Large fuel-line/small nipple

roddie Thu Mar 13, 2014 12:19 pm

I'm sure I'm not the first person to think of this, but I thought I'd post the idea for others to try. Fuel draw can be an issue with a suction-only/non-pressure system.. so it makes sense to use the least restrictive/largest i.d. fuel-line that you can. I needed to at least try this because of an over-sized venturi/back-plate that I'm running on my CEF Speed Contest engine. I haven't tested the larger line on my engine yet.. but I'm posting the idea for those who want to use a large size fuel line on their own set-ups.

Obtain some hard/round thin-wall 1/4" o.d. tubing (I used K & S 1/4" Brass tubing) and cut sleeves approx. 1/4" long; for as many connections needed. Dress the ends smooth and twist the end of the large size fuel-line into the sleeve, until the line and sleeve are flush. This compresses the fuel line and decreases it's i.d. only on the end... for a nice tight/secure fit on a small Cox spray-bar nipple. It's easy... really neat looking, and just may help fix a fuel-draw issue with your hard-tank.

Large fuel-line/small nipple 3-13-113

**RknRusty** Thu Mar 13, 2014 1:19 pm

It might be helpful. A guy at SH was having fuel draw troubles with his Tee Dee .049 and claims bigger line solved it.
Rusty

fredvon4 Thu Mar 13, 2014 5:07 pm

Great hint... many ways to skin the cat and this is a good looking way

I was making a noose of copper wire to secure the connection...I think this is a mite easier method

roddie Tue Apr 01, 2014 5:12 pm

I'm happy to say that running large-size fuel line made a BIG difference in my bench-runs today. I ran my 6.15oz. Speed model's uni-flow hard-tank through 2 tankful's of Sig Champion "25" and got 2 screaming-steady runs on a black Cox 5 x 4 round-tipped prop.

The engine is fitted with a repro .049 Tee Dee SPI cyl./piston, standard crank, high-flow (Bernie's red) horseshoe back-plate, Mylar reed and standard 80 tpi needle.

How my hard-tank behaves in the air, remains to be seen... but I am optimistic. I may bolt the set-up on the nose of another 1/2A profile model.. rather than risk my Rare bear for the first flight trials.

**RknRusty** Tue Apr 01, 2014 6:50 pm

roddie wrote:...How my hard-tank behaves in the air, remains to be seen... but I am optimistic. I may bolt the set-up on the nose of another 1/2A profile model.. rather than risk my Rare bear for the first flight trials.

Roddie, it will run fine in the air, but you should shim the rear of the tank behind the vibration padding so it's kicked out farther than the front. That keeps the fuel covering the pickup much better.
Rusty

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Large fuel-line/small nipple

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