My Maggie Mugs Clone

[Bobthemonkey]

Hi Everybody, this is my first post so I might make a few mistakes here.
I started making a Maggie Mugs about 3 weeks ago and only now was able to join and post my progress so far. I thought that J-B Weld was not Hi-Temp enough so I am using Resbond™ 907GF Adhesive & Sealant whitch can be found here: http://www.cotronics.com/vo/cotr/ca_putties.htm also I thought that I should block off the holes in the side of the sink strainer to keep the flame from blasting out and burining the epoxy. Here is a picture I took of my ramjet so far, the second one is my diagram.

Replies are greatly appreciated!

Bob

[PyroJoe]

Nice work, can't wait to see the flames.

[Bobthemonkey]

Thanks, I cant either!
I worked on it a little more this weekend and I built the struts and the fuel injection tube. I am almost out of Epoxy and I still need to attach the struts and the fuel tube to the main body. When I am finished I hope to measure the thrust and maybe shoot a video!

By the way this is my first ramjet project so I will probably be sort of messy.

Bob

[larry cottrill]

Bob -

Obviously, the bond you're using isn't as "workable" as J-B Weld, but I agree it's a much better material for the application. I should have done a lot more research on what was available before doing the original project and setting up the construction pages. I like your simple aluminum plate mount struts very much!

Another fairly silly element of the original design is that suboptimal diffuser. I wish I hadn't steered people down that path, and if I had come up with a simple cone of "just right" size I would have used it. But, for the low operating speeds I had in mind (U-control model plane speeds), the stepped design should work. A smooth cone would still be better, though.

What do you have for air? You'll need a heck of a leaf blower or something because the effective flow area of the blower outlet definitely needs to exceed the inlet width, for two reasons: First, you want the air to be as consistent in velocity across the inlet face as possible (and you certainly don't want any roughness of edge flow entering around the rim); and second, you want a decent flow of cooling air all around your engine (out there, turbulence won't matter). Getting the air right is probably the biggest headache for amateur ramjetters, since your choices are usually so limited by what you can spend. Getting a high velocity is just about meaningless if it isn't smooth clear across the inlet face, AND the flow also needs to be aligned right down the centerline!

Good luck! Let's see her howl!

L Cottrill

[Bobthemonkey]

Thanks Larry,
I found out just how unworkable this stuff is when I tried to use it. It literally starts to set in your hands! Actually I find it quite amazing that I have come this far without making a major mistake (I am only 13). As you can probably see from my first attempt at making struts,my work is pretty messy because the epoxy isnt self smothing like J-B Weld, though it is impossible to break once it is fully cured.

For air I thought of using a big shop-vac (the one I have is 5 hp) with a metal tube on the end of the bower tube to prevent the plastic from melting from the heat. I will probably eventully mount it on a R/C airplane, but first it has to run!

I thought of using propane as a fuel for proliminary testing, but if that works then I will move to liquid fuel.

Any Suggestions ANYONE?

Bob

[Bobthemonkey]

I have done a lot more over the weekend
I installed the fuel tube and I glued on the mounts as well and I am almost done! I have completly used up my supply of epoxy, but all I have to do now is put the spark plug in and then I will be done!

Replies are greatly appreciated!

Bob

[larry cottrill]

Bob, I have to hand it to you: It's really looking awfully good!

Since you're interested in a flying model, I'll take the liberty to describe how I was going to accomplish that:

I have an old Olson-Rice .60 cu.in. engine stripped down for glowplug running (i.e. all the ignition stuff is long gone). I was going to put an impeller from a medium-power leaf blower on the front end of this (with a starter pulley), and then have a carved shroud that would surround the impeller with a volute at the front end, routing all the air through and around the cooling fins and out the back where it would taper in slightly to "nozzle" the outflow (exhaust from the engine would be piped outboard so oil wouldn't end up in the forced air flow). Then I was going to mount Maggie a little distance behind this nozzled outlet.

The idea was that the forced air would be enough to get Maggie started before launch and keep her running until the plane was up to speed. Then, the piston mill would run out of fuel, leaving Maggie to carry the whole propulsion load. So, it would be a motorjet to ramjet transition design. This should work because the nozzled cowl would pull air inward from the two sides and blend it with what still gets through around the "dead" engine, due to the ample space in front of Maggie's inlet face. Some experimentation required (maybe some draggy baffles, too).

Of course, you may come up with a better scheme. I even thought of using water rocket boosters for the initial acceleration to speed.

Good luck!

L Cottrill

[Bobthemonkey]

Thanks Larry,

I like your idea, I wasnt really shure how I was going accelerate it in the begining. I think it would be a little bit better to have the motor located inside the main shell of the aircraft and have a chain or a belt going to the propeller as this would produce less drag. It would be great to put on a model aircraft, but I have to get it to run first! By the way, would an argumentor work for my shopvac to improve the effective air outlet size?

Construction is temporaraly on hold because I wasnt able to find a good sparkplug for this. What do you recomend for a sparkplug?

[larry cottrill]

Look for a CM-6 or other 10mm plug. A good hardware store will have M10x1.0 hex nuts to fit it - maybe even stainless. An augmentor for your shop vac will increase the breadth - BUT you will have a lot lower speed airstream. No free lunch from augmentors - ha! Remember that the pressure you develop in your diffuser (and therefore, in the chamber) will depend on the speed of what goes in the inlet.

L Cottrill

[tufty]

For testing, you don't need a sparkplug. A sparkler up the tailpipe[1], burning rag, anything to get a flame. Once it's going, you shouldn't need a plug anyway.

[1] (c) MangyJet, see http://youtube.com/watch?v=MiaAqeeb76g

[Irvine.J]

Tee hee I love that engine, It had the sweetest flameholder... I'll make it in stainless some day... I think I butchered the fuel line for a rossco-jector when we got desperate for copper pipe at some point lol. Rooosssssccccooooo!

[Bobthemonkey]

Thanks for the tip Larry,
I think I am going to go with the sparkplug just to ensure that the flame front is completly behind the flameholder. A sparkler works fine for an engine where the fuel is injected behind the flemeholder, but not for this engine because of where the fuel is injected.

-Bob

[Irvine.J]

Hey bob, my injector was a good several inches in front of the the flame holder too, and the sparkler just randomly half way down the engine. A sparkler is a much more forgiving way of igniting your ramjet, simply, its about 2000 degrees, and fires hot shards of metal everywhere almost guaranteeing ignition. You will find a "sweet spot" with the the sparkler that will allow you to better approximate your sparkplug position.

With the injector infront of the flameholder, its mixing all the way down and through the flameholder, when its through the flame holder, its well mixed and ready to burn, you would never really light a ramjet in front of the flameholder, I don't think it would actually ever light doing that? If you just want to see how it runs, there no shame in a sparkler at all.
Goodluck man its a sweet looking engine.

[Eric]

With the injection system infront of the flame holder you are going to get flames infront of the flame holder no matter what you do. Though the engine doesnt have a true diffuser section where the flow would slow down for it to burn well, its probably going to have quite a bit of flame infront.

Also with the injector pointing to the top wall most of the fuel is going to go upwards. and at low blower speed it could even come out the front of the engine.

Eric

[Bobthemonkey]

Actully, Eric the fuel injector is not pointing twards the top but it has the top blocked off and a series of five holes drilled in it, all pointing twards the rear of the engine. I think I am going to go with a sparkler after all, just because it keeps me from drilling any more holes(I might mess up eventully) and I also dont need a high voltage coil to get the plug running! this is a plus because I was going to just use an old Piezo grill ignitor I got and that doesent always throw a spark and almost never sets things on fire.

-Bob