hydraulic drive

[bobbyv]

Thanks to all who took the time to offer advice/thoughts etc.
I will take it all into consideration whilst making a decision.
There are definately some real advantages,the main disadvantages seem to be extra cost and power loss.
It would make an interesting project,wouldn`t it?
Bob V

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[Transcur]

We fitted twin hydraulic drives 18 months ago running from a ford 1.6Diesel. Works well with 2 folding props, very easy to control. We got the bits from ARS Anglian Diesels LTD . E-mail at ars@btconect.com. The system was quite expensive but very versatile. Using bent axis piston pumps is very efficient, about 95%. Gear or vane pumps are less efficient taking up to 30 % of the power. The oil resevoir is small, only 15 ltrs .and can be fitted anywhere. We used VOAC pumps/motors part of the Perker Hannifin Group(20,000 hours service interval!!!). Others are cheaper on the net.

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[snowleopard]

seem to have a lot of threads running on this topic! on thing i forgot to mention is that when the engine is stopped you can't stop the prop turning by putting it in gear, you have to have a shaft brake which can be a pain to operate and dangerous if you forget to disengage it. only boat i've sailed on with that system required lifting the floor and inserting an arm full length into the bilge!

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[Transcur]

If you use piston pumps/motors then stopping the shaft from spinning is NOT a problem. Just put in gear/select drive, astern is best.

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[bobbyv]

Thanks "Transcur",
I seem to be heading in the direction you have suggested.
There has been a lot of negative reaction to this form of transmission,
but 95% efficiency, 20,000 hours service intervals + the "controlability" suggest it might just be worth it!
The bent axis piston pump you mention, I believe may also be called swash plate or something similar.This is what gives the extra control,engines revs can be constant,the pump determining propshaft speed.
Appreciate your comments,
Bob V

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