Giving something different a try - gear train for mini helicopter

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David K
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Joined: Sat Jan 14, 2012 8:42 pm

Giving something different a try - gear train for mini helicopter

Post by David K »

I have a fun project (to me anyway), that presents a bunch of challenges

I have some small Align Helicopters (450 size), and an older but new&unbuilt kit for a scale EC135 helicopter body, with a Fenestron tail kit

The challenge has multiple parts. 
1) Drive gear box?
The original kit was meant for a belt drive, and I wanted to build one with a full gear train/torque tube (shaft drive tail) setup.
I may build one with a belt first, and then go on to a shaft drive model after

2) Tail Authority
These are full on stunt 3D helicopters, capable of flight parameters real helicopters will never match (it's insane what some great pilots are capable of, tbh)
these remote control birds are designed to spin the main rotor at high 2k/low 3k speeds, and the tail is geared to match that, and provide tail control with fast response.  in order to run a scale model, with more than the 2 blade setups the stunt helo's use, the rotation needs to be slowed down significantly, as well as it not being needed if the blade pitch is setup for a slower speed.

This challenge is the big one - I need to speed up the rotation of the tail at these lower head rotor speeds, and thus make some changes to the drivetrain.  A lot of folks gave up on the smaller helicopters running a real fenestron rotor for this reason.

I've modeled the gear train (the tooth counts are not yet verified, but it's got what is involved so far).  It's been more than a couple years since I played with Gearotic, but I am reminded how great this tool is, by virtue of being able to spend a few hours, watch a video of Art's and make the model!

I have a bunch of questions and ideas, and wanted to build a thread, see if I can't interest some of the experts here, get some advice etc...

Attachments
450classScaleEC135Fenestrontail.PNG
450Proflying.PNG
David K
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Posts: 14
Joined: Sat Jan 14, 2012 8:42 pm

Re: Giving something different a try - gear train for mini helicopter

Post by David K »

Here are some pictures of the mechanics I am thinking about using (the drive shaft version), and a scale fenestron rotor assembly similar to mine.
Attachments
ScaleFenestronexample2.PNG
ScaleFenestronexample.PNG
450Promechanicstailrotor.PNG
450Promechanics.PNG
David K
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Posts: 14
Joined: Sat Jan 14, 2012 8:42 pm

Re: Giving something different a try - gear train for mini helicopter

Post by David K »

BTW, if I am posting this in the wrong forum, just move it and let me know where it lands.

Here is the gearotic model I built
Attachments
drivetrainmodel.PNG
David K
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Posts: 14
Joined: Sat Jan 14, 2012 8:42 pm

Re: Giving something different a try - gear train for mini helicopter

Post by David K »

There a bunch of issues for what/how this all might be accomplished, but my first step is going to examine the existing drivetrain/rotor setups, and see if I can't use some tools to determine what thrust forces are being developed.  Probably spend some time modeling the tail rotor with a tool like OpenFOAM, to see what is being developed.  And then try to model the Fenestron I have, and see if I can get any decent analysis done.

This model wont need the kind of thrust the stunt birds make, but it needs more, as it won't fly well, and certainly not in ANY kind of wind, thus this effort.

I'll update the gearotic model when I have examined the geartrain.

is there a good place to ask basic use questions for gearotic, or can I do that here?
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ArtF
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Re: Giving something different a try - gear train for mini helicopter

Post by ArtF »

David:

  Ask anything here you wish. Im deep in new code so I apologize for not being here daily as is usual.

  Your question is pretty spot on for time. Im close to releasing new bevel code which will make it easier to get
gears more like the originals you show, or perhaps better in design for that job. Though personally I like those
high conical ones. Ticker will be more geared to 3d models, rather than machining process on gears. Ive never been
completely happy with Gearotics limitations on bevels and collars and such, this has been addressed for
future release.  I estimate within a few weeks the gear production release of Ticker will be out which may
help with exactly this type of project.

Art

David K
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Posts: 14
Joined: Sat Jan 14, 2012 8:42 pm

Re: Giving something different a try - gear train for mini helicopter

Post by David K »

very cool Art I'll be sure to keep an eye out for it
I have another post here in this forum, where I am trying to back-engineer a worm gear set, to help learn me some gear schtuff... They were shipped to me yesterday, so maybe I'll have them by the weekend...

appreciate everything you do
D
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