1 Blade Propeller

[Guest Michael Coates]

One of two flying single blade J-2 cubs

 

 

This is super interesting andtotally bizarre, so I did a little research. The idea is that a single blade would be more efficient than multiple blades because the single blade is always travelling through undisturbed air. The propeller is counterweighted and mounted eccentrically on the hub to keep it balanced. It also has fore-aft pivot so the prop pitch self-adjusts to the most efficient angle - you can move the tip of the blade forward and back several inches with your hand.

 

Apparently the design worked; in 1939 the Everel prop was tested on a Taylorcraft in a race and won by quite a bit. However, shortly after the introduction of the prop, powerful 50HP engines were developed which rendered the efficiency gains of the single blade moot. Considering that the balance of the prop was very fickle in changing weather, the already mechanical complex prop just wasn't worth the effort, so the design never caught on.

 

It's a nifty bit of engineering and a cool piece of history.

 

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[Coop]

Sort of reminds you of an amputee.

 

I wonder if you broke one end of a prop in the outback, could you saw it off, and add some weight so it was still balanced around the hub and then fly out? I suspect the pitch might be a bit too fine, but would there be any other problems?

 

Coop

 

 

[Guest aviatrix27]

go to the museum in Alice Springs where the airport used to be - there's a broken prop there and its story

 

 

[willedoo]

go to the museum in Alice Springs where the airport used to be - there's a broken prop there and its story

Kaye, is that the one from the plane that landed on Lake Armadeus looking for Lasseter's gold, or another one .

 

Cheers, Willie.

 

 

[siznaudin]

One of two flying single blade J-2 cubsThis is super interesting andtotally bizarre, so I did a little research. The idea is that a single blade would be more efficient than multiple blades because the single blade is always travelling through undisturbed air. The propeller is counterweighted and mounted eccentrically on the hub to keep it balanced. It also has fore-aft pivot so the prop pitch self-adjusts to the most efficient angle - you can move the tip of the blade forward and back several inches with your hand.

 

Apparently the design worked; in 1939 the Everel prop was tested on a Taylorcraft in a race and won by quite a bit. However, shortly after the introduction of the prop, powerful 50HP engines were developed which rendered the efficiency gains of the single blade moot. Considering that the balance of the prop was very fickle in changing weather, the already mechanical complex prop just wasn't worth the effort, so the design never caught on.

 

It's a nifty bit of engineering and a cool piece of history.

I thought I could remember from way back ... single blade props from control line model racer aircraft ... Googled it up, and hey-presto!

 

It's almost Python-esque to watch, but of course, deadly serious stuff.

 

 

[Guest Michael Coates]

Thats just crazy. Imagine the loads on the lines, breakage etc... I dont know why it started he god it going them kicked in like a supercharger.... what did that ?

 

 

[mnewbery]

I dare say it was a human operated throttle. I will try to find out more

 

 

[mnewbery]

http://naa.aero/siteadmin/data/document/SC4_Vol_ABR_13.pdf

 

Section 4 – Aeromodelling

 

Volume ABR Section 4A, Section 4B, Section 4C

 

2013 Edition Effective 1st January 2013

 

Section 4c Clause 1.3.2

 

(...)

 

b) Powertrain control may be accomplished by the pilot via the wires or cables or by an onboard self- contained, automatic process.

 

 

[Guest aviatrix27]

the one in the museum at The Alice - he was flying a surveyor around. I can't remember why he landed, but the prop broke and his passenger was injured. He helped his passenger with some first aid, got him some shade, used the broken piece of prop to clear a bit of a runway, matched the prop so that it was really short both sides. To cut a long story short, eventually he took off and went for help. He should have got a medal, but his licence was taken off him. Long story - go read it :)

 

 

[Coop]

Yes, I've seen the one at the Alice and read the story.I think he damaged both ends, one more than the other. He used an axe to shorten the long end and balance it up. When he got it flying, it would barely stay aloft, despite the engine doing around 3,000 rpm (usual max is 2300- a tribute to the durability of the Gypsy Major Engine). He flew mostly in ground effect, but was able to use a thermal to gain some extra altitude (and rest the engine a little) on a couple of occasions.

 

What I was asking was whether it would be possible to shorten only one end (if the other end was still intact) and balance it by adding some screws. bolts, etc. Because of the reduced length the force trying to drag the metal out of the short end wouldn 't be beyond the strength of the prop. And you might get a better result than balancing it by shortening both ends.

 

As for the control-line speed event. I have seen this run at a modelling comps at Waikerie many years ago when the world record was around 150mph. The record was broken at that meeting. In that competition, they controlled altitude by twisting the wire- that's what the little handle he is holding does. The use of the pivot is to ensure they can't "whip" the model to gain more speed. THey have to complete at least 10 laps with the handle mounted on the pivot. When I was watching, they had balloon fuel tanks that they inflated with a big syringe which provided fuel under pressure to the engine. The pulling on the wire beforehand is to ensure it is up to the load that will be imposed when it is in flight.

 

It is a crazy comp, but watching (from what I hoped was a safe distance) it was very impressive!! The little models are beautifully made.

 

Coop

 

 

[geoffreywh]

The video is of FAI speed . Two lines. 2.5cc , straight methanol and castor oil. No nitro. The aircraft is "whipped " up to speed and when the model comes "on the pipe" (tuned length expansion pipe ,it's a two stroke remember) the pilot put the handle in the cradle for 1 km....I don't know what the record is now, But it used to be 250+ kph...The model is asymmetric to cover as much line as possible to reduce drag....Fun to do....

 

 

[eightyknots]

One of two flying single blade J-2 cubsThis is super interesting andtotally bizarre, so I did a little research. The idea is that a single blade would be more efficient than multiple blades because the single blade is always travelling through undisturbed air. The propeller is counterweighted and mounted eccentrically on the hub to keep it balanced. It also has fore-aft pivot so the prop pitch self-adjusts to the most efficient angle - you can move the tip of the blade forward and back several inches with your hand.

 

Apparently the design worked; in 1939 the Everel prop was tested on a Taylorcraft in a race and won by quite a bit. However, shortly after the introduction of the prop, powerful 50HP engines were developed which rendered the efficiency gains of the single blade moot. Considering that the balance of the prop was very fickle in changing weather, the already mechanical complex prop just wasn't worth the effort, so the design never caught on.

 

It's a nifty bit of engineering and a cool piece of history.

 

[ATTACH=full]1947[/ATTACH]

I have heard of this in the distant past, and then in a vague way. Thanks for bringing this example to our notice.

 

It's probably time for someone to try it on and LSA/ultralight plane and see whether the efficiency is worthwhile.

 

 

[gandalph]

Video of flying the J2 with the Everel single bladed prop Stay to the end for a better look at how it works.

 

 

 

[eightyknots]

Video of flying the J2 with the Everel single bladed prop Stay to the end for a better look at how it works.

Thanks for posting that gandalph .

 

 

[facthunter]

After I see a flock of one winged birds flying. Nev

 

 

[Bikky]

After I see a flock of one winged birds flying. Nev

In circles I imagine. Could be handy in circuits - "Look Mum. No hands!"

 

 

[Guest ozzie]

These single blade props are fitted to a pair of Silent gliders. They make it easier for the folding pylon. Engine is mounted down low and a belt drive to the prop. Owner claims it produces more thrust than two blades. Took these photos in Cassola Italy.

 

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[eightyknots]

After I see a flock of one winged birds flying. Nev

Birds use wings for Lift and Thrust.

 

An aircraft with two wings (for Lift) and one propeller blade (for Thrust) seems to me to be no problem. It's just a different set of design parameters to birds.

 

 

[facthunter]

It would have to be designed very cleverly to remove all unwanted loads from the engine shaft and mounts. The blade pivot would have to coincide with the crankshaft centre. THAT can be done, but it's limited to pretty simple fixed pitch, and IF we are really talking about efficiency, we don't have fixed pitch as the standard. Nev

 

 

[Soleair]

An aircraft with two wings (for Lift) and one propeller blade (for Thrust) seems to me to be no problem. It's just a different set of design parameters to birds.

A bit off topic, this, but may be of passing interest.

 

In a previous life, I worked on the automation of lighthouses around the British Isles. I spent several months (not consecutively!) on the tallest of these, Bishop Rock, which was on the migration route for some bird species. Every morning I used to walk around the gallery outside the lantern, and hurl the unfortunates that had flown into the glass (nav system confused by light?) over the rail.

 

These birds would invariably descend in a flat spin. There not being a great deal to do on a lighthouse after work, I attempted to improve the flight characteristics of these deceased aviators, to get them to glide. I tried extending their wings by affixing a coathanger - same result.

 

Then it occurred to me that since birds are all fly-by-wire they don't need a vertical tail surface. So the judicious application of a fairly large cardboard fin, fixed to the tail with some difficulty, improved the flightpath. Still needed some work on pitch control, though.

 

Bruce

 

 

[Riley]

A bit off topic, this, but may be of passing interest.In a previous life, I worked on the automation of lighthouses around the British Isles. I spent several months (not consecutively!) on the tallest of these, Bishop Rock, which was on the migration route for some bird species. Every morning I used to walk around the gallery outside the lantern, and hurl the unfortunates that had flown into the glass (nav system confused by light?) over the rail.

 

These birds would invariably descend in a flat spin. There not being a great deal to do on a lighthouse after work, I attempted to improve the flight characteristics of these deceased aviators, to get them to glide. I tried extending their wings by affixing a coathanger - same result.

 

Then it occurred to me that since birds are all fly-by-wire they don't need a vertical tail surface. So the judicious application of a fairly large cardboard fin, fixed to the tail with some difficulty, improved the flightpath. Still needed some work on pitch control, though.

 

Bruce

Yer a daft basterd Soleair but (having been an asst lighthouse keeper myself in a previous life) I can understand your need for a meaningful project whilst on the rock. cheers Riley

 

 

[Mike Borgelt]

I don't think the second blade operating in the wake of the second is at all relevant unless not moving forwards.

 

At 2500rpm the prop goes around 41.67 times a second. a two blade prop means a blade passes 83.34 times a second. At 100knots (close to 50 meters/sec) this means the second blade passes 0.6 meters behind where the first one passed. The single blade prop advantage appears to be in some automatic pitch control with a simple offset hinge

 

 

[gandalph]

Mike, The rumour mill has a retired Aero engineer somewhere near Toowoomba close to finishing converting a Blanik sailplane to be self launching, powered by a 503 Rotax driving a single bladed self feathering prop. I believe he has studied it all very thoroughly and is satisfied that his proposed setup will give him the greatest efficiency.

 

 

[rankamateur]

Would he be south of Toowoomba?

 

 

[Mike Borgelt]

The prop on my Ventus TOP when it had the TOP fitted was 3 blades and meant to be quite efficient. Funnily enough the blades looked like the ones in this article: http://rexresearch.com/lippsprop/lipps.htm

 

Scroll down to "the single blade myth" but do read the rest of the article. Full of good stuff. I'd like one of those on our BD-4.

 

I think the single blade prop on a motorised Blanik may have more to do with the self feathering bit.