Archive for February, 2010

Hose Fabrication & Transducer Bracket

I decided to fabricate my own fuel lines out of Aeroquip 303 hose and Aeroquip 491 hose fittings. The EAA has a nice video tutorial and I thought I was good to go. It was a little more difficult than I had hoped.
I learned a lot as I went along. I’ll share the following tips if you want to try it for yourself:

  • Use tons of lubricant. Pick the slickest stuff you can find. I used Tri-Flow and motor oil. I think WD-40 might work just fine, too.
  • Once you’ve got everything set up and you’re ready to start threading the mandrel into the hose, you might try tapping lightly on the end of the mandrel until the shallow metal threads start tapping lightly against the metal of the gold sleeve. This way, when you start pushing and turning, you know you’re about to have thread engagement. Don’t bang too hard or you’ll damage the threads! Just a tap or two.
  • Don’t be afraid to back the mandrel out if it gets really hard to turn. I’d do this rather than continuing to crank the mandrel down tighter against the hose nut. Just back it out, apply additional lube and screw it back in.

Here are a couple of my completed hoses. I buggered up the fittings a little bit, but these were used fittings to start with so I didn’t put all the scuffs on them!

The official dip for fire sleeve is quite pricey at about $130 per quart. On the advice of a friend, I thinned a glob of high-temp RTV using lacquer thinner. It didn’t mix perfectly, but after sitting for a few minutes, it was at least acceptable. I made it a point to stir the mixture a little bit before I dipped each end of the hose. You can see that it wicked up in the hose pretty well.

I’m installing a JPI fuel totalizer. The installation instructions state that the fuel flow transducer should have something like 6 inches of straight flow before and after the transducer. Not gonna happen in my installation. With a gravity flow system, I don’t want to be routing fuel all over the engine compartment just to have 6 inches before and after the transducer. Instead, I just did the best I could and kept the fuel hoses fairly simple. I’ve seen installations that are far more “bendy” than mine and the owners claim their fuel flow system is still very accurate. I fabricated the yellow bracket as a mounting pad for the transducer. I glued it to the kidney-bean-shaped tank using JB Weld. I actually think it turned out quite well. I hope it works! [Oh. Before somebody scolds me… I am planning on using steel fittings as per the JPI instructions. The blue aluminum fitting was temporary for initial hose measuring and fitting. I’ve got steel fittings on order from Aircraft Spruce.]

This is the tool to install the stainless band clamps to secure the firesleeve. The tool was $18.65 and each stainless band cost $2.20. I didn’t price it out, but I’m betting I bought all the tools and supplies to make the hoses and still saved a little money. By using the proper tools and taking my time, I’m pretty certain I achieved an acceptable level of quality and saved a few bucks. On top of all this, it was very handy to be able to make, test fit, and re-make the hoses as necessary to achieve a perfect fit.

This is a close up of my finished banding at the end of the firesleeve. You initially bend the band at a 90 degree angle before you cut the band and remove the banding tool. I then tapped the band tight against the sleeve with a small hammer and cut off the excess band using a Dremel with a cutoff wheel. I tapped a little more with the hammer and then polished away the rough edges with my Scotchbrite wheel. I’m pretty pleased with the results.

Paint, Gascolator and Transducer Bracket

February 16, 2010. The time had finally come. I’m finished with all the sanding and filling on the remaining fiberglass pieces and they’re ready for the paint shop. I tried my hand at painting, but quickly realized I’m no good!

These are the parts and pieces of my gascolator. It was looking pretty ratty so I decided to blast it in my bead blasting cabinet and apply a little rattle can paint. It’s funny how when everything else is shiny and new how something like this sticks out like a sore thumb.

I decided I needed to fabricate a new bracket to hold my fuel flow transducer. At this point in the project (for good or for bad) I seem to have plenty of scrap aluminum lying around my shop.

Here are the gascolator parts after the strip and repaint. I’m hoping this won’t look so out of place when mounted on my freshly-painted white firewall.

Sorry some of these posts don’t fall neatly into a single category. At this point in the project, I’m no longer focusing on a single area in any given work day. It’s more a matter of wrapping up all the loose ends and keeping everything moving forward at once. That’s why pages like this are tagged with several different categories.