"Fly the Best - Fly a Pro"
Select the subject letter of your interest from this list:
Name Location Subject
Joanne Boyer Honesdale, PA Main Rotor Drive
Daniel Wilkenson Kalamazoo, MI Main Rotor Drive
John Pohlman Westminster, MD Main Rotor Drive
Dr. David Rhodes Fayetteville, AR Main Rotor Drive
B. J. Schramm Main Rotor Drive
Field Data Collected Main Rotor Drive
"Since installing the Pro drive system I have seen
oil temps drop from 195 degrees in hover to 170 degrees. The secondary bearing
temp has not reached 150 degrees in a sustained 1:00 hour hover. You can leave
your hand on it after flight. Starting seems easier and the blades turn longer
than usual on the shut down.
Everything John stated in his representation of the system has been very
accurate. The installation was simple and straight forward. The oil bath is
gone, and what a blessing. We did have some belt slippage attributed to oil from
the oil bath. Also had a problem with oil from the bath contaminating the grease
in the secondary drive. Had replaced so many seals in an effort to rid the
engine compartment of the mess and had just about given up when we decided to
try this new drive. To those of you who would insist that the installation of
the chain bath and seal was responsible for the leaks, you should be aware that
we even brought in a well respected expert in RotorWays to install one, and it
too leaked! We tried the new ones and the old ones with no improvement.
We hope to never go back to the chain drive. We are actually flying regularly
now because we don't have to spend an hour or two after every flight cleaning up
the engine compartment."
Mark & Joanne Boyer
"I have built 6 RotorWay helos - three were Award
winners at Oshkosh. We installed a cog belt drive from John Spurling in an Exec
90 with 173 hours on it. We have 18 hrs. on the drive system with no problems. I
have roped on this belt with two heavy people on board. I tried to work it as
hard as I can. It autos with 1 person on board and 1.5 degrees down pitch just
fine. It will over-speed if you don't pull some pitch into it. You know, it
doesn't leak one drop of oil, and the water and oil temps are both down so much
we installed a thermostat to warm the engine in Michigan. The secondary bearing
runs cool enough to hold on to with your hand - we can't do that with a chain
drive. I have had to force land many times with belts slipping, most times from
oil leaks from the chain case.
After building, flying, and force landing these RotorWay helos for 11 years,
then installing a Pro-Drive, everyone should convert as soon as possible!"
"We have installed the Pro-Drive cog belt
modification from John Spurling and are extremely happy with its performance. I
have built and helped build several RotorWays and have considerable experience
in the engineering and machining trade.
The ease of preflight and the fact that the engine and secondary bearing run
considerably cooler, was worth the effort. The installation was easy and no more
oil mess above the drive belts. I only want our ship to be trouble free, safe
and fun to fly and I see this belt as a way of enjoying our ship even more. I
too was and am a pessimist when it comes to "new",
"improved", "but wait there's more" gadgets. I did
interrogate John to death about the specs and got the books myself and talked to
other people that had the drive. When I bought the drive belt it had well over a
hundred hours on it (this is the life of the chain by the way). The belt is
still going on several ships. As for autorotations, the belt will have a lot
less drag and require you to add collective a lot quicker to keep the rotor in
I have had no engine fires but have had oil leaks from the valve cover. This
spoon full of oil made the engine compartment look like a major oil line had
broken. I can't imagine an oil leak from the oil bath and did not want to even
take that chance. We had to land prematurely because of belt slippage from the
chain oil bath seal in a friend's RotorWay. It took hours to clean everything
up. The preflights are much safer now because you can see ever thing in the
helicopter including the main drive. I had a treat adjusting the valves because
now you can see the "hole" in the flywheel easily and the secondary
drive pulley is easier to grab to turn the engine.
To sum it up I have found everything so far as quoted from John to be accurate
and even found more benefits than quoted. I am extremely happy with the system
and only wish I had the chance to install it sooner."
"Just had to put in my two cents worth on the
Pro-Drive cogbelt system.
Mine works. Fifty hours, zero maintenance, zero anxiety. My engine compartment
was oily before the cogbelt. Now it's clean and dry. The radiator fins are
clean, dry and open. The exhaust wraps are dry. The main drive belts, tail rotor
belts and other belts are dry. My oil and coolant temps are always in the green.
The factory ships run with the oil temp in the yellow. My radiator isn't clogged
with oil or blocked by the oil bath. My secondary shaft bearings are now cooler.
The grease no longer gets washed out of the bearings by the leaking oil bath
seal. I have made two forced landings because of main belt slippage prior to
conversion. My secondary bearings no longer overheat. Vibration and noise are
subjectively less than half what they were before the cogbelt conversion.
I carefully analyzed the system before I purchased one. Calculated the stress
the cogbelt puts on the secondary shaft and found that it is a drop in the
bucket compared to that created by the engine torque alone. I also found to my
surprise that there is no way to sideload the secondary stub without overheating
Then consulted a friend of mine who is an industrial technologist. He told me
about having worked at a local food processing plant back in the eighties, where
the quad-100 chain drive kept wearing out. He converted it to a cogbelt. It's
still running night and day.
Rotorway is a wonderful company with a wonderful product. They will adopt the
cogbelt in due course. But meanwhile, there are going to be more engine
compartment fires and secondary shaft failures due to oil seal leaks.
Experienced airmen/builders who have common sense and confidence in their
knowledge of mechanics and materials will be wise to examine this modification
Dr. David Rhodes
According to B.J. Schramm, who developed the RotorWay line of
"This is the best single improvement to the RotorWay aircraft since I left
Up to 25 degrees F. lower water temperature.
Up to 25 degrees F. lower oil temperature.
Over 20 lb. more useful load.
Major reduction in cabin noise and vibration.
Up to 50 degrees F. lower secondary bearing temperature.
Better viewing of engine compartment, allowing safer pre- and postflight
NO OIL BATH
Oil free drive belts, exhaust manifold, radiator and engine compartment.
Less and easier aircraft maintenance.
Less friction in drive system allows better auto rotations.
Better power coefficient for hover and forward flight.