Few Quick Questions...

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Irvine.J
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Re: Few Quick Questions...

Post by Irvine.J » Tue Feb 10, 2009 8:12 am

Fterh,
Hey Ft, for your air supply "in the field" consider a petrol powered leaf blow from ebay, you can find some nice little bargains on their.
Alternatively, I have a friend working on gearing a lawn mower or chain saw engine to one of the ducted fans on harbour freight, not a bad idea, he geared the prop on a jet boat up to 30 000 rpm with a minimoto engine, if your keen for some serious testing its just another idea.

Also if you can't find JB weld consider "kneed it" or muffler cement, there should be some at your automotive outlet.
Peace.
Where are you btw? Might help us find some low cost parts for you.
Cheers.
James- Image KEEPING IT REAL SINCE 1982
http://pulseairdefence.com
[url=callto://project42labs]Image[/url]

fterh
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Re: Few Quick Questions...

Post by fterh » Tue Feb 10, 2009 9:52 am

Irvine.J wrote:Fterh,
Hey Ft, for your air supply "in the field" consider a petrol powered leaf blow from ebay, you can find some nice little bargains on their.
Alternatively, I have a friend working on gearing a lawn mower or chain saw engine to one of the ducted fans on harbour freight, not a bad idea, he geared the prop on a jet boat up to 30 000 rpm with a minimoto engine, if your keen for some serious testing its just another idea.

Also if you can't find JB weld consider "kneed it" or muffler cement, there should be some at your automotive outlet.
Peace.
Where are you btw? Might help us find some low cost parts for you.
Cheers.
Petrol powered? My parents wouldn't allow, haha, they would say it's a waste of money. I'm in Singapore, thought I mentioned already? :D

Btw can you help with my 2nd question about the size of the stainless steel mugs :(

Irvine.J
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Re: Few Quick Questions...

Post by Irvine.J » Tue Feb 10, 2009 11:13 am

Sorry I must have missed your location earlier, singapore eh, I have friends there that fly for singapore air :)

Mate I haven't built a maggie mugs, i'm sure larry will help you answer that Q, however i'd still suggest some kind of muffler glue anyway.
You need some hard core air, other then a power blower I'm not sure where your going to find something unless you make it yourself, i'll do some scrounging around see if I can't find you something on the cheap.
James- Image KEEPING IT REAL SINCE 1982
http://pulseairdefence.com
[url=callto://project42labs]Image[/url]

fterh
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Re: Few Quick Questions...

Post by fterh » Tue Feb 10, 2009 11:46 am

Irvine.J wrote:Sorry I must have missed your location earlier, singapore eh, I have friends there that fly for singapore air :)

Mate I haven't built a maggie mugs, i'm sure larry will help you answer that Q, however i'd still suggest some kind of muffler glue anyway.
You need some hard core air, other then a power blower I'm not sure where your going to find something unless you make it yourself, i'll do some scrounging around see if I can't find you something on the cheap.
You mean they work for Singapore Air? :D

Hm this is why I want to live in countries like USA, you have your own backyard to try things like this. Well I hope I can use a Vacuum cleaner or what at a multi-purpose hall near my house, hope they have power points there and hope it won't be too loud :(

I've already ordered my JB weld from ebay, is that muffler glue?

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Re: Few Quick Questions...

Post by Irvine.J » Tue Feb 10, 2009 12:03 pm

You mean they work for Singapore Air? (They are pilots, yes) Are you nit picking? :P

Yes mate JB weld is ideal, exactly what you need.
A vacuum cleaner...hmm will be worth a try I suppose, its been years since I used mine in reverse, but I wouldn't expect much, it might have just enough to lock the flame in behind the flameholder so you can experience a bit of the sound and flame... you really need something that can push some air...
James- Image KEEPING IT REAL SINCE 1982
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phonedzero
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Re: Few Quick Questions...

Post by phonedzero » Tue Feb 10, 2009 12:48 pm

fterh wrote:Guys,

how do u ensure that the two stainless steel mugs, after cutting out the unnecessary portions will fit smoothly (like shown here: http://www.cottrillcyclodyne.com/Maggie ... aggie.html) How do u ensure that one of the mugs won't be like, much too big then the other?

:?: :?: :?:
Take your calipers to the store, I did! Just picture a guy standing in a Wal-Mart aisle measuring steel cups! Took me about 20 minutes to find the perfect pairing! But the results were awesome!

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Re: Few Quick Questions...

Post by larry cottrill » Tue Feb 10, 2009 12:51 pm

fterh -

I just used J-B Weld because it was highly workable and I was used to using epoxy type products. It is NOT the best for heat resistance, it softens when things get really hot. What you really need is a small "muffler repair kit" from a hardware shop or automotive supplies shop.

As far as getting pieces to fit, they need to be chosen to be pretty near the same diameter where they fit together. What I did (you can see it in Part IV of the first Maggie Construction Page) is I used the plastic rim of the tall mug as a mold to build up the epoxy around the rear edge of the diffuser where it joins on to the flameholder. This ended up being several mm thick all around, as you can see in the shot where I pulled it out of the plastic rim. That was enough of an enlargement that if pretty well fit the large rim of the tall mug after the plastic rim was removed. I don't know how effective the pictures are in showing this.

In a muffler repair kit, there's some kind of "fabric" that you can saturate with the glue and wind it around to build up a thick ring until it will fit the larger mug. If you get it a little too big, after it hardens you should be able to file it back to fit. Basically, you just have to do whatever it takes to get the right fit, and rely on the thick glue to fill any slight gap that remains. Of course, choosing your mugs carefully in the first place can save a lot of "gap filling".

L Cottrill
Attachments
Maggie_diffuser_gluing_crop1.jpg
First, the flameholder is glued to the rear edge of the small mug (diffuser cone).
Photo Copyright 2003 Larry Cottrill
Ring_forming_crop1.jpg
Forming the epoxy "ring" around the rear edge of the diffuser, after the
flameholder glue is hardened. Photo Copyright 2003 Larry Cottrill
Ring_separating_crop1.jpg
Separating the ring from the plastic mug rim "mold".
Photo Copyright 2003 Larry Cottrill
Ring_fitting_crop1.jpg
Testing the fit of the epoxy ring in the large mug (chamber/tailpipe).
Note that the plastic rim/handle has now been removed.
Photo Copyright 2003 Larry Cottrill

phonedzero
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Re: Few Quick Questions...

Post by phonedzero » Tue Feb 10, 2009 1:05 pm

If I can offer one suggestion, go with the JB. I used muffler cement for my Maggie, I takes the heat well but its is so so brittle. When it cures it expands and forms tiny little air bubbles and it's surface adhesion characteristcs are poor. but the upside is if you don't mind rebuilding it after every couple of runs, the muffler cement cure so quickly, that youy can literally rebuild it in a matter of an hour or so! Use the oven at 350 deg F, and use a dremel or like tool to grind off the expanded cement, back in buisness! I am going to mix JB and muffler cement together and see how it cures, see how it holds up! Here is my first Maggie running this past weekend, using just cement!

http://www.youtube.com/watch?v=_opm6e7U ... re=related

fterh
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Re: Few Quick Questions...

Post by fterh » Wed Feb 11, 2009 6:37 am

Irvine.J wrote:You mean they work for Singapore Air? (They are pilots, yes) Are you nit picking? :P

Yes mate JB weld is ideal, exactly what you need.
A vacuum cleaner...hmm will be worth a try I suppose, its been years since I used mine in reverse, but I wouldn't expect much, it might have just enough to lock the flame in behind the flameholder so you can experience a bit of the sound and flame... you really need something that can push some air...
What is nit picking? :shock:

fterh
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Re: Few Quick Questions...

Post by fterh » Wed Feb 11, 2009 6:40 am

larry cottrill wrote:fterh -

I just used J-B Weld because it was highly workable and I was used to using epoxy type products. It is NOT the best for heat resistance, it softens when things get really hot. What you really need is a small "muffler repair kit" from a hardware shop or automotive supplies shop.

As far as getting pieces to fit, they need to be chosen to be pretty near the same diameter where they fit together. What I did (you can see it in Part IV of the first Maggie Construction Page) is I used the plastic rim of the tall mug as a mold to build up the epoxy around the rear edge of the diffuser where it joins on to the flameholder. This ended up being several mm thick all around, as you can see in the shot where I pulled it out of the plastic rim. That was enough of an enlargement that if pretty well fit the large rim of the tall mug after the plastic rim was removed. I don't know how effective the pictures are in showing this.

In a muffler repair kit, there's some kind of "fabric" that you can saturate with the glue and wind it around to build up a thick ring until it will fit the larger mug. If you get it a little too big, after it hardens you should be able to file it back to fit. Basically, you just have to do whatever it takes to get the right fit, and rely on the thick glue to fill any slight gap that remains. Of course, choosing your mugs carefully in the first place can save a lot of "gap filling".

L Cottrill
Hi thanks for the tip, so I guess I should imagine the dimensions after cutting and "fit" it to the other mug in the store before buying, yeah? :D

By the way, for the flameholder, which direction should it be if the air is blown from left to right? [ or ] ?

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Re: Few Quick Questions...

Post by larry cottrill » Wed Feb 11, 2009 4:09 pm

fterh wrote:Hi thanks for the tip, so I guess I should imagine the dimensions after cutting and "fit" it to the other mug in the store before buying, yeah? :D
Exactly!
By the way, for the flameholder, which direction should it be if the air is blown from left to right? [ or ] ?
See attached, though it is only shown as a hidden line (dashed line). (I see I provided the dimensions in inches only on this one. Rats.) Note that some builders have attempted to seal up the long slotted holes around the outer wall of the strainer, which would be draggier but would probably help the front of the chamber to stay a little cooler.

L Cottrill
Attachments
Maggie_side_view.png
Maggie Muggs side view plan. Drawing Copyright 2003 Larry Cottrill

phonedzero
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Re: Few Quick Questions...

Post by phonedzero » Wed Feb 11, 2009 7:14 pm

I had to cut all the side holes on my strainer away to make it fit within the body properly, the only thing left was basically just the bottom disc with about an 1/8inch lip to connect to my diffuser! And seems to me I also inverted it to use the taper on the body of the strainer to assist in maintaining a tight seal. Thinking back, i think the only part of the build that I ended up staying true to was, the basic OAL of the jet, and the approx depth of the flame holder!

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Re: Few Quick Questions...

Post by larry cottrill » Wed Feb 11, 2009 8:05 pm

Should be OK -- no two Maggies are ever the same!

Since it's a "just for fun" engine, the fine points don't matter too much. All you're doing with Maggie is learning the basic parts and how they work together, and making some heat and noise.

Go for it!

L Cottrill

fterh
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Re: Few Quick Questions...

Post by fterh » Fri Feb 13, 2009 7:33 am

larry cottrill wrote:
fterh wrote:Hi thanks for the tip, so I guess I should imagine the dimensions after cutting and "fit" it to the other mug in the store before buying, yeah? :D
Exactly!
By the way, for the flameholder, which direction should it be if the air is blown from left to right? [ or ] ?
See attached, though it is only shown as a hidden line (dashed line). (I see I provided the dimensions in inches only on this one. Rats.) Note that some builders have attempted to seal up the long slotted holes around the outer wall of the strainer, which would be draggier but would probably help the front of the chamber to stay a little cooler.

L Cottrill
Eh at http://pulse-jets.com/ramjet/ramjet.htm it shows that the flameholder should be [, conflicting with your attached document (which states it should be ] direction)

fterh
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Re: Few Quick Questions...

Post by fterh » Fri Feb 13, 2009 7:36 am

Guys I got an idea. Is it possible to have a powerful fan that forces air in, and one it starts the fan will keep on spinning (faster and faster every second) due to the thrust? What I plan to do is:

Have a long heat-resistant rod to go through the center of the ramjet, connecting two fans: One to blast air in and one at the back (obviously it gotta be heat-resistant). Run the fan off a battery until the ramjet starts, once it starts up the battery can be disconnected. Air will enter the ramjet at x velocity and exit at x+y velocity (due to the fuel exploding and creating a faster-velocity stream of air). The x+y velocity thrust will spin the fan at the back which will in turn increase the RPM of the one in front (because they're connected by the rod).

Will it work?

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