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From all the
e-mails and calls we get, these are some of the most frequently
asked questions.
Bud is delighted to answer any and all - just send him an
e-mail. Please remember - most of the time
he is up to his elbows in aircraft
engines - so it may take a day or two to get an answer.
Click on the question in the list below to go
to the answer!
What temperature does the PSRU operate at?
How is the
PSRU lubricated
What
type of oil is recommended?
How much oil
does it hold?
How does the prop governor work on your PSRU?
Will my prop governor work with your PSRU?
Why
do you use a centrifugal clutch?
My old PSRU chatters and jumps around at low engine RPM.
Does yours?
How do you resolve torsional vibrations?
Any plans for a Geared Drive PSRU for Mazda?
Have you looked at the viability of using a small
block/PSRU combination on an RV-10?
Why build a FWF package for the RV-10?
How much
does an LS1 weight vs. O-540?
How does the engine RPM of the LS1 compare to the O-540?
What about planetary gears in a PSRU?
I heard that you were renovating an airplane and using a
supercharged 4 cylinder Chevrolet Ecotec.
How is that coming along?
I heard that you lost your test bed airplane. What
happened?
Bud Warren’s plans to replace the Wheeler:
Do you test run each Geared Drives PSRU?
Thougts
on Chevy Engines and the PSRU in P-51’s
How about Chevrolet engines for Twins?
How about Diesel engines in airplanes?
How did your PSRU fare after the fire and forced landing?
How much is your PSRU and what are the terms?
How much horsepower will your PSRU take?
What
about the Ecotec and a Glasair?
What temperature does the PSRU operate at?
Our PSRU runs cool. High temp for our unit is 150 degrees F. Temperature
We test run each unit for an hour each, and the highest temperature we
have seen is 120 degrees F. Temps usually do not even register on a
140-260 degree F gauge.
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How is the PSRU lubricated?
This unit has a separate oil reservoir with its own oil pump and
filtration system, lubricating all of the gears, bearings, accessory
shaft, prop shaft, prop and prop governor with clean, filtered oil as
long as the prop is turning.
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What type of oil is recommended?
You must use mineral type,
non-synthetic gear lube with anti-foaming additive in our PSRU, of the
type labeled for fill up, not just top off. You will not be able to use
ANY synthetic oils, as they do not provide proper lubrication and the
PSRU will heat up. No synthetics at all. We have learned this in testing
and actual use that synthetic gear lubes will not adequately lubricate
this gearbox and keep it running cool. Synthetics work great in engines,
but not in gearboxes.
What kind of oil do is required?
In the last twelve years or so, we have tried virtually every kind of
oil and gear lube that there is, including five or more major brands of
synthetic gear lube. Crazy as it sounds, the only lubricant that has
provided appropriate cooling with quiet and smooth operation is a
mineral gear lube that has an anti foaming additive, labeled for fill
up-not just top off. This is so important that we must tell you that you
will void your warranty with Geared Drives is you use any other
lubricant. Synthetics work great in auto engines, but fail miserably in
a gear box environment like our PSRU. Synthetic gear lubes in this
application simply did not provide adequate cooling or lubrication, as
evidenced by the high operating temperatures and gear noise.
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How much oil does it hold?
The Geared Drives PSRU holds two quarts of gear lube. If you choose to
use an oil cooler, simply add the capacity of the oil cooler and the
lines to the fill up volume. Use only 85-140 mineral type gear lube with
anti foaming additive. Be careful to only use gear lube labeled for fill
up, not just for top off.
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How does the prop governor work on your PSRU?
The Geared Drives PSRU pumps fresh filtered lubrication throughout the
entire system, including supplying oil to the prop governor, We have not
found any brand of prop governor that does not work properly with our
system. The prop governor itself is an oil pump, so as long as it has a
constant steady oil supply it will work just fine. Even though we are
supplying oil at 60 PSI to the prop governor, we have found that a prop
governor does not require a massive quantity of oil if the governor and
propeller are in good repair and are not leaking. We have even cut down
the oil flow with a 1/8" orifice and the prop governor still works
correctly. We do not have oil temp problems, governor problems, no
problems at all with our PSRU.
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Will my prop governor work with your PSRU?
Our PSRU has its own oil pump and filtration system, force feeding clean
and filtered lubrication to all the components of the PSRU, the
propeller and the prop governor. Our unit has two outlets on our prop
governor mount, which is built into the case, so that you can use a
clockwise turning or counter clockwise turning prop governor equally
well. Just bolt the governor on, if it does not cycle, change the oil
line to the other port on the top of the PSRU case and plug the port you
do not use. We have not found a governor that does not work on our PSRU.
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Why do you use a centrifugal clutch?
The centrifugal clutch serves well in a number of ways. The clutch
itself serves to resolves torsional vibration by means of a set of heavy
polymer coated springs in the center of the clutch disc. Since the
clutch disc, flywheel and pressure plate do not constitute a hard
connection, there is thought that perhaps some of the harmonic issues
might be solved there as well. In addition, the centrifugal clutch
engages the prop at low RPM and after the engine is already running,
which could dramatically extend the life of your starter.
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My old PSRU chatters and jumps around at low engine RPM. Does yours?
No. We tested our PSRU for literally hundreds of hours on the ground and
experienced no chattering ot vibrations at any RPM. We flew our Wheeler
for nearly 700 hours with great success and no torsional vibration. Our
PSRU operates smoothly at every RPM.
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How do you resolve torsional
vibrations?
Years of designing, redesigning, going back to the drawing board and
starting over, has yielded a design which utilizes a custom designed
centrifugal clutch assembly. This was designed specifically for use on
an automotive engine for experimental aircraft, and incorporates a
center clutch disc with polymer encased springs. This use of this disc
not only makes the system work and eliminates torsional vibration, it
offloads the engine long enough get it started which avoids strain on
the starter.
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Any plans for a Geared Drive PSRU for Mazda?
Please understand that I mean no offense with this answer. Years ago,
when I started working to develop and engine and PSRU for an airplane, I
chose the Chevrolet because it was lightweight, easy to get, anyone
could work on it and it was not difficult to accessorize or keep an
exhaust system on. Parts were plentiful, engine RPM ranges for best HP
and torque made sense. I could run the engines in a low RPM, get lots of
HP and torque, and amplify that torque to my prop without excessive
engine heat to have to deal with. Lower RPM means less heat, longer
engine life, lower fuel burn, and it all made sense to me
Contrast my philosophy with some of the facts that we already know about
the typical Mazda engine for aircraft use. They run extremely hot, have
oil temperature problems galore, and they certainly are not light
weight. The excessive temperature puts their exhaust systems are under
such pressure that they don’t hold up well. I also do not like that they
run at high RPM all of the time. In the automotive world the Mazda
engine is considered to be a “throw away” in that they are not designed
to be re-buildable, which simply does not appeal to my mechanical mind.
But again, that is my personal opinion. There are many pilots out there
using a Mazda engine and many have come to me asking if I could develop
a PSRU for their engine. Though there is not currently a plan on the
table to develop a Geared Drive for the Mazda, it is not entirely out of
the question for the future.
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Have you looked at the viability of using a small block/PSRU combination
on an RV-10?
Yes! This is perhaps the most exciting thing we have done to date! We
think that the RV-10 was made for a Chevrolet LS1 and Geared Drives
firewall forward package, whether they know it or not! We have developed
a bolt on package that comes complete with engine mount, LS1 engine,
Geared Drives PSRU with oil pump and filter assembly, alternator,
starter, headers and exhaust system, engine wiring harness, ECM,
radiator and all cooling lines and hoses. Also includes the fiberglass
blister kit that will be needed for cowling modifications in order for
the stock cowlings to fit. This package has been engineered, test run,
and upon delivery will be ready for an RV-10 builder to add his prop
governor and prop, tie in the electrical system and other controls and
be virtually finished with his engine installation. You have spend a
great deal of time building your RV-10, you ought to have a choice for a
Chevrolet engine package that is ready for you to fly!
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Why build a FWF package for the RV-10?
The RV-10 is a perfect airframe for an engine such as the LS1. The LS1
and Geared Drives PSRU FWF Package is ideal for pretty much any
application that would normally have called for an IO-540 or O-540. The
LS1 engine package, ready to run with all accessories, including
radiator, starter, alternator, oil and water, comes in about 20 lbs less
that the O-540. So the old myths that auto engines are so heavy is not
entirely accurate when you consider the modern auto engines of today.
Too many have requested that we develop a firewall forward package for
the RV-10 that would allow the owner to basically bolt the thing on,
wire it up, hang the prop, and go fly. The noise from the public became
so loud that we decided to develop this package. We have achieved our
goal, and will unveil this package at Sun N Fun in Lakeland, FL in
April, 2008.
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How much does an LS1 weight vs. O-540?
The ready to fly weight of the LS1 (less prop), complete with PSRU,
flywheel, engine, radiator, all accessories, including alternator and
starter, water and oil, comes in just under 500#. The O-540, equipped
same as above, weighs 520# (less prop). Yes, the LS1, ready to fly, less
prop, apples to apples, weights in less than an O-540 and has a lot more
horsepower.
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How does the engine RPM of the LS1 compare to the O-540?
The LS1 will happily operate at higher RPM than the 540. What makes the
difference is that the O-540 as a reciprocating engine which has a long
stroke and monstrously big and heavy pistons. The LS1 runs at a higher
RPM than does the O-540, but the rods and pistons are so very much
smaller and lighter that the certified engine pistons. Put this into
perspective, only one piston from out of a 0-540 weighs nearly what an
entire set of LS1 pistons weighs. The lighter pistons of the LS1 in this
smooth running and well balanced engine are not creating a lot of wear
and tear in the engine. The LS1 engine is capable of a lot more RPM with
no problems at all. Chevrolet has tested these engines unmercifully. The
engine RPM range that we advocate using for aircraft use is really quite
mild for the LS1. We like to see takeoff RPM’s around 3900-4000, not
because more is hard on the engine, but because this is all you need for
awesome performance and fantastic climb rates when combined with the
Geared Drives PSRU and a constant speed prop. You can even go up as high
as 4200-4300 RPM if you have a heavy load, and it will not hurt
anything. With the Geared Drives PSRU, you will not over speed the prop
and you will have lots of excess power at your disposal. You will
however, need to be judicious in how you apply that power. These engines
have so much power that it would not be hard to torque-roll the airplane
if you apply it all at once.
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What about planetary gears in a PSRU?
I choose to use the best for safety and dependability in the Geared
Drive. For this reason, I am against the use of planetary gears in a
PSRU. Consider what they were designed for; to change an automatic
transmission from one gear and into another. They were designed to work
at high RPM for only short periods of service. They are very small and
turn at ultra high RPM when in continuous use, and from twenty plus
years of personal experience in professional auto racing, my personal
opinion is that there is any way that planetary gears can possibly hold
up long term. The strongest and most dependable kind of gear is a
straight cut spur, which is what I chose to use in the Geared Drive PSRU.
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I heard that you were renovating an airplane and using a supercharged 4
cylinder Chevrolet Ecotec.
How is that coming along?
The airframe was in a sorry state of repair, and being honest about the
condition of the airframe in the pre purchase inspection for my customer
did not deter him in the least! I begged him not to buy the airplane and
darn if he didn’t buy it anyway! I am a glutton for punishment and with
the agreement that it might take a long while to rebuild, and that I
would be the test pilot, I accepted the challenge. There was not a
single system on this aircraft that did not need major repair or
replacement. I chose to replace the old turbine engine with the
Chevrolet Supercharged Ecotec 2.0 L engine because I believe that the
engine has been proven, and I expect it to also perform well for
aircraft use. Initial cost of the engine is very favorable. The
supercharger allows you to keep more of your horsepower at altitude, and
it runs cool under the cowling, unlike a turbo charged engine, and does
not require any expensive and exotic exhaust components. We are
currently building the cowling for the aircraft and completing the
wiring harness and electrical system. I do not think I will be ready to
taxi test and begin test flying until after Sun n Fun.
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I heard that you lost your test bed airplane. What happened?
We were flying to West Houston Airport in my Wheeler, to an EAA chapter
meeting where I was invited to speak. We had taken off only a few
minutes prior, and the flight was proceeding as planned. Perhaps ten
miles from CXO I noticed that the engine oil temp was getting higher.
The water temp was fine, oil pressure was fine, and then the engine
coughed. Just a moment later we had smoke in the cockpit and I asked my
passengers to help me find a place to land because we were going down.
Losing power quickly I did a 360 in the air and saw a hay field in the
distance, the engine quit just before we made contact with the ground,
and we hit a couple of posts in the fence, taking out the left wing,
which sent the airplane into a spin on the fresh mown hay field. The
impact forced the landing gear up through the wings and we were spinning
on our belly and seeing nothing but fire all around, but once we got on
the ground and the airplane came to a stop, we were able to escape the
aircraft through the right hand door.
We watched helplessly as the aircraft burned to the ground. I had minor
burns on my fingers from the seatbelt clasp which had already heated up
enough to burn me, and a couple of nice goose eggs on the top of my
head. James bruised his ribs and recieved a slight flash burn on his
face, and my daughter Phyllis skinned her elbow on the wing tread
escaping the aircraft! We were very grateful to be alive, but heart sick
at the same time as the magnitude of the loss began to sink in. We had
lost the Wheeler.
Investigation proved that the source of the engine fire was a braided
steel fuel line which failed. This caused fuel to spray over the exhaust
on the right hand side of the engine, which burned the distributor cap
and spark plug wires off of the engine. The cough we first felt was the
first symptom of our ignition system burning. Apparently the oil
temperature sensor heating up from the fire is why we were getting a
high engine temperature reading.
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Bud Warren’s plans to replace the Wheeler:
Currently, we have had to place our plans for replacing our aircraft on
the back burner for a while. Business is such that we must focus all of
our time and energy on completing our PSRU orders and aircraft projects
currently in our shop in order to serve all of our customers. In
addition, we are making the final touches on the RV-10 firewall forward
package with Chevrolet LS1 and Geared Drives PSRU, which we will have on
a running engine test stand, complete with propeller and governor, to
unveil and run for attendees of the Sun N Fun Fly In at Lakeland,
Florida, April 8-13, 2008.
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Do you test run each Geared Drives PSRU?
Yes. We have an early model LT Chevrolet 350 engine that we use to test
run each PSRU. For break in, we bolt on an 80” Hartzell Propeller and
test run for one hour following the resolution of any leaks that might
be found. This allows the seals to seat in, and operating temperatures
to normalize. We run the unit from 500 RPM all the way up to takeoff RPM
of 3900-4500, and everything in between. We are able to cycle the prop,
make many engine RPM changes, and put the engine and PSRU through the
same paces that you would if you were flying it in your aircraft. This
way, we can ship these units out knowing that all is exactly as it
should be. To witness this test run is an incredible sight-the
smoothness and ease of operation is really rather incredible.
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Thougts on
Chevy Engines and the PSRU in P-51’s
I think that the P-51 is an excellent platform for a Chevy and the
Geared Drives PSRU. I met half a dozen or so fellows at OSH this year
with P-51 replicas and I am anxious to get one in the air with my drive
on it behind a Chevrolet. Apparently, some years back, they used to have
a source of a geared redrive that they liked to use, however it did not
have all of the accessory drives built in like ours does. I am told that
the builder is no longer producing the PSRU, and they are looking for a
supplier for a geared drive that will perform the way they need it to.
Our PSRU would allow their installation to be so much more simple, would
eliminate the additional accessory drives that many currently have to
use, and save on weight and initial cost.
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How about Chevrolet engines for Twins?
If you are considering two Chevrolet engines you could use marine parts
in your right engine for counter rotation. It would entail a marine oil
pump, camshaft, starter, possibly a few other details. The stock
alternator should work just fine. This really makes sense for a twin,
since you would then have no critical engine. I am sure that you could
build up an early model Chevrolet engine this way, but you might check
on whether you could match a late model LS1 engine with one for marine
application and that would be really nifty. My Geared Drives PSRU does
not care which way it rotates, works equally well both directions, and
for tractor or pusher, so we got you covered there. Our drive has proven
to be bullet proof on my 383 Chevy and I am very proud to be able to say
that.
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How about Diesel engines in airplanes?
The Geared Drives PSRU will not bolt onto a DuraMax Diesel, nor do I
advocate the use of a diesel engine in an experimental aircraft. My
educated opinion is that the engine stresses and power pulses would just
not be conducive for use and would likely tear up the drive. My drive
has proven to be the toughest one around and I would not put in on a
diesel under any circumstances because of the engine power pulses. High
compression, strong engine pulsations, etc, together with the limited
altitude ceiling for a diesel just do not, in my opinion, make any sense
to use in aircraft, both in terms of safety and cost, and come at a huge
weight penalty compared to Mogas auto engine conversions. I feel so
strongly about this that I will not sell any drive of mine to anyone
planning to use it on a diesel engine, even if it did bolt on. I do not
want to be any part of someone hurting themselves or others doing
something that goes against what I know is good sound advice.
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How did your PSRU fare after the fire and forced landing?
I salvaged the 383 engine and Geared Drives PSRU from the fire and
disassembled them to see how they fared from the prop strike and the
fire. Of course, the engine had lost power due to the fire taking out
the electrical system, The prop was just wind-milling when we hit, but
even so, I was humbled to find that the PSRU was totally undamaged. I
mic'd the prop shaft to within .001 of its original dimension. There was
no damage to bearings, bearing surfaces, shafts, or even the PSRU case.
If there was a good thing that came out of the whole thing, I can say
this unit is as bullet proof as I could make it. Sometimes you have to
laugh in order to keep on going, and I can laugh and say that we have
tested this unit all the way into the ground!
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How much is your PSRU and what are the terms?
I require a 50% Deposit when the order is placed, and the balance with
the actual cost of shipping when the unit is shipped. Currently our PSRU
prices start at $8,900 for the four cylinder and six cylinder
applications, and the PSRU for the LS series engines are $9,500. We have
to use a different flywheel so that you can use a GM starter, which I
supply as with the PSRUs for LS series engines.
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How much horsepower will your PSRU take?
We have had great success with 405 HP in our 383 Chevrolet for the
nearly 700 hours that we flew our test aircraft, so we can say for a
fact we know that it will hold 400 HP.
However, we have sold a PSRU to a Reno racer with a very high profile
airframe. This team places very high and it tired of that and wants to
win. They just sent us their flywheel from the big block that they are
going to run next year in place of their big certified engine. Our
agreement with them is that they will run our unit on their big block on
an engine stand this winter, to see if they can blow it up. If they do
manage to do that, we have agreed to do whatever it needs to beef it up
so that they can use it in their racer next season. The only way we can
find out if it has a weakness at that power setting is to just run it
until it breaks. We are pretty anxious to see what happens. They will be
running 700 HP and to date the most we have run is 400 HP with no
problems at all. We believe that we can help them win at part throttle!
Stay tuned for more news as we get it.
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What about the Ecotec and a Glasair?
I think that the Ecotec could be a great little engine for your Glasair
and will be able to tell you more after we have tested this engine in
the little Mooney experimental we are working on now.
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