I'm lovin' the info...too bad I couldn't find an info-sponge smilie to post.
The diesel trans setups I speak of are engineered from the ground up for trolling valves, and the circuits are in place whether you buy that option or not. Great big coolers and lots of clutch area (we're talking 1200 cid diesels here with humongous torque output). Can you slip the clutches in a huber or velvet drive? I'd say yes, with very REAL limitations...
I'd say that you would need to stay below 1500rpm for sure with slipping engaged (easy enough to add an MSD 2-step with a 1500 rpm chip to run in parallel with the slip solenoid circuit).
I don't know if the pressure passages in those trannys will allow you to tap in and fit a dump solenoid easily, but if you can, then I'd say it can be done easily enough (but that first IF is a big one). The dump solenoid will go in the pressure line before the shift selector valve.
If you are serious about doing this, then figure out first where to tap into the pressure FEED line to the control valve (FWD/Neutral/REV valve) and start off by diverting ALL of the flow back to the sump. This will result in NO motion. You can then start restricting the flow back to the sump a little at a time, taking care to monitor the fluid temp GOING TO the cooler. I'd test at 1500rpm, and test at very low pressures (virtually open return flow back to the sump) watching for a fluid temp rise (you gotta start off with a fully warmed tranny) of maybe 15 degrees. If you can slip at 1500rpm for five solid minutes and get the propshaft speed you want at less than a 15 degree rise in fluid temp then my "guess" is that you're kosher.
** as far as docking with high pitched props, I find that (up to a point) increased pitch makes maneuvering even easier. It's the idle speed in gear that gets to be a hassle. Keep in mind, too, that a cone shift (Bravo) or dog shift (Alpha & outboards) DO NOT LIKE being shifted with high pitched props. At ALL. A hydraulic clutch trans, though, (Velvet Drive, Huber, TwinDisc, ZedF, etc) could care less what prop you got hung off it unless you're shifting at an rpm higher than recommended. **
I see London, I see France...
I'm lovin' the info...too bad I couldn't find an info-sponge smilie to post.
What about an overdrive like on a car? Have a 2-speed tranny with an overdrive....have the engines spinning 2K and be cruising. What do you think of that? Would also save gas too. If any race came about, you just down-shift to the lower gear like a car to accelerate. Just a thought.
Good question Martini... And the simple answer is that there is absolutely no good reason why multi-speed trannies are not more readily available in boats. Other than the fact that this is a funny industry which seems to be doing its best to resist every sort of progress. We all know that surface drives are crap, that diesels are no good, that stepped hulls are deadly devices... Hell, even EFI was a bad, bad idea a few years back.
Anyway, ZF 2-speed trannies were developed on my boat, fitted with 4 Yanmars and Trimax drives. Sure, we had some problems but this was in the previous century. Since then, the system has been made reliable and it offers all the advantages cited above. Firstly, it wastly improves acceleration which makes your boat more fun. Even a big pig like mine (23 000 lbs. dry) will get on plane in under 4 secs and get to 60 in about 10. And I'm not even joking! It also improves your planing ability. I can plane at 15-16 knots which means that I can actually avoid beating myself up if I'm caught up in some rough stuff. It also dramatically improves fuel consumption and spares your engines at cruising speed. Instead of cruising at 3000 RPM with a single trannie, my cruise speed is at 2700 RPM now. Oh yeah, I also have a higher top end because the acceleration-speed compromise is much less of a worry now when picking ratios and propping the boat because I just have the first gear for acceleration and second for cruising and top end. As for docking, those trannies actually cure all problems of those horrible surface drives. In first gear, I have more torque readily available which makes the boat react instantly to shifting. Which makes it nice and maneuverable.
Any disadvantages? Nope, apart from the fact that they are about 60 lbs. heavier than single speeds. Big deal... And the fact that you can't fit them in those engine compartments which are designed to take only V8s and Bravos. But that's to do with manufacturers who should pull their heads out of their *** and start thinking a bit outside of the box, be a little more flexible in their approach...
As for UIM and other governing bodies who actually outlawed stuff like Lamborghini's 5-speed trannies, they should do the same. Their reason was to lower running costs. Well, that sort of backfired. You see, guys have to push harder now with their single trannies to stay in the right torque range which means that they sometimes overcook it in turns or attempt to run too fast in rough seas. The result is a noticeable increase in accidents. What a saving! I bet it's cheaper to repair a busted carbon-fiber Tencara cat than it is to buy a multi trannie...
One last thought. If you're still against the idea of having multiple gears on your boat, I want you to take your manual sports car out and stick it in third. Then, go on your favourite mountain road and have a blast, all in third gear. Then come back and tell me how much fun you've had. Not a great deal I suspect and yet, that's exactly what everyone's doing with boats. And accepting it, no questions asked...
with a transmission would'nt a variable pitch prop be in order. The tranny allows the engine to run at a more constant RMP as the wheels change RPM. With out burning rubber, the wheels and vehicle speeed are related. IN a boat, prop slip allows the engine RPM and prop RPM to be related, without regard to boat speed.
Actually, commercial ships ie. ocean-going tugboats, tankers... have variable pitch props for that reason (newer and better ones at least), to offset the fact that they have a single speed trannie. The torque of those engines pose problems in the development of multi-speeds which are unsurmountable for the moment. In other words, it is easier to have variable pitch props than more than one gear to solve that problem. In offshore powerboats however, it is very difficult to have a variable pitch prop given the speed of rotation and the stress placed on prop blades. A better solution therefore is to have a multi-speed trannie.
Years ago I had one of those variable pitch props (Land'nSea?) on an outboard with about 225 hp. It worked very well. I talked to the factory about something for more horsepower for ski racing and they practically hung up on me. They knew how much power we raced with. They also refused to offer a prop for twin engine use, they weren't sure they could make them shift together.
Jerry Gilbreath has in interesting story about auto's in the European offshore boats. Seems that after the Alcone boat won everything in sight here in the U.S., they went oversea's and got their doors blown off. The rules overthere allowed multispeed autos and it made a great difference. This goes back a few years and I don't follow what they're doing in Europe now...
When I say variable, I mean physically changing. Like a helicopter blade.
maybe adjustable would be a better term
Good discussion, and Super Termoli has it about right.
There are a few reasons more to have multispeeds, but from our experience, an automatic tranny, a crash box, or a dragbox like a Lenco or a Liberty, are not the best solutions to the problem of shifting gears in a boat. Autos can't handle the slip, crash boxes crash, and drag boxes only upshift.
We developed semi-automatic gearboxes that are computer controlled, air shifted, have no clutch, and always have more than 2 speeds if we can help it. The driver hits a switch, the computers do the rest. Simple, reliable, and huge performance gains come with it.
The first trans my dad (Pete Weismann) did for boats was for a boat called Momma Maritime. It couldn't get on plane, so my dad made a trick automatic tranny for it, problem solved. That was in the 60's.
In the '80's, he convinced Betty Cook to try a 2 speed manual, no clutch, no converter. One of the reasons he first put multi speeds in boats was for the simple fact if you loose one engine way out at sea, you could still finish the race on one motor because you can keep it on plane. At the very least, it wouldn't take you hours to get home, it was a matter of minutes. We won the UIM World Championships that year (I think it was 1987).
In 1996, we came out with 3 speed semi-automatic gearboxes in a modified cat called Zerodefect and won every race in the APBA Open Championship. The next year multispeed were banned here in the US and it has been that way ever since.
During the years 1998-2000 in Europe, we campaigned 3,4 and 6 speed semi-automatic transmissions in UIM. We had tremendous success combining the gearboxes with stock twin turbo diesels, winning the World, European, and Pole Positions Championships with the Victory Team in 1999 and 2000.
Super Termoli - Lamborghini made 4 speeds, and they tried to make a 6 speed work; but they had no 5 speeds.
In 2001, UIM banned multispeeds, and they still are today.
Well as stated above, one main reason sighted was money. Our competitors in Europe (there was 3 of them) couldn't get it figured out, and they cost their customers a lot of money thru repeated and often catastrophic transmissions failures. Shifting transmissions without a clutch or converter, and running behind engines with over 1200 hp, is not easily accomplished!
Most of the guys running in UIM have plenty of money, so money was a very poor excuse. The only other choices were to spend more money to try to out think us, or throw all their existing stuff in the trashcan, and buy our transmissions; or ban transmissions.
And as stated above, after the ban, they started to having more crashes because they were trying to keep the speeds up thru the turns. Over the season, with no transmissions failures, the additional costs of having transmissions far outweigh the cost of repairing a crashed boat. The same can't be said for anybody else's trannies though.
In the US, we had no competition. The only option was to change the rules because the big M was not about to try to design gearboxes, they can barely do a drive!
The technology of multispeed transmissions has been completely arrested world wide. Boat racing, like Nascar, has now proved to be totally nonconducive to innovation, and thusly (I'm only going to use it once) the technology does not exist in boats for the general population.
The idea of putting transmissions in boats is valid. I encourage anybody out there thinking about it to do it. A lot of the methods discussed above are perfectly fine for most of the applications out there, so there is no excuse.
2 speeds are just OK, more is better!
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