J.
SHEET METAL MODIFICATIONS
The following
represents some possible modifications that you may wish to do
to your grill. The end result is a grill that is more
efficient in most cases and can over time substantially lower
your cost per pound on coffee, and extend the life of your
components. These mods are entirely optional but I don't
regret for one second the decisions.
As an example,
after completing my first 6Lb assembly, I noticed that I had to
run the burners at 100% to maintain 550 degrees.
With a 4 pound roast you will want to run about 545 F at least
through first crack and then perhaps back off just a bit.
Well imagine the
savings I experienced after modifying the rear vent and capping
off the dome. As a result, I was able to maintain
temperature at only 40% gas. That translates to 60% more
roasts on each tank. That is HUGE.
Similarly, on
this model, used for illustrations. 100% gas netted 550 F,
and after this rear vent mod, We achieved 600F at 33% gas.
So the efficiency increase is, well, astronomical.
Granted,
everyone has a different way of doing things, someone out there
will tell you that not venting the heat/smoke/moisture as
quickly will change your roast. Perhaps, do what you like,
that's why coffee is such an art, a million ways to do anything.
However, my
costs have dropped tremendously and not one complaint from one
customer.
So these are the
mods we have done, others will have other mods. Share
yours in the forum! Try these if you want to! With
that aside, lets get on to
"Fun with Sheet
Metal".
WARNING:
Sheet Metal will cut you open in a flat second. Use gloves
and be aware that it will get you. I know better, I've
done it many times, I'm experienced in Aircraft repair and
construction with sheet metal, aluminum. I told myself,
"Be careful, you could get cut". Guess what, yep, I got
cut....during the assembly of this nice machine. Be
careful, don't work aggressively with this stuff, you push or
shove and slip, you'll be getting stitches. Be firm,
gentle, careful, plan your actions and movements and don't swing
or hammer wildly at this stuff, you slip and it gets you.
Step 14.
Rear Vent Blocking.
(Figure
98)
During our roast
this is where the vast majority of your heat will escape off to.
If we seal this off, then a great deal of our heat will remain
trapped in the grill case and we can effectively lower our
burners substantially. This and the dome capping represent
the greatest efficiency increases you can make.
(Figure 98).
(Figure
99)
This is a piece
of Zinc Plated Aluminum picked up at Home Depot, I think it was
$7 as of early 2009. This is enough sheet metal for the
rear vent and the motor shield, but not for the dome cap.
Get an extra piece if you need to cap the dome. We'll get
to that later. (Figure 99).
Figure
100)
Here's the
details for those who want to know exactly what I'm using.
(Figure 100).
(Figure
101)
I'll go ahead
and measure my rear vent.
(Figure 101).
(Figure
102)
A bit hard to
see in this picture but it looks like 26.5 inches.
(Figure 102).
(Figure
103)
As a rough rule
of thumb, I like to block off 80% or 90% of my rear vent.
In this example, I'll use 80%. 80% of 26.5 is 21.2 inches.
I'll just round off to 21 inches (close enough).
(Figure 103).
(Figure
104)
This part gets a
little interesting, you need to think about how your grill hood
or base works. This one is not a one size fits all mod.
For example, on one grill, the hood hinged up nicely, so I was
able to attach the sheet metal to the hood and when you closed
the lid, the sheet metal presses itself against the base and
seals off 80% of the vent. In this grill design the hood
works differently. I will attach the sheet metal to the
base of the grill and when the lid is closed, the lid will press
up against the sheet metal sealing it off. You will have
to study your grill and see how best to do it.
So the plan here
is, we need approx. 4 inches of sheet metal, we will drill 4
holes in the base to screw the metal to the outside, bend a
flange in the top rearward so that when the grill closes the lid
pushes up against the sheet metal blocking our vent. We'll
take a better look at that as we move forward.
For this
example, you see my measurement of 4" will completely close off
this vent (vertically). So we need a 21" X 4" piece of
sheet metal (Figure 104).
(Figure
105)
Wow, do I need
to find my square.....ok, so 21" and we'll use this piece of
metal as a straight edge.
(Figure 105).
(Figure
106)
Mark your line
at 21" (Figure 106).
(Figure
107)
There's my line
at 21". (Figure 107).
(Figure
108)
Measure down 4"
square it up and draw another line.
(Figure 108 & 109).
(Figure
109)
(Figure
110)
Wish I had some
sheet metal cutters. Oh well, tin snips it is. See
we can do all of this at home, without professional equipment.
(Figure 110)
(Figure
111)
Here's my 4 X 21
sheet and the 4 screws/nuts I'm going to use to mount it to the
grill. (Figure 111)
(Figure
112)
I'm going to use
my metal sheet and a piece of wood to bend the metal cleanly to
create my flange that will press up against the hood when
closed. (Figure 112)
(Figure
113)
Here we are
after the bend. (Figure 113)
(Figure
115)
Here we'll mark
4 equidistant points for our screw holes.
(Figure 115)
(Figure
116)
Hey! Who stole
my center punch??? A big nail will have to do. We'll
mark four points for our drill bit .
(Figure 116)
(Figure
117)
And to the
drill. (Figure 117)
(Figure
118)
Here is my 4
holes, one of those is where I accidentally center punched.
(Figure 118)
(Figure
119)
Visually, center
the shield on the back of the grill, I used finer widths at the
sides. You see we will now have a relatively small area
for heat escape. Use a pencil to mark the spots for the
drill holes. (Figure 119)
(Figure
120)
Center punch
your marked circles. (Figure
120)
(Figure
118)
Here, I'm going
to just make a mark with my drill and verify that everything
lines up (Figure 118)
(Figure
119)
After all 4
holes are started inthe grill, I hold my sheet metal up to the
grill and verify that I can indeed see my mark through each of
the 4 holes.
(Figure 119)
(Figure
120)
Here are my 4
holes, ready for assembly.
(Figure 120)
(Figure
121)
Screws in the
back.... (Figure
121)
(Figure
122)
Nuts on the
front... (almost sounds like a joke, doesn't it)
(Figure 122)
(Figure
123)
Tighten
everything down, here is what it looks like. You can
clean up some of these bends with vise grips on the bend, and a
file if you choose.
(Figure 123)
(Figure
124)
Here's a view
from the inside with the door closed.
(Figure 124)
(Figure
125)
And one more,
see how it pretty well seals off the back? It will do a little
better when fully closed, how do you think I took the picture?
(Figure 125)
( Also a safety tip. The
vents in the grill are designed to keep the grill at a safe
operating temperature, thus, if you do choose to restrict the
vent, then operating the grill for extended periods of time at
highest heat, could overtemp the entire rig. Please do not
forget that you have left your burners on high and go and do
something else. We don't want any fires)
**END OF SECTION**
MOTOR SHIELD
(Figure
126)
We'll start the
motor shield by taking the remaining section of sheet metal we
have left from the original single piece. Let's make sure
that it will be wide enough to shield the motor assembly from
any escaping heat. You see the metal is at least as wide
as the motor assembly. That should do just fine.
While I have it here, I'm going to mark to the left and right
side of the rotisserie, about 1/2" on both sides. Making a
slot so to speak, 1 inch wide, 3" or 4" high, doesn't really
matter much at this point.
(Figure 126)
(Figure
127)
Lets do a rough
cutout, that top section is a bit tough, no problem, we'll file
it later. (Figure 127)
(Figure
128)
Let's hold it up
on the grill, make sure we're in the ballpark.
(Figure 128)
(Figure
129)
Go ahead and
just cut the corners off, this will allow opening and closing
without interference.
(Figure 129)
(Figure
130)
And we'll trim
off the top, we'll be a little flexible, and go longer than
necessary, we can always cut off, but we can't put it back
together! (Figure 130)
(Figure
131)
And lets just
check again, now look at the front of the grill, where we have
that big obnoxious corner just waiting to cut someone.
(Figure 131)
(Figure
132)
Let's use the
tin snips and rough that out, just like scissors, round it off.
(Figure 132)
(Figure
133)
Looking a little
nicer. Went ahead and trimmed up the other corners too,
just to avoid any accidental injuries.
(Figure 133)
(Figure
134)
Using my pencil
I am going to find 4 spots, preferably in each corner.
Look behind the sheet metal and look for 4 spots that, are in
relatively flat spots on the grill hood. Try to keep the
marks in the corners to offer the most support and keep the
shield from accidentally getting bent. We are getting
ready to drill holes where the marks are, and insert bolts and
nuts. NOTE: Also remember the shield should
stay with the hood, so keep the holes/marks on the hood and not
the grill base. (Figure
134)
(Figure
135)
Using my
center-nail (I mean center punch), lets dent the metal under
each mark, so the drill bit doesn't walk around.
(Figure 135)
(Figure
136)
There is where
I'll drill. (Figure 136)
(Figure
137)
And the drill
again. (Figure 137)
(Figure
138)
Looking better!.
(Figure 138)
(Figure
139)
OK, hold it up,
now it's important here we get this right, hold it perfectly in
position, exactly where you want it to be. Make sure your
rod, clears your shield. Take your pencil and mark the
position on the grill, in the holes. This is where we will
drill on the grill.
(Figure 139)
(Figure
140)
Center Punch
your 4 marks. (Figure
140)
(Figure
141)
And Drill.....
(Figure 141)
(Figure
142)
Here's my four
bolt holes, now were ready to clean up the shield.
(Figure 142)
(Figure
143)
Just to be sure
make sure our holes lines up correctly. NOTE: At
this point before we put it on, use a metal file and file any
sharp points or edges, get it cleaned up so you can't get cut on
it and we're ready to mount it. If you don't have a metal file,
I've actually used the concrete driveway in times past to file it down
if you find yourself without one :).(Figure
143)
(Figure
144)
Here's the
hardware I will use. 4 two inch bolts or so, and 12 nuts,
three per bolt. You'll see why that many are necessary.
(Figure 144)
(Figure
145)
Insert the bolts
into each hole, (the threads towards the grill) run a nut all
the way to the metal and tighten, we want this part solid.
(Figure 145)
(Figure
146)
Here's all 4
bolts with 1 nut each.
(Figure 146)
(Figure
147)
Now, lets run
another nut onto the end of each bolt, say about 3/8" onto the
bolt (like shown).
(Figure 147)
(Figure
148)
Here's where we
should be now. (Figure
148)
(Figure
149)
Mount your
shield up on the grill. See if your bolts line up.
The beauty with the threaded bolts are that you can adjust the
height of each bolt based on the contour of the grill.
Adjust the nuts until the shield sits nice and even.
(Figure 149)
(Figure
150)
Here's the
inside view, some bolts will be longer than others, this is OK.
(Figure 150)
(Figure
151)
Tighten the
shield down to the grill.
(Figure 151)
(Figure
152)
There you have
it, opened........
(Figure 152)
(Figure
153)
And
closed.......make sure there is no interference.
(Figure 153)
(Figure
154)
Look closely, if
there is a problem this is where it will be.
(Figure 154)
(Figure
155)
Another view.
(Figure 155)
(Figure
156)
Finished......
(Figure 156)
(Figure
157)
Finished......
(Figure 157)
(Figure
158)
And.....finished......
(Figure 158)
(Figure
159)
This triple
burner beauty is done, it has an included thermometer and no
need for a dome cap, so we won't do anymore to this roaster.
(This roaster was built for Craig Jensen of Hammond, LA-Thanks
Craig) (Figure 159)
DOME CAP
(Figure
160)
This grill has a
high dome and there is a cavernous space above the drum.
All your heat concentrates here. You are basically paying
to heat an area that your drum and coffee see no benefit from.
Capping this area off will increase efficiency, decrease heat up
times and lower gas consumption. It focuses heat on the
coffee and not just heating empty space.
(Figure 160)
(Figure
161)
Here I basically
cut this sheet metal to size, crammed it up in there and we are
going to simply use a screw and a nut to hold it in place.
(Figure 161)
(Figure
162)
Picture is worth
1000 words.... (Figure 162)
(Figure
163)
And the outside.
That's it, pretty simple, this whole mod took less than 15
minutes to complete. (Figure
163)
THERMOMETER SHIELD
(Figure 164)
Here is the
normal thermometer installation. Notice that the probe is
completely exposed. On some grills, with a horizontal
diffuser (Figure 165),the
heat column from the burner rises straight up the internal front
face of the grill and hits the temperature probe head on.
This causes wild, uncontrollable fluctuations in temperature.
If your probe is already shielded by your diffuser, then you
need not worry about this section. This is just for grills
where the heat rises up and hits the temp probe head on.
(Figure 164)
(Figure 165)
You see when you
push up the gas, a massive quantity of heat immediately rises
and strikes the probe within seconds, and causes wild
needle/temperature swings, it makes it hard to control your
roast. We will make a quick shield to shield the probe
from the heat blast, giving us a better idea of actual internal
temperature. (Figure 165)
(Figure
166)
This is simply a
piece of sheet metal, with tabs cut in the top, the tabs folded
over and three screws run through the front of the grill.
Now the heat column is directed around the probe and the probe
now measures internal temp, and fluctuations are mitigated
significantly. Note the sheet metal is taller then the probe,
completely shielding it from the heat blast.
(Figure 166)
(Figure
167)
Here is the view
with the lid open. (Figure 167)
That concludes
the sheet metal mods.
CONTINUE TO
TEST FIRING & FIRST RUN
inks
