alerion and try twisting the connecting rod to make sure it is free. I have found 2 RV's with improperly installed roll servo connecting rods.
 
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Servos mounted 1 concern

I had no problems mounting the Dynon servos. But I need to figure out a fix for this bolt.(see photo) If it should ever loosen and back out it would jamb the elevator.:eek: Its to long to turn around-the end hits the brace. Maybe some safety wire? It won't be left the way it is! Next the wiring:eek:
img2319iy4.jpg


Wing servo install
img2312rsr3.jpg
 
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What kind of nut do you have on that bolt? A castle nut and a cotter pin on a properly torqued bolt should be plenty secure. Since it doesn't rotate, a nylock nut would also suffice here, but I always feel better with a castle nut in these places. Perhaps shimming the belcrank a hair one way or the other would help?

Another thing from the photo- it looks like the rod end bearing attached to the bolt in question has quite a bit of thread showing. The rod end should be screwed more than 1/2 way into the pushrod. It may be so, but it doesn't look that way in the picture.
 
You could rivet a finger of spring steel to the bell crank that presses on the top of the bolt and hold the bolt in place that way.
 
Is it any more critical...

FrankK90989 said:
I had no problems mounting the Dynon servos. But I need to figure out a fix for this bolt.(see photo) If it should ever loosen and back out it would jamb the elevator.:eek: Its to long to turn around-the end hits the brace. Maybe some safety wire? It won't be left the way it is! ......
Click to expand...

...than the other two bolts at each end of the bellcrank that attach the rod ends?

If they back out they may also jam the system, but if they don't jam it up, you will have a total loss of control....:(

I think you may be over-rating the criticallity of this one bolt.... they are all critical in the push rod bearings/bellcrank system.

Build carefully and inspect fully on a regular basis.
 
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Frank,

The long bolt that you have installed upsidedown and safety wired can fit in from the top.

I suggest you turn it around next time you are at the plane.

Here's a picture from my -9.
 
Two set backs today--Got to the hanger this morning -0.4F oat a balmy + 10F inside. So I set the soda I brought for my lunch break inside the plane so it wouldn't freeze. (elect heat on inside) Never drank it But I couldn't find it at the end of the day to enjoy on the ride home. I must of buttoned it up under the floor boards. AAhh only about 45 screws:eek:. I did check for tools but not for cans duh.

After finishing the wiring I found the twisted pair to the roll servo was shorted together?? Van's wire loom the whole way? I'll pull a new pair tomorrow.(easy) anxious to see what the problem is, used milspec tefzel wire.

az_gila said:
...than the other two bolts at each end of the bellcrank that attach the rod ends?

If they back out they may also jamb the system, but if they don't jam it up, you will have a total loss of control....:(

I think you may be over-rating the criticallity of this one bolt.... they are all critical in the push rod bearings/bellcrank system.

Build carefully and inspect fully on a regular basis.
Click to expand...

The Van design uses the bolt as a clevis pin, Dynon uses the bolt as a one sided push pull pin. After about a billion cycles (3XC flights;)) it may rock loose.

N941WR said:
Frank,

The long bolt that you have installed upsidedown and safety wired can fit in from the top.

I suggest you turn it around next time you are at the plane.

Here's a picture from my -9.
Click to expand...

Yes it is on my toodo list. On my first quick check the bolt seemed to long to fit between the skin?
 
It can only...

FrankK90989 said:
The Van design uses the bolt as a clevis pin, Dynon uses the bolt as a one sided push pull pin. After about a billion cycles (3XC flights;)) it may rock loose.
Click to expand...

...rock loose if it looses torque because the self-locking nut is unscrewing. There should be no rotational force on the bolt if it is correctly installed and tightened up against the ball of the rod end bearing and the metal parts.

The fact that is a one sided push pin does not make a big difference - as long as the forces involved don't bend the bolt...:)

Even if it rocked loose, it should not jam the control system up, and the effect on the AP effectiveness from a slight looseness would be pretty obivious.

No need to do anything special to this bolt over all of the other critical ones in the control system.

But, if you want to, this would be the easiest thing to do... a self-locking castle nut...

ms17825selflock.jpg


http://www.aircraftspruce.com/catalog/hapages/ms17825.php

gil A

-- I just helped to re-design a modified Wheeler Express control system, and almost all of the primary elevator control system consisted of one-sided push pull pins.... multiple bellcranks with short throws, poor bearings and lots of play - which led to elevator flutter...:( Vans system is a lot cleaner....:)
 
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Dynon AP First Test Flt.

Got everything finished up to my satisfaction and still had time for a short test flight (.7). Climbed up to 4000 msl and hit the switch (cws)-- It zigged and bobbed a bunch trying to get on track (alt + hdg) sensitivity set at 5 on both servos, changed them both to 10 track got better-- then both to 15, now Im getting very close. Heading east dialed in HIB off to the west on the gps (old garmin etrax hehe) pushed the nav button she circled to the left went right to the track line and and straight to Hib.:) Feeling the stick I think 15 might be a hair aggressive? I have lots of hours tuning PID control loops at my old place of work (USS) I wounder if just one control parameter is enough? Anyway Im anxious to fly some more and fine tune. First impression is very positive.:)
 
re:toggle switch

Frank:
Your set up looks identical to mine (RV10). The question is, what's the unmarked toggle switch to the right of the AP74?

Marshall Alexander
RV10 N781DM
panel/fuse
 
RV10Man said:
Frank:
Your set up looks identical to mine (RV10). The question is, what's the unmarked toggle switch to the right of the AP74?

Marshall Alexander
RV10 N781DM
panel/fuse
Click to expand...

Marshall.
It is the 'recommened' servo power switch. I ran a wire from a spare fuse position (5A) to a the switch then to a terminal strip under the floor----
The AP74 power is just hooked up to the avionics bus per Dynon plans but I duno if I like this? And the switch now has a label.;)
 
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re: thanks

Frank:
Thanks, I would have seen that in the instructions, if I had read them yet.:)
Actually, all I've done so far is to cut the hole in the panel.

Marshall
 
Dynon AP RV6

Updated the servo's Firmware yesterday.
First test flight today it works like charm.
I have pictures of the installation if anyone needs them.
Mounted the Roll servo under the Co-Pilot position.
 
Loose shear screw

After Jamie found his servo arm a little 'sloppy' I checked my roll servo and yup it moved about 4 degrees with the servo locked! So long story short. I removed the cotter and nut and found the shear screw starting to back out allowing some wiggle room. See photo. Cleaned it up, a tiny bit of red loctite and good to go. Retested, no movement:) Went for a test flight .9 readjusted the sensitivity from 15 to 5!

Now I have to a test with blue loctite on brass, the reason is I removed some brass screws and nuts on a different project a while ago and found a green kinda goo. loctite Never hardened?
img2377rzf2.jpg
 
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Frank,

Just to get a clarification before I go back in and check my servo arms again...

Before you tightened the shear screws, was the movement of the servo arm around the mounting bolt, or did the arm, bolt and castellated nut move together (slop in the whole servo or connection system)? Sounds like it might have been the former, and the tightening of the shear screw fixed it...true?

How much linear travel of the servo arm did that 4 degrees represent (for instance, 1/2 inch back and forth at the servo arm to rod bolt)?

Did you re-torque the shear screw and/or castellated nut to any specific values...just asking, so if I need to do this, I put 'em back together correctly!

Thanks much!

Cheers,
Bob
 
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rvmills said:
Frank,

Just to get a clarification before I go back in and check my servo arms again...

Before you tightened the shear screws, was the movement of the servo arm around the mounting bolt, or did the arm, bolt and castellated nut move together (slop in the whole servo or connection system)? Sounds like it might have been the former, and the tightening of the shear screw fixed it...true?

How much linear travel of the servo arm did that 4 degrees represent (for instance, 1/2 inch back and forth at the servo arm to rod bolt)?

Did you re-torque the shear screw and/or castellated nut to any specific values...just asking, so if I need to do this, I put 'em back together correctly!

Thanks much!

Cheers,
Bob
Click to expand...

Bob,
I used a silver sharpie to mark a line across the "shear screw thick washer" and the servo arm. The arm would move about 2 deg. each way with the servo locked using the test setup. End of arm movement about 3/16"? I should of noted better. The castle nut was finger tight, so when I reinstalled I tightened just snug to the next cotter hole. The shear screw is a 6-32 brass capscrew 3/8' long. When it was loose it would rock back and forth, allowing movement.
When I do my pitch servo (lots of ele. movement) I will measure the arm hole vs shear screw. It did feel tight but not a friction fit. Just checking;)
Trying to be clear-- there is some small servo gear lash. And after I re-assembled, the shaft to arm movement went away:)
Hope this helps.
PS If anyone works on this you have to make sure the shear screw will break as designed. Not all glued up etc.
 
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FrankK90989 said:
Bob,
I used a silver sharpie to mark a line across the "shear screw thick washer" and the servo arm. The arm would move about 2 deg. each way with the servo locked using the test setup. End of arm movement about 3/16"? I should of noted better. The castle nut was finger tight, so when I reinstalled I tightened just snug to the next cotter hole. The shear screw is a 6-32 brass capscrew 3/8' long. When it was loose it would rock back and forth, allowing movement.
When I do my pitch servo (lots of ele. movement) I will measure the arm hole vs shear screw. It did feel tight but not a friction fit. Just checking;)
Trying to be clear-- there is some small servo gear lash. And after I re-assembled, the shaft to arm movement went away:)
Hope this helps.
PS If anyone works on this you have to make sure the shear screw will break as designed. Not all glued up etc.
Click to expand...

Thanks very much Frank...all makes sense. Will check for slop in the arm, and if it's there, check closely on the shear screws. Hey, on the comment on the shear screws being glued up, you mean that the head will break off and move with the servo arm to unstick a stuck control, right (ie, the head is not glued to its mounting hole and thus will not actually shear off)...am I reading that correctly?

Thanks again!!

Cheers,
Bob
 
Guys,

I can't speak for Dynon, but as someone with quite a bit of experience with AP's...I would not encourage you to dissasemble your servos. Perhaps the DynonSupport guys can jump in here (because this is actually a DynonSupport subject) and let customers know if they would like to see them being dissasembled and re-assembled in the field.

I'm not speaking for them, but I would really encourage you to call and speak with them before disassembling and re-assembling your own servos in the. If indeed a number of you are finding the arms loose or sloppy on the shaft, then perhaps Dynon should address it.

In the end I'm not speaking for them, just suggesting that the servos be serviced by the mfgr, not the builder. I think in the long term that is better for everyone.

My 2 cents as usual.

Cheers,
Stein
 
loctite

Searching the web I have found that blue loctite#242 might not set up on some metals/treatments such as anodized aluminum. The threaded hole looks to be anodized.
A snip--
Q: How long does it take for an anaerobic adhesive to dry?
A: Anaerobic adhesives do not contain solvents, which must dry. For an anaerobic adhesive to cure, it must be in contact with active metal ions and contact with oxygen eliminated. Outside of a bonded joint, anaerobic materials will not completely cure.

Q: What are materials that are considered "active" and "inactive"?
A: The list is as follows:

ACTIVE
Iron, Plain Steel, Nickel, Copper, Manganese, Kovar, Commercial Aluminum (with copper content e.g. 6061), Brass, Monel, Bronze

INACTIVE
Plated Parts, Anodized Aluminum, Titanium, Stainless Steel, Galvanized Steel, Zinc, Pure Aluminum, Cadmium, Magnesium, Magnetite Steel, Iconel, Silver, Gold, Natural or Chemical Black Oxide
 
Testing testing

Results-6-32 brass screws threaded into 6061 aluminum 5/16 thick, testing both blue (242) & red (271)Loctite. neither held very well. And that's just what I found when I checked my pitch servo. When I removed the shear screw it looks that it had been locked with a red thread locker. (Was loose)
I think this is a process of the castel nut not being tight enough, looseining the shear screw.
I re loctited (271) the screw, snugged up the nut 1 slot. Went for a test flight 1.3. Sensitivity went from 15 to 8--came back a happy camper:):):) It was fun. I'll be keeping a eye on this but I think its good to go:cool:

addendum: tried good ol super glue (cyanoacrylate),test screws won't budge, locked! Don't know if it would work long term?
 
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