Effect of prerotation on takeoff distance

Could calculate the drag on the ground at 200R rpm at 20° tilting angle ?
The static thrust of a rotor is proportional to the square of the rpm.
So, if 170 kg of thrust at 300 rpm, then at 200 rpm you will have 170 kg * (200/300)^2 = 75 kg
in accordance with what Xavier said.
With electric, no tire slipping
 
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why are you keeping this antique pre-spinner ?
It has worked well for over 2,800 pre-rotations.
It helps to teach rotor management.
It weighs 7 pounds (3.18 kilos).
I like to fly The Predator more than I like to work on her.
I fly often enough that I have plenty of other things to work on.
 
@Vance " The Predator's Denso geared automobile starter has a designed duty cycle of around eight seconds and is only 50 percent efficient " I think I would be looking for an alternative replacement unit with better outputs, I run mine for up to 25/30 seconds. The manufacturer changed the gearing within mine once I explained I was looking for 200 (ish) rrpm with a 108 tooth ring gear, at no extra cost.

8 seconds is the designed duty cycle for most automobile starters.
The Predator has 8.5 inch chord 30 foot blades.
It is geared to spin the rotor well past 100 rotor rpm.
The system simply doesn't have enough power to spin the heavy blades faster than 100 rpm in an acceptable time frame.
I am typically off in less than 500 feet and the shortest runway I fly from is over 2,000 feet long.
 
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while I’m all for the development of the reliable and fast electric pre rotate and support the efforts of anyone who is doing R&D on it, has anyone here attempted a hydraulic system?

with the Wx in Cape Town today just perfect I am going to do some experiments with take of distance ( in meters ) and various Pre rotate speeds to see if a higher pre rotate really offers much advantage on take off distance (50ft)
The Fusioncopter Nano uses hydraulic.
smiles,
Charles
 
1.58 kilos for 8000W (130 euros) , plus the 2 small gears, 2 aluminum plates and 4 small aluminium tubes = 2.5 kilos

you are speaking about researsh and devellopement cost , excuse me but it is hillarious, it took the deep uneducated man I am 10 hours to draw the cad, machine and mount it ...

what a research ...



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Your a genius .... now get it onto a factory machine with approvals .... really the arrogance of the French you and your mate need a good talking too 😳😈 The rotary wing engineer 😂


all theory ( talk) no results your tickiling my left ball now and I suggest you leave the right one alone😡

jm I have a5 axi mill in my workshop your cad drawing does not impress me ok .... mine makes me money I make bespoke parts for serious firearms for men who are very particular Drawing a sold works model and wanking lever it does not put into production!
 
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Thanks we all know this 😳 can you explain the relevance within this thread ? Look we are all over impressed with your theoretical knowledge ....

myself concerned with your seat in the Pic knowledge ....what gyroplan’s do you fly and how many hours of instruction under your belt ...sorry to ask but I’m just curious ?
 
Vance you can’t teach this prick anything ..... he and his mate know everything cos they have some maths calculations .. 😁
Good day Greg Vos, I feel your breadth and depth of experience can be an asset to the Rotary Wing Forum and I hope this will not diminish your willingness to contribute and you will take it as intended.

In my opinion part of how the Rotary Wing Forum works is people ask questions, questions get answered and sometimes the wrong answers get corrected.

I have learned a lot here through this process.

This thread is particularly interesting as it was started by someone who understands testing and he presented some interesting test results complete with quantifying the benefit and recognizing the risks.

I consider jm-urbani a friend and have found him receptive to input.

English is not his first language and sometimes I find the words he uses confusing.

He has a relatively narrow range of experience and I find it is useful to frame his posts inside that experience. Short, bumpy grass strips in aircraft of innovative design outside of most general aviation.

Just as my responses need to be framed as a flight instructor in the USA who usually teaches on a familiar eight thousand foot runway with an operating control tower and scheduled airlines.

I find when people refer to me or my friends in pejorative terms I am inclined to discount their contribution to the Rotary Wing Forum.
 
Thanks we all know this 😳 can you explain the relevance within this thread ? Look we are all over impressed with your theoretical knowledge ....

myself concerned with your seat in the Pic knowledge ....what gyroplan’s do you fly and how many hours of instruction under your belt ...sorry to ask but I’m just curious ?
When I am questioned, I answer
My sketch answered your questions, but I may have misunderstood

I have never taught flying on any flying machine.
You were probably not born when I built and flew my Bensen in 1969 without any instructor, without a pre-launcher. First hung on a long rope during the strong winds, like a kite, then pulled by a car, then finally propelled by a Panhard car engine. The design of a propeller adapted to this engine led me to think more about aerodynamics (my job was electronics technician)
What diameter? Which chord? Which pitch? Which profile? Which efficiency?

How many hours did you think about these questions?
Sorry to ask but I'm just curious.
 
Good day Greg Vos, I feel your breadth and depth of experience can be an asset to the Rotary Wing Forum and I hope this will not diminish your willingness to contribute and you will take it as intended.

In my opinion part of how the Rotary Wing Forum works is people ask questions, questions get answered and sometimes the wrong answers get corrected.

I have learned a lot here through this process.

This thread is particularly interesting as it was started by someone who understands testing and he presented some interesting test results complete with quantifying the benefit and recognizing the risks.

I consider jm-urbani a friend and have found him receptive to input.

English is not his first language and sometimes I find the words he uses confusing.

He has a relatively narrow range of experience and I find it is useful to frame his posts inside that experience. Short, bumpy grass strips in aircraft of innovative design outside of most general aviation.

Just as my responses need to be framed as a flight instructor in the USA who usually teaches on a familiar eight thousand foot runway with an operating control tower and scheduled airlines.

I find when people refer to me or my friends in pejorative terms I am inclined to discount their contribution to the Rotary Wing Forum.
Vance your responses in general are well thought out and never matter of fact, your a respected flight instructor who operates a very powerful Machine, if I were to research your posts and ideas as you put them out in a constructive way, and yet leave the door open for practical debate.
some clearly academic individuals are not as polite and are very matter of fact, have few flight hours or type ratings to base their sometime biased opinions with?
this thread was about - does a higher pre rotate speed aid performance take off?
finaly it was agreed after some banter that it does not, this happened while I was out today doing some practical tests, myself only reading this response on arrival at home,

my tests today are in line with your comments and with the opening posts yet I have been subjected to countless ( yet very well produced complex theories)
I am always open to improvements and new ideas just because I don’t agree does not mean I don’t appreciate its merit


for the record today pre rotate and take off same plane same MAUW Zero relevant wind QNH 400 Ft OAT 24

150 Rrpm
170 Rrpm
200 Rrpm
260 Rrpm
my distance to 50ft in runway length was almost identical

I am by no means a scientist but these were my actual flight tests done with one gyro all within 2 hours, while I accept that some clever people can add formulas and Complex models and they can discredit actual exp with calculations these were my findings and I am satisfied that a higher pre rote adds little advantage and will only serve to wear the mechanism.

in the above if we are going to be critical the only variable is the lowering weight in fuel spend for the flights
 
Thank you for all you contribute to the Rotary Wing Forum Jean Claude.

I love it when my testing is validated by your calculations and try to learn when there is a divergence.
 
When I am questioned, I answer
My sketch answered your questions, but I may have misunderstood

I have never taught flying on any flying machine.
You were probably not born when I built and flew my Bensen in 1969 without any instructor, without a pre-launcher. First hung on a long rope during the strong winds, like a kite, then pulled by a car, then finally propelled by a Panhard car engine. The design of a propeller adapted to this engine led me to think more about aerodynamics (my job was electronics technician)
What diameter? Which chord? Which pitch? Which profile? Which efficiency?

How many hours did you think about these questions?
Sorry to ask but I'm just curious.
Thank you for your compliment about when I was born 😁yes that is a very recent profile pic and yes I was already racing motorcycles in 1969 ...so the wine women and whiskey have done me well...😁 I spent 11 years as an engineer with Siemens so we both have a modest electronic background 😁

I with respect don’t question your calcs and models I simply question them in respect to practicality.

my good wife of 33 years is an actuary ( being an accountant was to exciting for her) she too has complex models and spreadsheets and the like, yet unable to use a screw driver with any practicality ....sometime we need to look beyond models and theory and we need to test them, I thank you for your efforts and just by the way I’m jealous i have not built a single seat gyro, our regulations are very restrictive in SA.
 
You don't have to fly to understand the theory of flight. A monkey can learn to fly but will have difficulty calculating the take off roll of a gyro.
Airline pilots do it often 😉😂😂😂🤣

understanding a theory doesn’t not make you a competent pilot😳 Practice and experience does .....
 
Thank you for all you contribute to the Rotary Wing Forum Jean Claude.

I love it when my testing is validated by your calculations and try to learn when there is a divergence.
Vance I cannot open pages on your web site? A few days now are the links working?
 
Vance your responses in general are well thought out and never matter of fact, your a respected flight instructor who operates a very powerful Machine, if I were to research your posts and ideas as you put them out in a constructive way, and yet leave the door open for practical debate.
some clearly academic individuals are not as polite and are very matter of fact, have few flight hours or type ratings to base their sometime biased opinions with?
this thread was about - does a higher pre rotate speed aid performance take off?
finaly it was agreed after some banter that it does not, this happened while I was out today doing some practical tests, myself only reading this response on arrival at home,

my tests today are in line with your comments and with the opening posts yet I have been subjected to countless ( yet very well produced complex theories)
I am always open to improvements and new ideas just because I don’t agree does not mean I don’t appreciate its merit


for the record today pre rotate and take off same plane same MAUW Zero relevant wind QNH 400 Ft OAT 24

150 Rrpm
170 Rrpm
200 Rrpm
260 Rrpm
my distance to 50ft in runway length was almost identical

I am by no means a scientist but these were my actual flight tests done with one gyro all within 2 hours, while I accept that some clever people can add formulas and Complex models and they can discredit actual exp with calculations these were my findings and I am satisfied that a higher pre rote adds little advantage and will only serve to wear the mechanism.

in the above if we are going to be critical the only variable is the lowering weight in fuel spend for the flights

Thank you Greg Vos, I find value in your willingness and ability to do such accurate testing.

Chris in his original post postulated that gaining a little airspeed before bringing the cyclic full back had some value at the increased risk of flapping the blades and did the testing to validate that hypothesis. Chris is both a PHD and an experienced test pilot from Austria flying an Arrow Copter.

I suspect the title of the thread and Chris’s hypothesis and may have made the communication more challenging.

Trying to discuss a technical subject with English as a second language also muddies the waters.

I have not had success with humor on the Rotary Wing Forum for the same reason. What is a joke in English often translates to an insult in another language or culture.

I marvel at your skill with the English language and am marginally familiar with the various languages spoken in South Africa having visited Cape Town and wandered around as part of a group many years ago.
 
Vance I cannot open pages on your web site? A few days now are the links working?
I will have my support representative have a look at is. It would help to have detail about which links won't open for you and what device you are using.
 
Vance I cannot open pages on your web site? A few days now are the links working?
I had the head of support at Santa Maria Software, Ralph, try every link and they worked for him.
He felt it might be a browser issue or a security issue.
If he knew what you were using and what pages didn't work it would help him narrow it down.
 
I had the head of support at Santa Maria Software, Ralph, try every link and they worked for him.
He felt it might be a browser issue or a security issue.
If he knew what you were using and what pages didn't work it would help him narrow it down.

will send pm not to thread drift
 
I with respect don’t question your calcs and models I simply question them in respect to practicality.
I always compare my "academic" calculations with real measurements, and not with vague subjective impressions that mislead many pilots (including instructors).
My sources of practical measurements are therefore often the very precise reports of the NACA, or other serious study organizations (they are rare), or my own test aircrafts (it requires much more than a few hours of work).
I appreciate that you did the distance test based on rpm (weren't you convinced?).
You may now test the static rotor pull as suggested ? (stick back as soon as you land without wind).
 
I always compare my "academic" calculations with real measurements, and not with vague subjective impressions that mislead many pilots (including instructors).
My sources of practical measurements are therefore often the very precise reports of the NACA, or other serious study organizations (they are rare), or my own test aircrafts (it requires much more than a few hours of work).
I appreciate that you did the distance test based on rpm (weren't you convinced?).
You may now test the static rotor pull as suggested ? (stick back as soon as you land without wind).
I’m not sure what you wanted to test on landing? I always pull stick back on landing to avoid forward roll? I use it as a break and don’t use the wheel brakes.

it must be understood that I land very diffrent on my own when I fly as Pic and not teaching ...I approach LZ behind the power curve with nose high and land with almost no forward roll, this is not for guys with low hours and I don’t recommend it to guys with low gyro hours for obvious reasons ...so my technique may not add bennafit?

I will of course gladly test any theory and report openly my findings without fear of being incorrect if this is the case
are you suggesting standard approach and on the touch down while still seeing 65 mph indicated before nose wheel down pull stick full aft ? And monitor Rrpm ?
 
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