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Quetico Bob
06-20-2009, 04:14 PM
How is it done? Just boggles my mind, 20,000 or so to 400rpm. That is some serious machining.

Our fire season is really just starting and we provide some space for the forward attack crews here. This baby just came in this morning, nice looking unit. Talk to the pilot, it’s an A-Star 350D. Actually thought by the sound it was a Bell 212 which frequents us, just a wee bit lighter on the thump.

But then again I think the thump depends on the pilot, sometimes, its rattle the windows in a big way and hang on to anything you don’t want shaken, other times its just noisey and I have to go to work dear, their here. And with the pads less than 80 yards from the house, you know it.

Although yesterday another new job came in, similar to this but way more aerodynamic looking and 4 blades with a fan. Nothing I have ever seen or heard before, more of a whine to it, must be new, sure looked like it. Next time it comes in I will get a pic and talk to the driver.

Anyway, thought some of you would like the pics, have always wanted to fly one of these, childhood dream. There’s a good chance they may be heading out on patrol and will try to get another of it lifting off this afternoon.

Cheers, Bob

http://i303.photobucket.com/albums/nn142/Queticobob/June202.jpg

http://i303.photobucket.com/albums/nn142/Queticobob/June201.jpg

http://i303.photobucket.com/albums/nn142/Queticobob/June20.jpg

Evan
06-20-2009, 05:26 PM
20K to 400 is only a 50 to one reduction. That's pretty easy to do. A double compound planetary gear set will do it nicely.

See these videos of one I made using SketchUp. (Not my model)

~1 MB

Proper operation http://ixian.ca/video/plgear.wmv

What happens if you forget something :D

http://ixian.ca/video/plgearnp.wmv

Quetico Bob
06-20-2009, 05:40 PM
QUOTE” What happens if you forget something” QUOTE

Priceless, first time I went up with a friend in his Taylor Craft he asked me, Do you know what the purpose of the propeller is? Obvious answer but, I have never thought I knew the obvious….Why I asked?

It keeps the pilot cool, cause when it stops you should see the sweat!

First and last time I flew a plane was with him, rest his sole.

Cheers, Bob

GKman
06-20-2009, 06:00 PM
20K to 400 is only a 50 to one reduction. That's pretty easy to do. A double compound planetary gear set will do it nicely.

See these videos of one I made using SketchUp. (Not my model)

~1 MB

Proper operation http://ixian.ca/video/plgear.wmv

What happens if you forget something :D

http://ixian.ca/video/plgearnp.wmv

I must be a little dense today. What color does what? Input? Output?

Evan
06-20-2009, 06:39 PM
The inner gear the centre carrier and the outer housing are all part of the action. What happens depends on what is allowed to rotate and what isn't.

Trying to explain it is very difficult. Play with it for a few minutes in SketchUp and it becomes clear, which is the point of the model. It is a Sketchy Physics model.

Bob, the helicopter you saw with the tail fan is probably the Aerospatiale Gazelle.

http://ixian.ca/pics6/gazelle.jpg

Quetico Bob
06-20-2009, 07:03 PM
QUOTE”the helicopter you saw with the tail fan is probably the Aerospatiale Gazelle”QUOTE

Hard to tell, this one had 4 blades and don’t remember the rib over the tail section. But I only drove by it about a dozen times in passing looking at it from the front. Never stopped to really take a close look as they were supposed to be stationed for several more days. Thought I had some time.

Tell you one thing, I have never seen such a tight turn at speed and altitude coming to the pad, an amazing machine. Betcha this thing would put John Travolta and his disco moves outta business.

It will be back as it’s a regulars owned aircraft.

Cheers, Bob

Evan
06-20-2009, 10:25 PM
Tell you one thing, I have never seen such a tight turn at speed and altitude coming to the pad, an amazing machine. Betcha this thing would put John Travolta and his disco moves outta business.


I don't know about the blades, maybe a newer version? The Gazelle is one of the fastest helicopters and is also fully aerobatic, very unusual for a helicopter.

http://ixian.ca/pics6/gazelle2.jpg

http://www.furyhelicopters.com/content/Movies_StoryShip.htm

Dr. Rob
06-20-2009, 10:31 PM
...or the Aerospatiale HH-65? They have a distinct constant whine with a lesser thump on approach and more of a smack-thump passing by. (i live under the flight path to a hospital landing pad a few hundred yards away)

http://farm4.static.flickr.com/3366/3345096669_d33c2fc4a9.jpg?v=0

clint
06-20-2009, 11:21 PM
Evan

On the planetary gears we have them on machines at work, I have worked with the company 15 years now, and have had my hand at going at every part on the machines, and the planetary gear gave me some trouble at first. Lucky for me we have a neat way of looking at a machine right beside the one broke down for how it should be, I also got a spare planetary to examine how it works, it's hard to comprehend in that video, however once you understand they are very simple, and superb in reliability. We replaced some steel gears inside with nylatron, then implemented across the entire job, it worked great if anything locked down the nylatron gear would strip instead of raking havoc with the entire gears, bearings, and most of the time the outside ring gear.

Our setup is one that is driven by a shaft on the inside center, this in turn transfers energy/movement to another set of gears, and yet to one more set that drives on the outside face with two "implements" ( have to be some what discrete company is real high on "treason") this allows the two implements to be timed via a 360* rotation.

Long rambling post, I just wanted to say it's really hard to comprehend a planetary without having it in your hands to work with, and then it takes a few minutes to see just exactly how it works, reduction can be whatever you dream of on a planetary.

dp
06-21-2009, 12:17 AM
Here's a fun animation of the Prius planetary drive. The Prius has two motors and this is how they are coupled to the final drive. This is a case where the planetary gear has two drivers.

http://homepage.mac.com/inachan/prius/planet_e.html

aostling
06-21-2009, 12:44 AM
Here's a fun animation of the Prius planetary drive.

This one is even more fun: http://eahart.com/prius/psd/ -- it has sliders which work. The drive is a fascinating electro-mechanical hybrid itself.


''It acts as a continuously variable transmission (CVT) but with a fixed gear ratio.''

dp
06-21-2009, 12:51 AM
This one is even more fun: http://eahart.com/prius/psd/ -- it has sliders which work. The drive is a fascinating electro-mechanical hybrid itself.


It acts as a continuously variable transmission (CVT) but with a fixed gear ratio.

This one does a good job of showing the relationship between the electric drive and the engine/generator combination.

Did the sliders not work for you on the other link? The were fine here. it's a pretty boring demo if they don't work :)

Evan
06-21-2009, 01:09 AM
Just download SketchUp and the Sketchy Physics plugin and there are hundreds of mechanical models to play with. With the SP plugin the main distinguishing feature of the $500 pro version vanishes. Right now I am just finishing debugging some code I wrote to produce fancy fully triangulated meshes for CamBam that will export DXFs that are compatible with ShetchUp.

I will post more later in a new thread.

aostling
06-21-2009, 01:09 AM
Did the sliders not work for you on the other link?

No, the sliders were stuck for me -- needing a Flash 6 player which I must not have loaded my mac.

Evan
06-21-2009, 01:15 AM
OK, I just saw proof that something is screwy with this BBS software. This has been happening for a while to me and a couple of other people have made comments about not seeing a post at all until later.

The post by Alan, #14 was already on line and I had already read it. It took me several minutes to post my post which should be after his but instead was inserted ahead of his as #13.

This explains some posts that appear to be non sequiters and really poses a problem in a some discussions. My post followed Alan's by at least 3 minutes.

dp
06-21-2009, 01:25 AM
I wonder if you're given a sequence token when you open a reply rather than when you post it.


Just checked and found this:



<div style="margin-top:6px">
<input type="hidden" name="s" value="" />

<input type="hidden" name="do" value="postreply" />
<input type="hidden" name="t" value="35298" />
<input type="hidden" name="p" value="449979" />
<input type="hidden" name="posthash" value="" />
<input type="hidden" name="poststarttime" value="" />
<input type="hidden" name="loggedinuser" value="4041" />
<input type="submit" class="button" name="sbutton" id="vB_Editor_001_save" value="Submit Reply" accesskey="s" tabindex="1" />
<input type="submit" class="button" name="preview" value="Preview Post" accesskey="p" tabindex="1" />
</div>


The hidden fields that are sent back with the reply suggest sequencing. 35298 /3600 == 9 hours and some change if it's a time field.

Evan
06-21-2009, 01:34 AM
That isn't it. I had Allan's post on screen while I was replying.

dp
06-21-2009, 01:40 AM
That isn't it. I had Alan's post on screen while I was replying.

I can't tell from the sequence if you were replying to Alan or someone else. If replying to Alan's last post then yup - makes not a lick of sense.

aostling
06-21-2009, 01:44 AM
With the SP plugin the main distinguishing feature of the $500 pro version vanishes.

I'm eager to see this post. SketchUp Pro has animations and dynamic components which I would find very useful, though I balk at paying the $500.

dp
06-21-2009, 01:47 AM
I'm eager to see this post. SketchUp Pro has animations and dynamic components which I would find very useful, though I balk at paying the $500.

Windows only - I'm on a Mac, too.

Update: I read the Wiki and found a Mac port I'll try out. It can be found at http://sketchyphysics2.googlecode.com/files/SketchyPhysics3a-Feb9-Mac.zip

oldtiffie
06-21-2009, 02:03 AM
Try these demonstrations of the principles of the various types and variations of sun and planet systems:

http://kmoddl.library.cornell.edu/search.php?search=+sun+and+planet+gear&collection_1=1&collection_2=1&collection_3=1&collection_4=1&collection_5=1&collection_6=1&collection_7=1&collection_8=1&in=0&type=m&audience=

http://kmoddl.library.cornell.edu/search.php?searchSelect=search+KMODDL&field3=fulltext&authority=kmoddl&collection_1=1&collection_2=1&collection_3=1&collection_4=1&collection_5=1&collection_6=1&collection_7=1&collection_8=1&search=sun+and+planet+gear&image.x=11&image.y=11

b2u44
06-21-2009, 02:49 AM
To reply to the OP's question:

Take a look at this photo:

https://engineering.purdue.edu/AAE/Research/Propulsion/Info/rockets/jets/tjets/images/jets/tprops/pw200.gif

In a turbo-shaft engine, the compressor and "compressor turbine" spin on one shaft at a very high RPM. The exhaust from the "compressor turbine" spins a "power turbine" that rotates much more slowly on a second shaft which transfers power through fairly standard gearing to the rotors on the helicopter.

Note: The low-speed shaft typically runs concentrically through the hollow high-speed shaft.

GKman
06-21-2009, 09:01 AM
The inner gear the centre carrier and the outer housing are all part of the action. What happens depends on what is allowed to rotate and what isn't.

Trying to explain it is very difficult. Play with it for a few minutes in SketchUp and it becomes clear, which is the point of the model. It is a Sketchy Physics model.

So you made a pretty gee-gaw that doesn't explain or demonstrate the question of a hugh gear reduction, and you don't know how it works either. Could you show it with part or parts fixed as in real life so it produces the desired result?

Evan
06-21-2009, 09:48 AM
I didn't make the model as I said in my original post. Perhaps you would like to explain in words how a differential works? It is something that is fairly easy to understand when you see it work but very difficult to explain in words. Fly at it if you think you can.

I do know how it works. Do you? If you don't then download SketchUp and the Sketchy Physics plug-in and learn for yourself. I have put up a new post with all the links you need.

oldtiffie
06-21-2009, 09:49 AM
Good question GKman.

I thought I'd better get my finger out and look a bit harder.

Press the buttons here:
http://www.mekanizmalar.com/transmission.shtml

The theory re ratios and directions of rotation are here:
http://en.wikipedia.org/wiki/Planetary_gearing

Quetico Bob
06-21-2009, 02:26 PM
Thanks folks for the cool stuff on planet gears and pics. Dr. Rob, that s not it, our hospital uses one that looks like that, one nice looking machine none the less. The one Evan posted is more along the lines. As soon as it shows up again I will post a pic. Missed the one stationed right now for lift off photo, left in a hurry shortly after 6 this morning.

B2u44, thanks for the tip “turbo-shaft engine”

http://www.youtube.com/watch?v=V2vpXCcICdg

Cheers, Bob

Quetico Bob
06-21-2009, 04:36 PM
This one just came in, it’s a B2 replaced this mornings 350D. More payload.

http://i303.photobucket.com/albums/nn142/Queticobob/DSC_0002.jpg

Found out the model of the one originally discussed by talking to the pilot, it’s a B4. Was just taken in for its 100hr service. The one here was painted bumble bee yellow which looked pretty cool.

http://en.wikipedia.org/wiki/Eurocopter_EC_130

Cheers, Bob

GKman
06-21-2009, 09:19 PM
I didn't make the model as I said in my original post.


these videos of one I made using SketchUp. (Not my model

I'm not only so dense that I can't figure out the planetary reduction, I can't even figure out whether you made the model or not. You better give up on me.

dp
06-21-2009, 09:58 PM
I'm not only so dense that I can't figure out the planetary reduction, I can't even figure out whether you made the model or not. You better give up on me.

He transcribed the pre-existing model to a video. Viewing the model directly requires installing software.

Evan
06-21-2009, 10:27 PM
Sketchy physics allows you to make animations (videos) of whatever happens on the SketchUp workspace. That was previously only available in the Pro version and combined with the interactivity of Sketchy Physics is the main difference between it and the free version. The other difference is the ability to export in many different formats. However, the is an Export to OBJ format plugin that pretty well eliminates that issue too. It is possible to make SketchUp Free equal to SketchUp Pro.