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Author Topic: Engine run duration: How big a fuel tanks for Cox .049 Medallion?  (Read 6605 times)

Offline Pat Chewning

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I've got a Cox .049 Medallion engine on a Brodak Baby clown.  I have a Perfect 1/3 oz tank.  I'm only getting 1-1/2 minutes of engine run.

The box says to use a 1/4 oz tank -- that would run even shorter.

The baby-bee is 5cc (1/6 oz) and the black widow is 8cc (1/4 oz), so it appears the fuel tank size might not be the problem.

What actual engine run times do people get for various tank sizes?  I think I must be doing something wrong.
« Last Edit: November 17, 2015, 11:17:36 AM by Pat Chewning »

Offline Dane Martin

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Re: Engine run duration: How big a fuel tanks for Cox .049 Medallion?
« Reply #1 on: November 16, 2015, 10:00:00 AM »
A babe bee should have a 5cc tank. The black widow and such have an 8cc tank.
I believe i get like 1.5 - 2 minutes from 5cc and maybe 3-3.5 sec from the 8cc. I'll have to actually time it.

Offline Fredvon4

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Re: Engine run duration: How big a fuel tanks for Cox .049 Medallion?
« Reply #2 on: November 16, 2015, 03:03:36 PM »
Pat as Dane said the Baby Bee was 5 cc and the black widow style are 8 cc and give two or three minuets run IN THE AIR--- on the ground is a different story because of where the fuel pick up MIGHT be

I suspect the perfect tank, at 1/3 oz, is only running half the tank on the ground....or you have a very thirsty Medallion

Prop it with a rubber ducky 5x3 and set it screaming fast lean then back of just a tad to rich...running say a 6x3 rich will eat a lot more fuel
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Offline Tim Wescott

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Re: Engine run duration: How big a fuel tanks for Cox .049 Medallion?
« Reply #3 on: November 16, 2015, 03:22:44 PM »
I suspect that for stunt a Cox 049 of any stripe is going to be happier with a 6-2 than a 5-3 (and most certainly happier than with a 6-3).

Try and find out -- I certainly like how they do with a 6-2.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Pat Chewning

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Re: Engine run duration: How big a fuel tanks for Cox .049 Medallion?
« Reply #4 on: November 16, 2015, 06:38:14 PM »
The engine run was on the ground and with the airplane tilted so that the tank would suck all of the fuel out (feed line at low point)   BTW:  In the air the plane got 18 laps, which is approx 1.5 minutes of time (at 5 sec/lap)..... [Not timed at all but just counting laps]

So I think it is just extremely thirsty.   I'm going to sub out for a Tee Dee .049 and see if it changes....

Yes, I am running a 6-3 prop which was "pleasant" to fly with other than the duration aspect...

I can't see the fun in doing a full set-up of the plane, lines, and what-not, getting the engine running, and then just flying for 1.5 minutes ....    What tank sizes are ACTUALLY used to do a complete pattern and fun flight?

Offline Fredvon4

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Re: Engine run duration: How big a fuel tanks for Cox .049 Medallion?
« Reply #5 on: November 17, 2015, 08:36:08 AM »
I fly a lot with TeeDee .049, Medallion .049 and Norvel .049s some stock and some modified. Each has various fuel likes and consumption

First answer for longer run is obviously more fuel and since I detest fiddling with very small hard tanks I use balloon or pressure bladders.

So in the Brodak Baby Clown not sure of your options for external tanks (I built mine for a tanked Black Widow) and I am curious how you did the engine mounting for TeeDee/Medallion but that is a side show ( I suspect the easiest way is the screw in radial mount back plate and I use this method on two of my 1/2a birds)

Buying and playing with all the small sized tanks gets tedious as most all of them need opened up to clean out the crap and verify (and fix) where the pipes actually ended up. That said I guess if you have the room just up the tank size to a full 1 oz. This is about the fuel load I put in a balloon or bladder to get around 5 minuets flight time after fiddling on the ground before launch

The TeeDee wants to be tuned and propped to be around 20,000, 21,000 Rpm to be happy and the Medallion some where from 15,000 to 17,000~ this is where they are at peak power and most efficient fuel wise. Stunt runs with the Baby Clown and either of these engines is going to be very fast paced as the Clown is better suited for the reed engine power to keep lap times reasonable. Even then my Black Widow Baby Clown only gets about a 2.5 to 3 min run off the 8 cc stunt tank

This all said I think the 6x3 and rich run is where you are loosing the efficiency of the Medallion and I assure you the TeeDee swapped in will drink more fuel for same setup and be a LOT faster doing it

A 1 Oz balloon tank is supper cheap, easy to use, and weighs less than the same sized tin tank

Most use of my Medallion and TeeDee are on combat planes so fast is what we tune for and I use propellers from 4.2" up to 5.5" and 2.5 to 4.5 pitch

If you are happy with the speed of lap time using the 6x3; keep that set up and just increase the fuel Qty to a full Oz. I have made side of fuselage tanks out of 35mm plastic film canisters.  Most bigger cities have a old skool camera sales and repair store...they have plenty of these canisters usually free for the asking

Poke/drill small holes in the lid and heat with hair dryier then force 1/8th copper tubing for the pick up and vent. Run a bead of RTV in the snap on cap lip after test fitting a few time to orient the pick up to the center rear of outside. I even set these up uniflo and they work very good with the Medallion .49/.051s

Came back to edit this in:

What fuel are you using?  For stunt use I recommend 25%N and 20~22% castor for the medallion, she will run fine on 30%~40%N but not needed for what you are doing.

I say this because I run 25% and 35% and the needle setting is dramatically different effecting run duration.

Another thought is your Medallion cylinder, is it true #2 with single bypass or has a TeeDee cylinder been swapped on with twin byPass?
 Also, which head are you using, stock low compression of higher compression TeeDee trumpet head? I prefer Galbreath adapter and Nelson plugs and play with head shims to get good starting and long plug life with higher Nitro levels

Reason for these thoughts is the TeeDee was developed first to be an all out screamer but starting was a problem for the common sport hobbyist and they created the Medallion to be a lot tamer (but still more powerful than a reed .049).

These are just random thoughts and I understand you are looking for a good smooth stunt run as compared to my max performance reliable restart desires.

Basically what I am saying is there are a lot of combinations for each of these engines that can have a fair effect on efficiency and fuel consumption...  Heads, (Merlin, Galbreath/Nelson, Cox std on High comp, GloBee) Head shims, cylinder shims (timing /compression), pressure or standard tank, piston fit, ball socket fit, crank fit/polish, heavy vs light propeller either in diameter/pitch or materiel, APC= heavy, vs top flight wood = light
Hundreds of combinations all have some degree of impact

I have .35 engines I never fiddled with, just break in and run, rarely changing fuel type or needle setting...Just about every Cox engine I use gets fiddled with a lot finding what I want, or just experimenting

Have fun brother the Baby Clown and good engine is a fun afternoon at the field

« Last Edit: November 17, 2015, 09:21:27 AM by Fredvon4 »
"A good scare teaches more than good advice"

Fred von Gortler IV

Offline Pat Chewning

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Re: Engine run duration: How big a fuel tanks for Cox .049 Medallion?
« Reply #6 on: November 17, 2015, 11:15:33 AM »
OK, 1oz tank it is.   I just find this strange because the integral-tanks are significantly smaller (1/6 and 1/4 oz), and the recommended tank is 1/4 oz ......

And I think I'll search for a 6X2 prop.

PS:  I am using Cox Superpower fuel which is:   
Contains 25% Nitromethane
55% Methanol
10% Synthetic Oil
10% Castor Oil

Offline Fredvon4

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Re: Engine run duration: How big a fuel tanks for Cox .049 Medallion?
« Reply #7 on: November 17, 2015, 11:52:41 AM »
Good fuel we tested it for Hobbico on Cox Engines Forum

APC has 6x2 props

http://www.apcprop.com/category_s/23.htm

I assume you know about cox International for parts and pros etc if not google them same with Exmodel engines
"A good scare teaches more than good advice"

Fred von Gortler IV

Offline Dane Martin

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Re: Engine run duration: How big a fuel tanks for Cox .049 Medallion?
« Reply #8 on: November 17, 2015, 04:24:01 PM »
My tanked reed engines run absolutely great, and 1.5 min is about it for 5cc. If you want to run long enough to do a pattern, bigger tank or bladder is the only way. Fredvon3 is spot on, in my opinion. I also agree with tim on the prop situation. But in my speed planes, its a different story of course

Offline Pat Chewning

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Re: Engine run duration: How big a fuel tanks for Cox .049 Medallion?
« Reply #9 on: November 17, 2015, 10:30:50 PM »
and I am curious how you did the engine mounting for TeeDee/Medallion but that is a side show ( I suspect the easiest way is the screw in radial mount back plate and I use this method on two of my 1/2a birds)

The Cox Medallion/ Baby-Clown mounting is similar to most profile fuselages: Hardwood block beams are set into the profile and ply doublers on each side form a nice sandwich.  The engine is mounted sideways, cylinder to outside of circle, and the needle valve/spray-bar flipped around so the fuel feed is on bottom and needle on top.

Offline Fredvon4

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Re: Engine run duration: How big a fuel tanks for Cox .049 Medallion?
« Reply #10 on: November 18, 2015, 08:05:09 AM »
Pat, that  sounds like how I used to adapt the 1/2a planes for TeeDee .049s before I found Radial adapters at Texas Timers site

Basically a screw in back plate for TeeDee/Medallions with a larger flange ring to screw to the firewall

I like them as they save the weight out front that Maple mounts cause
"A good scare teaches more than good advice"

Fred von Gortler IV


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