I am thinking about building a Reno Racer.
We need about 800 to 1000 HP to blow the rest of those guys into the
weeds :-)
First hurdle is coming up with a gear box.
I can't afford $35.000 for a bell final drive so I investigated the
Allison 1000 truck transmission.
Rumour had it it was 4:1 but that is not the case for a single planetary
set. P3 on the Allison is 3:1 when you hold the ring gear fixed, take
power out of the planet carrier and put power into the sun gear.
The output will rotate in the same direction as the engine.
You get the ratio by dividing the ring gear diameter by the sun gear
diameter and adding one.
Here is a picture compared to the Ford unit most people are using now
for most rotary powered air planes.
Looks good for a 1000 HP 3 rotor engine.
A lot of the stuff attached to the ring gear will be machined away.
Paul Lamar
I have decided to build our own planet carrier out of 7075T6 and add two
pinions. Six total up from four. 50% more torque capabilities.
The Allison planet carrier is too hard to machine.
The planet parts are low cost. There are a million Allison 1000 out there.
Here is what it will look. We will keep the .75 dia. planet shafts and
EDM a 1/2 inch hole in them for the prop shaft flange. Hardness and
smoothness are retained. Lower cost than making new shafts.
The back of the planet carrier is smooth for a pusher thrust bearing.
The Allison has a much better input shaft and the required splines to
the sun gear for our purposes than the Ford.
I talked to Kyle Mohan yesterday about his 3 rotor Drift engine making
800 to 950 HP
with side ports no less. It is running on gasoline. The turbo charger is
smaller than the time to climb turbo. A Turbonetics GTX 750.
He has 20 races around the world on the engine so far with out
rebuilding it.
Much thanks to my auto transmission expert Donny Caccamise that has
helped us over the years.
Paul Lamar
The prop situation is not as bad as I thought.
Here are some charts generated by a BASIC program of tip speed verses
RPM. We will see what RPM the time to climb engine achieves to see how
well the Catto 84 inch prop deals with tip speed. This also helps the
gear box as the shaft stress is reduced with a constant 1000 HP at a
higher shaft RPM than 2000. The shaft diameter is between 50 mm and 60
mm depending on what needle bearing I can buy.
I have yet to calculate the tip speed at 400 MPH AC speed.
That can be done with a modification of the BASIC program.
It will be a max of 1.3 times the radial tip speed.
If we are lucky the TTC engine will achieve 7500 RPM with the
3:1 gear box. I can hardly wait :-)
More on this soon.
Paul Lamar
Paul,
We changed the nose case on Steadfast to speed up the prop from .7 to .9
mach at the tip at race speed. It didn't add any speed! It made the
plane smoother as we were able to run a better prop combination, but as
it came out, that same prop on the slow nose case gave us the same speed.
If you want to go really fast at Reno, think three things.......
aerodynamics, aerodynamics and aerodynamics. Drag reduction is the
easiest way to go faster! The brute hp method works, but at a price, and
drag reduction has far better yields. A very low drag airframe will beat
them at much lower hp numbers. Not that I don't like HP, but I can tell
you for a fact where we found the speed in Steadfast.
Larry Child
Well that is fine but I don't have the money or time to design a new
Sport Class racer.
As I understand the Sport Class rules you need to sell x number of kits
to qualify.
I know top speed is the cube root of HP.
I was planning on buying a flying Glasair and using that. I think a
GlasAir is now going over 400 MPH.
A few aerodynamic tweaks may be possible.
I will be happy if we can just stay with them :-)
Weight is also a big factor as when you are pulling a steady 3 or 4G's
Paul Lamar
Larry, do you have my book How to Cool Your Wankel ?
If you apply the Kucheman & Webber curve on page 29 to the inside of
your cowl you can cut down on some of the opening area and in theory
reduced the cooling drag. This was done on late radial engines like the
Super Connie.
Paul Lamar
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Paul,
Don't think I have it. I have many of the old docs from NACA on cooling
the radial (and water cooled) engines. There was great research done
late in that engine era that never went into production as the jet age
took over. We used the data to redo the engine cooling on Steadfast and
gained lots of speed. The other area we gained lots of speed was getting
the airframe straight so the plane flew with no trim at speed. On sport
class airplanes there are many areas to reduce drag and I will go over
them when you are here. I have a friend who does drag reduction design
work that is very interesting and has been used on several very fast
sport planes as well as the jet class.
Larry Child.
OK Larry Thanks.
Paul Lamar
The Rotary Engine free News Letter. Powered by Linux.
If you want off the list PLEASE let me know and I will
remove you. ACRE NL web site.
http://www.rotaryeng.net
You Tube
http://tinyurl.com/beqqxas
Copyright 1998-2016 All world wide rights reserved.