High performance Integral tanks for Cox engines

Paulgibeault Wed Nov 05, 2014 11:45 pm

Hi Guys.
Those of you following my Vintage speed exploits are aware of my tank modification to uniflow venting.
Here is a photo of a photo where I first saw it some 20 yrs. ago. What your seeing is Master Modeller & top notch racer John McCollum's tank arrangement. John was kind enough to teach me many things about racing & even went so far as to build his entire AMA Class I Mouse race engine from scratch, as a research project. I don't know if John ever held the Open record but I do know he was near impossible to beat in a head to head race. Some of my wins over John were often because his pit man was not as fast in the pits starting & restarting as I was. So John's superior speed was occasionally lost in slower pit stops & pitting accidents in some cases...

1. Here's John's 8cc Silver Bee tank modified with a uniflow vent & very cool spring loaded overflow valve on top

High performance Integral tanks for Cox engines P1070218

Photos 2 and 3 show that very nifty home made spring loaded overflow valve in both open & closed positions. Note: John used a filter cloth over his 1/8" I.D. uniflow pipe as an air filter. John used a 1/8" vent pipe for quick filling. *That man thought of darn near everything!
2.

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3.

High performance Integral tanks for Cox engines P1070220

4. One other rather sneaky mod that John did was to seal up his backplate so that only a hole around the venturi was exposed. Then John drilled a 1/4" hole in the center of his aluminum motor mount plate. That 1/4" hole was then drilled straight through the top outboard nacelle block on the model. I never knew why until ~ 2 yrs ago! The normal engine sucks air through the bottom of the tank backplate. This area is close to the dirty ground & is prone to sucking in dirt & debris. John's model allows his engine to breathe clean air from up on top!!

Cheers, Paul

Theo Kleynhans Thu Nov 06, 2014 1:23 am

Thanks Paul

This is valuable information. Thanks for sharing this with us.

It seems that John was a real expert at this. The overflow system is quite cool.

Theo

Kim Thu Nov 06, 2014 5:54 am

Dude! What Theo Said!!!

Can't lose track of this stuff, so now, I got a "Paul Gibeault Engine File" in my Model Airplane Folder! You definitely got some cool friends also!!!

Thanks for all this great stuff !!!!!!!!!!!!!!

roddie Thu Nov 06, 2014 11:44 am

This might be a dumb question.. but from what you and others have experienced with the conversion of the small tank to uniflow, it would seem to be a worthwhile mod to make for flying c/l stunt.. wouldn't it? Not that the Babe Bee tank will give you a whole lot of time.. but it would be lengthened, due to eliminating the syphon effect. It would also allow extended inverted flight.. without loosing fuel out the vents.

I just re-read (skimmed) the Speed Secrets thread.. for how you blocked the vent on the backplate. I see that one is capped-off.. Is the other one filled with JB? Since the opposite vent has a tube extension for filling/capping-off, I would guess that you haven't had issues with it falling off. Your needle valve seal probably helps here. Would connecting the vents with a piece of fuel tubing work? I realize that this would be added drag on a speed model.. but it could actually add capacity to the tank. It would also be a visual fill indicator. If you fuel through one of the backplate vents while blocking the uniflow with a finger.. the tank will be full when fuel squirts out the open bridge-line. Connect it and fly.. no tiny plug to lose either.

These speed secrets threads have been extremely interesting Paul. Thanks for sharing!

Paulgibeault Thu Nov 06, 2014 12:42 pm

Hi Roger,
I would think you are absolutely right. A uniflow tank mod would make any Cox Integral engine run steadier in all phases of stunt , plus give a longer tank run.
MY way of making the tank uniflow is only one way. I suspect there may be other methods that work also. It definately gives a longer tank run in any event due to no more fuel siphoning.
If you look closely at some of the photos, you will see that I J-B Welded one of the backplate vents closed. My neophrene tube vent did fall off once & I got an off tune engine run. I've since found using a new (stiff) piece of neophrene before every contest seems to be sufficient for the time being...(lazy mans fix). I have seen a piece of tubing used to bridge the vent holes. It can work too. What I'd REALLY like to see is a miniature vent valve to do away with any tubing on top...
Cheers, Paul

roddie wrote:This might be a dumb question.. but from what you and others have experienced with the conversion of the small tank to uniflow, it would seem to be a worthwhile mod to make for flying c/l stunt.. wouldn't it? Not that the Babe Bee tank will give you a whole lot of time.. but it would be lengthened, due to eliminating the syphon effect. It would also allow extended inverted flight.. without loosing fuel out the vents.

I just re-read (skimmed) the Speed Secrets thread.. for how you blocked the vent on the backplate. I see that one is capped-off.. Is the other one filled with JB? Since the opposite vent has a tube extension for filling/capping-off, I would guess that you haven't had issues with it falling off. Your needle valve seal probably helps here. Would connecting the vents with a piece of fuel tubing work? I realize that this would be added drag on a speed model.. but it could actually add capacity to the tank. It would also be a visual fill indicator. If you fuel through one of the backplate vents while blocking the uniflow with a finger.. the tank will be full when fuel squirts out the open bridge-line. Connect it and fly.. no tiny plug to lose either.

These speed secrets threads have been extremely interesting Paul. Thanks for sharing!

roddie Thu Nov 06, 2014 11:08 pm

Paulgibeault wrote:

If you look closely at some of the photos, you will see that I J-B Welded one of the backplate vents closed. My neophrene tube vent did fall off once & I got an off tune engine run. I've since found using a new (stiff) piece of neophrene before every contest seems to be sufficient for the time being...(lazy mans fix). I have seen a piece of tubing used to bridge the vent holes. It can work too. What I'd REALLY like to see is a miniature vent valve to do away with any tubing on top...
Cheers, Paul

I thought a little about a valve.. and came up with this. It's super simple.. and should work.

inner-tube rubber used for a seal.. and pierced in the center with an awl.

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High performance Integral tanks for Cox engines Dsc02116

#2-56 x 3/8"L machine-screw, nut and compression-spring.

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#44 drill-hole (.086") in the top of the tank.. with screw/seal installed from the inside-out using tweezers or needle-nose pliers. Install compression-spring and nut on the outside, for adjustment.

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High performance Integral tanks for Cox engines Dsc02118

shown open..

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and closed..

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High performance Integral tanks for Cox engines

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