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Scale Model RC Helicopters > 700mm Flybarless Scale Build with DIRECT DRIVE TAIL ROTOR ???
 
 
HS10
Senior Heliman
Location: Elk River, MN

My Posts This: Topic  Forum		Hi Folks

I want to build a scale 700mm Jet Ranger using a direct drive tail rotor...

I am thinking about using a motor in the tail with the tail rotor mounted directly...

If this is not possible then use a motor connected to a short shaft and a 90 degree tail (maybe a TREX 600 / 700) assembly...

This would permit a wide range of low rotor speeds without loss of tail rotor authority...

I also understand there may be some other benefits in term of power efficiently could be realized???

I envision a CC ESC set to GOV mode and a NEU motor... The tail rotor speed could be adjusted by radio or set by Castle Link...

Think it is feasible or bad brain fart...

Looking for some ideas on where to start???

Logo 14/24 (Agusta 109A-MKII) (MH-6 Little Bird) (OH-58A) Navy - Retired
10-08-2009 03:55 AM
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wilerbee
Senior Heliman
Location: Hong Kong

My Posts This: Topic  Forum		HS10,

Try talk to Peter Wales, he is using this system on his turbine 1/7th
scale Black Hawk. Go up to his website and look it up there. Sorry I don't have his website address on hand but he is quite easy to find.

Good Luck !
10-08-2009 04:41 AM
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Hoverup
Elite Veteran
Location: Gulf Coast

My Posts This: Topic  Forum		Very feasible HS-10. MiniCopter's latest Joker evolution uses two motors for a slamming' great 3D machine. A scale application should be a piece of cake. Component selection will be the long pole in the tent. Keep us posted on your progress

Cheers - Boyd
AMA 80393
IRCHA 3355
Major USAF
Retired
10-08-2009 04:43 AM
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WrenFlyer
Senior Heliman
Location: Aberdeen, MS USA

My Posts This: Topic  Forum		I think Peter had problems with all of that mass placed back on the tail boom, I've been known to be wrong though.....

Alan Haney
10-08-2009 05:16 AM
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WrenFlyer
Senior Heliman
Location: Aberdeen, MS USA

My Posts This: Topic  Forum		Here's where you can see more of Peter's work:

http://scalehelicopters.org/

Go down to FRH Blackhawk Part 3 for the tail drive system.

Alan Haney
10-08-2009 05:24 AM
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Rodan
Senior Heliman
Location: Prescott Valley, AZ

My Posts This: Topic  Forum		Placing a motor at the tail will likely cause balance problems... I think that's what Peter ran into.

The new Joker is a step in the right direction... with the motor on the mechanics, there's no balance issue, and there are lots of advantages to a separate tail motor.

I really like the TRex 600E as a basis for scale machines, but the low T/R drive ratio limits what you can do, especially with heavy rotor discs and low headspeeds.
10-08-2009 06:55 AM
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stanc
Key Veteran
Location: Conroe, TX

My Posts This: Topic  Forum		Here are some pics of what misskimo did to drive the tail with a motor, he used the old style closed tail box from a MA heli. Something like this could possibly get your motor up to the mechanics for better CG.



Stan
Logo 500
Ion X2
eStratus
eAvro90
10-08-2009 11:30 AM
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WrenFlyer
Senior Heliman
Location: Aberdeen, MS USA

My Posts This: Topic  Forum		I agree with you guys, adding the motor at the frame would be the way to go. You could have super low HS and still have great tail authority.

Here's video of Misskimo's Joker flying at our house.

It's cool doing an Auto and hearing the tail rotor at full RPM.



Alan Haney
10-08-2009 02:46 PM
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HS10
Senior Heliman
Location: Elk River, MN

My Posts This: Topic  Forum		I visted the Peter Wales website, great help thanks... The best efficiency would be a motor in the tail... The weight will be an issue for sure...

I would like to try the simple motor in the tail first, I hope I can overcome the weight issue...

What would be a reasonable tail rotor speed range for a 700mm ship???

Does this look like a resonable starting point???

A NEU 1105 3.5Y & CC35 & 3 cell LIPO would give me 33192 rpm

The 1105 is 1.2" long and weights about 2.3 oz...

The width of the tail boom pod is 2"...

Is there a smaller motor that might work??? The small Hacker and Scorpion motors look like a possibility also...

Logo 14/24 (Agusta 109A-MKII) (MH-6 Little Bird) (OH-58A) Navy - Retired
10-08-2009 03:00 PM
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jack726
Veteran
Location: Cerritos California

My Posts This: Topic  Forum		I read somewhere that 4500 rpm turned out to be the proper range.
10-08-2009 04:21 PM
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WrenFlyer
Senior Heliman
Location: Aberdeen, MS USA

My Posts This: Topic  Forum		The Trex 700 has a tail gear ratio of 4.54

So.....2000 HS Equals 9,080 on the tail.

Alan Haney
10-08-2009 04:37 PM
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Jag72
Elite Veteran
Location: 20 minutes south of Boston Mass...

My Posts This: Topic  Forum		Contact CGBOLE here

He has a lot of experience with the direct drive tail also...he has a setup like that on his electric Synergy


Anthony

Esprit Model Flight Team
10-08-2009 04:39 PM
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jack726
Veteran
Location: Cerritos California

My Posts This: Topic  Forum		WrenFlyer is right. I had calculated the same speed, but when Peter Wales said it was 4500, I thought since he had used it in his Black Hawk it he must be right. I just went back and checked his site. He did say 4500 rpm but I just noticed he is running a 4 bladed tail rotor.

Sorry Jack
10-09-2009 12:23 AM
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cgbole
Key Veteran
Location: tulsa ok

My Posts This: Topic  Forum		Tail motor

Shouldn't be too hard to do. Just being willing to tinker is half the battle..

I tried it on the Synergizer because of the way the Hyperdrive installed in it. After we figure out what the normal tailrotor speed should be we'll be able to pick a power system. This does have a few draw backs for 3Dflying but the Aerial Photo guys seem to be having good luck with it.

Coming up with a coupling to fit the Trex input shaft shouldn't be too hard. Then you will need to fabricate a mount.




chuck

Magnito Chuck
ThunderPower
Esprit Model Flight Team
Synergizer
E T-700
10-09-2009 03:44 AM
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HS10
Senior Heliman
Location: Elk River, MN

My Posts This: Topic  Forum		UPDATE

Narrowing things down to a NEU 1905/12Y or 1907/9Y with fan (both special order versions)

If I use the existing 10S2P flight packs this would be in the 150-170 Kv range.

Looking at the Phoenix HV-30 ESC to drive it...

Do these numbers look reasonable driving a TREX 600 tail assembly?

Logo 14/24 (Agusta 109A-MKII) (MH-6 Little Bird) (OH-58A) Navy - Retired
10-28-2009 01:19 AM
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Experience RC . Heli-Max . Hobby Hut

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Scale Model RC Helicopters > 700mm Flybarless Scale Build with DIRECT DRIVE TAIL ROTOR ???
 
 
Peter Wales
Key Veteran
Location: Orlando Fl

My Posts This: Topic  Forum		Some facts about my experiments which may help you.

Mt Blackhawk fuse was all CF which is comparatively flexible. There was a large hole in the underside for the the tailwheel to mount in, about 6" log and 2" wide. This made the vertical fin IMHO weak to sideways oscillations and this made me a little nervous, but it proved to be strong enough.

My rotor speed was 900 rpm and working the gearing backwards dictated I needed a tail rotor speed of 4500 rpm. The tail rotor was a 17" diameter 4 blade unit.

If your headspeed is 2000 rpm and the gearing indicates a tail rotor speed of 10,000 rpm, then go for it. Thats what you will need.

I recommend you put your tail drive motor inside the frames and not at the tail, otherwise you will be adding a lot of nose weight to balance it out.

You need to compare the efficiency of the main gear/tail rotor drive gear to the efficiency of the electric motor to see if there will be any potential benefits and dont forget the added weight and complexity of the ESC amd motor and mount.

I had a good reason for doing it in my Blackhawk, are you sure you have?

Peter Wales
http://scalehelicopters.org
10-28-2009 02:09 PM
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Scale Model RC Helicopters > 700mm Flybarless Scale Build with DIRECT DRIVE TAIL ROTOR ???
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