Horsepower quetion

[1938BF50]

Not really Taylorctaft related but, I know that someone here will have the answer.....I want to know how many HP my Ford Model A is putting out at static run-up.

My Pietenpol is turning 1960 rpm's with a Sensenich 76-42 wooden prop in front of the Model A. Does anyone have a chart showing the horsepower curve of an aircraft engine turning a 76-42 prop? I think this was a standard prop on a Luscombe/A-65 combo.

Thanx!

[Ragwing nut]

Re: Horsepower quetion

Numbers don't relate to the continental it came off of. Model A is putting out about 40-50 hp at power, but more torque than the 65 to pull the same prop. Cam profiles, compression, stroke, etc, all affect power numbers.

[Marv]

Re: Horsepower quetion

If my memory is correct a Model A engine was 40 hp in the Model A. I do not know what horsepower it would be developing with that prop. Marv

[Hank Jarrett]

Re: Horsepower quetion

You really need to get the curves for the Model A then modify the prop to let it spin at max HP RPM. Doing what you are trying will eventually tell you how much HP it is producing on that prop at that RPM, but won't tell you anything about the best the Model A can do. You will be leaving performance on the table and never see it.
Hank

[Robert Lees]

Re: Horsepower quetion

Shirley it doesn't matter what HP it produces? The Piet should only be powered by the Model A engine!

[Marv]

Re: Horsepower quetion

With the specs i found a Model A engine will produce approximately 38 HP at 1900 rpms and 100 lbs. of torque with 30* of timing. Marv

[Marv]

Re: Horsepower quetion

PIRANIO'S ANTIQUE AUTOMOTIVE

DYNO SHEET
RUN NUMBER: 1
CUSTOMER: SHOP DATE: 2/15/2006
ADDRESS: PHONE:

ENGINE: DYNO STOCK TIME: 11:00 AM

BAROMETRIC PRESSURE: 29.93 ELEVATION: 690 TEMPERATURE: 70
STATION PRESSURE: 29.1906 CORRECTION FACTOR: 1.080969
HUMIDITY: 68

ENGINE TEMPERATURE: 180 FUEL: GASOLINE, REGULAR


RPM GAUGE TORQUE HORSEPOWER CORRECTED
READING HORSEPOWER

1200 23.5 129.70 29.63 32.03
1300 23 127.01 31.44 33.98
1500 22.4 123.78 35.35 38.21
1700 20.2 111.94 36.23 39.17
2000 18.1 100.64 38.33 41.43
2200 16.4 91.50 38.33 41.43
2500 13.3 74.82 35.61 38.50
2700 11 62.44 32.10 34.70
0.00 0.00 0.00
0.00 0.00 0.00
0.00 0.00 0.00

DESCRIPTION:
STOCK ENGINE 30 DEGREES TIMING



Marv

[barnstmr]

Re: Horsepower quetion

1200 23.5 129.70 29.63 32.03
1300 23 127.01 31.44 33.98
1500 22.4 123.78 35.35 38.21
1700 20.2 111.94 36.23 39.17
2000 18.1 100.64 38.33 41.43
2200 16.4 91.50 38.33 41.43
2500 13.3 74.82 35.61 38.50
2700 11 62.44 32.10 34.70
Marv

Based on this... the Model A engine has a broad RPM range over which it produces near peak power. If you plot it out and fit a curve it looks like actual peak power might occur at approx 2100 RPM. It would be best if you pick a propeller that will give you 2100 RPM at the air speed for initial climb.

And hey... look... your prop might be close. 1960 RPM static. It's worth a test flight to see what you can turn it up to 2100 on initial climb... then check what it does in a cruise configuration. On the other end of the spectrum, you would prefer your prop to have a pitch coarse-enough to limit the engine from over-speed when you are operating at the airspeed for maximum structural limit of the airplane. (You want to be able to control the prop with throttle at that condition and not have the airflow through the prop driving the engine) On a Piet, that airpseed limit is not well defined; but it's relatively slow.

OTHER METHODS
Here's a different approach. Note that it just-so-happens that a Continental A65 recommended cruise is at 2150 RPM. So, you could pick the prop based on an A65-powered airplane with a cruise speed about the same as a Piet... say... a J3 cub. So you should have good performance from a prop common to a J3 with A65 Cont. Check the J3 TCDS.

Or, we could start into a long drawn out engineering discussion about propeller efficiency / reynolds # / etc... not as fun... and takes common sense out of the equation.

[Hank Jarrett]

Re: Horsepower quetion

The long drawn out engineering discussion is great to establish a starting point, but you already have a starting point now. Just be careful to NOT over speed the engine on a dive with the wrong pitch pitch. You will want a little flatter pitch for better climb anyway (not so flat you over speed on WOT). Nobody builds a Piet to go fast anyway! It's a balancing act now, and you can't learn to ride a bike from books.
Hank

[Ragwing nut]

Re: Horsepower quetion

A powered piets are not fast. Your prop is pretty close on the money, I have built a few Ford props over the years, usually scimitar 72-42

[1938BF50]

Re: Horsepower quetion

Ragwing,

I take offense to your "not fast" statement!

I know of at least (2) "A" powered piets without bird strikes on the trailing edges.....

Let me ask the initial question this way.....does anyone know what thrust the Continental A-65 with a 76-42 prop is producing at a given RPM?

[Ragwing nut]

Re: Horsepower quetion

Ragwing,

I take offense to your "not fast" statement!

I know of at least (2) "A" powered piets without bird strikes on the trailing edges.....

Let me ask the initial question this way.....does anyone know what thrust the Continental A-65 with a 76-42 prop is producing at a given RPM?

Let's just say they are not Luscombe speed, more J-3, and a J-3 prop works great on one. You will have to call a shop with a dyno to find out torque numbers. Thrust loading is different as airfoil design, shape, and size will great affect numbers.

I suspect if your putting a ford on it your not going for speed anyways, more the cool factor which i prefer anyways. I have some time in a O-200 steel tube piet, and it was fast, nearly 100 mph at power. very neutral airplane and fairly easy to fly.

[Forrest Barber]

Re: Horsepower quetion

We have two Piets here at the moment, plus several that stop by to visit. Frank Pavliga has "Syy Gypsy" with the 90 HP Lambert plus Allen Rudolphs old ship with the Ford. They fly regularly , I have flown Sky Gypsy with the Ford & the A-65 .
An old trick we used many moons ago with the Gyro Planes was to tie them to a tree with a scale or back to back with a rope to see which would out pull the other. This is called "static thrust" . Any body tried that one??
I will check more soon ....