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.


Go Back   VAF Forums > Main > RV Building Tips/Techniques
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 02-29-2012, 09:03 PM
Ironflight's Avatar
Ironflight Ironflight is offline
VAF Moderator / Line Boy
 
Join Date: Jan 2005
Location: Dayton, NV
Posts: 12,835
Default Tip: Don?t Overtighten Fuel Sender Connection Screws!

One of the minor squawks we have had on our RV-3 has been an intermittent left fuel sender. Well, it started out intermittent, then went from ?mostly dead? to ?all dead? after awhile. Since we use the extremely accurate totalizer for fuel management, this was just an annoyance that we wanted to fix before the paint shop, and with the week?s forecast calling for continued glop, Louise and I figured it was a good tie to tackle it.

The RV-3 wing design is a little different from its siblings. On later model RV?s, the inboard end of the tank is set out from the fuselage farther than the inboard wing rib after of the spar. This leaves a reasonable space in which to work between the tank and the fuselage. On the -3, the inboard end of the tank is co-planar with the inboard rib, so there is only about two and a half inches in which to work. I frankly was worried that we?d have to pull the tank to get the sender out. Working with the screws and proseal in that tiny space was not going to be fun. If we has to pull the tank, I wanted to do it before paint, obviously. But there was no harm in trying to get it out with the tank on the airplane, so off came the root fairing, and microsurgery began.

Getting the five screws that hold the sending unit removed was made a whole lot easier because we had used Allen-head screws instead of the stock pan-head Phillips. It was still tedious with an Allen wrench, but would have taken as long to go and buy the right Allen bit for our small right-angel ratchet driver. I was really worried about the proseal removal, but it turned out to be fairly simple using a razor blade and two Plexiglas scrapers we made from a canopy scrap. Once we got it broken loose, it took a little creative puzzle-solving to get the float sender out of the tiny gap, but once the old one was out, it was easy to see what had gone wrong.

The screw that holds the sense wire in place goes into a bras ?button? that is pressed into an insulator on the plate. The rheostat wire is soldered to this button. Because there was no room to use even a stubby driver to attach the wire, we did it with the mini ratchet and a screwdriver bit ? and the ratchet handle provided WAY more torque than a screwdriver would have ? when the screw got too tight, it spun the ?button?, breaking the solder joint on the wire. The moral of the story ? BE VERY CARFUL NOT TO TIGHTEN THAT SCREW TOO MUCH!! A star washer and a light touch should be sufficient?..



Installing the new unit was straightforward, if messy. Messy because we had to maneuver it into place, then apply the proseal using tongue depressors, working over our heads. It sure isn?t as neat as when it was done on the wing rack ? but it holds fuel. One thing I always do when using proseal is to mix more than I need, and use the extra on the mixing board as a ?test coupon?. When I think it has cured sufficiently, I section the coupon with a razor knife to make sure I am happy that it has set properly, and is ready for fuel.

This was the big ticket ?fix it? item on junior?s list before paint, so now we will just do some tinkering with fiberglass until it disappears into Grady?s GLO custom next month. I like to think that when it comes out of paint, it?s like driving a new car of the lot ? and it?s great to have everything working.

Paul
__________________
Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
Reply With Quote
  #2  
Old 03-01-2012, 10:46 AM
jjconstant's Avatar
jjconstant jjconstant is offline
 
Join Date: Dec 2006
Location: Oakland CA
Posts: 771
Default

I now feel A LOT better about having done exactly the same thing on my left tank It took me a long time of troubleshooting (flailing based on presuming a bad ground path based on DVM readings) and procrastinating before I resigned myself to removing the plate with the proseal. It wasn't nearly as bad as I had made myself believe, but it still took me a while to figure out what was wrong...the broken wire was still bent stiff in a way that made it look connected but there was intermittent contact when checking with a DVM and it wasn't until I realized that depending on how I was holding the unit it was "good" or "bad". I then started looking really closely and discovered the completely broken wire. If I recall it is a solid core wire, not stranded and I think the heat from the solder might have made it quite brittle.

Thanks for posting this Paul.

All Best

Jeremy Constant
(Starting to put the plane back together tomorrow with finished paint at the paint shop)
Reply With Quote
  #3  
Old 03-01-2012, 06:32 PM
Ironflight's Avatar
Ironflight Ironflight is offline
VAF Moderator / Line Boy
 
Join Date: Jan 2005
Location: Dayton, NV
Posts: 12,835
Default

Ah ha! So I wasn't the only one to mess this up.....
__________________
Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
Reply With Quote
  #4  
Old 03-01-2012, 09:10 PM
SHIPCHIEF SHIPCHIEF is offline
 
Join Date: Mar 2008
Location: Seattle
Posts: 1,412
Default

Dang!
Mine don't work. I tightened them with a srewdriver bit and a 1/4" wrench, though I tried not to over do it.
I wish you had posted this a day sooner.
Maybe I did some other bone head thing. I guess I'll test tthe meters with a rheostat and make sure I didn't reverse the power and ground leads or something...
__________________
Scott Emery
http://gallery.eaa326.org/v/members/semery/
EAA 668340, chapter 326 & IAC chapter 67
RV-8 N89SE first flight 12/26/2013
Yak55M, and the wife has an RV-4
There is nothing-absolute nothing-half so much worth doing as simply messing around with Aeroplanes
(with apologies to Ratty)
2019
Reply With Quote
  #5  
Old 03-01-2012, 09:58 PM
JoeBlank's Avatar
JoeBlank JoeBlank is offline
 
Join Date: Mar 2005
Location: Molalla, Oregon (KOL05)
Posts: 529
Default

I just ran into this myself recently. IMHO the screw may oxidize, corrode, and lock in the assembly making it problematic when you need to remove it a few years later. The screw, ring terminal, and bushing all turn together and become impossible to remove, ruining the sender.

To avoid the problem in the future, I fabricated up a combination ring terminal (to attach to the sender screw) and male spade on the other end. Crimped and soldered the assembly together and installed it.

Now I just disconnect the sender wire by pulling the insulated spade fitting apart when needed. No need to turn that screw anymore and risk the same problem again. We'll see how it works over the long term. The fact is that I'll probably have to perform some sort of tank maintenance in the future.
__________________
Joe Blank
RV-6
IO-320-D1A
Advanced Flight Systems

Van's Aircraft Inc. Technical Support-Retired
EAA Tech Counselor & Flight Advisor

www.westcoastravens.com
Reply With Quote
  #6  
Old 03-02-2012, 09:01 AM
arunnells arunnells is offline
 
Join Date: Mar 2010
Location: Calgary, Alberta, Canada
Posts: 130
Default Me too!!

I re-painted my 6, re-installed the wings (72 bolts), I had also pro-sealed in two new fuel senders. When I was hand tightening the little screw with two fingers on a stubby Phillips, the darn thing snapped!! Argh! I couldn't believe I could have overtightened it with two fingers! So frustrating, I too wish I had read this post before doing that. What a simple thing, and sooo much work to correct.
__________________
RV-6 tip up,190hp,Pmag,ported/flowed ECI heads, WW200 prop,older glass panel,long range tank,SOLD
RV-3A tip over, 170 hp, dual Pmags, 15 gal wing tanks, CN-1,CN-2 wing mods, D10A, XM396, SOLD
Murphy Rebel Elite purchased and flying
DR-107 One Design project with Schuenemann 21 foot wing, wing tanks, 50% done SOLD

Last edited by arunnells : 03-02-2012 at 09:06 AM.
Reply With Quote
  #7  
Old 03-02-2012, 12:20 PM
Rupester Rupester is offline
 
Join Date: Dec 2005
Location: Mahomet, Illinois
Posts: 2,195
Default Arggghhhh ....

... On the very day this was posted, I made that wire connection and installed my R wing. I'm praying I didn't over tighten that son of a gun. I used a regular screwdriver and tightened it before the wing went in place, I.e no mechanical advantage from wrench assist. Fingers crossed.
__________________
Terry Ruprecht
RV-9A Tip-up; IO-320 D2A
S. James cowl/plenum
(Dues paid thru Nov '18)
Reply With Quote
  #8  
Old 03-02-2012, 09:05 PM
HFS HFS is offline
 
Join Date: Aug 2009
Location: Lemoore, CA
Posts: 384
Default What I did - (after reading your post)

Paul -

I have the same sending units for my -3 (under construction) that you do, so your revelation came at the exact right time for me, as I am just finishing the slow build tanks. Of my two units, one of them had the "rolled" head of the barrel rivet (that the sensing wire solders onto) underneath its retaining washer, thereby letting the whole thing rotate with very little rotational input - like cinching down on the connector screw. The other one appeared OK, but I still didn't like the idea of being able to turn the whole thing without knowing it and going down the path of unintended consequences.

This sort of reminds me of the issue with the fuel pickup tube and the SB and update necessary to take care of that issue.

So having said the above, what I did for my own comfort zone was to red locktite a 10-32 x 3/4" long allen set screw into the threaded receiver of the barrel rivet - taking care to make sure the (soldered) head of the rivet remains in its original position. Then I thread a 10-32 pattern nut (reduced head size) onto the set screw and cinch it down (also with red locktite) nice and tight, putting the set screw in tension against the threaded rivet barrel. Now, when I want to install/remove the sense wire, I'll place a 3/32 allen wrench in the set screw to maintain correct position of the barrel rivet and turn the holddown nut against the set screw wrench.

Anyway, that's my story and I'm stickin' to it!

HFS
RV-3 S/N 11226 Under Construction
Reply With Quote
  #9  
Old 04-16-2012, 10:20 AM
Mike S's Avatar
Mike S Mike S is offline
Senior Curmudgeon
 
Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 16,106
Default

Quote:
Originally Posted by Ironflight View Post
until it disappears into Grady’s GLO custom next month. I like to think that when it comes out of paint, it’s like driving a new car of the lot – and it’s great to have everything working.

Paul
It is next month.

And then some....................
__________________
Mike Starkey
VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."

Last edited by Mike S : 04-16-2012 at 10:51 AM.
Reply With Quote
  #10  
Old 04-16-2012, 10:40 AM
JonJay's Avatar
JonJay JonJay is offline
 
Join Date: Jan 2007
Location: Battleground
Posts: 4,348
Default

Quote:
Originally Posted by Joe Blank View Post
To avoid the problem in the future, I fabricated up a combination ring terminal (to attach to the sender screw) and male spade on the other end. Crimped and soldered the assembly together and installed it.

Now I just disconnect the sender wire by pulling the insulated spade fitting apart when needed. No need to turn that screw anymore and risk the same problem again. We'll see how it works over the long term. The fact is that I'll probably have to perform some sort of tank maintenance in the future.
Joe - good thinking. I used a standard spade lug available for terminal blocks. I premade my wiring harness with insulated spade lugs for all my intersection wiring. I was not aware of this problem, so it was purely by accident that I did it that way. I did not get to learn this lesson when I had a sender fail. Blind squirrel.
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.

RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
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 01:15 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.