Replacement for ZG-22

[Danyboy]

Hello altogether! :)

Not long ago I was able to do a real bargain-shopping with a gasser...

Actually it is a Robbe Futura Millenium with 810mm blades and a ZG-22 engine.

As I am fine-tuning the heli, I noticed that with high-load manoeuvers I have a significant drop in headspeed, going from dialled 1350 at zero-pitch down to a tad below 1150. Almost scary due to the sound and the climb-performance decrease...
I am running linear +9°/-9° pitch curve and throttle is maxed out...

Though I am strongly convinced this is partly being effected by the profiled blades, I do not believe symmetrical blades will offer the performance-increase I am looking for...

Let me assure you: Mixture *is* optimised, whatever i do there, it would only gets worse... ;)

This is why I start to look for a drop-in replacement...
But what to use?
I received no data-sheet about the engine with the heli...
Anyone knows some source of data?

I heard a ZG-23 would have the same hardpoints as the ZG-22?
Can anyone confirm this?

I'd be happy for inputs of any kind... :)

Sincerely,

Daniel

[Tom Fiddler]

Can you post a couple of Pictures of the engine from both sides of the Heli.
How old is this heli?

[Danyboy]

Tom,

Thank you very much for the reply! :)

Actually, the heli is about ten years old...
Which shows somehow in its components: I'll nickname it "the oldtimer"... ;) Flies well though... :)

It's been built ten years ago by a LHS, dialled and flown in, then being flown about five times by the owner until he busted a set of wooden tail-blades. Then it's been disassembled in the major assies and been put into storage. I couldn't believe my eyes, but everything *really* looked like fresh off the shelf...

The heli itself is no more being produced by Robbe.

Robbe did offer a conversion-package with it, to install this ZG-22 engine on, so nothing self-made or trial'n'error-style... :)
Bad side seems though, that technology wasn't that far advanced those days.
Though the silencer looks nice, I'd expect some increase in power with a modern replacement...

Nevertheless, I'd look for a stronger engine:
I do not really feel comfortable with the RPM dropping to about just 1100RPM, especially in *those* situation where you need your nerves and attention elsewhere... Let me tell you that it's a *very* scary sound, to hear the engine and the rotor bog that much...
I do expect less bogging by increasing the RPM (meaning less pitch and less torque) and maybe a smarter silencer (and will also conduct testing in that direction) but still I'm not conviced I could get in the levels of what I'm looking for with these modification and tunings.
Perhaps NOS is a valid option? ;)

I did some photoshooting this evening, zipped everything and putten it online here (http://www.xknights.ch/modellflug/futuramillenium.zip) as a zip-file on my webspace for viewing at your discretion...
If you like some closeups, just give me a shout, I'll gladly help you to help me! :)

Cheers,

Daniel

[Tom Fiddler]

I can't find your pictures.
I would like to see close ups of the engine and mounting

[Danyboy]

Hello Tom...

If you have a look at the post above...
In the sentence "...putten it online here as a zip-file...", does the word "here" appear blue, like a link...? It should be the link... ;)
If it didn't work, I'm sorry...

Just to make sure, here's the link in plain text:
http://www.xknights.ch/modellflug/futuramillenium.zip

Again, thank you very much for looking into this!

Cheers,

Daniel

[Tom Fiddler]

Sorry, My vision must really be getting bad.
Very nice pictures! I'm not sure, but I believe a G231puh would fit in there. You would have to redrill the mounting holes (or make a plate) on the bottom, as these engines only use 3 bolts. Let me do some research on the ZG22, to see if I can find out more. Do you know what gear ratio this heli has?

[Danyboy]

Hey Tom, that's more I can ask for... :)

I did know the ratio, but I'm not sure by heart, either 1:8.51 or 1:5.81, I tend to believe the former... I'll keep you updated once I had a chance to glance back in the manual...

I would be really glad to get any information you can find on the ZG-22...
Basically, I've found none, only some rough setup-manual which is for application in rc-cars...

Already now: Thank you very much for your help!!! :)

Sincerely,

Daniel

[Danyboy]

Tom,

Update on the gear-ratio...

I just checked and found 1:5,83, as originally advertised...

I guess I should try much higher headspeeds like 1500RPM to get the engine in the 9000RPM-range.

Meaybe I'll have time to test-fly this weekend, I'll get back with infos as soon as I have them...

Cheers,

Daniel

[update]
Testflighted this weekend, the engine won't spin the head any faster than 1350RPM... Still drops to 1150RPM... :(

[Danyboy]

OK, I'm somewhat pissed-off...

Another lesson learned:
Muffler has more influence than one might think...

Preamble:
Previous owner had installed the silencer with pretty short screws. There even was a reason for it, and it was the body of the silencer itself, that was in the way to install longer screws.
So all they catched, was maximum two turns on the flange's thread.

Which was the reason they came loose every second or third flight, which is why I have a scar on the rear skid: Lower screw loose, upper completely out of thread, silencer follows gravity and drops on the skid. Inflight.
I have installed grub screws that go all the way through the flange, also used some heat-resistant sealant to keep them in the thread, so I had two threaded studs onto which I screwed the silencer with nuts.
Even marked it with torque-/inspectors-laquer so I can see them immediately when getting loose.

Well, all in all it's now between ten and fifteen flight that the nuts were holding up, as I wanted to check and fine-tune the mixture again.
Funilly, I was not able to use a consistent mixture, it apeared the correct mixture was changing... Additionally, the engine appeared to gain a little on power...? I did not measure the headspeed, but it sounded to have increased from initial 1300 to 1450 with same TX-settings.
After about the fifth flight, just before I wanted to put it down, I consciously noticed vibration on the silencer. It was there before, not that much, but I saw it, but I did not take note of it.
Just then a light went off in my head...

As the screws were getting loose (the lower one was about one turn out, upper just a quarter of a turn), exhaust gas was able to bypass the muffler, thus unloading the backpressure from the muffler, increasing power of the engine and changing the mixture with it.

It's definitely worth to have a modern silencer installed.
Beside the power-increase I'm looking forward to, I can also safety-wire the screws, keeping them forever in place.

Also I start to suspect, the previous owner selected that silencer because of looks and flange, not matched to the engine. I agree it looks cool and matches somehow the heli's colour. But as I look at the silencer of my friends Raptor30, it's almost the same, not much smaller... I know, I know, size does not really matter here, it's about frequency and volume, but then again, an OS30 has definitely different frequ's and exhaust-volumes than a 22ccm...

Just wanted to share this... :)

Cheers,

Daniel

[Danyboy]

General Information...

I just got into contact with a german shop that has been into the gazbiz for more than 10 years: www.toni-clark.com

Been told the following about the question, what would fit instead of the ZG-22 I currently have:

"Almost-drop-in-replacement" would be the ZG231SLH. Slight modifications on cooling-duct are needed as well as two bushing due to the slimmer casing.
Much better power, though not yet as powerful as the ZG26SLH, which would need some mod on the frame to get installed.

Optimum RPM of the ZG-22 was between 9'500 and 10'000RPM. Known disadvantages were overheating with lower RPM due to the small radial-blower which is designed for glow-powered operation at high RPM. And with high RPM there was the problem of vibrations of the isolator-contact of the magneto.

Just thought I write this down somehwere once I've been digging it up so others could profit from it too.

Well then, let's go and save some money... :-)

Cheers,

Daniel

[Tom Fiddler]

Cool Danny...Go get it!! :mrgreen:

[Danyboy]

I did it...

About 2 months ago... :oops:

But had the maiden flight last weekend... :thumbup:

And I have to say:
Whoa...

Compared to before, there's awesome power there compared to before...
And flighttime compared to the 400-electric I had until lately, even compared to the turbine... :bang

So what've I got?
Engine is now a Titan ZG-231SLH with a Zimmermann Resotube (15ccm, 40mm). Heli is a Futura millenium with stretched boom (1,8mm)...
Engine did fit with only minor modification: Spacers on the engine mount had to be shortened (about halfway) and the cooling air shroud had to be widened to fit around the bigger cooling fins.

Starting is a breeze: For first flight of the day push primer-bulb until it overflows through the tube, then pull twice when choked and throttle open, once more when un-choked and idle-throttle - et voilà...
Before it was quite a workout... Talk about a lot of guesswork with a lot of aerobics...

Needles were factory-tuned and were pretty much spot-on.

Since that heli seems to be so much forgiving and as perfect for hovering as I ever had a heli, I guess that'll be my new workhorse... Bad thing though is the volume of exhaust-sound. Though a very pleasant note from the reso, it still is quite loud. I'd guess same volume as my turbine, if not even higher...
I even finished the onboard-generator (which I honestly started pretty exactly 2 months before I read about it here on helifreak... ;) ), which makes it also the perfect heli to fly when it's cold outside (low-battery-voltage due temperature).

One thing though...
The shop where I bought the engine-combo (www.toni-clark.com) did clearly indicate that to connect engine exhaust to muffler, no teflon or even silicone should be use due to high-temperatures. A note about the *whole* exhaust-system being considerably higher in temperature than with a nitro (not only between engine and muffler) would be helpful. Guess how I know... Stock bracket for reso-installation (on the exhaust side, reso's more than 30cm long...) melted away... :P Lesson learned, now it's steel...

Things left on the to-do-list are optimization of antenna-routing and installation of underload-bracket (talk about underslung loads and bambi-bucket... :) ), this boy is gonna be my new workhorse... :bad

On a side-note, I'm quite happy to have changed my little sports-car into a space-wagon, I now have enough space to load turbine and gasser with equipment and still have enough space for one passenger...

Cheers from Daniel, unfortunately at work again...

[Danyboy]

Some flights have passed now, though not as much as I would have liked due to the pretty cold winter we had. Almost no flying possible. So much for global warming...


All in all, I guess I have a little over two gallons of fuel through the engine.
As I stated before, the needles appeared to be quite well tuned, which is why I left them alone.

As I noted recently, I get more and more tail-kicks. Which to my knowledge indicates a too rich mixture. Hurray, I thought, finally getting broken-in, but I still left the needles, just to be on the safe side.
But then, just three flights ago, the engine seemed to loose power when I was in a low hover. The power dropped more and more while I fiddled with spool-up and such. It looked to me, as if I was too lean...
So I opened both needles a tad (about the width of the screw-driver slot), and flew happily for another two and a half tanks.
Two days later, I get quite some smoke which wouldn't even fade away after I went to hover. So I had to adjust the needles back towards closed. I am now at the same positions as before, maybe a tad leaner.

When the engine is purring away in idle, I always get some smoke. After I spool up to flight-idle and hover, the smoke will fade away after about ten seconds. I still have the quite frequent tail-kicks of which I would really like to get rid. The sound is somewhat smooth, though there is a wavering note to it.

I am quite afraid of toasting the engine by fiddling around the mixture-screws, so I'm looking for some advise here...

Engine is a Zenoah 231PUH, fuel is our standard 95 octane gasoline with 1:28 Castrol Moto-Sport oil. I'm running 790 profiled blades with 1450RPM's, the gearing is 1:5,83.

What I am not sure about, is first of all the smoke. May there be some smoke or does it mean, the low-needle is too rich?
That would indicate my second question as to whether it is really the case that hover is mainly controlled by the low-needle.
If the engine should be smoke-free in any throttle-regime, that would indicate the hover is controlled mostly by the high-needle, which is why the smoke clears after around 10s of hovering.
Did I get this right or am I completely wrong?

What are the indications of the engine breaking-in?
I guess a richer mixture leading to tail-kicks and... what else?

Thanks very much for your advises!

Cheers,

Daniel