Airwaves

Model Airplane News, Jan 1998

SOFT MOUNTS FOR SMALL ENGINES

I've been reading your articles for quite a while and have always found your opinions dead on. I agree heartily with form following function in most aspects of this hobby.

After reading your article in the October 1997 issue of Model Airplane News, I decided to drop you a line. I, too, have always been a gear-head.

I'm writing to get your opinion on soft-mounting the little O.S: 26 on a Clancy Lazy Bee. Clancy describes using fuel tubing above and below the mounting screws. Not a very good setup, in my opinion.

What are your thoughts on a better idea?

LYNN DODSON via email

Thanks for the support; I appreciate it. Soft mounts certainly do have their place within the broad spectrum of our hobby. On .25 to .90-size glow engines (2- and 4-stroke), however, the soft mount is not the answer, in my opinion. I'm still a believer in rigid mounts-the more rigid the better-in combination with carefully balanced props and spinners. Hard maple mounts extending through the firewall and passing through former 2 and possibly former 3 are an excellent rigid setup. Aluminum beam mounts are also a good choice. I prefer them over radial aluminum mounts because the two separate beams that are bolted to the firewall spread out over a larger area than do the radial types, thereby reinforcing and stiffening the firewall.

Good luck, and balance that prop. CC

APPRECIATES OUR HONESTY!

I read your article concerning oil content in fuels. Thank you for being frank with your readers about this, as it has caused us great cost through the years.

RJL has always recommended at least 18 percent oil with our RJL, HP and Mecoa engines. When you drop below this amount, you walk a fine line between survival and absolute disaster for your engine.

Usually less oil content will provide a slight power increase, as you have more burnable fuel, but along with that, you run the risk of higher temperatures and the initiation of wear. Once wear starts from lack of oil, it can't be reversed. These are some of the problems we have encourtered from low oil content: Piston rings getting stuck in the groove from the aluminum piston material scuffing into the ring area. This usually happens when the break-in period is rushed with a low oil content fuel. Wristpin areas in piston wearing prematurely.

Bearings wearing much faster than normal. Remember, 14,000rpm is severe duty for ball bearings.

Also a note:

Really hard chrome holds up better than nickel in cylinders, but both work fine with the right oil content. The other big problem is RUST. Some oils do not have the protective properties of good old castor. We recommend fuel with some castor.

I've seen engines as old as only a few weeks coming back with rust on bearings, cranks, wristpins and every other steel part. Naturally, it's our fault, right? The alcohol in glow fuel attracts moisture from the air. If you don't run your engine dry and use an after-run oil, you'll get rust; or you could just use an allcastor fuel like the good old days and put up with the mess all over your airplane. Anyway, thanks for writing the article and hopefully getting some fuel manufacturers in gear with some really useful information on their productrather than just nitro content.

RANDY LINSALATO RJL Industries

OIL CONTENT IN FUELS

Several people have called or sent me copies of Chris Chianelli's article in the October issue entitled, "Oil ContentThe Right to Know." Mr. Chianelli has made so many outrageous, inaccurate, untrue and offensive statements, it's hard to know where to begin. How about with, "Don't let any self-appointed 'expert' talk you into second-guessing the designers of these engines." It would appear that Mr. Chianelli has ordained himself the "self-appointed expert," and without any professional credentials on the subject whatever that I am aware of.

There are a number of very good reasons for a fuel manufacturer to not list the oil contents of the fuels on the labels, the most important being that the amount of oil required for a model engine fuel to function properly is entirely dependent upon what kinds of oils are being used. As with food, all oils are not the same and darned sure aren't equal.

Mr. Chianelli glaringly exposes his own ignorance on the subject by either ignoring this fact, or being totally unaware of it. As an example, one popular brand of engine now includes wording in their instruction sheet to the effect that they no longer recommend oil contents because of the great differences in the different types of oils. Except in the rather unlikely event the user had extensive knowledge and expertise on the subject of lubricants, a percentage number printed on the jug would not only be meaningless and useless, but most likely quite misleading. Knowing that they have no control of what kinds of oils are going to be used in their engines, most manufacturers simply try their best to protect themselves by stating a percentage high enough to cover as many potentials as possible. Let Mr. Chianelli invest years of his time and hundreds of thousands of dollars of his money in a fuel manufacturing business, and then see how willing he is to "tell all" about ingredients.