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HomeScaleAircraftHelicopterScale Model RC Helicopters › Multi-blade heads & gyros???????
11-13-2005 09:59 PM  12 years agoPost 121
erichevy

rrVeteran

Zevenhoven The Netherlands

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Come on...you can do better than that,
Everyting except the weight of the Hughes has been spoken of!
3 bladed head
800 mm blades/ chord 62mm
weight is around 15 us pounds (6,8-7 kilograms)
Rotordiam. 1.80meter
Zenoah G230
Eric.

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11-13-2005 10:04 PM  12 years agoPost 122
AirWolfRC

rrProfessor

42½ N, 83½ W

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What is the weight and span-wise CG of your blades and the diameter of the blade bolt circle 7-7/8" (1.8M - 1.6M = .2M)?

With 1000 rpm, your tip speed comes out to 0.27Mach, about half of a 90 size pod & boom. That means that you have about 40% of the head inertia of a 90 size with 150% of the weight leaving you with only about 25% of the gyroscopic stability compared to a 90 size pod & boom.

That goes a long way to explaining the control vagaries. And that without a flybar or gyros. Yes, it's easy to understand why it's a hand full.

It looks like you are at a Cl of about 0.15 which is good for blade pitch of about 4º to 5º in a hover and an AoA of about 1.5º. Only thing missing is gyroscopic stability.

Wolfgang

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11-14-2005 12:16 AM  12 years agoPost 123
Sea King

rrApprentice

England UK

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Wolfgang

So
If I understand your Logic you are stating that a high head speed of around 1800 rpm will work much better than a 12 - 1400 rpm head speed on multi blades

If that is the case why do People like Century who sell multi blade heads have a warning sticker attached with them not to exceed x amount head speed ( and its nowhere near the figures that you keep quoting)

FYI scalers change the gearing to get a lower head when flying a multi blade head as it is more scale LOOKING and a hell of a lot better for the long term health of the heli and your nerves

Also dont forget that a multi blade head with the correct blade combination will give more lift than a two blade head .I so far havent seen you take that into account while youve been saying the head speed needs to be increased

Forget about true scale head speed as that will never happen but you can get the head speed to LOOK scale

Oh and by the by I also use the Heltronix mixer (won it on a raffle )and i opted to follow joels advice ( stupid not to really) and used CSM180 gyros and it works great

Sorry guy but when it comes to multi blade heads I'll follow the advice of Peter ,Joel, Emile and most any other person on here anytime before I will you

That being said I cannot and will not argue the figures that you keep quoting about tip speeds and mach etc as I really don't understand any of it and have no wish to do so

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11-14-2005 12:42 AM  12 years agoPost 124
Dr.Tim

rrElite Veteran

Mojave Desert

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My SUPER PUMA L2 weighs in at 26lbs. , Vario Gasser for Power, G230, OF 4 Bladed Head with 670mm Blades (OF Head is wider so you use smaller blades) 1250 RPM's on the head ...... Helitronix Mixer with a GY240 on the elevator. This setup flew real nice ......


Dr.Tim

From Simple minds come simple ideas! Approach Engineering

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11-14-2005 12:53 AM  12 years agoPost 125
Dr.Tim

rrElite Veteran

Mojave Desert

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Forgot to mention .........
I followed Peter's Advice and Won the Nationals this year because of it!! !!!!!

Dr.Tim

From Simple minds come simple ideas! Approach Engineering

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11-14-2005 02:55 AM  12 years agoPost 126
AirWolfRC

rrProfessor

42½ N, 83½ W

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So
If I understand your Logic you are stating that a high head speed of around 1800 rpm will work much better than a 12 - 1400 rpm head speed on multi blades
OK, you have it comming so here it is. You know, I'm getting real tired of you short sighted and long mouth types.

Obviously, you completely fail to see my logic. You're too busy over reacting and exagerating my comments and doing your best to twist them to suit your own position.

Do the world a favor and try to be realistic instead of jumping to conclusions. It's a shame you would rather attack than converse.
If that is the case why do People like Century who sell multi blade heads have a warning sticker attached with them not to exceed x amount head speed ( and its nowhere near the figures that you keep quoting)
You fail to comprehend that limit is for structural reasons only. Lets them make the parts from cheaper components.
Also dont forget that a multi blade head with the correct blade combination will give more lift than a two blade head .I so far havent seen you take that into account while youve been saying the head speed needs to be increased
It looks like the second part of my last post eluded you.
Sorry guy but when it comes to multi blade heads I'll follow the advice of Peter ,Joel, Emile and most any other person on here anytime before I will you
Again you make stupid assumptions. You think that I am trying to get you to take my advice. I don't want you to take my advice. Never did. Never want to. I only want you to be intelligent enough to do your own thinking. You seem to have a problem with that. Matter of fact, you seem to be proud of having others do your thinking for you.
That being said I cannot and will not argue the figures that you keep quoting about tip speeds and mach etc as I really don't understand any of it and have no wish to do so
All professionals that I know pride themselves on learning. You force me to ask, is the "Dr" title you use real? You seem to be proud of staying in the dark.
Dr.Tim
"From Simple minds come Simple Ideas"......
I wouldn't be too proud of that.

If this alienates you from me, then fine ! The comments you have spouted, make me allright with that.

It didn't have to be this way. But you made sure of that.

Wolfgang

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11-14-2005 06:55 AM  12 years agoPost 127
Sea King

rrApprentice

England UK

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OK, you have it comming so here it is. You know, I'm getting real tired of you short sighted and long mouth types.

Obviously, you completely fail to see my logic. You're too busy over reacting and exagerating my comments and doing your best to twist them to suit your own position.

Do the world a favor and try to be realistic instead of jumping to conclusions. It's a shame you would rather attack than converse.
/QUOTE]

You know me so well Sorry but if thats the impression that i am getting from your posts then perhaps ,,just maybe I am not alone in this and I am always open to conversation/debate

[QUOTE]You fail to comprehend that limit is for structural reasons only. Lets then make the parts from cheaper components.
I fully understand the reasons for the limit However from your posts it would appear in your advice to run higher headspeeds you tend to over look this rather important fact.. so why would we want these rather important pieces made of cheaper components
It looks like the second part of my last post eluded you.
not at all perhaps you could actually show where you have taken the time to assess the difference in lift between a two blade flybar and say a 5 blade multi...Giving me the angle of attack and pitch setting does not give me the difference in lift ( remember Its a bit over my head )
Again you make stupid assumptions. You think that I am trying to get you to take my advice. I don't want you to take my advice. Never did. Never want to. I only want you to be intelligent enough to do your own thinking. You seem to have a problem with that. Matter of fact, you seem to be proud of having others do your thinking for you.
Not at all I like to make my own judgment by finding out about the products like the Heltronix unit by listening to the people who make and actually use this system and compare it with what else is out there as for others doing my thinking for me
Some of these guys on here have forgotten more than I will ever know about multi blades so it would be rather churlish not to learn from their experiences and adapt it to my own style/standard of flying
All professionals that I know pride themselves on learning. You force me to ask, is the "Dr" title you use real? You seem to be proud of staying in the dark.
I think you have me confused with some one else

(Sorry Tim I'm not wearing any of your hats LOL)

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11-14-2005 01:20 PM  12 years agoPost 128
Dr.Tim

rrElite Veteran

Mojave Desert

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Before I get angry I will assume that comment was for someone else ... you see I have 5 girls and 4 boys , they often speak before thinking. I have a Ph.D. in Physics so if you want to attack that then lets rumble .... you will loose! As for my Friend Peter ... He is Very informed and is not afraid to pick up a Book and read. He knows what he is talking about, knowledge comes from mistakes made .... after all the years he has been building and flying helicopters I am sure he has made a few.

Lets talk about you! Why would you attack me for simply stating what my setup was and what I flew to not only WIN the nationals but IRCHA as well for the past 3 Years!

I think enough is said at this point and you should rethink yours. Have a great day!

Dr.Tim

From Simple minds come simple ideas! Approach Engineering

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11-14-2005 01:44 PM  12 years agoPost 129
Peter Wales

rrElite Veteran

Orlando Fl

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Eric
I think 1200-1250 on the head sounds good. 50% expo is usually what I will run, so you are on the mark there. It is a fact that the flybar and paddles dramatically reduce the effect of wind on the helicopter, thats one of the main reasons they are there, so you can expect it to bounce up and down a bit in the hover.

You can also try reducing the sensitivity to collective in the hover by putting an S in the pitch curve at the hover point.

Did you get to fly it around?

A gyro on the elevator will help the ballooning if you did, and you will find the controls feel a little different but by the time you have 3 or 4 flights on it you will be getting the feel of it.

It will never feel like a flybar heli though.

Peter Wales
http://scalehelicopters.org

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11-14-2005 03:22 PM  12 years agoPost 130
AirWolfRC

rrProfessor

42½ N, 83½ W

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I was trying to highlite some acedemic discussion, right from the start, but most, if not all, ASSUMED that I was trying to tell them what to do.

I really thought I was talking in a place that was occupied by intellligent people, but I have been convinced that it is full of sheep. Peope that don't do any thinking for themselves but are happy to have others do the thinking for them, just like sheep.

Dr. Tim, if you have all you say you do, then act like it !

I would be happy to continue but I get testy in the face of continuous attacks resulting from closed and defensive minds that keep jumping to adversarial conclusions.

Sea King,
not at all perhaps you could actually show where you have taken the time to assess the difference in lift between a two blade flybar and say a 5 blade multi...Giving me the angle of attack and pitch setting does not give me the difference in lift ( remember Its a bit over my head )
When it comes down to the individual pieces, I treat the rotor blades just like any other wing. In the case of a heli, I typically us the "average" velocity over the blades as that at 75% of the rotor span and figure the AoA (Angle of Attack) from there. Then the down-wash has to be taken into account to get to the blade pitch angle. The rpm and the down-wash velocity will give the exact angle to be added to the AoA for the blade pitch angle for hover.

When you get a lateral velocity (forward or sideways flight or a gust from any direction, you disrupt the down-wash. As you move into "cleaner air", the down-wash through the rotor disk will be less. This will force a change in the AoA making it increase even though the blade pitch angle has not changed. This will give more lift, which will make the heli rise just as if you gave collective. This is also refered as transitional lift. This has NOTHING to do with any kind of flybar. The effect is the same on flybar and flybarless helis alike.

Flybars and gyros deal only with pitch and roll, not collective.

It may LOOK like pitch control can help with the "bobing up" from a gust of wind but it won't. With a gust or lateral flight, the advancing blade will generate more lift and gyroscopic precession will cause a pitching up motion. The heli will still "bob up". You can compensate for the pitching with cyclic but only collective will fix the "bobbing up".

Wolfgang

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11-14-2005 03:48 PM  12 years agoPost 131
Dr.Tim

rrElite Veteran

Mojave Desert

My Posts: All  Forum  Topic

Then tell me what it is your looking for ...

Basic Aerodynamics,
Dysymmetry Of Lift,
Rotory Wing Planforms,
Blade Flapping ,
Airfoils in General,
Transverse Flow Effect ,
Airfoil Pressure Patterns,
Ground Effect,
The Relative Wind,
The Hover!
Total Aerodynamic Force,
Effective Translational Lift (ETL),
Centrifugal Force,
Retreating Blade Stall,
Gyroscopic Precession,
Settling With Power,
Drag,
Autorotative Flight,
Torque,
Loss of Tail Rotor Effectiveness (LTE),
(Airfoil) Angle Of Attack,
Dynamic Rollover,
Rotor System Rotational Velocities,
Rotor Blade Hazards


I will be more than happy to "Quote" you anything you need from the
Army Field Manual FM 1-203, Fundamentals Of Flight, 9 September 1983
All of my Training came from the Navy. Lets Roll!

Airwolf
I have not Attacted you once!!! But if you continue attacking me things will as you say get testy!!

Dr.Tim

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11-14-2005 04:06 PM  12 years agoPost 132
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

So
If I understand your Logic you are stating that a high head speed of around 1800 rpm will work much better than a 12 - 1400 rpm head speed on multi blades
Bad assumption. You start out like that and then you wonder about the consequences ?

BTW, nice vocabulary. And you can memorize stuff too. Now if you could only come across like you really knew what it all meant.

After all, you did say
That being said I cannot and will not argue the figures that you keep quoting about tip speeds and mach etc as I really don't understand any of it and have no wish to do so
Some of my training came from the USMC, HMH-461, CH53C & CH53D. '69 to '72

Whenever you're ready to start over, so will I.

Wolfgang

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11-14-2005 04:22 PM  12 years agoPost 133
Dr.Tim

rrElite Veteran

Mojave Desert

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I never said those quotes? but, a fresh start is a good start.


Dr.Tim

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11-14-2005 04:30 PM  12 years agoPost 134
AirWolfRC

rrProfessor

42½ N, 83½ W

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I would like a fresh start . . . all the way around.

As for the quotes, go back and look.

Wolfgang

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11-14-2005 04:49 PM  12 years agoPost 135
Dr.Tim

rrElite Veteran

Mojave Desert

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I did ... I think they belong to Sea King.


Dr.Tim

From Simple minds come simple ideas! Approach Engineering

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11-14-2005 04:56 PM  12 years agoPost 136
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

I stand corrected. My apologies for that.

Wolfgang

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11-14-2005 05:14 PM  12 years agoPost 137
Sea King

rrApprentice

England UK

My Posts: All  Forum  Topic

ROFLMAO

Yes their mine

Wolfgang
Thank you for the explanation

Now if you would please answer the following I'd be obliged

Stock Predator gasser with 231PUH wet weight 20lbs
I would like to Run the Century 5 blade IDG head ( you pick the blades 690/670)What gearing would you recommend and what head speed would it give me


Roger

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11-14-2005 05:24 PM  12 years agoPost 138
pulsar110

rrApprentice

USA

My Posts: All  Forum  Topic

So Wolfgang. Instead of going to this long explaination,
When it comes down to the individual pieces, I treat the rotor blades just like any other wing. In the case of a heli, I typically us the "average" velocity over the blades as that at 75% of the rotor span and figure the AoA (Angle of Attack) from there. Then the down-wash has to be taken into account to get to the blade pitch angle. The rpm and the down-wash velocity will give the exact angle to be added to the AoA for the blade pitch angle for hover.
When you get a lateral velocity (forward or sideways flight or a gust from any direction, you disrupt the down-wash. As you move into "cleaner air", the down-wash through the rotor disk will be less. This will force a change in the AoA making it increase even though the blade pitch angle has not changed. This will give more lift, which will make the heli rise just as if you gave collective. This is also refered as transitional lift. This has NOTHING to do with any kind of flybar. The effect is the same on flybar and flybarless helis alike.
Just tell the man, by the term what his heli is doing. There is a specific term for this whole chain of events. Most of us know it and those of us that are around full scale deal with it everytime we fly.

Fly it like its a rental...

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11-14-2005 05:24 PM  12 years agoPost 139
AirWolfRC

rrProfessor

42½ N, 83½ W

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Heli_jack,

I take it you'd rather keep up the discourse. Are you happy now?

Wolfgang

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11-14-2005 05:43 PM  12 years agoPost 140
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

Sea King,

For the purposes of lift, 5 blades lets you use the shorter blades and lower rpm, under 1000 even.

But those items are exactly what makes it a hand full to fly.

The Predator comes with 88 / 15 = 5.87 gearing. Trying to run the motor at 5870 rpm would be "interesting", if not questionable to say the least.

Woflgang

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HomeScaleAircraftHelicopterScale Model RC Helicopters › Multi-blade heads & gyros???????
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