Paul,
I'm still looking into the possibility of a vertical installation for a
helicopter. I would be absolutely elegant if it could be made to work.
What would you think of installing three teflon buttons, one inch diameter,
or larger, near the apex inside the rotor edge seals on what would be the
lower side of the rotors. Would there be enough oil between the rotor and
the side plate that the buttons would ride on an oil film? Where are the
thrust bearings on the crankshaft?
Steve Brazil
Hi Steve,
Some thoughts on a helicopter application.
1. Most automotive design engines have little or no thrust bearings.
Rotational power is transferred to a transmission and that is where
the thrust is usually reacted against. The engine/tranny "joint" is
usually even splined to avoid putting thrust loads on the engine
bearings. You need to accomodate thrust absorption in your helicopter
transmission design.
2. In a vertical orientation you also need to consider oil return.
In a 13b slightly less than a quart of oil "disappears" in a running
engine. Some is in the oil pump, some in the pressure lines feeding
various bearing areas, some fills the oil filter, and a lot is in
the rotors cooling them. Most of these places "gravity drain" back
to the oil pan after shutdown. Only a thorough study of Mr
Yamamoto's book will provide insight to the drainage pathways.
3. Oil return and thrust handling are just some of the problems
you'll encounter. You may work for a long time to resolve either
problem adequately. Time resolving problems is time not flying,
so I would suggest you make as few problems for yourself as possible.
If you keep the engine orientation horizontal many of your oiling
and percieved rotor wear problems go away. Find the "lower unit"
for a 200 HP outboard motor and your thrust problems go away.
The "lower unit" will turn the power 90 degrees and provide a gear
reduction as well. Another problem gone. Your "engineering" effort
will consist of developing an adapter plate and reworking the
outboard's drive shaft to provide connection to the e-shaft.
(Probably, shortening and cutting a spline on the "lower unit's"
drive shaft, and fabricating a floating, internally splined collar
with splines that mate with the e-shaft on one end and the drive
shaft on the other.)
4. Keep in mind, this is the world of "experimental" aviation, and
many "experimentors" would rather tinker than fly, so you need to
address your specific goals, also. Dave M
Hi Paul and Steve,
I am currently working on a project to use the 13B on a Helicopter as well
and would like to throw in a few
of my project ideas which you might find useful.
1. Engine Mounting: The engine will run in a normal Horizontal position
and mounted in tandem on two
cross members of the airframe
2. Drive Mechanism: Will be driven by a Mechanical Clutch same as in a
manual transmission engine (to
have the ability to disengage the engine for running and fine-tuning on
the ground without spinning the
Main Rotors and also dampen the torsional vibrations from the engine).
I also incorporated a Sprag Clutch mechanism at the Final Drive end to
ensure Autorotational landing (A safety requirement for Helis so you
dont drop out of the sky peradventure the engine quits in operation).
3. Transmission: Here, I am using just the Bell Housing, an adapted
Input Shaft, similar Friction Clutch
mechanism, all from a manual transmission gearbox and, an axle differential.
The Input Shaft is connected
to a Cog wheel that drives a toothed Belt which then drives another toothed
Cog wheel attached to the main transmission unit at some reduction ratio. My
main Transmission is simply a modified automobile axle differential. This unit
converts the drive line into a 90deg drive system for the Main Rotor while
providing further engine speed reduction. A coupling off of this unit will
drive the Tail Rotor mechanisms.
4. I am still working on the Main Rotor/Propeller Blades, will definitely be
of a Composite material but the ones
out there seems to cost quite a bit; any ideas on how to get around this
without breaking the bank?
Regards,
Chidi Okonkwo
I think you guys are right about not messing with a vertical installation.
I've got some other ideas that should allow me to fit the envelope I'm
working with and get the weight where I want it. For one thing, I think I
can come up with a centrifical clutch that will also function as a sprag
clutch. The torsional dampener can be incorporated into the flywheel. One
question I need answered is what RPM can the engine--I'm thinking about the
Renisis--run continuously while varying manifold pressure for required
torque and what manifold pressure will be required to achieve 200hp at this
RPM? Is 5500 a good number?
Steve Brazil
Yeah, I thought about using a Centrifugal Clutch system but was a bit
worried about potential slippage at high power demand. Should work as well
though, I guess. Another thing that I consider necessary though not mandatory
is a simple brake system for the Main Rotor.
Most people have recommended an average 6000RPM for the 13B for airplane
operation, I am looking at an operating window between 5000RPM to 6000RPM
for my gear ratios.
How many seater capacity are you working on? Are you making the Rotor
Blades yourself?
Regards,
Chidi Okonkwo, TX.
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