Jesse Hilton wrote:
My email bounced to that New Zealand place. Does
anybody know where I can get or have made aluminum
housings to replace the cast iron housings between
rotors? I am worried about the weight.
Racing Beat in Anaheim CAlifornia sells aluminum end housings.
http://www.racingbeat.com/
Has anybody made an Allison truck auto transmission
psru?
Not yet to my knowledge. You are on the cutting edge here.
I was under the impression that 600hp from a 20b was
not unreasonable. I may be mistaken. What I really
want is 400hp at 35kft. I like the idea of increasing
your specific fuel consumption with a turbo compound.
Cause what is the use of a 350 mph airplane when you
have to stop for gas every hour or so.
I saw a few pics on bridge porting. What are the draw
backs of porting a rotary engine?
Very few. Street porting and a turbo are all you may need.
For 35,000 feet you may need two sequential turbos but not the
stock ones the 20B is usually equipped with. They are too small.
You will need two larger turbos and large intercoolers.
I'm building my Cozy out of carbon. I'm an aerospace
engineer with an A&P and I plan on having some
structural engineer friends of mine help me with the
airframe improvements to handle the increase in hp.
Your project sounds very interesting. I am looking forward to pictures
of your progress. Figure on about 550 pounds firewall forward.
Even with all aluminum end housings. The cooling system, PSRU
and turbos add up weight wise. The bare engine weight with aluminum
end housings should be close to 215 pounds. The 20B with iron end
housings is about 260 pounds.
BTW If you can find one a Bell 47 final rotor mast gear drive is
good for about 1000 HP and has been used successfully with a turbo two
rotor.
It makes a fine light weight PSRU around 45 pounds.
Paul Lamar
600hp ARE probably no problem for a 20b based engine, it just hasn't been
done yet on any airplane, go for it!
The Bell47 trans gears should be plentyful out there, at least run-out ones.
Overhaul is fairly expensive, but a run-out one would be a good template for
a selfmade one. You might be able to use some parts (planetary carrier,
housing parts) and just replace the worn parts with automotive ones.
There is a 600-series and a 900-series trans. The 900 is the stronger one,
but also WAY more expensive.
As far as I remember these trans have 2 planetary sets in a row (stacked one
on top of the other as these transmissions are vertical in the helicopter)
there is the same series for turbine powered B47's (Soloy conversions with
Allison 250 turbines. The 600 is only limited by trans-torque limits which
is about 67% of what the 250 could give. At one occasion, while ag-spraying
with one of thouse, I got myself into a bad situation: Question was, to keep
the torque within limits and touch hard or to pull power and risk the trans!
I pulled - to about 98% for about 2 seconds. The trans never started to make
any metal within the next 120 hrs, so I guess even the 600 is fairly tough.
The piston powered 600 B47's had mostly the 435 Lycomings with around 260
hp. The 900's used mainly the 540 Lycomings. TBO for the 600 was 1200 hrs.
As the Lycomings normally run around 2900 to 3100 rpm (green arc), the rotor
around 350, ...I think.
If I remember right the Soloys used the upper two planetaries from the
piston version, but had a nother reduction below, as the Allison would come
in with 6000 rpm (or was it 6600?).
In Australia you should be able to grab a few old trans as most B47's get
replaced by Robinsons.
For high altitude cooling issues you might want to contact Bruce Bohannon
from Exxon-Tiger fame.
He and his team had to work out a LOT of trouble in that respect! He is
pushing 50000 ft - Pistonpowered, turbo charged, intercooled. Thin air up
there!!
Thomas J. :))
500 HP from the core engine Thomas, not 600 HP. The exhaust turbine
adds the other 100 HP.
What matters in a gear box mostly is the torque capability.
This Bell gear box was designed as a final drive. I am guessing here but lets say
the helicopter rotor RPM is 200 and the engine HP is 260. That means the rotor torque
is:
HP = (Torque X RPM) /5252
We need to solve for Torque.
HP X 5252 / RPM = Torque
260 x 5252 / 200 = 6,800 foot pounds. I know nothing about helicopters
so 200 rotor RPM looks very low to me. You can fill me in on this point
and I can rerun the numbers. For example at 400 rotor RPM the rotor
torque would be half that or 3,400 foot pounds.
The point is this gear box will handle way more torque than a three rotor
could possibly put out. A three rotor NA would put out only about
240 foot pounds given the same level of tune as an RX8 engine.
Double the 3 rotor HP by a turbo at the same RPM and max torque would also double
or about 500 foot pounds. Still very far away from the obvious capabilities of
this gear box. That is why the Bell engineers told Dave Garber given
7000 RPM input this gear box would handle 1000 HP. BTW There is a heat
issue with high HP gear boxes so they must be supplied with cool oil.
In my experience over the last six years running this newsletter we have yet
to approach the limitations of the rotary. I have been nagging people to go
up on the gear ratio from the common 2.17:1 and increase the RPM to extract
more HP from the rotary. Ken Welter has been running his heavy Coot rotary engine
with a 3:1 gear reduction and nitrous oxide for years. Tracy Crook is just
now beginning to enjoy the fruits of his new 2.85:1 gear box.
All of the problems we have had so far has been with after market,
non Mazda oil coolers, engine swallowing metal parts, broken tension bolts or
hoses coming off. None of this has anything to do with the core engine. IMHO we
have not yet come even close to the limits of the Mazda rotary engine
in aircraft use. We do however need to focus on the reliability of the
accessories and plumbing.
There is a move afoot to adapt some of the same systems we have been
using for six years to aircraft engines such as electronic ignition and
electronic fuel injection. In addition some liquid cooled aircraft piston engines
have been tried. In other words the world of the rotary and the world
of the aircraft piston engine are slowly converging in this regard. Obviously
the rotary will eventually win as the rotary core engine is far more robust,
far simpler and will outlast a piston engine by a wide margin.
Paul Lamar
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