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  #1  
Old 06-21-2011, 10:15 PM
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rocketbob rocketbob is offline
 
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Location: 8I3
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Default Tip: Fuel Cap mods

Often I find it fascinating how creative people can get in solving problems but overlook the obvious. Seeing how creative people can get in coming up with CNC machined levers to open fuel caps, and not fixing a simple geometry problem, is one of those things. The following mod takes about 5 minutes to do with a scotchbrite wheel. It will allow you to easily open your caps with a fingernail--no fancy schmantzy tools required!


Step 1. Disassemble the cap. Remove the locknut, and unscrew the bottom piece, and pull the lever assembly out of the fuel cap casting.



Step 2. Using your scotchbrite wheel, cut a negative rake aft of the pivot axis, with the forward end just slightly forward of the pivot pin. Then carefully smooth the radius forward of that. It doesn't take much! The angle is exaggerated with the red lines for illustrative purposes.



When you're done you want it to look like this. The negative rake angle and the larger radius working against the wear plate make the cap much easier to operate. It makes the cap snap shut but at the same time makes it easy enough to operate that the cap opens easily with a fingernail. The key is to not overtighten the cap. It does not have to be air tight to keep fuel in and water out. In 11 years of flying my RV and leaving it outside many times in the rain, I never once saw any water in the fuel samples.

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Bob Japundza CFI A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
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  #2  
Old 06-22-2011, 11:01 AM
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kentb kentb is offline
 
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Thumbs up Looks to easy

Thanks Bob. I am going to do this tonight.

Kent
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  #3  
Old 06-23-2011, 09:18 AM
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kentb kentb is offline
 
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Default Bob, This is great.

I did the mode last night on my scotch brite wheel. It took all of five minutes and results are great.

It is so simple.

What else don't I know?


Kent
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  #4  
Old 06-23-2011, 09:28 AM
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tkatc tkatc is offline
 
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Default

Kent, you may or may not know this but Jeff Vaughn recently taught this to me. After you raise the fuel cap lever, push straight down on that lever and it will then relieve the seal so you wont have to struggle to remove the cap. Before knowing this I was wiggling/twisting the cap to release it!

I like the scotchbrite idea. Might have to give it a go!
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  #5  
Old 06-23-2011, 09:41 AM
Bavafa Bavafa is offline
 
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Location: Sacramento, CA
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Default

Thanks for the tip, I will be doing this too.
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  #6  
Old 06-23-2011, 11:30 AM
asav8tor asav8tor is offline
 
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Location: Seattle, wa
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The fact that it takes a little something to open other than a finger is a slight deterrent against little fingers at an airshow opening the cap. Perhaps a slight deterrent from a 6 year old opening the cap and putting something in the tank. Of course locking caps are better; short of that I would leave the cap unmodified.
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  #7  
Old 06-23-2011, 11:53 AM
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rocketbob rocketbob is offline
 
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Quote:
Originally Posted by asav8tor View Post
The fact that it takes a little something to open other than a finger is a slight deterrent against little fingers at an airshow opening the cap. Perhaps a slight deterrent from a 6 year old opening the cap and putting something in the tank. Of course locking caps are better; short of that I would leave the cap unmodified.
Using that logic, we should all be flying high-wing airplanes to prevent children from climbing on them.
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Bob Japundza CFI A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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  #8  
Old 06-23-2011, 12:11 PM
civengpe civengpe is offline
 
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Location: Houston, Texas
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Default

Better make sure Van doesn't read this post or you might get mentioned by name in his next safety post!


Disclaimer: This post is intended to be funny. I am an engineer, so I fail in this type of endeavor quite often. I apologize in advance if I offend anyone here.
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  #9  
Old 06-23-2011, 12:30 PM
gasman gasman is offline
 
Join Date: Mar 2007
Location: Sonoma County
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Default

Quote:
Originally Posted by tkatc View Post
Kent, you may or may not know this but Jeff Vaughn recently taught this to me. After you raise the fuel cap lever, push straight down on that lever and it will then relieve the seal so you wont have to struggle to remove the cap. Before knowing this I was wiggling/twisting the cap to release it!

I like the scotchbrite idea. Might have to give it a go!
You can just lubricate and adjust the stock cap and it will work just fine without grinding anything off. Just try it first. The nut is a lock nut. back it off and spin the disc out to make the lever easer to work. Lube the O-ring first, then adjust so the cap will drop into the neck with a little resistance.

Pushing down on the lever to relieve the seal as mentioned above means that the O-ring can't slide on the taper and it needs to be lubed.

Why is it so hard for people to understand? Just remove a cap and look how it operates................ you will then understand that the O-ring MUST slide on the taper (requiring lube) or you will have a hard time removing and installing the cap. And you will stress the hinge pin and break it.
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  #10  
Old 06-23-2011, 12:46 PM
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rocketbob rocketbob is offline
 
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Quote:
Originally Posted by civengpe View Post
Better make sure Van doesn't read this post or you might get mentioned by name in his next safety post!
A mod to the fuel system!!
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Bob Japundza CFI A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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