Helicóptero com rotor coaxial

[Cmte.Mampian]

Hello friends. I am studying the possibility of using a Subaru engine 130Hps about; knowing this, I have to do some calculations to scale the axle of the main rotor mast, and scale the intermediate shaft. The intermediate station transmits the power from the engine to the gearbox, which in turn transmits it to the main rotors. Based on potential whistle-blowers in an engine that will work in a regime of approximately 5000 rpms, and a rotor spinning at max 450 rpms, I need to have an exact idea of ​​the dimensions of these axles. I need help! Someone who has done something like this can help me give me some ideas?

Thank`s

[1946]

Originally Posted by Cmte.Mampian

Hello friends. I am studying the possibility of using a Subaru engine 130Hps about; knowing this, I have to do some calculations to scale the axle of the main rotor mast, and scale the intermediate shaft. The intermediate station transmits the power from the engine to the gearbox, which in turn transmits it to the main rotors. Based on potential whistle-blowers in an engine that will work in a regime of approximately 5000 rpms, and a rotor spinning at max 450 rpms, I need to have an exact idea of ​​the dimensions of these axles. I need help! Someone who has done something like this can help me give me some ideas?

Thank`s

Mantiene el estudio sobre tu proyecto, te advierto también en el ámbito de helicópteros no hay muchos secretos a excepción de un nuevo invento. Francois (Hobby CAD) posiblemente un Francés desde Australia, seria en mi opinión la persone indicada para una seria interacción sobre helicópteros. En la China, nuestra especialidad son motores Subaru de alta potencia y caja reductoras, también podríamos cooperar en tus proyectos.

Atentamente
Alberto Briceño
psruaustralia@yahoo.com
subaruair@yahoo.com

[Jon]

Here is an article from the Experimental Helo magazine, it may be helpful to you.

I may be wrong but on a new and untested design I would suggest using the largest diameter shafts that you can use because the larger shaft would be stronger. While researching for my project I found that for a given shaft weight the hollow shaft is stronger.

If I can help in any way let me know.

The article starts here. It is a lot to read but has lots of useful information.

Stu FieldsRotor Shaft Safety Factors Rotor Shaft Safety Factors
Disassembling my Safari transmission to replace failed
bearings, a groove, worn into the main rotor shaft by a rubber
seal, was discovered. Discussions ensued as to the degree of safety
hazard posed by this groove. To better evaluate the hazard of
operating a shaft in this condition the following limited analysis
has been done.

Groove in a Ti shaft,
caused by the rubber seal. .
The picture shown here is the groove in the Ti shaft caused
by the simple rubber seal. The seal had the little internal support
spring removed at the kit factory, so the seal was only rubber
when it was in contact with the Ti shaft. The time on the shaft was
170 hours.

The nominal diameter of the shaft is 1.5 inches while the
diameter at the groove site as measured by a digital caliper is

1.460 inches, meaning that the depth of the groove is 0.020 inches.
The caliper cannot measure to the bottom of the jagged
grooves. However, taking just the 0.020 and ignoring the jagged
nature for simplicity, an estimate of the stress concentration factor
caused by the groove can be made from calculations and
charts found in the Standard Handbook of Machine Design, page
28.17.
Stress on a round shaft induced by torsion
(1). Mt = (pD3*Sv)/16
Mt = the applied torque units of inch pounds
D = the diameter of the round shaft in inches
Sv = the shearing unit stress at a distance ‘r’ from the

center in psi.

For hollow shaft,
(2). Mt = p(D4- d4) Sv / (16D) or


Sv = Mt (16D) / (p
(D4-d4))

D = O.D.
d = I. D

Note: We will use this equation later for calculations on
the RotorWay Exec, the Mosquito, Wasp, Helicycle, Mini-500,
Hummingbird, and the Helismart helicopters, which all use a hollow
shaft.

Note: The statement of “Tube is stronger than a Rod” is
proven true when the math says that for the same weight and
materials, the tube is stronger in shear and bending than the solid
rod. To get the same weight in the tube, the diameter must be larger
than the rod diameter. As shown in the above calculations, the
shear strength increases exponentialy with increases in diameter.

We can compute the moment Mt by knowing the Rpm,
and the Hp from the equation:
Hp = Rpm x Torque/5252

Note: Torque has units of foot-lbs and needs to be modified
to inch-lbs for use in (1).

For the helicopter in question, the power is listed as

Hp = 160 and the rotor Rpm = 500.

Then the Torque, Mt, is:

160 x 5252/500 =1681 foot lbs = 20,168 inch lbs


4 / Experimental Helo / November 2010 www.experimentalhelo.com

 
Looking at the charts found in the “Standard Handbook of

Machine Design”, pg 28.17

For our example,

D = 1.5-inches; d = 1.46-inches; r = 0.020-inches

Then

D/d = 1.03 and r/d = 0.014
For torsion, it is seen that the stress concentration factor is
approximately 1.85
From equation (1)
Sv = (16*Mt) / p(D3)
The torsional nominal stress for a 1.5-inches diameter
shaft computes to:
Sv = (16 x 20,168) / p(1.53) = 30.4-kpsi
correcting for the stress concentration induced by the
smooth groove, yields
30.4kpsi x 1.85 = 56.3kpsi

The equation 1.4.6.5, found on page 1-14 of the MILHDBK-
5H, provides a method to compute the shear yield stress.
As a rule the shear yield is approximately 60% of the ultimate
shear strength. Using this equation and the data provided in the
MIL-HDBK-5H, table 5.4.1.0(c1), the shear yield strength is
computed as 81.7ksi.

Shigley’s, Mechanical Engineering Design, page 11,
defines the safety factor to be the ‘Ultimate stress’, divided by the
stress being experienced. However, that means for a small
increase in stress, the member will fail to be able to perform its
designed task.

For a more conservative definition, most designers use the
‘Yield stress’ instead of the ‘Ultimate stress’ and the Yield stress
is used in the table in the next column defining conditions appropriate
for various numerical safety factors.

Using the Shear Yield, divided by the stress concentration
corrected stress, we find: the safety factor to be:
81.7ksi / 56.3ksi = 1.5
Is this good or bad? The shown table was taken from:
http://www.roymech.co.uk/Useful_Tabl...ft_design.html
The purpose of the table is to indicate the environment
where the indicated Factor of Safety is appropriate.

Comparing the computed safety factor (Sf) of 1.5 to the
table of safety factors above, 1.5 is found to be in the range where
material certifications are required, proof loads are demonstrated
and the environment and actual stresses are well known with a
“high degree of certainty”. I can’t think of any experimental kit-
built helicopter where these conditions are met and where this
low a safety factor would be applicable or desirable.

Summary as derived from the above discussion:

160Hp and 0.020 smooth groove gives a Sf= 1.5

160Hp and No groove gives a Sf = 2.7

The fact has been pointed out that there are some ships flying
with these seal caused grooves and none have failed yet. One
possible explanation for this is that the 160hp engine does not
really produce 160hp into the main rotor shaft, but is something
less. In fact, estimates show a probable horsepower closer to
130hp, when the exhaust and intake systems are taken into consideration.
Further, when gear box efficiencies, fans and alternator
power absorption is taken into account, the power delivered to
the main rotor shaft is probably closer to 120hp.

www.experimentalhelo.com

Factor of Safety Application

Factor of
Safety
Application
Application
1.25 - 1.5
Material properties known in detail.
Operating conditions known in detail Loads
and resultant stresses and strains known with
a high degree of certainty. Material test certificates,
proof loading, regular inspection and
maintenance. Low weight is important to
design.
1.5 - 2
Known materials with certification under reasonably
constant environmental conditions,
subjected to loads and stresses that can be
determined using qualified design procedures.
Proof tests, regular inspection and maintenance
required.
2 - 2.5
Materials obtained for reputable suppliers to
relevant standards operated in normal environments
and subjected to loads and stresses
that can be determined using checked calculations.
2.5 - 3
For less tried materials or for brittle materials
under average conditions of environment,
load and stress.
3 - 4
For untried materials used under average conditions
of environment, load and stress.
3 - 4
Should also be used with better-known materials
that are to be used in uncertain environments
or subject to uncertain stresses.

This changes the computed smooth grooved shaft shear to
42.2ksi for a safety factor of: 1.8; the safety factor for the non-
grooved shaft at 120hp being 3.4; a highly significant difference.

It is clear the seal caused groove significantly decreases the
shear safety factor. How much more the safety factor is
reduced by the jagged nature of the groove is not known.

Currently, the kit manufacturer is offering a “Speedy
Sleeve” modification, providing a wear surface for the seal and protecting
the shaft from the seal caused groove. Of course, to help
keep the safety factor up, the “Speedy Sleeve” must be applied
before the seal causes a groove like the one pictured above.

Continued next page

November 2010 / Experimental Helo /5

[Cmte.Mampian]

Originally Posted by Jon

Here is an article from the Experimental Helo magazine, it may be helpful to you.

I may be wrong but on a new and untested design I would suggest using the largest diameter shafts that you can use because the larger shaft would be stronger. While researching for my project I found that for a given shaft weight the hollow shaft is stronger.

If I can help in any way let me know.

The article starts here. It is a lot to read but has lots of useful information.

Stu FieldsRotor Shaft Safety Factors Rotor Shaft Safety Factors
Disassembling my Safari transmission to replace failed
bearings, a groove, worn into the main rotor shaft by a rubber
seal, was discovered. Discussions ensued as to the degree of safety
hazard posed by this groove. To better evaluate the hazard of
operating a shaft in this condition the following limited analysis
has been done.

Groove in a Ti shaft,
caused by the rubber seal. .
The picture shown here is the groove in the Ti shaft caused
by the simple rubber seal. The seal had the little internal support
spring removed at the kit factory, so the seal was only rubber
when it was in contact with the Ti shaft. The time on the shaft was
170 hours.

The nominal diameter of the shaft is 1.5 inches while the
diameter at the groove site as measured by a digital caliper is

1.460 inches, meaning that the depth of the groove is 0.020 inches.
The caliper cannot measure to the bottom of the jagged
grooves. However, taking just the 0.020 and ignoring the jagged
nature for simplicity, an estimate of the stress concentration factor
caused by the groove can be made from calculations and
charts found in the Standard Handbook of Machine Design, page
28.17.
Stress on a round shaft induced by torsion
(1). Mt = (pD3*Sv)/16
Mt = the applied torque units of inch pounds
D = the diameter of the round shaft in inches
Sv = the shearing unit stress at a distance ‘r’ from the

center in psi.

For hollow shaft,
(2). Mt = p(D4- d4) Sv / (16D) or


Sv = Mt (16D) / (p
(D4-d4))

D = O.D.
d = I. D

Note: We will use this equation later for calculations on
the RotorWay Exec, the Mosquito, Wasp, Helicycle, Mini-500,
Hummingbird, and the Helismart helicopters, which all use a hollow
shaft.

Note: The statement of “Tube is stronger than a Rod” is
proven true when the math says that for the same weight and
materials, the tube is stronger in shear and bending than the solid
rod. To get the same weight in the tube, the diameter must be larger
than the rod diameter. As shown in the above calculations, the
shear strength increases exponentialy with increases in diameter.

We can compute the moment Mt by knowing the Rpm,
and the Hp from the equation:
Hp = Rpm x Torque/5252

Note: Torque has units of foot-lbs and needs to be modified
to inch-lbs for use in (1).

For the helicopter in question, the power is listed as

Hp = 160 and the rotor Rpm = 500.

Then the Torque, Mt, is:

160 x 5252/500 =1681 foot lbs = 20,168 inch lbs


4 / Experimental Helo / November 2010 www.experimentalhelo.com

 
Looking at the charts found in the “Standard Handbook of

Machine Design”, pg 28.17

For our example,

D = 1.5-inches; d = 1.46-inches; r = 0.020-inches

Then

D/d = 1.03 and r/d = 0.014
For torsion, it is seen that the stress concentration factor is
approximately 1.85
From equation (1)
Sv = (16*Mt) / p(D3)
The torsional nominal stress for a 1.5-inches diameter
shaft computes to:
Sv = (16 x 20,168) / p(1.53) = 30.4-kpsi
correcting for the stress concentration induced by the
smooth groove, yields
30.4kpsi x 1.85 = 56.3kpsi

The equation 1.4.6.5, found on page 1-14 of the MILHDBK-
5H, provides a method to compute the shear yield stress.
As a rule the shear yield is approximately 60% of the ultimate
shear strength. Using this equation and the data provided in the
MIL-HDBK-5H, table 5.4.1.0(c1), the shear yield strength is
computed as 81.7ksi.

Shigley’s, Mechanical Engineering Design, page 11,
defines the safety factor to be the ‘Ultimate stress’, divided by the
stress being experienced. However, that means for a small
increase in stress, the member will fail to be able to perform its
designed task.

For a more conservative definition, most designers use the
‘Yield stress’ instead of the ‘Ultimate stress’ and the Yield stress
is used in the table in the next column defining conditions appropriate
for various numerical safety factors.

Using the Shear Yield, divided by the stress concentration
corrected stress, we find: the safety factor to be:
81.7ksi / 56.3ksi = 1.5
Is this good or bad? The shown table was taken from:
http://www.roymech.co.uk/Useful_Tabl...ft_design.html
The purpose of the table is to indicate the environment
where the indicated Factor of Safety is appropriate.

Comparing the computed safety factor (Sf) of 1.5 to the
table of safety factors above, 1.5 is found to be in the range where
material certifications are required, proof loads are demonstrated
and the environment and actual stresses are well known with a
“high degree of certainty”. I can’t think of any experimental kit-
built helicopter where these conditions are met and where this
low a safety factor would be applicable or desirable.

Summary as derived from the above discussion:

160Hp and 0.020 smooth groove gives a Sf= 1.5

160Hp and No groove gives a Sf = 2.7

The fact has been pointed out that there are some ships flying
with these seal caused grooves and none have failed yet. One
possible explanation for this is that the 160hp engine does not
really produce 160hp into the main rotor shaft, but is something
less. In fact, estimates show a probable horsepower closer to
130hp, when the exhaust and intake systems are taken into consideration.
Further, when gear box efficiencies, fans and alternator
power absorption is taken into account, the power delivered to
the main rotor shaft is probably closer to 120hp.

www.experimentalhelo.com

Factor of Safety Application

Factor of
Safety
Application
Application
1.25 - 1.5
Material properties known in detail.
Operating conditions known in detail Loads
and resultant stresses and strains known with
a high degree of certainty. Material test certificates,
proof loading, regular inspection and
maintenance. Low weight is important to
design.
1.5 - 2
Known materials with certification under reasonably
constant environmental conditions,
subjected to loads and stresses that can be
determined using qualified design procedures.
Proof tests, regular inspection and maintenance
required.
2 - 2.5
Materials obtained for reputable suppliers to
relevant standards operated in normal environments
and subjected to loads and stresses
that can be determined using checked calculations.
2.5 - 3
For less tried materials or for brittle materials
under average conditions of environment,
load and stress.
3 - 4
For untried materials used under average conditions
of environment, load and stress.
3 - 4
Should also be used with better-known materials
that are to be used in uncertain environments
or subject to uncertain stresses.

This changes the computed smooth grooved shaft shear to
42.2ksi for a safety factor of: 1.8; the safety factor for the non-
grooved shaft at 120hp being 3.4; a highly significant difference.

It is clear the seal caused groove significantly decreases the
shear safety factor. How much more the safety factor is
reduced by the jagged nature of the groove is not known.

Currently, the kit manufacturer is offering a “Speedy
Sleeve” modification, providing a wear surface for the seal and protecting
the shaft from the seal caused groove. Of course, to help
keep the safety factor up, the “Speedy Sleeve” must be applied
before the seal causes a groove like the one pictured above.

Continued next page

November 2010 / Experimental Helo /5

Thanks Jon!
I'll read for sure.
It's a great contribution on your part in this topic.
Actually, yes I'm working on the project with a hollow shaft, and within it another smaller diameter which is also hollow. There will be two, one inside the other, turning one on each side.

[Cmte.Mampian]

Someone tell me that this is an experimental helicopter?
I can not find your referral on the Internet at any site.

Tank`s
Cmte.Mampian.

[Jon]

It looks like an experimental helicopter to me. Someone used some Mini 500 parts to make this one. I recognize the main transmission and tail rotor assembly from pictures that I have seen.

[Jean-Luc]

Well, pretty interesting...
Had the same idea but was thinking about using one of those new hybrid engines
Like the Toyota Prius.
What is the range that you have in mind?
I do speak multiple languages like English, German, Finnish, Spanish, Portuguese, French, Italian, Romanian, Kechua, Yurok, Inuit and Esperanto. Learning Russian at the moment.
Lets talk...Cmte.Mampian
I got a few drawings myself and a large amount of data too.

Bem, muito interessante ... Tive a mesma idéia, mas foi pensando em usar um desses novos motores híbridos como o Toyota Prius. Qual é a distancia que você tem em mente? Eu falo vários idiomas como Inglês, Alemão, Finlandês, Espanhol, Português, Francês, Italiano, Romeno, Kechua, Yurok, Inuit e Esperanto. Aprendendo russo no momento.
Cmte.Mampian, precisamos conversar... eu tenho alguns desenhos originais e um grande ( whats the portuguese word for amount?????) data.

[Cmte.Mampian]

Hi Jean Luc.
First excuse me for not answering your message promptly.
I knew a Jean Luc in Europe flying a Bell 47 agricultural ... do not get to be friends, but I knew him well. It was a really good guy flying. It should already be retired.
I'm away to speak so many languages​​.
I am very likely to use the engine subaru Ej25.
My project is a little slow due to some other duties that arose, but I am always here.
Let's talk instead.

As for the word amount? In Portuguese, we use the shake "quantidade".

Big hug.
Cmte.Mampian

[Jean-Luc]

Well, I've been following the Skyrunner Coaxial helicopter project pretty close.
It sounds great and pretty solid.
Noticed that your max output on that Subaru engine is around 120/ 130 hp.
Pretty good.
But again, What is the range do you have in mind for this babe?

Bem, Eu tenho seguido o projeto Coaxial helicóptero Skyrunner de perto.
Soa bom e bem sólido .
Notei que sua saída maxima nesse motor Subaru é ao redor de 120/ 130 hp.
Muito bom. Mas outra vez, qual é o alcance que você tem em mente para esta maquina?

[Cmte.Mampian]

I do not particularly like the Skyrunner in some respects. This is because I see some problems related to the limited distance between the main rotor, think for a autorrotação, this is not very effective.
All this structure and more the engine above the pilot's head ... I do not like.



Work more with the idea of ​​Yoshine ...



I like it ...

JENSEN - YouTube


I like the way it's being worked on his gearbox ... is different, compact.
With regard to my project, if you are referring to the range (distance) flight, I have not thought much about it because for me, being a long term project, a diversion, say. some technical issues, I resolved as the time comes.
But on the other hand, I'm taking it seriously, to the extent if any, may register a patent, license, and so on. This in the future. The medium / long term.

Good luck!
Big hug!

Cmte. Mampian

[Jean-Luc]

Know what you mean.
I had a talk with him and he asked me for an out of this world 50 grand for the cds 2, delivered....
Unfortunately, 2 hours endurance doesn't fit with my project...hahaha
Did learned a lot from him on the other hand.
Well, back to equations and mathematical proof.

[Cmte.Mampian]

I forgot how to put a youtube video of a post. Can anyone help me?
Thank you.

Cmte.Mampian

[Cmte.Mampian]

Descobri.
Este helicóptero foi lançado na Rússia há poucos dias.


Berkut Helicopter - YouTube

[Brent_Brown]

http://www.helihub.com/2011/08/10/co...ias-maks-show/

[Brent_Brown]

What is a ConverVAZ engine? I can't find it on line.