GZ 061N

GZ061N left GZ061N top GZ061N right

GZ061N in standard form with Nelson head. Jerry Barnette photos.

This is a Chinese made twin ball race, Schnuerle ported engine using ABC technology. The GZ 061N, which replaced the earlier CS 061N, is not a dedicated F1J engine so it is not fitted with a brake or flood-off inlet and, at 82 g, its no lightweight. Older engines used a custom glow button but current production GZ 061N units are designed to use a Nelson plug. They follow current best practice by using a two piece head. A clamp ring is attached to the crank case with four machine screws. This retains an alloy insert which combines the roles of cylinder head, combustion chamber and squish band. It is a push fit in the chromed brass liner. Screwing the plug in and tightening it down expands the insert to form a good gas seal with the liner. Removing the insert with the plug installed is not recommended. Doing so may damage the engine.

NOTE: Only the GZ 061N has suitable timing for F1J or F1P. The GZ 061S version is timed for a tuned pipe. There is also a diesel version, the GZ 061D, which is presumably a sport engine.

People who used the CS 061N all reworked it extensively so, though it was cheap, it was not usable out of the box like the Norvel 061. Doug Galbreath sold much modified CS 049N and CS 061N engines for Free Flight use. He eventually gave up on them due to quality control problems, which was creating too much work for him to be a viable business. Doug said that he thought the CS engines were made in a trade school, or something like one, because there was no pattern to the quality problems. Each engine seemed to have its own individual shortcomings as if there were many different machinists making their own mistakes.

The major CS user in the UK was the late Pete Buskell. I know he had to do a lot of work on the internals and then use his own tiny, narrow bladed carbon props to make them go. Even so there was rather more sound and fury than the performance seemed to warrant because the climb heights were way behind what Stafford Screen was achieving with his AD-06.

GZ061N left rear view GZ049N cutaway drawing

GZ061N as above. Jerry Barnette photo.

GZ 049N cross section. This differs from production models by showing a single piece head with the plug set too high: see the following text for details.

The only performance information I have for the GZ series engines comes from Robert Rayzak in Canada. He purchased a GZ 049N directly from James Zhou when he visited Canada. His engine is in factory condition except that the clamping ring inner diameter needed relieving to clear the hexagonal plug body. Without this the plug fouled on the ring when it was screwed home. He says the engine is only happy on pressure feed and that it makes little difference whether the venturi insert is fitted or not. He experimented with using no, one, or two head shims and found it ran best with one shim as it came from box. The engine was broken in on FAI fuel and then turned an APC 5.5" x 2" prop at 26,700 on 25% nitro. The main operational problem he found was that the spinner is too small for APC props, but he is overcoming that by fitting a turned conical prop nut supplied by Doug Galbreath. This sounds as if it is similar to the one I fitted to my Rex-06.

If the GZ 061N is a bored out GZ 049N with the same crank throw and con-rod I'd expect it to turn an APC 5.5" x 2" prop at 27,700 on 25% nitro: this is approximately the same rpm difference found when the Cyclon-06 and Cyclon-049 are compared using the same prop and fuel. That puts the GZ 061N and GZ 049N into the top half of my "mid-range" classification: they would have to turn the larger APC 6 x 2 at those speeds to be classified amongst the "hot engines".

These engines are available from Raptorz (Meng Ying) Air Model Company. Ltd. who are based in Shanghai, China. Contact details are on the web site. The US agent is James Zhou.