What is Your Takeoff Angle ?

CLS447

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I am just curious...

On your gyrocopter , What is the takeoff angle of your hub bar ??

Takeoff angle = The angle of your hub bar when the nosewheel is on the ground & the stick is at full back.

Like when you start your takeoff roll before the machine tips back on the tail wheel.

As a side observation......Without the blades spinning, do your blades touch the ground at this point ?


While you are checking that......what is the angle of the hub bar when it is tipped back on the tail wheel ??

Again as a side observation....Without the blades spinning, do your blades touch the ground at this point ?


I can tell you right now that my 2 place, when back on the tail wheel & stick back & blades at full back the hub bar angle is at 31 degrees back .

I will check how much less when the nosewheel is down.


Is this figure interesting to anyone else here ??? & why ???
 

CLS447

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Wow !!!!! 119 views & not one response !

Does anyone else own a protractor ?

Maybe tommorrow ?

For livelier discussion , I would like to predict the end of the world.....July 19, 2011 ( my birthday)

What do you think of me now ??
 
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cgmg

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Chris,

It's only been about 12 hours since you asked. Most people have to work for a living during the daytime, if they're lucky. So be patient, and maybe you'll get some more answers over the next couple of days.

I just checked my notes on my RAF, and here's my angles:
-1 degree forward tilt
18 degrees rearward tilt(RAF recommends 19-20)

RAF also recommends 10-12 degrees tilt, from center, for both left and right lateral trim. Don't recall, and don't have any notes, regarding what mine actually is.

My blades will easily touch the ground if spun around by hand sitting level. I've never measured the head angle with the tail down, what difference would it make if you have the proper travel with the keel level?
 
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Alan_Cheatham

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Your probably not going to get many replies, it's like asking how many licks does it take to get to the Tootsie Roll center of a Tootsie Pop?. :D

.
 

CLS447

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Mark, Thanks ! Your post got me thinking a little further.

Larry B. mentioned those numbers to me yesterday. The RAF is a bit of a different animal in some aspects but....

I am thinking that the rotorhead (that has adjustable stops ), has a full range of about 18* .......9 front & 9 rear from center. But I guess that you are saying that with the nosewheel down on the ground & stick full forward, ...........

When a protractor is placed on the torque tube, it should be adjusted so that it only tilts 1* forward Right ???


When flying is the nose hanging down more than it was on the ground ?
 

scottessex

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My protractor falls off the hub bar when I prerotate...... :)
 

Penguin

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When I put the protractor on the hub bar I keep getting my fingers whacked by the rotor ...
 

CLS447

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Scott, I used JB weld & mine is yet to come off ! What kind of glue are you using ?

The magnet will not stick to aluminum.
 

CLS447

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You know what....This hole thing is getting scattered. I should stick to one question at a time.

But this is the kind of theory that I enjoy....the mechanics of it all.

I don't know about anyone else but I am not too thrilled when spinning parts can come in contact with fixed parts !

But I have been thinking alot about this stuff & don't recall much of it being discussed.

Let's say the RAF can cut off it's own tail & the blades can easily smack the ground ....right ?

So I know the RAF has a stick lock to hold the stick full front. We take her out on the runway & with the stick front we start the prerotation. The "droop" comes out of the blades quickly. When they are spinning fast enough, we can bring the stick to full back.

Viola ! We got plenty of clearance !

Now if someone was stupid enough to shut down the engine & leave the stick at full back, & let the blades slow down.....What is going to happen ?


Another thought ....any gyro........we prerotate with the head level to say 150 rpm.

Now I bring the stick to full back.....Is the angle of the hub bar the same as the angle of the rotor head ??

If these are stupid questions, please try not to make a prick out of me, some might be able to learn something here !
 

Alan_Cheatham

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Now if someone was stupid enough to shut down the engine & leave the stick at full back, & let the blades slow down.....What is going to happen ?

One thing not mentioned in this discussion is the use of centrifugal teeter limiters, something found on many larger gyros to keep the rotor from chopping the tail or ground when at low rotor rpm.

.
 

CLS447

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Alan, I was going to mention those. They are an option.

If they prevent it, A very wise option. I have a set from RAF & want to adapt them to my machine. Thanks
 

Alan_Cheatham

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Another option is a stick lock that keeps the stick forward for low rpm operation on critical machines that run the risk of rotor tail chopping. Ron Herron developed one for the Littlewing, which is critical about rotor management at low rpm. Cierva and other tractor autogiros also used stick locks and kept them locked till a minimum of rotor rpm was achieved.

.
 

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bmoore2156

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One thing not mentioned in this discussion is the use of centrifugal teeter limiters, something found on many larger gyros to keep the rotor from chopping the tail or ground when at low rotor rpm.

.

The ones on my gyro are not fool proof. Say the rotor is spinning 50 rpm and slowing down and it's a windy day. The droop stops will let the rotor teeter (flap) and smack the tail if I let the stick back.
Chris, I agree with you. Nothing rotating should be able to hit anything fixed on the gyro. If you want to design it out, I think you should. In my gyro, there are just some things you cannot do, like.... Flap the blades with the stick back... Go full power under 200 rpm... Land on the nose wheel... Fly inverted.. ect. ect.
My RAF rotorhead as measured from the torque tube had 2 deg forward, 18 deg aft, and 12 deg left/right
Your build is looking good, Keep it up!
Brad
 

birdy

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Now if someone was stupid enough to shut down the engine & leave the stick at full back, & let the blades slow down.....What is going to happen ?
Chris, the blades shouldnt be able to touch anythn but the air.
Neither of mine [ wasa included] will touch anythn no matter where the stick is or if its restn on the tail wheel at 0 rrpm.
If the blades cant touch anythn at rest, they wont at speed.
Iv seen sum machines that allow the blades to smash all sorts of stationay bits without rrpm. Yes, they mite not touch anythn while spin'n up, in calm air or consistant wind.
But throw in sum gusty air and a pilot half asleep and sh1t will hit the fan, or rotor.
Specialy at low rrpm, at the start of prespin.
Blades will sail all over the place to the extreams of teeter angles in gusty air at low rpm. It only takes a too soon a backstick to max things out.

Most of the work i do in the wasa is bore run'n [Checkn me moos waters] which means alot of TOs n landing.
And im usualy pretty tight for time and cant be bothered waitn for the blades to stop every time, so i just turn the RAFs ass to the wind and leave it there, stick locked forward without the break on and blades still spin'n, no matter how strong the wind is, and theyv never touched anythn.

Let's say the RAF can cut off it's own tail & the blades can easily smack the ground ....right ?
Then hang the dichead who set that head up.

Now I bring the stick to full back.....Is the angle of the hub bar the same as the angle of the rotor head ??
Only wen the blades are at 3 n 9, sumtimes, dependn on the consistancy of airflow.
Wen they are at 12 n 6, the bar can touch the stops if they are fed too much air at too low rrpm.
The only time the hubbar is at the same angle as the torque tube is ina true power off virtical decent or prespin'n with 0 wind.
 

CLS447

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Thank you Birdy ! I agree with you 100% .

Brad, I always enjoy landing on the nosewheel & inverted flyin. Bunting over is good also !

What are the "new" angles with the SC head ? Front & back & side to side ?
 
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CLS447

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Brad , are you still there ?

Anyone else care to comment? Don't be shy !
 

CLS447

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Your probably not going to get many replies, it's like asking how many licks does it take to get to the Tootsie Roll center of a Tootsie Pop?. :D

.
Why is it anything like that ??
 

CLS447

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Is it true or possible that the harder the angle that you have ( tilted back ), The better the airflow through the blades will be & the quicker you can get them to flying speed ?

This could lead to a shorter takeoff roll & the quicker one could get off the ground.


So I was wondering what the differences in hub angles were.

Especially the ones that don't hit the tail or ground.

It would be nice to get some numbers....................Thanks
 

bones

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cant remember, didnt have log books before, but since over 3000
Is it true or possible that the harder the angle that you have ( tilted back ), The better the airflow through the blades will be & the quicker you can get them to flying speed ?

This could lead to a shorter takeoff roll & the quicker one could get off the ground.
Thanks

Only and only until the nose wheel "pops"
 
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