VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 02-28-2017, 10:14 PM
simatos simatos is offline
 
Join Date: Sep 2014
Location: vancouver canada
Posts: 83
Question Garmin GSA28 ROLL servo question

For RV 7: For the roll servo installed in the wing, I see the pushrod installed in the outermost position (third hole) in the install drawings, but here i see some have used the middle hole.

Garmin says middle hole for the RV8 roll servo.

So what is the consensus for the RV 7? Outer or middle position for the pushrod??

Thanks Gary
Reply With Quote
  #2  
Old 03-01-2017, 03:03 AM
tgmillso tgmillso is offline
 
Join Date: Nov 2012
Location: Launceston, Tasmania, Australia
Posts: 444
Default Middle position

I too ran into the same problem on my -7, so I called Garmin. They said that the middle hole was the ideal position, as it meant that more force could be applied by the servo on the pushrod than if using the outer hole. The downside is that you have to be more accurate at adjusting the pushrod length, otherwise it will but up against the servo stops at the extent of the aileron travel. Get your ailerons adjusted first to match your desired throw. Keep in mind that the neutral position of the stick is about 19 degrees of forward elevator (IIRC), as this seems to affect the aileron position through slight geometry changes to the large aileron pushrods. Then adjust the servo pushrod length so that at each of the aileron stops, the servo arm has equal clearance to the respective servo stops. This will mean that in the neutral stick position the servo arm will NOT be perpendicular to the servo body, just by a few degrees. The important thing is that at the extremes of the aileron throw, the clearance to each stop is the same. If the neutral stick position results in a perpendicular servo arm, the arm will contact one of the stops at the extent of travel when using the middle hole. This is why many people just use the outer hole. The total linear travel is the same, but the angular travel using the outer hole is less, meaning that the alignment with the servo stops is less critical, but at the cost of the servo being able to provide less force to the control surfaces.
On the topic of the servo stops, the instructions say to let half the stop ride up on the main servo mounting bracket. As an engineer, I can not stomach this half baked solution, so I have trimmed the bottom of the stop bracket flush with the servo mounting bracket, creating a left and a right stop. These now mount separately, but flush, with the face of the servo. I have performed load calculations for the mounting screws with the bracket in this separated fashion and they are more than adequate to handle the maximum torque of the servo. Your opinion (and obviously Garmin's) may differ on this point, so I would advise that you perform your own basic load calcs before proceeding accordingly.
I hope this helps.
Tom.
Reply With Quote
  #3  
Old 03-01-2017, 04:31 AM
g3xpert's Avatar
g3xpert g3xpert is offline
 
Join Date: Sep 2010
Location: Olathe, KS
Posts: 1,677
Post

Quote:
Originally Posted by simatos View Post
For RV 7: For the roll servo installed in the wing, I see the pushrod installed in the outermost position (third hole) in the install drawings, but here i see some have used the middle hole.

Garmin says middle hole for the RV8 roll servo.

So what is the consensus for the RV 7? Outer or middle position for the pushrod??

Thanks Gary
Hello Gary,

Pages 15-30 and 15-31 of the current Rev. AA G3X Installation Manual show using the middle hole on the roll servo arm for an RV-7/8/10, and this is what we recommend.

Thanks,
Steve
__________________
Garmin G3X Support
g3xpert@garmin.com
1-866-854-8433 - 7 to 7 Central Time M to F
Please email us for support instead of using Private Messaging due to the limitations of the latter.
Reply With Quote
  #4  
Old 03-01-2017, 09:40 PM
simatos simatos is offline
 
Join Date: Sep 2014
Location: vancouver canada
Posts: 83
Default

Steve, Thanks (twice)
Tom G'day M8 and also thanks
Installing the roll servo today with middle hole position for the pushrod. Couple of wrinkles. The pushrod at the servo used the big washer and this is what is striking the stops. I do expect the travel will be less once hooked up the push-pull tubes and the sticks but who knows, i guess i will live with it for now.

Tom I agree the canted placement of the stop bracket on to of the servo bracket is less than elegant..........i wonder if you made a shim for the servo bracket the same thickness of the stop bracket, if that would be a legal fix, if you see what i mean. So the servo moves back the thickness of the stop bracket, the stop bracket is now flush against the servo face and you get the full purchase of the screws. Just spitballing here, What do you think???????????

Also wires and strobe cable passing thru this area would need to be secured away from moving items agreed???

Gonna try to put it to bed tomorrow, wanna get that wing mounted before too long, thanks Gary
Reply With Quote
  #5  
Old 03-02-2017, 12:50 AM
tgmillso tgmillso is offline
 
Join Date: Nov 2012
Location: Launceston, Tasmania, Australia
Posts: 444
Default

Regarding the big washer, if you adjust your aileron stops first (I used the delrin rod stops and highly support this mod) then adjust your aileron pushrod lengths, by the time you get around to adjusting the servo pushrod, you will find that the washer will have adequate clearance to both servo stops. I set my aileron throw by sizing the delrin rod so that it was midway between Vans specified max and min.
Regarding a doubler for the servo stops, I too thought about going down this path, and even ordered longer screws (the stock ones are not long enough to use with a doubler). I began cutting the doubler, then I realized that every time I needed to remove the servo, I would have to take the stops off, which I could see becoming a PITA, not to mention the risk of destroying the tiny #4 screws that hold it on. Out came the dremel tool, and problem solved.
Tom.
Reply With Quote
  #6  
Old 03-02-2017, 04:25 AM
tgmillso tgmillso is offline
 
Join Date: Nov 2012
Location: Launceston, Tasmania, Australia
Posts: 444
Default

For securing the servo wire bundle, I just fabricated a right angle bracket out of a piece of 0.025" Alclad. On one side of the angle, I drilled two holes that match the hole pattern on the bellcrank mount, and on the other flange I drilled one hole in the center to which I will bolt an adel clamp to secure the wire bundle. Just be sure that you make the angle large enough so it allows clearance for a socket or other tools, as access installing this and the adel clamp will be awkward. Check your thread length for the bellcrank bolts, as you may need to use thinner washers or a longer bolt, and of course check everything through the full range of control motion to ensure no conflicts.
Tom.
Reply With Quote
  #7  
Old 03-02-2017, 10:11 PM
simatos simatos is offline
 
Join Date: Sep 2014
Location: vancouver canada
Posts: 83
Default

Tom, made your bracket with clamp and wires nicely out of the way. The Derlin stops I see folks are using about 3/4 inch diameter to get right throw, sound right? Is you machine flying yet? If so what do you think to the Garmin stuff?
Totally off topic, I got a real nice pay of boots from Tas
Thanks again G
Reply With Quote
  #8  
Old 03-02-2017, 10:54 PM
tgmillso tgmillso is offline
 
Join Date: Nov 2012
Location: Launceston, Tasmania, Australia
Posts: 444
Default

Glad the bracket worked.
I'm using 5/8" delrin rod and I get 29.8deg up and 16.0 deg down. The high limit is 32 deg up and 17 down, so I thought this worked OK. You may go to the 3/4". I haven't run the numbers on the throw, but I suspect they will be right at the minimums(25/15). I keep hearing that less is more with these aircraft, so it may be worth a try. No, mine isn't flying yet, because I spend too much time trying to optimize things. Hopefully later this year. Just about to put the canopy on.
Blunnies are a great pair of boots.
Tom.
Reply With Quote
  #9  
Old 03-06-2017, 03:03 PM
longranger's Avatar
longranger longranger is offline
 
Join Date: Mar 2007
Location: 45G, Brighton, MI
Posts: 1,719
Default

A 3/4" diameter spacer put my up stop at exactly 32 degrees.
http://mykitlog.com/users/display_lo...=169555&row=25
__________________
Miles (VAF# 1238, Paid up as of 12/2016)
RV-7 TU 904KM (reserved)
Wings Structurally Complete!!
SB Fuselage Just Past QB Stage


Construction Log
Picasa: Empennage Album, Wings Album, Fuselage Album


1955 Cessna 170B flying since 1982


'To get something you never had, you have to do something you never did.' -Unk.
Reply With Quote
  #10  
Old 03-06-2017, 11:17 PM
simatos simatos is offline
 
Join Date: Sep 2014
Location: vancouver canada
Posts: 83
Talking

yes i got out the hobby lathe and spun one down to 0.750 in and my deflections are about the same. Then the belt blew off the lathe so its counterpart on the other wing will wait till I locate new belts. The second one prob won't take all day to whip up I hope, again thats to everyone for the info
cheersG
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 12:19 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.