History/info on 4/2/4 break

Greets from down under,

My father flew primarily free flight and some control line in his early days and got me hooked on C/L as a boy. He has now retired and has the time and cash to fly R/C, which he is slowly learning to do.

He writes articles for his club magazine and was interested in educating the R/C community on the ol' 4/2/4 break - until recently neither of us had experience with this since I mostly used diesels as a boy and F/F is not big on aerobatics (or motor runs long enough to worry about 4/2/4 come to think of it)

He asked me if I could find out as much about the 4/2/4 as possible, in particular:
- who figured this out?
- was it accident or by design?
- what are the main engines that exhibit this?
- what parts of the engine design contribute to this (related to 2 I guess!)
- anything else of interest or humor

Any help or pointers to information would be gratefully accepted - you will be immortalised in print if you reply!

TIA

Dave.

PS: My Dad tricked me into my first ever R/C flight on the weekend - I had taken the kids to see Grandpa flying his planes and next thing the box was in my hands and one of the instructors was taking me round the circuit! It was fun, but not enough to make me a convert. There is definitely something about sharp whirly things hurtling round your head, threatening to pull your arm out of its socket that add a sense of immediacy to the experience. I dare say I wouldn't even have flinched if I put Dad's plane into the dirt, which is pretty sad really.

I don't think anybody actually figured this out or designed it that way, it "just happened". It also is not necessary to a good stunt pattern as you should well know if you are used to diesels (or piped engines or 4-strokes, etc, etc.)...

> - who figured this out?

That I can't be sure about, but George Aldrich is the one who made it popular.

> - was it accident or by design?

Orwick never claimed it as intentional.

> - what are the main engines that exhibit this?

The first was supposed to be the Orwick spark ignition 64 (according to GMA -- I've never heard one of those run). Next was the Fox 29/35, followed by the series 100 Veco 29/35, and then the K&B 29S. The Testors McCoy, according to Aldrich, had the best breaking characteristics of them all. I almost left out the smaller 15/19/25 Fox engines of the mid-1950's, starting from the three-bolt 19 in about 1954.

The UK's mid-1960's Merco 35 will run in a 4-2-4, and is a dead ringer for a Veco Series 100. Finally, comparatively late in the history of the baffle-piston engines and of 4-2-4 operation, the two that I thought ran that way best were the Max-S 35 and the G21-46 Tigre. The Max H's were available before the S's, but not popular for stunt -- most of H-40's do a useful 4-2-4, but the audio note is misleading on those.

>
Once upon a time, George's own web site had some text files about the "right" setup in his opinion, and his slogan for that web site was "Home of the 4-2-4 Run". (Or it could as easily have said "Birth place of the 4-2-4 Run".)
>

.

Kiwi

If you want to know who popularized the 2-4 break, give the credit to
George Aldrich.

Larry Scarinzi told me a funny story about it. He and Red Reinhart were at one of the Plymouth International meets (held at Belle Isle
near Detriot Michigan) and were sitting on a small hill watching a hotshot getting ready to fly his stunt pattern. The guy had almost won stunt at the Nats, so Larry and Red were interested to see him fly. The guy started his engine and took off. The engine sounded too rich, and Red said " Aw, the poor guy got a rich run." The airplane putted around the circle, hit the wingover, went into the two stroke, finished the pattern, and won the Stunt event!

The guy's name was George Aldrich.

Greetings from downunder also (check my name )..

I won't go into the history or which engines exhibit this because others are far more qualified than me. Not to mention that I simply can't remember now how I used to run my Merco 35's and Enya 45 back in the 60's and 70's. Well OK, there's the Fox 35 (which I've never used) but I've read that some put its break partly down to the very short intake although I can't see how this could help.

As to why some engines are more prone to the 4-2-4 break, it seems to revolve around having a certain amount of inefficiency in the scavenging process. This can be because of a short blowdown interval giving less time for the exhaust to escape or baffled pistons which are less efficient at giving turbulence and directing the fresh charge (their combustion chamber shape isn't as good either).

However, this can't be the complete answer because some years ago I bought a Stalker 61 (not their 4-2-4 version) and after some initial running in the very first flight gave me a magnificent 4-2-4 run. I remember thinking wow, so this is what it's like. But as more flights were done this break gradually faded away until now it runs a constant 4 stroke. This is a baffled piston non-Schneurle engine. In my case I think the initial 4-2-4 break effect was more psychological than of real benefit.

My ST G51 on the other hand had a HUGE 2 stroke break that was uncontrollable until I added far more oil to the fuel. This eliminated the break entirely so possibly by experimenting with oil quantities I could get it to give a mild break.

Duke Fox ran ads in the popular-at-the-time magazine "Boy's Life" that featured the Fox stunt motor and Fox fuel. One of the ads showed a description of the AMA square eight and showed the places on the eight where "deceleration forces" caused the motor to run leaner and thus increase power at those places. No mention was made of the phrase "2-4 break", but that is what it was. This dated around 1956. Best regards, dale gleason

George Aldrich mentioned online and in videos that blowdown time was a primary factor. Other things to adjust the run included compression ratio, plug, venturi size, prop, etc.

GMA also mentioned that his brother had encouraged him to fly slower. Perhaps in his quest to fly slower, he ran across the 4-2-4 run.

Back in "the days" some of us referred to it as a 4-2 break but actually the last 4 in 4-2-4 is important. Someone corrected me on this. Lots of engines will lean out and stay there if you launch a bit rich.