Old and New Powerplant Info
As many longtime readers may know, from time to time we like to bring lesser-known manufacturers or businesses with useful products or services to our readers’ attention. Such is the case this month with a company called Swanson Associates. Swanson Associates has been around for many years but has always kept a low-key approach to advertising. Swanson Associates was founded back in 1948 by Henry Swanson and brother-in-law Ben Shereshaw, with the main product being Fireball glow plugs. The name of the company at that time was Shereshaw & Swanson. Then in mid-1960, the partnership broke up, with Henry retaining ownership of the business and the company was renamed Swanson Associates. In 1980, due to health issues, Henry turned the business over to his son Kent, who now owns and operates the company.
Ben Shereshaw should be a familiar name to many of our old-timers as he manufactured the well-known Bantam engines prior to and following World War II. One item in the line of Fireball plugs that I found of particular interest is the “idle bar” plug. Idle bar plugs have been difficult to find in recent years due mainly to the fact that the newer Schnuerle-scavenged two-stroke engines generally do not require an idle bar plug for good idle and acceleration, whereas the old cross-flow baffled piston engines did due to the piston baffle directing the incoming air/fuel mixture directly at the plug. Schnuerle-scavenged engines utilize a flattop piston with the angularity of the transfer ports directing the incoming air/fuel mixture. If idle or acceleration problems are encountered, however, a Fireball idle bar plug can often solve the problem. (For more information, contact Swanson Associates at P.O. Box 151, Wayne, NJ 07470; 973-984-5930.
BIG ENGINE OIL CONTENT
The town in which I live has a hardware store that is a Ryobi dealer. It recently had a sale on Ryobi string trimmers, selling them for only $79.00. Never being able to pass up a bargain, I purchased one with the intention of possibly converting the engine to aircraft use as several of my flying friends have done. Being a sheet-metal worker by profession, I easily made a radial mount. My flying buddy is a machinist and made me a prop-drive assembly. Included is a picture of the finished project, which I feel turned out exceptionally nice. I intend to use that engine in a quarter-scale Fairchild PT-19 that I am building. The operating instructions that accompany the engine specify a fuel mixture of gasoline and 50:1 Ryobi motor oil, which brings me to my question.
I have both a Quadra 35 and 50 and have always used your recommended oil content fuel of 32:1 for break-in and 16:1 afterward with no problems. I am somewhat uncomfortable with using a 50:1 mix, especially when my O.S. 120 Surpass four-stroke and Enya .60 twostroke use 17 to 20% lubrication. Why would a larger gas burner require less oil than my smaller glow engines?—Charles Watson, Billings, Montana
Answer: Well, Charles, this is a question that I am sure quite a few of our readers have wondered about. First, one of the functions of the oil, besides lubrication, is to carry away heat (something that few of the oil and engine manufacturers seem to take into consideration). But to answer your question, my old friend Duke Fox used to run a paid advertisement called “Duke’s Mixture” in which he discussed various topics. In the August 1969 issue of Model Airplane News, he pretty much answered your question. Duke’s rather technical article might be hard to understand unless you have a college degree in internalcombustion engines. I have always tried to present topics of varying interest, so for our more technical types, here is Duke’s answer, more than likely taken from an engineering handbook.
Why do large engines require less oil, percentage wise, than smaller
ones? The reason being that as the size of the engine increases, the displacement goes up as the cube, while the area to be lubricated goes up by the square. Thus, an engine with a 1.50-inch bore would be as well lubricated on a 10% oil mix as a 0.75-inch bore would be with a 20% oil mix. This is known as the “lubricating area to displacement ratio.”
When doubling the engine’s bore from 0.75 inches (.35ci with a stroke of 0.75 inch) to 1.50 inches (2.65ci with a stroke of 1.50 inches), the cube of the bore increases (0.75 in. x 2 = 1.50 in.) 2 cubed (2 x 2 x
2), or 8 times. Assuming similar design features, an engine that is eight times larger than another will consume fuel eight times faster than the smaller engine. Conventional thinking suggests that eight times the lubrication will also be needed for the larger engine. The large 1.50-inch bore engine, however, has only four times the lubricating area of the 0.75-inch small-bore engine since cylinder area increases as the bore increases 2 squared (2 x 2), or 4 times.
Consequently, the large engine receives twice the lubrication of the smaller engine (8 ÷ 4 = 2). By reducing the large engine’s lubrication content by half (from 20 to 10%), it will be lubricated the same as the smaller engine. Based on traditional lubrication content, here are a few engine displacement sizes (bore = stroke), with their calculated lubrication percentages:
O.S. G5 GAS/GLOW PLUG
I have an Evolution 10cc gas engine, which I have been running with an O.S. glow G5 gas/plug from a GGT-15. While tuning and flying, I guess I got too lean and burned out the plug. I replaced the plug with what I thought was my spare G5 plug. The engine started and ran great, and I flew it for 10 minutes with no problems. I later found my spare new G5 plug, still in its original packaging. The plug I had used was a regular glow plug (for nitro engines). Why did it work so well, and will I damage anything if I just use the much-less-expensive regular glow plugs in lieu of the O.S. G5 plug?—Mike Rost, via email
Answer: Mike, I am afraid you have thrown a question at me for which I do not have an answer. Back in the July 2015 issue, I did a review on the GGT-15 and tried both the gas glow plug and a standard two-stroke plug. The standard plug did not work nearly as well, being harder to start, bad idle, etc. As I said previously, I do not have an answer for this. If any of our readers do, please let me know. At any rate, I am sure you will not harm your Evolution by using the standard glow plug. In the December issue (which should be in readers’ hands at the time of this writing), reader Dick Parkes was having trouble with his Evolution 15cc gas engine running the tank out. I suggested that he was just setting the engine too lean, as had the technicians at Evolution. Well, as they say, it’s the difference of opinion that makes the ball game, and readers Harold Smith and Malcolm Nelson disagreed with Evolution and my reply (see below).
OVERHEATING?
Your knowledge of engines far exceeds mine, but I think you missed the call in the December 2017 issue in your reply to Dick Parkes about his engine quitting after about 15 minutes of flight. I am familiar with the Goldberg Ultimate 3010, and the airplane had a cowled engine. When Mr. Parkes bench-ran the engine for 15 minutes, it was likely without the cowl. The problem sounds more like an overheating issue. He most likely does not have enough air-exit vents. The air inside the cowl is getting hot and overheating the engine. From his statement, it sounds as if the mixture settings are OK.—Harold Smith, via email
Answer: Harold, I believe your assumption is correct. When I gave my answer, I did not realize that the Goldberg Ultimate had a cowled engine. It is very important with cowled installations that there be adequate air exit; otherwise, pressure builds within the cowl and the cooling air just goes around rather than through the cowl.
CARBON DEPOSITS
I enjoy reading your column, and you no doubt have way more knowledge and experience with engines than I do. But having read
Dick Parkes problem with his O.S. and Evolution engines in the October 2017 issue, it reminded me of a problem I encountered not so long ago. The only common denominator is the fuel! I had the same problems he described until I noticed I was near the last pint or so of fuel in the bottle and I pumped it into a glass; much to my chagrin, it was laced with trash. I hadn’t flown as often as I usually do because of a pinched cervical nerve and I couldn’t look up without my right arm tingling, so I quit flying as often. The gallon of fuel lasted a long, long time that season. I rarely if ever fly the tank dry in any of my 10 airplanes, so when I pack up to go home, I pump whatever’s left in the tank back into the fuel bottle. About half of my engines are four-strokes; most of my engines are getting long in the tooth, so I believe that I pumped carbon deposits back into my fuel container by doing so. It’s not a problem when I burn a gallon a month or so, but over a much longer period, I think I contaminated the fuel. My solution was to open a new gallon of fuel, and the problem immediately went away.—Malcolm Nelson, via email
Answer: Thanks for sharing your experience with us, Malcolm. It is always appreciated when readers do this.