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Author Topic: Variable pitch propeller experience?  (Read 2207 times)
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Pops
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« on: June 30, 2015, 08:29:01 PM »

Friends,

Are there any of you that have experience with this type of variable pitch propeller?

http://i.ebayimg.com/00/s/MTIwMFgxNjAw/z/VugAAOSwv0tVTSNe/$_57.JPG

I'm planning a new design and like to check it out, but think it would be nice with some "for and against" inputs before I buy.

All oppinions are appreciated! Thanx a bunch in advance.

Brg

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« Reply #1 on: July 02, 2015, 05:51:53 AM »

Who is it made by?  More info is needed than just a photo.
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« Reply #2 on: July 04, 2015, 09:16:21 PM »

Friend,

So far I haven't been able to positively find out who the manufacturer is, but it might be Mamo. This is probably a case of "same stuff, different wrapping", since I find this propeller sold by several shops, Icare Icarus, Robotbirds and Hobbyking being three of them. Many places it's called a "Type C" propeller. You can find Chinese vendors selling blades for this prop on ebay, but not a complete propeller. (Okay, complete propellers CAN be found with other ebay vendors but none of them seems to be willing to ship to Sweden!) Smiley

Blade sizes seems to vary from 7" up to 10".

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« Reply #3 on: July 05, 2015, 11:58:02 AM »

Found it on MAMO with 8 inch blades.  Kind of expensive, tho.  I've seen a couple of the VP units at some of the indoor rc outings, but they don't seem to have really caught on even tho the antics they allow are nothing short of triple "WOW".  Probably due to the cost and difficulty getting spares.  I don't know of anyone using these for outdoor planes (yet) nor have I found them on fleabay (de).

The one you pictured looks to be all-plastic, whereas the one from MAMO and HK are carbon fiber (blades and motor mount) with a few plastic side gubbins - the hubs appear to be alike

You shouldn't have any problem ordering from MAMO (or HK for that matter with a longer shipping time but half the price and two sets of blades).

Where are you in Sweden?  I have cousins in Malmo.
« Last Edit: July 05, 2015, 12:14:38 PM by Pit » Logged

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« Reply #4 on: July 05, 2015, 02:09:38 PM »

I think that's not a useful item for free-flight. As far as I know this gimmicks are used for indoor aerobatic flying coming vertically down, stopping at 10cm from the floor, inverting pitch and coming out of the figure backwards. So the variation in pitch is remarkable going from say pitch +8'' to -8''. What you are looking for, I believe, is a much smaller pitch change, say from 10'' to 6''.
I also ask myself what type of model could profit of such a mechanic. Of course Wake's and CdH's use variable pitch props, the governing power is torque. In your gimmick you would need a servo to command the pitch variation and some crafty algorithm to govern it.
It just does not make sense to me, sorry.

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« Reply #5 on: July 05, 2015, 03:48:35 PM »

I think that's not a useful item for free-flight. As far as I know this gimmicks are used for indoor aerobatic flying coming vertically down, stopping at 10cm from the floor, inverting pitch and coming out of the figure backwards. So the variation in pitch is remarkable going from say pitch +8'' to -8''. What you are looking for, I believe, is a much smaller pitch change, say from 10'' to 6''.
I also ask myself what type of model could profit of such a mechanic. Of course Wake's and CdH's use variable pitch props, the governing power is torque. In your gimmick you would need a servo to command the pitch variation and some crafty algorithm to govern it.
It just does not make sense to me, sorry.

Urs
What leads you to think that the OP is thinking of using this in a free flight application, after all he posted in the RC forum of this site? Yes, it was a bit of gimmick often called "4D".

Now this is neat and easy to use this as the basses of a constant speed prop. With today's telemetry and the open source code of radios like the Taranis there are several way to accomplish this.

The real stumbling block is that the blades for these prop hubs are non twist. That is they are not helical pitched, very inefficient! Now again it is easy to fabricate your own blades out of epoxy and carbon.

I did something like this with the old Kyosho Hyper Fly, 25 or so years ago.

All the best,
Konrad
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« Reply #6 on: July 05, 2015, 03:54:31 PM »

OOOOOps..... should look better next time  Embarrassed Embarrassed Embarrassed

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« Reply #7 on: July 05, 2015, 07:47:55 PM »

On second thought my constant speed prop was based of a Kalt Barron tail rotor.
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« Reply #8 on: July 05, 2015, 09:38:50 PM »

Friends,

Thank you so much for this input! Yes, I'm planning a new R/C design but the more I scrutinize this contraption I find that it probably won't suit my needs. It's too small and, as Konrad points out, the blades are very inefficient (and way too flimsy for anything more than a few hundred watts). So I guess it's back to the good ol' drawing board. You know the old saying; "If you want something done, do it yourself!" Smiley

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« Reply #9 on: July 06, 2015, 12:49:26 PM »

Such is the plight of the pioneer!
Don't give up. I think with the plethora of 700 and larger size helicopters that there is a hub strong enough for your needs. And making continuous fiber blades (carbon) is not that difficult.

So may I ask what you are thinking of making?
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« Reply #10 on: July 08, 2015, 09:13:14 AM »

Haha, I was about to reply with the famous(?) phrase: "I could tell you but I have to kill you afterwards!" (Kidding indeed!) Cheesy

I'm not planning on building a "4-D" shockflyer, instead I want a propeller in a suitable size that can be feathered/reversed, and have a rather nice efficiency. The hub design should be able to be used with either 3, 4 or 5 blades, so the prop can be used with many different airframes and engines. Using turboprop engines has become a "wet dream" for me and now that technology is "starting to mature" so to speak. Some people are even building their own turbines; who says I can't do the same, starting at a lower level and work upwards from there?

My ultimate design is a multi-engined, quarter-scale behemoth, that I probably can't fly anywhere without the world's most expensive insurance, along with certificates and permissions from the police, FAA, NASA, CIA, UN, the IRS, the Kremlin and the Pope... Cheesy Before that, I intend to practice on smaller airframes, building proof of concepts. For now I would be happy with a propeller and gear unit, capable of soaking up around 1000W of power and have variable pitch capabilities. A design is already on the sketchpad, now it's time to iron out the wrinkles and create a good prototype or two. They will be tested on a twin-outrunner powered aircraft, approx. 3000mm (118") wingspan, my own design.

Brg

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« Reply #11 on: July 08, 2015, 10:28:12 AM »

I'll break my confidentiality agreement with myself. My project was a failure. I wanted to reverse the props to slow down my 2 meter C130. Truth be told at the weight of my C130 all I really got was a lot of noise. With today's brushless motors and speed controllers, I think I would have gotten better results if one reprogramed the speed controller to stop the prop and then reverse the rotation of the prop. With controllers like the Arduino's, it should be possible to prototype this concept without having to make too much new hardware.

I wish you the best in finding a hub that will hold 1KW of power. As a guideline I've been told that the tail rotors draw about 15% of the helicoptor's engine power
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« Reply #12 on: July 08, 2015, 10:28:42 AM »

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« Reply #13 on: July 08, 2015, 10:43:42 AM »

One that had escaped me till last night was the unit sold (designed by?) Kress Jets, Inc near the millenium.  It was advertised as a two and four blade system in 10 to 12 inch diameter (used Graupner blades).  I never saw a price in the ads, and I have no idea how or how well they worked or if they ever got to market.  You might find something with a web search or on RC Groups, Watt Flyer, or RC Universe.  The advertisement  photos were impressive, tho.

I also think that Ramoser and a couple of other prop Guru's in Germany have in-flight, variable pitch (NOT constant speed) in the works.  I DO know that there are a few experimental units from various people in use (YouTube might be  helpful).  Nearly all are big bucks and based on a heli head with cut down chopper blades.  One that I had read about - with photos and a short vid - was a true, miniaturized CS, but was a fairly large diameter.
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« Reply #14 on: July 08, 2015, 10:52:13 AM »

I'll break my confidentiality agreement with myself. My project was a failure. I wanted to reverse the props to slow down my 2 meter C130. Truth be told at the weight of my C130 all I really got was a lot of noise. With today's brushless motors and speed controllers, I think I would have gotten better results if one reprogramed the speed controller to stop the prop and then reverse the rotation of the prop. With controllers like the Arduino's, it should be possible to prototype this concept without having to make too much new hardware.

I wish you the best in finding a hub that will hold 1KW of power. As a guideline I've been told that the tail rotors draw about 15% of the helicoptor's engine power
A quick search would have shown you a LOT of interesting results like this one.

http://www.flyinggiants.com/forums/showthread.php?t=77602

Heli blades might be inefficient compared to a "true" helical shape, but they DO work, and there IS work being done on the blade issue for VP/CS units (including dedicated - not modified from heli - hubs).
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« Reply #15 on: July 08, 2015, 11:42:58 AM »

I'll break my confidentiality agreement with myself. My project was a failure. I wanted to reverse the props to slow down my 2 meter C130. Truth be told at the weight of my C130 all I really got was a lot of noise. With today's brushless motors and speed controllers, I think I would have gotten better results if one reprogramed the speed controller to stop the prop and then reverse the rotation of the prop. With controllers like the Arduino's, it should be possible to prototype this concept without having to make too much new hardware.

I wish you the best in finding a hub that will hold 1KW of power. As a guideline I've been told that the tail rotors draw about 15% of the helicoptor's engine power
A quick search would have shown you a LOT of interesting results like this one.

http://www.flyinggiants.com/forums/showthread.php?t=77602

Heli blades might be inefficient compared to a "true" helical shape, but they DO work, and there IS work being done on the blade issue for VP/CS units (including dedicated - not modified from heli - hubs).
In my day we didn't have the internet. Besides that video showed much the same issue I had, lots of noise and stability issues with the attempts at nose down hover. With the lighter shock fliers I've actually moved vertically in a nose down hover. The best part of this gimmick is the backwards taxing.

Never said  straight blades wouldn't work, just that they were inefficient.

From my perspective my experience "Failure" is still a valid point, with weight and efficiency issues

Now what I'd have found helpful would have been a link to these new dedicated hubs. I assume that these have large thrust bearing and that the pitch arms are 90° to the blade mount slot ( Heli blade holders the pitch arms are in line with the blade chord). I like the way the props blades are held in the FAI F5B type hubs.

All the best,
Konrad
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« Reply #16 on: July 08, 2015, 03:49:06 PM »

If I had a link, or if there WAS one, I would have included it.  I had seen some of these prototypes at shows over here - mostly behind the counter - simply because I take the time an effort to talk to the people about what they hope to produce (ultimate goals), and some of these people won't "publish" until they get the proto working to perfection.  Most consumers spend their time asking about what they see at the stand, or what they have seen advertised.  One won't find much info at shows such as the Nuernberg Toy Fair (Nuremberg), 'cause the small companies (namely, one or two man operations) can't afford the cost.

It's easy to do the searching if one is REALLY interested, just takes a bit of time Wink.  IIRC the thread about the CV (centrifugally/spring operated) unit was on one of the sites I already mentioned, but then again, it might have been in one of the German model mags at least a year or so ago.
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« Reply #17 on: July 08, 2015, 09:43:31 PM »

Ah yea, I remember the Kress units! Shown with clear spinners so you could see the mechanism inside. At least the first versions used bent pushrods and eyelets to control the pitch, seemed to me there were a lot of slop in the system? And they were EXPENSIVE as I remember...

I am not going for the "heli" type of VPP, with the mechanism dangling outside the spinner, I want all to be concealed and it should be relatively easy to manufacture, preferably on a CNC lathe with C-axis.

Pit:
Thank you for that link! (y) I could use a setup like that on my Citabria! Smiley

Konrad:
Imagine your 2m Herc breaking in mid-air and do a backflip!?!? That would absolutely be a showstopper! Cheesy

I also recognize the feeling of waiting until you have a relevant, reliable and solid product until you advertise it, that's how you make money in the long run - instead of just whipping something together in a hurry, selling it with a flashy ad and then go out of business before anyone can complain about bad quality. I have a few designs, both airplane kits and other constructions that I can produce, but they are still in the design process - and will be until I find them okay. Then we might talk about fabricating and selling the products.

But every now and then I have a design that I want a second oppinion on, and then I offer a kit for testing. "Here, build and fly this, and tell me what you think!" Smiley

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« Reply #18 on: July 08, 2015, 11:17:21 PM »

Ah yea, I remember the Kress units! Shown with clear spinners so you could see the mechanism inside. At least the first versions used bent pushrods and eyelets to control the pitch, seemed to me there were a lot of slop in the system? And they were EXPENSIVE as I remember...

I am not going for the "heli" type of VPP, with the mechanism dangling outside the spinner, I want all to be concealed and it should be relatively easy to manufacture, preferably on a CNC lathe with C-axis.

Pit:
Thank you for that link! (y) I could use a setup like that on my Citabria! Smiley

Konrad:
Imagine your 2m Herc breaking in mid-air and do a backflip!?!? That would absolutely be a showstopper! Cheesy

I also recognize the feeling of waiting until you have a relevant, reliable and solid product until you advertise it, that's how you make money in the long run - instead of just whipping something together in a hurry, selling it with a flashy ad and then go out of business before anyone can complain about bad quality. I have a few designs, both airplane kits and other constructions that I can produce, but they are still in the design process - and will be until I find them okay. Then we might talk about fabricating and selling the products.

But every now and then I have a design that I want a second oppinion on, and then I offer a kit for testing. "Here, build and fly this, and tell me what you think!" Smiley

Brg

Pops-
Well it didn't "break" (fail) in mid-air nor did it "brake" (stop). Grin
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« Reply #19 on: July 09, 2015, 12:22:45 AM »

I stand (sit!) corrected! Cheesy Cheesy Cheesy

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« Reply #20 on: July 09, 2015, 12:51:32 PM »

I know, I should be the last person to call anybody on their use of the english language. I was having fun thinking that the crowd would stand to their feet as the C130 broke up in mid-flight. I've had enough models do that without the need of a variable pitch prop. :'(

All the best,
Konrad
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