George Lendich wrote:
Paul, Does anyone have a posting on the internal logic of the 2.85/1
gearbox? I'm sure if I saw it
I might understand why it has opposite rotation. Thanks, Bill Jepson
Actually the output shaft on the 2.85 rotates in the same direction
as the input shaft.
BTW I was looking for some illustrations on the WWW and I ran
across this blurb :)
************************************************
Helical planetary design -Helical gears have more
tooth contact and greater face width than spur gears.
This results in higher loads, smoother tooth
engagement, quieter operation and lower backlash.
Special tooth profiles have been developed to further
optimize planetary gear performance. Since most
vibration occurs at the entry and exit points of a gear
tooth, revised profiles eliminates metal in these
areas, without sacrificing gear strength, producing a
quieter and stronger gear.
*******************************************************
Paul Lamar
Paul or anyone else for that matter !!
Buddy - did you ever find that formula for the 2.17:1(Planetary housing
drive). It's got me beat !!
George
The power is taken out of the ring gear on the 2.17.
The planet carrier is fixed.
The RPM of the pinions is proportional to the ratio of the pitch diameter
of the pinion gear to that of the sun gear.
Lets say the sun gear is two inches and the pinion is one inch.
Therefor the RPM of the pinion is twice as
high as the RPM of the the sun gear. Now the pinion gear is doing the driving
of the ring gear. The ratio of the ring gear pitch diameter to that of the pinion
gear pitch diameter now controls the RPM ratio. Since the sun gear is
two inches in diameter and the pinion gear in our example is one inch in diamter
the radius of the ring gear MUST be 3 inches or the ring gear is 6 inches
in pitch diameter. So two up by six down = 1/2 x 6/1 = 6/2 = 3/1 or 3:1
S = sun gear dia. = 2
P = pinion gear dia. = 1
R = ring gear dia. = (S/2 + P) = 6
Over all ratio = P/S X R/P = P/S X ((S/2 + P) X 2)/P
(Professor) Paul Lamar
****************************************************************
Opps mistake. Got to fix before Russell catches it :)
Since the sun gear is two inches in diameter and the pinion gear
in our example is one inch in diameter the radius of the ring gear
MUST be 2 inches or the ring gear is 4 inches in pitch diameter.
So two up by four down = 1/2 x 4/1 = 4/2 = 2/1 or 2:1
S = sun gear dia. = 2
P = pinion gear dia. = 1
R = ring gear dia. = (S/2 + P) X 2 = 4
_______________________________^^^^
Over all ratio = P/S X R/P = P/S X ((S/2 + P) X 2)/P
(Professor) Paul Lamar
Professor,
I used the teeth count to do your calculations (see above) but that's for
the 2.85, I believe. But I'm still looking for the 2.17 calculations.
The method of Ring gear(78) divided by the Sun gear (42) and then add 1 is a
little simpler than the above.
George
Yes. You used my 2.17 formula (fixed planet carrier) and put the tooth
count in for the 2.85. That won't work. 78/42 is indeed 1.857 and that
would be the ratio if you used the 2.85 in the manner of fixing the
planet carrier, putting power in the sun gear and taking power out
of the ring gear. You then added one which indeed adds up to 2.85
which is the proper ratio for fixing the ring gear, putting power
in the sun gear and taking power out of the planet carrier.
Counting the teeth is indeed the same as measuring the pitch diameter
for purposes of calculating the gear ratio.
What is not simple about this? This IS the 2.17:1 calculations.
Over all ratio = P/S X R/P = R/S for power in the sun gear, planet carrier fixed
and power out of the ring gear.
The complicated part was showing how the formula was derived. My physics professors
taught me to disassemble a problem and think it through from the bottom up.
That way you never have to memorize a bunch of formulas and you acquire
a very good understanding of how things work.
Paul Lamar
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