From the Editor of
from the Editor of jetZILLA - the Online Magazine of Amateur Jet Propulsion from the Editor of jetZILLA - the Online Magazine of Amateur Jet Propulsion from the Editor of jetZILLA - the Online Magazine of Amateur Jet Propulsion

Maggie Muggs(TM) ramjet engine and designer Larry Cottrill

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The  Maggie MuggsTM  low-speed ramjet project -
August 2003 - TODAY!
(last content update: 08 Mar 2004)

'Maggie Muggs' experimental low-speed ramjet engine (c) 2004 Larry Cottrill
The original Maggie Muggs low-speed ramjet engine


WORK IN PROGRESS LOG
  Preliminary Design
    Concept submitted:   2003-07-10    
    Design complete:   2003-08-07    
  Working Prototype
    Construction started:   2003-08-28    
    Construction completed:   2003-10-03    
    Testing started:   - Not started -    
    Testing completed:   - N/A -        
 


E X P E R I M E N T A L
---   R E A D   T H I S   N O T I C E   ---
In viewing this site, YOU ARE AGREEING TO THE FOLLOWING TERMS AND CONDITIONS:
  1. LIMITED LICENSE IS HEREBY GRANTED TO BUILD AND MODIFY THIS DESIGN IN SINGLE UNITS ONLY, FOR NON-COMMERCIAL PURPOSES ONLY, such as for personal education and amusement, and including use of the design as a powerplant for an unoccupied model vehicle, UNDER THE REMAINING PROVISIONS OF THIS STATEMENT OF TERMS AND CONDITIONS:
  2. PRODUCT DESIGNS SHOWN ON THIS PAGE ARE proposed embodiments of INVENTIONS OF LARRY B COTTRILL, and any or all rights may be assigned to Cottrill Cyclodyne Corporation (a for-profit corporation registered in the State of Iowa, USA);
  3. PRODUCT DESIGNS SHOWN ON THIS PAGE ARE UNDER DEVELOPMENT AND THESE PRODUCTS AND THE UNDERLYING INVENTIONS potentially embodied in such products ARE NOT BEING MARKETED NOR OFFERED FOR SALE, pending completion of development efforts and possible patent application;
  4. NO ORDERS ARE BEING TAKEN for any future products shown or described herein, pending completion of development efforts and possible patent application for the underlying Inventions;
  5. NOTHING in the images or descriptions of proposed future products on this page SHALL BE CONSTRUED TO LIMIT the range of embodied applications for the underlying Inventions, NOR IN ANY WAY TO WARRANT SUCH INVENTIONS or any derivative embodiments as to fitness FOR ANY PARTICULAR PURPOSE;
  6. In showing product information on this page, NO CLAIMS OF ANY KIND ARE MADE in regard to performance, manufacturability, marketability, product safety, or fitness for any particular purpose;
  7. In showing product information on this page, NO LICENSE IS GRANTED to duplicate, re-scale, publish, revise or offer these designs to any party on any basis FOR ANY COMMERCIAL USE;
  8. PUBLIC PRESENTATION OF THIS PAGE and the images and descriptions of these proposed future products SHALL NOT CONSTITUTE ANY WAIVER OF PATENT RIGHTS OR OTHER RIGHTS the Inventor or any licensee or assign thereof may have in relation to these Inventions;
  9. BY VIEWING THIS PAGE, YOU AGREE THAT YOU UNDERSTAND THAT THE BUILDING AND TESTING OF JET ENGINES IS INHERENTLY DANGEROUS TO PROPERTY, LIFE AND LIMB, AND THAT THE DESIGNS SHOWN ARE NOT REPRESENTED AS EXPERIMENTALLY PROVEN DESIGNS;
  10. AND YOU FURTHER AGREE THAT ANY ATTEMPT on your part TO BUILD, TEST, MODIFY AND/OR UTILIZE THE DESIGNS SHOWN IS PERFORMED UNDER CIRCUMSTANCES BEYOND OUR CONTROL, THAT YOU ARE BUILDING AND TESTING THE DESIGNS AT YOUR OWN RISK, AND THAT YOU ARE ASSUMING TOTAL LEGAL RESPONSIBILITY FOR ALL DAMAGES OF EVERY KIND THAT MAY BE INCURRED in such building, testing, modifying and/or utilizing them for any purpose whatsoever; AND THAT YOU AGREE TO HOLD THE DESIGNER AND COTTRILL CYCLODYNE CORPORATION COMPLETELY HARMLESS IN REGARD TO ANY SUCH DAMAGES YOU INCUR, WITHOUT LIMITATION.


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    I.   O R I G I N A L   S C A L E   D R A W I N G
   ______________________________________________________________

Disclosed on Kenneth Moller's Ramjet Forum - 07 August 2003:
    
Scale drawing for 'Maggie Muggs', an experimental low-speed ramjet engine (c) 2003 Larry Cottrill VIEW LARGE
IMAGE
 
LOW-SPEED RAMJET ENGINE - 'Little Maggie Muggs' The scale working drawing, as disclosed on 10 July 2003. The engine is designed to be fabricated entirely from easily available parts and cheap materials, with 100% chemically bonded construction - absolutely no welding required. This engine is now under construction by the author, and is nearing completion. Drawing Copyright 2003 Larry Cottrill



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    II.   W O R K   I N   P R O G R E S S   P H O T O   D I A R Y
   ______________________________________________________________


Photo Diary: How I Built the "Maggie Muggs" Low-Speed
Ramjet Prototype at home in my basement, using
ordinary hand tools and a handful of discount-store
materials, with NO WELDING, for under $60 US - PART I
by Larry Cottrill, Editor, jetZILLA Online Magazine
 
          - All photos this page Copyright 2003 Larry Cottrill - 

Table of Contents [Sections I-IV below]:
I.  The parts lineup [28 August 2003]
II.  The tubular truss engine mounts [28 August 2003]
III.  Building the diffuser section [04 September 2003]
IV.  Bonding the diffuser/flameholder subassembly to
       the combustion chamber/nozzle shell [12 September 2003]

Table of Contents [Sections V-VIII go on to Page 2]
V.  Final major assembly steps [22 September 2003]
VI.  Details, details [22 September 2003]
VII.  Fuel and ignition system work [29 September 2003]
VIII.  Finishing up [03 October 2003]:


I.  The parts lineup [28 August 2003]:
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Parts and materials for 'Maggie Muggs' ramjet engine (c) 2003 Larry Cottrill



II.  The tubular truss engine mounts [28 August 2003]:
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Gluing up an N-strut in my first gluing jig - the opposite strut, 
semi-finished, and the fully cut rails are to the left. The rails
are .5 x .75 x 1/16 inch aluminum angle; the N-struts are cut 
from the .25 OD titanium tubing contributed by my friend 
Mark 'Thixis': 

Gluing up one of the N-struts in the gluing jig (c) 2003 Larry Cottrill


The N-struts resting against a cardboard jig to align them 
properly, with just enough J-B Weld to tack them to the rails: 

N-struts joined to rails, aligned with simple cardboard jig (c) 2003 Larry Cottrill


The finished engine mounts, fully reinforced with J-B Weld - 
left mount in foreground, right mount behind: 

Finished engine mounts - left in foreground, right in background (c) 2003 Larry Cottrill



III.  Building the diffuser section [04 September 2003]:
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Here's a shot of cutting the groove around the mug shell. The mug 
is rotated counterclockwise as seen from the top, with the saw 
oriented as shown [for a left-handed blacksmith, set it all up 
just the opposite way round]. I oiled the hacksaw blade, but 
couldn't tell whether this really helped any - it was slow going:

Cutting the groove around the mug shell, to cut excess length from the diffuser section (c) 2003 Larry Cottrill


I tried starting the cut with the jeweler's saw, but found it 
impossible to get a good starting cut, so I just ended up working 
my way around it with the hacksaw until I knew I'd gotten fully 
through it all around. The piece had to be moved in the vise jaws 
four or five times:

Cutting the diffuser section to final length with the hacksaw (c) 2003 Larry Cottrill


Oddly, the lower part of the shell was not that easy to remove, 
because of the friction of the insulating foam tightly formed 
inside: 

Pulling the fully cut diffuser section off the mug insulation, with some difficulty (c) 2003 Larry Cottrill


Finally, though, it does break free: 

Finally, it breaks free (c) 2003 Larry Cottrill


The edge requires a few minutes of work with a flat file and a 
small half-round file to make it safe to handle: 

Smoothing the sawed edge with a flat file (c) 2003 Larry Cottrill


When I scraped off the non-skid ring attached to the end, I was 
pleasantly surprised to find two little holes, so it was easy to 
thread the jeweler's saw through to get a good start on the cut. 
I just worked my way around, a bit inside the edge of the flat 
end. Again, the piece had to be re-chucked in the vise a few 
times; and, as predicted, I went through 6 or 7 saw blades to get
the whole end cut out. Unfortunately, neither the blade nor the 
progressing saw kerf shows in the picture, since they are about 
the width of a horse hair. It took about 45 minutes of sawing and 
changing blades to complete the cut: 

Cutting out the end of the diffuser section, using the jeweler's saw (c) 2003 Larry Cottrill


Even though the jeweler's saw is capable of accurate work, I 
didn't try for real smoothness or precision. A fairly coarse 
half-round file was perfect for evening up the hole - this only 
took ten minutes or so: 

Evening up the inlet opening with a fairly coarse round file (c) 2003 Larry Cottrill


Then, a much smaller and finer half-round was used to smooth up 
the opening for safe handling and inlet streamlining: 

Final smoothing and streamlining of the inlet, using a fine half-round file (c) 2003 Larry Cottrill


The finished diffuser behind the 'draggy flameholder'. All the 
small parts of the sink basket strainer are removed and discarded.
Note the wonderful array of apertures in this high-quality 
stainless strainer - a near-perfect 'burner grill': 

Finished diffuser shell behind sink strainer 'draggy flameholder' (c) 2003 Larry Cottrill


Both the inside edge of the diffuser [large end] and the entire 
rolled rim of the flameholder have been roughened with sandpaper.
A small bead of J-B Weld has been applied to the INSIDE of the 
diffuser rim. Here, I apply a HEAVY bead of J-B Weld over the 
whole surface of the flameholder rim: 

Applying J-B Weld to the rim of the flameholder before setting the diffuser in place (c) 2003 Larry Cottrill

When the diffuser is inverted and lowered into place on this rim, 
the two beads of cement will blend together to form a smooth, 
strong 'glue fillet' that will lock the pieces together without 
the chance of even the slightest gap, with just the slightest 
bead of J-B Weld visible all around the outside. 



IV.  Bonding the diffuser/flameholder subassembly to 
the combustion chamber/nozzle shell [12 September 2003]:
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There is a significant gap [a couple of millimeters] between the 
OD of the rear of the diffuser assembly and the ID of the front 
edge of the combustor shell. A ring of solid J-B Weld is formed 
around the diffuser rear edge to a depth of about 3/8 inch [about 
8mm] to take up this difference. Believe it or not, the TOP 
inside plastic rim of the Wal-Mart mug looked like just the right
dimensions to work as a mold for this epoxy ring. The trick is to
make sure the J-B Weld sticks to the stainless but not to the 
plastic; so I smeared a thin coating of vegetable oil all over 
the plastic rim internal surfaces. Then, a heavy coating of J-B 
Weld was run around the rear diffuser where the flameholder is 
bonded on, and this is then lowered, flameholder down, into the 
top of the mug. J-B Weld is added by toothpick to finish filling 
the gap, right up past the top of the plastic rim:

Using the plastic top of the Wal-Mart mug to form the epoxy ring at the rear of the diffuser shell (c) 2003 Larry Cottrill


The fingertip is used to smooth out the top edge and remove the 
slight excess. The thin film of J-B Weld left on the outside of 
the diffuser shell is of no consequence:

Smoothing the top of the epoxy ring (c) 2003 Larry Cottrill


After allowing full curing time, the finished molded ring is 
popped out of the mold by wiggling the diffuser [it comes out 
easily] - note the inevitable small air voids; these will be 
individually filled in with J-B Weld during the operation of 
bonding to the combustor shell:

Separating the diffuser from the mold, showing the fully cured epoxy ring (c) 2003 Larry Cottrill


Now the Wal-Mart mug is disassembled, and the top rim of the 
stainless shell is smoothed with a small file to remove slight 
burrs. This is a trial fit of the epoxy ring into the edge of 
the shell. Note the formed ridge of epoxy; the shell slides 
easily over the main body of the ring, but balks at this ridge, 
which will assure that the shell is perfectly aligned with the 
diffuser assembly:

Trial fit of the epoxy ring into the combustor shell (c) 2003 Larry Cottrill

The epoxy ring must be cleaned thoroughly with strong alcohol to 
make sure there is no residue of the cooking oil.


Using medium sandpaper to roughen the inside edge of the shell to 
ensure solid bonding [this area is also de-greased with strong 
alcohol]:

Using sandpaper to roughen the inner rim of the combustor shell before gluing (c) 2003 Larry Cottrill


Finally, the entire outer surface of the epoxy ring is coated with 
J-B Weld and the little voids are all filled in. Then, a HEAVY 
bead of J-B Weld is applied all around the INSIDE of the front 
edge of the shell. The diffuser assembly is inverted and the shell
is lowered into place around it, until it comes to rest on the 
molded ridge. This is the orientation it is left in until the bond
is fully cured. Here, I wipe excess epoxy off the outside with a 
dry paper towel; the residual film will be removed by a little 
fine sanding:

Wiping away excess epoxy after gluing the diffuser assembly into the combustor shell (c) 2003 Larry Cottrill

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Page updated: 29 March 2004

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