Donald,
I was not familiar with the the “shuttle term” as to transmissions so I looked it up.. Based on what I read and could surmise, I’d guess the basic design is based on the combo “oil in shear”wet clutch design and a full lock-up design after initial changing of gear the the from fwd to reverse…There might even be a fluid coupling with a lockup feature in it hidden it the design.
But I would also surmise this………..These transmissions are many times more robust as to both external size and weigh on the HP to HP basis compared to a marine transmission used in planing hulls where weight and size play a major part in design ( or actually” lack of” weight & size)..
Let’s take s ZF220A gear–Rated to close to 400HP at 3000 RPM ( like on the back of a QSB 3.9 380).. Under 120 lbs.. Maybe a front end loader from the 70’s & 80’s with a 200 HP John Deere had a “Shuttle Gear” gear that weighted over 1000 Lbs?.. It’s not a “apples to apples” comparison.
On the other hand, we do use heavy duty marine gears on lower HP engines that have very smooth engagement and you can shift back and forth at maybe 1000 RPM and you hardly feel the shift as the clutches build pressure over a 2-3 second period that are designed to slip in the “oil-in-shear” mode during this process.. A typical gear we use weighs about 400-600 lbs and are used on a 200-300 HP engines. That would not be “performance or fit friendly” in a 28-30 Ft 8000- 10000 lbs performance boat. Our start-up videos show many of these gears “in motion” ..
Anyway, “shuttle gears” are a neat design.
I am going to post a design & video we put together in a commercial application about 25 years ago that will get you thinking as to shifting fwd to reverse. Just have to get it from a VCR tape to U-Tube 1st–That’s a “Corey job.. He has not even seen it..
Tony
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