Will the 720 SL work on a 600 nitro?

[reimorei]

Hi! Anyone running a SK-720 on a T-Rex 600 Nitro? What level of vibes can I expect? Will the Self Level work fine on a nitro?

[Groucho_]

That's a bit like asking how long a piece of string is, isn't it?

It definitely has the potential to work and It will definitely work as an FBL controller without self leveling. The amount of vibrations would determine whether that would work or not...

[thefrog]

SL does work on a nitro - it works fine on my nitro. You have to play around with the mounting tape options until you find something that's absorbs enough vibes but it still firm enough. The condition of you nitro motor (e.g. bearings) has a big impact on vibes, as does the motor's state of tune.

[Doc-b]

What TheFrog said is the absolute Truth. I have A trex 600N. It works just fine. It took awhile. Playing with different mounting tapes, replacing engine bearing, Main shaft bearings. . But I finally got it. It was worth the trouble. This Forum will help you until You get it Right. You came to the right place.

[jperkosk]

IMHO you've got to be a nutcase to try, although it's possible if you dedicate enough time and effort to it.

I got close on my brand new TR700N but I could never get SK720 to last more than 2-3 min without deactivating SL function (infamous flashing red light). Tried 4-5 different mountings, and got the vibes down to ~10 peaks (always on vertical axis @ engine frequency). The heli was checked out a few times @ my club by our local heli guru and declared perfectly sane.

Stopped short of declaring my Align kit (that otherwise flew perfectly, the FBL part of SK720 doesn't seem to give rat's a$$ about any vibrations) a total POS and throwing all kinds of upgrades on it. Living @ 1900 m altitude means I run rather rich with the carb adjustment that would make it very lean on the sea level, so can't really go lean in fear of strangulating the lubrication; this may be part of the reason.

Felt SK720 underutilized on TR700N so moved it to the new home on 6HV where it's happy, and I'm in the process of installing MB on the nitro.

[thefrog]

Originally Posted by jperkosk

Living @ 1900 m altitude means I run rather rich with the carb adjustment that would make it very lean on the sea level, so can't really go lean in fear of strangulating the lubrication; this may be part of the reason.

I live at 1750m ASL and tune the motor to run between 90*C and 100*C. This is an OS 91 HZ-R regulated, the needles are very lean - about 1 1/3 turns on main and 1/3 on the mid. Lubrication isn't a problem but running the motor those 4 or 5 clicks rich would be a serious source of vibes. Check this comparison I posted a while back:

https://www.helifreak.com/showthread.php?t=396577

[desertstalker]

Originally Posted by jperkosk

I run rather rich

Which is the problem, you need to tune the engine correctly, there is plenty of oil in the fuel if your not overheating the engine.

[reimorei]

Ok folks, I´rather use my HC3-SX on the nitro as it doesn´t care about vibrations, and the SK-720 on my 550 Electric.

[fastflyer20]

Good choice, even with medium vibes, if you fly hard enough with a nitro, you can get it to disable SL, HC SL works great on any heli.

[SpeedTape]

Originally Posted by fastflyer20

HC SL works great on any heli.

I keep reading statements like this, but I have always wondered under what circumstances the HC self-leveling works well? Nobody ever qualifies their claims. They all sound subjective to me.

The rumors I have heard are that the Heli Command system works great so long as you stick to scale-like flying, but it doesn't do so well after prolonged periods of aerobatics, high-G turns or 3D.

Does anyone have any actual experience with this?

[fastflyer20]

I fly mild 3d, for Captain Rescue, it must boot up with the heli stable. Once activated, sometimes it will drift slightly left, right fore, aft but way better than I can correct under the conditions.

[jperkosk]

Originally Posted by thefrog

I live at 1750m ASL and tune the motor to run between 90*C and 100*C. This is an OS 91 HZ-R regulated, the needles are very lean - about 1 1/3 turns on main and 1/3 on the mid. Lubrication isn't a problem but running the motor those 4 or 5 clicks rich would be a serious source of vibes. Check this comparison I posted a while back:

https://www.helifreak.com/showthread.php?t=396577

Froggy, amazing difference !!! I knew there was one, but never suspected it was that much.

Originally Posted by desertstalker

Which is the problem, you need to tune the engine correctly, there is plenty of oil in the fuel if your not overheating the engine.

Easier said than done, my friend. In addition to 1900 m ASL I have frequently ambient temperature ~30°C. My temp alarm on DX8 goes off @ 110°C and I feel I'll fry the engine if I lean it any more. During the trials I was doing when the flashing red light would stay off for a couple of minutes the engine was reaching >125°C, so I had to make it a bit richer. BTW, using Coolpower 20%, seems (non-quantified non-scientific subjective feeling) to run cooler that Byron 15% I was using before, although Byron smelled better and smoked more.

[thefrog]

Originally Posted by jperkosk

Easier said than done, my friend. In addition to 1900 m ASL I have frequently ambient temperature ~30°C. My temp alarm on DX8 goes off @ 110°C and I feel I'll fry the engine if I lean it any more. During the trials I was doing when the flashing red light would stay off for a couple of minutes the engine was reaching >125°C, so I had to make it a bit richer.

That could have been the problem too - at 125*C it could have been too lean, maybe even experiencing detonation, hence the vibes.

Out of interest, we live in similar conditions - mid summer its typically low to mid 30s.

[desertstalker]

Not an expert on nitros, but could it be worth trying 30%? AFAIK its easier to tune the higher nitro fuels?

[jperkosk]

Water under the bridge. I have already pulled the SK720 off the 700N and moved it to a happier home, 6HV. Remaining 2 SK720s are waiting for their small electric heli builds. 700N gets a MB + CP2 (for bailout). It actually flies quite happily with the current tuning and fuel, on SK720 vibes weren't that bad at all overall and the heli guru at my club declared my 700N fit and sane. Engine temp stays where it should be, rarely passing 100°C mark.

Would try a gallon of 30% just out of curiosity, but with SK720 gone won't even have means to compare