Why are low-revving, high torque engines preferred?

On Nov 28, 6:47 am, "Morgans" wrote:
wrote

The Continental Tiara 6-285. Kept breaking that shaft, IIRC.
There's still a TCDS on it so there's a few out there yet.

TCDS??
--
Jim in NC

Type Certificate Data Sheet. See
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgMakeModel.nsf/0/1376F796A5B3E1D58525670E00481FC2/$FILE/E12ce.PDF

Any U.S. certified aircraft, engine or appliance has a TCDS. Look
up your airplane. Listing he
http://www.airweb.faa.gov/Regulatory...e?OpenFrameSet

Dan

When I flew the Merlin we were told in ground school the prop turned
half engine rpm. Probably because that termonology easier to remember
than 0.42 ratio.

Power was adjusted using engine rpm (and MP) so prop speed never
entered into the equation during flight.

Big John
************************************************** ****************************

On Fri, 28 Nov 2008 00:05:28 +0100, GTH
wrote:

Morgans a écrit :

Many of the old big "V" and inline engines were 2:1, and were using the
front end of a very strong camshaft as the prop drive, weren't they?

Rolls Royce and Allison V engines were (are) overhead camshafts.
The prop reduction gear was driven from the nose of the crankshaft.
According to Rolls Royce, the Merlin XX drive ratio was 0.42.

Best regards,

wrote

Type Certificate Data Sheet. See
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgMakeModel.nsf/0/1376F796A5B3E1D58525670E00481FC2/$FILE/E12ce.PDF

Any U.S. certified aircraft, engine or appliance has a TCDS. Look
up your airplane. Listing he
http://www.airweb.faa.gov/Regulatory...e?OpenFrameSet

Duh! I should have known that. Too much turkey! g
--
Jim in NC

"Dana M. Hague" wrote in message
...
On Thu, 27 Nov 2008 09:37:54 -0500, "Peter Dohm"
wrote:

IIRC, snowmobiles are/were derived from chain saws--which required an
engine
light enough for a man to carry and use as a hand held tool. That made
them
an obvious choice for another application were light weight was the most
critical factor--even at the cost of reliability and maintenance
intervals...

I've never heard that, seems unlikely... they are really very
different, except for both (along with outboard motors) being
2-strokes. All for the same reason of light weight.

-Dana
--
If you glue a piece of toast, butter side up, to your cat's back, and drop
it from a high place, which way will it land?

Today, thanks to a substantial market with plenty of discretionary money,
engines for snowmobiles and ultralights have improved drastically.
Gardening equipment also runs far more reliably today--and a portion of that
improvement may have come from improvements made first on ultralights and
snowmobiles.

But it was not always so--and I recommend that you ask a few of the old
timers why they used to refer to some ofthe ultralight areas by nicknames
such as "the killing fields".

Peter

"Peter Dohm" wrote

IIRC, snowmobiles are/were derived from chain saws--which required an
engine light enough for a man to carry and use as a hand held tool. That
made them an obvious choice for another application were light weight was
the most critical factor--even at the cost of reliability and maintenance
intervals...

Snow machines were survival, for people living WAY up north. Reliability
was life and death, or could be.

Lightness was also important, so the sled footprint could be smaller, and
not sink too deep, and still haul more.

Bombardier made snow machines (and engines) by the name of skii-doo. Only
one more step to sea-doo, and to ultralight engines.
--
Jim in NC

On Fri, 28 Nov 2008 08:30:06 -0500, Dana M. Hague
wrote:

On Thu, 27 Nov 2008 09:37:54 -0500, "Peter Dohm"
wrote:

IIRC, snowmobiles are/were derived from chain saws--which required an engine
light enough for a man to carry and use as a hand held tool. That made them
an obvious choice for another application were light weight was the most
critical factor--even at the cost of reliability and maintenance
intervals...

I've never heard that, seems unlikely... they are really very
different, except for both (along with outboard motors) being
2-strokes. All for the same reason of light weight.

-Dana
Some of the first ultralights DID run chainsaw motors - just like the
go-cart crowd. Some of the small aircooled outboard engines were also
used - and some early snowmobiles also used a converted aircooled
outboard. (horizontal twin Johnson Snow Cruiser and OMC)

"Peter Dohm" wrote in message
news |
| "Dana M. Hague" wrote in message
| ...
| On Thu, 27 Nov 2008 09:37:54 -0500, "Peter Dohm"
| wrote:
|
| IIRC, snowmobiles are/were derived from chain saws--which required an
| engine
| light enough for a man to carry and use as a hand held tool. That made
| them
| an obvious choice for another application were light weight was the most
| critical factor--even at the cost of reliability and maintenance
| intervals...
|
| I've never heard that, seems unlikely... they are really very
| different, except for both (along with outboard motors) being
| 2-strokes. All for the same reason of light weight.
|
| -Dana
| --
| If you glue a piece of toast, butter side up, to your cat's back, and
drop
| it from a high place, which way will it land?
|
| Today, thanks to a substantial market with plenty of discretionary money,
| engines for snowmobiles and ultralights have improved drastically.
| Gardening equipment also runs far more reliably today--and a portion of
that
| improvement may have come from improvements made first on ultralights and
| snowmobiles.
|
| But it was not always so--and I recommend that you ask a few of the old
| timers why they used to refer to some ofthe ultralight areas by nicknames
| such as "the killing fields".
|
| Peter
|
|

I'm an old timer, with a good bit of experience in ultralights, but I don't
recall engine reliability being all the bad in the early days, or having
much to do with the early ultralight fatalities.

On Fri, 28 Nov 2008 14:01:36 -0500, "Peter Dohm"
But it was not always so--and I recommend that you ask a few of the old
timers why they used to refer to some ofthe ultralight areas by nicknames
such as "the killing fields".

Most of the early ultralight fatalities were due to lack of training
and the occasional structural failure, not engine failure... not that
there weren't frequent engine failures, too. And even at that, many
of the engine failures were pilot related... either not knowing
anything about engines (again, lack of training) or pilots who thought
they could treat a 2-stroke just like a Continental 0-200. How many
pilots fried their Cuyuna engines because they didn't have an EGT to
keep track of the temperatures?

-Dana (who first flew an ultralight in the 1980's, and still flies a
Cuyuna powered ultralight today(yes, with EGT and CHT))


--
People in cars cause accidents. Accidents in cars cause people.

On Fri, 28 Nov 2008 14:39:46 -0500, wrote:

Some of the first ultralights DID run chainsaw motors - just like the
go-cart crowd. Some of the small aircooled outboard engines were also
used - and some early snowmobiles also used a converted aircooled
outboard. (horizontal twin Johnson Snow Cruiser and OMC)

True. The first ultralights used either a McCulloch 101 (a target
drone engine) or the Chrysler-West Bend engines of about 9HP (from a
two man chainsaw, I believe). However, the snowmobile engines (Cuyuna
and then Rotax) quickly supplanted them.

-Dana

--
People in cars cause accidents. Accidents in cars cause people.

"Dana M. Hague" wrote in message
...
| On Fri, 28 Nov 2008 14:39:46 -0500, wrote:
|
| Some of the first ultralights DID run chainsaw motors - just like the
| go-cart crowd. Some of the small aircooled outboard engines were also
| used - and some early snowmobiles also used a converted aircooled
| outboard. (horizontal twin Johnson Snow Cruiser and OMC)
|
| True. The first ultralights used either a McCulloch 101 (a target
| drone engine) or the Chrysler-West Bend engines of about 9HP (from a
| two man chainsaw, I believe). However, the snowmobile engines (Cuyuna
| and then Rotax) quickly supplanted them.
|
| -Dana

I don't recall the original use for the McCulloch engines, but I think the
West Bend was just simply an industrial engine, designed to be sold on
mowers and alike. But IIRC, probably because of it's high horsepower for the
era, snow blowers were responsible for most of it's success.