Another Homebuilt heli gets going

[Sita]

another homebuilt heli
YouTube - ‪CLIP0057bug mk 4 helicopter third hover‬‎


cita

[Jincamty]

Doug, I know it's a hassel converting taped videos, but I'd love to see more of your old testing. I'm having "helicopter testing withdrawls" being stuck inside, from our crap weather over here.

Cheers Cam.

[Jincamty]

Please, help needed from the helicopter experts.
I have a problem with a bad low frequency vibration as I approach approximately 15-20km/hr or lifting up into the wind. It comes on quite fast and remains until I come to a complete stop... At hover, it's very smooth.

I had an "Ahaa" moment after watching a great video about Arthur Young.
(3:10 describes the exact symptoms)
The Birth of the Bell Helicopter (Part 3) - YouTube

It seems I'm getting into some sort of chord wise resonance?.....
Are there any other reasons that would cause these symptoms?

I have a camera mounted on the rotor head looking at a split image of both rotors to see any chord-wise flexing (and other things), But I am waiting for some descent weather.

Below is a compilation of the progress.
You can see in one scene (fast motion)(5:26) where I'm going clockwise around the goal posts and have to pullup due to the "shaking". It seems to happen at the same place consistently.

(Please excuse the tacky video, it was made to entertain the family.)

Homebuilt Helicopter compilation (part 1-9) - YouTube

Cheers Cam.

[Doug Schwochert]

Hi Cam

need a little info to figure out the problem

1 undersling in inches.
2 degrees of coning angle
3 disc diameter in feet
4 rotor rpm
5 degrees of rotor teeter

it looks to me from the video you may not have enough undersling

just my uneducated opinion

Doug

[Jincamty]

Thanks Doug,
I did wonder about that. I can change the undersling, but it's not a five minute job.

Some numbers for ya.....

Undersling = 2.56" (65mm)
Pre-cone angle = 3 degrees
Disc diameter = 21' (6.6m)
RRPM = 485
Degrees of rotor teeter = +-5.5 degrees (just touching rubber stops)

Mass of blade = 30 lbs (13.6kg)
Tip weight = 1.76 lbs (0.8kg)
Centre of mass = 52" from root (1.346m) (that doesn't sound right?)

Doug, while I have your attention ;-) ,I notice on some old photos of the AW95, you appear to have added pitch/flap coupling? What effect did that have?

Cheers Cam

[HobbyCAD]

Would you mind posting your blade chord and AUW as well? I would like to do some calcs myself.

Thanks,

Francois

[Jincamty]

Thanks Francois,

7" chord
AUW = 726lbs (330kg)

[Jens]

Exciting homebuilt project - looks great. Very well done!

[Doug Schwochert]

Hi Cam

Did you measure your undersling from the center of the teeter bolt to the center of the rotor hub plate? if you did your undersling should be in the ball park.
the rotor RPM seems to be a little low for your disc aera. and your coning angle may be 1 degree too much. 2 degrees per side seems to be about the average.teeter is about right I measured mine it has about +-7 degrees.
you are close to being the same weight and disc aera as the helicycle. if I try to fly my Helicycle with the rotor RPM at any less then 580 (615 is normal) it shakes and vibrates like crazy. If I were doing the job I would make the coning angle 2 degrees per side. and speed up the rotor speed to about 550 looks like a drive gear change is easy enough. But then you may need to cut your tip weights about in half. not knowing how the rotor head is constructed the extra centrufugal load on the blades may be too much. The way you design a helicopter today is copy the specs from another helicopter that is about the same size and weight.
The off set pitch links on the A/W 95 were an experiment to see if I could gain more stability. how they were suppose to work was as the disc flaped up or down the pitch of the blades would increase or decrease. I guess it may have worked a little bit maybe.don't know for sure. it was hard to tell if there was much difference. they were eventualy change back to normal later on.

Just my uneducated opinion.

Doug

[Arnie Madsen]

Jincamty .... by video #5 you were hovering as good as any rookie helicopter pilot .Very good. Love your progress .

Your son has a cool dad and his camera skills are excellent. His commentary is genuine.

I am amazed by how smooth your helicopter flies . Forward speed vibrations are typical snags all pioneers encounter.

Arnie

[rotor46]

Originally Posted by choppergabor

What a complete ignorant idiot! That guy has either no training or very little. Hopping backwards just asking for digging the skids in! The hopping sideways with touchdowns asking for dynamic rollover. No helmet on the guy and he had absolute no control over that machine. Oh and he had the great idea to take his son along maybe he could witness Daddy being made into Sushi. And he puts this on Youtube? Wow. I am getting too old I guess. Should have named it "How to get killed in a few easy steps"

For a self-taught builder and upcoming heli pilot, the gentleman has done remarkable well; he doesn’t deserve to be called an idiot. You attitude is reprehensible and an abuse of friendship to those members that support your membership on this board.

[choppergabor]

Originally Posted by rotor46

For a self-taught builder and upcoming heli pilot, the gentleman has done remarkable well; he doesn’t deserve to be called an idiot. You attitude is reprehensible and an abuse of friendship to those members that support your membership on this board.

Ouch my previous straight to the point post was deleted! OUCH! Well it seems you have a problem with me so I invite you to settle this in private so it does NOT get deleted. I always wonder what really is behind one's actions like yours.....and than I suddenly remember I don't give a rat's a$$............ Do NOT patronize me or my attitude as you have no business doing so. No one asked you to be the defender of the weak and helpless. I am waiting for you private gum flapping dude. Go for it!

[HobbyCAD]

C'mon Gabor, let's be civil here. The guy posts a negative thing about you, using civil language. How about you respond with the same civility. No need to start a bunfight by calling him an a$$hole. Call him an idiot if you like, no problem, but you jumped in boots and all, with "kiss my a$$, you a$$hole" My thread has no place for that.

Gabor, let's take a moment to reflect on things. No one took sides here. No-one was defending the weak. I simply deleted your short post in my thread, for calling the guy an a$$hole.

Hey, I think this Rotor46 guy now posting from Shandong is the same Perth based dude that has twice been banned, resurfacing again. I also think he is an absolute idiot, but I'm not resorting to such insults as you were doing.

[Redbaron]

Originally Posted by HobbyCAD

C'mon Gabor, let's be civil here. The guy posts a negative thing about you, using civil language. How about you respond with the same civility. No need to start a bunfight by calling him an a$$hole. Call him an idiot if you like, no problem, but you jumped in boots and all, with "kiss my a$$, you a$$hole" My thread has no place for that.

Gabor, let's take a moment to reflect on things. No one took sides here. No-one was defending the weak. I simply deleted your short post in my thread, for calling the guy an a$$hole.

Hey, I think this Rotor46 guy now posting from Shandong is the same Perth based dude that has twice been banned, resurfacing again. I also think he is an absolute idiot, but I'm not resorting to such insults as you were doing.

If you kiss enough ass you eventually choke on ****.

[choppergabor]

Originally Posted by HobbyCAD

C'mon Gabor, let's be civil here. The guy posts a negative thing about you, using civil language. How about you respond with the same civility. No need to start a bunfight by calling him an a$$hole. Call him an idiot if you like, no problem, but you jumped in boots and all, with "kiss my a$$, you a$$hole" My thread has no place for that.

Gabor, let's take a moment to reflect on things. No one took sides here. No-one was defending the weak. I simply deleted your short post in my thread, for calling the guy an a$$hole.

Hey, I think this Rotor46 guy now posting from Shandong is the same Perth based dude that has twice been banned, resurfacing again. I also think he is an absolute idiot, but I'm not resorting to such insults as you were doing.

Yes he is the same guy. That is exactly why I handled him that way. Obvious what he was doing digging up a long gone post to pick a fight. Francois I don't back down ever from a good one but Albert46 or Rotor46 or whatever he changes his name to does not deserve anything else. Didn't mean to crap into your thread PM me your e-mail and I will let you in on something. You'll see my side a bit better I promise. Gab
ps: I wasn't directing the defending towards you and you were right to delete my post. I was referring to him doing it so transparently fake that was not even funny.
Again my apologies for dirtying up the thread.