13 Horsepower

12 Horsepower

After it's successful flight at Kitty Hawk, upon its return to Dayton
the Wright 'Flyer' underwent an extensive overhaul. The engine was
fitted with spark plugs and a magneto, replacing the original make &
break system. Whilst installing the magneto Orville discovered the
original timing was so retarded that the engine's output was reduced
by about half or about twelve horsepower. Timed correctly, the engine
provided more than enough power to carry a passenger.

This evening I was thumbing through a flyer of a different sort, this
one from Harbor Freight, in which they offered a 13 hp engine for
$370. The engine has a displacement of about 25 cubic inches and
claims an output of 17 ft/lbs @ 2500 rpm. The Harbor Freight engine
weighs78 lbs; the 'Flyer' engine ran about 200 lb.

With forty feet of span and more than 500 square feet of area, I've no
doubt that the Harbor Freight engine ...or even a pair of
them ...could power a replica of the Wright 'Flyer,' although I can't
imagine why anyone would want to do so. But the idea of using a
Harbor Freight engine meshes neatly with a recent thread about a
minimum flying machine.

The Wright's drove their eight-foot propellers at about 1200 rpm
through the use of a chain drive. Crossing the chain on one of the
props gave them contra-rotation.

Should a builder wish to produce a kind of power pod suitable for use
on a variety of low-cost, light-weight airframes, the thirteen
horsepower Harbor Freight engine, appears amenable to a 2:1 speed
reduction unit. Since this is the ratio between the cam and
crankshaft of all Otto Cycle engines, suitable belts and gearing is
available at your nearest automotive salvage yard.

-R.S.Hoover

On Tue, 29 Jul 2008 20:44:23 -0700 (PDT), "
wrote:


12 Horsepower

After it's successful flight at Kitty Hawk, upon its return to Dayton
the Wright 'Flyer' underwent an extensive overhaul. The engine was
fitted with spark plugs and a magneto, replacing the original make &
break system. Whilst installing the magneto Orville discovered the
original timing was so retarded that the engine's output was reduced
by about half or about twelve horsepower. Timed correctly, the engine
provided more than enough power to carry a passenger.

This evening I was thumbing through a flyer of a different sort, this
one from Harbor Freight, in which they offered a 13 hp engine for
$370. The engine has a displacement of about 25 cubic inches and
claims an output of 17 ft/lbs @ 2500 rpm. The Harbor Freight engine
weighs78 lbs; the 'Flyer' engine ran about 200 lb.

With forty feet of span and more than 500 square feet of area, I've no
doubt that the Harbor Freight engine ...or even a pair of
them ...could power a replica of the Wright 'Flyer,' although I can't
imagine why anyone would want to do so. But the idea of using a
Harbor Freight engine meshes neatly with a recent thread about a
minimum flying machine.

The Wright's drove their eight-foot propellers at about 1200 rpm
through the use of a chain drive. Crossing the chain on one of the
props gave them contra-rotation.

Should a builder wish to produce a kind of power pod suitable for use
on a variety of low-cost, light-weight airframes, the thirteen
horsepower Harbor Freight engine, appears amenable to a 2:1 speed
reduction unit. Since this is the ratio between the cam and
crankshaft of all Otto Cycle engines, suitable belts and gearing is
available at your nearest automotive salvage yard.

-R.S.Hoover

when people talk of lycosaurs and other dinosaur references to air
cooled aircraft engines they miss entirely the measure of progress
that the wright engine provides.
the wright engine and a continental O-200 both have the same
displacement. 12 hp vs 100 hp is not a bad measure of the improvements
in engine technology.
lycontisaurs ...phooey.

is the harbour freight engine a V-twin?
Stealth Pilot

On Jul 30, 6:30 am, Stealth Pilot
wrote:

is the harbour freight engine a V-twin?
-------------------------------------------------------------------------------

It appears to be a one-lunger with a recoil starter.

-R.S.Hoover

On Jul 30, 10:51*am, " wrote:
On Jul 30, 6:30 am, Stealth Pilot
wrote:

is the harbour freight engine a V-twin?
---------------------------------------------------------------------------*----

It appears to be a one-lunger with a recoil starter.

-R.S.Hoover

This is a very insightful and thought provoking topic and I enjoyed
reading it. The HF engine mentioned is a knock off of a Robin engine
and is actually a fairly well made engine. I’ve found it interesting
to see the larger HP rated Generic and B&S V twin engines turning up
in aircraft projects and the re-drives fabricated for them. They’re
less expensive then the imported engines and do a good job for their
purpose. What they lack though is the 40 to 50 + HP range. This
however has yet to stop innovative approaches and solutions to the
problem by end users, i.e. us.

OK, Bob. I'm not even an armchair engineer, so I'll ask the question.

How much weight could that HF engine get off the ground and then at what
cruise? Assuming, of course, that it could be geared suitably. And what
propeller? Eight foot diameter?

Suitable for a minimum parasol? For a Team Airbike?

Thanks,

Flash






wrote in message
...

12 Horsepower

After it's successful flight at Kitty Hawk, upon its return to Dayton
the Wright 'Flyer' underwent an extensive overhaul. The engine was
fitted with spark plugs and a magneto, replacing the original make &
break system. Whilst installing the magneto Orville discovered the
original timing was so retarded that the engine's output was reduced
by about half or about twelve horsepower. Timed correctly, the engine
provided more than enough power to carry a passenger.

This evening I was thumbing through a flyer of a different sort, this
one from Harbor Freight, in which they offered a 13 hp engine for
$370. The engine has a displacement of about 25 cubic inches and
claims an output of 17 ft/lbs @ 2500 rpm. The Harbor Freight engine
weighs78 lbs; the 'Flyer' engine ran about 200 lb.

With forty feet of span and more than 500 square feet of area, I've no
doubt that the Harbor Freight engine ...or even a pair of
them ...could power a replica of the Wright 'Flyer,' although I can't
imagine why anyone would want to do so. But the idea of using a
Harbor Freight engine meshes neatly with a recent thread about a
minimum flying machine.

The Wright's drove their eight-foot propellers at about 1200 rpm
through the use of a chain drive. Crossing the chain on one of the
props gave them contra-rotation.

Should a builder wish to produce a kind of power pod suitable for use
on a variety of low-cost, light-weight airframes, the thirteen
horsepower Harbor Freight engine, appears amenable to a 2:1 speed
reduction unit. Since this is the ratio between the cam and
crankshaft of all Otto Cycle engines, suitable belts and gearing is
available at your nearest automotive salvage yard.

-R.S.Hoover

Copperhead144 wrote:

This is a very insightful and thought provoking topic and I enjoyed
reading it. The HF engine mentioned is a knock off of a Robin engine
and is actually a fairly well made engine. I’ve found it interesting
to see the larger HP rated Generic and B&S V twin engines turning up
in aircraft projects and the re-drives fabricated for them. They’re
less expensive then the imported engines and do a good job for their
purpose. What they lack though is the 40 to 50 + HP range. This
however has yet to stop innovative approaches and solutions to the
problem by end users, i.e. us.

The one I looked at at the local HF store looks like the Honda
industrial engines of about 25 years ago. This would probably be about
right since the Chinese have been copying the hell out of small Honda
motorcycles.

Tony

On Jul 30, 11:41 am, "Flash" wrote:

How much weight could that HF engine get off the ground and then at what
cruise? Assuming, of course, that it could be geared suitably. And what
propeller? Eight foot diameter?

Suitable for a minimum parasol? For a Team Airbike?
--------------------------------------------------------

Dear Flash,

I don't know. I'm not an engineer either... I don't even play one on
TV. But the equation for flight sez the lift has to exceed the weight
and the thrust must exceed the drag.

Lift involves air foils and velocity -- for a given wing-area a
particular wing will generate x-amount of lift at a given speed (or
forward velocity). The 'Flyer' grossed-out at about 700 lbs (!!) with
Orville on-board. It had about 500 square feet of lifting surface and
its forward velocity was between 28 and 30 miles per hour.

This is when you begin to appreciate the fact 'horsepower' does not
appear in the flight equation :-)

Abbott's 'Theory of Airfoils' tells you how much lift will be produced
by a given airfoil at a certain speed and angle of attack. Manipulate
that to find out how much wing-area you'll need to generate enough
lift to overcome your weight. Not enough? then increase the size of
the wing... but keeping in mind that one form of drag is a by-product
of lift. You're liable to run out of thrust before you arrive at
sufficient wing area.

Torque can be manipulated to achieve the best match to a particular
airframe. When that happens, the velocity of the thrust-slug will be
a very close match to the cruise velocity of the airframe. This is
where your loses due to drag will be the least. The real genius of
the 'Flyer' is that the Wright's guesstimated 30mph as their flying
speed and designed their system of thrust to match. They knew the rpm
of the engine and how much torque it was producing at that speed.
They geared this down and designed a pair of propellers capable of
converting that amount of torque into thrust and achieved an
incredible 82% efficiency in converting the available torque into
thrust. (The typical light plane of today is lucky if it sees 60%).

I think a more practical approach to the problem would be to define
the airframe in terms of weight, thrust, speed and wing area. You may
then manipulate those factors to see if your engine is a suitable
match. For example, you might consider increasing the area of the
wing.. Of course, doing so will increase the weight. Your goal is to
see if you can arrive at a suitable compromise before the weight
becomes excessive. An even more successful approach is to start with
a clean sheet of paper. With the engine fully defined (or reasonably
so :-) you know about how much work it can do. That can be
translated into a wing having a particular air foil, chord and span,
from which you can determine the weight of the wing. Those factors
would be manipulated as often as requred to determine Worse Case --
which will tell you if the match WON'T work -- and the Nominal Case --
which tells you if the thing will work.. at least, on paper.

-R.S.Hoover

This is straight from Evans, a good starting place for
understanding the mathematics of flight.

Evans also developed a straight forward design spreadsheet
that brings it all together as a performance estimate.

It takes all the following and puts it in columns by airspeed
from 40 to 200 mph. That is usually in range of what people
design. But here, with only 13 hp, you would want to expand
the low speed end of the table.

Often, low and slow machines are dominated by parasitic drag.
Open structure, lots of struts and wires. Guess high and then
double it!

That has implications on performance.
Like cruise speed and stall speed at the same place on the clock?
Also very little excess power for climb.
(Lift HAS to be higher than weigh to climb

When you have some idea of the drag estimate, the performance
numbers can be estimated.

Once the airplane is completed and flying one can actually measure
all the parameters that were initially wild guesses.


The Equations

Basic descriptive equations - Equ 1..14
Drag in all it's many forms - Equ 15..19
Performance estimate - Equ 20..28

Equasions are numbered for reference.
Variable definitions at end of the page


CHAPTER 1 AERODYNAMICS
-----------------------
GENERAL
-------

(1) Q = .00256 V^2

(2) Gross Weight Estimate:

Gross Wt.(1 place) = Payload /.35

Gross Wt.(2 place) = Payload /.40

(Payload = Persons * Baggage + Fuel)


(3) Reynolds No. (RN) = 778 * c * V

(4) V Stall (Vs) = 20 * sqrt((W/S)/CLmax)

(5) Wing Area (S) = W / ( Q * CLmax)

(6) Wing Area (S) = (391 W) /(V^2 * CLmax)

(7) CL = W / (S * Q)

(8) CL = 391 * W / (S * V^2)

(9) Lift (L) = CL * S * Q

(10) Lift (L) = (S * CL * V^2) / 391

(11) Span (b) = S /C (both the same - inches or feet)

(12) Chord (C) = S/b

(13) Wing Loading = W / S

(14) Aspect Ratio (AR) = b/C or b^2/S


DRAG
----

WETTED AREA DETERMINATION (Sw )
-------------------------


(If the airplane was totally immersed in water, all surfaces would be
wetted.)

(a) Add exposed wing and tail areas and multiply by 2.06 for curved area
of top and

bottom surfaces.

(b) Divide fuselage length into a number of sections, Multiply perimeter
of each cress

section by its longitudinal width. Add rear surfaces.

(c) Sum up all surface areas = S


COEFFICIENT OF FRICTION (Cf )

-----------------------
Super clean Sailplane Cf =.003
Clean Q2, Dragonfly .005
Enclosed Basic Trainer, Mono .009
Open Biplane, Exp. Radial .014


(15) Parasite Drag (Dp) = Cf Sw q

(16) Parasite Drag (Dp) = (D/q) x q ???

(17) Coef. Induced Drag (Cdi) = CL^2 /(Pi * AR)

(18) Induced Drag (Di) = Cdi S q

(19) Total Drag (DT)= Di +Dp


Ercoupe = 4.4
Cherokee 180 = 3.9
Varieze = 2.1
Lancair 200 = 1.6
Q2 = 1.3
Dragonfly = 1.3



PERFORMANCE
-----------

(20) Prop Eff. (n) = .85
(less for shorter props, more for longer)
(at 3000 RPM n .5)!!!

Prop n = .85/(1+( DT /Q * Prop Diameter^2)

(21) Thrust HP Req. = D * V /375

(22) Max THP (Tm)= n(BHP)

(23) Cruise THP(Tcr) = .75 (.90 for VW)

(24) Climb THP (Tcl) = .90 (.95 for VW)

(25) Level Flit THP Req (TL) = .00267 * (DV/n)

(26) Excess THP (Te) = Tcl - TL

(27) Rate Climb (RC) = (Te * 33,000) /W

(28) THP req. climb = (RC * W) / 33000



WHE
V = Velocity in MPH
Persons = 170 pounds
Baggage = 4 pounds each
Fuel = 6 pounds / gallon
C = chord in inches
W = Weight in pounds (usually Gross weight)
L = Lift in pounds
D = Drag in pounds
S = surface in Sq Ft
rc = rate of climb in ft/Min
n = effeceincy
pd' = prop diameter in feet

CLmax:
Fabric = 1.2
Metal = 1.3
Composite = 1.35

*

This was origonally written on a TRS80 (with line numbers and no WHILE)
As it, it should run under Qbasic interpreter, or compiled with QB45.

Anyone who wants to play with it but doesn't have the software to run
it can email me and I'll send a compiled executible file.



FF = 0

TT = NOT FF

doRun = TT



KK$ = "LVSCQ?"



'initial values:

L = 555

W = L

A = 55

V = A * 1.4666

CL = 1.2

S = 125



CLS

PRINT "Finite Wing Theory: ---== R. Lamb 1983 ==---"; : PRINT

WHILE doRun = TT

PRINT "solve for Lift Velocity Surface Clift Quit [LVSCQ?] ";

Z$ = ""

WHILE Z$ = ""

Z$ = UCASE$(INKEY$):

IF Z$ = CHR$(13) THEN Z$ = ""

IF Z$ = CHR$(27) THEN Z$ = "Q"

IF INSTR(KK$, Z$) = 0 THEN Z$ = ""

WEND



PRINT

SELECT CASE UCASE$(Z$)

CASE "L"

PRINT " Calculate LIFT.............."

GOSUB doLift

CASE "V"

PRINT " Calculate Velocity.........."

GOSUB doVel

CASE "S"

PRINT " Calculate Wing Area........."

GOSUB doSurf

CASE "C"

PRINT " Calculate Coef. of Lift....."

GOSUB doCL

CASE "?"

'GOSUB doDump

PRINT

PRINT " Variable dump:---------------------------"

PRINT " Lift / Weight "; L; " lbs"

PRINT " Airspeed "; A; " mph = "; V; " fps"

PRINT " Coefec of Lift "; CL

PRINT " Wing Area "; S; " sq ft"

PRINT " -----------------------------------------"

CASE "Q"

doRun = FF

END SELECT



PRINT



WEND

END





doLift:

GOSUB GetSurf

GOSUB GetVel

GOSUB GetCL

L = .001188 * CL * V * V * S

PRINT " Lift = "; L

RETURN



doVel:

GOSUB GetSurf

GOSUB GetCL

GOSUB GetWgt

V = SQR(L / (.001188 * CL * S))

A = V * .681

PRINT " Velocity = ";

PRINT USING "#,###.#"; A;

PRINT " MPH = ";

PRINT USING "#,###.#"; V;

PRINT " FPS"

RETURN



doSurf:

GOSUB GetCL

GOSUB GetWgt

GOSUB GetVel

S = L / (.001188 * CL * V * V)

PRINT " Surface = "; S

RETURN



doCL:

GOSUB GetWgt

GOSUB GetVel

GOSUB GetSurf

CL = L / (.001188 * S * V * V)

PRINT " Coeff. Lift = "; CL

RETURN



GetSurf:

PRINT " Wing Area (sq ft) ["; S; "]";

INPUT ""; X

IF X 0 THEN S = X

RETURN



GetVel:

PRINT " Airspeed (mph) ["; A; "]";

INPUT ""; X

IF X 0 THEN

A = X

V = X * 1.467

END IF

RETURN



GetCL:

PRINT " Coeff. Lift (#.##) ["; CL; "]";

INPUT ""; X

IF X 0 THEN CL = X

RETURN



GetWgt:

PRINT " Gross Weight (lbs) ["; L; "}";

INPUT ""; X

IF X 0 THEN

W = X ' steady state W = L

L = X

END IF

RETURN

Copperhead144 wrote:


It appears to be a one-lunger with a recoil starter.

-R.S.Hoover

This is a very insightful and thought provoking topic and I enjoyed
reading it. The HF engine mentioned is a knock off of a Robin engine
and is actually a fairly well made engine. I’ve found it interesting
to see the larger HP rated Generic and B&S V twin engines turning up
in aircraft projects and the re-drives fabricated for them. They’re
less expensive then the imported engines and do a good job for their
purpose. What they lack though is the 40 to 50 + HP range. This
however has yet to stop innovative approaches and solutions to the
problem by end users, i.e. us.

I bought the 6.5 hp version 2 years ago for the gocart. Nary a problem,
starts usually on the first pull and runs good after a decent warming
period on half choke. Now its coupon priced under $103...