VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.

  #11  
Old 06-03-2021, 11:36 AM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,401
Default

Quote:
Originally Posted by seagull View Post
Scott,

I have complied with SB-00026 but your comment about SB 13-03-06 Rev.1 made me think maybe I missed something. I went to the Vans site and could not find SB 13-03-06 Rev.1 with a search or in the SB's.

Can you provide a link?
Sorry... my fault.

It is SB 18-03-06 (a 3 looks kind of like an 8 doesn't it?) Edited my post with a correction.

Link to the SB - https://www.vansaircraft.com/service...s/sb-18-03-06/
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #12  
Old 06-03-2021, 12:26 PM
seagull seagull is offline
 
Join Date: Dec 2019
Location: San Bernardino
Posts: 312
Default

Scott,
18-03-06 was what I had followed.

I had my springs installed with the tail against the bolt head as shown in 18-03-06. When I tightened the throttle arm nut the last turn created friction on the arm rotation. This happened on both carburetors. the friction was caused by the spring being squeezed.

My solution was to let the tail drop into the notch of the retaining plate.

This kinda defeats the purpose of the backing plate since the last coil is now riding on the shaft.
__________________
Live as if you were to die tomorrow. Learn as if you were to live forever.
-- Walt --
Reply With Quote
  #13  
Old 06-03-2021, 01:47 PM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,401
Default

SB-00026 refers to KAI page 50-05 (attached below) for installation details of the VA-00276.
In figure 2 it shows that the inboard leg of the spring is supposed to be against the tang of the VA-00176 Spring Retainer.

For possibly some additional clarity... What the Spring Retainer does is constrain the inboard end of the spring (the end that will bare against the throttle shaft because of the wound up torsion load in the spring) so that it is held in proper position with the throttle shaft projecting through its center. Additionally, with the leg of the spring rotated to bare against the tang on the Spring Retainer (highlighted with red arrow in attached drawing), it adds a small amount of additional spring tension.

If the torsion spring and Spring Retainer are properly installed, and there is no abnormal friction in the throttle cables, we have found that the system performs very well and the carb synch is very accurate through the entire throttle range (as checked on multiple ULS RV-12's).
Attached Thumbnails
Click image for larger version

Name:	Screenshot 2021-06-03 123503.jpg
Views:	65
Size:	284.2 KB
ID:	12199  
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #14  
Old 06-03-2021, 05:28 PM
seagull seagull is offline
 
Join Date: Dec 2019
Location: San Bernardino
Posts: 312
Default

Scott,

That is the way I have them now, your pic with the red circle, no binding.

What if you add that pic to SB-00026 along with the pics that are there, just a thought.
__________________
Live as if you were to die tomorrow. Learn as if you were to live forever.
-- Walt --
Reply With Quote
  #15  
Old 06-03-2021, 05:53 PM
seagull seagull is offline
 
Join Date: Dec 2019
Location: San Bernardino
Posts: 312
Default

Quote:
Originally Posted by rvbuilder2002 View Post
If the torsion spring and Spring Retainer are properly installed, and there is no abnormal friction in the throttle cables, we have found that the system performs very well and the carb synch is very accurate through the entire throttle range (as checked on multiple ULS RV-12's).
I don't want to start a battle with the expert, just sharing my experience.

My carbs would not stay in balance, the problem was tracked to the cables were not moving evenly, measured with calipers. I discussed this with McFarlane and they offered to check my cable for problems. I thought maybe there was problem where the cables came to the "Y" into one cable.

I pioneered the idea of adding a 3# additional expansion spring and it solved my balance issue as far as the cables traveling equally.

I was felt I was using a bandaid to hide a cable problem so I bought a new throttle cable, installed it with the upmost care and large radiuses. Then I removed the additional springs. the travel on the cables would occasionally be different, I could lightly pull on the short cable and it would move another .040 out. Maybe engine vibration of unbalanced carbs will nurse the cables into position with just the tension of the torsion spring, but I felt they should move equal without vibration help.

I put the #3 spring back on with the torsion and have not looked back. This was well over 100 hours ago.
__________________
Live as if you were to die tomorrow. Learn as if you were to live forever.
-- Walt --
Reply With Quote
  #16  
Old 06-04-2021, 08:36 AM
bobg56 bobg56 is offline
 
Join Date: Nov 2018
Location: Peachtree City, GA
Posts: 179
Default

I agree with Seagull, I had replaced the throttle cable and still had some slop in the cable movement, adding the additional springs did the trick making the sync easier and more accurate.
Reply With Quote
  #17  
Old 06-04-2021, 09:24 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,425
Default

The outer sheath on these cables is spiral wound wire which has a few drawbacks. Dirt and grime can penetrate the cable housing along its length. Vibration can impart the spiral grooves onto the surface of the sliding multi-strand inner cable.

The J-3 Cub I owned developed a stiff throttle cable. Upon disassembly, the solid inner wire had grooves that matched the outer sheath and caused binding.

Eye-opener for sure…
__________________
-
Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 670

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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 12:00 AM.


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.