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Jan 13, 2004, 02:05 PM
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diy Pixelito

Do any small motors have a four segment comutator that could be canabalised for this project?

Or is it possible to make a suitable comutator?
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Jan 13, 2004, 03:38 PM
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Tab magnet

As in patent application WO 03/080433A1 by Alexander Van De Rostyne, the commutator will be used to transfer power to a single Tab mag (see Graham Stabbler's inside story articles) sat in an upper yoke in the rotor head. This will either turn the main rotor blades or tillt the whole flybar yoke. Mini springs to the trailing edge of the rotors will help stabilise the arrangement.
Jan 13, 2004, 06:21 PM
Nickel what?
Phreakish's Avatar
where do you find this patent info?
Jan 13, 2004, 06:55 PM
Me likes Depron...
Pjotrrr's Avatar
Yup, should be no prob to publish here for private use....Or not???

Jan 13, 2004, 08:21 PM
Registered Lifeform
Paul Willenborg's Avatar
There was a link to the patent in one of the earlier Pixelito threads. Use the very handy "search" button in the upper right hand corner of your screen, and you should have no trouble finding it. The document is long and very detailed, you may want to skip to the illustrations first to see how it works. It is truly remarkable!

I think it would be very impolite to publish any details from the patent here, at least until a firm announcement is made on commercial applications. If you read Alexander's site, he says clearly that the technology is being licensed for commercial use. We should err on the side of caution, since he was nice enough to share the Pixelito with us.

Jan 14, 2004, 03:18 AM
Registered User

Patent link

Here is the link to the pixelito patent :-

The hinge for the tab magnet could be mounted outside of the coil as in some of Graham Stabler's 'inside story' illustrations or the magnet could be pivoted by bringing the shaft out in between two adjacent coils, as in some of the other designs. If the coil radius is R and the coils are separated by a distance R then the field at the midpoint, and some way along the axis, is uniform. Within a single coil it's probably more or less uniform to a first approximation. Perhaps someone might comment on how the single/double coils affect the proportionality of the coil response?
Jan 14, 2004, 12:12 PM
Registered User

Pixelito patent

The pixelito patent is public domain. All patent applicants must agree to their patent being published. Full protection against unathorised commercial exploitation is provided by the patent application (and continues for a considerable period providing it is subsequently granted by the patent examiners).

The following is nearly the same in every country.:-

The specification shall contain a written description
of the invention, and of the manner and process of
making and using it, in such full, clear, concise, and
exact terms as to enable any person skilled in the art
to which it pertains, or with which it is most nearly
connected, to make and use the same, and shall set
forth the best mode contemplated by the inventor of
carrying out his invention.

On the danger of invalidating the patent by Mr Van de Rostyne using a secret Tab mag in the pixelito model, instead of a motors as illustrated in the document see

"Since patents have been invalidated for failure of the applicant to adequately present or describe the invention, it is important that we be sure to include in the application a sufficient description to permit one skilled in the field to which the invention pertains to make and use not only some form of the invention, but the best form of the invention known to us at the time the application is filed. For example, if we know that the preferred form of the invention requires use of a particular material, or processing of a particular sort, we must fully disclose this in the application. Put differently, if we decide that some aspect of the invention is really proprietary and a trade secret and therefore do not disclose this aspect in the application even though it relates to the preferred embodiment of the invention, not only will any resulting patent likely be invalid, we also may be held liable for significant damages occasioned by others who have been sued for infringement of the patent, or who have improperly paid royalties thinking the patent to be valid, or who have had to change what they were doing, or were investing monies to design around what they thought to be a valid patent. "
Jan 14, 2004, 03:22 PM
Registered User

commutator ideas but problems

It has been sugested that any commutor of suitable OD could be employed. Drill out the centre to the required ID, remove those copper segments not required, fill these 'dead' gaps with a low friction non conducting substance e.g. resin. should be straight forward. polish by inserting in a drill using lapping compound or similar. However any gaps in the live segment of the comutator need to be filled with a conductor, any suggestions?


Jan 14, 2004, 04:58 PM
Registered User

Fatigue problems in pixelito design

Any extension of this idea to full size helicopters as suggested in the patent would require much analysis of the rotors loading's which is of a cyclic nature. It may also impact on the longevity of scale models. The blade's oscillation pattern reminds me of the Wohler cyclic fatigue test.

Further to Peter Bennett's post a test of the patent's validity is that it can be reproduced from the patent details by those skilled in the art, e.g. experienced members of this forum.
Jan 14, 2004, 07:05 PM
Registered User
Anybody know if the concept of using a commutator and muscle wire based actuator embedded in the rotor head for helicopter control has been patented?

Cause if not (and if it hasn't already come up), will just discussing it here make for prior art?

Jan 14, 2004, 07:58 PM
Registered User
Keennon's Avatar
Darkith- I don't think muscle wire will work too well. The 0.001 in. (25 micron) diameter wire drops to half it's activation length at around 7 Hz or 420 RPM, so I don't think it could actively drive a rotor as it spins. At micro heli rotor speeds probably could only get less than a percent of contraction. Maybe it could pushed very hard and get to work, but the power consumption would be much higher than a mag-coil applying same force and travel.

I think Piezo or electro-magnetic are the two most promising ways.

Muscle wire could drive a swashplate with no problem, since speed only needs to be as fast as the pilot's movements of the sticks.

Jan 14, 2004, 08:27 PM
Registered User
Thanks Matt.

Jan 14, 2004, 09:04 PM
Permanently banned
Mario's Avatar
Commutators come in vaious number of poles, just have to find them. The transfer of power "round the pole" style as well as use of actuators for control of models is nothing novel.
Jan 15, 2004, 03:15 AM
Registered User

Suitable commutator


Forget about taking out the unused segments. Once you have found one of a suitable size OD/ID, wire in series suficient of the arc to give the required length of contact and just don't connect the other segments. If graphite bridging or similar becomes a problem then you might have to do some judicious filing and possibly fill the gap with expoxy and smooth down really well to avoid excessive brush wear.

Jan 15, 2004, 04:27 AM
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