RunRyder RC Helicopter Topic - Highest safe headspeed in a Predator?

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Gasser Model RC Helicopters > Highest safe headspeed in a Predator?

Manol
Senior Heliman
Location: Hermosillo, Sonora, Mexico

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Hi to all.
I have not found any information regarding the fastest headspeed that can be run safely in a Predator NX/SE with full metal head, SG720 FAIs. Engine is a Zenoah Hanson 260PUH, ratio is stock at 5.86, and I´m using the GV1 and stator gator.
Currently highest I´m using is 1910, I would like to run 2000 or slightly higher but don´t know if this is safe.

Thx.

10-28-2009 08:15 PM

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kogibankole
Veteran
Location: albuquerque

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I ran a plastic head past 1950 in mine at times with no issues at all. My biggest concern would be the thrust brearings. I think running these big blades puts a lot of pressure on them. Does anyone have data about them?

if im not blade bogging youll find me pack puffing

10-28-2009 08:51 PM

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Techflyer
Heliman
Location: Palm Bay, FL

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For about 8 or 10 flights I ran my Predator at 2000.
This was when I first installed the Hanson 3D Max.
I was using the stock gearing just as a test.
I used the metal head and was swinging 720 blades.
The flight response was quite amazing.
But...
While it flew and responded quickly, the helicopter as a whole did not seem happy.
The tail was definately spinning too fast.
While I could not put my finger on exactly what was happening, the helicopter lost that "Predator" feel that most of us really like.
It felt like flying a collection of parts and not a well integrated machine. (Really hard to put into words)
When I changed the gearing to bring the headspeed back to reality, I dissassembled the entire maching to see if I had damaged anything during the high headspeed tests. The only thing that I could find was the shims in the head had started to deform. They had become a bit "cone" shaped.
My conclusion was that while it was fun for a brief time, I would think that 2000 is not a good "long term" headspeed. I believe that the head and airframe will not withstand it for long.

10-29-2009 02:09 PM

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Carey Shurley
Veteran
Location: Orlando, FL

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Quote
Engine is a Zenoah Hanson 260PUH, ratio is stock at 5.86

5.86? All the documentation says its an 88/14 = 6.28 ratio

are you running a custom ratio or has the pinion gear changed to 15 tooth with the NX version

10-29-2009 02:47 PM

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AceBird
Elite Veteran
Location: Utica, NY USA

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Quote
Currently highest I´m using is 1910, I would like to run 2000 or slightly higher but don´t know if this is safe.

For how long? Every flexing member has a cycle life. The faster you go the shorter the life and not necessarily linear, more then likely it is exponential. No hobby related supplier will predict cycle life. I would guess that they have never tested their products to failure to even know a bench mark. The industry doesn’t demand it. But rest assured increased cycles and increased forces will shorten the life of every component.

Assuming you don’t reach the yield stress of the screw holding the grips or the blades on, I would suspect the blades to fail first. Raja has a sizeable number of flights / hours logged so maybe he can chime in as to how many hours he has on any one set of blades. Even though his head speed is lower you can calculate the number of cycles the blades have incurred. Then decide for yourself how much to de-rate the life for the higher head speed for blade replacement.

Ace
What could be more fun?

10-29-2009 07:12 PM

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Manol
Senior Heliman
Location: Hermosillo, Sonora, Mexico

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Techflyer, I think you´re right, it may just be too much for the components (blades and T Bearings mainly?)
Ace, I agree, it will degrade the lifespan of the whole.
And Carey, yes, my 6 month old kit came with a 15T as stock, 88T on the main gear.

Today I settled for 1900 in ST2 (Highest) and the heli just feels happy there, I´ll just leave my 2000 or higher thoughts behind

, no need since at 1900 it performed quite well.
I was just curious to find out if someone had used those higher speeds routinely and to know their impressions.

Thank You All

10-29-2009 08:24 PM

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Carey Shurley
Veteran
Location: Orlando, FL

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interesting, I agree with the change, just didn't know it had been made.

thank you

10-29-2009 08:34 PM

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Manol
Senior Heliman
Location: Hermosillo, Sonora, Mexico

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Carey!!!

My wrong, it IS a 14T pinion, I had my GV1 dialed wrong

I just re-checked it counting the tooths
Jeessseeees sorry

10-29-2009 08:41 PM

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Carey Shurley
Veteran
Location: Orlando, FL

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k, thanks. That makes more sense. Those little guys are hard to count!

10-29-2009 09:15 PM

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rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

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Head speeds

Well I was out flying my 1005 again today. Tried a faster rpm just to see how the motor behaves (1950 or 13,500 rpms on the motor) and while it spins it fine, when I climb out at full collective (12.5 degrees) it can't handle it.

I see no reason to run this fast and stress the machine. While there was no ill effects, I landed and turned it back down. In fact I tweaked the speeds a little and I feel I'm in the sweet spot. Here is what I have:

1540 in normal mode, 10661 rpms
1670 in idle up 1, 11561 rpms
1800 in idle up 2, 12461 rpms

Don't ask me how the engine rpms all ended in 61, its a coincidence!

At 1540 it seemed a litte quieter and smoother then 1560.
At 1670 the motor pulls forever at full collective (12.5 degrees) uncontested.
At 1800 its good for very fast forward flight FAI style.

I like those speeds and will stick with them. In most cases I fly the medium speed for 3D, with the other two reserved for fast forward flight/fai type maneuvers and the low speed for slow forward flight over the runway.

I did also try 1750 for the medium speed for 3D but felt the motor was running faster than needed for the type of flying that I was doing and opted to slow it down - my original setting was 1680 I went to 1670 to split the difference between low and high.

-=>Raja.

1005 Gasser, G26 3DMax++, 2205+ flights
Spectra-g, G26 3DMax, 870+ flights

10-29-2009 11:41 PM

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Manol
Senior Heliman
Location: Hermosillo, Sonora, Mexico

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I hooked the GV1 and stator gator today, Tomorrow I´ll test it, I think I´ve got the curves close enough and I´m aiming at:

Normal 1650 RPM´s / 10362 Engine RPM´s
ST1 1750 RPM´s / 10990 Engine RPM´s
ST2 1850 RPM´s / 11618 Engine RPM´s

Will try to stay below 1900 trying not to overstress the TBs and blades.

10-30-2009 02:06 AM

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AceBird
Elite Veteran
Location: Utica, NY USA

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Quote
the motor behaves (1950 or 13,500 rpms on the motor) and while it spins it fine, when I climb out at full collective (12.5 degrees) it can't handle it.

This is the fault of your gear ratio Raja. The motor has lost torque at 13500 RPM when you have put the most demanding load on it. In order to get the higher headspeeds you have to lower the ratio and limit the pitch of the blades which you can do because they are spinning faster. At higher headspeeds you are asking the heli to climb faster in a climbout so the engine is going to really bog.

Lower your ratio and lower your maximum pitch. It will be fine.

Ace
What could be more fun?

10-30-2009 03:27 PM

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rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

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That was just a test Ace to see how the engine ran at 13,500.

But absolutely the engine performs better at lower rpms at it has alot of grunt torque there to maintain the head speed. I could certainly reduce the pitch to unload it as well.

Basically if you want to get a higher head speed, you need to lower the gear ratio to maintain the engine rpms - totally agree.

-=>Raja.

1005 Gasser, G26 3DMax++, 2205+ flights
Spectra-g, G26 3DMax, 870+ flights

10-30-2009 05:47 PM

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Dr. Fibinotchi
Key Veteran
Location: Sioux Falls SD

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yea

You will be really happy when you get it in the air. The 1850-1900 head speed works soo much better in wind than lower head speed. Its not just for looks and gives the bird some agility especially like faster 4 point rolls look really nice and crisp.

-C

10-30-2009 05:57 PM

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rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

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As I sit and think about this

The interesting this is that the original 1005 GR of 6.43 we all know that it doesn't work as well for 3D flying.

You would think that the motor will perform excellent if you turn up the head speed, but from what I see and gather -- been so long since I flew that ratio, most people want to bring that GR up for better performance.

Cody are you still flying the original gear ratio in your 1005? And or if not what do you think of it compared to a higher ratio?

I'm at 6.92 and I think its pretty close to ideal. Maybe you want to go down a little from here for a faster head, but I would say not much.

Did you try 6.78 GR which is 95 tooth on a 14 tooth pinion? I forgot but thought you did. What's your thoughts?

-=>Raja.

1005 Gasser, G26 3DMax++, 2205+ flights
Spectra-g, G26 3DMax, 870+ flights

10-30-2009 06:50 PM

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Chris Bergen
Elite Veteran
Location: location

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Hmm, I'm running 6.43 in mine...

1900 HS, 12217 on the 3D Max motor..

Chris Bergen

10-30-2009 08:30 PM

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Dr. Fibinotchi
Key Veteran
Location: Sioux Falls SD

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hmm

I can't explain it very well so I will just post it. On this you tube video pay attention to the head speed loss. Forget about anything else. As I am making these figure eights you will see the blades visiblly go down in head speed. I am actually letting off the collective on the top end as the air speed is forcing down the head rpm in the turn. In a higher gear ratio like the 6.43's you have less head room. Head room meaning that even though you are sitting on the max torque of the motor running its like running in a larger gear on your bike up a hill. You still might produce the same power, but its harder and slows down you more than if you where at say 6.9. Its a tad more touchy when you are near the max power of the motor. So you have to take a tad more off the top end to keep the motor from pulling down more.

http://www.youtube.com/watch?v=r1gDHpLghdU

-C

10-30-2009 10:01 PM

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rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

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Chris

You should try 6.92, after all I'm using your drive gear so you have that in stock!!!!

Let me know what you think if you have a chance to try it. I agree with Cody you can spin it up more with the 6.43 but it bogs down more as its in a higher gear. By best explanation is this:

Driving you car in 4th gear, you approach a hill. You can go up the hill at 65mph and you'll feel pretty good but if you step more on the gas it doesn't accelerate that fast. If the hill it steep it may even lose speed even if you floor it.

In 3rd gear, you may go up the hill at 57mph (I got that as an exact ratio from 1900HS to 1680). At that speed if you step on the gas it will accelerate faster, and if the hill is steep it will not even lose speed.

Make sense? So one is geared for a higher variable speed head speed, and the other is geared for a lower head speed that is more constant. I prefer constant over variable - makes for a much better flyer for me.

-=>Raja.

1005 Gasser, G26 3DMax++, 2205+ flights
Spectra-g, G26 3DMax, 870+ flights

10-30-2009 10:24 PM

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Manol
Senior Heliman
Location: Hermosillo, Sonora, Mexico

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I'm one of the few around here using 720 blades instead of 710s. What am I missing?

10-31-2009 07:43 AM

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AceBird
Elite Veteran
Location: Utica, NY USA

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Quote
I agree with Cody you can spin it up more with the 6.43 but it bogs down more as its in a higher gear. By best explanation is this:

Yes, if you don't back off the pitch. If you raise the gear ratio all you are doing is lowing the speed that the heli can go. You see that effect in the climbout.

As I said before lower the gear ratio and manage the collective

Ace
What could be more fun?

10-31-2009 01:49 PM

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Gasser Model RC Helicopters > Highest safe headspeed in a Predator?

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