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Fuel-line attach to Cox prod. backplate

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Fuel-line attach to Cox prod. backplate

Post  roddie on Sun Jul 16, 2017 3:12 pm

Hey folks, "Bob" (rsv1cox) commented recently on my methods when working with fuel-lines. Today I was installing a Cox .049 product-engine (horseshoe backplate) on one of my airplanes.. and thought I'd share how I went about it. It's difficult to install a fuel-line onto the NVA/nipple "after" the engine is mounted.. or if it happens to "pull-off" the nipple after the engine is mounted. Really small ID fuel-line will usually stay-put.. but I prefer to use fuel-line that has a slightly larger ID.

This example uses line that has a .075" ID and a .165" OD. It's categorized as "small-size" line.. although "Dubro's" small-size line has a .042" ID for comparison. If your running a high-performance engine on a suction-feed.. (as opposed to a pressure-bladder..) a little less-restriction to flow can be an advantage.

That point aside.. here's what I do to help keep the fuel-line from being inadvertently/accidentally being "pulled-off" the NVA. I use a short "sleeve" of alloy-tubing that's close to my fuel-tubing's "OD".



I then insert the fuel-tubing into the sleeve. If it's a tight-fit; I apply a little petroleum-jelly to the end of the line.. and "twist/slide" the alloy-sleeve onto the line, so that there's approximately 1/4" of fuel-line protruding. Just enough to push-onto the NVA's nipple.



This can give the fuel-line some rigidity for the ease of "initial" installation onto the nipple. Once the fuel-line is installed as far as possible.. the "sleeve" can then be pushed-forward; which compresses the line around the nipple's barb. I used blunt tweezers to push the sleeve forward; being careful not to abrade the silicone fuel-line. After the sleeve is in-place, the fuel-line isn't going to pull-off unless it's "yanked-off".



It's these little details that can save a lot of frustration at the field.
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Re: Fuel-line attach to Cox prod. backplate

Post  Kim on Mon Jul 17, 2017 5:42 am

Thanks Roddie...gonna give this a try!
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Re: Fuel-line attach to Cox prod. backplate

Post  roddie on Mon Jul 17, 2017 1:40 pm

Kim wrote:Thanks Roddie...gonna give this a try!

I hope you do Kim! It's a simple step that can increase reliability. It can also bail you out, if you don't have any fuel-line that's small enough for the application.

I've posted this photo before.. but it's applicable to this thread. Try this; the next time you rebuild an engine with an integral fuel-tank.. (IE: Babe Bee, Golden Bee, Black Widow.. etc.)




Note also the "pick-up". A separate short piece of alloy-tubing with a notch filed in the end. The notch assures fuel-flow and keeps the pick-up located where you want it. It can really help to keep the pick-up in position when re-assembling the tank to the backplate. This example shows an OEM spring internal to the fuel-line. I'll admit; I don't always include one.. but they were originally there for a purpose. My belief is that the spring can help to disperse air-bubbles.. and possibly augment the fuel-flow through capillary-action.. Laughing Yea.. I'll go with that theory..
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Re: Fuel-line attach to Cox prod. backplate

Post  balogh on Tue Jul 18, 2017 12:55 am

Your theory may be right Roddie. I thought the spring was there to internally stiffen the pickup line and prevent it from buckling when bent that would restrict the fuel flow.
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Re: Fuel-line attach to Cox prod. backplate

Post  RknRusty on Tue Jul 18, 2017 2:31 am

Since we're revisiting theories on fuel line ideas, here's the first video experiment I ever made. Forgive the cheesy dramatic prelude, it was my first time using WMM for editing video:

https://youtu.be/xyA6He9EX8c

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Re: Fuel-line attach to Cox prod. backplate

Post  roddie on Tue Jul 18, 2017 6:58 am

Pretty cool vid Rusty! I know that you're partial to running bladders now.. but how'd this end up working on the Stuntman with that tank set-up? I'd like to build a Stuntman. I have one that my dad built. It's beyond practical-repair.. but I could copy it. Most of my designs are a tad large for the reed-valve engines.
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