Howard Wilkinson wrote:

Paul:
    I can accept that 4130 forged cranks are used in many aircraft engines
and that the journals are nitrided.... a common practice in diesel engines
as well.  1050 may well be used in some transmission shafts.... This is
hardly mild steel..... 1050 (composition listed below) is a common spring
steel stock and is often tempered to 118000+ lbs tensile strength....  I
quote tensile only because it is the most commonly quoted strength
property.... I can provide other properties to anybody who requires this
information.  This is an extremely tough material and not brittle if
tempered properly.  In any case I would advocate using a special load
bearing hub design rather than relying on the transmission shaft to carry
the total load.

Yes I agree with this but it is likely to be very heavy.
It is better to up the shaft size as per common practice in
aircraft engines and other PSRU's. You can bore a big hole in
them without affecting the strength (or stiffness :-)) too much.

    I don't have a Mazda transmission readily available.... I've got one
from a '74 Mazda rotary pickup in the junkpile somewhere, but I'm not going
to dig it out to get exact measurements.  In lieu of a Mazda transmission I
measured second gear in a Toyota pickup transmission (also used in Toyota
cars), and in a Datsun pickup transmission (also used in Datsun cars) which
I just happened to have laying in pieces.  This is a fair comparison as most
all these type of Jap transmissions are very similar internally.
    For those who are unfamiliar with transmission design, there is a short
input shaft with a gear which drives the countershaft.  The output shaft has
stub which fits into the end of the input shaft and uses a set of roller
bearings (free) to join them.  The countershaft has a cluster of gears
attached one of which drives the output shaft in all gears except fourth
which is direct in virtually all automotive transmissions (except 3 speeds).
On the Datusn transmission the input to countershaft drive was a 21/2" gear
(input shaft)driving a 31/2" gear (countershaft).  The countershaft second
gear was also a 21/2" gear driving in turn another 31/2" gear on the output
shaft... these gears were 3/4" wide.  The Toyota transmission was virtually
the same thing except that the gears were each 1/8" larger, and width was
11/16.
******  These measurements are rough quick measurements made a few minutes
ago with an el-cheapo caliper *****  It's 5 degrees F out there.

Note:  Shaft material is absolutely not mild steel.... they are quite hard
but can be marked with a sharp file.  They appear to be surface hardened
where the bearings run..... the I scratched in an unhardened area.

    I conceed that 4130 may well be used in aircraft crankshafts..... and
that the journals may well be nitrided......

1050 composition:
Component Wt. %
C 0.48 - 0.55
Fe 99
Mn 0.075
P Max 0.04
S Max 0.05

                                                                H.W.

Good work Howard. The four pinions in the C6 are about 1.3 inches in diameter
and 7/8th of an inch wide. The sun gear as mentioned is two inches in 
diameter. The ring gear is 4.5inches in diameter. Do you want to do 
the calculations or should I?

Stating the line length in the C6 as being four times the Mazda was a 
crude simplfication I made because I did not know the Mazda gear dimensions.  
I am very sure however the Ford C6 is a lot stronger than the RX7 gear box.

Any idea what Tracy is talking about? :-)

Paul Lamar
 
The Aircraft Rotary Engine Newsletter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org