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Gohbee Aviation Stinger 30-90 > Gohbee / TZ / Raptor 90 Heli with BME modified G90 Gas Engine

AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Malorie,

Thats good info! Thanks! Still seems a bit odd to be getting 14,000+ from this engine under load but then again im new to fuel so everything seems a bit odd to me compared to electrics

A day without sunshine is like, well, night.

04-06-2006 Over year old.

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Ringo Ranger
Senior Heliman
Location: Honolulu, Hawaii

JB WELD IT

04-12-2006 Over year old.

Ringo Ranger
Senior Heliman
Location: Honolulu, Hawaii

I SENT BACK MY BME 90, & GET AN OS91 FZR HYPER. GET A RELIABLE POWERPLANT THAT WILL NOT STALL

04-12-2006 Over year old.

MRS
Heliman
Location: Netherlands

Reliable

MFIS could get a nitro powerplant, but that's less fun, expencive fuelcosts and maybe not as reliable.

The pioneers of things makes it a better world. It's always easier to do what everybody does. To do something different makes the individu getting out of the crowd.

Marcel

04-15-2006 Over year old.

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Harris
Senior Heliman
Location: Cyprus

MFIS-2,

How are you getting on with the G90? Any problems with overheating or vibrations?

Harris

04-15-2006 Over year old.

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AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Well, Funny you should ask. Ive finally gotten most issues sorted out and have been able to fly out about 3 tanks of gas yesterday and today. Yesterday i had no issues with overheating but today the engine stopped on me once after about 7-8 minutes of flight. I was in idle two and flying pretty much at the max throttle to get about 1620 on the head and with the needle a bit rich on the high. Not much but just enough that you could hear the engine 4-stroke every now and then and then power just started dropping slowly and when i brought it in to land it quit on me. Grabbed a temp gun and shot about 195 degrees Celsius on the head. Im assuming that was too hot. No damage to the engine because it started right up and ran fine after a cooldown but it started to do the same thing again after about 6-7 minutes or so on the next flight so i brought it in and set er down and let it idle to cool down and was able to fly some more.

Im not real sure what to try next. Ambient temps were only about 14 deg celsius max so this is definetly not going to work this way come summer temps unless i figure something out.

Please give me some input on which options i should pursue first to try and get temps down and which of these you think are most likely to help.

* switch to smaller than 710mm blades (680 or something like?)
* swap the stock fan with straight fins to a CNC curved fin fan setup which should maybe move more air over the engine?
* Just keep running the engine in (without overheating it) with the hope that as it breaks in fully it may run smoother and cooler with more power and less overheating?

Any other ideas? These are the only things that pop to my head as a newbie to fuel engines.

The engine DOES seem to have quite a bit of power. More in fact than i was expecting but i have never flown a glow model so have nothing to compare it to. It does seem to definetly have more power and outclimb the two guys I fly with who are both flying predator gassers with the 23cc zenoah. It likes to be run fast and hard and seems to really like a load.

I dont know. Im still having fun with it but many small little problems keep popping up. Just little annoying things that keep you busy tinkering instead of flying. Earlier i mentioned that i was getting 1800+ on the head but since then i realized i was running WAY too lean and had to richen that up and now im getting the 1600-1650 that one should expect from the gear ratio i am using and i have to say i really would like more rpm on this thing to have it fly the way i want it. Please someone make 13-14T pinions for a raptor or gohbee!

A day without sunshine is like, well, night.

04-15-2006 Over year old.

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AceBird
Elite Veteran
Location: Utica, NY USA

Quote
With a butterfly type carberator, the throttle is not linear, it is exponential. At about 30 or 40% on the radio, you are around half throttle.

Depends on how you set the mechanicals. Servo motors rotate so that means a sinosoidal motion. If you set your links right you can take most of the exponential out or double it.

Ace

Ace
What could be more fun?

04-16-2006 Over year old.

Chris Bergen
Key Veteran
Location: location

I believe Mal was thinking of the action of the butterfly in the carb itself.

To further aid the discussion, I spent some time finding this explanation from Mal, http://runryder.com/helicopter/t105349p1/, in addition here's a pic on how she sets it up to give a "linear" curve in the radio. http://runryder.com/helicopter/gall...rottleSetup.jpg

Chris Bergen

04-16-2006 Over year old.

Harris
Senior Heliman
Location: Cyprus

Anni,

Try to run the engine as rich as possible. After all it is just an airplane engine (i.e. not designed for the limited airflows produced by a heli fan)! Running it hot will not make it last for long.

You can certainly try the CNC fan. My friends who fly Raptors here in Cyprus are using it with pretty good results. You can also extend the fan shroud so that it covers the whole engine head and forces the air to pass through the fins.

How much oil are you using? Try a different make or increase the oil:fuel ratio.

Overall, don't expect this engine to give you the punch or the rpm to perform hard 3D. Regard your heli more like a scale or mild aerobatic machine. It will never be as powerful as an OS91.

Just my 0.02.

Have a nice day!

Harris

P.S. How about vibrations? And I mean engine vibrations!

04-16-2006 Over year old.

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MRS
Heliman
Location: Netherlands

Air flow

Anni,

Make a picture from the outlet of the fan scroud at the head. This way i will not be the only one saying you should chance the airflow.

Marcel

04-16-2006 Over year old.

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AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Hey guys,

I know airflow is one thing that definetly needs to be looked at and i dont disagree there at all i just was hoping to save modifying the fan shroud as a last resort. Some people are having luck with these engines in a 60 size heli without overheating so i just thought as a first attempt to address the overheating i would look at other issues before starting to mod the fan shroud. With the huge carbeurator on this engine blocking airflow i think there will be no other choice except do what Marcel, Harris, and others are recommending and modify/extend the fan shroud to get more airflow over the engine cooling fins.

Ive ordered a new cnc fan and smaller blades which i will also be trying just out of curiosity. I want to try every possible thing one at a time and see what works and what doesnt.

A day without sunshine is like, well, night.

04-16-2006 Over year old.

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Franconia2
Heliman
Location: Shrewsury, MA

Headspeed

Anni,

Success
Today I increased my headspeed to over 1920.....
Seems the muffler assembly can be tuned like a pipe. The G90 engine comes with a stock Supretigre muffler that consists of a straight header and a muffler. If you extend the muffler 20 MM out on the header the engine is a very happy puppy.

Richen the hi needle and move the muffler out on the header, this should fix a lot of problems.

For overheating, consider improving the fan shroud to completely cover the head. Have not experienced any overheating problem yet with ambient temps around 60F.

04-17-2006 Over year old.

MRS
Heliman
Location: Netherlands

Head speed

Over 1920!This looks promising!

Marcel

04-17-2006 Over year old.

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Franconia2
Heliman
Location: Shrewsury, MA

Headspeed

The headspeed increased from 1730 to 1920, the only change was the placement of the muffler on the header.

04-17-2006 Over year old.

AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Franconia,

Thats great info! Im having Zimmerman custom make a muffler for me for this engine which should be here this week. It will interesting to see if i get any performance increase with this. If not im going to try your suggestion.

A day without sunshine is like, well, night.

04-17-2006 Over year old.

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AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

WOW! Thats all i can say right now! But thats a good thing....

Today is the first time I came home from the field HAPPY with this machine. What was pissing me off about it?

1) PCM lockouts that i have NOT been able to find the reason for and coming at VERY odd and unpredictable times.
2) engine overheating after about 6-7 minutes of flight.
3) Muffler falling off / Vibration

All of these issues were fixed today and i finally got to enjoy it a bit without worrying about what was gonna break or if it was going to lockout.

The lockouts were 2 things. Broken shielding in the ignition cable to the spark plug and MUCH MORE NOISE coming from the Koolflight Ultimate BEC than i would ever have imagined it could make. I put a 4.8 volt nicad on the ignition and threw off the Lipo and BEC i was using for the ignition before and all issues were gone. WOW! Finally!

The engine overheating seems to have just simply gone away after 2 changes.
a) switched to 690mm V-blades from the SAB 710's
b) richened up the high mixture just a tad and installed a zimmerman muffler.

This zimmerman muffler ROX! I got about 150 more rpm even with the engine a bit rich and no overheating problems. Its also VERY quite and gave me a VERY noticable increase in power. No discernible bogging in short full pitch climbouts which was there before. The engine just seems to run MUCH Better.

Im through my first gallon now on this thing and have started in on my 2nd with about a 40:1 mixture of Aspen 2T and a bit of extra oil added. I ran the first gallon at 33:1

The vibration seems to have been caused by the old muffler which would keep coming slightly loose and then because of its mass would cause the whole heli to shake as it moved around a bit. This is only speculation on my part but after changing the muffler the vibes are gone.

The engine is getting more and more power the more i run it and i think its going to be a keeper. Its still a bit early to tell because this is only my FIRST TROUBLE FREE DAY with the thing. However im cautiously optimistic about this heli - about it being finally reliable and also about the power im getting from it. It has, without a doubt, noticeably and considerably more power than a predator gassor with a zenoah 23. If this is because of the weight or because the engine simply is performing better i dont really know yet.

Anyway thats the latest update.

A day without sunshine is like, well, night.

04-22-2006 Over year old.

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AceBird
Elite Veteran
Location: Utica, NY USA

Quote

The engine overheating seems to have just simply gone away after 2 changes.
a) switched to 690mm V-blades from the SAB 710's
b) richened up the high mixture just a tad and installed a zimmerman muffler.

This zimmerman muffler ROX! I got about 150 more rpm even with the engine a bit rich and no overheating problems. Its also VERY quite and gave me a VERY noticable increase in power. No discernible bogging in short full pitch climbouts which was there before. The engine just seems to run MUCH Better.
-------------

without a doubt, noticeably and considerably more power than a predator gassor with a zenoah 23.

There is a whole lot about your comments I don't understand ...
If you went to shorter blades you cut the torque requirement and that will surely yield higher RPMs but not higher horsepower.

If you can't swing 710's you haven't matched the HP of the Zenoah let alone do better. Put a set of 500's on it and you will never bog, but you might not get off the ground either. Having so many problems and doing several different things to the heli it is hard to predict what actually solved what problem if any at all. You may have just accepted a compromise to make the heli flyable.

Ace

Ace
What could be more fun?

04-22-2006 Over year old.

AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Ace,

Good point and well taken. You could be right and to be honest i dont know exactly what has caused the overheating issue to go away since i made several of these changes all at once. Its really hard to say especially coming from me who has never owned a fuel heli before. Im STILL on a pretty steep learning curve when it comes to a fuel based power system.

When i say it has more power than a Predator with a z23 i simply mean that visually my machine climbs faster with less bogging than the aforementioned and with actually a bit less headspeed and definetly smaller blades. It also just seems to be in general much "lighter" in the air and responds quickly and with authority when pumping pitch. I would, in a very general sort of way, call this more power but this also could just be attributed to my machine being lighter than a Pgasser with a z23 which just would mean a better power to weight ratio. Keep in mind im new to these things so much of what i say may seem confusing since its still, to an extent, confusing to me as well!

Quote
There is a whole lot about your comments I don't understand ... If you went to shorter blades you cut the torque requirement and that will surely yield higher RPMs but not higher horsepower.

Would a tuned zimmerman pipe yield more horsepower? Could i also just be seeing the engine yielding better performance as it breaks in more ?

Quote
You may have just accepted a compromise to make the heli flyable

Good point and very possible as far as i know but thats not far yet

A day without sunshine is like, well, night.

04-22-2006 Over year old.

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FLYINFOOL
Veteran
Location: Cudahy, WI

Glad to here your making progress and that the over heating issue is gone for now.

I don't know the head dimensions of a Pgasser, but for instance the Stinger 90 head is almost 40mm bigger (blade bolt to blade bolt) than a Fury head. So 690mm blades on a Stinger will give the same effective disk area as a Fury with 710mm blades.

Jeff Borowski
Gohbee Field Rep
0133TD

04-23-2006 Over year old.

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PaulH-MA
Veteran
Location: Boston, MA

Quote
The lockouts were 2 things. Broken shielding in the ignition cable to the spark plug and MUCH MORE NOISE coming from the Koolflight Ultimate BEC than i would ever have imagined it could make. I put a 4.8 volt nicad on the ignition and threw off the Lipo and BEC i was using for the ignition before and all issues were gone. WOW! Finally!

Were you using the UBEC on the iginition or on your receiver? The last I knew, ignition systems didn't play well with switching regulators. If you really want to use lithium batteries, I think you're limited to a 2s pack and a linear regulator in this situation.

--Paul

TREX 450
Bergen Intrepid Gasser x2

04-23-2006 Over year old.

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11863 views

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Gohbee Aviation Stinger 30-90 > Gohbee / TZ / Raptor 90 Heli with BME modified G90 Gas Engine

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