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  #1  
Old 05-05-2016, 08:37 AM
jeffw@sc47's Avatar
jeffw@sc47 jeffw@sc47 is offline
 
Join Date: Aug 2014
Location: Simpsonville, SC (SC47)
Posts: 248
Default RV14-Fuel Sender Float Wire Bends

I messed up the two float wires supplied with the sender units yesterday. Bent the first one "precisely" as shown in the diagram Page 18-10. My definition of "precisely" means that I fabricated a plywood jig to hold the wire along the 4" lengths very tight and got the 90 degree bends sharp with a small radius, the arm lengths were as close to the diagram specs as anyone could get them.

After bending the first, the clamp loop around the float interfered with the #2 rib and would not work freely. Tried to put a couple of bends in the leg coming from the sender unit to shorten the leg - kind of fixed it but not good solution. So I bent the other wire per the design specs thinking I the first was not precise enough. Same outcome and the second one was no better than the first - perfect in my opinion. Second also interfered with the rib.

So I got out my measurement tools, my CAD tools, my scanner, and my kit of software. In the diagram (Figure 1, page 18-07) showing the arc swing and scaling of the design I found a couple of discrepancies.

My findings and solution - you will need to decide for yourself whether I got this correct or am off base:

This I Believe - scrutinize what I found and if you see that I am wrong please let me know.

1- The distance between the facing surfaces of the ribs each side of the compartment where the float is located is approximately 8 7/16", almost 1/2" less than the space indicated (8 29/32") in the diagram (Fig 1, 18-07).

2- The arc of the swing designed is not indicated correctly in that the center-point of the swing shown is approximately 3 1/2" beyond the presumed c-p shown at the sender. The arc swing as I calculate is 6 7/16" with the center of the swing at the post inserted into the sender unit.

3- In the diagram, I created the pdf scan (then scaled to actual size) is over-laid with CAD construction - BLUE lines highlighting the designed tank ribs locations, floats, and swing arc; and the RED lines indicate the float wire bends as designed on Page 18-10 with their swing arc.

[IMG][/IMG]

4- The interference point of the actual swing arc and the actual location of the tank rib corresponds exactly with what I found when bending the wires as designed and temporarily installing the sender in the tank. I inserted some 1/32" thick paper shims to simulate the ProSeal gasket thickness.

5- Also, I believe that the bend diagram on page 18-10 showing the 1/2" leg at the sender end of the wire is bent the same direction relative to the float end clamp for both float wires. At first I thought that it would be opposite the left float and that was part of the reason the first wire was discarded. I am still trying to convince myself of that. This float wire bending is akin to a Rubics Cube.

I found that Van's does have a supply of replacement float wires, so I ordered 3 wires to do-over the bends, at $5.50 each. I believe that if I shorten the 4" legs by 1/16" - 3/32" each, the float will clear the rib and I will have the 1/16" clearance called for top and bottom from the skins.
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  #2  
Old 05-05-2016, 09:16 AM
Ron B. Ron B. is offline
 
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I just bent mine in a vise as per plans and then tweaked them for clearance. Mine seemed fine.
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  #3  
Old 05-05-2016, 12:48 PM
KeithB KeithB is offline
 
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Location: Granbury, TX
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As I recall, I painstakingly tried to match the drawing and ended up with interference just as you experienced - the drawing and measurements make the "arms" too long. On the first one (already bent), I shortened the arms with V bends and on the second I shortened the arms.
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  #4  
Old 05-05-2016, 01:44 PM
Jake14 Jake14 is offline
 
Join Date: May 2014
Location: Seattle
Posts: 219
Default float interference

Good bit of work Jeff. I had the same problem only worse, since I did it on a QB wing and assumed all would be ok if I bent per plans since the clearance on the drawing looked more than adequate...then after pro-sealing in place, I discovered the interference. I managed to reach in through the drain and vent holes with a hooked rod and tweak the bend to eliminate the interference, but I should have checked first...

Whoever drew the arc on Fig 1 apparently used the wrong center point...

Last edited by Jake14 : 05-05-2016 at 01:58 PM.
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  #5  
Old 05-05-2016, 07:01 PM
Tom023 Tom023 is offline
 
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Location: Cypress, TX
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Ouch! My eyes hurt just looking at that. My first one I bent in a vice to size and it was too big. I put two crimps in it with fluting pliers and it was fine. The second one I made a tad smaller and it was perfect.
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  #6  
Old 05-06-2016, 07:45 AM
smash smash is offline
 
Join Date: Apr 2013
Location: Fair Oaks,CA
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I just worked on those last week and had a similar problem. I put a v-bend in and tweaked until it worked in the tanks. On that topic- how well do these floats actually work in practice? I never trust the floats in my Mooney. I dip my tanks before every flight and use a fuel flow computer to monitor fuel burned.

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  #7  
Old 05-06-2016, 08:14 AM
ShortSnorter ShortSnorter is offline
 
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Location: NOLA
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I'm with Ron on this one. Get it close and make small tweaks. I was more concerned with accuracy on the low end, so I made sure that the sender bottomed out per specs. On the high end of travel, I'm assuming my tanks will take slightly longer to show a drawdown since my upper limit of travel doesn't place the float as close to the top surface.

The float wires are cheap. Ask me how I know.
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  #8  
Old 05-29-2016, 12:22 PM
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czechsix czechsix is offline
 
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Location: Spring Hill, KS
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Quote:
Originally Posted by jeffw@sc47 View Post
5- Also, I believe that the bend diagram on page 18-10 showing the 1/2" leg at the sender end of the wire is bent the same direction relative to the float end clamp for both float wires. At first I thought that it would be opposite the left float and that was part of the reason the first wire was discarded. I am still trying to convince myself of that. This float wire bending is akin to a Rubics Cube.

I found that Van's does have a supply of replacement float wires, so I ordered 3 wires to do-over the bends, at $5.50 each. I believe that if I shorten the 4" legs by 1/16" - 3/32" each, the float will clear the rib and I will have the 1/16" clearance called for top and bottom from the skins.
Jeff, thanks for posting this info. It was good timing as I needed to bend the float wires yesterday. I reduced each of the 4" legs by 3/32" per your advice and they fit perfectly, with about 1/8" clearance to the rib. Also I can confirm that you bend the wires for both tanks exactly as shown in the isometric view on page 18-10 and install the float pointing the same direction as the 1/2" leg on the sender end of the wire. In other words, don't try to make the right one opposite of what is shown for the left one. When installed in the right tank this will result in the float pointing back towards the aft baffle (if it were pointing forward like it is in the left tank it would interfere with the vent line).

Thanks,
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