Mechanical or electronic? - RC Groups
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Feb 01, 2013, 09:55 AM
Registered User

Mechanical or electronic?

I am thinking of building a multi blade 450. 4 or 5 blade.
I was considering setting it up all mechanic (90* phasing). and flying it like people used to before 3 axis gyros came out.

I LOVE a challenge and get great satisfaction from having mastered a difficult activity.

what do you think?
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Feb 01, 2013, 11:53 AM
A man with too many toys
If you have more than 2 blades you need an adjustable phase head if you want to go 100% mechanical because 90 degrees won’t work.

The way they flew scale with no flybar before electronic controllers was to set it up with very low cyclic and collective pitch. They used –2.5 to 7 (some were as low as +5) collective pitch. I don’t remember the cyclic angles but I think it was only a couple of degrees. If you set it up like a modern 3D helicopter it will instantly go out of control.

That was with large scale helicopters with lots on inertia to help stabilize them. With a 450 it’s just doing to be that much harder to fly.

You will also need some very heavy blades to increase stability. Scale guys sue flat bottom or semi-symmetrical blades.

My advice is to get a SK540 and load the scale code that's designed for multi rotor helies – you will be a lot happier with the results.

Feb 01, 2013, 12:01 PM
Rocket Programmer
jasmine2501's Avatar
I think you're confusing two sorta related things, but I'll take a shot at this...

There's two concepts here - control mechanism, and stabilization. Your control mechanism can use mechanical or electronic mixing - this is how you are able to control both collective and cyclic from a single control point, the swash plate. Mechanical mixing is when the cyclic servos sit on a tray that moves up and down with the swash plate when the collective changes - each servo controls one axis, roll, nick, and collective. In electronic mixing, all three servos are involved in all three actions - collective change is caused by moving the servos up and down together and cyclic is caused by moving them differently to tilt the swash. So, that's your mixing options - you will almost certainly want to choose electronic mixing so you don't have to go find an old kit that isn't made any more. Raptor was the lone hold-out using mechanical mixing up until a couple years ago, but the current Raptor lineup is all electronic CPPM mixing, I think.

Stabilization can be done many ways - one is with an electronic stabilizer such as the BeastX flybarless controller, or the KK 2.0 multi-rotor controller (which can run a single rotor also). The other methods of stabilization involve making the helicopter naturally stable - multiple blades and flybars contribute to that. Multiple blades raise the mass of the rotor disc, making it harder to move, and that adds stability. Flybars are a passive mechanical stabilization system, and generally can not be added to anything but a two-blade head.

You can fly a 5-blade head without any electronic stabilizer, but it's difficult, and if your skills aren't up to par, you're better off adding the stabilizer whatever it costs because it will probably save you money overall and greatly reduce your frustration.
Feb 01, 2013, 12:26 PM
Cranky old fart
Balr14's Avatar
Before you attempt to fly without electronic assistance, find an ESky HBCT and try flying that. It's a 3 blade head with flapping hinges, so it has a lot softer response than the usual rigid head. They are dirt cheap don't use any special parts that are hard to find.

It has not been mentioned, but balancing and tracking multi-blade heads is a real bitch and the more blades you have the worse it gets.
Feb 01, 2013, 01:29 PM
Registered User
I'll look at the HBCT.

but for the project I'm hearing:
1) 5 blades
2) electronic mixing (i was assuming so, I think my concept .30 had a mechanical mixer a long time ago.)
3) weighted blades.
4) maybe on a 500 instead of a 450

edit: if the HBCT didn't have a brushed motor, I'd consider buying one.
Last edited by resago; Feb 01, 2013 at 01:39 PM.
Feb 01, 2013, 08:06 PM
My other addiction!
norcalheli's Avatar
You can learn to fly a 3, 4, 5, even 6 blade helicopter without a fbl unit. The head does need to have adjustable phasing, but the process of mechanical phasing is surprisingly simple. You loosen the grub screw or bolt on the swash follower (depending on what head you buy), then pick one master blade. Rotate the blades until the master blade is perpendicular to the tail boom. Twist the swash until the ball link for the master blade lines up with the tail boom and is 90* ahead of the blade. Tighten the follower bolt (grub or whatever) and test. Give stick input for left and right cyclic. If the phasing is correct, then the master blade should not change pitch. Then give fore and aft cyclic input. The blade should change pitch. If there is some movement where there shouldn't be, simply loosen the follower and make minute adjustments until the test results are satisfactory. When you are ready to fly, dial in about twice as much expo as you normally would, and set dual rates to about 60% until you get the feel of it. I have a clone 450 with a RC Aerodyne three blade head that I'm using for a Ecureil AS-350 build. It is touchy, but pretty stable with weighted blades. RC Aerodyne ( has a decent selection of scale blades for the 450's. You can order them in sets of two, three, four and five. (I don't know if they have six blade sets or not.) They have a nice scale look, can be ordered weighted or non-weighted, and the sets are reasonably matched so you shouldn't have balance issues. Weighted work best for rigid heads, unweighted for flapping heads. For more information on all things scale you can join us over on the scale forum under fuel helis (though most over there are flying electrics nowadays). The page is Lots of good ideas and some unbelievably great scale modelers showing their talents.
Feb 01, 2013, 08:25 PM
Cranky old fart
Balr14's Avatar
Originally Posted by resago

edit: if the HBCT didn't have a brushed motor, I'd consider buying one.
For what they cost now, I don't think you could expect a brushless motor. They are selling for under $100. Besides, ESky brushed motors last pretty long. You can get 100 hours from a main and 50 hours from the tail motor, lots longer if you are flying and not hovering.

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