If you want to put on a show, you have to have smoke. You can take my word for it, nothing gets attention like a plane with a good smoker. From Cubs to Lasers, smoke makes your aerobatics or your crop dusting look 200 percent better. Even if you are on your first giant, consider a smoke system. You will like it.

There are several smoke pumps on the market, and I have two of the more popular ones, the B&B and the Harris. The only smoke muffler I have used is the B&B. I have it on a Sachs, a Bully and a Zenoah. I am sure that other pumps work well, I have just been satisfied by these two. I admit that I use B&B mufflers because I saw their advertisement in High Flight and other fliers at meets use them. The two pumps are different types, the B&B uses a Mikuni diaphram pump powered by crankcase pressure. The Harris uses an electric pump powered by two AA batteries. Both require a servo for switching. Both are also comparable and priced less than $25.

My subject for this article is not the pumps but the fluid, the stuff that goes in and makes the smoke. I normally run straight diesel fuel from the local Amoco station. I know they are still wondering why this guy always stops by on the weekends and gets one gallon of gas and one gallon of diesel. Straight diesel has always worked fine, but I hear now and then about this great smoke fluid that puts out gobs of smoke that hangs around for several minutes. I haven't seen any but I have heard of it. I occasionally read in other columns about certain different oils that work really well. I have been keeping these formulas for a couple of years and the time had come to make a test.

Terry Green of Craptech Unlimited came over to help and verify the tests. I have a big engine test stand (wood) and I took the Zenoah G-38 with B&B smoke muffler out of Phyllis' Air Tech Duster and mounted it. I bolted an extra B&B smoke pump I have to the side and hooked the plumbing up. Cambell's soup supplied a smoke oil tank, the open top made it easy to pour in the oil. This whole mess was bolted to a table and I was ready.

For the test I planned to use as many of the formulas as I could find. The baseline was straight diesel. All the smoke was compared to it. Here's the fluids I used:
1. Diesel
2. Diesel 75%, Kerosene 25%
3. Diesel 50%, kerosene 50%
4. Hollywood smoke oil?
5. Kerosene with Dissolved parafin
6. Kerosene 75%, cutting oil 25%
7. B&B smoke fluid
8. Diesel 75%, B&B 25%

Diesel and kerosene you know about. The Hollywood smoke oil was given to me by one of the other members of my club. It is supposed to be what they use in movie aerobatic planes to make smoke. The cutting oil is regular machine shop cutting oil; it's pretty thick and had to be cut. The kerosene and parafin I have read made really good smoke. Terry cooked up a pot of kerosene on the gas grill and dissolved (melted) the parafin. The B&B oil is Dick Bennet's secret formula for $5.95 a gallon.

We cranked up the trusty Zenoah on a Sunday afternoon and poured in the oils. Then the three of us (Phyllis, Terry and myself) stood back and looked at the length and persistence of the smoke trail. Here it is:

THE WINNER WAS B&B SMOKE OIL (by a bunch).

Dick Bennet has some good stuff here. Really puts out a persistent trail of smoke. The cutting oil and parafin mixes didn't even come close. Straight diesel still works pretty good. I tried the diesel kerosene mixes because someone told me that it was easier to pump and worked well. The 75-25 looked slightly better than straight diesel and I'll probably use it for regular flying. The 75% diesel, 25% B&B was also good. The others had nowhere the persistence of those I have already mentioned. Maybe I didn't have the right mixture, but we also tried every other combination of these fluids. My bottom line is this: I'll use B&B fluid for meets, got to have the good stuff. For local flying to cut the down the cost, I'll use a 75-25 mix of diesel and kerosene.

I have to admit that the smoke muffler can make a difference. I used the B&B to keep everything the same for the test of the fluids. Harris' muffler is supposed to smoke really well, but I have yet to see one. Terry Green and I are working on our own smoke muffler design made from the little "lawn mower" muffler that comes on the Zenoah. If this works, I'll hunt up one for the Sachs on my main plane. It would be nice to try the various smoke mufflers with the same fluid to see which one of these does the best.

Finally, if you know of any more smoke formulas, I'll be glad to try them. Drop me a line. Put on a show but safely.

Editor's Note: Erwin Koberstein, IMAA 4151, of Regina, Sask, Canada writes, wanting to know if there are any of our members that have a formula for mixing an oil for colored smoke... red, blue or green? If anyone has and is sure it'll work without too much of a mess, send it to the attention of this publication and it will be printed for all members.

In response to Don's Smoke Test article, Hubert wrote the following:

Dear Ed:

Not only the Model-Pilots have "Smoke Oil" problems, the "Big Ones" require just about the same nerves to get the right kind of smoke. Several factors play the role:

1. Oil Flow (amount of fluid from pump to muffler)
2. Oil Pressures (back pressure from nozzle installed on muffler).
3. Oil Viscosity (approximately 2 degrees Engler)
4. Oil Distribution in Muffler
5. Tail Pipe Temperature and Vaccum

Being an air show pilot myself for years and having model experience for nearly two years, my North American T-60 really does put out the smoke like no other system will. Up to 4 minutes visible. I designed my system for use of approximately 10 W oil and 2 gallons per minute are consumed with my 1340 cu.in. Pratt and Whitney. Formula 0.0015 U.S. Gallon per cu.in.

SMOKE FLUID/OIL
Diesel fuel I would never use. Several reasons, even though some pilots do. It causes higher temperatures, more backpressure to the exhaust valves (loss of power/high cylinder head temperature) and the smoke is not that good anyway.

The very best oil one can get is manufactured by TEXACO OIL CORPORATION under the specification "CORVUS OIL 13", approximately $2.00 per gallon.

This type of oil is used as "Concrete-Form Oil" and you may ask somebody at your nearest Air Show this summer. They may let you have two or three gallons. This type of oil is light and does not need any dilution. TRY IT. Your injection nozzle should be as close as possible to the exhaust port of the engine. You may have to increase or decrease your supply line/nozzle to achieve volume/pressure and with the right amount of temperature you will get good lasting smoke. There is one other good oil, it is "Transformer Cooling Oil". However, this one is highly toxic. You may get this from your local power company.

As for Erwin Doberstein of Regina, Saskatoon, Canada, asking how to make colored smoke. There is no way known in the Air Show circuit, International, by use of piston powered engines. Only with flares or turbine powered aircraft. In the case of jet engines, various kinds of color is achieved by injecting magnesium powder.

Well, I hope that my experience could be of some help to you. Also you may find some improper english in this letter since I am a recent immigrant from Germany.

For one year I'm into model airplanes. Currently I am building the 72-inch T-6 (Circus Hobbies) and considering a smoke system installation. I enjoyed your report in High Flight. A very nice magazine. For your future testing, I wish you luck and good flying. Mit Fraundlichen Gruessen. Sincerely, Hals-und-Beinbruch. Lynnwood, WA.