Minimum Rotor RPM
 

The application is a human powered helicopter. Yes, human powered.
I cannot generate the 470HP as supplied for the 1500 Ft/Sec ascent a factory Bell 206B is equipped with, but pehaps I can get my craft to hop. Any thoughts on a minimum Rotation RPM at zero pitch, the applying a 7 to 10 degree collective pitch using a Bell 206 Rotor? Vehicle gross weight is just over 500lbs. I am not looking for an engineered response, (unless you have one), merely an experiential case in point when a Bell 206B copter had hopped due to a __________. Any thoughts from you, the professionals, and your experiences would be a great value to me.

470 HP?
 

I would have thought 470 HP is somewhat more than the main Xmsn is rated for? ( But someone correct me if I am wrong ! :ugh: - VFR

Can I just get a few things straight here...

You are:

Intending to human-power a 206 main rotor?

... with 7 - 10 degrees of pitch?

Expecting to get this 500lbs of machine off the ground - even to hop?

Well, thinking about it - if you can get a decent rpm (Yes, I know that was your question) and have some sort of mechanism that snaps pitch on the blades very quickly - like a jump-start autogyro - the high inertia in the rotor system might give sufficient lift for a hop. Using the rotors as a flywheel really.

How will you control it if it gets off the ground?

In my day, the 206 xmsn was rated at 317hp, which equated to 100% Tq. regardless of engine installed. Originally the max rated output of a 250-C18. - I think.

How many humans are you planning to use? The 206B transmission is 317shp the 206L4 is a little over 450 shp.

HPH Hop
 

Thanks for the clarification on the HP, I appreciate the assistance. I am employing a cable enacted, hand operated, variable collective pitch control, (not sure how much effort that will take) , and then, providing I get positive test results on my spinnup test, I will hopefully be constructing a cyclical disk controller to employ 3 axis control. But, yes, I should be in Auto-rotation, given the input HP, as soon as it is off the ground. Given the airspeed will be next to zero, it could be an interesting ride.

HPH Hop
 

I can employ up to 2 humans, but that may bring the craft weight up to 700lbs. 510lbs + second human

The University of Maryland have build a prototype human powered rotorcraft with very lightweight material (approx 220lbs including the pilot) which they just managed to get off the ground for a few seconds.


Not sure how easy it's going to be to get over twice that much off the ground.

Best of luck though!

OH

HPH Hop
 

Yes, the weight is definately the most difficult hurdle, given the Bell Rotor weighs in at 184LBS plus the Hub to hold it together and provide pitch. The advantage is that it is inertia energy once it is airborne. Thanks for the support.
DB

Think you`d be better off with a B-47 rotor...

Interested to hear why you suggest that. A 47 M/R hub is more complicated (not talking stab bar here) and wouldn't 206 blades with their extra weight be an advantage?

HPH Hop
 

I used what was available. May have to go back to the DB. Design is for a coaxial craft. but I can modify all energy to single rotor.
I had hoped the weight would be an advantage to a point. I realize the Gamera, Yuri, and Da Vinci Crafts all were under 150lbs plus pilot, but they had no pitch control. The operated at full pitch from the start. No inertia, no storage.

Really? I'd like to see that - please post a video on Youtube asap.

It already is on Youtube.
 

If you view the rotor spinnup video, you can see I was able to get to almost 50 RPM, but the sprocket was too high ratio. I have just installed a lower ratio for more torque (3X), which I anticipate to increase RPM to 100+. Test is this Sat.
I was hoping to get some tips if this thing hops, recommended pitch settings to not stall the rotor, to safely lift, and if it does, Any pointers on how to survive...

Flat Pitch Power Required
 

If memory serves me correctly, it takes approximately 17%-20% to turn the B-206 rotor at 100%. That would be somewhere between 50 and 60 ESHP. This would get you to your starting point. Your system would have no accessories (i.e. hydraulic pumps generators or tail rotor take off) so the number would be somewhat reduced from the 50 to 60 ESHP.

Assuming it does 'hop', you won't be in autorotation as the term properly applies to helicopters, as significant rate-of-descent airflow and minimum pitch is required for that.

I imagine this is an attempt to win the Sikorsky prize? I guess it lets you store some energy without using flywheels or other storage devices (I just had a quick look at the rules on the web), which is fair enough, but in all honesty the weight of the setup compared to the power you can put in is going to be too much, I think, (not to mention control issues) to be airborne for more than a second or two, let alone a minute.

Best of luck though.

HPH hop
 

I see your point on the auto-rotation and the weight.
I will give it a shot and see what we can do.

I appreciate this blog and all of you that took the time to contribute, and had patience with me considering I am not a professional pilot.

Thanks again.

Can't wait until the day you tell us that your name is also a reincarnated,
Johnny Weismuller.

Tarzan swings,
Tarzan faaaaalls,
Tarzan hannnnnnngs,
by the hair of his balllllllllllls;

Banjo strumming in the background.

After reading all the pros and cons above. Whats the chance of getting a set of Skeeter main rotor blades, head and transmission? No it won't have high inertia, but will be considerably lighter than the weights you are discussing. To carry this statement to an extreme; make your own plywood and doped fabric blades, and utilize simple belt drive reduction. The head flap system would not be hard to make as its got a short usage life. Last thought is wear a good crash helmet.

HPH Hop
 

The Latter is my only option given the budget. That is the next step.
For now this is where I have progressed to (if you are interested)...
https://sites.google.com/site/hphbumblebee/

https://sites.google.com/site/hphbum...FBP1290378.JPG


You can see the rotor hub that I have created, and the size of the main torque tube, Frame, and some of the drive components. This is what I have to work with. I can build a rotor, and will probably need to, but much to learn in that realm and $$$.

What I have is at least worth a try. I will know this Sat. if this current config. is feasible at all.

A quick bit of google'idge reveals that a REALLY strong person can muster approx 0.7hp. Remember the power required to turn the rotor (rotor profile power), increases exponetially as a factor of the RPM ie to double it takes 4x power, to quadruple it takes 16x power etc.

I am intrigued by your plan and wish you best of luck, but mister physics says that you do not have a chance. Sorry.