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05-07-2014, 01:50 PM
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Join Date: Sep 2007
Location: pittsburgh pa
Posts: 533
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Bill. The link between the servo and the control attachment must be lengthened so that the servo arm is operating between 10:00 and 2:00. It can not operate between 8:00 and 10:00 as your set up currently does.
With current set up, when the servo is at about 9:30 your controls will be locked!!!! It is only by pure luck that this has apparently only happened this one time.
__________________
Gary Reed
RV-6 IO-360
WW 200 RV now an Al Hartzell for improved CG
Last edited by gereed75 : 05-07-2014 at 01:53 PM.
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05-07-2014, 02:07 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Quote:
Originally Posted by gereed75
Bill. The link between the servo and the control attachment must be lengthened so that the servo arm is operating between 10:00 and 2:00. It can not operate between 8:00 and 10:00 as your set up currently does.
With current set up, when the servo is at about 9:30 your controls will be locked!!!! It is only by pure luck that this has apparently only happened this one time.
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Are you talking about the 2nd picture I posted? If so, you are correct, and as I stated, that is the position it was in when it jammed, after the AP bent the plate doing a self-test on the ground. Prior to the AP bending the plate, it could not go over center and I flew that way for four or five years without any issues. In fact, I had just inspected that servo two weeks prior during my condition inspection and found nothing amiss.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
Last edited by N941WR : 05-07-2014 at 02:16 PM.
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05-07-2014, 02:20 PM
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Join Date: Aug 2010
Location: Wichita, KS
Posts: 1,958
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Quote:
Originally Posted by Toobuilder
Bill,
While similar, the execution between your pictures and the drawing provided have some subtle, yet important differences. Without seeing the actual dimensions of the two, the spacers are much shorter and larger diameter on the Tru Trak drawing, and the rod end is on the inside of the servo arm. Both contribute heavily toward increasing stiffness of the system.
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While Bill's installation does not match the TruTrak drawing linked, his setup does appear to conform to the RV9 roll servo installation drawing from Dynon which uses a 7/8" spacer.
Dynon Instructions
Apparently Dynon installation uses a longer bolt and spacer than TruTrak, and installs the rod-end bushing on the opposite side of the servo arm. I too have the Dynon installation. This is a solid argument for installing the rotation-limiter brackets. I'll be doing so ASAP.
__________________
Kurt W.
RV9A
FLYING!!!
Last edited by krw5927 : 05-07-2014 at 02:22 PM.
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05-07-2014, 02:32 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Time to admit something?
Quote:
Originally Posted by krw5927
While Bill's installation does not match the TruTrak drawing linked, his setup does appear to conform to the RV9 roll servo installation drawing from Dynon which uses a 7/8" spacer.
Dynon Instructions
Apparently Dynon installation uses a longer bolt and spacer than TruTrak, and installs the rod-end bushing on the opposite side of the servo arm. I too have the Dynon installation. This is a solid argument for installing the rotation-limiter brackets. I'll be doing so ASAP.
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I was on the Dynon Beta team for their autopilot and was the person who helped them come up with the RV-9 installation. Thus, I?m not sure if their directions follow my installation, or if my installation follows their directions.
Either way, I will try installing that rod per the Tru Trak recommendation this evening and report back.
I don?t recall why I put that longer bolt in there, there very well might be an interference problem when putting the push rod on the other side of the servo arm or it could be that I simply messed up. Either way, I will report back after I get a chance to pull it apart.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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05-07-2014, 02:44 PM
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Join Date: Sep 2007
Location: pittsburgh pa
Posts: 533
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Bill glad you read the last post before "fixing" and flying again. This is not about the length of the spacer at the attach point. Yes good practice would dictate re arranging the actuation arm to shorten that spacer.... But the most important point is to get the length of the actuation arm correct so that the geometry of the setup is correct
My reccomendation is to disassemble your current setup. Set your controls at the midpoint of travel. Then set the servo arm at 12:00 or 90 degrees to the actuation arm. Then make an actuation arm the correct length to maintain that geometry. Bolt it all together and check that the servo arm only moves throught 10:00 to 2:00 or so AND NEVER COMES CLOSE TO 9:00 while moving the controls through full range of motion
__________________
Gary Reed
RV-6 IO-360
WW 200 RV now an Al Hartzell for improved CG
Last edited by gereed75 : 05-07-2014 at 02:50 PM.
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05-07-2014, 03:00 PM
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Join Date: Sep 2007
Location: pittsburgh pa
Posts: 533
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Bill. The AP servo can not bend the tab. It was the center locked geometry and you pushing the stick that supplied the force to bend that mount tab. Think of a piston at exactly T D C. You can push it down with lots of force but it will not go down until it rolls past T D C. Your servo rod was "at TDC" and there is enough friction in a powered up servo that you can not get it past TDC. Result - locked control
__________________
Gary Reed
RV-6 IO-360
WW 200 RV now an Al Hartzell for improved CG
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05-07-2014, 03:05 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Quote:
Originally Posted by gereed75
...My reccomendation is to set your controls at the midpoint of travel. Then set the servo arm at 12:00 or 90 degrees to the actuation arm. Then make an actuation arm the correct length to maintain that geometry. Bolt it all together and check that the servo arm only moves throught 10:00 to 2:00 or so AND NEVER COMES CLOSE TO 9:00.
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That's exactly how it has been is set up since its installation, only I based it on the bell crank movement and not the aileron being centered, IIRC. It has been a long time since I installed that thing.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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05-07-2014, 03:08 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Quote:
Originally Posted by gereed75
Bill. The AP servo can not bend the tab. It was the center locked geometry and you pushing the stick that supplied the force to bend that mount tab. Think of a piston at exactly T D C. You can push it down with lots of force but it will not go down until it rolls past T D C. Your servo rod was "at TDC" and there is enough friction in a powered up servo that you can not get it past TDC. Result - locked control
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You are wrong on this point, it was the servo, in test mode, that bent the tab. Simple as that and allowed it to go over center. Once the tab was straightened, and reinstalled, it could not go over center.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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05-07-2014, 03:29 PM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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Quote:
Originally Posted by gereed75
... This is not about the length of the spacer at the attach point. Yes good practice would dictate re arranging the actuation arm to shorten that spacer.... But the most important point is to get the length of the actuation arm correct so that the geometry of the setup is correct...
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Yes, the over center geometry is the most critical aspect here, but it's more than "good practice" to address the length and diameter of the spacer. All issues are conspiring to cause safety issues in this case. This installation can be improved dramatically with a little effort.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
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Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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05-07-2014, 07:05 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Quote:
Originally Posted by Toobuilder
Bill,
While similar, the execution between your pictures and the drawing provided have some subtle, yet important differences. Without seeing the actual dimensions of the two, the spacers are much shorter and larger diameter on the Tru Trak drawing, and the rod end is on the inside of the servo arm. Both contribute heavily toward increasing stiffness of the system.
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OK...
I just returned from the airport. It is as I feared, there is not enough room on the roll servo to move the bearing to the top of the arm. This leaves me with three options:
1) Make a push rod that bends up. This could allow flex in the tube.
2) Add a doubler to the existing plate. This will require longer bolts.
3) Make a new plate with tabs bent up to stiffen it. This requires me to buy some 4130 and is probably the route I will go.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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