Helicopter + Gyrocopter

Rotor Rooter

Dave Jackson
Proposal for a very simple ultralight VTOL rotorcraft.


The two primary features of this proposal are the worm & wheel gearing and the CVJ rotorhead.​


Double Enveloping Worm & Wheels:


  1. The gearbox simply consists of 1 worm gear and 2 wheels.
  2. The wheels are located on opposite sides of the worm and the angle between the 2 wheels is dependent on the 'V' angle between the 2 masts.
  3. The wheels can back drive the worm if the ratio is 10:1 or less, which should be advantageous for autorotation and synchronization.
  4. The double enveloping gears with a ratio of 5:1 have an efficiency of 95%. With a ratio of 8:1 the efficiency is 94%.
  5. For a comparison; the tail rotor on a single rotor helicopter consumes 10% of the power.
  6. If a pusher propeller is included then during cruise only 1/2 the power will be going through the worm and 1/4 of the power through each wheel.
  7. In addition, there is a power loss on a gyrocopter of 15% for the propeller to aerodynamically 'drive' the main rotor. This will be significantly reduced since each of the two main rotors are mechanically driven through their worm and wheel.

Constant Velocity Joint:


  1. The control system is by Weight Shift and the two CVJs allow the rotorheads to be pivoted in respect to their masts while still receiving fulltime mechanical power for rotation.
  2. One of the many advantages of the bilateral twin rotor configurations is that the weight-shift pivot can be high. This, and the smaller diameter of having twin rotor disks, minimizes the control effort of the pilot.

____________________________

Hopefully, this concept may stimulate the interest of the technical and the practical. Perhaps, through group thinking and doing, it will lead to multiple realizations of viable recreational rotorcraft and radio-controlled models by those who aspires to build better rotorcraft.

Please find fault and/or offer suggestions for improvement; by anyone and for anyone.



Dave
 
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brett s

Gold Supporter
A tail rotor doesn't consume 10% of the power all the time, in a no wind hover it's usually closer to 5%. But you already know that & like to use numbers that make your idea look better...

5% loss in a single worm gear means a ton of heat to get rid of.
 

hillberg

Newbie
worm gears as shown don't like coast down. rather have simple spur gears.
Drawings are fun but unless you build it the idea just sits as paper it's unproven & filler for the waste bin.
Build something,
 

Rotor Rooter

Dave Jackson
Originally Posted by brett s .....But you already know that & like to use numbers that make your idea look better...
Brett constructive criticism and openly suggested improvements are appreciated by myself and hopefully by others. However, it is a shame that you felt the need to deigrate the author at the very inception of this thread.

If you would like to revise post #2, I will then revise this post #4


_________________________________​


Re: Tail Rotor:
A tail rotor doesn't consume 10% of the power all the time, in a no wind hover it's usually closer to 5%.
  1. For decades, Western aerodynamic texts have mathematically shown that the tail rotor wastes 8 - 10% of the power. Kamov has stated in an article entitled Aerodynamic Features of Coaxial Configuration Helicopter that "the single-rotor helicopter's tail rotor power consumption accounts for 10-12% of total power."
  2. Stepniewski in 'A comparative study of Soviet vs. Western Helicopters' says that the tail rotor consumes approximately 11% of the power, during hover.
  3. The aerodynamic text (year 2000), by Leishman (University of Maryland) supports Kamov's position.
  4. Therefore, if a craft's gross weight to empty weight is 2:1, a loss of 11% will result in a difference in payload of to 22%.
  5. Prouty says, "... tail rotor absorbing 10 to 20 percent of the engine power". ~ [Source ~ RWP5 p.35]

Re: Worm & Wheel Reducer:
5% loss in a single worm gear means a ton of heat to get rid of.
Drive train for the Proposed Intermeshing Flettner Fl 339 ~ before Double Enveloping Worm Gear Drives were being produced:



Different Types of Worm Gears: There are three different types of worm gearing: non-throated, single-throated, and double-throated.



In this Article on satisfying higher energy efficiency demands with worm gear reducers the graph shows the Double Enveloping Worm Gear Drive as having a greater efficiency, below a 10:1 ratio, then the Helical Bevel Gearing (which is used on just about all major helicopters).
Those who have an interest in considering, developing and perhaps building a 'new' rotorcraft may find the full page of interest.


Dave
 
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Rotor Rooter

Dave Jackson
Don,

Thanks your comment may be a valid one.
Worm gears with ratios of 10:1 and below will back-drive. But, this may result in high friction, simply to turn the worm. :noidea:


Your concern about stopping the 'designing' and start the 'building' is fair statement, and it has been expressed by others. However, from my perspective, a project will only move beyond the design and component testing stages when it shows absolutely no terminal limitations. Enough problems will arise in the building and subsequent testing.

From a life in the manufacturing industry, I have seen too many projects rushed to the manufacturing department while the engineering department is still 'finishing off a few details’.
It would be interesting to know how many hundreds or thousands of rotorcraft builds were started and how many of those became viable craft.


Without elaborating, Sikorsky and Nick Lappos never complained about my posting of ideas. :)



Brett,

Yes. Nick and I have had some enjoyable arguments. You must remember that he works for the company that is responsible for the promotion of the tail-rotor concept. Hell, Igor was so enthralled by the tail rotor that he put three of them on his first helicopter.


As I recall, Leashman's first book gave the current Western mantra on tail-rotor efficiency. He then produced a number of papers on the coaxial configuration and revised the efficiency downward.


Dave
 

Rotor Rooter

Dave Jackson
Brett,

Thanks for the image but please note that he acknowledges that in forward flight the drag of the vertical stabilizer consumes power.


Dave
 
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Rotor Rooter

Dave Jackson
& some vertical stabs are just silly.:boink::wacko:
Pascal was initially having a lot of difficulty controlling yaw and since the battery life was only a few minutes long it gave him little time to do testing and modifications. He added the temporary large rudder so that he could devote more attention to other aspects of the craft.


Dave
 

LGoodhind

Member
>However, it is a shame that you felt the need to deigrate the author at the very inception of this thread.

Dave- you've been posting on this "let's all get together and design something that one of you guys builds" meta-thread for almost a decade, right?

When somebody says "build something" you need to remember that this group takes joy in staircases and NACA 0012 carved yard sticks driven by a drill ... the way to eat a whale is lots of small bites with a tiny spoon. Dig in. It's really as simple as pigs 'n chickens.

I wondered the same thing when I read your suggestion of using worm gears to drive a rotor- worm gears simply stop when the driver stops because the helical gear can't be driven- from what I have read the compliance you would need to build into a system that uses them to prevent backlash may make them a bad choice in certain applications but I have no real experience to base that on other than my erector set ferris wheel and that was in 1973.

I wouldn't take offense at the spanking; it was pretty gentle and the purpose appeared to be to get you to engage your gears as both the driver and the driven.

Peace love and donuts.
 
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Doug Riley

Platinum Member
"Meta-thread;" I love it.

A project that departs from the state of the art must do so for a good reason; otherwise, all that "innovation" is just wasted time, money and effort to get to a place we already have reached.

The innovator, if he's going to be rational, has to state precisely what problem with rotorcraft he's trying to fix.

IMHO, the old "problem" of power wasted by tail rotors is a relic of the helicopter's infant years. Back in the 20's and 30's, the weight-to-power ratios of engines were much worse than they are today (3, 4 or more lb. per horsepower). Helicopters barely had enough power to hold themselves up, much less any to give away to a tail rotor.

But today, that 5% or 8% or even 10% just isn't that big a deal. I think that it's not worth agonizing over, much less worth the cost and complexity of a second rotor and drive and control systems. All aircraft lose some power to trim drag.*

We have small tail-rotor helicopters that work nicely. You can see them at flyins, follow Stan's adventures here or hang out at Homer Bell's.
_____________________
* One of my best flying friends was killed in an U.L sailplane that had been designed to have the least possible trim drag while also using a high-C.L. wing with very aggressive camber. The design put the CG aft at 40% of wing chord to balance out the tremendous pitching moment of that droop-edged wing. Such a plane, however, is airspeed-unstable and easy to stall and spin if you don't babysit speed every second. The cost of efficiency in that case was simply too high for a weekend sport plane.
 

Rotor Rooter

Dave Jackson
Hi Larry,
Dave- you've been posting on this "let's all get together and design something that one of you guys builds" meta-thread for almost a decade, right?
Yes, you are very right.
I have tried to cajole and to provoke others into discussing, developing, and perhaps building, rotorcraft that stepped beyond the existing.

Way back then just about anyone who dared to think beyond Benson got abused. Today, the tide has changed somewhat, but even recently Cita (backpack build) has left the forum, some will not enter the forum, and Fetters has been banished from it.

For my part, I will not build a complete rotorcraft when a flaw is discovered that cannot be overcome, by me or by others. Perhaps the only 'build' will be my www.UniCopter.com 'workbook'; which is freely available to all.
:noidea:​



You and Don expressing your concerns about not being able to back drive the worm is one of the wonderful features of this forum. It allows potential problems to be raised and potential solutions to be offered. It also allows anyone to, publicly or privately, put that idea to use, if or when it looks viable.

P.S.
One of the problems of low ratio worm & wheels is there inability to hold position.
Thanks, in part to Don's comment, I went to the Eng-Tip forum and this is an intriguing part of one posting "We are experiencing a problem with an overdriving worm gear box. The worm gear ratio is 100:1 which would suggest that it should (ideally) self-lock. However probably due to the high loads and vibration it is overdriving. It is probably also a function of gear teeth wear ............"


Dave
 

Rotor Rooter

Dave Jackson
Doug, thanks for your valid post and points.

To argue the other side;

IMHO the gyrocopters and the helicopters (Mosquito and Helicycle, etc.) are excellent as recreational vehicles.


My 'Unhumble' objective is to 'discover' a utilitarian VTOL craft that can be a meaningful entrant to the next generation of rotorcraft.


The objection to the tail rotor is two-fold (or more :) ).
One is the inefficiency combined with the eventual use of electrical power.
The other is to remove the current difficulties in piloting a rotorcraft.​


Dave
 

L_Butler

N41423
Analysis paralysis

Analysis paralysis

Dave,
I have enjoyed your posts over the years, in fact, about ten years ago I wished you luck in your build. I find it difficult to believe you haven't accomplished anything yet.

Over the years, I have read many of your posts and have wondered if you are going to analyze everything ad nauseum or try something and hopefully advance the sport.

What does this mean? "My 'Unhumble' objective is to 'discover' a utilitarian VTOL craft that can be a meaningful entrant to the next generation of rotorcraft."

Really Dave, what is your objective? Small personal craft or large family wagon? Simply throwing out ideas for alternate methods of flight without defining a purpose is a time waster for everyone involved. Although the people on this forum can be nasty at times, everyone here would like to see you succeed.

I've been rooting for you to show us a better way or show us what you have learned that will advance the sport. I'd love to incorporate some new ideas in my craft.

Thanks,
Larry
 

Rotor Rooter

Dave Jackson
Larry,

Your comment about 'Analysis paralysis' and similar ones by others is fair. The comment is particularly valid when one considers that the majority of participants on this forum are kit builders, modifiers and fliers.

What does this mean? "My 'Unhumble' objective is to 'discover' a utilitarian VTOL craft that can be a meaningful entrant to the next generation of rotorcraft."
It means that mommy was right. A long, long time ago she said that "my head was trying to do things that my hands could not achieve."


__________________________​

More;



The UniCopter site shows a progression of 'ideas'. Each one was developed until one or more fatal flaws arose.
All of these flaws have been publicly stated in red as Concerns:. This is quite different from those who do not publicize their problems, perhaps because they are trying to raise money.
_______________​

The first project, the SynchroLite, was done on the earlier recreational rotorcraft forum. It was ready to be built when it became obvious that the necessary price and potential ease of piloting would not be of interest to the recreational rotorcraft community. The new Mosquito would best serve this group.

From there I migrated to PPRuNe and the discussions and development was directed toward larger rotorcraft. With new sets of Concerns:.

From there to this forum and the persuit of microlight Electric helicopters. The Electrotor-SloMo ideas still look very good. But Chuck was correct in questioning the time it is taking to develop viable electrical storage.

This latest effort is basically the Electrotor-SloMo, but powered by an engine instead of motors, while waiting for batteries. This latest effort should be low-cost, provide VTOL, and allow others to publically consider variations, which some may change to or continue on their own path.




Dave
 
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davh12

Newbie
Yep, i must admit that I have been intrigued with some of your designs over the years. I was curious about the worm gears being too slow? I'm just accustom to seeing worm gears in seed spreaders and garden tillers because it slows the out put shaft down. Or maybe I'm seeing it reversed. But I have to be honest: that the picture that you posted with the power plant and worm gearing eased my doubt a bit. Ever think of building small scale RC to test validity?
 

Rotor Rooter

Dave Jackson
Ever think of building small scale RC to test validity?
Yes, but the MicroLite craft is so small and light that it might be more practical to design [as outside parties critiqued it :help:].
Then build the primary components, and then the build the full-size craft.

Also, R/C actuators have increased to the size that a full-size craft could be tested by remote control.


A Constant Velocity Rotorhead has already been designed for a twin rotor 550 lb helicopter Hub - 3-blade CVJ w/ Hub Spring, and only needs to be simplified for weight-shift control etc. Alternatively, a double universal joint could be used.

This is information on the Winsmith ~ Double Enveloping Worm Gear Reducers. Unfortunately their smallest worm & wheel are too big.


So far, so good.

Dave
 
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LGoodhind

Member
>Yes, but the MicroLite craft is so small and light that it might be more practical to design [as outside parties critiqued it ].

The major cost for a rotorcraft is the engine followed by the rotor- you just spent 75% of the budget for a microlight KISS solution. How do you figure a full size model is more practical? What's your limiting factor? A two stroke line cutter gives you a motor and Benson blades could be built 1/5th scale on a dining room table.

There is a serious pigs and chickens issue that is a barrier to entry for your described effort related to the time, money, and potential for blood loss that I am failing to describe in an engaging way- thank God for wikipedia.

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

Rotor Rooter

Dave Jackson
Larry,
The major cost for a rotorcraft is the engine followed by the rotor- you just spent 75% of the budget for a microlight KISS solution. How do you figure a full size model is more practical?
I agree 100% with your remark, particularly if there are serious concerns about the flight dynamics of a ‘concept’.

That Chicken and Pig story is a good one :), but I am not thinking of the Wikinomics approach; again. This time I am willing to be the pig and personally fund and build the initial prototype. The major costs for this first-off will be the design time, plus the outside casting, fabricating and revising etc. of the 3-gear worm & wheels Gearbox and the Constant Velocity Joint - Rotorhub.

The additional cost at this time to produce a 2nd, 3rd or 4th of the non-standard items, such as the castings for the gearbox, will be relatively insignificant. They could be given to others who have acquired a genuine enthusiasm for the possibilities of the rotorcraft as the prototype moves forward.

They could then build their own variant of the craft, and/or, become the manufacture of one of the ‘unique’ components. My interest over the past 15 years has always been the challenge of conceiving and then prototyping a better VTOL craft. There is absolutely no way that I will get back into the manufacturing business.

___________________​

Custom blade(s?) and the probable(?) need for collective-change have yet to be fully considered, and perhaps discussed, for this concept. But potential solutions for both exist. The objective is to produce an engine driven version of the Electrotor-SloMo


Dave
 
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L_Butler

N41423
Schedule

Schedule

So Dave, when do you expect to start cutting metal? By you, I mean anyone you designate to do the actual fabrication.

Larry
 
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