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Futaba-RC . A Main Hobbies . Boca Bearings

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Thunder Tiger Raptors 30-90 - Imperio > RAPTOR 90 whats a good head speed for 3D on the 90s?
 
 
FenderBean
Key Veteran
Location: savannah, Ga

Been noticing a few things and was wondering if im using to much rotorspeed.
07-15-2008 03:23 PM
 
 
w12martin
Senior Heliman
Location: Matsuyama, Ehime, Japan

How much rotor-speed are you using?? How about the blades length?
07-15-2008 03:35 PM
 
 
Kinger
Elite Veteran
Location: Columbus, OH

Blade speed depends on the engine you are running and the gear ratio. Without that information it's hard to give any recommendations.
07-15-2008 03:39 PM
 
 
FenderBean
Key Veteran
Location: savannah, Ga

os 90 hyper non pumped and radix 710
07-15-2008 03:44 PM
 
 
w12martin
Senior Heliman
Location: Matsuyama, Ehime, Japan

1950rpm seems to be the rotor speed most used for 3D...
07-15-2008 04:01 PM
 
 
AMainMaker
Key Veteran
Location: Nappanee,IN

Make sure you have the 8.27 ratio though dont use that head speed on 8.45 .
Jason

Thunder Tiger Rep
Wildcat Team Pilot
Kong Power Team Pilot
Sw!tchGlo
CY Enterprises
07-15-2008 05:12 PM
HOMEPAGE  
 
 
w12martin
Senior Heliman
Location: Matsuyama, Ehime, Japan

AMainMaker: Which head speed do you suggest for 8.45 ratio and 710 or 690mm blades?
I just checked now my heli and I have 7.75 ratio! (93/12)
07-15-2008 05:21 PM
 
 
Raptile
Senior Heliman
Location: SLOVENIA-Logatec

8,45 (1800-1860rpm) 710mm blades
8,27 (1880-1950rpm) 690mm blades


T-Rex450SE, Raptor 50, Raptor 90 & FUTABA user =)
07-15-2008 05:30 PM
 
 
AMainMaker
Key Veteran
Location: Nappanee,IN

I am running my r90 at 1825-1850 at 8.45 with 710 radix.
Raptile is has a good spread. the power band of the engine can be pretty widespread if collective managment is used well. If you are a bogger then lower the head speed. if you are smooth as silk then crank it up. Dont know if this is a true theory but that is what I go by and tell people.

Thunder Tiger Rep
Wildcat Team Pilot
Kong Power Team Pilot
Sw!tchGlo
CY Enterprises
07-15-2008 05:53 PM
HOMEPAGE  
 
 
NEM3
Veteran
Location: New Lenox, Il

Are you guys quoting those numbers for the OS 91 SZ-H Hyper.

The SZ peak rpm is @ 15,000 rpm. With a max rpm of 16,000. If thats the case the numbers break down like this.

On the 8.27 Gearing
Headspeed - Engine Speed
1800 rpm - 14886 rpm
1850 rpm - 15299 rpm
1900 rpm - 15713 rpm
1950 rpm - 16126 rpm



On the 8.45 Gearing
Headspeed - Engine Speed
1700 rpm - 14365 rpm
1750 rpm - 14787 rpm
1800 rpm - 15210 rpm
1850 rpm - 15632 rpm
1900 rpm - 16055 rpm
1950 rpm - 16477 rpm


For starters the 8.45 gearing is meant for the YS 91 as it makes its best power at a lower rpm. And in my opinion the 8.27 is barely low enough for the OS 91SZ-H. This is also why all the M.A. guys are going nuts over the BW Stratus. 8.18 gear ratio.

You don't want to start off with a govenor setting that is already at or near the rpm limits of the engine. Just to have it overspeed another 500 or so rpm while flying.

You do want to set your govenor at a setting just above the max HP of the engine. That way it will bog into the torque range. The same concept is applied to tuned pipes on 2 cycle engines.

FWIW, I used to run my 91SZ-H cranked up to 1950 on the 8.27 ratio. After running the numbers I decided to turn it down to 1850. And I couldn't be happier. The engine runs better, longer and stronger than before. And flips are rolls are just barely slower. For the difference it made I would just buy lighter blades.
07-15-2008 07:50 PM
 
 
w12martin
Senior Heliman
Location: Matsuyama, Ehime, Japan

Any idea about 7.75 ratio (93/12) Engine rpm and Rotor rpm relations?
07-16-2008 02:03 AM
 
 
w12martin
Senior Heliman
Location: Matsuyama, Ehime, Japan

I found it... 7.75 ratio: head speed 1950rpm, about 15100rpm.
07-16-2008 02:58 AM
 
 
NEM3
Veteran
Location: New Lenox, Il

I think the 7.75 is to low for a couple of reasons. For one, your barely in the peak hp band. And the ratio is possibly so low that you losing quite a bit of the mechanical advantage of gearing. Something closer to 8.00 would be much better.
07-16-2008 04:12 AM
 
 
AMainMaker
Key Veteran
Location: Nappanee,IN

The raptor is capable of a 7.91 ratio. I used it for a little while and the head speed is amazing. I did however use it with a YS so I dont know if my findings are kosher for this test but it doesn't hurt to try it.
Jason

Thunder Tiger Rep
Wildcat Team Pilot
Kong Power Team Pilot
Sw!tchGlo
CY Enterprises
07-16-2008 04:45 AM
HOMEPAGE  
 
 
w12martin
Senior Heliman
Location: Matsuyama, Ehime, Japan

NEM3: Could you explain why using 7.75 ratio I'll be out of the peak hp band? If I set the head speed to 1950rpm (engine rotate at 15100rpm) don't you think this is very near to the peak range?
Also...what kind of mechanical advantage of gearing I'll be loosing if I use 7.75 ratio?
Ahh... just as a comment... My heli is a Bravo 90. The kit comes with 93 teeth main gear and 12 teeth pinion.
Thanx in advance!!
07-16-2008 05:02 AM
 
 
NEM3
Veteran
Location: New Lenox, Il

I didn't say your not in the peak power band. Just so close to the bottom end of it. I didn't mean to upset if that is the way it was taken. To be honest I would love to be able to dyno all the motors available to see exactly what kind of power bands they do have. Then we could start arguing about gear ratio's.

As far as the mechanical advantage comment. The higher you go in gear ratio the more torque your power plant will make at the rotor head. The lower you go, the more your power plant has to make the torque.

For example. And these are not even close to exact numbers. You have to figure in drive train losses.

You have an OS 91SZH that produces ~14 in-lbs of torque @ 15000 rpm. (3.3hp * 15000rpm)

You running a gear ratio of 7.75. So at the rotor head you have to ability to deliver 108.5 in-lbs of torque at 1935rpm headspeed.

I am running the same motor at a gear ratio of 8.27. So at the rotor head I have the ability to deliver 115.78 in-lbs of torque at 1813rpm headspeed.

To add to your problem. You are spinning your main gear/tail gear and tail rotor that much faster, which takes energy to do. Along with spinnning your blades and paddles 100rpm faster which again takes energy to do. The bottom line is that I have the ability to deliver more power at my rotor head than you given the same exact power input.


One thing I want to say is that I am not trying to say it won't work. I was originally posting about the suggestions to run that kind of headspeed on the 8.45 and 8.27 gear ratio. But I would feel more comfortable with a head speed of 2000rpm on a 7.75 gear ratio. But 90's aren't supposed to be run at that, so we get by with 1950

7.91 sure does sound promising. Think I will have to look into that. Thanks AMainMaker
07-16-2008 06:19 AM
 
 
w12martin
Senior Heliman
Location: Matsuyama, Ehime, Japan

NEM3... Thank you very much for your explanation!!!
07-16-2008 06:47 AM
 
 
NEM3
Veteran
Location: New Lenox, Il

You bet, just here to help
07-16-2008 06:49 AM
 
 
FenderBean
Key Veteran
Location: savannah, Ga

you know theres way more to this than I ever thought, maybe this is why I cant seem to get over the hump im in.
07-16-2008 02:33 PM
 
 
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Thunder Tiger Raptors 30-90 - Imperio > RAPTOR 90 whats a good head speed for 3D on the 90s?
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