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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › General Questions of OSGT15 Mark 2
04-02-2020 04:34 AM  11 months ago
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rrApprentice

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General Questions of OSGT15 Mark 2
Could someone give me some general tips. I might want to consider this in my new RAVE ENV 90 build. Do I need to change fuel tank/ plumbing , gear ratios or are these just direct replacement of say an OS 91 ? Also do they run on unleaded fuel of 25:1 like a weeder? Thanks
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04-02-2020 05:17 PM  11 months ago
ticedoff8

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Morgan Hill, CA. USA

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There are a few versions of the GT15. If you are headed in this direction, get the GT15HZ-II (not the older versions).

In general, the GT15HZ-II (or the older GT15HZ) puts out about the same power as a well tuned, modern OS 55HZ-R or YS 60SR.
If there were a OS 61 still on the market, it would be closer to those.

The GT15HZ works well in 550 / 600 heli with modifications - not so well in a 700 size. Gasser conversions for 700 size would typically use a 30cc motor (the GT15HZ is 15cc). If you plug a GT15HZ-II into a 700, the engine will be running at 100% throughout the flight and still acting like an under-powered 700.

Gas Powered Heli has mods and upgrades that are proven to help with the reliability, cooling and adds a little power.

The GT15HZ-II has some changes that have fixed a few problems from all the previous versions of the GT15.
A newer head for better cooling, changed back to the Walbro carb and changed to a crankshaft with a more standard threaded "snout" for mounting a more standard flywheel / fan / clutch.
The changes help with reliability, but they don't really add power.

OS recommends the 50:1 (3%) oil to gas but for long life you need to get closer to 10% oil (12 oz oil to 1 gal gas = 10:1).
And, the thinner the oil the better.
Red Line 2T or the Morgan fuel that is used in their Cool Power is recommended.

For the Rave 90 (or any nitro powered heli being converted to gasoline) - you will need to change all the fuel lines to fuel line tubing that is meant for gasoline. That includes the bung, the clunk and the tube inside the tank.
The stuff supplied with the kit will melt when you run gasoline through it.

I'd start here: https://www.helifreak.com/showthread.php?t=853987
And, Carey from GPH has this OS GT15HZ-II guide that may be helpful:https://drive.google.com/open?id=19...qkO3Sq16dydTRC5
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04-02-2020 06:23 PM  11 months ago
Rojoalfa

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Very good explanation.

You must consider some warning on electronic due to...

... VIBRATIONS...

Take care of:

1.FBL controller reinstalation.
2.Throttle servo.
3.Threadlock everywhere.
4.New liner or new clutch bell on clutch system.
5.Walbro's needles adjustment are quite sentitives on this OS15HZ.
6.Electromagnetic interference.

/
Saludos cordiales,
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04-03-2020 07:26 PM  11 months ago
ticedoff8

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Oh... one more thing:
Also do they run on unleaded fuel of 25:1 like a weeder?
You cannot run any of the 2-stroke motors on straight gasoline. They will all need a fuel / oil pre-mix.
And some will use the Colemen lantern (aka: white gas) fuel as a base instead of unleaded pump gasoline.
It still needs to have oil mixed in, but some say it smells better that pump gasoline.
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04-04-2020 12:36 AM  11 months ago
Dyehard

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I've switched over to Crown white gas with 28% oil. It does smell much better, close to what lighter fluid used to smell like and not very strong at all. Crown is available at Walmart and is $4 cheaper per gallon than Coleman. My JR 260Z/230Z is running at least as smooth, if not more smoothly, on the white gas than it did on a 28:1 gasoline/oil mix.Allen Dye
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04-18-2020 02:39 AM  10 months ago
Rojoalfa

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We all appreciate you may post some pics...

A glow to gasser conversion is a complete different situation.

Even, your starter motor/battery pack need to be consider for an upgrade.

Running Temperature... An issue you must consider.
Check for enhanced fan... Metal.

/
Saludos cordiales,
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04-26-2020 12:29 AM  10 months ago
RM3

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Killeen, Texas - USA

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The OS 15gt...

Is to be considered an eccentrics engine... and for expert tuners.

This engine is not recommended for anyone that is not meticulous about tuning and maintenance nor one that prefers to fly any harder than light sport. In addition the engine can easily get overheated so any temperature monitoring system is highly recommended.

My personal opinion is that this is one engine your garden variety helicopter flyer should avoid
showing a preference will only get you into trouble, 90% of everything is crap...
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04-26-2020 01:15 AM  10 months ago
Rojoalfa

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It is hard to say but that is correct.

Walbro carb is too big so needle adjustment is happen to be very difficult. One "click" is nothing but two is a lot!

Most of the time, motor is running like burning no matter what you do... 100-130 C...

If you are lucky, you can have 60 flights with this motor... With several overheating in between... No more than that.

/
Saludos cordiales,
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09-19-2020 03:12 PM  5 months ago
keron

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Miami

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I have an osgt15hz that i modified the sharft to fit in actrec 600 let me know if you interested it brand new, also the clutch , hub and fan.
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09-20-2020 01:49 AM  5 months ago
Rojoalfa

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Infarcted Do I need to change fuel tank/ plumbing , gear ratios or are these just direct replacement of say an OS 91 ?
/
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Very nice explanation above!!!

From glow, you do need to convert it to handle gas changing stopper, tubings, clunk, etc.

You don't need to change the mechanics.

And, this is not a conversion from your class 90 to 90 gasser.
With this motor you are going to get some sort of strong class 50 helicopter but heavier and lazy like a Cadillac.

Because of the bolt pattern, it doesn't fit on a regular class 50 heli so that is why you need the class 90 or series 700 to install the motor.

Tuning the carb... Well... It is very sensitive. I hope new version handle better the temperature but it run very hot. 130 Celsius degrees... Very hot no matter what you do with the needles.

Main blades... That is the only mechanics you need to change.
It flies very good with a 600-620 mm main blades. Don't need to change the boom.

With the older version, you got aprox. 60 flights without problems, then the motor dies and need to replace piston ring. Very bad.
IMHO, you better run this motor with more 2T oil than spec.

Take care of Fan shroud instalation.
The motor doesn't cool well on raptors, trex... And some "home made" assembly may be required.

I would like to tell you something... Don't do that.

/
Saludos cordiales,
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10-18-2020 09:24 PM  4 months ago
kenneth8

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USA

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keron I have an osgt15hz that i modified the sharft to fit in actrec 600 let me know if you interested it brand new, also the clutch , hub and fan.
Does anyone know the stock shaft Diameter to fit different hub and fans? I could not find it in the manual , Thanks.

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10-18-2020 11:24 PM  4 months ago
keron

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Miami

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I think its the same as a normal os 91 and thundertiger 91 sharft
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10-19-2020 01:23 AM  4 months ago
Rojoalfa

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Front bearing...

3/8 x 7/8 x 9/32

Shaft 3/8"...

/
Saludos cordiales,
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10-19-2020 03:51 AM  4 months ago
kenneth8

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USA

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apprecite it. Is 9.5MM a common size in Nitro kits? Where the fan bolts onto the engine crankshaft? Wondering if this engine will bolt up to current 700 class nitro kit fan/clutch out there in production. Keron above had to modify the crankshaft to fit his kit. So i guess it was not 9.5MM Thanks
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10-19-2020 03:52 AM  4 months ago
keron

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Miami

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Yes it will.
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10-19-2020 07:25 PM  4 months ago
kenneth8

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USA

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apprecite it, so stock crankshaft 9.5MM then anyone know why the gas powered thoughts GT15HZ is sold with an 8MM crank shaft?
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10-20-2020 03:46 AM  4 months ago
Rojoalfa

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I can't follow your "actrec 600" helicopter manufacturer... Or you mean trex 600?

Difficult yo know why you modified crankshaft diameter.
Trex 600 fan Hub, fix with no issue...

/
Saludos cordiales,
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10-20-2020 11:59 AM  4 months ago
keron

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Miami

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Sorry trex 600 helicopter.
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10-20-2020 12:02 PM  4 months ago
keron

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Miami

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Yes it fit but the sharft on the osgt15 is a bit longer than the normal fan hub, so i have was to drill into the hub a further 5mm so it will fit on the drive washer also the sharft was cut to avoid bouncing the starter sharft
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10-20-2020 01:59 PM  4 months ago
Rojoalfa

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Yes! That is the sort of things you need to do with this type of asiatic kits.

Modify hub and other things is easy but never intend to cut, drill the motor crankshaft unless you are making a "Frankenstein" heli.

/
Saludos cordiales,
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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › General Questions of OSGT15 Mark 2
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