X-Mozilla-Keys:                                                                                 
Marc Pedings wrote:

Paul wrote:

Cyprian Troyer wrote:

  Mr Lamar,

Just a couple quick thoughts on custom pulleys. If you can't find
existing pulleys to modify, a good machinist/gearcutter shouldn't have
any trouble making up the gears if you split them down the middle and
dowelled them together in the final assembly. The key on the output shaft
would also help maintain alignment of the herrringbone sections. If you
don't like the idea of using two pieces built up for the pulley, the
herringbone pattern would no problem to EDM into the surface of a
pulley.It would take a long time to burn, especially in order to get the
needed accuracy and surface finish, but certainly not impossible. I'll
ask at work if they'd mind terribly having me work on a prototype for
you.

Thanks, C.Troyer

I think that is a good idea. I need to call Goodyear and get
an engineering catalog to see if they have 15 inch diameter
aluminum pulleys. Don't say airplanes! :-)

I have them all.  Goodyear HTD, Gates Polychain, Browning, Morse, etc.  I also
have the application software for the Gates products.  None of these
manufacturers use aluminum for off the shelf order.  Goodyear (at the time I
checked) does not custom these in aluminum.  Gates Polychain will do them in
aluminum, but at an exorbitant cost.  To do a 2.14 ratio at 255HP, it requires
the 14mm (.55") pitch Polychain 68mm (2.6") width with a driver sprocket at 28 teeth.  
The driven sprocket is 60 tooth. Center distance is 8.4 to 9.1 inches 
adjustable (8.6 fixed).  

Service life at this level is around 1000 hours for the belt.  They
will cut you aluminum sprockets on a custom special order basis.  The Driver
sprocket was $600 and the Driven was almost 1K.  If the Driver sprocket exceeds
6500 Feet Per Minute, (somewhere around 5300 RPM) and it does, therefore it
requires Dynamic (not static) balancing.  That adds a $150 cost to the DriveR
sprocket.  

Interesting info for those who wish to cantilever the sprocket off
the front bearings of ANY engine:  The compressive pull on the system at 105HP
is 1100 lbs. best I remember.  I will be glad to do a drive analysis for anyone
interested.

Marc Pedings

Thanks Marc for all the info. How does the GoodYear Eagle stand
up in comparision to the others? Narrower belt same HP?
Higher RPM possibly? 

The 1000 hour life is interesting. 
All this does not sound good for a belt PSRU for your average run of
the mill 13B powered airplane. For the Reno racer a static
analysis based on the belt breaking strength as suggested by Matt
Cosman is called for IMHO. We might also get a little more life
with Teflon coated sprockets like your average frying pan has.

Paul Lamar
 
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