Design and construction of a cheap 1-2 seater helicopter

[FredGarvin]

The thing with pulse jets on the tips, you run into some issues like getting fuel to them through a complicated mechanical system of blades and swashplates. Also, they are extremely loud. Also, helicopter blades need to be twisted so the angle of attack where the pulse jet is is not in line with the plane of rotation. That may or may not be an issue.

 

[Guinea_Pig]

those are fair points that i had not considered. angle of attack of the pulse jets id imagine are a big deal. i wonder what the tip speed is... maybe even ram jets are feasible its about 400mph is it not where they become effective...

i guess that a hollow mainshaft would allow fuel to pass through, and maintain a 0* AOA on the engines could be achieved by a feathering shaft the length of the blades. OK so you are increasing the rotational mass... but surely that's a pretty good thing as the more energy stored in rotation the longer you have to auto rotate etc... if you guys would like i could draw up a crude diagram as to how i would address those issues.. and you guys can point out where I am being stupid (as I am certain i have missed a point)

 

[JerryL]

I don't know if anyone is still using this thread, but there is the mosquito helicopter kit for around $35,000. And as for using a transmission. I believe rotorway's scorpion and the mosquito both use belt drives for main rotor power with the redution achieved by a much larger pulley on the rotor shaft than the motor output shaft. Using a large cog belt they have become much more reliable.

 

[Orion84]

Hello, this thread made me sign up

engine wise it has got to be a motorbike engine. I am into my Bike Engined Kit cars and am embarking on an R1 Powered one... this engine... 132Kw (180hp) from a new one at 12500rpm and the engine can't weigh anymore than 70kg... oh and that includes a 6 speed sequential gearbox... not that you would need it... also turboing such an engine is fairly realistic and as you run a helicopter at constant RPM setting a safe level of boost would be feasible and could be set up to not be detrimental to the engine or performance... i fly RC helis also so do have a basic understanding as to how helis in general work...

The small problem with that engine choice, or even the one I was thinking (Rotary engine) is that conventional autmotive ICE's are not designed to sit at their max rpm or peak hp RPM for extended periods of time. They are designed to be brought up to peak hp, then shifted, thus dropping to lower RPM and reducing the amount of heat created. So with that in mind you can not choose an engine based on it's peak numbers, but more it's useable numbers. You would want an engine with a flat torque curve and suitable hp at that tq. I was thinking that with a properly built 2 rotor (12A or 13B, or even the 16X which makes me giddy) I could have 200+ hp (300+ in the case of the 16X) at 10K RPM. The flaw in that plan is the engine would need ridiculous cooling to cope with those prolonged high engine speeds. Rotary's are notorious for their heat production, but at 12.5K, a bike engine would be boiling it's coolant as well. Running it at a lower RPM with gearing would make it more suitable, but also drastically reduce the hp available since such small engines make it all up top. Turboing the engine would indeed give you the higher hp/tq at lower RPMs, but again it comes back to heat. Sustained RPMs with boost, even at 4K would create a lot of heat, so a very serious cooling system would need to be in place. Since a helicopters forward speed is limited, so is airflow through the radiators, but big scoops increase drag and reduce speeds. Sitting and hovering would require the fans to be pulling a very large amount of air to cope with the heat produced by the engine strain caused by the increased load on the engine. The right fan choice wouldn't be hard. However all this adds weight. Unless you plan to fly for a couple minutes at a time then stop to let the engine cool down, there's no way around it, you must choose the right engine. Something more along the lines a of a larger displacement V twin engine -if we're thinking bike engines- would allow for the lower rpm/higher tq - hp needed.

 

[JerryL]

You don't need to run for long periods of time at full rpm, simply get a gearbox to drop you desired rpm down to main rotor rpm you desire, around 600.

 

[JerryL]

this small helicopter uses a 4 cyl subaru engine165hp. How large did you want to go?

http://www.ask.com/bar?q=hot+rod+helicopter&page=1&qsrc=0&ab=0&u=http%3A%2F%2Fwww.vortechonline.com%2Fhrh%2Fmain.htm

 

[JerryL]

your cooling wouldn't be limited to the crafts forward speed you have a very large cooling fan on the top of your craft forcing large quantities of air downward.

 

[Orion84]

I was thinking (read: dreaming) of using a 1.3L two rotor engine. Possibly the Renesis out of the RX-8. Claimed hp of 240 at the flywheel, however dyno results have shown it closer to about 210. I like the idea of the rotary. It's small, light, very powerful for it's displacement, extremely simple and reliable. Unless you throw boost at it. The 12A two rotor is known to be nearly indestructible as far as rotarys go. Can pump out 150 flywheel horsepower with just an upgraded carb and free flowing exhaust. Not that a carb would be the best choice in an aviation application, but they can be relatively inexpensive to convert to F.I.

Thank you Jerry, I completely forgot that a giant fan was actually what the motor would be driving. I can't believe I missed that. I guess a decent scoop would be more than enough to handle cooling duties.

Also I live up in Canada, so screw the FAA. Although I'm sure our counterpart would have some things to say.

Just to clarify for everyone, I just got it in my head that it might be cool to build a rotary powered helicopter. Not sure why but I've been thinking about it rather intensely for a few days now. I am a rotorhead, I own an 84 RX-7 that's been modded and just love what the engine can do. Maybe it's because I went to the Red Bull Air Races in Windsor, ON on the 14th, and the choppers they had performing were pretty cool. It won't happen. Hell, I can barely be bothered to go strip the useless wiring out my engine bay, so I can't imagine digging up the funds to have an airframe built, mold a body of carbon fibre and amass all the parts necessary, let alone properly engineering it. Not going to stop dreaming though.

Chris

 

[JerryL]

You could probably use the same basic plans as those for the Hot Rod Helicopter just tweek the motor mounting. That takes care of the engineering. Fabricate your own air frame as per the plans. I know what you mean I've been dreaming myself but no money for it.

 

[JerryL]

I've looked at many helicopter kit sites. There is a lot information you can get from them and lots of ideas to appropriate. I'd check the local regs. no point in getting a fine if you can avoid it. Good luck with your dream.
Jerry

 

[RonL]

If you are planning on building a ultralight FAA rule 103 limits max housepower to around 65 hp. You also don't need to runn for long periods of time at full rpm, simply get a gearbox to drop you desired rpm down to main rotor rpm you desire, around 600.

http://www.airweb.faa.gov/Regulator...8CF133AD5A5BA4B3862569DE005BD75A?OpenDocument

This might help anyone interested.

I don't think power is limited, but speed is (55 knots) or 65 MPH

Open the pdf doc on the right, I'm not sure if rules have changed recently.

Ron

 

[Orion84]

Thanks

Well I'll outline the idea I had.

Similar in shape to the Cobra attack helicopter but obviously smaller. Tandem seating, narrow fuselage with a twist. A propeller driven off the tail rotor shaft to provide forward thrust. As I mentioned it would use a rotary which creates a ton of heat, so there would be some ducting for the radiators and oil coolers and to allow hot air to escape, as well as a proper exhaust because an uncorked rotary would most likely cause the ears to bleed. They have a lot of exhaust energy, considerably more than a piston engine and can be quite unbearable even at idle if there is no muffler. Inflatable pontoons for trips up to the cabin. I don't have one, but I may get an invite one day. A pod type storage compartment underneath, similar in principle to the A600 Talon. It could also be swapped for an extended range fuel tank.

The theory being that the forward propulsion would allow the main rotor to deal solely with lift and turning and the propeller would handle forward flight, hopefully reducing fuel consumption. I know the added drag on the tailshaft would use fuel, but was thinking the forward propulsion would outweigh that. It would also provide a higher top speed and cruise. Disengage it for take off and landings, or use it in conjunction with wheels for a very short take off. This would aid in lowering the amount of fuel used for take offs. Body made entirely of carbon fiber, because it's light and looks real pretty. Plexi-glass bubble canopy, as well as part of the floor so I can see any ground obstructions as I land. Something along these lines would be great for long trips, as it uses regular 87 octane gasoline, and reduces travel time. I took a trip from southern Ontario to Manitoba last October and it was a 20 hour drive with cutting through part of the US. I was very tired afterwards. A vehicle like this would allow me to cut straight across Georgian Bay and hop over parts of Lake Superior, instead of driving around it. When it's gas time, simply land in a field near a gas station, and a few walks back and forth with a decent sized gas can and she's full and I'm off again. A little longer for fuel stops than in a car, and I'm sure I could figure out a better method, but time saved would be greatly increased compared to driving. Also how cool would it be to give your friends rides in a helicopter you built with your own two hands.

That's what was floating around in my head.

 

[JerryL]

Something I forgot. It is not necessary to build a airframe and mold a carbon fiber body.
Go uni-body combine airframe and body like the Mosquito XE
Jerry

 

[JerryL]

Sounds almost like an auto-gyro, except for the vertical take off. are you familiar with the principles of the auto-gyro? It's main rotor is not motor drive but driven by the forward airflow. I don't know about a prop pushed helicoper. A small company around Wichita Falls Texas is is working on a commuter craft slightly similar except thay want to use the rotor like a wing after vertical take off. The Have spent millions on the research. Last time I checked they were up to tethered tests. I think your rotor head and blades may be a bit fragile for too much push. Not really designed for it. you may talk to the guy who designs choppers he has the chinook helicopter logo by his user name if I'm not mistaken. You might stick with a regular Heli if you need the vertical take off, or an auto-gyro if not.
Keep looking around till you find the bits you want then put them together.
Jerry

 

[JerryL]

http://www.airweb.faa.gov/Regulator...8CF133AD5A5BA4B3862569DE005BD75A?OpenDocument

This might help anyone interested.

I don't think power is limited, but speed is (55 knots) or 65 MPH

Open the pdf doc on the right, I'm not sure if rules have changed recently.

Ron

It's been a while since I looked at them. My memory was faulty I have removed that error.
getting old I guess. (Regulation language causes brain Damage!)
Thank you for the correction
JerryL

 

[Orion84]

Actually during the Vietnam war era the US army (or a company did it for them) tried developing an attack chopper using a propeller to provide forward thrust. It was never put into production, I believe because the Cobra performed better or was more readily available for the war. This was when they were looking to replace the Huey gunship models with purpose built attack craft. Can't say for sure since it's been a number of years since I saw that show, so details are sketchy at best. I'll have to remember to look it up. Anyhow that's what gave me the idea in the first place.

 

[FredGarvin]

Actually during the Vietnam war era the US army (or a company did it for them) tried developing an attack chopper using a propeller to provide forward thrust. It was never put into production, I believe because the Cobra performed better or was more readily available for the war. This was when they were looking to replace the Huey gunship models with purpose built attack craft. Can't say for sure since it's been a number of years since I saw that show, so details are sketchy at best. I'll have to remember to look it up. Anyhow that's what gave me the idea in the first place.

You're thinking of the Cheyenne program. It's a shame since Sikorsky is essentially doing the same thing right now with a compound rotor version.

 

[JerryL]

I apologize for my Ignorance. I am not an engineer or helicopter mechanic. I had not heard of that helicopter design and was concerned about the increased stress on a motor driven main rotor, since it is the only thing holding the craft in the air. After having been informed about the Cheyenne I did some research and this link may be useful.

http://www.internetage.com/cartercopters/pics9.htm

This is an excerpt from the website below, it might warrant consideration.

http://www.ask.com/bar?q=Cheyenne+helicopter&page=1&qsrc=0&ab=1&u=http%3A%2F%2Fwww.aviastar.org%2Fhelicopters_eng%2Flok_cheyenne.php

The flight test programme revealed several significant problems with the aircraft's innovative propulsion system, problems which ultimately resulted in the fatal crash of one of the ten prototypes.

I admit it is a beatiful craft and if it could be done I wouldn't mind one myself.

Jerry

 

[vapl153]

Smallest, affordable, safe helicopter on the market: Mosquito
http://www.innovator.mosquito.net.nz/mbbs2/boxx/modules/mosquitohelicopters/contact-dealers-air.asp?dealerID=7

 

[Cyrus]

The Cheyenne is an interesting helicopter. I was talking with a retired air force colonel who knew test pilots that flew it. Every test pilot loved it because it flew like a fighter and not a helicopter. It has a rigid rotor system, like the Sikorsky ABC (Advancing Blade Concept) concept demensontrator. Note, both aircraft suffer from significant vibration problems, but the Sikorsky X2 has vibration suppression systems. Second note, this is not the first time Sikorsky has made such a helicopter.

I was told by people involved in this aircraft that it required three people to operate. A pilot, copilot and a guy on throttle. The guy on throttle was busy 100% of the time adjusting the engines that gave it forward propulsion and torque for the main rotors.

The x2 is different in that it has a rigid rotor with a significantly reduced rotor hub size. (The one pictured above is huge).

 

[JerryL]

How would you calculate the stall angle for the main rotor airfoil. You wouldn't your collective , cyclic total pitch angle to get that high. Stops to keep the pitch within a proper range wouldn't be that hard, but how do you calculate that range.

Some of you might want to check this site. They may start open a factory in Wichita Falls, Texas soon.

http://www.ask.com/bar?q=carter+copter&page=1&qsrc=0&ab=0&u=http%3A%2F%2Fwww.cartercopters.com%2F

 

[Cyrus]

I'm trying to identify the mission statement of this thread, and it's all over the place. Could someone close it, as PF is not the place to ask how to build your own helicopter.

Some of the posts are off-topic to making your own helicopter, but interesting. I think they would be better served moved into a new thread with a more reasonable thesis.

 

[JerryL]

I don't agree that this thread should be closed.
Any non distructive (homemade rpg not being one of them) project that open the mind to solve a problem is benifical. It gets someone thinking outside of their normal processes and perhaps gets them into an area that they would not normally consider. Or an area that they thought was beyond their grasp. Many people would not normally turn to physics, unless they needed it to solve a problem.

I see no problem with a thread about something that is not designed to intentionally hurt or maime another human being, but does challenge the imagination and intellect and relates to
physics. You must admit that there is lot of physics involved in the flight of a helicopter.

Jerry Lunsford

 

[Cyrus]

I don't agree that this thread should be closed.
Any non distructive (homemade rpg not being one of them) project that open the mind to solve a problem is benifical. It gets someone thinking outside of their normal processes and perhaps gets them into an area that they would not normally consider. Or an area that they thought was beyond their grasp. Many people would not normally turn to physics, unless they needed it to solve a problem.

I see no problem with a thread about something that is not designed to intentionally hurt or maime another human being, but does challenge the imagination and intellect and relates to
physics. You must admit that there is lot of physics involved in the flight of a helicopter.

Jerry Lunsford

I know the physics behind the flight of a helicopter, which is why I find this thread to be ridiculous. More to the point, I don't actually see anyone here building a helicopter. It's all talk.


Ta-Da:

http://www.rotaryforum.com/forum/forumdisplay.php?f=34

Lots of posts there, and better than what I've read here.

 

[JerryL]

After some research on NASA's website I found it is almost impossible to calculate the stall angle for an airfoil so thanks anyway.
Jerry

 

[JerryL]

I know the physics behind the flight of a helicopter, which is why I find this thread to be ridiculous. More to the point, I don't actually see anyone here building a helicopter. It's all talk.


Ta-Da:

http://www.rotaryforum.com/forum/forumdisplay.php?f=34

Lots of posts there, and better than what I've read here.

Yes, Cyrus you may know all of the physics behind helicopter flight but do you want to deny others who don't a place to do it.
I believe you would agree that a LOT of talk would be a good ideal before attempting to start a build. It would save a lot of time and possibly lives.
Do you consider this thread ridiculous because you think that an average person could not build a helicopter?
While building a helicopter is quite a challenge it is possible.

 

[Cyrus]

Yes, Cyrus you may know all of the physics behind helicopter flight but do you want to deny others who don't a place to do it.

I'm not denying anyone the place to do it. If you want to, by all means knock yourself out.

I believe you would agree that a LOT of talk would be a good ideal before attempting to start a build. It would save a lot of time and possibly lives.

Actually, no. I think you need to calculate something. Otherwise, all this 'talk' is worthless. You have to be able to calculate if you want to design your own helicopter.

Do you consider this thread ridiculous because you think that an average person could not build a helicopter?

No, an average person cannot build their own helicopter. The exception would be if they bought a kit and assembled it.

While building a helicopter is quite a challenge it is possible.

Yeah, uhuh. Okay.

I think you should read this review by Dr. Celi (who teachers helicopter courses here) on https://www.amazon.com/dp/0486682307/?tag=pfamazon01-20to give you some education on what you're proposing:

Looking for information on how to fly a helicopter? Look elsewhere. Trying to design and build your own helicopter? Yeah, right, how about performing a quadruple bypass on your own heart? But if you are an aerospace engineer interested in helicopters, or if you are studying to become one (an engineer, not a helicopter), this is a must-have book.
This *is* an advanced textbook, which will take you from the fundamentals of helicopter aerodynamics, dynamics, and flight dynamics, all the way to the advanced topics. The book came out in 1980, and helicopter engineering has made a lot of progress since then. However, much of what is in the book remains current. The extensive bibliography gives a comprehensive picture of the state of the art until 1980.

Want some bedtime reading? Get Patricia Cornwell. Want to read stories about airplanes and military hi-tech? Read Dale Brown or Tom Clancy. Serious about learning helicopter engineering? Get this book.

If you really, honestly want to build a helicopter. I suggest you start showing me some calculations if you want me to take you seriously.

 

[JerryL]

I can't show you any calculations as I do not have enough knowledge of aerodynamics to produce them.
Never the less, one day I plan to build a helicopter. I don't know how long it will take to scrape up the money and information but I intend to do it.
Until that time I learn what I can and design parts as I can.

 

[Cyrus]

I can't show you any calculations as I do not have enough knowledge of aerodynamics to produce them.
Never the less, one day I plan to build a helicopter. I don't know how long it will take to scrape up the money and information but I intend to do it.
Until that time I learn what I can and design parts as I can.

I guess I won't be taking you seriously then.

 

[Cyrus]

I can't show you any calculations as I do not have enough knowledge of aerodynamics to produce them.
Never the less, one day I plan to build a helicopter. I don't know how long it will take to scrape up the money and information but I intend to do it.
Until that time I learn what I can and design parts as I can.

I don't want to dissuade you from aviation. I think it's great that you like helicopters. I just think your time and money would be better spent taking helicopter lessons and learning/reading the fundamentals of helicopter flight so you have a better respect for it.

There is a reason why it took guys with engineering degrees to design the first helicopters. Unlike airplanes they are far, far more complex.