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مُساهمة من طرف Admin في السبت فبراير 28, 2015 12:26 pm

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II. The tubular truss engine mounts [28 August 2003]:
[size=10]Previous section
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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': 



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



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




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:



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:



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



Finally, though, it does break free: 



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



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: 



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: 



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



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': 



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: 


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:



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:



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:



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:


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]:



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:
[/size]




The mounts are secured, accurately aligned, to a piece of flat 
scrap wood, using 1/4-20 hex head bolts & washers, with 'tee nuts'
underneath. 


Forming the streamlining fillet at the front edge of the 
combustor shell. This is along the bottom side, before the little 
hole was filed into being a slot:



Here's a fine shot of Maggie, basically assembled, but before 
drilling out for the fuel pipe & spark plug:




VI. Details, details [22 September 2003]:
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The flattened and kinked end of the pressure tube. This part will 
protrude slightly beyond the inside wall of the large part of the 
diffuser, so the cut end will lie along the presumed flow path. 
The tubing is 1/4-inch OD brass. The flattening is to limit 
leakage from the diffuser shell when a gauge is not attached; 
only a trickle of air is needed to pressurize the gauge.



The hole that used to hold the bottom end of the mug handle is 
lengthened into a slot, using a Heller needle file. The slot is 
cut in line with rearward airflow, but is slanted to one side for 
the flattened tube end:



Preparing to test fit the flattened end of the pressure tube. 
This shows approximately the final orientation and location -- 
the outer end of the tube extends forward and down, out through 
the lower space in the left-side N-strut:



Because of the thinness of the shell, the spark plug hole was 
drilled small and filed out with another of the Heller miniature 
files. This one is similar to a half-round, except that both 
sides are round but ground to two different radii:



The bottom side of the engine, showing the fully bonded engine 
mounts and pressure gauge tube, with the spark plug temporarily 
mounted [exact location of the plug is not critical]:



The fuel pipe mounting will be cut from a standard 1/4-inch 
stainless tubing fitting. First, the fitting is drilled out 1/4-
inch ID all the way through, so the tube can pass clear through 
it into the intake:



The hardest saw cut in the entire project: Cutting off the bottom 
[pipe thread] end of the fitting. I finally bought a new hacksaw 
blade, and the work went MUCH faster. This will leave the machine-
thread part of the fitting to protrude through the hole in the 
shell from the inside, with a thin, hexagonal flange for bonding. 
The cut surface will be filed smooth, and the hole edge chamfered 
for smooth passage of the fuel pipe:




VII. Fuel and ignition system work [29 September 2003]:
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The spark plug ready to mount in the combustor shell. The box-end
wrench is fitted with a short piece of masking tape to hold the
plug mount nut up at the wrench surface, making it easy to get it
into place inside the hole so the plug can simply be threaded in.
The electrical lug is filed out to fit the plug; it not only acts
as the spark plug washer, but as a contact for the ground side of
the high-voltage ignition system during starting.



Parts of the fuel pipe mount, after cutting and filing - from the
left: the outer bonnet nut, slip ring, collet, finished mount stud,
and the cut-off end [pipe-threaded end, to be discarded].



The fuel pipe mount stud ready to mount. The stud will pass through
the hole from the inside. Above it is the Heller needle file used
to bring the hole out just large enough for the stud to pass through.



Using the full length of the raw 1/4-inch brass tube to hold the
pipe mount stud in alignment as we wait for the J-B Weld to harden:



Inside view of the finished fuel pipe mount, in place. You can
just make out the smooth fillet of J-B Weld all around the hex
flange that forms the base of the mount:



Outside view of the finished fuel pipe mount, fully filleted in
with J-B Weld:



The first fuel pipe shown in place in the fuel pipe mount. It is
made from 1/4-inch brass tubing, and is nothing but a simple tube
with the end plugged with a dollop of J-B Weld, and a 1/16-inch
hole drilled clear through, just behind the plug. This very simple
pipe should be suitable for propane testing, using an external 
valve to regulate the flow; the liquid-fuel tube will have its own
needle valve permanently attached to the external end of the tube.



The engine so far, along with the tools used in mounting the plug.
A six-point socket, as shown here, should be used around the plug
body, to prevent slipping off and breaking the porcelain insulator.
The tape can still be seen attached to the 12-point box-end wrench
used to reach inside the engine to hold the plug mount nut. Also
shown is the soon-to-be modified Super Tigre needle valve assembly,
which at $18.00 US turned out to be the most expensive single part 
of the entire engine.



The jeweler's saw turned out to be an easy way to remove the short,
cylindrical ring at the tail end of the engine. Once the cut was
started, it was worked all the way around, keeping fairly close to
the rolled zone [about 3/8 inch forward of the rim].



Finally, a decent shot of the jeweler's saw in action! Cutting off 
the short machined inner end of the Super Tigre needle valve body:




VIII. Finishing up [03 October 2003]:
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The parts of the fuel tube [liquid fuel version]: The main tube is
3/16-inch OD brass tubing, the shoulder tube is 1/4-inch tubing.
The tiny part to the left of the main needle valve body is the 
small machined end that was being removed in the previous photo;
it will be discarded. The needle valve entrance pipe and main 
valve body have been 'ported' out with a jeweler's drill to an
approximately .055 inch ID.



The fully finished fuel pipe for liquid fuels. The thin film of
J-B Weld at the left end of the shoulder pipe will be easily 
cleaned up with a few strokes of fine sandpaper.



The fuel pipe going into the pipe mount. The bonnet nut is slid on,
followed by the properly-oriented slip ring and the collet. Then
the whole assembly is inserted into the mount and slid in until the
metering holes at the far end of the pipe are perfectly centered in
the intake opening.



The new fuel pipe fully installed, just after tightening up with an
adjustable wrench. It is not necessary to tighten the nut 
excessively; just enough to keep the pipe from rotating as the
needle valve is adjusted.



The cut end of the exhaust nozzle is smoothed up with a good-sized 
half-round file ...


... and finished with a smaller one:



The end result is a smooth opening with just enough 'rolled edge'
left intact to strengthen the rim:



Maggie Muggs, finished at last - finished weight 10.6 ounces [0.66 pound]:




[/COLOR]




توقيع mahamed125





  

 24-12-2008, 10:28 AM  #3



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الملف الشخصي
















شكرت مرة واحدة في مشاركة واحدة




 رد: واخيرا صنع محرك نفات بمواد متواجدة




[size]


[COLOR="]standard 'shop vac', and it seems to work well enough: 



When more airflow and/or less fuel flow is applied, the flame starts 
to look somewhat better - we're moving towards "lean" combustion:



Continuing to lean out the burn. It looks like there's enough flame 
and noise at this point that the test run is beginning to draw a 
crowd. The mug parts were from teachers that were willing to donate 
their used coffee mugs to the project, so these parts aren't exactly 
like the ones shown in the plans; note, however, how Ben chose a mug 
shell that has a well-developed combustion chamber zone and a good 
long, smooth cone for the tail section - exactly the right approach!



Leaning out the combustion even more makes the flame much less 
visible, but significantly louder [note that the unlookers are starting 
to back off a little!]. The sink strainer flameholder is one of the few 
parts that had to be purchased new for the project; it keeps the 
flame back in the tail section where we need it [unfortunately, the 
flameholder can't be seen in any of these photos]:



Once you get a really good lean run, the noise is a pretty intense 
'jet noise' roar, and in daylight the visible flame almost disappears. 
This is exactly the way your jet ought to be running. However, this is 
also a very hot way to run, and the epoxy construction can't be 
expected to take this for too long:
[
[/size]

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