# Do airboat gear drives really work?

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#### Autodidact

##### Well-Known Member
I don't want to create a definition "what works" or in this case, "sufficiently reliable", what I would like to know and think would be helpful to know is what kind of quantifiable track record do these gear drives (airboat only, and geared only, please...) have when used in aircraft. Reliability is a degreed assessment, so to what degree are these devices reliable. So the key identifiers for this thread are "airboat", "gear drive", and "used in an aircraft". Are there documented experiences (logs) of usage, type of usage, flight hours, any failures, durability (time between rebuilds), etc. I only know of two airboat gear drives used in aircraft: an RV6 and the Radial Rocket derivative. Surely there are others - how did they work out in the long term?

#### rv6ejguy

##### Well-Known Member
I'm not sure there's a big difference in the applications. Ballistic gives you a 2 year warranty as long as there is oil in the drive I believe. Given that many airboat engines are producing over 600 hp, seems like running at 300ish in cruise would barely tax them.

#### vhhjr

##### Well-Known Member
HBA Supporter
I have not used one, but Casale Drives appear to have been used in aircraft. They are rated for up to 1000 hp in boat use.

http://www.casalev-drive.com/

#### Lendo

##### Well-Known Member
Gearboxes (Reduction Drives) DO actually work very well, if their designed right and built right and run with sufficiently cooled oil. There is a member who posted on here his desire to design and manufacture such a Gearbox, but I believe he's still working on the project, he is a Mechanical Engineer. I believe he's suggesting a torsionally stiff Internal Spur gear design capable of handling well in excess of 200 hp at approx 50 lbs. Naturally the issues of Torsional Vibrations must be considered, with each engine type - that is true of any reduction drive/ Gearbox.
George

#### pfarber

##### Well-Known Member
HBA Supporter
Gearboxes (Reduction Drives) DO actually work very well, if their designed right and built right and run with sufficiently cooled oil. There is a member who posted on here his desire to design and manufacture such a Gearbox, but I believe he's still working on the project, he is a Mechanical Engineer. I believe he's suggesting a torsionally stiff Internal Spur gear design capable of handling well in excess of 200 hp at approx 50 lbs. Naturally the issues of Torsional Vibrations must be considered, with each engine type - that is true of any reduction drive/ Gearbox.
George
Most PSRUs have implemented a 'soft drive' where the flywheel bolts have neoprene-like material for dampening. Similar to springs on manual clutch plates.

One thing I would like is a centripetal clutch... but I'm not sure the price is worth it. I've had to manually push start lots of motors and never worried about the crank/internals being damaged.

Another 'wish list' item would be an oil cooler. But with the propwash hitting the case there may be enough cooling to keep the oil from breaking down.

#### Riggerrob

##### Well-Known Member
Definitely install a PSRU temperature gauge.

#### PW_Plack

##### Well-Known Member
Some airboats are used for working, like towing fishing nets.
Mark Kettering at AeroMomentum told me one of his airboat customers for the 1.3L Suzuki conversion tows nets, running high power almost continuously. Mark says the guy recently wore out his first short block (after running past recommended TBR) and ordered a new one, but declined to replace the cylinder head, accessories or gearbox. That will be an interesting long-term beta/guinea pig.

#### Bigorneau

##### Well-Known Member
Casale gear box work perfectly on E-Racer model Mk1 with 240 hp from V8. (see avatar of my E-Racer MK1)

HBA Supporter

#### Dennis K

##### Member
For what it's worth I've watched aircraft engined airboats run up fast-flowing rivers in Alaska for hours at high power levels while salmon fishing the Copper and Tanana Rivers. Also had a few trips in a four place VW-powered hovercraft on the Tanana river that was screaming its guts out for hours all day giving demo rides some years ago.

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