Smoke System:
Starduster
Too Smoke System
Somewhere
around November of 2000 I saw, on the Starduster Bulletin Board, that Gary
DeBaun was contemplating putting a smoke system on his Acroduster. I decided at
that moment that I wanted to do exactly the same thing on my Starduster. Now
neither Gary nor I had a clue as to what a smoke system looked like or what was
entailed in creating one for an airplane. At that point both he and I began the
long process (or at least it seemed long to us) of building a smoke oil
injections system for our planes.
We
began with BB posts, asking those who had built smoke systems, “How do we make
our birds smoke”. Answers to most of our questions were answered in bits and
pieces. In retrospect I suppose the answers were quite succinct and to the
point. However, not having a clue as to what we needed, it seemed like we were
getting only about half of the answer many times.
What
I found is that the system really isn’t very complicated, but if you don’t
know what it looks like and you don’t have a parts list then the design of the
system is daunting to say the least. I was also reminded several times that
smoke oil IS flammable and you are exhausting a heated, vaporized, flammable
substance right under your seat! I was also told to make absolutely sure I
didn’t cut the throttle WHILE injecting oil. I suppose a possible backfire
could ignite the oil and make a really spectacular site from the ground, and a
really big surprise in the air. The guys doing this professionally even suggest
a Nomex suit before you turn the smoke on. I don’t know whether all of that is
necessary or not, but I am adding it as a caution and a reminder that making
smoke may be pretty but it ‘ain’t without it’s hazard’s’.
I
knew from posts on the BB that a good system would probably put out in the
neighborhood of 1 gal of oil per minute, and I would probably want 5 gallons of
oil capacity to allow for 5 minutes worth of smoke. I didn’t want any more of
this tank intruding into an already small cockpit than was absolutely necessary
and I wanted the tank as near to the firewall as possible because my bird is
already way heavy on the tail. Various sources on the BB also suggested that I
would need at least 15psi oil pressure to feed the system. With those design
constraints in place I set about designing the system.
As
the tank seemed to me to be the most complicated part I created it first. I
designed a tank the fits partially below the front floorboards and partially
above it. The dimensions of the tank are approximately 26 inches wide under the
floor and 10 x 10 x 10 for the box, with the half moon shaped bottom area being
3 ¼ inches deep. The 3 ¼ depth is part of the 10 inch total height .I
purchased a 9” flop tube for oil pickup. The fuel cap is a twist to lock
non-vented cap.The tank has a side panel that is notched to fit around braces
and longerons in the aircraft floor. These plates were made from .090 aluminum
and just welded on the tank. The tank walls could probably be made out of .090
in this area and then the braces would become part of the tank proper. The
1-inch aluminum angle, also notched, has a 1/8 x 1 inch steel plate screwed on
to the top for added strength. I placed small pieces of hard rubber around the
notches to help prevent chaffing. This is the only portion of the installation I
am not really happy with, so if someone comes up with a better installation
method I’d like to hear about it. The tank is vented with a piece of 1/8 in
aluminum tubing welded through an AN816 fitting. This tube goes to within 1/8
inch of the top of the tank. It is screwed into a piece of ¼ inch plate welded
on the lower rear portion of the tank, which was drilled and tapped for the
fitting. The flop tube should just barely clear it when you are finished. You
will want to tack the tank together and make sure of clearances before final
welding. It clears the bungee posts by about ½ inch in front and JUST clears
the stick at the rear of the tank when the stick is in full aft position. As
individual builders may have somewhat different
dimensions
in their plane than I did, you should fabricate the tank to fit you dimensional
constraints. My tank holds almost exactly 5 gallons when full.I used a fuel tank
sloshing compound (obtained at a local auto parts dealer) to help prevent any
leaks along seams but if the tank is welded well that probably isn’t
necessary. I also welded baffle plates across the tank where the half moon
section meets the square top. That was done to help stop sloshing of oil in the
tank when you roll the plane and the tank is not full. The baffles essentially
continue the square top down to the bottom of the tank.
Forward
of the tank, passing right between the triangular bungee cord attach bracing is
a length of 601-6 Aeroquip hose. This hose connects to an AN833-6D bulkhead
elbow. From that point 3/8 aluminum tubing, bent to clear firewall throttle and
mixture components, connects to a filter and then a high pressure fuel pump. The
pump I used does not have an internal filter screen and I have been warned that
not using a filter will cause a lot of grief. The pressure relief valve inside
the pump will plug and then one must disassemble the pump to clean the valve.
The filter, with that thought in mind, seemed like a good idea. The pump itself
is mounted on a piece of 4430 steel plate bolted onto the lower part of the
battery box. From the output port of the pump more 601 hose connects to an
inline check valve and further downstream an aluminum T Bock. This block has a
3/8 pipe input and 2 1/8 pipe thread exit ports. I used a piece of .060 4130
plate to attach the block to the engine using two of the studs covering the
governor port on my engine. Those having constant speed props will need to find
some other mount point for this block. To connect
the
T-block to the exhaust system I had 2 flexible braided stainless steel Teflon
lined brake lines made at a local auto parts store. So far they seem to be
holding up very well. The injector nozzle was placed right after the 2 in one
header meet the collector past the swivel joint. I welded stainless steel bung
onto the SS header system right over a quarter inch hole I predrilled in the
exhaust collector. An AN816-2 nipple was welded shut on the pipe-threaded end
and then drilled through with a 1/16-inch drill to be used as an injector
nozzle. The beauty of this is that if you are too small or too large you just
drill it larger or weld it up and redrill. The injector nozzle is easily
removable. Photos accompanying the article should clarify any questions about
the setup.
The pump I used pulls only 2 amps. I used a combination switch/circuit breaker mounted in the panel to turn the smoke on. I suppose an on/off button could also be mounted on the stick but I haven’t done that and at this point it doesn’t really seem necessary. I also added a cutoff micro-switch that shuts the pump off when the RPM drops below 1500. This was a safety item added in deference to the concern I had for pulling the throttle back while in smoke mode without having time to otherwise switch the system off. By doing this I don’t even have to think about it. The switch is adjustable by moving the mounting position for different RPM ranges or it could be mounted as a normally open switch that is only closed when the Rpm’s reach a certain point. In this configuration it would need to be placed, of course, on the opposite side of the throttle arm. This switch is mounted on a bracket made from 1 inch angle aluminum cut to fit on the firewall throttle mixture control arm bracket.
That’s
all there is to it. Anyone who is reasonably competent in fabrication should
have no problems duplicating my system. The aluminum tank was the only thing
that was the least bit tricky and with a little planning it should present no
major problem.
Now
on the subject of which oil to use – I have used both the cheapest hydraulic
oil that WalMart sells ($7.50 for 2 gal) and
Most
of my parts were purchased from Aircraft Spruce. The parts list will include AS
part numbers if they are AS purchased parts. Other parts will have a
manufacturers part number or description where available. There are no special
purchase parts, everything is available from any aircraft parts supplier, your
local auto parts dealer(and
I would like to thank Buck Roetman, Frank Gorham, and Gary DeBaun for
all their encouragement, insights, and support during this project. And a big thanks to the
folks at Starduster for providing a Bulletin Board, without which, the project
would have most probably never been finished.
Bob Perkins
24BX
Parts List
1. 1. .050 and .090 Aluminum plate - amount will vary on final tank dimensions
2.
2.
8 ft of 1 x 1 inch angle aluminum
3.
3.
6 x 6 x .060 4130 plate to fabricat
mounting plates
4.
4.
4 ft 1 x 1/8 mild steel plate for angle
reinforcing material
5.
5.
assorted nuts and bolts for mounting
hardware
6.
6.
3/8” aluminum tube approximately 2 feet
S# 03-40600
7.
7.
¼” aluminum tube approximately 1 ft
(vent)
AS# 03-39300
8.
8.
Aluminum Manifold
AS#
04-00126
9.
9.
ACS twist to lock non vented cap
AS# 10600
10.
10.
ACS Free flow check valve
AS# 10630
11.
11.
Flop tube AS#
05-20509
12.
12.
Flop tube adapter AS#
10380-1
13.
13.
Aluminum Welding
14.
14.
Aeroquip 601 hose - 3/8 i.d.
approximately 4 ft AS#
601-6
15.
15.
6 Aeroquip hose fittings AS#
816-6D
16.
16.
Fuel pump from Summit Racing 140gph, 18psi
·
·
an alternative pump is a Blue Holly fuel
pump
17.
17.
Fuel filter 390 gph, 60 micron, 100psi
18.
18.
Micro switch - Selecta straight lever SPDT 15A
UPC#71180 mfg#
BZ-2RW80-A2-BG
·
·
This switch can be configured for either
normally closed or normally open
19.
19.
30 Ft of 16 gauge electrical wire
20.
20.
W31 series 5 amp circuit breaker
AS# W31X2M1G5
21.
21.
AN fittings
·
·
2 AN816-2D
·
·
2 AN816-2
steel for injector nozzles
·
·
4 AN816-6-6D
one is used
for vent
·
·
1 AN833-6D
·
·
1 AN822-6-6D
·
·
4 AN818-6D
· · 4 AN819-6D
Also look at http://musclebiplane.org/htmlfile/tanks.htm
