Firstly, it is totally wrong to assume that I worked from theory - take a look at MEW Jan '97 back cover - not only will you seeEZE's in development but also discover the starting point. See Neville Palmer's letter in Dec 98 MEW - it was Roy L Clough's Little Dragon of which I have made and flown many [ hence becoming familiar with it's short comings] that started off the development of the EZE series. Each one I made contained one new idea to see if it was an improvement on the previous engine, so yes, I've made a lot of these engines. In formulating the article fo EZE, John G. asked me to aim it at those who have never made an engine before. So what did I do, I asked people who had never made an engine before about what equipment and what skills they had, and then I wrote the article. The drawings were not the ones that I had submitted to John, someone [not criticising] had kindly converted my imperial drawings [I think Tom means fractional -KC] to CAD and decimal. In doing so had cocked up two things. Firstly they were done in imperial units so that a ruler could be used to make this engine as some of the would-be constructors didn't have or didn't know how to use a mike or a vernier. Secondly, a number of dimensional errors crept in.

Perhaps I should state what the concept was all about.

  1. Anyone can make one with minimum machining.
  2. It will start easily.
  3. It will run with sufficient power to fly a small [30 to 36"] f/f model. [For glow I aimed at 10,000 rpm max on 6x3 or 4x6]
  4. It will last a couple of seasons use [has a bearing on materials used]
If you care to check the letters published and those sent to me personally, [a good one from Doug. Bellgove in Australia, MEW March '99,] you will see that I have achieved my criteria as set. Note Doug's performance figures. That engine is flying a 72" 2 channel r/c glider now I believe. The whole aim of my putting this motor into print was to encourage people to build, fly, and enjoy their own engines - again I've achieved some sucess in that sphere.

Criticism I welcome if constructive, uninformed opinion I am afraid I am not very tolerant of. A lot of development work has gone into the EZE series and is ongoing - I'm enjoying it. Now let me get on with the replies to the rest of the points raised.

One should understand the concept of the word sport as applied to flyer. [The guy who likes to fly a small model quietly, usually in a small place. This is a SPORTS ENGINE. The word howling [success] for me gives me an insight into your ideas, maybe you have used Cox's at 22,000pm on a 5x2. This is not what EZE is about. 10,000 rpm is the aimed for figure on a 6x3/6x4 - that is what it does - keeping these figures means usually easier starting - [see comments in Bowden's book on model diesels all those years ago!]

Comment on point number 2. A flat was used to keep the transfer passage volume in keeping with the rest of the design. You have milled yours concentric [difficult for a beginner or someone with limited machining. Keep the basic concept in mind. And, the comment that your engine does not sound happy, this is probably due to poor transfer pressure. I wonder if you are a "small engine person" and if you are familar with their symptoms and cures. I wonder why your engine floods easily. Perhaps too much transfer volume? Rotary valve: pressed pin - fine for someone who has built a few engines - my method is foolproof for an absolute beginner. Brass is used because it works well - I've had no failures, it machines easily and most people seem to have some in their material stores. As for weight - well if was designing something to rival a Shuriken the yes, otherwise it is just personal preference.

Now to the plug head. Again, fine if you want to machine cox heads to fit, or to copy their shape, then ok. But again you are loosing the thread of simplicity ie use of standard 1/4 x 32 plugs. Yes it performs best on a hot plug. As to the head chamber shape, you must be familiar with the concept of a squish band. This is along that train of thought, as by using different plug lengths, the compression ratio is experimented with. It works, I have tried it over more than two dozen motors. So have others and they have been successful. Clearly you are not the first to build one apart from myself. There are four others that I know of in my own area built to prove the drawings. In future it would be wise to stop guessing and surmising, and start asking. I am happy to talk, argue, and discuss my work anytime.

Finally, the one you have made is very pretty"

[Tom Crompton, England, September 1999]

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