Do airboat gear drives really work?

Discussion in 'General Auto Conversion Discussion' started by Autodidact, Jul 14, 2017.

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  1. Jul 14, 2017 #1

    Autodidact

    Autodidact

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    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?
     
  2. Jul 14, 2017 #2

    rv6ejguy

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    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.

    This would certainly be the way I'd go for a high hp auto conversion rather than the $15K+ stuff from other vendors making drives designed for aircraft with a fraction of running hours on them by comparison and a number of known failures.
     
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  3. Jul 14, 2017 #3

    cheapracer

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    Ballistic are at $3300, good pricing once you get out of "aviation" tags, there's a few airboat redrive companies by the looks of it.

    This may be of interest for some, 40HP V Twin Kohler engine redrive ..

    http://www.centurydrives.com/briggs_mini.htm
    http://www.centurydrives.com/briggs_mini.htm
     
  4. Jul 14, 2017 #4

    Autodidact

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    Airboat gear drives obviously work, the question I have is how well for an aircraft. The duty cycle for an airboat is not the same as for an aircraft; airboating is about being in nature and looking at scenery. I've been watching the longest you tube vids I can find and what I see is airboats cruising at low power for 5 to 10 minutes, stopping to look at something and then continuing on again at low power. The high power bursts are used for getting over embankments or going overland a short distance to get to other water. Air boats have a lot of thrust but it is held in reserve and used for tight spots.

    The only airboats that would even come close to an aircraft duty cycle are the government agency patrol boats and even then those guys are more interested in seeing whats happening on the bank than in making multi-hour runs at a constant high power setting. There's a big difference between cruising at high power for 30 minutes then stopping for a minute or two, and high power for 2 1/2 hours straight. The hardest duty I can think of for an airboat would be on ice choked rivers up north. I think that the best comparison of airboat and aircraft operation would be an extrapolation and I don't think that is accurate enough. But, the fact that these gear drives are used on patrol and rescue craft is encouraging, although I would hate to build an aircraft to haul a load some distance only to find out that the gear drive could not handle the stress. Hearing some quantifiable specifics from aircraft operators would be much better than knowing that they work well on airboats. I really hope that the technology can successfully cross over - I mean really successfully as in equivalent to the reliability of certificated aircraft gear drives (which is the most you could hope for). I think the market for airboats is big enough that use in aircraft would not be disturbing enough to cause some kind of shut down of manufacturing or unreasonable restrictions on purchase and use, IOW if the airboat drives became common on aircraft they would be here to stay and that aircraft usage would not be made difficult because of liability concerns.

    The people that have used them say that they work fine and I suspect that they do, but I would like some real numbers.
     
  5. Jul 14, 2017 #5

    rv6ejguy

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    Like you said in your original post, few in use in aircraft so you won't find a big database.

    Some airboats are used for working, like towing fishing nets. It takes quite a bit of power to cruise fast on step too- I'd guess 60-100hp depending on size of the craft. Some of the racing stuff is over 1000hp. If it can stand 1000hp for even 30 seconds at a time, taking 200-300hp continuously for many hundreds of hours would generally be no issue based on my experience with manual transmissions in racing cars. Ballistic doesn't specify a hp rating. They used to say if you break it and it has oil in it, they will give you a new one. Must be pretty confident in the design to say that. The aircraft gearbox guys generally give you NO warranty.

    If a gearbox is not making any metal, it's usually going to be fine. Regular checks and maybe a chip detector and I'd feel pretty safe using one.

    I would worry about the liability angle though.
     
  6. Jul 14, 2017 #6

    Autodidact

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    It's very tempting; even an iron block and heads SBC will have about 1.83 lb/hp and aluminum heads/iron-block can be @ 1.5 lb/hp with one of these redrives. An LT-1 engine making 300 hp can be bought for around $2500. It almost seems possible to have 300 hp for $8,000!
     
  7. Jul 14, 2017 #7

    TFF

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    There are a few RV10s I think. If you can handle the weight, its probably not an issue for a cross country airplane. I have a feeling its one of those things of if you get a good one, you have no worries. In a boat if its making metal, you still go out on the lake until it blows up all the way; you might back off the last 5 min and laugh about the noise. The what if is what gets the airplane; boat is like jumping a monster truck, Go!
     
  8. Aug 14, 2017 #8

    TXFlyGuy

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    It appears that Ballistic does not work with a constant speed hydraulic propeller. This would make the item of little use in the high performance, high horsepower applications. High hp being defined as 300 and up.

    EDIT: I suppose an electric prop could be used.
     
    Last edited: Aug 14, 2017
  9. Jan 29, 2018 #9

    rv7charlie

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  10. Jan 29, 2018 #10

    Wanttaja

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    [Deleted]

    Ron Wanttaja
     
  11. Aug 1, 2019 #11

    PTAirco

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    '

    I don't know what videos you've been looking at, but it seems to me an awful lot of airboats are being used by yahoos who run the hell out of them.
     
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  12. Aug 2, 2019 #12

    tailwind

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    I visited Ballistic Gear Boxes manufacturing facilities a few months back on a driving trip. They are very willing to work with exp aircraft. Was quoted $4400 for an aircraft box. Looked like a good heavy duty box. Yes heavy 78lbs.
     
  13. Aug 2, 2019 #13

    vhhjr

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    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/
     
  14. Aug 3, 2019 #14

    Lendo

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    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
     
  15. Aug 3, 2019 #15

    pfarber

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    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.
     
  16. Aug 4, 2019 #16

    Riggerrob

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    Definitely install a PSRU temperature gauge.
     
  17. Aug 5, 2019 #17

    PW_Plack

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    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.
     
  18. Aug 5, 2019 #18

    Bigorneau

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    Casale gear box work perfectly on E-Racer model Mk1 with 240 hp from V8. (see avatar of my E-Racer MK1)
     
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  19. Aug 6, 2019 #19

    pfarber

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    That sounds noisy.
     
  20. Aug 6, 2019 #20

    Dennis K

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    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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