Will a EDF be enough to push a Maggie Muggs near 100%?

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Purki
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Will a EDF be enough to push a Maggie Muggs near 100%?

Post by Purki » Tue Apr 07, 2009 5:27 pm

Lets say this in front of a well built maggie mug:

http://www.ejf.com/index.php?main_page= ... a2f6d4c2cf

will there be enough air to push it?

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by larry cottrill » Tue Apr 07, 2009 6:04 pm

Man, if that doesn't do it, I don't know what will!

However, I think you should provide at least a short section of "flow straightener" (just a tube with some vanes running full length), since I'm sure the output of this fan will be heavily twisted around the axis. I'll bet this provides enough air that you could divert a SMALL fraction of it around the outside of the engine for cooling!

Man, if that's something you can afford, go for it! Even if your experiment fails to live up to what you want, you'll have a nice ducted fan you can fly someday on some really nice model.

L Cottrill

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by Purki » Wed Apr 08, 2009 3:57 am

Larry,

Thanks a lot! I have had this idea in my head for months! I want a motor that will fit in small places since I want to make an RC boat with it! I would only need to find parts to make the gas flow be good enough to work with a 1lb propane tank, ramjet+EDF would be about 1.5 feet in length and will have about a 3 inch separation between the jet and the edf. If I take on this project, I hope you could guide me through building the maggie mugg!!

All my best,

Marco

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by Skodasupercar » Wed Apr 08, 2009 8:02 pm

Check out my motorjet in the other section of the forum

Essentially it is a ramjet stuck to the back of one of those.

My fan is a lot less powerful, but still does a hell of a job!

You will need (if it doesn't come with one) a brushless speed controller and some rc gear to get it going, as well as some form of power supply (be that batteries or a big fat transformer).

Lewis

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by Purki » Wed Apr 08, 2009 10:23 pm

Thanks!

I have a gas RC airplane and have some servos laying around, I guess that cuts the maneuver part :lol: but my main priority is just to get this thing rolling!!

Here is a pic of stuff I just bought:

• Two mugs
• Mini Hacksaw
• Strainer
• Some sand paper

Image

I think tonight I will cut the intake mug, I want to take this slow to have something to do this vacation less spring break :)

Also, I will checkout the motorjet Skoda!!

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by Purki » Wed Apr 08, 2009 10:38 pm

GAH!! I think I got the wrong intake mug. It has the handle attached. I might have to fill it in with a screw (cut short) and some JB weld.

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by Purki » Thu Apr 09, 2009 1:30 am

Here is the plan:
Attachments
04-08-09_2041.jpg
Front/Top
04-08-09_2040.jpg
From rear/top
04-08-09_2055.jpg
top view
ramjet.jpg
Showing the dimmensions

larry cottrill
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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by larry cottrill » Thu Apr 09, 2009 10:50 am

What you REALLY need to add is a fairly long conical diffuser in front of that short cylindrical stub. What you have will probably work, but it will be nowhere near as good as you'd have with a real diffuser (I realize that the one shown on the original Maggie was suboptimal). What is often forgotten is that a ramjet gets its operating pressure from the diffuser, NOT from combustion !!! This is especially true in your motorjet, because you will have some really nice velocity going in the front end of your engine, so you COULD actually get decent pressure, IF the right diffuser was put in there.

Of course, what you have is good enough to experiment with and see what kind of performance you get. Don't forget thjat you need cooling air around the outside just as much as air for combustion through the inside!

L Cottrill

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by Purki » Thu Apr 09, 2009 2:04 pm

Thank you Larry,

Can the diffuser and flame holder be "together"? I mean attaching(JB WELD) the diffuser cone on the flame holder or do they HAVE to be separate?

Also, the mug that will go in the back is a "2 layer" mug, steel layers.. I will leave that on and I guess I have myself a cooling layer :P its about 1/4 inch apart from the main CC, Ill post pictures in a while

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by Purki » Thu Apr 09, 2009 11:30 pm

I have decided to make the diffuser cone out of aluminum cans, maybe a two layer to make it a bit stronger. does it HAVE to be round or can it be a triangle?

EDIT: The diffuser would be no longer than 3 inches, I suppose.

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by Purki » Fri Apr 10, 2009 1:49 am

I ran out of options, the soda aluminum is EXTREMELY flexible and weak. even if I do layer it, it wont work

I guess im going with the flameholder for now (first ramjet) and maybe my next to come would use a diffuser

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by larry cottrill » Mon Apr 13, 2009 12:38 pm

Purki -

SORRY! I haven't been paying attention for a few days!

The diffuser could be aluminum, but the can material is VERY thin. Something like aluminum duct for clothes dryers would work. It's about the thickness of a business card, but can still be cut easily with large scissors. It can be hard to glue aluminum -- you should roughen it with sandpaper before applying cement.

You must not consider the diffuser section as something "optional" -- it is the heart of proper ramjet operation! It will be especially important in a motorjet, since the fan makes really high speed air available to you.

I don't really like the "double wall" around the chamber. The trouble will be that it shields the front of the chamber from cooling air! What you ideally want is slow but constant air motion along the outside chamber wall. If you must have the outer wall attached, drill a ring of little holes or oval slots all around where air can get in to flow along the chamber surface. You've GOT to have airflow over the front part of the chamber!

L Cottrill

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by Purki » Mon Apr 13, 2009 7:50 pm

Larry,

I finished the engine and here is what happened:

I turned the gas on and gave it a quick spark, it lit and I started blowing air from far away and bringing it closer and closer slowly (with gas at full power, my gas valve is weak..)The propane tank (1lb) tipped over and liquid propane got in the engine giving it 25%-35% more power than gaseous fuel. Although it gave it this much more power have in mind that I was not using a high power source (shop vac). I get almost no power out of it whatsoever for the bad reasons i posted below.

Here are the good things:

1. lights fast
2. Flame holder works

Bad things:

1. The flame stays in the FRONT and BACK of the flame holder unless I position the air in a certain angle. When the flame are in the front of the flame holder, the power is almost nothing but when I get it to ALL be in the back, I hear and see a power increase.

2. When too much air is "injected" the flame dies.

I think that the flame dies because of lack of fuel?
I also think that the flame stays in the front as well because the strainer has a dime-sized hole on the center? I would weld a dime there with a hole drilled in the center?


My uncle has also let me use his shop/metal to build one (real welding, tubing etc) I was thinking of the CC to being 5 inches long, 3 inches in diameter, and the intake/nozzle be 2.5 inches each going from 3 inches to 2 inches. YES i would have a diffuser this time.

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by larry cottrill » Tue Apr 14, 2009 12:15 pm

Purki wrote: 1. The flame stays in the FRONT and BACK of the flame holder unless I position the air in a certain angle. When the flame are in the front of the flame holder, the power is almost nothing but when I get it to ALL be in the back, I hear and see a power increase.
That is just exactly what should be happening. Inadequate air speed will allow the flame front to move forward, ahead of the flameholder. All ramjets have an operating range of speeds. Too slow, inadequate pressure is developed. Too fast, most of the combustion is wasted behind the engine. Just right, all the combustion takes place right behind the flameholder, and good velocity is developed (the roar is an indication of power development).
2. When too much air is "injected" the flame dies.
I think that the flame dies because of lack of fuel?
Yes, exactly. As you increase air you MUST increase fuel flow so the mixture will remain combustible and the flame will thus remain stable.
I also think that the flame stays in the front as well because the strainer has a dime-sized hole on the center? I would weld a dime there with a hole drilled in the center?
I doubt that it means much. But, it sure wouldn't hurt anything to close that hole.
My uncle has also let me use his shop/metal to build one (real welding, tubing etc) I was thinking of the CC to being 5 inches long, 3 inches in diameter, and the intake/nozzle be 2.5 inches each going from 3 inches to 2 inches. YES i would have a diffuser this time.
Now, you're getting serious! If you're going to do that, instead of using the Maggie pattern, page down this foum just a little, until you get to "Steve's TLAR Ramjet" and study that thread THOROUGHLY. That's the way to do it! You will need a powerful blower and a good fuel supply to make it work!

Good luck!

L Cottrill

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Re: Will a EDF be enough to push a Maggie Muggs near 100%?

Post by Purki » Tue Apr 14, 2009 8:06 pm

I don't haev enough words to thank you Larry!!
I will try running the Maggie M. with alcohol sometime this week, I will keep updating!

I will check out the TLAR!!

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