fuel pickup tube spring

It will run without the spring.  

Over the years, I think many of us (at least I did) thought it was used to keep the tubing from kinking when the tubing was bent into a U shape.  Others have suggested that it may serve as a crude filter to block some of the larger debris.  

However, Rusty showed us a video where he demonstrated that the spring improved the capillary action of the tubing and actually helped pull fuel into the inlet tube.

EDIT: Looks like Ken slipped in while I was typing.

Thats means I need to install one, for better fuel feeding.

tru168 wrote: Thats means I need to install one, for better fuel feeding.

This is the Rusty's thread on springs.

https://www.coxengineforum.com/t449-experiment-with-the-spring-in-the-babe-bee-pickup-tube?highlight=fuel+tube+spring

Thanks for info, I should search before I ask this question.

Gentlemen:
Somehow this item appears to me to be over thought! I have thrown my springs into the junk parts drawer well over 10 years ago. Mine are now replaced with bent aluminum tubing that is SECURELY attached to the backplate by fuel line.
My mufflered Cox Black Widow (w/ a Top Ftite 5-1/4 X 4 nylon prop & Sig 35% fuel) on my Coroplast trainer is fully capable of doing loops, fiqure 8's, inverted flight etc. It runs real sweet with the only noticeable item (if you listen hard) is the engine leans out slightly during the run. I think this is quite NORMAL with non uniflow vented tanks.
My trainer has been POUNDED INTO THE GROUND numerous times & the engine continues to start easily & run STEADILY flight after flight (the muffler helps keep the cyl clean from grass & dirt...).

Bottom line, I'd try a fixed pick up arrangement. I think it's shown in photos in my mouse race article...

Keep 'em flying!

Paul (aka Mr. Mouse)

Thanks, Paul. I'm the Chief Forum Overthinker(CFO). Dang, that sounds important, I need to ask for a raise. 

Hi Paul,

I ran a few tank without spring ,and its lean out too at near the end of tank.
May I know what type of muffler you use? the QRC type, or Cox tether car type? Most of black widow come with SPI cylinder, performance will be greatly reduced if using muffler. did you using cylinder shim to delete the SPI?

Hi Jocob,


Yes , this is the one! thanks for info. huge difference between early BW and Estes BW.
now I know , at least I bought a black widow, not the custom built engine. A question here, Does it came with Hi-comp. glow head ? or normal glow head? mine normal glow head.

I want to ask more about the glow head,and you just answered. I've heard of Firefly glow head, but this is the first time I see from picture. thanks for sharing !

Hi Tru,
I had a few juniors fly my mufflered "Coroplast trainer" this week-end. It was pounded into the ground many times but just kept on running smooth & steady with excellent (instant) starting.
We even flew it inverted & did figure 8's too.
I'm convinced my solid tubing pick-up helps use up all the fuel because it's essentially fixed in the correct position & has no real way of moving.

Your observation that most Coxes lean out at the end of the tank is true. They will all do it to some extent. Some not very much, others quite a lot.. I firmly believe that it's a function of the tank being a regular suction tank design rather than being a proper "uniflow" design that feeds more steadily throughout the run.
That being said, my engines do not lean out very much. It's a pretty subtle change. There are things that will make this rich to lean change worse. Certain props (like the L/H 4.4D X 4 P) seem to lean out more throughout the run. The APC 4.75D X 4P on the other hand is a fairly steady running prop as is the Top Flite 5-1/4"D X 4P nylon prop. Other things like high compression make the engine rich to lean running more noticeable. The more "sport" (slow speed) the engine runs, the less this rich to lean tendency will be felt. ANY TANK LEAKS make the rich to lean running much more noticeable.

My "Coroplast Trainer" uses a Black Widow, with a TeeDee piston/cylinder that has no SPI. Some
Cox (R/C??) versions just came like that, with no SPI. I use the standard Cox muffler & finds it works really well. Surprisingly well! Best part is that it keeps the grass & dirt out of the exhaust ports, which is very important!
I have tried to "re-produce" this engine & have failed miserably for some reason... Perhaps at the end of the season, when I do an overhaul, I will more closely examine this engine & try to see why it runs so darn steady.  Even today, some cox engines still have me puzzled...

Cheers, Paul

p.s.  I cannot say (with any authority) after a back to back run with, then without a spring in the pick up tube that there is a noticeable difference in the way the engine tank feeds.

tru168 wrote:Hi Paul,
I ran a few tank without spring ,and its lean out too at near the end of tank.
May I know what type of muffler you use? the QRC type, or Cox tether car type? Most of black widow come with SPI cylinder, performance will be greatly reduced if using muffler. did you using cylinder shim to delete the SPI?

For those that don't realize it, a footnote:

The small coil spring in the reedie fuel pickup tube acts as a quasi-fuel filter and is often overlooked as a source of fuel starvation problems. It should be clean and free of obstruction.

SD

Some/most of you will cringe at this... but I have a couple 5cc tanks that I've drilled a 1/4" hole in... installed a rubber grommet for sm. sz. silicone fuel tubing to pass through, attached the line to the backplates' nipple with a little slack when assembled. I can then; run an external tank of my choice. Yes... it's definitely red-neck...

The 1st time I tried this, I had 12+ in. of line hanging out of the tank, which I submerged in a sm. cup of fuel... I opened the needle valve and proceeded to pulse-crank the engine with my elec. starter. The fuel came up the line very quickly.

When the Cox reedie works correctly... by "design" it sucks fuel into the crankcase while running; making it a pretty reliable little engine. Fuel tank placement isn't as much of an issue; compared with rotary-valve designs... just remember to filter your fuel from the can, and use an in-line filter from the tank (if you use an external one). Keep dirt out of the intake air as well. The backplate's venturi screen is adequate... but you can go a step further; by cutting a 1" sq. pc. of polyurethane "air conditioner" filter media between the backplate and firewall... especially if you R.O.G. The polyurethane is impervious to glow fuel... and you've gotta' admit... it's cheap and easy to do. This filter media can also be used as a cushion between your wedge-tank and fuse to dampen vibration that could cause fuel foaming.

I personally; have discarded all of my old "hardened/brittle" vinyl fuel pick-ups with springs; for the sm. sz. "blue" silicone tubing without a spring... I'll admit... I needed therapy, after trying to insert a spring into the sm. sz. blue silicone tubing...

If you like to use an elec. starter; as I occasionally do... squirt a few drops of 3-in-1 oil between the prop-driver and case beforehand, and flip the prop a couple times before you connect the batt. to the plug. If you don't; you "will" eventually cause undue wear to these surfaces from friction/heat.

Roger

I have a 5cc tank that someone has done that before. I also have one that has been swiss cheesed.

Years ago when I ran a Babe Bee.049 in model hydroplane I drilled the 5cc tank to accept fuel line connected to a larger remote tank.

Edit: I ALWAYS use a sping in the pick up tube.

This arrangement extended the hydro's run time considerably.  Worked well for me.   

So it's been done and done successfully.

SD

SuperDave wrote:Years ago when I ran a Babe Bee.049 in model hydroplane I drilled the 5cc tank to accept fuel line connected to a larger remote tank.

Edit: I ALWAYS use a sping in the pick up tube.

This arrangement extended the hydro's run time considerably.  Worked well for me.   

So it's been done and done successfully.

SD

That's interesting about the hydro's run-time SD; as I have a model "outrigger" in the works. Do you have any pics of that hydro? Where did you locate the spring in the line? What type/sz. line and length did you use? What type of external tank was it? Was it an "air boat"... or did you run a flywheel/stuffing-tube arrangement? RC or tethered? (a lot of questions... sorry...) I'd be very interested in knowing more about that model!

Thanks,
Roger

Roger:

Pictures are long gone by now.  The spring/filter was in the standard place (the fuel line just upstream of the NV seat).  The hydro ran a flywheel but no stuffing box (used the lubricant (Vaseline) for that purpose.  (Would use lithium grease now)

Used a rudder to keep it running in a circle (a tether would create drag in the water).  The tank was a rectangular Perfect of 1/3 oz capacity located on the starboard side.

The hydro eventually castor soften the balsa to the point the hydro became too soft to use.  (I have a hydro carcass and hardware here awaiting the day I get "around2it")  Probably never will as my hobby interests have changed.

The hydro was 18" LOA and pretty darn quick on the water. Edit: It was water prop driven.

SD

SuperDave wrote:Roger:

Pictures are long gone by now.  The spring/filter was in the standard place (the fuel line just upstream of the NV seat).  The hydro ran a flywheel but no stuffing box (used the lubricant (Vaseline) for that purpose.  (Would use lithium grease now)

Used a rudder to keep it running in a circle (a tether would create drag in the water).  The tank was a rectangular Perfect of 1/3 oz capacity located on the starboard side.

The hydro eventually castor soften the balsa to the point the hydro became too soft to use.  (I have a hydro carcass and hardware here awaiting the day I get "around2it")  Probably never will as my hobby interests have changed.

The hydro was 18" LOA and pretty darn quick on the water.  Edit:  It was water prop driven.

SD

Thanks much Super Dave! Yea... I figured it may have been a long time ago...

I also have a Dumas "Atlas Van Lines" kit (no longer in production) 1/2 built... since 1994...?

I know exactly what you mean about the "changing hobby interests"...

Roger