X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from ispmxmta06-srv.windstream.net ([166.102.165.167] verified) by logan.com (CommuniGate Pro SMTP 5.1.10) with ESMTP id 2204484 for flyrotary@lancaironline.net; Sat, 28 Jul 2007 11:42:52 -0400 Received-SPF: pass receiver=logan.com; client-ip=166.102.165.167; envelope-from=montyr2157@alltel.net Received: from ispmxaamta08-gx.windstream.net ([71.29.244.202]) by ispmxmta06-srv.windstream.net with ESMTP id <20070728154211.TEPL29331.ispmxmta06-srv.windstream.net@ispmxaamta08-gx.windstream.net> for ; Sat, 28 Jul 2007 10:42:11 -0500 Received: from Thorstwin ([71.29.244.202]) by ispmxaamta08-gx.windstream.net with SMTP id <20070728154211.BCDE7089.ispmxaamta08-gx.windstream.net@Thorstwin> for ; Sat, 28 Jul 2007 10:42:11 -0500 Message-ID: <001601c7d12d$e2a97b80$6501a8c0@Thorstwin> From: "M Roberts" To: "Rotary motors in aircraft" Subject: Gear redrives.com Date: Sat, 28 Jul 2007 10:42:19 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0013_01C7D103.F933B110" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 This is a multi-part message in MIME format. ------=_NextPart_000_0013_01C7D103.F933B110 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable and planetary gears are simply not designed to operate at high RPM's and under such a great load as they are under while in use in an airplane. Planetary gears do well in situations that only require high = RPM for a very brief period of time, but are not designed to operate under consistent and continuous use at high RPMs. This is a recipe for = disaster in our opinion. Spur gears, as we use in our PSRU, on the other hand, are designed to safely operate at a high RPMs and under continuously use. We chose to use what we know to be the most dependable and reliable = technology for this application because our objective was to do what makes sense in terms of safety, reliability, and ease of maintenance. " I don't know who the hell Bud is, but he doesn't know jack about gear = design. I don't think I would want to fly behind hardware designed by = someone who is obviously ignorant of basic machine design. I suggest Bud and anybody considering flying behind his products peruse = the following excerpt from this document: http://www.sil.si.edu/SmithsonianContributions/AnnalsofFlight/pdf_lo/SAOF= -0001.4.pdf Reduction Gears The Wrights, with their chain drive, were evidently aware that the = optimum speed for engines is not usually that for propellers. Even before the = Wrights, most experimental airplanes (Stringfellow, Maxim, Langley, and others) had belt- or gear-driven propellers, although the drive ratio for steam engines was usually up rather than down. Direct propeller drive, with the propeller mounted on the crankshaft, is attractive for its simplicity and reliability, and was used by most = of the early fliers after The Wright's and up to the start of World War I. An exception was the early Renault air-cooled V-8 (fig. 17, p. 20), the = propeller shaft of which was an extension of the camshaft (or vice-versa) and ran = at half crankshaft speed-a ratio which has been widely used since. Other geared engines which appeared for use in World War I included the RAF (a copy of the Renault), the 8-cylinder-in-line Mercedes, and = the 220-hp Hispano-Suiza. These were soon followed by the Rolls-Royce Eagle, with planetary gears. (emphasis mine) The need for propeller gearing results from the fact that the propeller speed for optimum propeller efficiency is usually lower than the speed = at which the engine gives its best performance. Without gearing, the speed for the engine-propeller combination is chosen as a compromise-too high for best propeller efficiency and too low for maximum engine power. As improved engine design called for higher engine speeds, this compromise became more unsatisfactory. By 1920 most large European engines were geared. In the United States, however, the general use of reduction = gears came much later. For that matter, in 1924 gearing was actually = eliminated from the Curtiss D-12 engine in order to save 25 pounds of weight! = Nevertheless, by 1930 it was evident that large engines should be geared to allow of optimum performance. Pratt & Whitney used an internal gear in 1931, and both Wright Aeronautical and Pratt & Whitney adopted the Farman planetary gear for use in the DC-3 in 1933 (fig. 69). From that time on, 78 Figure 69.-Bevel planetary reduction gear system as used on Farman engines, after World War I. This type was also used by some American engine builders under license from Farman. Below, Spur-type planetary reduction gear system which superseded the bevel type. >///////;//M////w/=BB/}, propeller reduction gears became an integral part of all large airplane = engines, spur type planetary gears being standard for most radials and plain 2-element spur gears for V-type engines (fig. 70). The plain spur gears used by the Rolls-Royce Merlin of 1945 carried 2,200 takeoff horsepower satisfactorily on a face 2-in. wide, a remarkable achievement in gear = design. Now obviously since planetary drives have been with us since the dawn of = the airplane engine they must be capable of working wouldn't you think? = The PT-6 has a planetary reduction drive for the propeller, as do most = all geared turbofan engines. Spur gears have offset loading which = requires both a more substantial gear and housing for the same load as a = planetary. Any competent designer would choose the planetary over a spur = gear, unless there was some reason not to (like an offset shaft for a V = type engine) Caveat Emptor. Monty ------=_NextPart_000_0013_01C7D103.F933B110 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
and = planetary gears=20 are simply not designed to operate at high
RPM's and under such a = great load=20 as they are under while in use in an
airplane. Planetary gears do = well in=20 situations that only require high RPM
for a very brief period of = time, but=20 are not designed to operate under
consistent and continuous use at = high RPMs.=20 This is a recipe for disaster in
our opinion. Spur gears, as we use = in our=20 PSRU, on the other hand, are
designed to safely operate at a high = RPMs and=20 under continuously use. We
chose to use what we know to be the most=20 dependable and reliable technology
for this application because our = objective=20 was to do what makes sense in
terms of safety, reliability, and ease = of=20 maintenance. "
 
 
I don't know who the hell Bud is, but = he doesn't=20 know jack about gear design. I don't think I would want to fly behind = hardware=20 designed by someone who is obviously ignorant of basic machine=20 design.
 
I suggest Bud and anybody considering = flying behind=20 his products peruse the following excerpt from this = document:
 

http://www.sil.si.edu/SmithsonianContributions/Annal= sofFlight/pdf_lo/SAOF-0001.4.pdf

 

Reduction Gears

The Wrights, = with their chain=20 drive, were evidently aware that the optimum

speed for = engines is not=20 usually that for propellers. Even before the Wrights,

most = experimental airplanes=20 (Stringfellow, Maxim, Langley, and others)

had belt- or = gear-driven=20 propellers, although the drive ratio for steam

engines was = usually up rather=20 than down.

Direct propeller = drive, with=20 the propeller mounted on the crankshaft,

is attractive = for its=20 simplicity and reliability, and was used by most of the

early fliers = after The=20 Wright's and up to the start of World War I. An

exception was = the early=20 Renault air-cooled V-8 (fig. 17, p. 20), the propeller

shaft of which = was an=20 extension of the camshaft (or vice-versa) and ran at

half crankshaft = speed=97a ratio=20 which has been widely used since.

Other geared = engines which=20 appeared for use in World War I included

the RAF (a copy = of the=20 Renault), the 8-cylinder-in-line Mercedes, and the

220-hp = Hispano-Suiza. These=20 were soon followed by the Rolls-Royce Eagle,

with planetary gears. (emphasis=20 mine)

The need for = propeller gearing=20 results from the fact that the propeller

speed for = optimum propeller=20 efficiency is usually lower than the speed at

which the engine = gives its=20 best performance. Without gearing, the speed

for the = engine-propeller=20 combination is chosen as a compromise=97too high

for best = propeller efficiency=20 and too low for maximum engine power. As

improved engine = design called=20 for higher engine speeds, this compromise

became more = unsatisfactory. By=20 1920 most large European engines were

geared. In the = United States,=20 however, the general use of reduction gears

came much later. = For that=20 matter, in 1924 gearing was actually eliminated

from the Curtiss = D-12 engine=20 in order to save 25 pounds of weight! Nevertheless,

by 1930 it was = evident that=20 large engines should be geared to allow

of optimum = performance. Pratt=20 & Whitney used an internal gear in 1931,

and both Wright = Aeronautical=20 and Pratt & Whitney adopted the Farman

planetary gear for use in the = DC-3 in 1933=20 (fig. 69). From that time on,

78

Figure 69.=97Bevel=20 planetary

reduction = gear=20 system as used

on Farman engines, after World

War I. This type was also used

by some American engine

builders under license from

Farman. Below, Spur-type

planetary = reduction gear=20 system

which superseded the

bevel type.

>///////;//M////w/=BB/},

propeller reduction gears became an integral part of all = large=20 airplane engines,

spur type planetary gears = being=20 standard for most radials and plain

2-element spur gears for V-type engines (fig. 70). The = plain spur=20 gears

used by the Rolls-Royce Merlin of 1945 carried 2,200 = takeoff=20 horsepower

satisfactorily on a face 2-in. wide, a remarkable = achievement in=20 gear design.

 

 

Now obviously since = planetary drives have=20 been with us since the dawn of the airplane engine they must be capable = of=20 working wouldn't you think? The PT-6 has a planetary reduction drive for = the=20 propeller, as do most all geared turbofan engines. Spur gears have = offset=20 loading which requires both a more substantial gear and housing for the = same=20 load as a planetary. Any competent designer would choose the planetary = over a=20 spur gear, unless there was some reason not to (like an offset shaft for = a V=20 type engine)

 

Caveat Emptor.

 

Monty

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