Paul,

Attached is a copy of the main parts of the drive I told you about.
Obviously, I would change it to accommodate typical parts from Ford C6.

The

original called for Corvair parts, which are still available, but the C6
parts would be much stronger.  I don't know if you can see it from the
portion of the drawing sent, but it uses a captured ring gear which

would

provide the output to turn in the same direction as the input shaft.
However, documentation with the plans state that is turns in the

opposite

direction.  The shaft is 1.33" at the thickest portion. (again from a
Corvair transmission)  The main portion shown, referred to as the

nosecone,

is 6.5625" long with the rear portion of that part at 5.75".  The

thinnest

wall is .3125" and is made from 2024-T3.  I might consider using FORTAL,
which exceeds 7075.  Using the Ford parts, the diameter
of the nosecone would probably have to be larger to accommodate the

larger

shaft and bearings, etc.  I welcome your critque.  Thanks.

Dave Kuc

Tracy Crook wrote:

I must confess that my opinion of Gyro Dynamics was formed on the basis of a
single phone call 7 years ago when I was searching for a redrive for my
13B/RV-4.  I also make gear drives so you may consider my remarks as biased
if you like.  My comments on the drive itself are meant mainly for fun.

First, I think GD is a paper company who probably never produced anything.
I asked them if they made a drive appropriate for my engine and they said of
course they did.  The price and delivery schedule ($8500.00 and 6 - 8
months) they quoted indicated to me that they had nothing to deliver but
would be happy to take my money to develop something.  I declined the
opportunity to find out if they would actually deliver.

The drawing of the drive is chock full of clues that it is a "paper design"
only.  I'll point out a few and invite others to point out more.  As already
noted, the prop hub conforms to no standard that I know of so the "artist"
probably just picked dimensions out of the air (or somewhere less sanitary).
The fine taper on the shaft would be quite adequate for transmitting the
power so the keyway at the hub does nothing but create an opportunity for
stress concentrations to cause failure.  Since they are selling plans,
presumably this was meant to be something that amateurs could make
themselves.  This design in not a particularly easy one to machine and
requires a fairly high degree of precision to be successful.   And that
front oil seal and bearing retainer!  Anyone care to calculate how much
thrust those 3/8" bolts would take?  Talk about overkill.

This looks like a mechanical drawing class exercise, not a practical gear
drive design.  Has anyone out there actually *seen* a Gyro Dynamics gear
drive?

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

 
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