Snips... Variable

Ideal for our use would be a Lemans type variable length set up
where we would have one length for take off RPMs and another for
top speed and a third for cruise RPM for best BSFC. Not all that
hard to do as we are only talking about a four or five inch
change in length. This will become more important as the 2.85:1
and 3.12:1 gear box and the higher max RPM  RX8 engine come into

use.

I think Mazda has already found that out with the RX8 engine.
Basically the poor torque characteristics of the rotary engine
make it a better aircraft engine than a car engine.
IMHO Mazda will eventually address that issue with e
super charger to enhance the torque down low.

BTW Ed how far down your airstrip do the RPMs finally peak
if at all? What are the RPMs that you use to climb out
after you break ground?

Paul Lamar

It would be nice to try some different configuration on a dyno for
comparison.  My current sliding tube manifold was fabricated with

the

idea

of trying different manifold lengths (can vary length by 2 1/2").

Its

currently set for the long position (21") but could be shortened

to 18

1/2"

by simply opening a tube clamp and lowering the top part.  I had

envisioned

a high torque dc motor driving a screw to run the tubes in and out

with

a

two position swithc "Take-Off" and "Cruise".  Had too many other

variables

early on to play with changing its length, but now might be the

time to

do

so.

snips...

Ed

I have been thinking about it too. If you apply a point load on
telescopic tubing it tends to cock and jam. I am thinking about
a light weight integral annular hydraulic cylinder on each runner to
serves as  actuators. I'll draw something up.


Paul Lamar

Yes, the tubes can be adjusted by tapping on the plate welded to all

four

(up or down), but had to keep the fit tight between outer and inner

tubes to

stop air leaks and that does not lend itself to easily running them up

and

down.  Be interested in your  drawing.

more snips...

Ed Anderson

OK here it is. The control in it's simplest form would be a hydraulic

cylinder

on the instrument panel with a knob on the ram. Move the knob in and the
runner elongates. Move the knob out and the runner contracts.
All done with low pressure fluid piping. Mazda should make this instead of
all that Mickey Mouse three stage dynamic chamber mess. This should be

fairly

cheap to build in large quantities.

Since the runner would have to move in and out inside the plenum a gadget
in the plenum could limit runner extension travel.

To answer those that will ask: "How come the bell is 180 degrees instead
of only 90 degrees as in my other designs? The answer is: a 180 bell works
better when it is not attached to a wall. In other words in the middle of

a plenum.

If the bell is attached to the plenum wall 90 degrees is sufficient.

The trick to keeping the runner wall thickness down is the trick with
the off set O rings shown in the second jpg. Teflon encapsulated silicone
O-rings would work well hear as they would reduce the friction forces.

Paul Lamar

  Interesting arrangement on the"O" rings to seal the tubes and permit
movement.
I'll file that for future reference.

Ed

So what do you think of the hydraulic drive itself? :)

Paul Lamar
 
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