Sunday, July 4, 2010

A Matter of Trust...

... or, I suppose one could say, "A Line of Credit."

I was hoping to receive the extra fuel line that I had ordered from Van's last week so I could keep up my momentum on the fuel system this weekend. I still had some fuel line to work with, but most of the short runs are done. That leaves the big run from the fuel pump up to the fuel valve to do, and the amount of tube remaining after my first abortive attempt was too short. I had also ordered replacement screws and nuts to finish those pesky six screws that have given me so much trouble. Those needed to be done so I could install the plastic channel blocks that hold the fuel lines and brake lines. As you may remember, I had received a phone call from Aircraft Spruce to tell me that the Visa card that I used to pay for the tube bender had been declined due to suspicious activity. I had heard nothing from Van's, so I assumed all was well that order.

Not so much. My package arrived in time to allow me to continue work this weekend, but it contained a note.

I was thinking about how trusting those folks must be to go ahead and send the order without knowing that I'd eventually pay for it, but then it struck me that if I didn't pay, they were going to be very unlikely to send me a finish kit, or an avionics kit, or an engine kit.... yeah, I think they're pretty sure that they will get paid!  Still, it was an act of good customer service to just go ahead and send it so that I wouldn't have to wait all of those extra days to get the accounting straightened out.

As I was reviewing the steps for fabricating the 40.5" tube that makes the long haul from the fuel pump up to the fuel valve, I got to thinking that I ought to learn how to use the fancy tube bender with all of the intricate and arcane mathematical machinations detailed in the instructions that came with the it. First I measured and marked the 'L' length.

That line is used to match up with one of the plethora of markings on the tool. If all works out as it should, you are left with exactly the right length of tube before the bend.

You have to be careful while doing this. While it looks like the Sharpie(tm) mark on the tube is correctly aligned with the 'L' mark, it actually isn't. If you look closely at the spot that I pointed out in the picture, you will see that the 'O' line on the top part of the bender is not aligned with the 'O' on the lower part. That means that I didn't have the top part of the bender snugged down and aligned tightly enough on the tube. I reseated the tube in the tool until the O's lined up, then made the bend.


A perfect match! The math (well, there was no real math, to be honest.) worked!

So now the bad news: the tube bender that I have cannot make another 90 degree bend as close to the one that I had just made as the one depicted in the drawing. I snugged the tool up as tight as I could get it to the existing bend and hoped for the best. While it didn't match the drawing exactly, in the end it turned out to be close enough.

This is another of those tubes that needs to be pushed through bushings and bulkheads before the second flare is made, besides which I was anxious to see if my too-far-apart 90 degree bends were going to be a problem, so I guess I was in a hurry to get it into the plane. Due to its length, I had to feed it in through the lightening holes in the aft bulkhead. It took a little bending and scraping to get the unflared end up to the first bushing, where the bushing in question refused to allow through passage. The tube wouldn't fit through the bushing! It looked like either the bushing was too small, the slight angle of the tube trying to go through it was causing it to bind, or both. I ended up pulling the whole enchilada back out of there to see if I could figure out what was wrong.

After a bit of trying this and that, what I finally ended up doing was cutting off a few inches of extra tubing (which I could afford to do now that I have way more than I need - it's either feast or famine around here) and sliding it in and out of the bushings to loosen them up a little. Once I had them loosened up, I was able to wriggle and bend and coerce the tube back in through the aft bulkhead, through both of the bushings, and up to the fuel valve. Success!

But wait! What about the channel blocks that the tube is supposed to fit down into. For that matter, what about those pesky screws and nuts needed to hold the channel blocks in place? Drat. Out came the tube again.

You may remember that those screws weren't put in place because the nuts were way too tight and I stripped the screws out trying to get them threaded in. The replacement screws and nuts had arrived in the same package as the fuel tube, so I was ready to try again. I have been thinking about the proposed solution of running a 8-32 tap through them to loosen them up, and I ended up not being too keen on the idea. My fear was that it would loosen them too much - they're lock nuts for a reason. Well, with the new nuts it turned out that I wouldn't have to. For some reason, the screws went into the new nuts exactly like one would expect them to. That naturally left me wondering just what was wrong with the nuts that came with the kit, but I decided to let the teeth of that particular gift horse go unexamined. I was just happy to have it finally done.

With the screw posts in place to hold the channel blocks, I installed the blocks and pushed the fuel line through the maze again. You'd think it would get easier with repetition, but it didn't.

Yay! Progress!

Short-lived, though. Next step? Cut the end off the tube to make it the correct length (not needed, oddly enough) and pull it back out far enough to flare the end. And don't forget to put on a sleeve and nut!!!

The tube didn't have to come all of the way out (in fact, you would not want to pull it back out through the bushings since you wouldn't be able to get it back through them once it was flared) but it did have to be bent quite a bit to get it up where the flaring tool could reach it.

That was a treat for my knuckles!

Once flared, I screwed both fittings onto their respective ends.

I was going to do the last line that runs from the tank down to the pump, but it turns out that I'm missing the two sleeves build that line. That's what I get for not doing an inventory on the bags. It's only a couple of bucks worth of parts, but it's going to take a few days for them to get here. I'm also missing the nipple that goes in the gascolator, so I had to order one of those too.

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