Author Topic: Variable Pitch Hub (Read 25227 times)

Goose · « **on:** September 25, 2006, 02:31:44 PM »

Here is something I made about 4 years ago, and has been in storage ever since. I have a new design now. This one will get scrapped.

big pic 1

big pic 2

And here is one of the reasons my projects are in storage for awhile. This is the fun part of my responsibility.

big pic 3

big pic 4

big pic 5

i had to remove your pics as they are over 100k so i made them links please resize in the future
Kurt

The Crazy Noob · « **Reply #1 on:** September 25, 2006, 09:15:15 AM »

Can you give more details about the hub?

Bruce S · « **Reply #2 on:** September 25, 2006, 10:57:35 AM »

I've got gray and biscuits on , let's eat:--)

Bruce S

makenzie71 · « **Reply #3 on:** September 25, 2006, 10:58:47 AM »

What were you going to use as blades? How were you going to operate the pitch mechanism?

The Professor · « **Reply #4 on:** September 25, 2006, 11:17:07 AM »

Looks much like Marshall Price's plan in Mother Earth News. Currently $25. I bought this plan set about a month ago. Looks to be a pretty good plan for a 12ft diameter mill with a variable pitch hub. He had his running for several years before the article was written. I think this was in 1984.

Just painted the tips red last night. 9ft dia. 2 x 6 lumber

twombo · « **Reply #5 on:** September 25, 2006, 11:56:43 AM »

Looks like that young fella has a good shooting form. Nice work "Pop"!! Looks like you are making good investment choices!

Mike

Goose · « **Reply #6 on:** September 25, 2006, 02:27:32 PM »

Yep,

From Mother Earth news, drawn up by Marshall Price. I modified, instead of using ball bearings, I used Timken taper roller bearings.

Nice blades! That will be a new thing for me, carving out the blades. Hopefully they will look as good as yours.

Goose · « **Reply #7 on:** September 25, 2006, 02:28:37 PM »

Sorry Kurt,

I had them resized to 100k, but they didn't look very good. Thanks for making a link for me.

Goose · « **Reply #8 on:** September 25, 2006, 02:32:02 PM »

It will work with lead weights swinging as it turns faster. Where the pencil is in the picture, there will be a spring compressing as the hub turns faster. Don't know about blades yet. I was planing on making fiberglass foam core, but I might try to carve a set out.

Goose · « **Reply #9 on:** September 25, 2006, 02:36:34 PM »

Ya, he's doing pretty good for a 6 year old. He shot those with my .17 rim fire. He begs me everyday to get a gun bigger then the daisy. Maybe a pellet gun for his B-day.

jmk · « **Reply #10 on:** September 25, 2006, 07:33:32 PM »

I like your blades too. Are those airplain parts up on the shelf in the background. Looks like a spar to a horizontal stab?

twombo · « **Reply #11 on:** September 25, 2006, 10:03:48 PM »

Yeah, that little .17 will busta bunny. I'm wanting one myself. I have a couple jazzed up 10-22s, but, would like a little more snap for the big old jacks around here.

You can see the confidence in his eyes... very cool little partner!

Keep up the good work!

Nice variable pitch work too. Betcha that little tiger will be making hot blue chips soon too!

Regards

Mike

txcowdog · « **Reply #12 on:** September 25, 2006, 11:36:18 PM »

That is a great looking hub and a considerable amount of work. How much fabricaton time do you have invested in that hub?

The Professor · « **Reply #13 on:** September 26, 2006, 10:07:02 AM »

Ultralight airplane parts in the back ground,for a geodesic wood and fabric Ritz Standard. 36ft. span. An unfinished project, I console myself by thinking that I have lived this much longer to raise 2 kids and build many other projects.

Link to 4 pics of the pieces.

http://ph.groups.yahoo.com/group/vula/photos/browse/3de4

Goose · « **Reply #14 on:** September 26, 2006, 10:46:53 AM »

up to that point, only a few hours. The prints Mother Earth sells are pretty good.

The new one I want to build will take longer, cause It is my own design. I will try to get a picture on the board when I get home from work.

Goose · « **Reply #15 on:** September 26, 2006, 10:49:25 AM »

Ya, that little .17 can hit a dime no problem anywhere inside a 150 yards.

wlcoldiron · « **Reply #16 on:** September 26, 2006, 06:44:27 PM »

Jacobs used tapered bearings in his flyball governer design. The bearings do not rotate fully causing the rollers to only wear in a small area. this causes the outer race to have high and low wear areas. Mike hackleman's book shows some close ups of what happens. large surface area bushings will be better than the tapered roller bearings for this application. wlc

Goose · « **Reply #17 on:** September 26, 2006, 08:40:12 PM »

OK,

Maybe somebody can tell me if this will or will not work. I don't have the governer figured out completely yet, but there will be 3 racks 120degrees apart in the center sliding in and out with fly weights. To get the right preload on the gears, I was thinking of making the outside of the bearing blocks offset with the bearings(like a cam). When you rotate the bearing block it will move the gear closer to the rack. I've had this drawn up with Acad for awhile now, and I am just learning with SolidWorks, so I haven't finished it yet.

redsand · « **Reply #18 on:** November 07, 2006, 10:27:11 AM »

This seems to be a great hub. The blades are of what material? Carve them from what? Any other problems that might be expected? your design looks solid enough. Though don't take it from me. I am a novice without much experience.

smidy · « **Reply #19 on:** December 25, 2006, 11:28:29 PM »

hi

I have a prop from a small aeroplane, probably a Cessna, with variable pitch blades. if there is any intrest I can take a picture of the hub. I think those hubs should be well worth thinking of for variable pitch windmills

hvirtane · « **Reply #20 on:** December 26, 2006, 03:59:38 AM »

That aeroplane prop would be interesting to see.

if you can, please take pictures and post here.

Some time ago I made draft drawings for a pitch

control system:

- Hannu

smidy · « **Reply #21 on:** December 26, 2006, 07:58:04 AM »

okay lets se if I can post pictures

and

and last

if you want I can take some messurements tomorow

hvirtane · « **Reply #22 on:** December 27, 2006, 03:31:35 AM »

Hi,

the pictures are nice. Thank you a lot.

But could you put here more pictures

about the inside of the hub?

- Hannu

smidy · « **Reply #23 on:** December 27, 2006, 12:29:14 PM »

for hannu

Yes I think I can take some more pictures tomorow, eventual remove the blade that is in up position in the pictures. It´s not so much to se really, it´s a pretty simple construction: where the blade enters the hub it´s changing shape from airfoil to round and have two ballberings, pretty big about 10-15 cm diameter. Where the "blade" ends inside the hub it´s a tapered hole with a pin in ,so you are able to turn the blade when moving the pin back or forward for "+ or -" pith angle

xymox · « **Reply #24 on:** November 17, 2011, 01:29:13 AM »

I had this idea for a variable pitch hub floating around in my head, tricky part is sizing the spring. I calculate a 20 Lb blade 8 feet long at 400rpm would equal about 8725.52 Lbs of pull via this calc tool

http://www.calctool.org/CALC/phys/newtonian/centrifugal

Was thinking I could use a die spring like these at

http://www.danly.com/cgi-bin/proddisp.pl?prod=18123

anyway it seems a pretty simple idea and I have not seen it built as simple but wanted to get some feedback from the experts. Basically its just a pin that guides the pitch based on its position down the collar.

RP · « **Reply #25 on:** November 17, 2011, 10:13:34 AM »

Without tying the 2 blades together, you can assume that one blade will move before the other one and you'll immediately have a severe out of balance condition on your spinning rotor. That particular vibration will amplify the out of balance condition and tend to pull that 1st blade out even further.

That's why in these kind of designs you always see some levers or gears or some such keeping all the blades synchronized.

Bruce S · « **Reply #26 on:** November 17, 2011, 10:42:29 AM »

Here's an article I found in a NASA magazine that I get.
http://contest.techbriefs.com/component/content/article/1389

Deals with just this as well.
Thought it would make for some good reading too.
Cheers;
Bruce S

xymox · « **Reply #27 on:** November 17, 2011, 11:20:55 AM »

That is interesting, I guess I had figured that with equal mass on each side of the hub and equal size springs, it would all stay in sync, but you are right, in reality, one always moves before the other. the distance traveled outward would be about .68 inch.

Based on spring streangth, it moves 1/10 of an inch for every 419 Lbs of outward thrust. So I guess my opinion is that yes one will move first. But with springs this strong. It would only be out of balance by a very small fraction of an inch (dare I say thousanths of an inch)

I did my calc on a 16 Lb blade (which is probably way to heavy) and calculated the outward thrust in Lbs every 1 foot then added them all together.

midwoud1 · « **Reply #28 on:** November 17, 2011, 03:57:11 PM »

Hi Xymox.
Yes synchronize the blades is a must. Try to find something with a levers and quick-links . Otherwise you get problems with earlier mentioned unbalance and flutter.
Rgds F.

xymox · « **Reply #29 on:** November 17, 2011, 04:18:01 PM »

when people say flutter, I assume they are talking about the rotational movement along the blade length axis in a quick and repetitive motion? is this something that some form of a damper would solve?

midwoud1 · « **Reply #30 on:** November 17, 2011, 05:47:03 PM »

Flutter is an uncontrolled vibration in the blades running medium and high speed.
I made a 2 blade hub with parallel shafts connected with gearwheels . Make it light moving and without play .Find relation between flyweights and spring tension. My prop opens at about 90 Rpm.
to working angle.

xymox · « **Reply #31 on:** November 17, 2011, 11:31:31 PM »

ok, so I came up with a cam lobe setup so that positions are equaled out. This should solve that problem, center shaft of course would come through the middle of it and be secured with a few thousands clearance so that its free to move. now how to deal with flutter......

Dave B · « **Reply #32 on:** November 18, 2011, 01:53:06 AM »

I think the cam ends would need to be linked to the blade shaft ends to be syncronized unless I am missing something. This appears that one blade could still pitch on it's own without helping or forcing the other to pitch the same as well. Hyme joints are common in variable pitch hub configurations, lots of options there. Dave B.

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Author Topic: Variable Pitch Hub (Read 25227 times)