Multi-blade setup help - RC Groups
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Oct 29, 2009, 05:29 AM
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TermIInatoR's Avatar
Help!

Multi-blade setup help


Hi Guys,

After I completed my MH68 Build I am now pondering on installing a multi-blade rotor head. Having NO EXPERIENCE at all in installing these, I was hoping I can get some guidance from you regarding things I need to know.

This is the multi-blade head I am planning to use...


These are the blades the manufacturer recommended...


This is the heli I am planning to install it to...


Questions that come to my mind are:
1. How do I set the pitch without the flybar?
2. Does the individual blades have individual feathering shafts as well?
3. Will it be stable to fly out of the box if I just remove my 2 bladed head and install the 4 bladed head (assuming the pitch and tracking is correct)? Or will I need to know other stuff?
4. Does the multi-blade rotorhead use the "standard" main shaft? (I have a couple of spares and would like to know if I need to stock up on a different kind)
5. Any NEW/special equiptment I need to reliably set this up?
6. I read somewhere that some people install gyros to stabilize the head Really? How does that work and do I need that?

Thanks for your input guys!
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Oct 29, 2009, 06:47 AM
Registered User
With one blade over the bom phase the head that when you give right ail
only the blade over the tailbom should move and give posetive pitch, when moving elev this blade shouldnt move att all, use the same pitchangles as for a flybarhead, test fly yours machine
and correct the angles after testflying, if the angles are to high your gone notice that
the heli wants to bump.usually you dont have to set higher pitchvalues with a multihead due more blades and liftcapacity, Multiheads gyros gives a moore relaxed flight and with a correct tuned gyro and heli it flies like flybar one, some use
it, some not

Good luck
Jack
Oct 29, 2009, 06:03 PM
Registered User
TermIInatoR's Avatar
Jack, thank you for your input. I've been reading up in other forums about setting up multi-bladed head and it seems more complicated than I first imagined. I hope to get more feedbak to maximize my success rate, or I'll just scrap the project if I can't get enough info before taking the plunge.
Oct 30, 2009, 02:10 AM
Registered User
Quote:
Originally Posted by TermIInatoR
Jack, thank you for your input. I've been reading up in other forums about setting up multi-bladed head and it seems more complicated than I first imagined. I hope to get more feedbak to maximize my success rate, or I'll just scrap the project if I can't get enough info before taking the plunge.
You can use a digital pitch gauge to setup ur pitch, draw a horizontal line on the wall or use the button on the head as reference. I use the button head method.
Oct 30, 2009, 02:47 AM
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TermIInatoR's Avatar
Quote:
Originally Posted by Adrianli
You can use a digital pitch gauge to setup ur pitch, draw a horizontal line on the wall or use the button on the head as reference. I use the button head method.
I see... but how do I zero the digital guage when the boom is inside the fuse? Maybe the button head is a good enough reference point.
Oct 30, 2009, 06:34 AM
Registered User
You can just eyeball zero pitch... fold the blade back and match it with the one 90° behind. That's normally good enough to get the tracking right. Then get the swash level, and phased correctly.

Now halve your aileron and elevator rates (for a start).

At that point it will be stable, and probably pretty easy to hover. However, forward flight will be pretty strange... expect it to roll HARD at transition into forward flight (in case you didn't know, this happens at a certain airspeed, about 2m/s for a 450). So take it up high before you try forward flight.
Oct 30, 2009, 09:39 AM
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TermIInatoR's Avatar
Quote:
Originally Posted by Andrew McGregor
You can just eyeball zero pitch... fold the blade back and match it with the one 90° behind. That's normally good enough to get the tracking right. Then get the swash level, and phased correctly.

Now halve your aileron and elevator rates (for a start).

At that point it will be stable, and probably pretty easy to hover. However, forward flight will be pretty strange... expect it to roll HARD at transition into forward flight (in case you didn't know, this happens at a certain airspeed, about 2m/s for a 450). So take it up high before you try forward flight.
Roll to what side? Any random side? As in like transitioning to an inverted hover by nudging full right cyclic? Thats scary... but nevertheless a very helpful information. Does that mean I cannot go over 2m/s?
Oct 30, 2009, 09:56 AM
Registered User
It'll go the same way every time, toward the retreating blade. It won't be full cyclic, but it might take 1/3 of your travel to hold it. It will probably also pitch up, not so hard. This effect comes on fairly slowly as the heli accelerates, it's not like a snap.

You can go over 2m/s, sure, it's just going to be pulling hard and you'll need to be right on top of your flying... but fullsize helis do this, and they're controllable.

This is why many pilots put cyclic gyros on multiblade and flybarless helis... it makes the handling easier to deal with. Or, you can learn to fly through the aerodynamics. I've flown my 4-blade T-Rex both ways, and to be quite honest, I'm not sure the cyclic gyro makes it easier... it's just a different problem (setting up the gyro instead of learning a different flying technique).

Since you have scale blades, rather than the standard 3D blades I'm using, it might be easier to fly than mine.

Still, if you get the phasing right, it will be possible to hover it (without wind!) with no gyro, and then you can take steps toward flying it quicker. If you don't like how it flies that way, you can then save up for an electronic flybar.
Oct 30, 2009, 10:34 AM
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TermIInatoR's Avatar
I see... seems like an awful lot of work with quite a few disadvantages compared to the current flybar setup that I have. It might look great with a quad-blade, but if my heli is going to be more difficult to fly then I'm beginning to have second thoughts about this.

The only advantage is in the "looks" department, and that doesn't even matter when it's flying because you can't see how many blades there are when the blades are spinning.

Thank you Andrew, your post was quite enlightening.
Oct 30, 2009, 04:19 PM
Registered User
Quote:
Originally Posted by TermIInatoR
I see... seems like an awful lot of work with quite a few disadvantages compared to the current flybar setup that I have. It might look great with a quad-blade, but if my heli is going to be more difficult to fly then I'm beginning to have second thoughts about this.

The only advantage is in the "looks" department, and that doesn't even matter when it's flying because you can't see how many blades there are when the blades are spinning.

Thank you Andrew, your post was quite enlightening.
Correct..but..if your seriously in scale and fly a scaleheli that are supposed
to have 3,4,5 or moore blades you dont want to go 2 blade with a flybar, as I wrote a correct tuned multiblade heli with a equal tuned multigyro like a sk 360 flies as good as a flybar one ,and as a static bonus the apperence is 100% better, I dont think a multiblade is harder to tune if as long you know what you are doing, if im not wrong this also correspont to a flybar one
Go for it!!

Cheers
Jack
Oct 30, 2009, 04:26 PM
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C Andrew Green's Avatar
Hi TermIInatoR,

I'm currently flying this: http://cgi.ebay.co.uk/ws/eBayISAPI.d...fvi%3D1&_rdc=1 Rush Heli 4 blade head / blades which appears to be the same head with a different top cap. I took the route of fitting it to the airframe in pod & boom form for ease of tinkering. As these heads have extended pitch arms you don't need to change either cyclic or pitch values, I literally lifted the 2 blade head/flybar/swash/mainshaft assembly off the airframe and fitted the 4 blader. (I had to drill an extra jesus bolt hole 2mm lower down in a new Align mainshaft) I adjusted the pitch by adjusting one pushrod and making all four exactly the same length and haven't had to touch the tracking. Being a flapping head it doesn't appear to exhibit any unpredictable FFF characteristics, in FFF you definitely have to fly the attitude of the model, if you release the forward stick it gently pitches up. I've looped it a couple of times with no surprises, it's fairly direct in the hover and you need to pay attention all the time until the blades are stopped when landing. I've only tried it briefly back in the Fuz and it really isn't happy being tail heavy (understatement). It's currently back in pod & boom till my lower Kv motor arrives as flying it governed at 70% can't be good for the ESC.
Oct 30, 2009, 08:09 PM
Registered User
Quote:
Originally Posted by TermIInatoR
I see... seems like an awful lot of work with quite a few disadvantages compared to the current flybar setup that I have. It might look great with a quad-blade, but if my heli is going to be more difficult to fly then I'm beginning to have second thoughts about this.

The only advantage is in the "looks" department, and that doesn't even matter when it's flying because you can't see how many blades there are when the blades are spinning.

Thank you Andrew, your post was quite enlightening.
True, you can't count the blades in flight (until you take a photo anyway), but you can see the flybar paddles, and they're not supposed to be there.

I have to say, with the cyclic gyro it handles BETTER than any flybar heli. And it's not unflyable without, I'd just hate to hear you crashed it because it rolled over and you weren't expecting that.

Scale helis ARE a lot of work, every way you look at it, but they're worth it. Multiblades look extremely cool during start up and shut down too.
Oct 30, 2009, 09:07 PM
Registered User
TermIInatoR's Avatar
Quote:
Originally Posted by C Andrew Green
Hi TermIInatoR,

I'm currently flying this: http://cgi.ebay.co.uk/ws/eBayISAPI.d...fvi%3D1&_rdc=1 Rush Heli 4 blade head / blades which appears to be the same head with a different top cap. I took the route of fitting it to the airframe in pod & boom form for ease of tinkering. As these heads have extended pitch arms you don't need to change either cyclic or pitch values, I literally lifted the 2 blade head/flybar/swash/mainshaft assembly off the airframe and fitted the 4 blader. (I had to drill an extra jesus bolt hole 2mm lower down in a new Align mainshaft) I adjusted the pitch by adjusting one pushrod and making all four exactly the same length and haven't had to touch the tracking. Being a flapping head it doesn't appear to exhibit any unpredictable FFF characteristics, in FFF you definitely have to fly the attitude of the model, if you release the forward stick it gently pitches up. I've looped it a couple of times with no surprises, it's fairly direct in the hover and you need to pay attention all the time until the blades are stopped when landing. I've only tried it briefly back in the Fuz and it really isn't happy being tail heavy (understatement). It's currently back in pod & boom till my lower Kv motor arrives as flying it governed at 70% can't be good for the ESC.
Very nice indeed. That's exactly the kind of look I was aiming for, and thaks for the reassuring comments. I don't think I have a budget for a cyclic gyro, so if ever I will just purchase the blades and the head and hope for the best (taking to heart all the comments you guys posted here). Negative and positive comments are always welcome. The last thing I want is to have a false sense of security that everything is going to be easy and ok, so I will be grateful for anything else that you guys want to share in addition to what has been said so far.
Oct 31, 2009, 02:52 AM
Registered User
TermIInatoR's Avatar
Quote:
Originally Posted by Jack Söderberg
Correct..but..if your seriously in scale and fly a scaleheli that are supposed
to have 3,4,5 or moore blades you dont want to go 2 blade with a flybar, as I wrote a correct tuned multiblade heli with a equal tuned multigyro like a sk 360 flies as good as a flybar one ,and as a static bonus the apperence is 100% better, I dont think a multiblade is harder to tune if as long you know what you are doing, if im not wrong this also correspont to a flybar one
Go for it!!

Cheers
Jack
You are absolutely right Jack. I have a bit of a perfectionist side (jut a bit) and that usually means having the mechanical setup as accurate as possible before resorting to tx adjustments. The result is that I use no subtrims (not that it's bad to have some, but I believe in using only a small amount AND only if absolutely necessary). So you see, I know I can do this, I just need some guidance. That is why I'm asking for advice from you kind folks. I know with your help I can do this. So I hope you all hang in there till I get my head and blades ordered,shipped, and installed. The local distributor tells me the next batch will come in around December, so I have more than enough time to collect information on do's, dont's, how to's, and everything else in between.
Oct 31, 2009, 03:04 AM
Registered User
TermIInatoR's Avatar
Quote:
Originally Posted by Andrew McGregor
...
Still, if you get the phasing right, it will be possible to hover it (without wind!) with no gyro, and then you can take steps toward flying it quicker. If you don't like how it flies that way, you can then save up for an electronic flybar.
I am not too keen on getting a cyclic gyro, if at all possible.

"Phasing" is something I have been reading on, but unfortunately I'm a bit slow on this matter and I couldn't quite understand it yet. In a 2 blade setup the swash and the mixing arms allow the blades to vary the pitch smoothly in unison with the swash tilt angle, creating more lift in one side and less in the other --to push the heli in any direction. I really thought this was exactly how a multi-blade was also behaving, only without the mixing arms. I never learned the term "phasing" in 2 blade setup, so I suppose this is unique to multi-blade setups only? If you can provide links to how I might understand this better then I'd appreciate it. I have already read up on in other forums but I am still puzzled...


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