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Old Jan 03, 2007, 07:56 AM
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Stockholm, Sweden
Joined Jan 2004
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BBA / Muscle Wire Actuator - State of the art

Hello,

While fixing up my BBA equipped Tiny Moth for the indoor flying season I realised it has been rather quiet around BBA:s and other muscle wire actuators lately.

So, what is the current state of the art of BBA:s?
Are there any new designs to reduce the risk of muscle wire fatigue?
What can be done to reduce power consumption?
What is your favourite combination of wire length, voltage regulator and power transistors?
Are there any new designs that can compete with the BBA with respect to centering accuracy, control force to weight ratio or low power consumption?

Please contribute your experience and latest development of muscle wire actuators for micro RC models.


Best regards,


Jonas
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Old Jan 26, 2007, 03:15 PM
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Stockholm, Sweden
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Bump...

Is anybody still using muscle wires?


Best regards,


Jonas
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Old Jan 26, 2007, 04:52 PM
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MGeo's Avatar
New York
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Muscle (shape memory) wire seems to be less popular due to availability and increased complexity in application.

What is BBA?
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Old Jan 26, 2007, 05:37 PM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
BBA stands for Bob Bailey actuator. See index thread for links.

He wire springs to maintain tension and wire attachment points to the rear of the pivot to provide excellent centering.

No developments on this front to my knowledge.

Graham
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Old Jan 27, 2007, 01:18 PM
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California
Joined Oct 2002
410 Posts
Hey wait a minute! I'm using muscle wire dual actuators exclusively on my micro models. I designed a variant of the BBA actuator that work quite well and has many advantages over mag coils. Quieter, essentially silent, lighter weight for same force, better power to weight ratio, very similar electrical power to mechanical power efficiency to mag coils. They can be installed easily in the fuselages and drive pushrods like normal servo type installations. Downsides are difficulty to build, non-linearity, and slower response (helps the noise however). Response is plenty fast for aerobatics, but not fast enough vibrate your tail surfaces at 1Khz! Here are three of my smallest models, 3 channels each, 2.5g on the WWI ships, the other is around 5g as I recall.
-Matt
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Old Jan 27, 2007, 02:09 PM
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I don't think anyone sells BBA or other muscle wire actuators pre built do they?

That would probably be a big reason for thier non use by the general populace.

Would there be enough interest in pre built ones for shops to start stocking/making and selling them ?

(They would probably be labour intensive to make and therefor a lot more expensive than coils)
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Old Jan 27, 2007, 02:26 PM
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Wow Keennon, these are nice models. Can you give us some insight in how you made your modified BBA's and how you drive them?
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Old Jan 27, 2007, 03:14 PM
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California
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I did a series of articles on my muscle wire actuators and models for RC Microflight which folded and is no longer available. I will try to update those and publish them again in the RC Microworld online magazine: http://www.cloud9rc.com. They are by no means impossble to build, but in a world full of RTF toy airplanes and instant gratification, people are less likely to invest a weekend tinkering with new technology, regardless of good it might be. I've sold a bunch of actuators to people, the people that bothered actually putting them into a model did great with them. If RC Microworld doesn't want to publish my muscle wire articles, maybe I can publish them on Ezone.
Cheers.
-Matt
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Old Jan 27, 2007, 03:55 PM
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Stockholm, Sweden
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Hi Matt,

It is great to see you on this thread. Your models have been a valuable source of inspiration when trying the BBA.

Regarding the muscle wire actuators you use; I am assuming you use a regulated voltage to supply them, am I correct? If so, what voltage do you use and how long are the muscle wires? My Tiny Moth uses 3.0V and about 30 mm of wire on each side of the horns.

It would also be interesting to know what type of drive transistors you recommend. I have used the Fairchild FDG6303N transistor pair. One or two of these transistors have failed, so they may not be quite up to the job (or perhaps they failed due to my mistreatment?).

For readers not familliar with muscle wire actuators;

The reason for asking about the voltage and wire length is that these parameters set the maximum current draw of the actuator. Finding a suitable combination that heats the wire enough but does not draw excessive current would help minimizing the power consumption of the actuator.

Some background information...
The original BBA thread:
http://www.rcgroups.com/forums/showthread.php?t=166212
My Tiny Moth using a BBA actuator:
http://www.rcgroups.com/forums/showthread.php?t=314393


Best regards,


Jonas
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Old Jan 27, 2007, 05:16 PM
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Brisbane
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Matt,

What kind of price where you selling the actuators for when you where selling them ?

Also looking at the aeronutz article yours seem a lot easier to make than the BBA. How much heavier where your style actuators than Bobs (talking about having 2 of yours vs the one of Bobs which had the weight written down as 0.1g)
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