small horsepower hydraulic drive

[marshmat]

Very interesting, Marine Nut.

If specifying such a system for more aggressive use (eg. not just for getting in and out of harbour), I would make one change to Tony's design: replacing what appear to be gear pumps with variable-displacement axial piston pumps. That should cut the losses in the pump from 15-20% to about 5%, leaving the whole system (pump, valves, hoses, motors) at 80, maybe 85% overall efficiency. The cost? More money (of course) and either an automatic control to match pump displacement and engine RPM, or a second control lever for pump displacement (akin to the "pitch" lever on a CPP drive). I'd leave the engine as variable RPM, of course; the idea is to match the combination of RPM and pump displacement to provide the needed power with the engine turning at its most efficient speed for that particular power setting.

It still won't be as efficient as a simple shaft to a big prop, but it'd be a step up (in both performance and price) from the simple auxiliary drives described in the article.

[Marine Nut]

Matt,

I think the gap has closed more than you think between modern gear pumps operating at 3000-3500 PSI vs piston pumps at the same pressures, especially PC ones when you do not have manual control over the displacement. They are big power robbers at anything less than close to full output.

What you said was the "KEY", having control over the displacement and the engine RPM.. Between the two and the way a prop loads the engine, yes, matching is 100% to each load and RPM.. But, with a properly sized FIXED displacement system, having throttle control is very close to what would be ideal in a much simpler system.

I also look at it as "what is the highest practical pressure" you want under the deck, ( maybe 3500 max), as that is about all us laymen can afford.. Above that, efficiency does rise with piston pumps, but with that comes way more than just the cost of the pump.. All fittings, valves and hoses now take a quantum leap as to cost if you want a good safety factor.. And yes, pushing what modern piston pumps can do (5000+ PSI now) efficiency goes up, but again, how much in the practical sense when you look at the big picture?

As to what is right to each application-- For short term use (harbor use or getting out of the harbor when things are not just right, or to just help the sails a tad if you are trying to avoid a tak, then I think what this guy has done is admirable based on all.........


Marine Nut

[CalGuySkip]

I broke all the rules. when my A4 froze due to a freak cold snap, I was confronted with the choice A4 or something else. the Aholes at moyermarine backed out of a deal where i had the high res cad stuff for the foundry. so i
tossed the whole hateful smog making mess in the recycle bin and ....

i started with a kohler 2cyc .62liter 18 horse air cooled. I used a SAE B mount for both the prince 2.003 cuinch pump and a parker 4.0 cu inch motor.
this afforded me the same basic ratio as the hateful A4 v-drive.

I made a heat exchanger from pipe and 4" pvc pipe and a aquatiger water pump. i got the 3 gallon tank and all else from surplus center.com

i made hoses and uses a mech open center spool valve and a brand hydro flow control valve. once i got every thing sorted out i replaced the manual valves with electric ones.

VERY IMPORTANT I USE EXXONMOBILE FR200 ETHYLENE GLYCOL FIRE RESISTANT HYDRO FLUID. OIL BASED IS SO DANGEROUS FOR SO MANY REASONS. it will leak and burn like a N.Carolina chicken fryer. poly glycol works too, and is a good chaser with tanquerey 10.

anyway ... it runs at 2-25 gpm @ 300-500 psi.

i made a microcontroller that controls the throttle and choke using industrial metal gear servos and the electric spool valve. the brand electro flow valve is controled with a mosfet transistor coupled to the microcontroller.

i then used heavyduty pots and buried them in an indian rosewood tiller.

so now i can start stop throttle up, control pressure and direction from the tiller. all so easy and simple. in summer i have a radiator fan to blow the heat out and in the winter the heat feels so nice comeing out of the salon into the cockpit. i have used this for 6 years and never had a problem.

glycol is the perfect hydro fluid and it works at temps that freezes hydro oil. and sooooo safe. trust me this is very important unless you like running for your life.

total cost $2700. the way i look at it i can deep 6 the whole setup 5 times before i even cross the cost of the hateful a4. also the kohler is electric and pull start. it is epa approved and will freeze long after hell does.

from smallengine warehouse i got the 25 amp upgrade and a exhaust set. a bit of welding and the thing is so quiet and i can run all my lowpower tronics like sea clear II runining on a VIA fanless itx pc with a 64 gig SSD a phylon 10'touch screen and the open cpn tide and current software.
i bought a garmin 5 gps and a bushnell sat xm weather / radio, as wel as a thin panasonic blue ray dvd spinner for the little pc. nothing to wear out or break. totally done and complete.

[FAST FRED]

ON our boat we use Hyd for steering , the big fancy wheel simply operates a valve , and 2 solenoids operate from the auto pilot , no cooler at all.

When we decided to add a circuit for the windlass the mfg recommended some cooling.

Our solution (the windlass is used for maybe 10 min a day) was to run the supply and return hose thru the bilge.

There is always an inch or two of water there and so far it works hust fine.

A simple solution!

Be sure to order ALL your hoses with swivel fittings on both ends, or you may end up spinning 30 ft of hose to install it.

Remember you have a GASOLINE boat so pumps , alts and the rest must be gas compliant.
FF

[kbowen]

Originally Posted by marshmat

If you take the time to sort through the catalogues for a properly sized, variable displacement piston pump and a suitable motor .....

Why variable displacement? Couldn't you just have a reversing valve and use the engine rpm to vary speed?

[Submarine Tom]

And what would the maintenance costs look like I wonder.

My experience is high.

-Tom

[whitepointer23]

put an 8 hp fourstroke outboard on the back and keep things simple. much nicer to have the engine on the back and save the room inside for accomodation.

[kbowen]

Originally Posted by whitepointer23

put an 8 hp fourstroke outboard on the back and keep things simple. much nicer to have the engine on the back and save the room inside for accomodation.

Since your signature-block contains something about twin 318 Chryslers, I suspect we might be speaking different languages, but I was thinking about some smaller system with hoses that I could ship inboard and out-of sight, out-of-smell easier than an outboard. Also, the typical 8hp outboard is engineered to drive a 14' aluminum boat at 15-20mph not a 6000# double-ender at 6mph.

[FAST FRED]

Also, the typical 8hp outboard is engineered to drive a 14' aluminum boat at 15-20mph not a 6000# double-ender at 6mph.

"Typical outboard ", yes , however there ARE high thrust outboards with big props and heavy gearing that are made just for this.No problem.

FF

[kbowen]

Originally Posted by FAST FRED

Also, the typical 8hp outboard is engineered to drive a 14' aluminum boat at 15-20mph not a 6000# double-ender at 6mph.

"Typical outboard ", yes , however there ARE high thrust outboards with big props and heavy gearing that are made just for this.No problem.

FF

Can you refer me to some examples of these engines that you like? I would still have the question of how to mount and ship the monster over a very skinny double-ended stern... Or make a motor well, or ????

[whitepointer23]

Originally Posted by kbowen

Since your signature-block contains something about twin 318 Chryslers, I suspect we might be speaking different languages, but I was thinking about some smaller system with hoses that I could ship inboard and out-of sight, out-of-smell easier than an outboard. Also, the typical 8hp outboard is engineered to drive a 14' aluminum boat at 15-20mph not a 6000# double-ender at 6mph.

sorry to offend you, i was just stating an option thats all. as fred says, there are high thrust outboards for houseboats and yacht auxillarys, you would have to live under a big rock not to know that. i can see your point in that an outboard might not look good on your type of boat but it is an easy fit with a bracket or build a well, i personally don't like wells but they do have some advantages. even a standard outboard with the right prop will push your boat fine . i wouldn't think a modern outboard would be as smelly as a motor mounted in the boat.

[whitepointer23]

Originally Posted by kbowen

Since your signature-block contains something about twin 318 Chryslers, I suspect we might be speaking different languages, but I was thinking about some smaller system with hoses that I could ship inboard and out-of sight, out-of-smell easier than an outboard. Also, the typical 8hp outboard is engineered to drive a 14' aluminum boat at 15-20mph not a 6000# double-ender at 6mph.

sorry, thought i was talking to the original post not a blow in. and i thought cat boats had straight transoms.

[marshmat]

Originally Posted by kbowen

Why variable displacement? Couldn't you just have a reversing valve and use the engine rpm to vary speed?

The point of a variable displacement pump is one of two things:
- If you have a constant speed engine, variable pumps give variable speed;
- If you have a variable speed engine, variable pumps let you match the engine speed to the load, in the same manner as a car's multi-speed or CVT transmission, or a workboat's controllable-pitch prop. This gives a more efficient system and greatly extends engine life.
If you're just trying to get in and out of harbour, a simple fixed pump and reversing valve is simpler and cheaper. Variable stuff is called for in heavy- or continuous-duty applications.